D E S C R I P T I O N
Imaging device
Technical Field
The present invention relates to an imaging
device, which is excellent in color balance and color
reproducibility.
Background Art
Conventionally, an image sensor (imager) used for
digital and video cameras includes an imaging device.
The imaging device is provided with a light receiving
element, such as a CMOS or CCD, and a color filter,
which are paired, and thereby, images a color image.
The light receiving element outputs an electrical
signal in accordance with the intensity of incident
light. The light receiving element senses the
brightness only of the incident light, and does not
determine the color thereof. And so, a side
(hereinafter, referred to as incident light side) where
light is incident on each light receiving device is
provided with a color filter to extract light having a
specified color component from the incident light. By
doing so, the extracted color component light is
observed via the light receiving element. Extracting
light having a specified color component from the
incident light is called as "color separation".
Specifically, the incident light side of the light
receiving element is provided with color filters for
light of three primary colors, that is, red (R), green
(G) and blue (B). The incident light from an observed
object is separated in colors via the color filters
before reaching the light receiving element, and
thereby, a specified light is extracted. The extracted
light reaches the light receiving element facing each
color filter, and then, is photo-electrically converted
into an electrical signal. By doing so, an output
value (usually, voltage value) of the three primary
colors of the incident light is obtained. Then, the
obtained output value is added, and thereby, the
observed object is reproduced as a color image.
In general, the color filter is patterned into a
necessary pattern in the following manner.
Specifically, the color filter is developed using a
developer after pattern exposure to a photosensitive
resin via "photolithography process". The exposure
system using the photolithography process includes a
stepper, aligner, mirror projection aligner, etc. If
high pixel and scale-down are required, the stepper is
used.
Recently, for imaging devices, a demand as arisen
for more pixels; as a result, the scale-down of pixel
advances. Specifically, the pixel pitch becomes less
than 3 um, and as of today, about 2 /um. If a fine
pixel having the pixel pitch of about 2 um is given,
an area per pixel becomes small. For this reason, the
quantity of light incident on the light receiving
element reduces. As a result, the sensitivity of the
imaging device is reduced, and therefore, the image
quality is reduced (a dark image is produced).
As described above, in the conventional imaging
device, the incident light side of the light receiving
element is provided with blue, green and red, that is,
three primary color filters to separate the color of
the light from the observed object. FIG. 1 shows one
example of spectral transmittance of blue, green and
red, that is, three primary color filters. In FIG. I,
the horizontal axis shows the wavelength while the
vertical axis shows the transmittance. As seen from
FIG. 1, the top portion of the transmittance of blue
and green colors is a value before and after 80%. In
other words, blue and green color filters each have low
transmittance; for this reason, the quantity of light
reaching the light receiving element is reduced. As a
result, the image quality is reduced (a dark image is
produced).
Light receiving elements such as a CMOS and CCD
have a wide sensitivity range from about 400 nm to
1000 nm. In particular, as shown in FIG. 2, the SPD
(Silicon Photo Diode) sensitivity of the light
receiving element has a high value in the wavelength
range of about 700 nm. In other words, the light
receiving element has a high sensitivity in a red
wavelength range (700 nm). However, the sensitivity is
reduced in a short wavelength range. The sensitivity
is about half of red in a blue wavelength range (400 nm
to 500 nm).
As seen from the foregoing description, the
sensitivity of the light receiving element is low in
the blue range in the imaging device having blue, green
and red primary color filters. In addition, the
transmittance of the blue color filter is lower than
that of red and green color filters.
For this reason, the conventional imaging device
has the following problem. Specifically, blue
reproducibility and color rendering is lower than red
and green; as a result, color balance is not strictly
reproducible.
In order overcome the foregoing problem, the
following technique has been proposed (e.g., Jpn. Pat.
Appln. KOKAI Publication No. 2002-51350) . According to
the technique, a complementary color filter comprising
cyan (C), magenta (M) and yellow (Y) is used to prevent
reduction of the quantity of light arriving at the
light receiving element.
According to the technique, the yellow (Y) color
filter is used, and thereby, composite light of red (R)
and green (G) is extracted. The magenta (M) color
filter is used, and thereby, composite light of red (R)
and blue (B) is extracted. The cyan (C) color filter
is used, and thereby, composite light of green (G) and
blue (B) is extracted. In other words, the
complementary color filter transmits light of two
colors; therefore, this serves to increase the
transrnittance of light. By doing so, it is possible to
prevent the quantity of light incident on the imaging
device from being reduced.
Disclosure of Invention
However, troublesome operations are required to
extract the three primary colors of light; blue, green
and red from the light transmitted through cyan,
magenta and yellow complementary color filters.
For example, the following calculations must be
made based on an observed data value of each filter.
Blue = (cyan + magenta - yellow)/2
Green = (cyan + yellow - magenta)/2
Red = (magenta + yellow - cyan)/2
FIG. 3 is a graph showing spectral characteristics
of general C, M and Y complementary color filters. As
described above, the complementary color filters obtain
an observed data value equivalent to the three primary
colors using the operation. As seen from FIG. 3, the
complementary color filters each transmit light
belonging to a light wavelength range to be inherently
shielded. As is evident from ul, u2, and u3 shown in
FIG. 3, the transmittance of each complementary color
filter is different for every color in the wavelength
range to be inherently shielded. The foregoing
difference is the factor of a noise component included
in the operation resultant value.
For this reason, the imaging device using
complementary color filters has a high sensitivity, but
noise is increased. As a result, there is a problem
that color reproducibility (color separation) is
reduced as compared with three primary color filters.
The present invention has been made in view of the
foregoing circumstances. An object of the present
invention is to provide an imaging device, which is
excellent in color balance and color reproducibility.
In order to solve the problem, the present
invention provides an imaging device comprising:
a filter used for extracting a specified color
component of an incident light; and
a light receiving element observing the incident
light via the filter,
the filter including:
a transparent filter
a yellow filter used for extracting a yellow
component; and
a red filter used for extracting a red component.
Brief Description of Drawings
FIG. 1 is a graph showing a spectral transmittance
of a conventional imaging device;
FIG. 2 is a graph showing the relationship between
wavelength and transmittance in human visual
sensitivity, sensitivity (SPD sensitivity) of light
receiving element and ideal infrared cut filter;
FIG. 3 is a graph showing spectral characteristics
of general C, M and Y complementary color filters;
FIG. 4 is a top plan view showing a state that
filters are arrayed in an imaging device 1 according to
a first embodiment of the present invention;
FIG. 5 is a cross-sectional view showing the
imaging device according to the first embodiment;
FIG. 6 is a graph showing each spectral
transmittance of transparent filter 2W, yellow filter
2Y and red filter 2R according to the first embodiment;
FIG. 7 is a graph showing each spectral
transmittance of virtual blue, green and red filters
obtained by an operation of the imaging device 1
according to the first embodiment;
FIG. 8 is a graph showing spectral characteristics
of a conventional imaging device;
FIG. 9 is a cross-sectional view showing an
imaging device 9 according to a second embodiment of
the present invention;
FIG. 10 is a cross-sectional view showing an
imaging device 11 according to a third embodiment of
the present invention;
FIG. 11 is a cross-sectional view to explain a
process of manufacturing the imaging device 11
according to the third embodiment;
FIG. 12 is a cross-sectional view to explain the
process of manufacturing the imaging device 11
according to the third embodiment;
FIG. 13 is a cross-sectional view to explain the
process of manufacturing the imaging device 11
according to the third embodiment;
FIG. 14 is a cross-sectional view to explain the
process of manufacturing the imaging device 11
according to the third embodiment;
FIG. 15 is a cross-sectional view to explain the
process of manufacturing the imaging device 11
according to the third embodiment;
FIG. 16 is a top plan view showing an arrangement
of a shield film o an imaging device 17 according to a
fourth embodiment of the present invention;
FIG. 17 is a front view showing a state that
filters are arrayed in an imaging device 31 according
to a fifth embodiment of the present invention;
FIG. 18 is a cross-sectional view showing the
imaging device 31 according to the fifth embodiment;
FIG. 19 is a cross-sectional view showing another
imaging device 31 according to the fifth embodiment;
FIG. 20 is a graph showing spectral transmittance
relevant to compensating filter 2Blk, transparent
filter 2W, yellow filter 2Y and red filter 2R according
to the fifth embodiment;
FIG. 21 is a graph showing each spectral
transmittance of virtual blue, green and red filters
obtained by an operation of the imaging device 31
according to the fifth embodiment;
FIG. 22 is a graph showing spectral
characteristics of the compensating filter according to
the fifth embodiment;
FIG. 23 is a graph showing spectral
characteristics of a general absorption type infrared
cut filter;
FIG. 24 is a cross-sectional view showing the
imaging device 39 according to a sixth embodiment of
the present invention;
FIG. 25 is a cross-sectional view showing the
imaging device 41 according to a seventh embodiment of
the present invention;
FIG. 26 is a font view showing a first arrangement
of a shield film 19 of an imaging device 47 according
to an eighth embodiment of the present invention;
FIG. 27 is a cross-sectional view showing the
imaging device 47 according to the eighth embodiment;
FIG. 28 is a cross-sectional view a second
arrangement of a shield film 19 of an imaging device 44
according to the eighth embodiment;
FIG. 29 is a graph showing spectral transmittance
characteristics of a compensating filter according to a
ninth embodiment of the present invention;
FIG. 30 is a graph showing spectral transmittance
characteristics of a compensating filter according to a
ninth embodiment;
FIG. 31 is a graph showing spectral
characteristics of a compensating filter according to a
tenth embodiment of the present invention;
FIG. 32 is a schematic view showing the
configuration of an imaging device according to an llth
embodiment of the present invention;
FIG. 33 is a view to explain the concept of an
arrayed state of a color filter of an imaging device
110 according to the llth embodiment when viewing from
the incident light side;
FIG. 34A is a cross-sectional view showing the
imaging device 110 according to the llth embodiment;
FIG. 34B is a cross-sectional view showing the
imaging device 110 according to the llth embodiment;
FIG. 35 is a flowchart to explain the operation of
the imaging device 110 according to the llth
embodiment;
FIG. 36 is a graph showing the human eye
stimulation value of light, which changes according to
wavelength;
FIG. 37A is a view to explain a method of
manufacturing an imaging device 110 according to a 12th
embodiment of the present invention;
FIG. 37B is a view to explain the method of
manufacturing the imaging device 110;
FIG. 37C is a view to explain the method of
manufacturing the imaging device 110;
FIG. 37D is a view to explain the method of
manufacturing the imaging device 110;
FIG. 38A is a view to explain the method of
manufacturing the imaging device 110;
FIG. 38B is a view to explain the method of
manufacturing the imaging device 110;
FIG. 38C is a view to explain the method of
manufacturing the imaging device 110;
FIG. 38D is a view to explain the method of
manufacturing the imaging device 110;
FIG. 38E is a view to explain the method of
manufacturing the imaging device 110;
FIG. 39 is a view showing another imaging device
according to the 12th embodiment;
FIG. 40 is a view showing another imaging device
according to the 12th embodiment;
FIG. 41 is a schematic view showing the
configuration of an imaging device according to a 13th
embodiment of the present invention;
FIG. 42 is a view to explain the concept of an
arrayed state of a color filter 114 of an imaging
device HOT according to the 13th embodiment when
viewing from the incident light side;
FIG. 43A is a cross-sectional view showing the
imaging device HOT according to the 13th embodiment;
FIG. 43B is a cross-sectional view showing the
imaging device HOT according to the 13th embodiment;
FIG. 44 is a cross-sectional view showing another
imaging device HOT according to the 13th embodiment;
FIG. 45 is a graph showing the relationship
between wavelength and transmittance in human visual
sensitivity, sensitivity (SPD sensitivity) of light
receiving element and ideal infrared cut filter;
FIG. 46 is a graph showing the relationship
between light wavelength and transmittance in
reflection and absorption type infrared cut filters;
FIG. 47 is a graph showing spectral
characteristics of a planarization layer according to
the first example of the present invention;
FIG. 48 is a graph showing spectral
characteristics of transparent filter 114W, yellow
filter 114Y, red filter 114R and compensating filter
11431k according to the first example;
FIG. 49 is a graph showing each spectral
characteristic of virtual blue, green and red filters
obtained by an operation of the imaging device
according to the first example;
FIG. 50 is a graph showing spectral
characteristics of a transparent resin according to the
second example of the present invention;
FIG. 51 is a graph showing spectral
characteristics of transparent filter 114W, yellow
filter 114Y, red filter 114R and compensating filter
114Bllc according to the second example;
FIG. 52 is a graph showing each spectral
characteristic of virtual blue, green and red filters
obtained by an operation of the imaging device
according to the second example;
FIG. 53 is a graph showing spectral
characteristics of filters Fl to F7 according to a 14th
embodiment of the present invention;
FIG. 54 is a view to explain the concept of
virtual color filter according to the 14th embodiment;
FIG. 55 is a front view showing an imaging device
according to a 15th embodiment of the present
invention; and
FIG. 56 is a graph showing spectral
characteristics of filters Fl to F7 according to the
15th embodiment.
Best Mode for Carrying Out the Invention
Various embodiments of the present invention will
be hereinafter described with reference to the
accompanying drawings. In the following description,
the same reference numerals are used to designate the
identical components, and the details thereof are
omitted.

An imaging device according to the first
embodiment will now be described. The imaging device
is provided with a filter layer at a light incident
side of a light receiving element, such as a CMOS or
CCD, to observe a color component of an observed
object.
FIG. 4 is a top plan view showing a state that
filters are arrayed in the imaging device according to
the first embodiment. FIG. 4 shows a state that
filters are arrayed when viewing from the light
incident side.
FIG. 5 is a cross-sectional view showing the
imaging device according to the first embodiment.
FIG. 5 shows a cross section taken along a line I-I' of
FIG. 4. In FIG. 5, although there is shown the case
where the light receiving element is a CMOS, a CCD may
be used as the light receiving element. In the
following description, the same configuration is given
to other cross-sectional views of the imaging device.
An imaging device 1 includes filter layer 2, light
receiving element 3 and an operator 4. The filter
layer 2 is used for extracting a specified color
component of incident light. The light receiving
element 3 observes the incident light via the filter
layer 2.
The filter layer 2 includes transparent filter 2W,
yellow filter 2Y and red filter 2R. Two pixels are
given as the yellow filter 2Y, and one pixel is given
as each of transparent and red filters 2W and 2R.
Thus, one unit of color separation is formed of the
total of four pixels. In other words, the number of
the pixels of the yellow filter 2Y is equal to the
total number of pixels of transparent and red filters
2W and 2R. By ding so, operations such as
{(white) - (yellow)} and {(yellow) - (red)} described
later are carried out for every unit.
The foregoing transparent filter 2W, yellow filter
2Y and red filter 2R are arrayed adjacently like a mesh
to form a plane.
Preferably, the transparent filter 2W transmits
light without absorbing mainly a long wavelength light
of 400 ran or more. In other words, the transparent
filter 2W transmits light synthesizing blue, green and
red components. For example, a filter satisfying the
following conditions is preferably given as the
transparent filter 2W. According to the conditions, a
transparent glass having a refraction n of about 1.5 is
used as a reference, and the transmittance of the light
having a wavelength of 400 nm or more is 95% or more.
