[Designation of Document] SPECIFICATION
[Title of the Invention) OPTICAL MEASUREMENT DEVICE AND
OPTICAL MEASUREMENT METHOD
[Technical Field]
[0001]
The present invention relates to an optical measurement
device, or the like, for measuring an optical rotation angle.
[Background Art]
[0002]
It is possible to know the composition of a material
without making direct contact by measuring light which has
passed through the material. For example, it is possible to
estimate concentration of a material by measuring an angle of
optical rotation. Optical rotation refers to a property in
which, when linearly polarized light passes through an
optically active substance such as glucose, for example, a
plane of polarization thereof rotates.
[0003]
As a technology using the property of optical rotation,
a technology is disclosed in Patent Reference 1, for example:
in which linearly polarized light which has passed through a
test object is orthogonally separated, polarized components
thereof are received by two respective light receiving
elements, and an angle of optical rotation is measured from
a difference between output levels of both the light receiving
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[Related Art Documents)
[Patent Documents]
[0004]
[Patent Reference 1]
International Publication WO
99/30132
[Disclosure of the Invention]
[Problem that the Invention is to Solve]
[0005]
In the technology of measuring an angle of optical
rotation which is disclosed in Patent Reference 1, the angle
of optical rotation is measured from a difference between
output levels of the two light receiving elements. However,
there is a problem in this measuring method. As light which
is radiated to the test object, laser light is generally used,
however, there is a c'ase in which an output fluctuation, which
is referred to as a so-called returrt light noise, occurs in
a laser device such as a semiconductor laser which outputs laser
light. It is a phenomenon in which oscillation of a laser
becomes unstable since a part of light which is output from
the laser device returns to the laser device again by being
reflected. In this case, a so-called fluctuation in amount
of light occurs in which amount of light of transmitted light
which has passed through the test object fluctuates.
[0006]
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••
In addition. when a test object having a plurality of
components whose absorbance is different from each other is
measured, each component is not necessarily distributed
equally in the test object. That is, the fluctuation in amount
of light of transmitted light which passes through the test
object easily occurs, since the absorbance becomes different
depending o~ a mixed state of each component, a radiated
position of the laser, the passage of time, or the like when
performing the measuring.
(0007]
When such a fluctuation in amount of light occurs, it
is not possible to guarantee that the angle of optical rotation,
which is simply calculated from a difference between received
light levels in the light receiving elements, is a correct
measurement value. This is because, when the fluctuation in
amount of light occurs, the received light levels in the light
receiving elements are totally changed, and the difference
between the received light levels is changed. For example,
though it is an extreme example, when amount of light of the
transmitted light is reduced to 1/2, a difference between
received light levels is reduced to 1/2, since the light
receiving level in the light receiving element is reduced to
1/2. Consequently, the method of measuring an angle of optical
·rotation in the related art determined from the difference in
received light levels, is unable to provide the correct angle
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of optical rotation.
[0008]
The invention has been made in consideration of the above
described problem; and an object thereof is to propose a new
method in which an angle of optical rotation can be correctly
measured.
[Means for Solving the Problem]
[0009]
A first aspect for solving the above described problem
is directed to an optical measurement device which includes
an orthogonal separation unit which orthogonally separates
transmitted light in which linearly polarized light has passed
through a test object; at least two light receiving units which
receive light which is orthogonally separated in the
orthogonal separation unit; and an angle of optical rotation
calculation unit which includes a transmitted amount of light
determination unit which determines amount of light of the
transmitted light, or amount of light of a predetermined
proportion of the amount of light, and calculates an angle of
optical rotation after normalizing a difference between the
received light levels which are received in the light receiving
unit using the amount of light which is determined in the
transmitted amount of light determination unit.
[0010]
In addition, as another aspect, the invention may be
5
••
configured as an optical measurement method which includes
orthogonally separating transmitted light in which linearly
polarized light passes through a test object; receiving the
orthogonally separated light; determining amount of light of
the transmitted light, or amount of light of the predetermined
proportion of the amount of light; and calculating an angle
of optical rotation after normalizing a difference between the
received light levels using the determined amount of light.
[0011]
According to the first aspect or the like, the
transmitted light in which the linearly polarized light passes
through the test object is orthogonally separated, and the
orthogonally separated light is received. In addition, the
amount of light of the transmitted light, or amount of light
of the predetermined proportion of the amount of light. is
determined, and the angle of optical rotation is calculated
after normalizing the difference between the received light
levels in the light receiving unit using the determined light.
By normalizing the difference between the received light
levels, it is possible to correctly calculate the angle of
optical rotation, even in a case in which a fluctuation in the
amount of light of the transmitted light occurs.
[0012]
In addition, as a second aspect, the optical measurement
device according to the first aspect may be configured such
6
..
that the optical measurement device includes the angle of
optical rotation calculation unit which has a differential
amplification unit obtaining a difference between the received
'light levels, and further has an amplification factor setting
unit which variably sets an amplification factor of the
differential amplification unit.
[0013]
According to the second aspect, the difference between
the received light levels is obtained by the differential
amplification unit. The amplification factor of the
differential amplification unit is variably set by the
amplification factor setting unit. For example, by variably
setting the amplification factor based on absorbance of the
test object, and the magnitude of the angle of optical rotation,
it is possible to calculate the angle of optical rotation in
a wide dynamic range.
