Description
Title of Invention: PROJECTION DISPLAY APPARATUS AND
METHOD OF CONTROLLING THE SAME
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The entire disclosure of Japanese Patent Application No.2010-20641 1, filed
September 15, 2010 is expressly incorporated by reference herein.
Technical Field
[0002] The present invention relates to a projection display apparatus capable of performing
keystone correction and a method of controlling the same.
Background Art
[0003] Some projection display apparatuses (projectors) have a function for keystone
correction (trapezoidal distortion correction). The keystone correction includes vertical
keystone correction, as correction in the top and bottom direction, and horizontal
keystone correction, as correction in the right and left direction. The projection display
apparatuses having the keystone correction function include a manual type which is
provided with two discrete rotary knobs to adjust the amount of vertical keystone
correction and the amount of horizontal keystone correction in accordance with
rotations of the rotary knobs (refer to PTL 1, for example).
Citation List
Patent Literature
[0004] PTL 1: JP-A-2003-9038
Summary of Invention
Technical Problem
[0005] When the projection display apparatus is accurately disposed so as to face a
projection screen, horizontal keystone correction is not needed. In this case, a user
operates the rotary knob such that the amount of horizontal keystone correction
(hereinafter, "horizontal keystone correction amount") is zero. Practically, however, it
is difficult to operate an analog operation device, such as a rotary knob, to a single
operation position where the amount of keystone correction (hereinafter, "keystone
correction amount") is zero. If the user has intended to operate the rotary knob to such
a zero position, the knob may be actually deviated from the position slightly.
[0006] If the display apparatus is provided with a click mechanism to generate a mechanical
click state (a click and sense of clicking) at the zero position where the keystone
correction amount is zero, it is just conceivable that the user may actually operate the
rotary knob to a position slightly deviated from the zero position though the user has
intended to operate the knob to the zero position. Simply adding the click mechanism
does not solve the difficulty of controlling the amount of correction to zero.
[0007] If such an operation device includes a variable resistor, serving as a relatively in
expensive part, such that the keystone correction amount is set by a voltage value
changed through the variable resistor, individual variations between variable resistors
result in variations in voltage value. Each variable resistor therefore needs calibration.
Furthermore, a voltage value set by the variable resistor varies depending on, for
example, variation in power supply voltage or temperature drift. In the use of the
variable resistor, therefore, it is more difficult to set a keystone correction amount to
zero.
[0008] If the display apparatus is configured such that the current keystone correction
amount is indicated in a projected image, the user can easily control the keystone
correction amount to zero. Indication processing is, however, required separately. Fur
thermore, since such an indication overlaps part of the image which the user is
viewing, it hinders the viewing.
[0009] The present invention has been made in consideration of the above-described cir
cumstances. The present invention provides a projection display apparatus in which a
user can easily adjust the keystone correction amount to zero without relying on an in
dication, and a method of controlling the same.
Solution to Problem
[0010] An aspect of the present invention provides a projection display apparatus including
an image projecting unit that projects an image, an operation unit whose output value
changes depending on the amount of operation, a correction amount setting unit that
changes a keystone correction amount in accordance with an output value of the
operation unit, and a keystone correcting unit that performs keystone correction on an
image to be projected in accordance with the keystone correction amount, wherein a
zero reference position in which the keystone correction amount is zero is set within an
operation range of the operation unit, a dead zone, which includes the zero reference
position and an area surrounding the zero reference position, is set within the operation
range of the operation unit, and the correction amount setting unit sets the keystone
correction amount to zero in accordance with the output value corresponding to the
inside of the dead zone.
[001 1] With this configuration, the dead zone including the zero reference position of the
operation unit and the area surrounding the zero reference position is set within the
operation range of the operation unit and the keystone correction amount is set to zero
in accordance with the output value, corresponding to the inside of the dead zone, of
the operation unit. Accordingly, the user can easily set the keystone correction amount
to zero without relying on an indication of the keystone correction amount.