The transparent filter 2W is formed of phenol,
polystyrene or acrylic resin. In this case, the
transparent filter 2W is formed of polystyrene,
preferably, acrylic resin. This is preferable in view
of heat resistance.
The yellow filter 2Y is a filter used for
extracting a yellow component of incident light (light
synthesizing red and green components). Moreover, the
yellow filter 2Y is a complementary color filter. In
general, a complementary color filter has a higher
transmittance than a blue, green, red, three primary
color filter.
The red filter 2R is a red color filter used for
extracting a red component of the incident light. In
general, a red color filter has a higher transmittance
than other color filters of three primary colors, that
is, blue and green color filters.
The light receiving element 3 is arranged at the
side opposite to the light incident side of the filter
layer 2. The light receiving element 3 includes
incident light receiving element 3W, yellow light
receiving element 3Y and red light receiving element
3R. Moreover, the light receiving element 3 has a
function of receiving light via the filter layer 2 and
converting the received light into an electrical signal
to calculate an observed data value (intensity value).
The one-to-one combination of the light receiving
element and the filter is equivalent to a pixel. The
light receiving element 3 is formed at the incident
light side of a semiconductor substrate 5.
The incident light receiving element 3W is formed
corresponding to transparent filter 2W to observe an
incident light via the transparent filter 2W.
The yellow light receiving element 3Y is formed
corresponding to the yellow filter 2Y to observe the
incident light via the yellow filter 2.
The red light receiving element 3R is formed
corresponding to the red filter 2R to observe the
incident light via the yellow filter 2R.
The operator 4 includes blue, green and red
operating units 4B, 4G and 4R. The operator 4 further
has a function of calculating the following data.
Based on observed data values Dw and Dy taken by the
foregoing incident light, yellow and red receiving
elements 3W, 3Y and 3R, blue and green observed data
values Db and Dg are determined.
The blue operating unit 4B subtracts the observed
data value Dy observed by the yellow light receiving
element 3Y from the observed data value Dw observed by
the incident light receiving element 3W. Thus, the
operating unit 4B determines the blue observed data Db
(= Dw - Dy) .
The green operating unit 4G subtracts the observed
data value Dr observed by the red light receiving
element 3R from the observed data value Dy observed by
the yellow light receiving element 3Y. Thus, the green
operating unit 4G determines the green observed data Dg
(= Dy - Dr) .
Namely, if white (W), Yellow (Y) and red (R) are
given as each of colors corresponding to transparent,
yellow and red filters 2W, 2Y and 2R, the following
equations (1) and (2) are established.
Blue (B) = white (W) - yellow (Y) ... (1)
Green (G) = yellow (Y) - red (R) ... (2)
FIG. 5 shows a cross section ranging yellow and
transparent filters 2Y and 2W and yellow and
transparent light receiving elements 3Y and 3W. Other
filters and light receiving elements each have the same
cross-sectional structure as described above.
The light receiving side of the semiconductor
substrate 5 is formed with the light receiving element
3.
A planarization layer 6 is stacked on the surface
of the light incident side of the semiconductor
substrate formed with the light receiving element 3. A
resin containing one or more of acryl, epoxy,
polyimide, urethane, melamine, polyester, urea and
styrene is usable as the material for the planarization
layer 6.
The light incident side of the planarization layer
6 is formed with the filter layer 2 corresponding to
the light receiving element 3. Moreover, a resin layer
(transparent planarization layer) 7 is stacked on the
light incident side of the filter layer 2.
The light incident side of the resin layer 7 is
provided with a micro lens 8 corresponding to the light
receiving element 3.
A micro lens 8 is arranged above each of
transparent, yellow and red filters 2W, 2Y and 2R to
make a pair with each of these filters. Moreover, the
micro lens 8 is formed of acrylic resin to improve
convergence to incident light, yellow and red receiving
elements 3W, 3Y and 3R.
According to the first embodiment, each filter
layer has a film thickness of 1.4 /urn, and a pixel
pitch (of transparent, yellow and red filters 2W, 2Y,
2R) is 2.6 Aim.
An ultraviolet absorbing agent is added to the
foregoing planarization layer 6. Specifically, the
planarization layer 6 is formed of a thermosetting
acrylic resin added with an ultraviolet absorbing
agent, and formed to have a film thickness of 0.3 /zm.
Adding the ultraviolet absorbing agent to the
planarization layer 6 is done for the following reason.
Namely, when the filter layer 2 is formed using the
photolithography process, halation of a pattern
exposure light from the front-end, that is, the
semiconductor substrate 5 is prevented. By doing so, a
filter having a good shape is obtained. Here, pattern
exposure and development are made with respect to a
photosensitive resin layer using the photolithography
process so that a photosensitive resin remains at a
predetermined portion.
According to the first embodiment, the
planarization layer 6 is formed. In this case, no
planarization layer 6 may be formed for the purpose of
making the imaging device thinner.
According to the first embodiment, the transparent
filter 2W is formed of an alkali-soluble photosensitive
acrylic resin (refraction n = 1.55).
Yellow filter 2Y and red filter 2R are formed of a
colored photosensitive resin described below. The
colored photosensitive resin is formed in a manner of
adding and dispersing a predetermined organic pigment
to the transparent resin (photosensitive acrylic resin)
used for forming the transparent filter 2W. For
example, C.I. Pigment Yellow 150 may be used as an
organic pigment for forming the yellow filter 2Y. In
addition, a pigment mixing C.I. Pigment Yellow 150 with
C.I. Pigment Yellow 139 is usable. Moreover, a pigment
mixing C.I. Pigment Red 177, C.I. Pigment Red 48:1 and
C.I. Pigment Yellow 139 may be used as an organic
pigment for forming the red filter 2R. Incidentally,
the transparent filter 2W may be formed of a
transparent resin to which no colored pigment is added.
FIG. 6 is a graph showing spectral transmittance
of transparent, yellow and red filters 2W, 2Y and 2R.
The imaging device 1 performs an operation
(subtraction) based on observed data values Dw, Dy and
Dr observed by each light receiving element. By doing
so, for the three primary colors, that is, blue, green
and red, observed data values Db, Dg and Dr are
obtained. In other words, the imaging device 1
performs the operation described above, and thereby,
seemingly (virtually) includes blue and green filters.
FIG. 7 is a graph showing spectral transmittance
of virtual blue, green and red filters obtained by the
operation of the imaging device 1. When comparing the
graph of FIG. 7 with the spectral transmittance of the
conventional blue and green color filters, it can be
seen that the spectral transmittance of virtual blue
and green filters of the imaging device 1 is higher
than that of the conventional blue and green color
filters. In particular, the transmittance of the
virtual blue filter is higher than the conventional
blue color filter. Therefore, the imaging device 1
according to the first embodiment has high blue
sensitivity; as a result, color balance is excellent.
A comparison between the imaging device 1
according to the first embodiment and the conventional
imaging device will be hereinafter described.
First, a "virtual color filter" will be described
below.
FIG. 8 is a graph showing spectral characteristics
of the conventional imaging device.
The spectral characteristics of the conventional
imaging device are equivalent to the product value
obtained in the following manner. The product value is
obtained from multiplying the sensitivity of light
receiving element (graph (A) of FIG. 8) by the
transmittance of filters arranged on the light incident
side of the light receiving element (graph (B) of
FIG. 8). The result is expressed as shown in a graph
(C) of FIG. 8.
As shown in the graph (B) of FIG. 8, the blue
color filter of the conventional imaging device has a
transmittance lower than the red and green color
filters. As seen from the graph (A) of FIG. 8, the
sensitivity of the light receiving element in the blue
wavelength range is lower than that in the red and
green wavelength ranges. For this reason, when the
sensitivity ratio of the conventional imaging device is
calculated, the ratio of (blue/green) becomes smaller
than that of (red/green). This is a factor which
reduces color reproducibility.
On the contrary, the imaging device 1 according to
the first embodiment has the following features.
Specifically, transparent, yellow and red filters 2W,
2Y and 2R are provided in place of three primary
colors, that is, red, green and blue color filters.
Therefore, the spectral characteristics of the imaging
device I according to the first embodiment are
equivalent to a product value obtained in the following
manner. The product value is obtained from multiplying
the sensitivity of light receiving element by the
transmittance of transparent, yellow and red filters
2W, 2Y and 2R arranged on the light incident side of
the light receiving element. The transmittance of
transparent, yellow and red filters 2W, 2Y and 2R is
higher than that of the blue and green color filters.
Therefore, incident, yellow and red light receiving
elements 3W, 3Y and 3R observe an incident light via
transparent, yellow and red filters 2W, 2Y and 2R. In
this case, observed data values Db and Dg calculated
based on observed data values Dw, Dy and Dr are the
observation result obtained from high transmittance.
In particular, according to the blue observed data
value Db, the sensitivity ratio of (blue/green) is made
high; therefore, color reproducibility is improved.
According to the first embodiment, blue and green
observed data values Db and Dg are calculated using
one-time subtraction only. Therefore, this serves to
simplify the operation as compared with the imaging
device using the conventional complementary color
filter. As a result, vivid colors close to primary
colors are reproducible.
The following is an explanation about "noise
resulting from dark current".
As seen from the graph (C) of FIG. 8, the light
receiving element generates a small current even if no
light is incident thereon. Even though light is not
incident on the element, the current flowing from the
light receiving element is called "dark current", which
is a factor generating noise. Conventional blue, green
and red, that is, three primary color filers transmit
light having a predetermined wavelength range on
spectral characteristics, and there exists a wavelength
range shielding light.
However, the light receiving element generates a
dark current in the wavelength range of shielding
light. For this reason, the observed result of the
conventional imaging device includes the noise
resulting from the dark current in addition to the
observed result of light in the wavelength range of
transmitted light. Thus, there is a possibility that
color reproducibility is reduced resulting from the
noise.
On the contrary, the imaging device 1 according to
the first embodiment performs the following operations,
that is, subtractions described above. Specifically,
the observed data value Dy of the yellow light
receiving element 3Y is subtracted from the observed
data value Dw of the incident light receiving element
3W. Moreover, the observed data value Dr of the red
light receiving element 3R is subtracted from the
observed data value Dy of the yellow light receiving
element 3R. By doing so, a dark current value is
offset. Thus, the noise is removed from the observed
result; therefore, color reproducibility is improved.
The following is an explanation about "spectral
peaks and troughs".
The spectral transmittance of the conventional
blue, green and red color filters is seen from the
graph (B) of FIG. 8. The transmittances of the ridge
portions of the spectral curves of blue and red color
filters are low, that is, several percent (%). On the
other hand, the transmittance of the ridge portion of
the spectral curve of the green color filter is high,
that is, about 10%. As described above, the
transmittance of the ridge portion of the curve is
high, and this means that spectral peaks and troughs
are large.
The conventional imaging device has the following
features. The ridge portion of the spectral curve of
the green color filter exists in blue and red
wavelength range. The spectral peaks and troughs of
the ridge portion of green are large. For this reason,
the green observed result mixes blue and red color; as
a result, there is problem that green color
reproducibility is reduced.
On the contrary, the imaging device according to
the first embodiment performs the following operation
to calculate the green observed data value Dg.
Specifically, the observed data value Dr of the red
light receiving element 3R is subtracted from the
observed data value Dy o the yellow light receiving
element 3Y. Thus, the spectral peaks and troughs are
made small; therefore, this serves to improve color
reproducibility.
The following is an explanation about the
"ultraviolet and infrared absorbing agent".
The light receiving element, such as a CMOS or
CCD, has a slight sensitivity with respect to an
ultraviolet range that humans cannot sense. For this
reason, the following features are desired.
Specifically, the filter layer 2 of the first
embodiment absorbs light of 400 nm or less so as not to
transmit it. On the other hand, the filter layer 2
transmits light of 400 nm or more without absorbing it.
In order to achieve the foregoing features, an
ultraviolet absorbing agent, an initiator used for
resin thermosetting and hardener are added to the
transparent filter 2W. By doing so, the transparent
filter 2W has an ultraviolet absorbing function. For
example, benzotriazole, benzophenone compound,
salicylic acid and coumarin compounds are usable as the
ultraviolet absorbing agent. Moreover, a light
stabilizer such as hinderdomine and quencher may be
added to the ultraviolet absorbing agent. A functional
group having the ultraviolet absorbing function is
pendent to a resin used for forming the transparent
filter 2W, that is, a polymer, monomer or hardener. A
group incorporated into polymer may be polymerized.
For example, quinone and anthracene may be introduced
into a polymer, or a monomer having an ultraviolet
absorbing group may be added. The foregoing pendent
means that a reactive absorber is incorporated into a
resin molecular chain.
More preferably, an infrared absorptive compound
and infrared absorbing agent are added to a resin
forming the transparent filter 2W. For example,
according to the foregoing pendent, they are added to
the resin forming the transparent filter 2W.
Moreover, the filter layer 2 of the first
embodiment has the following features. Two pixels are
used as the yellow filter 2Y, and one pixel is used as
each of transparent and red filters 2W and 2R. Thus,
one unit of color separation is formed using
four pixels in total. Therefore, when the operator 4
obtains blue and green observed values, the yellow data
value does not need to be repeatedly used. In other
words, the operator 4 independently executes the
operations of {(white) - (yellow)} and
{(yellow) - (red)} in one unit. This serves to realize
a high-speed operation.
As described above, the imaging device I according
to the first embodiment performs one-time subtraction.
By doing so, the imaging device 1 includes virtual
high-transmittance blue and green filters. Thus, blue
observation accuracy is improved as compared with the
conventional imaging device.

The second embodiment relates to a modification
example of the imaging device 1 according to the first
embodiment. An imaging device 9 according to the
second embodiment differs from the imaging device 1
according to the first embodiment in the following
point. That is, the transparent filter 2W and the
resin layer 7 are integrated. The same reference
numerals are used to designate portions the same as
already described, and a repeated explanation is
omitted. In the following embodiments, overlapping
explanations are omitted, likewise.
FIG. 9 is a cross-sectional view showing the
imaging device according to the second embodiment.
FIG. 9 shows a cross section taken along a line I-I' of
FIG. 4. A transparent filter 10W is equivalent to the
transparent filter 2W and the resin layer 7 described
in the first embodiment.
The imaging device 9 of the second embodiment has
a structure in which part of the transparent filter 10W
is arranged at the transparent filter 2W of the first
embodiment.
Other portions of the transparent filter 10W cover
the surface on the light incident side of yellow and
red filters 2Y and 2R. In other words, the transparent
filter 10W has a structure in which the transparent
filter 2W and the resin layer 7 of the first embodiment
are integrated. In addition, the transparent filter
10W also performs a function as a transparent
planarization layer.
Like the first embodiment, the imaging device 9
performs an operation (subtraction) based on observed
data values Dw, Dy and Dr obtained by each light
receiving element 3 to obtain blue and green data
values Db and Dg. In other words, the imaging device 9
performs an operation (subtraction) based on observed
data values obtained by each light receiving element 3.