[0014]
In addition, as a third aspect, the optical measurement
device according to the first or second aspect may be configured
such that the transmitted amount of light determination unit
determines the amount of light using the sum of the received
light levels which are received in the light receiving unit.
[0015]
According to the third aspect, it is possible to simply
determine the amount of light of the transmitted light using
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the sum of the received light levels which are received in the
light receiving unit.
[0016]
In addition, as a fourth aspect, the optical measurement
device according to the first or second aspect may be configured
such that the optical measurement device further includes a
non-polarizing division unit which divides the transmitted
light using the predetermined proportion in a non-polarizing
manner, and a second light receiving unit which receives light
on one side which is divided in the non-polarizing manner are
further included, in which the orthogonal separation unit
orthogonally separates light on the other side which is divided
in the non-polarizing manner, and the transmitted amount of
light determination unit determines amount of light of the
transmitted light of the predetermined rate based on the light
receiving level of the second light receiving unit.
[0017]
According to the fourth aspect, the transmitted light
is divided at the predetermined rate in the non-polarizing
manner by the non-polarizing division unit. In addition, the
light on one side which is divided in the non-polarizing manner
is received in the second light receiving unit. In contrast
to this, the light on the other side which is divided in the
non-polarizing manner is orthogonally divided in the
orthogonal separation unit. In addition, the amount of light
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of the transmitted light of the predetermined rate is
determined based on the light receiving level of the second
light receiving unit. It is possible to determine the amount
of light of the transmitted light of the predetermined rate
by adopting a simple configuration in which the transmitted
light is divided in the non-polarizing manner by the
non-polarizing division unit, and the light on one side is
received in the second light receiving unit.
[Brief Descriptions of Drawings]
[0018]
Fig. 1 is a diagram which illustrates a configuration
example of a first optical measurement device.
Fig. 2 is a table showing a data structure example of
parameter data for control.
Fig. 3 is a flowchart which illustrates a flow of a first
angle of optical rotation measurement processing.
Fig. 4 is a diagram which illustrates a configuration
example of a second optical measurement device.
Fig. 5 is a flowchart which illustrates a flow of a second
angle of optical rotation measurement processing.
[Best Mode for Carrying out the Invention]
[0019]
Hereinafter, examples of preferable embodiments of the
invention will be described with reference to drawings.
However, as a matter of course, embodiments to which the
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invention is applicable are not limited to embodiments
described herein.
[0020]
1. First Embodiment
1-1. Configuration
Fig. 1 is a diagram which illustrates a configuration
example of a first optical measurement device 1A according to
a first embodiment. The first optical measurement device 1A
is mainly configured by including a light source 10, a
polarizing unit 20, an orthogonal separation unit 30, a light
receiving unit 40, a differential amplification unit 50, a
control unit 100, an operation unit 200, a display unit 300,
a sound output unit 400, a communication unit 500, and a storage
unit 600.
[0021]
A test object A is arranged between the polarizing unit
20 and the orthogonal separation unit 30. It is possible to
set the test object A to any sample such as a solid matter or
liquid which includes an optically active substance. In the
embodiment, the test object A is set to a reagent whose main
component is glucose, and a property of optical rotation of
the test object A is estimated by measuring the angle of optical
rotation of the test object A by receiving the transmitted light
which passes through the test object A.
[0022]
10
..
The light source 10 is a laser device which generates
and outputs light. For example 1 the light source is configured
by including a semiconductor laser (laser diode) . The light
source 10 radiates laser light with a phase of a predetermined
wavelength (for example 1 650 nanometer [nm] ) from an end face
which is a half mirror.
[0023]
The polarizing unit 20 is a polarizing element
(polarizer) which converts output light from the light source
10 to linearly polarized light, and is configured by including,
for example, a polarizing optical element such as a polarizing
prism. As the polarizing unit 20, for example, it is possible
to apply a Glan Thompson prism which is a Glan type polarizer.
[0024]
In the orthogonal separation unit 30, the transmitted
light in which the linearly polarized light passed through the
test object A is separated into orthogonal components which
form a predetermined angle of aperture, that is, polarized
components which are different by 90° from each other. As the
orthogonal separation unit 30, for example, it is possible to
apply the Wollaston prism as a type of polarizing optical
element.
[0025]
The light receiving unit 40 is an element which rec:ei ves
light which is orthogonally separated by the orthogonal
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separation unit 30, and is configured by including a light
detector such as a photo diode. The light receiving unit 40
is configured by including at least two light receiving units.
For example, the light receiving unit 40 is configured by
including a P polarized light receiving unit 40A and an S
polarized light receiving unit 40B. In addition, the
polarized components (P component and S component) which are
orthogonally separated by the orthogonal separation unit 30,
and are orthogonal to each other are detected, a voltage·
corresponding
differential
to the amount of light
amplification unit 50
is
by
output to the
performing a
photoelectric conversion. In descriptions below, a voltage
which is subject to the photoelectric conversion in the P
polarized light receiving unit 40A is referred to as a "P
polarization voltage", and a voltage which is subject to the
photoelectric conversion in the S polarized light receiving
unit 40B is referred to as an "S polarization voltage".