[0012] In this aspect of the present invention, the keystone correction amount may be easily
set to zero using an inexpensive variable resistor. Advantageously, the user can adjust
the keystone correction amount instinctively.
[0013] In this aspect of the present invention, the keystone correction amount may be easily
set to zero while information regarding the keystone correction amount is not provided
to the user.
[0014] In this aspect of the present invention, if the operation unit is operated within the
dead zone, pixel interpolation may be inhibited. Advantageously, an input image can
be displayed faithfully, thus improving image quality.
[0015] In this aspect of the present invention, the operation unit may reliably provide a click
state within the dead zone. Accordingly, the user can easily and reliably set the
keystone correction amount to zero without relying on vision. In this case, the
operation unit may provide the click state at the zero reference position. With this con
figuration, the keystone correction amount can be more easily and reliably set to zero.
[0016] Another aspect of the present invention provides a method of controlling a projection
display apparatus that projects an image, the apparatus including an operation unit
whose output value changes depending on the amount of operation, the method
including changing a keystone correction amount in accordance with an output value
of the operation unit, performing keystone correction on an image to be projected in
accordance with the keystone correction amount, setting a zero reference position, in
which the keystone correction amount is zero, within an operation range of the
operation unit, setting a dead zone within the operation range of the operation unit such
that the dead zone includes the zero reference position and an area surrounding the
zero reference position, and setting the keystone correction amount to zero in ac
cordance with the output value corresponding to the inside of the dead zone.
[0017] With this configuration, the dead zone including the zero reference position of the
operation unit and the area surrounding the zero reference position is set within the
operation range of the operation unit and the keystone correction amount is set to zero
in accordance with the output value, corresponding to the inside of the dead zone, of
the operation unit. Accordingly, the user can easily set the keystone correction amount
to zero without relying on an indication of the keystone correction amount.
Advantageous Effects of Invention
[0018] Another aspect of the present invention provides a projection display apparatus
including an image projecting unit that projects an image, an operation unit, whose
output value changes depending on the amount of operation, that is a sliding operation
device capable of being operated in a direction orthogonal to a projection direction in
which the image is projected by the image projecting unit, a correction amount setting
unit that sets a keystone correction amount in the direction orthogonal to the projection
direction, and changes the keystone correction amount in accordance with an output
value of the operation unit; and a keystone correcting unit that performs keystone
correction on an image to be projected in accordance with the keystone correction
amount.
[0019] With this configuration, the user can adjust the keystone correction amount in
stinctively.
[0020] According to the present invention, the user can easily set the keystone correction
amount without relying on an indication of the keystone correction amount.
Brief Description of Drawings
[0021] [fig. l]Fig. 1 is a diagram illustrating a projector according to an embodiment of the
present invention.
[fig.2A]Fig. 2A is a diagram explaining a case where the projector is tilted in the top
and bottom direction.
[fig.2B]Fig. 2B is a diagram explaining a case where the projector is tilted in the right
and left direction.
[fig.3]Fig. 3 is a block diagram of the functional configuration of the projector.
[fig.4]Fig. 4 is a graph illustrating of the relationship between a keystone operation
unit and a horizontal keystone correction amount.
[fig.5]Fig. 5 is a flowchart of an operation mode switching process.
[fig.6A]Fig. 6A is a diagram explaining a non-adjustment mode.
[fig.6B]Fig. 6B is a diagram explaining an adjustment mode.
[fig.7]Fig. 7 is a flowchart of control by a filter.
Description of Embodiment
[0022] An embodiment of the present invention will be described below with reference to
the drawings.
[0023] Fig. 1 illustrates a projector (projection display apparatus) 10 according to an em
bodiment of the present invention. The projector 10 projects image light representing
an image to display an image (projected image) PM on a screen SC, serving as a
projection plane. The projector 10 has a keystone correction (trapezoidal distortion
correction) function of correcting a trapezoidal distortion of the projected image PM
caused by the relative positional relationship between the projector 10 and the screen
SC. The projected image PM may be either of a still image and a moving image.