By doing so, the imaging device 9 includes virtual
blue, green and red filters.
The spectral transmittance of virtual blue, green
and red filters obtained by the operation of the
imaging device 9 is the same as that in FIG. 7 in a
wavelength range from 400 nm to 800 nm.
According to the second embodiment, yellow and red
filters 2Y and 2R are formed, and thereafter, the
transparent filter 10W is formed to cover these
filters. In this case, the transparent filter 10W is
formed integrally with the transparent planarization
layer.
In other words, the process of forming the
transparent filter 10W and the transparent
planarization layer is simultaneously carried out.
Therefore, there is no need of independently providing
a process of forming a pattern of the transparent
filter. This contributes to simplifying the process of
manufacturing the imaging device 9.
Specifically, the transparent planarization layer,
that is, part of the transparent filter 10W is arranged
at the position formed with the transparent filter 2W.
Thus, the transparent filter 10W performs a function as
the transparent planarization layer. Therefore, this
serves to omit a process of independently forming the
transparent filter using the photolithography process.
In other words, three color filters are formed via the
process of forming two color (yellow, red) filters.
Therefore, a process of forming one color filter is
reduced.

The third embodiment relates to a modification
example of the imaging device according to the first
and second embodiments.
FIG. 10 is a cross-sectional view showing an
imaging device according to the third embodiment.
An imaging device 11 of the third embodiment
includes a transparent filter 12W. The transparent
filter 12W has a structure in which the micro lens 8
and the transparent filter 10W of the imaging device 9
of the second embodiment are integrated. In other
words, the transparent filter 12W has a function of
enhancing convergence to incident, yellow and red light
receiving elements 3W, 3Y and 3R.
The process of manufacturing the imaging device 11
will be hereinafter described with reference to FIG. 11
to FIG. 15.
At first, a semiconductor substrate 5 is formed
with incident, yellow and red light receiving elements
3W, 3Y and 3R. A planarization layer 6 formed of a
transparent resin is formed on the semiconductor
substrate 5 (FIG. 11). Specifically, a coating liquid
using an acrylic resin as a main component is applied
on the semiconductor substrate 5 provided twodimensionally
with light receiving elements using spin
coating at a rotational speed of 2000 rpm. Then, a
heat treatment of 200°C is carried out to harden the
film, and thereby, the planarization layer 6 having a
film thickness of 0.2 um is formed. The used acrylic
resin coating liquid is doped with a coumarin
ultraviolet absorbing agent having a solid ratio of
about 3%.
In order to form color filters consisting of a
colored photosensitive resin, an ultraviolet ray is
used to expose the pattern on the colored
photosensitive resin. In the pattern exposure,
halation occurs. In order to prevent halation, it is
desirable to add an ultraviolet absorbing agent to the
planarization layer 6. In this case, no planarization
layer 6 may be formed, to make the imaging device 11
thinner.
Thereafter, yellow and red filters 2Y and 2R are
formed using the photolithography process (FIG. 12).
Specifically, yellow and red filters 2Y and 2R
having a thickness of about 1 um are formed using two
color resists (yellow, red) mixed in with the color
material in an exposable and developable photosensitive
acrylic resin. An organic pigment C.I. Pigment Yellow
150 is usable as the color material of the yellow
filter 2Y. The color material (organic pigment) of the
yellow filter 2Y has a solid ratio of about 33%. A
pigment mixing C.I. Pigment Red 177, C.I. Pigment Red
48:1 and C.I. Pigment Yellow 139 is usable as the color
material of the red filter 2R. The color material
(organic pigment) of the red filter 2R has a solid
ratio of about 48%.
A transparent resin layer is coated on the
semiconductor substrate 5 using spin coating to cover
yellow and red filters 2Y and 2R. Then, the
transparent resin layer is thermally hardened at a
temperature of 180°C for three minutes to form a
planarization layer 12 including a transparent filter
12W. The planarization layer 12 uses substantially the
same material as the planarization layer 6. The
planarization layer 12 is formed by coating a
thermosetting acrylic resin having a high solid ratio
for making the film thick. Incidentally, the acrylic
resin contains a coumarin ultraviolet absorbing agent
of 2%. The planarization layer 12 has a film thickness
of about 2 μm.
Thereafter, an exposable and developable
photosensitive phenol resin layer 13 is formed on the
planarization layer 12 (FIG. 13). The photosensitive
phenol resin layer 13 is a resin having "thermal
reflow". Thermal reflow refers to the property in
which the resin is melted by heat treatment, and then,
rounded like a lens by surface tension.
Then, the photosensitive phenol resin layer 13 is
formed with a photosensitive phenol resin having a
predetermined pattern by carrying out pattern exposure
development and film hardening.
A heat treatment of 2000C is carried out to
fluidize the photosensitive phenol resin having a
predetermined pattern. By doing so, a semi-spherical
lens material (matrix) 13a having a thickness of about
0.6 jum is formed (FIG. 14).
Anisotropic dry etching is carried out using the
lens material 13a as a mask. By doing so, the shape of
the lens material 13a is transferred to the
planarization layer 12 to form a micro lens (FIG. 15).
In other words, the lens material 13a is removed by the
foregoing etching; however, the lens material 13a is
used as the mask for the transparent filter 12W. Thus,
the semi-spherical shape of the lens material 13a is
transferred to the transparent filter 12W. In this
manner, the micro lens 8 and the transparent filter 12W
are simultaneously formed. In this case, dry etching
(etching depth) is about 1 μm. Moreover, yellow and
red filters 2Y and 2R are formed having a substantially
film thickness of 1.2 μm as the etching depth to the
surface.
As seen from the foregoing description, there is
obtained the imaging device 11 in which part of the
transparent filter 12W functions as a micro lens. The
transparent filter 12W and the micro lens are formed
integrally; therefore, the imaging device 11 can be
made thinner.
According to the third embodiment, the transparent
filter 12W having a function as a transparent
planarization layer is formed into the shape of the
micro lens. However, the transparent filter 12W having
a function as a transparent planarization layer may be
intactly formed without forming the micro lens. In
this case, the transparent filter 12W is formed in the
third process of FIG. 13, and thereafter, processes
after the process of forming the photosensitive phenol
resin 13 are not carried out.
As described above, preferably, the ultraviolet
absorbing agent is added to the planarization layer 6
to prevent halation occurring in the pattern exposure
of the colored photosensitive resin.
Moreover, preferably, the ultraviolet absorbing
agent is added to the transparent filter 12W to prevent
the generation of noise resulting from ultraviolet
rays. This is because the light receiving element has
sensitivity in the ultraviolet range.
Fine grains consisting of a metal oxide, such as
cerium oxide and titanium oxide, are used as the
ultraviolet absorbing agent. However, as described
above, the lens shape is transferred to the transparent
filter 12W, and thus, the transparent filter 12W
functions as a transferred type micro lens. In this
case, if the ultraviolet absorbing agent consists of
fine grains of a metal oxide, an inorganic material
becomes optical foreign matter in the resin of the
transferred lens. For this reason, there is a
possibility that light is shielded; as a result, an
image obtained by the imaging device has a blacked-out
portion. Therefore, it is preferable to use a dye
ultraviolet absorbing agent. For example, any of
benzo-triazole, benzo-phenone, triazine, salicylate,
coumarin, xanthene, and a methoxyl arsenic acid
compound may be used as the ultraviolet absorbing
agent.
According to the first to third embodiments,
yellow may be used as an under color other excepting
transparent portions. In other words, yellow may be
contained in common to red portions excepting
transparent portions. In this case, the yellow filter
2Y is formed using a yellow resin while it is formed at
the position formed with the red filter. Thereafter,
the red filter 2R is formed at the position formed with
the red filter.

The fourth embodiment relates to an imaging device
that is provided with a light shield film (antireflection
filter). The light shield film is used for
preventing reflection, diffusion and diffraction
resulting from light other than the incident light
incident on the light receiving elements.
FIG. 16 is a top plan view showing the layout of a
light shield film of an imaging device according to the
fourth embodiment. An imaging device 17 shown in
FIG. 16 includes a light shield film 19 for preventing
reflection and transmission of light. The light shield
film 19 is arranged at the light incident side of the
light receiving element, and at the outer periphery of
an effective pixel part 18 provided with the filter
layer 2. The imaging device 17 has an electrode 20
comprising aluminum for making external electric
connections. The electrode 20 is formed with no light
shield film 19.
A resin liquid dispersing and mixing the organic
pigments given below is usable as the color material of
the light shield film 19. For example, C.I. Pigment
violet 23 and C.I. Pigment Red 177, C.I. Pigment ref
48:1, C.I. Pigment Yellow 139 are given. The foregoing
color material is applied and hardened, and thereby,
the light shield film 19 is formed. However, the color
material is not limited to above, and other pigments
may be used. The light shield film may be a single
layer, or a layer stacking different colors.
The light shield film 19 is arranged at the outer
periphery of the effective pixel part 18 of the imaging
device 17. By doing so, it is possible to prevent the
observed result of the imaging device 17 from being
affected by noise. As a result, the image quality is
enhanced.
In addition, in a conventional imaging device,
stray light may enter the imaging device. This means
that light incident on portions other than the light
receiving elements strays into the imaging device. If
such light is incident on the light receiving element,
this is a factor causing noise. Moreover, if
unnecessary light is incident on the peripheral region
of the light receiving element, this is also a factor
causing noise.
On the contrary, the imaging device 17 of the
fourth embodiment is provided with the light shield
film 19 at the effective opening periphery of the light
receiving element and in part of the semiconductor
substrate (e.g., outer periphery thereof). The light
shield film has the characteristic of preventing
transmission in the visible light wavelength range.
Thus, the light shield film 19 absorbs light incident
on portions other than the light receiving elements.
By doing so, it is possible to prevent unnecessary
light, such as stray light, from being incident on the
light receiving elements. In other words, noise is
reduced; therefore, the image quality obtained by the
imaging device 17 can be enhanced.
According to the fourth embodiment, preferably,
the light shield film 19 has a function of cutting
infrared rays, in addition to the function of cutting
visible light. The function of cutting infrared rays
is realized in the following manner. Specifically, the
light shield film 19 is formed to have a thickness of
0.8 μm using a resin liquid mixed with a black
pigment, such as carbon black, at a solid ratio 40%.
Moreover, an absorption layer absorbing infrared
and ultraviolet rays may be stacked on the light shield
film 19 using a black pigment such as carbon black. By
doing so, it is possible to prevent noise resulting
from stray light caused by infrared and ultraviolet
rays being incident on portions other than the light
receiving elements. Infrared and ultraviolet absorbing
agents are added to the transparent resin used for
forming the micro lens 8. This agent is used as an
absorption film absorbing infrared and ultraviolet
rays. This serves to reduce the material cost.
According to the fourth embodiment, the imaging
device 1 of the first embodiment is provided with the
light shield film 19 and the absorption film. The
imaging devices of other embodiments may be provided
with the light shield film 19 and the absorption film.
The imaging device may also be solely provided with the
light shield film 19. Moreover, ultraviolet and
infrared absorbing agents may be added to the light
shield film 19.

The fifth embodiment relates to an imaging device
31 in which the imaging device 1 of the first
embodiment is additionally provided with a compensating
filter 2Blk.
FIG. 17 is a front view showing a state that
filters are arrayed in the imaging device 31 f the
fifth embodiment. FIG. 18 is a cross-sectional view
showing the imaging device 31 of the fifth embodiment.
FIG. 18 shows cross section taken along a line Ill-Ill'
of FG. 17. In FIG. 18, there is shown the case where
the light receiving element is CMOS. In this case, the
light receiving element may be a CCD, likewise. In the
following, other cross-sectional views of the imaging
device, the light receiving element may be a CMOS or
CCD.
The imaging device 31 of the fifth embodiment
includes filter lay 2, light receiving element 3 and
operator 4. The filter layer 2 is used for extracting
a specified color component of incident light. The
light receiving element 3 observes the incident light
via the filter layer 2.
The filter layer 2 includes a compensating filter
2Blk in addition to transparent, yellow and red filters
2W, 2Y and 2R. One unit of color separation is formed
by combining transparent filter 2W, yellow filter 2Y,
red filter 2R and compensating filter 2Blk one by one.
These transparent filter 2W, yellow filter 2Y, red
filter 2R and compensating filter 2Blk are adjacently
arrayed like a mesh. Each filter has a film thickness
of 1.4 μm, and the pixel pitch (of transparent filter
2W, yellow filter 2Y, red filter 2R and compensating
filter 2Blk) is 2.6 μm.
The compensating filter 2Blk has the following
characteristics. One is an anti-transmission
characteristic (low transmission characteristic) in a
visible light wavelength range. Another is a
transmission characteristic in a long wavelength range
out of visible light. In other words, the compensating
filter 2Blk has a characteristic such that the
transmittance in the infrared range is higher than that
in the visible light wavelength range. Moreover, the
compensating filter 2Blk is visibly black.
According to the fifth embodiment, the
compensating filter 2Blk is formed by optically
overlapping violet (V) and red (R). The following is
given as a method of realizing the foregoing optical
overlapping. Specifically, a piece of filter is formed
using the color material mixing violet color material
and red color material. Moreover, a violet filter and
a red filter may be stacked.
The light receiving element 3 is arranged on the
side opposite to the light incident side of the filter
layer 2. The light receiving element 3 further
includes a compensating light receiving element 3Blk in
addition to incident, yellow and red light receiving
elements 3W, 3Y and 3R. These light receiving elements
are formed and arrayed on the semiconductor substrate
5.
The compensating light receiving element 3Blk
corresponds to the compensating filter 2Blk, and
observes the incident light via the compensating filter
2Blk.
The operator 4 includes flue, green and red
operating units 4B, 4G and 4R. The operator 4 has a
function of calculating the following values. Namely,
the operator 4 calculates blue, green, compensated red
observed data values Db, Dg and HDr based on observed
data values Dw, Dy, Dr and Dblk obtained from incident,
yellow, red compensating light receiving elements 3W,
3Y, 3R and 3Blk.
The red operating unit 4R subtracts an observed
data value Dblk obtained from the compensating light
receiving element 3Blk from an observed data value Dr
obtained from the red light receiving element 3R. By
doing so, the red operating unit 4R calculates a
compensated red observed data value HDr (= Dr - Dblk).
FIG. 18 shows a cross section crossing red and
compensating filters 2R, 2Blk red and compensating
light receiving elements 3R, 3Blk. Other filters and
light receiving elements have the same cross section as
shown in FIG. 18.
In FIG. 18, there is shown a compensating filter
2Blk having a single lay formed of a transparent resin
mixing red and violet pigments. The compensating
filter 2Blk is not limited to the structure shown in
FIG. 18, and may be realized by optical overlapping.
The optical overlapping is realized using a singlelayer
colored resin comprising a mixture of different
color materials (pigment, dye). Moreover, two
different color filters may be stacked, and thereby,
the compensating filter is realized. For example, as
illustrated in FIG. 19, a violet filter 2V and a red
filter 2R are stacked to form the compensating filter
2Blk. Two color materials or more may be used for
adjusting color and transmittance.