[ 002 6]
The differential amplification unit 50 is a calculation
unit which amplifies a difference and the sum of the received
light levels in the light receiving unit 4 0 for detection, and
is configured by including an adder 51, a subtracter 53, a
switch 55, and an amplification circuit 57. Outputs of the
P polarized light receiving unit 40A and S polarized light
receiving unit 40B are subject to an addition and subtracti.on
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in the adder 51 and the subtracter 53, respectively, and are
configured such that any one of the addition result and the
subtraction result is selected in the switch 55, and is
amplified in the amplification circuit 57. Switching of the
switch 55, and the amplification factor of the amplification
circuit 57 are controlled by an instruction signal from the
control unit 100.
[0027]
The control unit 100 performs switching of the switch
55 in a predetermined cycle. According to the switching
control by the control unit 100,
the differential
amplification unit 50 outputs a voltage corresponding to a
difference between received light levels, and a voltage
corresponding to the sum of the received light levels by
calculating in a time division method.
Hereinafter,
descriptions will be made by referring to the voltage
corresponding to the difference between received light levels
as a "subtraction output voltagen,
and the voltage ~
corresponding to the sum of the received light levels as an
"addition output voltagen.
[0028]
In addition, the control unit 100 variably sets the
amplification factor of the differential amplification unit
50 (amplification circuit 57). Specifically, when the switch
55 is switched to the subtracter 53 side, the subtraction output
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voltage is amplified with a first amplification factor "Gl"
by setting the amplification factor to the first amplification
factor "Gl". In contrast to this, when the switch 55 is
switched to the adder 51 side, the addition output voltage is
amplified with a second amplification factor "G2" by setting
the amplification factor to the second amplification factor
"G2" which is lower than the first amplification factor "Gl".
[0029]
The control unit 100 includes a transmitted amount of
light determination unit 110 which determines amount of light
of transmitted light from the addition output val tage (sum of
received light levels) which is output from the differential
amplification unit 50, and an amplification factor setting
unit 120 which variably sets an amplification factor of the
differential amplification unit 50. An angle of optical
rotation calculation unit 150 which calculates the angle of
optical rotation is configured by the differential
amplification unit 50 and the control unit 100 in the first
optical measurement device 1A.
[0030]
The control unit 100 is a control unit which collectively
controls each unit of the first optical measurement device 1A,
and is configured by including a microprocessor such as a CPU
(Central Processing Unit) , or a DSP (Digital Signal Processor) ,
an ASIC (Application Specific Integrated Circuit), or the
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like.
[0031]
The operation unit 200 is an input unit which is
configured by including a button switch, or the like, and
outputs a signal of a pressed button to the control unit 100.
Due to an operation of the operation unit 200, various
instruction inputs such as an instruction on starting the
measurement of the angle of optical rotation, and the like,
are performed.
[0032]
The display unit 300 is configured by including an LCD
(Liquid Crystal Display), or the like, and is a display unit
which performs various displays based on a display signal which
is input from the control unit 100. Information on the
measured angle of optical rotation, or the like is displayed
on the display unit 300.
[0033]
The sound output unit 400 is a sound output unit which
outputs various sounds based on a sound output signal which
is input from the control unit 100.
[0034]
The communication unit 500 is a communication unit which
transmits and receives information which is used in the unit
to and from an external information processing device
according to a control of the control unit 100. As a
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communication method of the communication unit 500, various
methods such as a type in which a wired connection is made
through a cable which is conformed with a predetermined
communication standard, a type in which a connection is made
through an intermediate device which is used also as a battery
charger which is referred to as a cradle, or a type in which
a wireless connection is made using a pear field wireless
communication are applied.
[0035]
The storage unit 600 is configured by including a storage
unit such as a ROM (Read Only Memory), a flash ROM, or a RAM
(Random Access Memory). The stora.ge unit 600 stores a system
program of the first optical measurement device lA, various
programs for executing various functions such as a measuring
function of the angle of optical rotation, data, or the like.
In addition, a work area in which data in the middle of
processing of various processes, a processing result, or the
like is temporarily stored is included.
[ 0036]
The storage unit 600 is stored with a first angle of
optical rotation. measurement program 610 which is read out by
the control unit 100, and is executed as first angle of optical
rotation measurement processing (refer to Fig. 3) , The first
angle of optical rotation measurement processing will be
described in detail later using a flowchart.
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[0037)
In addition, the storage unit 600 is stored with
parameter data for control 620, output voltage data 630, and
a calculated angle of optical rotation 640.
[0038)
Fig. 2 is a·table showing a data structure example of
a parameter data for control 620.
The parameter data for control 620 is data which is used
when the control unit 100 controls the differential
amplification unit 50, and is prescribed in the form of a table
in which switching setting of the switch 55, and the
amplification factor of the amplification circuit 57 are
correlated with each other regarding the respective
subtraction and addition. The control unit 100 controls the
differential amplification unit 50 according to the parameter
data for control 620.
[0039]
The output voltage data 630 is data in which a voltage
which is output from the differential amplification unit 50
is stored. Specifically, the output voltage data 630 is stored
with the subtraction output voltage and the addition output
voltage in time sequence which are alternately output from the
differential amplification unit 50 in the time division method
so that it is possible to identify what output voltage i~ is.
In addition, the calculated angle of optical rotation
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640 is data in which an angle of optical rotation which is
calculated by the control unit 100 is stored.
[0040]
1-2. Calculation method of angle of optical rotation
A calculation method of the angle of optical rotation
according to the first embodiment will be described in detail.