If two color filters are optically overlapped, the
compensating filter 2Blk has a transmittance obtained
from the product of the transmittance of each of the
overlapped color filters. Therefore, the compensating
filter 2Blk is formed using optical overlapping,
thereby forming the compensating filter having the
following characteristics. One is an anti-transmission
characteristic in a visible light wavelength range.
Another is a transmission characteristic in the long
wavelength side out of the visible light wavelength
range.
The following pigment may be used as an organic
pigment used for forming the compensating filter 2Blk.
It is an organic pigment comprising the organic pigment
used for the red filter 2R (e.g., C.I. Pigment Red 177,
C.I. Pigment Red 48:1, C.I. Pigment Yellow 139).
FIG. 20 shows a graph of the spectral
transmittance of the compensating filter 2Blk form in
the foregoing manner: transparent, yellow and red
filters, 2W, 2Y and 2R.
As described above, the imaging device 31 executes
a subtraction based on observed data values Dw, Dy, Dr
and Dblk of each light receiving element. By doing so,
the imaging device 31 obtains blue, green and
compensated red, that is, three primary colors Db, Dg
and HDr. In other words, the imaging device 31
performs the foregoing operation, and thereby, includes
virtual blue, green and red filters.
FIG. 21 is a graph showing the spectral
transraittance of virtual blue, green and red filters
obtained by the operation performed by the imaging
device 31. The spectral transmittance of virtual blue,
green and red filters of the imaging device 31 is
compared with that of conventional blue, green and red
color filters. According to the comparative result,
the spectral transmittance of virtual blue, green and
red filters of the imaging device 31 has a
transmittance higher than conventional blue, green and
red color filters. In particular, the virtual blue
filter has a transmittance higher than the conventional
blue color filter in a blue wavelength range.
Therefore, The imaging device 31 of the fifth
embodiment has high blue sensitively; as a result,
color balance is improved.
Blue, green and compensated red observed data
values Db, Dg and HDr obtained from the imaging device
are calculated in the following manner. Namely,
observed data value in the infrared range is
subtracted. Thus, according to the spectral
transmittance curve of the virtual blue, green and red
filters, there is desensitization of the infrared range
(cut). Therefore, the imaging device of the fifth
embodiment requires no infrared cut filter; as a
result, he imaging device can be formed thinner.
Moreover, it is possible to prevent a reduction of red
sensitivity resulting from the case where an absorption
infrared cut filter is provided.
The same explanation as in the first embodiment
applies to "virtual color filter", "noise by dark
current", "spectral peaks and troughs" and "ultraviolet
and infrared agents".
The following is a supplemental explanation
regarding the "spectral characteristic of the
compensating filter 2Blk".
FIG. 22 is a graph showing the spectral
characteristic of the compensating filter 2Blk formed
in the following manner. The compensating filter 2Blk
is formed using acrylic resin dispersion and mixing a
violet pigment (e.g., C.I. Pigment Violet 23) and the
pigment used for the red filter 2R. The filter has a
thickness of 1.4 μm.
The transmittance of the compensating filter 2Blk
is approximately the same (same or approximate) as the
red filter of FIG. 20 in a long wavelength side out of
the visible light wavelength range.
The observed data value Dblk obtained from the
compensating light receiving element 3Blk is subtracted
from the observed data value Dr received from the red
light receiving element 3R. By doing so, the observed
result of the infrared range is deleted from the
observed data value Dr received from the red light
receiving element 3R. In other words, the compensating
filter 2Blk performs a function as an infrared cut
filter with respect to the red observed data value.
The compensating filter 2Blk shown in FIG. 22
differs from a general absorption type infrared cut
filter sown in FIG. 23. The transmittance (i.e.,
effective transmittance as an infrared cut filter) is
low, in a wavelength range from about 600 nm to 650 nm.
Therefore, after the operation (subtraction) is
performed, the obtained color rendering is further
improved.
According to the fifth embodiment, the difference
is less than 5% in the transmittance between the
compensating filter 2Blk and the red color filter shown
in FIG. 1 in the light wavelength range from 400 nm to
550nm and a range greater than 750 nm. By doing so,
the compensated red observed data value HDr is obtained
without being affected by the infrared ray and other
colors. Therefore, the red color reproducibility is
enhanced. Specifically, the transmittance of the
compensating filter 2Blk is kept at a low value from
400 nm to 630 nm. Thereafter, the transmittance curve
suddenly rises up in a range from 630 nm to 750 nm.
When exceeding 750 nm, the transmittance is kept at a
high value.
The general absorption type infrared cut filter is
in the vicinity of the wavelength 630 nm when the
transmittance value becomes half (50%). In general
inorganic multi-layer infrared cut filters, the
wavelength when the transmittance value becomes half is
approximately 700 μm. In the compensating filter 2Blk
formed using optical overlapping of violet and red, the
wavelength when the transmittance value becomes half is
in a range from approximately 650 nm to 660 nm. In the
compensating filter 2Blk formed using optical
overlapping of cyan and red, the wavelength when the
transmittance becomes half is in a range from
approximately 740 nm to 750 nm.
Considering the foregoing point, the point P of
the compensating filter 2Blk when the transmittance
becomes half is within a wavelength range from 630 nm
to 750 nm. This is preferable from the viewpoint of
improving the red observed data value. Moreover, it is
preferable to add an ultraviolet absorbing agent to the
transparent filter 2W.
The imaging device 31 of the fifth embodiment
calculates the compensated red observed data value HDr.
The compensated red observed data value HDr is
calculated from the difference between red observed
data value Dr and compensating observed data value
Dblk. Therefore, the compensating filter 2Blk has the
transmittance shown in FIG. 22, and thereby, the
compensated red observed data value HDr is not affected
by infrared rays or other color light. Moreover, the
red sensitivity is high; therefore, an imaging device
31 having excellent color reproducibility is obtained.
According to the fifth embodiment, the
compensating filter 2Blk may be formed by optically
overlapping two colors; that is, violet and red or cyan
and red. The compensating filter 2Blk is formed by
combining the foregoing two colors. By doing so, the
wavelength position of the compensating filter 2Blk
corresponding to 50% can be adjusted according to the
ratio of color materials. Color control (adjustment)
is further made with respect to the compensated red
observed data value HDr.
The following controls may be carried out using
other color materials or other color organic pigments.
For example, violet, blue and green. One is color
control (e.g., gray level control) in the visible light
wavelength range of the compensating filter 2Blk.
Another is the rise of the transmittance curve of the
compensating filter 2Blk in the near-infrared
transmission spectra of 700 nm or after 700 nm.
Another is control of the wavelength position when the
transmittance value becomes half.
Moreover, the imaging device 31 of the fifth
embodiment can delete the light observed result of the
infrared range, which is not in the human visible
range. Therefore, an imaging result close to that of
the human sense of vision can be obtained.
The imaging device 31 of the fifth embodiment
differs from the general absorption type infrared cut
filter having the transmittance characteristic shown in
FIG. 23. Namely, the imaging device 31 relaxes light
absorption in a wavelength range from 550 nm to 650 nm.
Therefore, red color rendering is improved.
In other words, the imaging device 31 of the fifth
embodiment includes virtual blue, green and red filters
having high transmission. In particular, blue and red
observed accuracy are improved as compared with the
conventional imaging device.
According to the fifth embodiment, the
compensating pixel of the imaging device observes light
in the infrared rage. The compensating pixel observed
result is subtracted from the red pixel observed
result, thereby realizing an infrared absorbing
function. With respect to other colors (blue, green),
the infrared range is subtracted from the observed
result. As a result, it is possible to omit the
infrared absorption type infrared cut filter included
in the conventional camera module optical system. This
serves to make thin the camera.
According to the fifth embodiment, yellow may be
used as under color for other colors except transparent
portions. In other words, yellow may be included in
red and compensating portions except transparent
portions. In this case, the yellow filter 2Y is formed
of yellow resin, and then, formed at both positions of
forming red and compensating filters. Thereafter, the
red filter 2R is formed at the position of forming the
red filter while the compensating filter 2Blk is formed
at the position of forming the compensating filter.

According to the sixth embodiment, an imaging
device 39 differs from the imaging device 31 of the
fifth embodiment in the following point. The
transparent filter 2W and the resin layer 7 are
integrated to form a transparent filter 10W. This is
equivalent to the imaging device 9 of the second
embodiment, which is formed with the compensating
filter 2Blk. FIG. 24 shows a cross section of the
imaging device 39. FIG. 24 is a cross-sectional view
taken along a ling Ill-Ill' of FIG. 17.
As described above, in the imaging device 39 of
the sixth embodiment, the process of forming the
transparent filter 10W and the transparent
planarization layer is integrated. Thus, there is no
need of independently providing a process of forming
the pattern of the transparent filter, that is, in
filter formation. Therefore, the manufacture process
is simplified. In other words, four color filters are
formed via the process of forming three color filters.
Namely, one process of forming the filter is removed.
Oeventh embodiment^
According to the seventh embodiment, an imaging
device 41 differs from the imaging device of the sixth
embodiment in the following point. The transparent
filter 2W and the micro lens 8 are integrated to form a
transparent filter 12W. This is equivalent to the
imaging device 11 of the third embodiment, which is
formed with the compensating filter 2Blk. FIG. 25
shows a cross section of the imaging device 41.
FIG. 25 is a cross-sectional view taken along a ling
Ill-Ill' of FIG. 17.
According to the seventh embodiment, the
transparent filter 10W and the micro lens 8 are
integrally formed, as described above. Therefore, this
serves to make thin the imaging device 41.

According to the eighth embodiment, a light shield
film is provided at areas other than an area at which
an incident light is incident.
FIG. 26 is a front view showing a first
arrangement of a light shield film 19 of an imaging
device according to the eighth embodiment. FIG. 27 is
a cross-sectional view taken along a ling IV-IV of
FIG. 26.
The compensating filter 2Blk described in the
fifth embodiment is used as the light shield film 19.
By doing so, it is possible to cut light in a visible
light wavelength range, and to reduce stray light on
the frame (outer periphery portion) of the imaging
device 47.
Incidentally, the light shield film 19 may have a
function of cutting infrared rays in addition to the
function of cutting visible light. The foregoing light
shield film cutting visible light and infrared ray is
realized in the following manner. For example, the
light shield film is formed to have a film thickness of
0.8 ju m using a resin liquid mixed with a pigment such
as carbon black at a solid ratio 40%.
FIG. 28 is a cross-sectional view showing a second
arrangement of the light shield film of an imaging
device 44 of the eighth embodiment.
The imaging device 44 is characterized in that a
light shield film 15 and a film 16 are stacked at the
outer periphery of the CMOS light receiving element 3.
For example, the compensating filter 2Blk is
usable as the light shield film 15. In other words,
the light shield film 15 is formed using the same
process as that for forming the compensating filter
2Blk, and thereby, it has the same material quality.
The film 16 has at least one of infrared and
ultraviolet absorbing functions.
As described above, the imaging devices 44 and 47
of the eighth embodiment are provided with the light
shield film. The light shield film is formed at the
effective opening periphery of the light receiving
element and at part of the semiconductor substrate 5
(e.g., outer periphery of the semiconductor substrate
5). In addition, the light shield film has an antitransmission
characteristic in a visible light
wavelength range. Therefore, the light shield film
absorbs light incident on areas other than the light
receiving element. By doing so, it is possible to
prevent unnecessary light such as stray light from
being incident on the light receiving element. This
serves to reduce noise, and to improve the image
quality obtained by the imaging device.
According to the eighth embodiment, the light
shield film is arranged at the outer periphery of the
effective pixel part. If the light receiving element
is a CCD, the light shield film may be formed on the
interconnection.

The ninth embodiment relates to a detailed example
of the compensating filter 2Blk according to the fifth
embodiment.
The compensating filter 2Blk of the ninth
embodiment has a transmittance of less than 5% with
respect to light having a wavelength range 400 nm to
550 nm. According to this spectral characteristic, the
wavelength range corresponding to 50% transmittance is
in the range from 620 nm to 690 nm. The transmittance
is 70% with respect to light having a wavelength
700 μm.
A general absorption type infrared cut filter
starts to absorb light from the vicinity of 550 nm.
For this reason, according to the ninth embodiment,
consideration needs to be given to the increased
transmission range of the compensating filter 2Blk used
as means for cutting infrared rays. Namely, the rise
is 550 nm at the shortest light wavelength. Therefore,
the compensating filter 2Blk has a low transmission
(transmittance of less than 5%) range from 400 nm to
700 nm.
The compensating filter 2Blk of the ninth
embodiment performs an infrared cut function. For this
reason, the compensating filter 2Blk has a transmission
characteristic in a red and near-infrared range after
the wavelength of 550 nm. Here, calculation is made
based on human vision. The stimulus value of an RGB
color function peaks at 600 nm, and then, drops toward
700 nm. Thus, the compensating filter 2Blk preferably
has the following spectral transmittance characteristic
(curve shape). Specifically, the transmittance rises
from the vicinity of 600 nm, and then, becomes high
from the vicinity of 700 nm. Therefore, according to
the spectral transmittance characteristic, the
wavelength range (half value range) when the
transmittance becomes 50% is preferably 620 nm to
690 ran.
The compensating filter 2Blk has an antitransmission
characteristic (low transmission
characteristic) in a visible light wavelength range.
The compensating filter 2Blk is visibly seen as black.
According to the ninth embodiment, the
compensating filter 2Blk is formed of a colored resin
composite containing at least each pigment, that is,
C.I. Pigment 23 and C.I. Pigment Yellow 139. Moreover,
the compensating filter 2Blk is formed of a colored
resin composite containing each pigment, that is, C.I.
Pigment 23, C.I. Pigment Yellow 139 and C.I. Pigment
Red 254.
According to the ninth embodiment, each filter has
a film thickness of 1.0 μm to 1.1 Aim, and the pixel
pitch (of transparent, yellow, red and compensating
filters 2W, 2Y, 2R ad 2Blk) is 2.6μm.
The following three pigments are used as a
compensating colored resin composite used for forming
the compensating filter 2Blk.
C.I. (Color Index) Pigment Red 245 (abbr. R254)
C.I. Pigment yellow 139 (abbr. Y139)
C.I. pigment Violet 23 (abbr. V23)
Of the three pigments, the R254 may be eliminated.
In addition to these three pigments, for color
(transmission wavelength) control, a slight amount of
another pigment is added.
The weight ratio (%) to the compensating filter
colored resin composite of these three pigments (R254,
Y139, V23) is as follows.
R254 = 0 to 15%
Y139 = 30 to 40%
V23 = 55 to 65%
The compensating filter colored resin composite
contains resin and a solution in addition the foregoing
pigments. For example, in order to disperse the
pigment Y139 itself, the following is contained with
respect to the Y139 having 7 weight parts.
Acrylic resin solution (solid 20%): 40 weight
parts
Dispersant: 0.5 weight parts
Cyclohexanone: 23.0 weight parts
The same solution as above is used to disperse V23
and R254.
The following is an explanation about the method
of manufacturing the compensating filter 2Blk of the
ninth embodiment.
A pigment paste of the forgoing Y139 and V23 is
prepared with the weight ratio and weight part
described above. The following materials are mixed to
form a compensating colored resin composite.
Y139: 14.70 weight parts
V23: 20.60 weight parts
Acrylic resin solution: 14.00 weight parts
Acrylic monomer: 4.15 parts
Initiator: 0.7 weight parts
Sensitizer: 0.4 weight parts
Cyclohexanone: 27.00 weight parts
PGMAC: 10.89 weight parts
Then, the compensating colored resin composite is
applied using a spin coater, and thereafter, a dry film
is formed having a thickness of 1.1 μm.
The resultant film (composite) is dried in a state
of being placed on a hot plate at 70°C for one minute.
Then, the resultant film is exposed using an i-line
stepper via a mask forming 5 μm pixel pattern. In
this case, the exposure sensitivity is 1000 mj/cm2.
Using an organic alkali solution, the
semiconductor substrate 5 is spun while being developed
for 60 seconds using shower coating. The semiconductor
substrate 5 is sufficiently rinsed using pure water,
and thereafter, is dried by spinning to remove water.
A heat treatment is carried out on the hot plate
at 220°C for six minutes to harden a pixel pattern
film. By doing so, a compensating filter having a
thickness of 1.1 μm is formed.
A carrier for fixing pigments contained in each
filter colored resin composite is composed of acrylic
resin, transparent resin, and the precursor or mixture
of them.
The transparent resin has a transmittance of 80%
or more over the entire wavelength range from 400 to
700 μm, which is a visible range. More preferably, the
transparent resin has a transmittance of 90% or more.
The transparent resin includes thermoplastic,
thermosetting and activation energy hardening resins.
The precursor includes monomer or oligomer generating a
transparent resin hardened by activation energy
radiation. The transparent resin may be formed of a
single resin or a mixture of two or more resins.
FIG. 29 is a graph showing the spectral
transmittance characteristic of the compensating filter
manufactured in the foregoing manner. Thus, the
compensating filter 2Blk of the ninth embodiment has
the following spectral transmittance characteristic.
Specifically, the transmittance is less than 5% with
respect to light of the wavelength range from 400 nm to
550 nm. On the other hand, the transmittance becomes
70% or more with respect to light having a wavelength
700 nm. The wavelength position when the transmittance
becomes 50% is within a range from 620 nm to 690 nm.
Therefore, the compensating filter 2Blk of the
ninth embodiment differs from the general absorption
type infrared cut filter shown in FIG. 23. Namely, the
compensating filter 2Blk has low transmittance in the
vicinity of a range from 600 nm to 650 nm. Thus, this
serves to further improve red color rendering after the
operation (subtraction).
Preferably, the difference is less than 5% between
the compensating filter and red color filter (e.g., red
filter having transmittance shown in FIG. 1) in the
light wavelength range from 400 nm to 550 nm and after
750 nm. Specifically, the transmittance characteristic
shown in FIG. 30 is given, and thereby, a compensated
red observed data value HDr is obtained without
receiving an influence by infrared ray and other
colors. Therefore, red reproducibility is enhanced.
The compensating filter 2Blk of the ninth
embodiment has the following spectral characteristic.
Namely, the transmittance is low in a wavelength range
from 400 nm to 550 nm; therefore, visible light is
shielded. Thus, it is possible to prevent color noise
from being generated in the imaging device provided
with the compensating filter 2Blk.

The tenth embodiment relates to another example of
the compensating filter 2Blk of the fifth embodiment.
A compensating filter 2Blk of the tenth embodiment
is formed of pigment paste having the following
composition. The compensating filter has a film
thickness of 1.1 μm.
Pigment:
Y139: 11.3 weight parts
R254: 4.23 weight parts
V23: 19.77 weight parts
FIG. 31 shows the spectral characteristic of the
compensating filter 2Blk of the fifth embodiment. The
pigment composition of a compensating filter colored
resin composite is as follows. The pigment R254 is
added to the pigment composition (pigment V23 and
pigment Y139) of the ninth embodiment.
The spectral characteristic of the compensating
filter 2Blk of the fifth embodiment will be described
using the graph of FIG. 31. In the graph, the light
wavelength (nm) is given on the horizontal axis, and
light transmittance of each wavelength is given on the
vertical axis. As seen from the graph, the
transmittance is less than 5% with respect to the
wavelength range from 400 nm to 550 nm. The
transmittance becomes 70% or more with respect to light
having a wavelength 700 nm. The wavelength position
when the transmittance becomes 50% is in a range from
620 nm to 690 nm.
The compensating filter 2Blk of the tenth
embodiment has the following spectral characteristic.
Namely, the transmittance is low in a wavelength range
from 400 nm to 550 nm; therefore, visible light is
shielded. Thus, it is possible to prevent a color
noise from being generated in the imaging device
provided with the compensating filter 2Blk.

The llth embodiment relates to an imaging device,
which includes a transparent filter having an
ultraviolet light absorbing function. The imaging
device of the llth embodiment includes an imager 110
and an operator 120.
FIG. 32 is a schematic view showing the
configuration of the imager 110 and the operator 120 of
the imaging device of the llth embodiment. FIG. 33 is
a view to explain the concept of an arrayed state of
color filters of the imager 110 when viewing them from
the incident light side. FIG. 34A and FIG. 34B are
respectively cross-sectional views taken along lines
V-V and VI-VI' of the imager 110.
The imager 110 includes substrate 111, light
receiving element 112, planarization layer 113, color
filter 114 and micro lens 115.
The substrate 111 is a semiconductor substrate
including an interconnection layer capable of making an
electric signal exchange. The substrate 11 sends an
intensity value (electric signal) of light received by
the light receiving element 112 via the interconnection
layer.
The light receiving element 112 is formed on the
substrate 111, and when receiving light, photoelectrically
converts the received light into an
electric signal. As described later, according to the
llth embodiment, three color filters 114, that is,
transparent, yellow and red filters 114W, 114Y and 114R
are formed. For convenience, light receiving elements
receiving light via transparent, yellow and red filters
114W, 114Y and 114R are each called white, yellow and
red light receiving elements 112W, 112Y and 112R.
The white light receiving element 112W sends an
electric signal obtained from the received light to a
blue operating unit 121B.
The yellow light receiving element 112Y sends an
electric signal obtained from the received light to the
blue operating unit 121B and a green operating unit
121G.
The red light receiving element 112R sends an
electric signal obtained from the received light to the
green and red operating units 121G and 121R.
The planarization layer 113 is stacked on the
surface of the light incident side of the substrate 111
formed with light receiving elements 112. The
planarization layer 113 planrizes the surface of the
color filter 114. Moreover, the planarization layer
113 is formed of an acrylic resin containing coumarin
dye at a dye concentration 5% as an ultraviolet light
absorbing agent. By doing so, the planarization layer
113 has the following spectral characteristic.
Specifically, the planarization layer 113 has a
transmittance of 50% with respect to light of a
wavelength range from 365 nm to 420 nm. Moreover, the
planarization layer 113 has a transmittance of 90% or
more with respect to light having a wavelength of
450 nm or more.
The color filters 114 are independently formed on
each light receiving element 112 to be adjacent to each
other. According to the llth embodiment, three, that
is, transparent, yellow and red filters 114W, 114Y and
114R are formed as the color filter 114. Two pixels
are used as the yellow filter 114Y while one pixel is
used as each of transparent and red filters 114W and
114R. Thus, one unit of color separation is formed
using four pixels in total. When transparent, yellow
and red filters 114W, 114Y and 114R are shown as W, Y
and R', respectively, a color filter 114 having the
arrayed state shown in FIG. 33 is formed.
The transparent filter 114W is a colorless and
transparent color filter formed of the same material as
the planarization layer 113. Namely, the transparent
filter 114W is formed of an acrylic resin containing
coumarin dye at a dye concentration of 5%. By doing
so, the transparent filter 114W has the following
spectral characteristic. Specifically, the transparent
filter 114W has a transmittance of 50% with respect to
any of a light wavelength range from 365 nm to 420 nm.
Moreover, the transparent filter 114W has a
transmittance of 90% or more with respect to light
having a wavelength of 450 nm or more.
The yellow filter 114Y is a filter for extracting
yellow light (synthesizing red and green components) of
the light incident on the light receiving element.
Specifically, the yellow filer 114Y is a filter
transmitting light of a wavelength of the green range
or more, which includes red range light and infrared
range light. C.I. Pigment Yellow 139 is usable as the
color material for the yellow filter 114Y.
The red filter 114R is a filter for extracting red
light (synthesizing red and green components) of the
light: incident on the light receiving element.
Specifically, the red filer 114R is a filter
transmitting light in a wavelength of the red range or
more, which includes infrared range light. C.I.
Pigment Red 117, C.I. Pigment 48:1 and C.I. Pigment
Yellow 139 is usable as the color material for the red
filter 114R.
The micro lens 115 is used for collecting light to
the light receiving element 112, and formed on each
color filter 114. Incidentally, the micro lens 115 is
formed of the same material as the planarization layer
113 and the transparent filter 114W.
The operator 120 includes blue, green and red
operating units 121B, 121G and 121R. The operator 120
calculates light three-primary color observed data
values based on the intensity value of light receiving
from the imager 110. By doing so, color image data is
reproducible.
The blue operating unit 121B calculates a blue
light observed data value. Specifically, the blue
operating unit 121B receives an electric signal from
white and yellow light receiving elements 112W and
112Y. The blue operating unit 112B subtracts an
intensity value of light received from the yellow light
receiving element 112Y from that of light received from
the white light receiving element 112W. By doing so,
the blue operating unit 121B obtains the blue light
observed data value.
The green operating unit 121G calculates a green
light observed data value. Specifically, the green
operating unit 121G receives an electric signal from
yellow and red light receiving elements 112Y and 112R.
The blue operating unit 112B subtracts an intensity
value of light received from the yellow light receiving
element 112Y from that of light received from the red
light receiving element 112R. By doing so, the blue
operating unit 121B obtains the green light observed
data value.
The red operating unit 121R calculates a red light
observed data value. Here, the red operating unit 121R
takes an intensity value of light received from the red
light receiving element 112R as a red light observed
value data.
The operation of the imaging device of the llth
embodiment will be hereinafter described with reference
to a flowchart of FIG. 35.
When light is radiated from an observed object,
part of the light is incident on the imager 110 as an
incident light (step SI).
The incident light is collected via the micro lens
115, and thereafter, travels to the light receiving
element 112 transmitting through the color filter 114.
Here, transparent, yellow and red filters 114W, 114Y
and 114R are formed as the color filter. Therefore,
white, yellow and red light receiving elements 112W,
112Y and 112R extracts incident light, yellow light and
red light, and removes ultraviolet light (step 32).
Light entering each light receiving element 112 is
converted into an electric signal, and thereafter, sent
to the operator 120 (step S3). In this case, light
transmitting through each of transparent, yellow and
red filters 112W, 112Y and 112R is sent to the operator
120.
Thereafter, operating units 121 of the operator
120 calculate red, green and blue light observed data
values, respectively (step S4). In this case,
intensity values of incident, yellow and red lights
obtained by light receiving elements are set as Dw, Dy
and Dr. Moreover, three primary colors, that is, red,
green blue observed data values are set as Db, dg and
dr. The foregoing setting is made, and thereby, the
following equations (3) and (4) are satisfied.
Db = Dw - Dy ... (3)
Dg = Dy - Dr ... (4)
Three primary color light data in each pixel
obtained in this manner are synthesized, and thereby,
color image data of the observed object is created
(step S5) .
As described above, the imager 110 of the llth
embodiment includes planarization layer 113 and
transparent filter 114 having the following spectral
characteristic. Namely, the transmittance is 50% with
respect to light having a wavelength range from 365 nm
to 420 nm. Moreover, the transmittance is 90% or more
with respect to light having a wavelength of 450 nm or
more. Therefore, the imaging device 20 can obtain
light observed data values corrected for effects due to
ultraviolet rays. By doing so, a blue light observed
data value close to the human sense of vision is
obtained. Thus, it is possible to provide an imager
110 that is excellent in color balance and color
reproducibility.
Moreover, the imager 110 is configured to have
micro-fabricated pixels. Namely, the micro lens 115
for collecting light to each light receiving element
112 is formed on each color filter 114. By doing so, a
small-sized imaging device is provided.
The color filter 114 of the imager 110 includes
yellow and red filters 114Y and 114R. Thus, a color
image from the observed object is reproduced from the
intensity value of light via transparent, yellow and
red filters 114W, 14Y and 114R. This serves to reduce
a noise as compared with an imaging device using the
conventional compensating color filter. Therefore,
vivid colors close to primary colors, are reproduced.
As seen from the foregoing equation (3), the blue
light data is calculated based on the intensity value
of the incident light via the transparent filter 114W.
Depending on the kind of the imaging device, the light
receiving element 112 has various sensitivities in the
ultraviolet range. For this reason, when the light
receiving element 112 receives incident light that
includes ultraviolet rays, the following problems
arise. In brief, it is difficult to consistently
reproduce the blue light observed data value due to the
many kinds of imaging devices. Moreover, alignment
with the human sense of vision becomes insufficient.
In order to solve the foregoing problems, the
transparent filter 114W of the llth embodiment is used.
By doing so, it is possible to obtain a light observed
data value that is corrected for effects due to
ultraviolet rays. Therefore, reproducibility of the
blue light observed data value and color rendering are
improved regardless of the kind of imaging device.
Moreover, the planarization layer 113 absorbs an
influence of halation from the substrate in pattern
exposure when the color filter is formed using a
photolithography process. This serves to prevent the
pixels of the color filter from being thickened.
Namely, an ultraviolet absorbing agent is added to the
planarization layer 113, and thereby, it is possible to
prevent halation of the exposure light from the
substrate 111. Thus, a filter having a good shape is
formed.
The imaging device of the llth embodiment performs
the following operation to obtain the blue light
observed data value. The blue light observed data
value is obtained based on the electric signal obtained
via the transparent filter 114W and the same is
obtained via the yellow filter 114Y. The transparent
filter 114W has low transmittance in a short-wavelength
range and has the rise part of the transmittance.
Moreover, the transparent filter 114W has high
transmittance in a long-wavelength range. Thus, the
transparent filter 114W has a substantially S-shaped
spectral transmittance curve. In this case, the
transparent filter 114W has the spectral characteristic
curve showing the following features. Namely, light
transmittance becomes 50% in a light wavelength range
from 365 to 420 nm. (More preferably, the light
transmittance becomes 50% in a light wavelength range
from 390 to 420 nm.) By doing so, the blue light
observed data value obtained from the operation has the
following advantages. Specifically, color balance and
reproducibility are excellent, and a vivid blue color
can be seen with the human eye.
A supplemental explanation about the foregoing
point is made. FIG. 36 is a graph showing the human
eye stimulation value of light, which changes according
to wavelength of R (red), G (green) and B (blue)
colors. As seen from FIG. 36, a B (blue) human eye
spectral stimulus value has a peak (maximum value) in
the vicinity of a light wavelength from 445 to 450 nm.