The amount of light of the transmit ted light which
transmitted the test object A is set to "Ea2
", an incident angle
of linearly polarized light with respect to the orthogonal
separation unit 30 is set to "80", and the angle of optical
rotation by the test object A is set to "9". At this time,
electric field components of P polarization and S polarization
are expressed by "Eacos (9+90 ) 11
, and "Easin (8+9o) 11
, respectively.
Accordingly, the P polarization voltage and the S polarization
voltage are expressed by "Ea2cos2 (9+80 )", and "Ea
2
sin
2
(9+80 )
11
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respectively.
[0041]
At this time, it is possible to obtain a subtraction
voltage "Vs 11 as in the following expression ( 1) by subtracting
the S polarization voltage from the P polarization voltage.
In addition, it is possible to obtain an addition voltage "Va11
as in the following expression ( 2) by adding the P polarization
voltage to the S polarization voltage.
[Expression 1]
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Vs = Ea2 cos2(8 + Bn)- Ea2 sin 2(8 + 80 )
= £a2(cos 2(8+B0)-sin 2(B+B0)} .. (1)
[Expression 2]
Va = Ea2 cos 2(B +80 )+ Ea 2 sin2(B + 80 )
= Ea2 (cos 2(B + 80 )+ sin 2(8 + 80 ))
= Ea 2 ···(2)
[0042]
The differential amplification unit 50 calculates the
subtraction voltage "Vs" and the addition voltage "Va" which
are expressed in the expressions (1) and (2), and amplifies
the calculation result using an amplification factor which is
instructed from the control unit 100. Since a·n amplification
fact.or with respect to the subtraction voltage "Vs" is "G1",
and an amplification factor with respect to the addition
voltage "Va" is "G2", the subtraction output voltage "V1" and
the addition output voltage "V2" which are output from the
differential amplification unit 50 become the following
expressions (3), and (4), respectively.
[Expression 3]
Vl=Gl·Vs
= Gl· Ea2 (cos2(B + B0)-sin 2(B + 80 )}··(3)
[Expression 4]
V2=G2·Va
= G2· Ea2 ···(4)
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[0043]
It is possible to derive the following expression (5)
from the expressions (3) and (4).
[Expression 5]
-G2- V=I cos2 (8+ 8 • 0 )-sm2(B +00 )
Gl V2
=cos 2(8 + 80 )··· (5)
[0044]
Accordingly, it is possible to calculate the angle of
optical rotation "8" from the expression (5) as in the following
expression (6).
[Expression 6]
(J = _!_arccos(G2 Vl )-eo 2 Gl V2
=~arccos( CI ~~)-e. ···(6)
However, it is replaced with "G2/Gl=C1".
[0045]
According to the expression (6), two parameter values
of "Cl" and "8
0
" are necessary in order to calculate the angle
of optical rotation "8". For example, the "Cl" can be obtained
from a ratio of the first amplification factor "Gl" to the
second amplification factor "G2" which is prescribed in the
parameter data for control 620, and the "80 " can be mechanically
set to a predetermined angle, or the like.
[0046]
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Since an angle of optical rotation which is expressed
at an extremely minute angle is set to a measurement target,
the above described parameter value greatly influences on
measurement precision of the angle of optical rotation. An
error which is caused by a temperature property of a circuit
element, precision in a design value, or the like, can be
included in the amplification factor in design (design value)
of the differential amplification unit 50. It is also
considered that the measurement precision of the angle of
optical rotation deteriorates due to the error.
[0047]
Therefore, according to the embodiment, it is possible
to set the "Cl" and "90" by performing an initial correction.
Specifically, an equation which derives an angle of optical
rotation is set up using two or more kinds of substances whose
angles of optical rotation are well-known as the test object
A. Since there are two unknown number of "Cl" and "9o", two
unknown numbers are obtained when two or more equations are
set up. A solution of the equation can be calculated using,
for example, a well-known numerical calculation such as a least
squares method.
[0048]
1-3. Flow of processing
Fig. 3 is a flowchart which illustrates a flow of the.
first angle of optical rotation measurement processing which
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is executed by the control unit 100 according to the first angle
of optical rotation measurement program 610 which is stored
in the storage unit 600.
[0049]
Firstly, the control unit 100 performs a first initial
correction processing (step AD) . Specifically, two parameter
values of "C1" and "80" in the expression (6) are corrected
based on the above described method, or the like.
[0050]
Subsequently, the control unit 100 performs an
arrangement instruction of the test object A (step A1). For
example, a message is displayed on the display unit 300, or
a sound guidance is output from the sound output unit 400. In
addition, the control unit 100 causes the light source 10 to
start radiating of laser light (step A3).
[ 0051]
Subsequently, the control unit 100 executes a control
for subtraction (step AS). Specifically, a switch switching
signal S1 which switches to the subtracter 53 side is output
to the switch 55 by referring to the parameter data for control
620. In addition, a control signal for setting the
amplification factor of the amplification circuit 57 to Gl is
output to the amplification circuit 57. In addition, the
control unit 100 causes the output voltage from the
differential amplification unit 50 to be stored in the output
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voltage data 630 as the subtraction output voltage (step A7).
[0052]
Subsequently, the control unit 100 executes a control
for adding (step A9). Specifically, a switch switching signal
S2 which switches to the adder 51 side is output to the switch
55 by referring to the parameter data for control 620. In
addition, a control signal for setting the amplification
factor of the amplification circuit 57 to G2 is output to the
amplification circuit 57. In addition, the control unit 100
causes the output voltage from the differential amplification
unit 50 to be stored in the output voltage data 630 as the
addition output voltage (step All).