The half value (50% stimulus value of the maximum
value) of the maximum stimulus value exists in the
vicinity of a light wavelength from 420 nm to 425 nm on
a short-wavelength side from light wavelength becoming
the maximum stimulus value. Thus, the transparent
filter of this embodiment is used, and thereby, a vivid
blue color can be seen by the human eye. As shown in
FIG. 1, the peak value of light transmittance of the
conventional blue filter exists in a light wavelength
range of about 450 nm. The light transmittance in the
light wavelength range of about 540 nm is about 80%
(transmittance is measured using a glass substrate as a
reference).
The transparent filter 114W has a light
transmittance of 90% or more in the wavelength of
450 nrn. Therefore, the imaging device of the llth
embodiment improves blue sensitivity.
According to the llth embodiment, the transparent
filter 114W is formed of an acrylic resin containing
coumarin dye at a dye concentration of 5% as an
ultraviolet light absorbing agent. Resins other than
acrylic resin are usable. For example, a resin
containing one or more of epoxy, polyimide, and phenol
novolac resins may be used.
According to the llth embodiment, the transparent
filter 114W is formed of an acrylic resin containing
coumarin dye at a dye concentration of 5% as an
ultraviolet light absorbing agent. For example,
benzotriazole, benzophenone, salicylic acid, and hinder
domine compounds may be used as the ultraviolet
absorbing agent. Moreover, the following dyes are
usable. Specifically, azoic dye, azoic metal complex
salt dye, anthraquinone dye, indigoid dye, thioindigoid
dye, phthalocyanine dye, diphenyl-methane dye,
tri-phenyl methane dye, xanthene dye, thiazine dye,
kaothine dye, cyanine dye, nitro dye, quinoline dye,
naphthoquinone dye, and oxiasin dye. Moreover, an
optical polymeric monomer, such as bi-functional
monomers or tri-functional monomer or multi-functional
monomer is usable. As the bi-functional monomer,
1.6-hexadior acrylate, ethylene glycol di-acrylate,
neo-penthyl glycol di-acrylate, and tri-ethylene glycol
di-acrylate are given. As the tri-functional monomer,
tri-methylolu prohasen tri-acrylate, pentaerythritol
tri-acrylate, tris (2-hydroxymethyl) isocyanate are
given. As the muli-functional monomer, ditri-methylolu
propantetra acrylate, di-pentaerythritol penta and
hexacrylate are given. As others, optical polymer
initiators such as the following derivatives are
usable. Specifically, halo-methylation triazine
derivative, halo-methylation oxadiazol derivative,
imidazol derivative, benzoinalkyl ether group,
anthraquinone derivative, benzanthron derivative,
benzophenone derivative, acetophenone derivative,
thioxisanton derivative, benzoic acid ester derivative,
acridine derivative, phenazin derivative and titanium
derivative. A functional group having ultraviolet
light absorption is pendent to a resin polymer or
monomer as a hardener, or polymerized to have a group
incorporated into a polymer. For example, a quinone
group and anthracene may be introduced into a polymer,
or a monomer having an ultraviolet light absorption
group may be added.
The foregoing ultraviolet light absorbing agent is
properly used, and thereby, the spectral characteristic
of the transparent filter 114W is changed. The half
value on the short-wavelength side (light wavelength
value when transmittance becomes 5% in the spectral
characteristic curve) is set. By doing so, it is
possible to select the color characteristic (color and
organic pigment close to actual visual sensitivity).
(Peeling of pixels)
Peeling of pixels will be hereinafter described.
In recent years, high-definition CMOS and CCD
having six million pixels or more are required. In the
foregoing high-definition CMOS and CCD, it is
frequently necessary to use a color filter having a
pixel size of 2 /zm x 2 jum or less.
However, there is a problem that such color filter
(pixel) is easy to peel off, resulting from the scaledown
of the pixel size. In particular, the foregoing
problem becomes very apparent in a color filter using a
blue organic pigment. This is because the
transmittance of the blue color resist is low (less
than 1%) in a pattern exposure light wavelength of
365 nm. For this reason, the exposure light does not
travel to the lower portion of the blue color resist.
In other words, if the blue color filter is patterned
and exposed using a photolithography process, the
portion to be inherently hardened does not have the
required hardness. On the other hand, in the red and
green color resists, the pattern exposure light of the
wavelength 365 nm is sufficiently transmitted through
the resist (transmittance range from about 5 to 10%).
As a result, the lower portion of the color resist is
sufficiently hardened. Thus, red and green color
filters are relatively hard to peel off.
Conversely, in order to fully harden the color
resist and to prevent the color filter from peeling
off, the following is required. Specifically, the
transmittance of the blue color resist is made high
with respect to the pattern exposure light of the
wavelength of 365 nm. However, if the transmittance is
made high in the wavelength range of the pattern
exposure light of the blue color resist, the following
problem arises. Namely, the transmittance becomes high
in red and green light wavelength ranges where the
transmittance should be made as low as the blue color
resist. As a result, color separation as blue color
resist is reduced. For this reason, the imaging device
using the conventional blue, green and red filters has
the following problem. That is, light with respect to
several colors is transmitted; for this reason, color
separation becomes worse.
In order to solve the foregoing problem, in the
imaging device of the llth embodiment, white and yellow
filters are hardened in the pattern exposure light
having the wavelength 356 nm. This serves to prevent a
phenomenon in which pixels peel off, and to calculate
the blue observed data value. Therefore, an imaging
device having an improved color separation is provided.
Moreover, the following problem arises. Namely,
the micro-fabricated color filter receives an influence
of halation from the substrate in pattern exposure
using the photolithography process. As a result, the
pixels become thicker. Thus, color un-evenness and
mixing occur.
In order to solve the foregoing problem, the
imaging device of the llth embodiment has the
planarization layer 113 to which the ultraviolet
absorbing agent is added. Therefore, the planarization
layer 113 absorbs halation of exposure light from the
substrate in the pattern exposure. As a result, it is
possible to. prevent the pixels of the color filter from
becoming thick, and to form a filter having a good
shape. Thus, an imaging device having an improved
color separation is provided.
<12th embodiment>
The 12th embodiment relates to a method of
manufacturing the imager 110 according to the llth
embodiment.
The method of manufacturing the imager 110
according to the 12th embodiment will be hereinafter
described with reference to FIG. 37A to FIG. 37D and
FIG. 38A to FIG. 38E.
A planarization layer 113 is formed on a substrate
111 formed with light receiving elements (112W, 112Y in
FIG. 37) (FIG. 37A). The planarization layer 113 is
formed of an acrylic resin containing coumarin dye at a
dye concentration of 5%.
A yellow resin layer YL is formed on the
planarization layer 113. The yellow resin layer YL is
a photosensitive resin layer formed in the following
manner. For example, C.I. Pigment Yellow 139, organic
solution such as cyclohexanone and PGMEA, polymer
vanish, monomer and initiator are added to a
photosensitive acrylic resin.
Then, pattern exposure is carried out using a mask
M (FIG. 37B). In this case, the exposed portions start
a chemical reaction, and become alkali in-solution.
Portions to which light is radiated are removed
using a developer, such as an alkali solution. By
doing so, the Yellow filer 114Y is formed (FIG. 37C).
In other words, the yellow filter 114Y is formed via
the photolithography process.
Although no illustration is given, the red filter
114R is formed in the same manner as above.
After yellow and red filters 114Y and 114R are
formed, a transparent filter 114W is formed (FIG. 37D).
Then, a lens layer LL is formed using a
transparent resin. Specifically, the lens layer LL is
formed of the same material as that of the
planarization layer 113 (FIG. 38A).
A phenol resin layer is formed on the lens layer
LL (FIG. 38B). The phenol resin layer 116 is formed
for controlling the etching rate in dry etching
described later to obtain a micro lens of the desired
shape. Thus, preferably, the etching rate of the
phenol resin layer 116 is slower than that of a lens
material 117M. In this case, the phenol resin layer
116 performs a function of controlling thermal reflow
when forming the lens material 117M described later
using the thermal reflow.
A photosensitive resin layer 117 is further formed
on the phenol resin layer 116 (FIG. 38C). The
photosensitive resin layer 117 is formed of an acrylic
resin having alkali soluble, photosensitive and thermal
reflow.
Then, the photosensitive resin layer 117 is formed
into a rectangular pattern using the photolithography
process. Thereafter, the photosensitive resin layer
117 is reflowed to make it round, using a heat
treatment. By doing so, the lens material 117M is
formed (FIG. 38D).
Dry etching is carried out using the lens material
117M as a mask. By doing so, the shape of the lens
material 117 is transferred to the lens layer LL via
the phenol resin layer 116, and thus, a micro lens 115
is formed (FIG. 38E).
According to the foregoing method, the imager 110
is manufactured.
In the imager 110, the transparent filter 114W and
the micro lens 115 each have the same material quality,
and are integrally formed. This serves to simplify the
manufacture process.
Specifically, according to the 12th embodiment,
the transparent filter 114W and the lens layer LL for
forming the micro lens 115 are independently formed.
The transparent filter 114W and the micro lens 115 have
the same material quality; therefore, the processes of
FIG. 37D and FIG. 38A are simultaneously carried out.
In other words, after the process of FIG. 37D, a
portion for forming the transparent filter 114W is
filled. Then, the lens layer LL containing an
ultraviolet light absorbing agent is applied to cover
the red and yellow filters 114R and 114Y by one-time
coating. Thereafter, the process of forming the micro
lens 115 is carried out. By doing so, it is possible
to manufacture an imager 110A shown in FIG. 39 having a
structure in which the transparent filter 14W and the
micro lens 115 are integrally formed. This serves to
simplify the manufacture process.
As depicted in FIG. 40, an imager HOB is formed
with no planarization layer 113, and thereby, the
manufacture process is further simplified.
<13th embodiment>
FIG. 41 is a schematic view showing the
configuration of an imaging device according to 13th
embodiment of the present invention. FIG. 42 is a view
to explain the concept of a state in which color
filters 114 in an imager HOT are arrayed when viewing
them from the incident light side. FIG. 43A and
FIG. 43B are cross-sectional views taken along lines
VII-VII' and VIII-VIII' of the imager HOT of FIG. 41,
respectively.
The imager HOT has a structure in which the
imager 110 of the llth embodiment further includes a
compensating filter 114Blk. The compensating filter
114Blk does not transmit visible light, and transmits
light in an infrared range to extract an infrared ray.
For convenience, a light receiving element receiving
light via the compensating filter 114Blk is called a
black light receiving element 112Blk.
The black light receiving element 112Blk sends an
electric signal obtained from the received light to a
red operating unit 121R.
A pigment mixing C.I. Pigment Red 254, C.I.
Pigment Yellow 139 and C.I. Pigment Violet 23 is usable
as the color material of the compensating filter
114Blk.
A set of transparent, yellow, red and compensating
filters 114W, 114Y, 114R and 114Blk corresponds to one
pixel. When these transparent, yellow, red and
compensating filters 114W, 114Y, 114R and 114Blk are
expressed as W, Y, R' and Blk, a color filter 114
having an arrayed state shown in FIG. 42 is formed.
The red operating unit 121R receives electric
signals from red and black light receiving elements
112R and 112Blk. By doing so, a compensated red light
observed data value is calculated based on each
intensity value of light received via red and
compensating filters 114R and 114Blk.
With the foregoing configuration, the intensity
values of lights obtained from incident, yellow and red
light receiving elements 112W, 112Y and 112R are each
set as Dw, Dy, Dr and Dblk. Further, blue, green and
compensated red light observed data values are set as
Db, dg and HDr. By doing so, the following
equations (5) to (7) are established.
Db = Dw - Dy ... (5)
Dg = Dy - Dr ... (6)
HDr = Dr - Dblk ... (7)
The imager HOT of the 13th embodiment includes
the compensating filter 114Blk; therefore, a red
observed data value removing an influence of infrared
ray is obtained. By doing so, light colors close to
those of human visual sensitivity are obtained. Thus,
it is possible to provide an imaging device that is
excellent in color balance and color reproducibility.
The imaging device of the present invention formed
with the compensating filter 114Blk has an effect of
removing an influence of ultraviolet rays. In addition
to the effect, it is possible to produce a small-sized
imaging device having high sensitivity and excellent
color reproducibility as compared with the imaging
device including an infrared cut filter.
According to the 13th embodiment, as shown in
FIG. 44, the compensating filter 114Blk may be formed
by optically overlapping the violet color filter 114V
and red filter 114R. The violet filter 114V is formed
of C.I. Pigment violet 23, for example.
(Compensating filter)
The following is a supplementary explanation about
the compensating filter 114Blk.
Solid-state imaging devices, such as a CCD and
CMOS, have high sensitivity in a range outside that of
the range of human vision (e.g., 400 nm to 700 nm). A
wavelength range on the long-wavelength side from the
visual light wavelength range is hereinafter called
"infrared range". For example, a high sensitivity
exists in a wavelength range from 700 nm to 1100 nm. A
normal organic color filter has no function of cutting
light (infrared ray) in the infrared range. For this
reason, light outside the range of human vision (e.g.,
long wavelength side from 700 nm) is incident on the
light receiving element. Thus, there may be a
difference between the color of the observed object
obtained by the imaging device and the color that a
human actually sees.
FIG. 45 shows the relationship between the
wavelength and transmittance as regards the sensitivity
of human vision, sensitivity of a light receiving
element (SPD sensitivity) and ideal infrared cut
filter. In FIG. 45, if the infrared cut filter cuts
the incident light belong to the slanted wavelength
range, a color close to that perceived by human vision
is reproducible. The infrared cut filter has two
kinds, that is, a reflection type and an absorption
type. FIG. 46 shows the relationship between
wavelength and transmittance in reflection type and
absorption type infrared cut filters.
However, if the infrared ray is cut using an
infrared cut filter, the following problem arises.
First, it is difficult to reduce the size of the
imaging device. For example, Jpn. Pat. Appln. KOKAI
Publications No. 2000-19322 and 63-73204 have proposed
a technique of incorporating an infrared cut filter
into an optical system of the imaging device. However,
according to the foregoing technique, the infrared cut
filter is inserted to cover light receiving elements
such as a CMOS or CCD. Thus, the infrared cut filter
is thick; for this reason, it is difficult to reduce
the size of an imaging device of the optical system.
For example the absorption type infrared cut filter has
a thickness of about 1 to 3 mm.
Moreover, there is a problem that it is difficult
to reduce the manufacturing cost. Specifically, if the
color filter is used as a camera component, the process
of incorporating the infrared cut filter into a lens
system is required. Thus, it is difficult to reduce
the manufacturing cost.
The foregoing problem is solved in the following
manner. Namely, an influence of an infrared ray is
removed through use of a compensating filter.
There exists an imaging device that includes three
primary color filters (R, G, B) or complementary color
filters (C, M, Y). The foregoing imaging device has a
problem that sensitivity is reduced if the infrared cut
filter is used. This is because an infrared ray is cut
via all light receiving elements in the imaging device
using the infrared cut filter. Thus, the infrared cut
filter absorbs light of a visual wavelength range from
550 nm to 700 ran. As a result, there is a problem that
sensitivity is reduced in an imaging that has green and
red color filters.
The forgoing problem is solved in the following
manner. Namely, transparent, yellow and red color
filters 114W, 114Y and 114R are used, and further, a
compensating filter 114Blk is used. Specifically,
blue, green red light observed data values are obtained
and reproduced based on the intensity values of light
obtained via transparent, yellow, red and compensating
filters 114W, 114Y, 114R and 114Blk. Therefore, the
three primary colors are reproducible without reducing
the sensitivity. The compensating filter 114Blk is
further used, so that an influence of infrared rays is
only removed from red light observed data value.
(Example 1)
The method of manufacturing the solid-state
imaging device according to an example 1 of the 13th
embodiment will be hereinafter described.
First, a semiconductor substrate 111 is formed
with light receiving elements 112, light shield film
and passivation. A thermosetting acrylic resin
containing coumarin dye at a dye concentration 5% is
applied using spin coating. Thereafter, a heat
treatment is carried out to harden the resin and to
form a film. By doing so, a planarization layer 113
formed of transparent resin is formed. In FIG. 47, al
shows the spectral characteristic of the planarization
layer 113 after being hardened. For comparison, a2 and
a3 show each spectral characteristic when containing
coumarin dye at dye concentrations of 1% and 10%.
Yellow, red and compensating filters 114Y, 114R
and 114Blk are individually formed via three-time
photolithography processes. The pixel pitch is
2.5 jum. The arrayed state of each filter is the same
as shown in FIG. 42.
The C.I. Pigment Yellow 139 is used as the color
material of a color resist (yellow resin layer YL) for
forming the yellow filter 114Y. Further, according to
the composition, cyclohexanone, organic solvent such as
PGMEA, polymer vanish, monomer and initiator are added
to a photosensitive acrylic resin.
C.I. Pigment Red 177, C.I. Pigment Red 48:1 and
C.I. Pigment Yellow 139 are used as the color material
of a color resist for forming the red filter 114R. The
remaining composition is the same as that of the yellow
filter 114Y.
C.I. Pigment Red 254, C.I. Pigment Yellow 139 and
C.I. Pigment Violet 23 are used as the color material
of a color resist for forming the compensating filter
114B1R. The remaining composition is the same as that
of the yellow filter 114Y.
Then, the same acrylic resin solution as the
planarization layer 113 I applied on the color filter
114 to have a film thickness of 0.8 //m. Thereafter,
the resultant is heated at 200°C for six minutes, and
then, hardened to form a film, and thereby, a lens
layer LL is formed. A phenol resin is applied to a
film thickness of 1.0 JJL m to form a phenol resin layer
116. The phenol resin layer 116 has an etching control
function and a thermal reflow control function. An
acrylic resin (lens shape material) having alkali
soluble, photosensitive and thermal reflow is further
applied to form a photosensitive resin layer 117.
The photosensitive resin layer 117 (lens shape
material) is formed into a rectangular pattern via the
photolithography process using a developer. Then, the
resin layer 117 is reflowed via a heat treatment of
200°C. By doing so, a rounded semi-spherical lens
material 7 M is formed. If reflow is correctly
conducted, a height of 0.45 //m, one side of 0.15 /urn,
and gap of 0.35 /zm between lens shape materials are
given, thereby forming a smooth semi-spherical lens
material 117M.
Finally, etching is carried out in a dry etching
system using a mixed gas of chlorofluorocarbon gases
C3F8 ad C4F8 and using the lens shape material 117M as
a mask. By doing so, no gap between lenses is
substantially given, and then, a micro lens 115 having
a narrow gap between lenses is formed.
The etching rate of the acrylic resin used in the
13th embodiment is 1.2 times faster than that of the
resin for forming the lens material 117M. The frontend
resin of the lens material 117M, that is,
photosensitive resin layer 117 serves-to form the micro
lens 115 having no surface roughness and narrow gap.
Therefore, the numerical aperture of the micro lens 115
is improved. The etching rate of the resin forming the
lens material 117M is the same as that of
photosensitive resin 117 and lens layer LL. By doing
so, the shape of the micro lens 115 is formed to have
approximately the same size and shape as the lens
material 117M.
In the imaging device thus configured,
transparent, yellow, red and compensating filters 114W,
114Y, 114R and 114Blk have the spectral characteristic
shown in FIG. 48. In FIG. 48, bl, b2, b3 and b4 show
the spectral characteristic of transparent, yellow, red
and compensating filters 114W, 114Y, 114R and 114Blk,
respectively. As seen from FIG. 48, the spectral
characteristic curve of each filter has the following
features. Namely, the transmittance is low in a shortwavelength
range, and the rise of the transmittance
exists there. Moreover, the transmittance becomes high
in a long-wavelength range. Thus, a spectral
characteristic curve with an approximately S-shape is
obtained.
The foregoing color operations referred to by the
equations (5) to (7) are performed. By doing so, it is
possible for an imaging device to include virtual blue,
green and red filters having the spectral
characteristic shown in FIG. 49. In FIG. 49, cl, c2
and c3 show the spectral characteristic of virtual
blue, green and red filters, respectively.
The spectral measurement is carried out in the
following manner.
First, the thickness of each color filter 114 on
the light receiving element 112 and that of transparent
layer (planarization layer 113 and lens layer LL) are
measured. The thickness of the transparent resin is
measured in the following manner. Specifically, a film
is formed on a Si substrate, and thereafter, the film
thickness is measured using a contact film thickness
meter (Dektak IIA made by Sloan Company).
A transparent resin and color filter 114 having
the same thickness as measured are formed on a glass
substrate. Then, spectral characteristic is measured
using a spectrophotometer U-3400 (made by Hitachi
Seisakusho). In this case, the glass substrate only
(having no color filter and transparent resin) is used
as a reference. The spectral characteristic of a color
filter and transparent resin only is measured.
Moreover, the transmittance value using a transparent
glass having a refraction of 1.5 is taken as 100%.
(Example 2)
A thermosetting acrylic resin solution containing
benzotriazole dye at a dye concentration at 5% is
applied. Then, the solution is coated by spin coating
to form planarization layer 113, transparent filter
114W and lens layer LL. An imaging device is
manufactured in the same manner as the Example 1 except
for the foregoing condition.
In FIG. 50, dl shows the spectral characteristic
of the transparent resin containing benzotriazole dye
at a dye concentration at 5%. For comparison, d2 and
d3 show each spectral characteristics of the
transparent resins containing benzotriazole dye at dye
concentrations of 1% and at 10%.
In the imaging device made in the foregoing
manner, el, e2, e3 and e4 of FIG. 51, show the spectral
characteristic of transparent, yellow, red and
compensating filters 114W, 114Y, 114R and 114Blk,
respectively.
The color operations referred to by the foregoing
equations (5) to (7) are performed. By doing so, it is
possible to obtain an imaging device having virtual
blue, green and red filters having the spectral
characteristic shown in FIG. 52. In FIG. 52, fl, f2
and f3 show the spectral characteristic of virtual
blue, green and red filters, respectively.
As described above, the spectral characteristic of
the transparent resin layer (planarization layer 113,
transparent filter 114W, lens layer LL) is changed. By
doing so, the transparent filter 114W has a
transrnittance of 50% on a short-wavelength side is set.
Thus, it is possible to select the color characteristic
(color close to actual visual sensitivity, the same
color as an organic pigment).
Incidentally, the following is given as the
secondary effect. Namely, it is possible to prevent
halation occurring due to reflection of the pattern
exposure light when forming color filters via the
photolithography process. Therefore, a color filter
having a high resolution is formed.
According to Example 2, an influence of infrared
rays is removed by the operation using the compensating
filter 114Blk. Therefore, no infrared cut filter is
required.
An imaging device using no compensating filter
114Blk is manufactured by the same method without
considering an influence of infrared rays in view of
simplifying the process of manufacturing the imaging
device. In this case, the infrared cut filter must be
used; however, the following merit is given. In
photolithography including pattern exposure and
development, two-time coloring of a color resist for
forming yellow and red filters 114Y and 114R is carried
out. This serves to reduce the number of processes.
Moreover, the transparent filter and micro lens are
integrated, and thereby, a process is further omitted.
On the contrary, three-time coloring is required in
order to produce blue, green and red color filters used
for a normal imaging device.
<14th embodiment>
The 14th embodiment relates to an imaging device
201, which includes at lest two filters. One is a
first filter having an anti-transmission characteristic
with respect to light on a short wavelength side from a
first wavelength and having a transmission
characteristic with respect to light on a long
wavelength side from the first wavelength. Another is
a second filter having an anti-transmission
characteristic with respect to light on a short
wavelength side from a second wavelength on the long
wavelength side from the first wavelength and having a
transmission characteristic with respect to light on a
long wavelength side from the second wavelength.
According to the 14th embodiment, each filter has an
anti-transmission characteristic in a short wavelength
range while having a transmission characteristic in a
long wavelength range. Preferably, an approximately
S-shaped transmittance curve is obtained as the
spectral characteristic.
Light incident via the first and second filters is
received by first and second light receiving elements,
and then, converted into an electric signal.
Specifically, the imaging device 201 includes
filters Fl to F7 . These filters Fl to F7 have a first
wavelength range of a transmittance of 10% or less in a
wavelength range from 350 nm to 750 nm. Moreover,
filters Fl to F7 have a wavelength range of
transmittance of 90% or more in a wavelength range from
450 nm to 1100 nm, which is a long wavelength range
from the first wavelength range. The first and second
filters are named as such to show that they are
related. Filters Fl to F7 are used as the first and
secona filters.
Filters Fl to F7 are used for showing white
(transparent), green blue, yellow green light, yellow,
orange, red and infrared (for convenience, black)
lights. The spectral characteristic of filters Fl to
F7 is shown as LI to L7 in FIG. 53.
According to the 14th embodiment, filters Fl, F4
and F6 are equivalent to transparent, yellow and red
filters 2W, 2Y and 2R, respectively.
The following is an explanation about the method
of calculating observed data used for reproducing
incident light received via filters Fl to F7 .
When light is incident on the imaging device 201,
the corresponding first and second light receiving
elements receive the incident light via any of filters
Fl to F7, that is, first and second filters. The
received light is converted into an electric signal.
FIG. 54 shows the concept of filters. A
wavelength data value DC corresponding to the
difference between wavelength ranges of light received
by the first and second filters. The wavelength data
value DC is calculated from a data value Dl of light
received by the first filter and a data value D2 of
light received by the second filter.
In other words, the first and second filters form
a virtual color filter of the color corresponding to
the difference between wavelength ranges.
For example, a blue observed data value Db is
obtained based on filter Fl (white) and filter F4
(yellow). A green observed data value Dg is obtained
based on filter F4 (yellow) and filter F6 (red). A red
data value HDr receiving no influence of infrared ray
is obtained from filters F6 (red) and F7 (black).
In the manner descried above, three primary color
light data values are obtained, and thus, the received
incident light is reproduced.
For example, subtraction of the filter F2
(greenish blue) and the filter F3 (yellow green) is
made, and thereby, a green blue (greenish blue) data
value is obtained. Subtraction of the filter F3
(yellow green) and the filter F4 (yellow) is made, and
thereby, a yellow green data value is obtained.
Subtraction of the filter F4 (yellow) and the filter F5
(orange) is made, and thereby, a yellow data value is
obtained. Subtraction of the filter F5 (orange) and
the filter F6 (red) is made, and thereby, an orange
data value is obtained.
In brief, according to the foregoing method, two
of filters Fl to F7 forming the first and second
filters are used, and thereby, the received incident
light is reproduced, and in addition, a finer color is
extracted.
According to the 14th embodiment, filters Fl to F7
are given as an example. However, the present
invention is not limited to the above. Any color
filters may be used so long as they have the foregoing
characteristic. Namely, color filters that have the
first wavelength range showing a transmittance of 10%
or less in a wavelength range from 350 nm to 750 ran are
used. Moreover, the color filters have a wavelength
range of transmittance of 90% or more in a wavelength
range from 450 nm to 1100 nm, which is a long
wavelength range from the first wavelength range.
The imaging device of the 14th embodiment is
manufactured in the following manner. Namely, of color
filters, the color filter having a high color material
content is formed using dry etching. Color filters
having a low content, except for filters having a high
content, are formed using the photolithography process.
<15th embodiment>
According to the 15th embodiment, the
transmittance of several filters, that is, color,
compensating and transparent filters each rises
(increases) in the different wavelength range.
FIG. 55 is a front view showing an imaging device
according to a 15th embodiment. In FIG. 55, there is
shown a state that filters Fl to F7 of an imaging
device 210 are arrayed when viewing them from the light
incident side. The filters Fl to F7 includes color,
compensating and transparent filters.
Light receiving elements (photo-electrical
converting element) HI to H7 receive incident light via
filters Fl to F7, respectively, and then, output
observed data values El to E7 to an operator 62.
The operator 220 executes subtraction based on
observed data values observed via arbitrary two filters
of observed data values El to E7 of several light
receiving elements HI to H7 observed via filters Fl to
F7 . Then, the operator 220 calculates an observed data
value of light in the wavelength range corresponding to
the pair of the foregoing arbitrary two filters, and
thereafter, outputs the calculated observed data value.
FIG. 56 is a graph showing the relationship
between light wavelength and transmittance of filters
Fl to F7 included in the imaging device 210.
Filters Fl to F7 included in the imaging device
210 have the following features. Specifically, filters
Fl to F7 each have an anti-transmission characteristic
of light on a short-wavelength side from wavelengths
WLl to WL7 where the self-transmittance rises.
Moreover, filters Fl to F7 each have a transmission
characteristic of light on a long-wavelength side from
wavelengths WLl to WL7 where the self-transmittance
rises.
In the imaging device 210, light rays incident via
filters I to F7 are each observed by light receiving
elements (photo-electrical converting elements) HI to
H7. The operator 220 inputs observed data values El to
E7 of light receiving elements HI to H7.
Filters Fl to F7 each have the following spectra;
curve. The transmittance is low in a short-wavelength
range from a portion where the self-transmittance rises
while being high in a long-wavelength range. Thus, the
spectral curve is formed into an approximate S shape.
Filters Fl to Fl each have the rise of transmittance in
a different wavelength.
According to the 15th embodiment, the filter Fl is
a transparent filter (e.g., colorless transparent
filter).
The filter F4 is a yellow color filter used for
extracting a yellow component of light.
The filter F6 is a red color filter used for
extracting a red component of light.
The filter F7 is a compensating filter having an
anti-transmission characteristic of light in a visual
light wavelength range and a transmission
characteristic in a long-wavelength range from the
visual light wavelength range.
Considering the characteristic between light
transmittance and wavelength, the wavelength WL2 where
the transmittance of the filter F2 rises exists between
wavelengths WL1 and WL3. The WL1 is a wavelength of a
portion where the transmittance of the filter
(transparent filter) Fl rises. The WL3 is a wavelength
of a portion where the transmittance of the filter F3
rises. For example, the wavelength WL2 where the
transmittance of the filter F2 rises divides a
wavelength range between WL1 and WL3 into two. Of
course, the WL1 is a wavelength of a portion where the
transmittance of the filter (transparent filter) Fl
rises. The WL3 is a wavelength of a portion where the
transmittance of the filter F3 rises.