[0053]
Processes of the above described steps AS to All are
executed until data of output voltages of a predetermined time
is obtained (step Al3). When the data of output voltage of
the predetermined time is obtained (Yes in step Al3), the
control unit 100 stops the radiation of laser light of the light
source 10 (step Al5).
[0054]
Thereafter, the control unit 100 calculates the angle
of optical rotation according to the expression (6) using a
parameter value which is corrected in the first initial
correction processing, a mean value of the subtraction output
voltage, and a mean value of the addition output voltage of
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the predetermined time which is stored in the output voltage
data 630, and stores the angle of optical rotation in the
storage unit 600 as the calculated angle of optical rotation
640 (step A17).
[ 0055]
In addition, it is also prefer:able to calculate the angle
of optical rotation "8" using instantaneous values of the
subtraction output voltage "Vl" and the addition output
voltage "V2", however, in order to improve calculation
precision of the angle of optical rotation "8", it is effective
when the angle of optical rotation "8" is calculated according
to the expression (6) using, for example, a mean value of the
subtraction output voltage "Vl", and the addition output
voltage "V2" of the predetermined time.
[ 0056]
As is understood from the expression (6), according to
the embodiment, the subtraction output voltage "Vl" is divided
by the addition output voltage "V2", and the angle of optical
rotation "8" is calculated using the result. The addition
output voltage "V2" is a voltage corresponding to amount of
light of transmitted light.
In addition, the subtraction
output voltage "Vl" is a voltage corresponding to a difference
between the received light levels. Accordingly, dividing the
subtraction output voltage "Vl" by the addition output voltage
"V2" means normalizing the difference between received lig~t
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levels using the amount of light of the transmitted light, and
the angle of optical rotation "0" is calculated from the
difference between the normalized received light levels.
[0057]
Returning to the descriptions in the flowchart in Fig.
3, when the control unit 100 determines whether or not to end
the measurement of the angle of optical rotation (step A19),
and determines to continue the measurement (No in step A19),
after calculating the angle of optical rotation, the process
returns to step Al. In addition, when it is determined to end
the measurement (Yes in step A19), the first angle of optical
rotation measurement processing is ended.
[0058]
1-4. Effects of operation
In the first optical measurement device 1A, light which
is output from the light source 10 becomes the linearly
polarized light in the polarizing unit 20, and is input to the
test object A. The transmitted light which transmitted the
test object A is orthogonally separated in the orthogonal
separation unit 30, and the light which is orthogonally
separated in the orthogonal separation unit 30 is received in
at least two light receiving units 40 (40A and 408). In
addition, the amount of light of the transmitted light is
determined in the control unit 100, the difference between the
received light levels which are received in the light receiving
25
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unit 40 is normalized using the amount of light which is
determined in a transmitted amount of light determination unit,
and then the angle of optical rotation is calculated by the
angle of optical rotation calculation unit 150.
[0059]
If the angle of optical rotation is calculated simply
using the difference between the received light levels which
are received in the light receiving unit 4 0, when a fluctuation
in the amount of light of the transmitted light occurs, it is
difficult to obtain an accurate angle of optical rotation due
to the fluctuation in the amount of light. However, since the
amount of light of the transmitted light is determined, and
the angle of optical rotation is calculated after normalizing
the difference between the received light levels using the
amount of light in the first optical measurement device lA,
it is possible to accurately calculate the angle of optical
rotation even when the amount of light of the transmitted light
fluctuates.
[0060]
More specifically, the difference and the sum of the
received light levels in the light receiving unit 40 are
obtained in a time division method in the differential
amplification unit 50.
The transmitted amount of light
determination unit of the control unit 100 determines the
amount of light of the transmitted light using the sum of the
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received light levels which are received in the light receiving
unit 40, and normalizes the difference between the received
light levels using the determined amount of light of the
transmitted light. With this configuration, it is possible
to determine the amount of light of the transmit ted light using
a simple method such as obtaining the sum of the received light
levels.
[0061]
In addition, the control unit 100 variably sets the
amplification factor of the differential amplification unit
50. Specifically, when the differential amplification unit
50 calculates the difference between the received light levels,
the amplification factor is set to a first amplification factor,
and when the differential amplification unit 50 calculates the
sum of the received light levels, the amplification factor is
set to a second amplification factor which is lower than the
first amplification factor. Since the difference between the
received light levels is a minute value, it is possible to
calculate the angle of optical rotation with high preclsion
according to the received light levels by improving resolution
by setting the amplification factor high compared to a case
of obtaining the sum of the received light levels.
[ 0 0 62]
2. Second Embodiment
2-1. Configuration
27
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Fig. 4 is a diagram which illustrates a configuration
example of a second optical measurement device 1B in a second
embodiment. The second optical measurement device lB is
configured by including a light source 10, a polarizing unit
20, a non-polarizing separation unit 25, an orthogonal
separation unit 30, a light receiving unit 40, a second
differential amplification unit 70, a second light receiving
unit 80, an amplification unit 90, a control unit 100, an
operation unit 200, a display unit 300, a sound output unit
400, a communication unit 500, and a storage unit 600. In
addition, the same constituent elements as those in the first
optical measurement device lA will be given the same reference
numerals, and repeated descriptions will be omitted.