Likewise, considering the characteristic between
light transmittance and wavelength, the wavelength WL4
where the transmittance of the filter (yellow filter)
F4 rises exists between wavelengths WL3 and WL6. The
WL3 is a wavelength of a portion where the
transmittance of the filter F3 rises. The WL6 is a
wavelength of a portion where the transmittance of the
filter (red filter) F6 rises.
Likewise, the wavelength WL5 where the
transmittance of the filter F5 rises exists between
wavelengths WL4 and WL6. The WL4 is a wavelength of a
portion where the transmittance of the filter F4 rises.
The WL6 is a wavelength of a portion where the
transmittance of the filter (red filter) F6 rises.
Considering the characteristic between light
transmittance and wavelength, the wavelength WL 4 where
the transmittance of the filter F4 (yellow filter) rise
increases on a short-wavelength side from the
wavelength WL5. Of course, the WL5 is a wavelength of
a portion where the transmittance of the filter F5
rises. For example, wavelengths WL4 and WL5 divide a
wavelength range between WL3 and WL6 into three. Of
course?, the WL3 is a wavelength of a portion where the
transmittance of the filter F3 rises. The WL6 is a
wavelength of a portion where the transmittance of the
filter (red filter) F6 rises.
As described above, the operator 220 executes
subtraction based on observed data values observed via
arbitrary two filters of observed data values El to E7
of light receiving elements HI to H7 observed via
filters Fl to F7. Then, the operator 220 calculates an
observed data value of light in the wavelength range
corresponding to the pair of the foregoing arbitrary
two filters.
For example, the operator 220 subtracts the
observed data value E4 observed via the filter (yellow
filter) F4 from the observed data value El observed via
the filter (transparent filter) Fl. Then, the operator
220 outputs a blue observed data value Gl.
The operator 220 subtracts the observed data value
E6 observed via the filter (red filter) F6 from the
observed data value E4 observed via the filter (yellow
filter) F4. Then, the operator 220 outputs a green
observed data value G2.
The operator 62 subtracts the observed data value
E7 via the compensating filter F7 from the observed
data value E6 observed via the filter (red filter) F6.
Then, the operator outputs a red observed data value G3
removing an influence (component) of infrared ray.
The operator 220 subtracts the observed data value
E3 via the filter F3 from the observed data value E2
via the filter F2. Then, the operator outputs a
greenish blue observed data value G4.
The operator 220 subtracts the observed data value
E4 observed via the filter (yellow filter) F4 from the
observed data value E3 via the filter F3. Then, the
operator outputs a yellow green observed data value G5.
The operator 220 subtracts the observed data value
E5 observed via the filter F5 from the observed data
value E4 observed via the filter (yellow filter) F4.
Then, the operator outputs a yellow observed data value
G6.
The operator 220 subtracts the observed data value
E6 observed via the filter (red filter) F6 from the
observed data value E5 observed via the filter F5.
Then, the operator outputs an orange observed data
value G7 .
Preferably, filters Fl to F7 each have a
transmittance of 90% or more when the wavelength of
light is in a long-wavelength range from 750 nm. This
is due to cutting of the infrared light component so as
to highly accurately observe the intensity of the light
component that exists within the human range of vision.
There is the case where light receiving elements
(photo-electrical converting elements) HI to H7 have
different sensitivities in a short-wavelength range,
which is due to different manufacturers.
If an ultraviolet light absorbing agent is added
to the filter (transparent filter) Fl, preferably, the
light wavelength when the transmittance of the filter
Fl becomes 50% is in a range from 350 nm to 400 nm
(ultraviolet light range). Therefore, it is preferable
that the light wavelength when the transmittance of the
filters Fl to F7 becomes 50% is 350 nm or more.
On the other hand, if no ultraviolet light
absorbing agent is added to the filter (transparent
filter) Fl, the following conditions are preferably
satisfied. Namely, the light wavelength when the
transmittance of other filters F2 to F7 except for
filter Fl becomes 50% is 400 nm or more. Preferably,
the transmittance of the filter Fl becomes 90% or more
in the light wavelength of 400 nm or more.
By doing so, it is possible to reduce an influence
of the difference in the sensitivity between
manufacturing makers of light receiving elements HI to
H7. Thus, the blue observed data value is obtained
according to a fixed condition.
The human sense of vision relates to light in a
wavelength range of 400 nm to 700 nm; therefore, the
sensitivity of the red range must be controlled. In
order to obtain a proper red observed data value, the
light wavelength when the transmittance becomes 50% is
preferably set as 750 nm or less for filters Fl to F7.
From the result of the foregoing study, the
following requirements must be satisfied if an
ultraviolet light absorbing agent is added to the
filter (transparent filter) Fl. Preferably, filters Fl
to F7 each have a light transmittance of 50% in a
wavelength rage from 350 nm, to 700 nm. In addition,
these filters Fl to F7 each have a light transmittance
of 90% or more on a long-wavelength side from the light
wavelength 750 nm.
Moreover, the following requirements must be
satisfied if no ultraviolet light absorbing agent is
added to the filter (transparent filter) Fl.
Preferably, filters F2 to F7 except for filter Fl each
have a light transmittance of 50% in a wavelength range
from 450 nm, to 700 nm. In addition, these filters F2
to F7 each have a light transmittance of 90% or more on
a long-wavelength side from the light wavelength of
750 nm. The filter Fl has a light transmittance of 90%
or more on a long-wavelength side from the light
wavelength of 400 nm.
According to the 15th embodiment, filters Fl to F7
may be provided with a micro lens at the light incident
side. The filter Fl and the micro lens are formed of
the same transparent resin.
As described above, filters (e.g., Fl to F7)
having the spectral characteristic that the
transmittance suddenly increases in different
wavelength ranges are properly selected. The selected
filter is placed on the light receiving element, and an
operation is made based on observed data values
obtained from the light receiving elements. By doing
so, other observed data values having fine color
component are obtained in addition to red (R), green
(G) and blue (B).
The compensating filter according the foregoing
each embodiment is formed by mixing red pigment and
violet pigment. By doing so, the compensating filter
is formed to have the transmittance of 50% in the
wavelength of about 660 nm.
Moreover, the compensating filter is formed by
mixing a red pigment and cyan pigment. By doing so,
the compensating filter is formed to have the
transmittance of 50% in the wavelength of about 740 nm.
Industrial Applicability
According to the present invention, there is
provided an imaging device, which is excellent in color
balance and color reproducibility.

C L A I M S
1. An imaging device characterized by comprising:
a filter used for extracting a specified color
component of an incident light; and
a light receiving element observing the incident
light via the filter,
the filter including:
a transparent filter;
a yellow filter used for extracting a yellow
component; and
a red filter used for extracting a red component.
2. The imaging device according to claim 1,
characterized in that the light receiving element
further includes:
*
an incident light receiving element observing the
incident light via the transparent filter;
a yellow light receiving element observing the
incident light via the yellow filter;
a red light receiving element observing the
incident light via the red filter;
operating means for subtracting an observed result
observed by the yellow light receiving element from an
observed result observed by the incident light
receiving element to calculate a blue observed result;
and
operating means for subtracting an observed result
observed by the red light receiving element from an
observed result observed by the yellow light receiving
element to calculate a green observed result.
3. The imaging device according to claim 1 or 2,
characterized by further comprising:
a transparent planarization layer forming the
transparent filter to cover the yellow and red filters.
4. The imaging device according to claim 3,
characterized by further comprising:
a micro lens formed of the transparent
planarization layer, and collecting light to the light
receiving elements.
5. The imaging device according to any one of
claims 1 to 4, characterized in that the transparent
filter absorbs ultraviolet ray in a short-wavelength
range from 400 nm.
6. The imaging device according to any one of
claims 1 to 5, characterized in that the transparent
filter has a spectral characteristic of showing a light
transmittance of 50% with respect to light having any
of a wavelength range from 365 nm to 420 nm and having
a light transmittance of 90% or more in a wavelength of
450 nm.
7. The imaging device according to any one of
claims 1 to 6, characterized in that the transparent
filter has a spectral characteristic of showing a light
transmittance of 50% with respect to light having any
of a wavelength range from 390 nm to 420 nm and having
a light transmittance of 90% or more in a wavelength of
450 nm.
8. The imaging device according to any one of
claims 1 to 7, characterized in that the transparent
filter, the yellow filter and the red filter are
adjacently arrayed like a mesh to form one unit of
color separation, and
the number of pixels of the yellow filter is equal
to the total number of pixels of the transparent filter
and the red filter.
9. The imaging device according to any one of
claims 1 to 7, characterized in that the filter further
includes a compensating filter having an antitransmission
characteristic in a visible light
wavelength range and a transmission characteristic on a
long-wavelength side from the visible light wavelength
range.
10. The imaging device according to claim 9,
wherein the light receiving element further includes a
compensating light receiving element observing the
incident light via the compensating filter, and
the device further includes operating means for
subtracting an observed result observed by the
compensating light receiving element from the observed
result observed by the red light receiving element.
11. The imaging device according to claim 9 or
10, wherein the compensating filter has approximately
the same level transmission characteristic as the red
filter on a long-wavelength side from a visible light
wavelength range.
12. The imaging device according to any one of
claims 8 to 11, characterized in that the difference in
light transmittance between the compensating filter and
the red filter is in a range of about 5% or less in a
light wavelength range from 400 nm to 550 nm and on a
long-wavelength range from 750 nm, and
the compensating filter has a light transmittance
of 50% in a light wavelength range from 630 nm to
750 nm.
13. The imaging device according to any one of
claims 8 to 12, characterized in that the compensating
filter is formed by optically overlapping several
colors.
14. The imaging device according to claim 13,
characterized in that the compensating filter is formed
by optically overlapping two colors, that is, violet
and red.
15. The imaging device according to claim 13,
characterized in that the compensating filter is formed
by optically overlapping two colors, that is, cyan and
red.
16. The imaging device according to any one of
claims 13 to 15, characterized in that the compensating
filter is formed by stacking several filters.
17. The imaging device according to any one of
claims 8 to 16, characterized in that the transparent
filter, the yellow filter, the red filter and the
compensating filter are adjacently arrayed like a mesh
to form one unit of color separation.
18. The imaging device according to any one of
claims 8 to 17, characterized in that the compensating
filter has a transmittance of 5% or less with respect
to light having a wavelength range from 400 nm to
550 nm, and has a transmittance of 50% with respect to
light having any of a wavelength range from 620 nm to
690 nm, and further, has a transmittance of 70% or more
with respect to light having a wavelength of 700 nm.
19. The imaging device according to any one of
15 claims 8 to 18, characterized in that the compensating
filter is formed of a colored resin compound containing
at least pigments of C.I. Pigment Violet 23 and, C.I.
Pigment Yellow 139.
20. The imaging device according to any one of
claims 8 to 19, characterized in that the compensating
filter is formed of a colored resin compound containing
at least pigments of C.I. Pigment Violet 23, C.I.
Pigment Yellow 139 and C.I. Pigment Red 254.
21. The imaging device according to any one of
claims 1 to 20, characterized by further comprising:
a substrate provided with the light receiving
element,
the substrate being provided with a light shield
film for preventing reflection and transmission of
light except the incident light, which is incident on
the light receiving element, the light shield film
being provided on an area on the substrate other than
an area where the incident light is incident on the
light receiving element.
22. The imaging device according to claim 21,
characterized in that the light shield film has an
ultraviolet absorbing function.
23. The imaging device according to claim 21 or
22, characterized in that the light shield film has an
infrared absorbing function.
24. The imaging device according to any one of
claims 21 to 23, characterized in that the light shield
film is stacked with a film having at least one of a
ultraviolet absorbing function and a near-infrared
absorbing function.
25. An imaging device including several photoelectric
converting elements receiving an incident
light via several filters, characterized by comprising:
a first filter being one of said several filters,
and being an arbitrary filter included in said several
filters, and further, having an anti-transmission
characteristic with respect to light on a shortwavelength
side from a first wavelength and a
transmission characteristic with respect to light on a
long-wavelength side from the first wavelength;
a second filter being another filter different
from the first filter of said several filters, and
having an anti-transmission characteristic with respect
to light on a short-wavelength side from a second
wavelength, which is a long-wavelength side from the
first wavelength, and a transmission characteristic
with respect to light on a long-wavelength side from
the second wavelength;
a first photo-electric converting element being
one of said several photo-electric converting elements,
and receiving an incident light via the first filter;
a second photo-electric converting element being
another photo-electric converting element different
from the first photo-electric converting element, and
receiving the incident light via the second filter; and
operating means for subtracting an observed data
value of light observed by the second photo-electric
converting element from an observed data value of light
observed by the first photo-electric converting element
to calculate an observed data value of light of a color
corresponding to the difference in a wavelength range
between the first and second filters.
26. The imaging device according to claim 25,
characterized in that the first wavelength is any of a
wavelength range 350 nm to 750 nm.
27. The imaging device according to claim 25 or
26, characterized in that the first filter is a
transparent filter having a light transmittance of 90%
or more on a long-wavelength side from light wavelength
of 400 nm,
of said several filters, a filter having a
characteristic such that the light transmittance rises
at the most long-wavelength side is a compensating
filter having an anti-transmission characteristic in a
visible light wavelength range and having transmission
characteristic on a long-wavelength side from the
visible light wavelength range,
other filters except the compensating filter each
have a light transmittance of 50% in a light wavelength
range from 350 nm to 750 nm, and each have a light
transmittance of 90% or more on a long-wavelength side
from a light wavelength of about 750 nm.
28. An imaging device characterized by
comprising:
an imaging element detecting an intensity value of
light having a specified wavelength range of an
incident light; and
operating means for reproducing the incident light
based on the intensity value of light detected by the
imaging element,
the imaging element including:
a semiconductor substrate;
a photo-electric converting element formed on the
semiconductor substrate, and receiving an incident
light;
a transparent filter formed on the photo-electric
converting element, and transmitting the incident
light;
a red filter formed on the photo-electric
converting element, and used for extracting a red
component of the incident light;
a yellow filter formed on the photo-electric
converting element, and used for extracting a yellow
component of the incident light;
a transparent resin layer formed to cover the
color filters; and
a micro lens formed on the color filters,
the operating means including:
means for subtracting an intensity value of the
incident light received via the yellow filter from an
intensity value of the incident light received via the
transparent filter to calculate a blue component value
of the incident light; and
means for subtracting an intensity value of the
incident light received via the red filter from an
intensity value of the incident light received via the
yellow filter to calculate a green component value of
the incident light.
29. The imaging device according to claim 28,
characterized in that the imaging element further
includes a compensating filter used for extracting an
infrared component of the incident light, and
the operating means further includes means for
subtracting an intensity value of the incident light
received via the compensating filter from an intensity
value of the incident light received via the red filter
to calculate a red component value of the incident
light.