[0063]
In the second optical measurement device lB, the
non-polarizing separation unit 25 is provided between a test
object A and the orthogonal separation unit 30. The
non-polarizing separation unit 25 is a polarizing element
which separates incident light into transmitted light and
reflected light in a predetermined amount of light ratio while
maintaining a polarized state o~ the incident light. It is
possible to apply, for example, a non-polarizing beam splitter
as the non-polarizing separation unit 25.
[ 00 64]
Light on one side which is separated by the
28
..
non-polarizing separation unit 25 inputs to the orthogonal
separation unit 30, and is separated into a P polarized
component and S polarized component. In contrast to this,
light on the other side which is separated by the non-polarizing
separation unit 25 is received in the second light receiving
unit 80. The light which is received in the second light
receiving unit 80 is subject to photoelectric conversion, and
a voltage corresponding to amount of light is output to the
amplification unit 90. In addition, the light is amplified
in a predetermined amplification factor in the amplification
unit 90, and then is output to the control unit 100. The
transmitted amount of light determination unit 110 determines
amount of light of transmitted light based on received light
levels of the second light receiving unit 80.
[0065]
Since the amount of light separation proportion of the
incident light by the non-polarizing separation unit 25 is
well-known, the transmitted amount of light determination unit
110 is able to calculate the whole amount of light of the
transmitted light using the light receiving level of the second
light receiving unit 80, and also to calculate the amount of
light which is input to the orthogonal separation unit 30.
[0066]
On the other hand, the P polarization voltage which is
subject to the photoelectric conversion in the P polarized
29
..
light receiving unit 40A of the light receiving unit 40, and
the S polarization voltage which is subject to the
photoelectric conversion in the S polarized light receiving
unit 40B are output to the second differential amplification
unit 70. In the second differential amplification unit 70,
a difference between the P polarization voltage and the S
polarization voltage is calculated, and is output to the
control unit 100 after being amplified with a predetermined
amplification factor.
Accordingly, only the subtraction
output voltage which is mentioned in the first embodiment is
output from the second differential amplification unit 70.
[0067]
In addition, the storage unit 600 is stored with a second
angle of optical rotation measurement program 612 which is
executed as second angle of optical rotation .measurement
processing (refer to Fig. 5) by the control unit 100, output
voltage data 630, and a calculated angle of optical rotation
640.
[0068]
2-2. Calculation method of angle of optical rotation
A calculation method of the angle of optical rotation
according to the second embodiment will be described in detail.
Transmitted light which has transrni tted the test object
A is subject to a non-polarizing separation into "T1:T2" by
the non-polarizing separation unit 25 (here, T1+T2=1).
30
..
· Specifically, amount of light "Ea2
" of the transmitted light
is separated into "Tl:T2", light of amount of light "Tl·Ea
2
"
..
is received in the light receiving unit 40, and light of amount
of light "T2·Ea2" is received in the second light receiving unit
80.
[0069]
At this time, the P polarizing voltage and the S
polarizing voltage which are received in the P polarized light
receiving unit 40A and the S polarized light receiving unit
40B, and are subject to the photoelectric conversion are
(8+8o) ",
respectively. Accordingly, the subtraction voltage "Vs" when
the S polarizing voltage is subtracted from the P polarizing
voltage is expressed in the following expression (7) .
[Expression 7]
Vs = Tl· Ea 2 (cos 2 (8 + B0)- sin 2 (8 + 80)} •• (7)
[0070]
On the other hand, a voltage "V" which is received in
the second light receiving unit 80, and is subject to the
photoelectric conversion is given in the following expression
( 8) •
[Expression 8]
V = T2 · Ea1
• · • (8)
31
..
[0071]
The second differential amplification unit 70 amplifies
the subtraction voltage "Vs" which is expressed in the
expression (7) with an amplification factor "G3". As a result,
a subtraction output voltage "V3" which is output from the
second differential amplification unit 70 is expressed as in
the following expression (9).
[Expression 9]
V3=G3·Vs
= G3· n · Ea2(cos2(B + B0
)-sin2(B +00)} .. (9)
[0072]
In addition, the amplification unit 90 amplifies the
voltage _"V" which is expressed in the expression (8) with an
amplification factor "G4". As a result, an output voltage "V4"
which is output from the amplification unit 90 is expressed
as in the following expression (10).
[Expression 10]
V4=G4·V
= G4 · T2 · Ea 2
.. • (1 0)
[ 007 3]
The following expression ( 11) is derived from the
expressions (9) and (10).
[Expression 11]
32
..
-G4- T2- V=3 cos 2 (B + 0 . 0)-sm 2(8+80 )
G3 Tl V4
=cos 2(B + B0 )··· (11)
[0074]
Accordingly, it is possible to calculate the angle of
optical rotation "8" as iri the following expression (12) from
the expression (11).
[Expression 12]
B =_!_arccos (G4 T2 V3) _ Bo
2 G3 Tt V4
=-1a rccos ( C2V3-) -8 ··· (12)
2 V4 et
However, it is replaced with "(G4/G3) (T2/T1)=C2".
[0075]
Similarly to the first embodiment, even in this case,
it is effective when determining two parameter values of "C2"
and "8
0
" in the expression (12) by performing a measurement
using, for example, two or more substances whose angles of
optical rotation are known.
[0076]
2-3. Flow of processing
Fig. 5 is a flowchart which illustrates a flow of the
second angle of optical rotation measurement processing which
is executed by the control unit 100 according to the second
angle of optical rotation measurement program 612 which is
stored in the storage unit 600. In addition, the same steps
33
' .
as those in the first angle of optical rotation measurement
processing are given the same reference numerals, and repeated
descriptions will be omitted.
[0077]
First, the control unit 100 performs second initial
correction processing (step BO) . Specifically, the two
parameter values of "C2" and "80" in the expression (12) are
corrected based on the above described method, or the like.
[0078]
The control unit 100 stores the subtraction output
voltage which is output from the second differential
amplification unit 70, and the output voltage which is output
from the amplification unit 90 in the output voltage data 630
of the storage unit 600 after performing a start control of
radiating laser light in step A3 (step B5). In addition, the
control unit 100 continuously stores the data of the output
voltage until data of the output voltage of a predetermined
time is obtained (No in step A13~step B5).
[0079]
When the output voltage of the predetermined time is
obtained (Yes in step A13), the control unit 100 performs a
stop control of radiating of the laser light (step A15). In
addition, the control unit 100 calculates the angle of optical
rotation according to the expression ( 12) using the parameter
value which is corrected in the second initial correction
34
' .
processing, and a mean value of the subtraction output voltage,
and a mean value of the output voltage which are stored in the
output voltage data 630, and stores the angle of optical
rotation in the storage unit 600 as the calculated angle of
optical rotation 640 (step B17).
[0080]
2-4. Effects of operation
In the second optical measurement device 1B, transmitted
light in which the linearly polarized light which is output
from the light source 10, and is converted by the polarizing
unit 20 passes through the test object A is subject to the
non-polarizing separation in a predetermined proportion by the
non-polarizing separation unit 2 5. In addition, light on one
side which is subject to the non-polarizing separation is
received in the second light receiving unit 80. In addition,
light on the other side which is subject to the non-polarizing
separation is orthogonally separated by the orthogonal
separation unit 30.
In addition, the control unit 100
determines the amount of light of the transmitted light based
on the light receiving level in the second light receiving unit
80, and calculates the angle of optical rotation after
normalizing a difference between the received light levels in
the light receiving unit 40 using the determined amount of
light.
[0081]
35
..
In the second optical measurement device lB, the
difference between the received light levels is normalized
·using the amount of light which is subject to the non-polarizing
separation by the non-polarizing separation unit 25, not
normalizing the difference in the received light levels using
the amount of light of the transmit ted light corresponding to
the sum of the received light levels which are received in the
light receiving unit 40. The amount of light of the
transmitted light is determined by adopting a simple
configuration in which the transmitted light is subject to the
non-polarizing separation by the non-polarizing separation
unit 25, and light on one side thereof is received in the second
light receiving unit 80. In addition, it is possible to
accurately calculate the angle of optical rotation even when
a fluctuation in the amount of light of the transmitted light
occurs by normalizing the difference between the received
light levels in the light receiving unit 40 using the determined
amount of light.
[0082]
3. Modification Example
Embodiments to which the invention is applied are not
limited to the above described embodiments, and as a matter
of course, the embodiments can be appropriately changed
without departing from the scope of the invention.
Hereinafter, modification examples will be described.
36
' .
[0083]
3-1. Application Example
The optical measurement devices which are described in
the above described embodiments (first optical measurement
device lA, and second optical measurement device lB) can be
used by being incorporated in measuring equipment, for example,
sugar measuring equipment which measures sugar in fruits,
blood sugar level measuring equipment. which measures a human
blood sugar level.
[0084]
When the optical measurement device is applied to the
sugar measuring equipment, an angle of optical rotation is
calculated by radiating linearly polarized light to, for
example, fruit juice of fruit as a test object A. In addition,
when the optical measurement device is applied to the blood
sugar level measuring equipment, the angle of optical rotation
is calculated by radiating the linearly polarized light to a
portion to be measured, by setting portions having
transmitting property such as an earlobe, fingertips,
epidermis parts of fingers as portions to be'measured. In
addition, the sugar of fruit, or the human blood sugar level
can be obtained based on the calculated ·angle of optical
rotation.
[0085]
3-2. Amplification factor of differential
37
' .
amplification unit
In the above described embodiments, the amplification
factor was s~t to be switched in a case in which the difference
between the received light levels is calculated, and in a case
in which the sum of the received light levels is calculated
by the differential amplification unit 50 of the first optical
measurement device lA, however, a method of variably setting
the amplification factor of the differential amplification
unit 50 is not limited to this. For example, the amplification
factor of the differential amplification unit 50 may also be
variably set based on the difference between the received light
levels which are calculated in the differential amplification
unit 50. The smaller the difference between the received light
levels, it is effective to set the amplification factor high.
[0086]
In addition, when it is possible to measure absorbance
of an component which is included in the test object A, it is
also possible to variably set the amplification factor of the
differential amplification unit 50 based on the magnitude of
the absorbance. When the absorbance of the component which
is included in the test object A is large, the amount of light
in the transmitted light is reduced. For this reason, it is
possible to perform a measurement of the transmitted light in
a wide dynamic range by setting the amplification factor of
the differential amplification unit 50 high, and amplifying
38
..
the difference between the received light levels with a high
amplification factor.
[0087]
In addition, the amplification factor of the
differential amplification unit 50 may be variably set based
on the magnitude of the angle of optical rotation. It.is
possible to measure the angle of optical rotation in a wide
dynamic range by setting the amplification factor of the
differential amplification unit 50 high, and amplifying the
difference between the received light levels with a high
amplification factor, when the angle of optical rotation is
small.
[0088]
The above described setting method of the amplification
factor can be similarly applied to the second differential
amplification unit 70 of the second optical measurement device
lB, as well. That is, it is also preferable to variably set
the amplification factor of the second differential
amplification unit 70 based on the difference between the
received light levels which is calculated in the second
differential amplification unit 70. In addition, the
amplification factor of the second differential amplification
unit 70 may be variably set based on the absorbance of an
component which is included in the test object A, or the
magnitude of the angle of optical rotation.
39
' .
[0089]
3-3. Calculation method of angle of optical rotation
According to the above described embodiment, the angle
of optical rotation was calculated using a mean value of an
output voltage of a predetermined time, however, a calculation
method of an angle of optical rotation is not limited to this.
For example, as a matter of course, the angle of optical
rotation may be calculated using an instantaneous value of an
output voltage. In addition, it is also possible that angles
of optical rotation of a predetermined time, or of a
predetermined number are calculated by repeating a step of
calculating the angle of optical rotation using the
instantaneous value of an output voJ.tage, and the angle of
optical rotation is calculated by calculating the average of
these angles of optical rotation.
[ 0090]
3-4. Optical element for polarization
According to the above described embodiment, it has been
described that the polarizing unit 20 is configured- by
including, for example, the Glan Thompson prism, however, it
is natural to have a configuration in which other optical
element for polarization than that is included. For example,
it is also possible to have a configuration in which the Glan
Tailor prism which is the same Glan-type optical element for
polarization is included.
40
[0091] '
In addition, according to the above described embodiment,
it has been described that the orthogonal separation unit 30
is configured by including, for example, the Wollaston prism,
however, it is possible to suitably change the optical element
for polarization which configures the orthogonal separation
unit 30. For example, it is also ·possible to have a
configuration in which an optical element for polarization
having a function of orthogonal separation such as the Glan
Laser prism, or a lotion prism is included.
[Description of Reference Numeral]
[0092]
lA: FIRST OPTICAL MEASUREMENT DEVICE
lB: SECOND OPTICAL MEASUREMENT DEVICE
10: LIGHT SOURCE
20: POLARIZING UNIT
25: NON-POLARIZING SEPARATION UNIT
30: ORTHOGONAL SEPARATION UNIT
40: LIGHT RECEIVING UNIT
40A: p POLARIZED LIGHT RECEIVING UNIT
40B: s POLARIZED LIGHT RECEIVING UNIT
50: DIFFERENTIAL AMPLIFICATION UNIT
51: ADDER
53: SUBTRACTER
55: SWITCH
41
••
57: AMPLIFICATION CIRCUIT
70: SECOND DIFFERENTIAL AMPLIFICATION UNIT
80: SECOND LIGHT RECEIVING UNIT
90: AMPLIFICATION UNIT
100: CONTROL UNIT
150: ANGLE OF OPTICAL ROTATION CALCULATION UNIT
200: OPERATION UNIT
300: DISPLAY UNIT
400: SOUND OUTPUT UNIT
500: COMMUNICATION UNIT
600: STORAGE UNIT

[Designation of Document] CLAIMS
[Claim 1]
An optical measurement device comprising:
an orthogonal separation unit which orthogonally
separates transmitted light in which linearly polarized light
has passed through a test object;
at least two light receiving units which receive light
which is orthogonally separated in the orthogonal separation
unit;' and
an angle of optical rotation calculation unit which
includes a transmitted amount of light determination unit
which determines amount of light of the transmitted light, or
amount of Aight of a predetermined proportion of the amount
of light, and calculates an angle of optical rotation after
normalizing a difference between the received light levels
which are received in the light receiving unit using the amount
of light which is determined in the transmitted amount of light
determination unit.
[Claim 2]
The optical measurement device according to claim 1,
wherein the angle of optical rotation calculation unit
has a differential amplification unit obtaining a difference
between the received light levels, and further has an
amplification factor setting unit which variably sets an
amplification factor of the differential amplification unit.
43
[Claim 3]
The optical measurement device according to claim 1, or
2,
wherein the transmitted amount of light determ.ination
unit determines the amount of light using the sum of the
received light levels which are received in the light receiving
unit.
[Claim 4]
The optical measurement device according to claim 1, or
2, further comprising:
a non-polarizing division unit which divides the
transmitted light using the predetermined proportion in a
non-polarizing manner; and
a second light receiving unit which receives light on
one side which is divided in the non-polarizing manner,
wherein the orthogonal separation unit orthogonally
separates light on the other side which is divided in the
non-polarizing manner, and
wherein the transmitted amount of light determination
unit determines amount of light of the transmitted light of
the predetermined proportion based on the received light
levels of the second light receiving unit.
[Claim 5]
An optical measurement method comprising:
orthogonally separating transmitted light in which
44
i
, 1
linearly polarized light is passed through a test object;
receiving the orthogonally separated light;
determining amount of light of the transmitted light,
or amount of light of a predetermined proportion of the amount
of light; and
calculating an angle of optical rotation after
normalizing a difference between the received light levels
using the determined amount of light.