[0024] Fig. 2A is a diagram explaining a case where the projector 10 is tilted in the top and
bottom direction (also referred to as "the vertical direction" or "the longitudinal
direction"). Referring to Fig. 2A, the optical axis OA of projected light is tilted in the
top and bottom direction relative to a normal NL of the screen SC by a tilt angle thetal
(hereinafter, referred to as a "vertical tilt angle thetal). If keystone correction is not
performed, a trapezoidally distorted projected image PM1 is displayed such that the
length of the upper side of the image differs from that of the lower side as illustrated in
left part of Fig. 2A. Right part of Fig. 2A illustrates a projected image PM1 1 subjected
to keystone correction in the top and bottom direction (vertical keystone correction) for
the vertical tilt angle thetal.
[0025] Fig. 2B is a diagram explaining a case where the projector 10 is tilted in the right and
left direction (also referred to as "the horizontal direction" or "the lateral direction").
Referring to Fig. 2B, the optical axis OA of projected light is tilted in the right and left
direction relative to the normal NL of the screen SC by a tilt angle theta2 (hereinafter,
referred to as the "horizontal tilt angle theta2"). If keystone correction is not
performed, a trapezoidally distorted projected image PM2 is displayed such that the
length of the left side of the image differs from that of the right side as illustrated in
left part of Fig. 2B. Right part of Fig. 2B illustrates a projected image PM22 subjected
to keystone correction in the right and left direction (horizontal keystone correction)
for the horizontal tilt angle theta2.
[0026] Referring to Fig. 1, a housing 10A of the projector 10 is provided with a keystone
operation unit 12 disposed on the upper surface thereof such that the keystone
operation unit 12 can be operated in the right and left direction (direction orthogonal to
a projection direction). The keystone operation unit 12 functions as a manual operation
device for horizontal keystone correction. The keystone operation unit 12 includes an
operation member 12A, which includes a sliding variable resistor and which the user
can slide horizontally while holding with fingers. When the operation member 12A is
operated from one side to the other side in a sliding range, an output voltage changes in
proportion to the amount of operation (slide stroke) of the operation member 12A.
[0027] A constant power supply voltage VI (3.3 V in the present configuration) is applied to
the keystone operation unit 12. An output voltage changes depending on the position
of the operation member 12A of the keystone operation unit 12. In the present con
figuration, a horizontal keystone correction amount is set on the basis of the output
voltage. Consequently, the horizontal keystone correction amount is set by a user's
manual operation.
[0028] In the present configuration, an operation direction for adjustment of the horizontal
keystone correction amount is allowed to coincide with the right and left direction in
which the optical axis OA is tilted and horizontal keystone correction has to be
performed. Accordingly, the user can intuitively adjust the horizontal keystone
correction amount and also instinctively recognize the keystone operation unit 12 as an
operation unit for horizontal keystone correction amount.
[0029] Fig. 3 is a block diagram illustrating the functional configuration of the projector 10.
Referring to Fig. 3, the projector 10 includes an image processing unit 21, a keystone
correcting unit (trapezoidal distortion correcting unit) 22, a panel driving unit 23, an
image projecting unit 24 including a liquid crystal display panel 24A, a sensor unit 26,
a memory 27, and a control unit 30.
[0030] The image processing unit 2 1 receives an image signal SA from an external device
17, such as a personal computer or a DVD player, connected thereto via a cable. The
image processing unit 2 1 writes image data corresponding to the signal SA to a frame
buffer (not illustrated) on a frame-by-frame basis, and performs IP conversion to
convert the image data from the interlace format to the progressive format, resolution
conversion to enlarge or reduce the size of the IP-converted image data, and various
color corrections to control, for example, brightness and color saturation. The frame
buffer stores original image data output from the image processing unit 21, uncorrected
image data obtained by format-converting the original image data through the image
processing unit 21, and corrected image data obtained by performing keystone
correction on the uncorrected image data through the keystone correcting unit 22.
[0031] The keystone correcting unit 22 corrects a trapezoidal distortion caused when an
image is projected while the projection axis (corresponding to the optical axis OA of
projected light) of the projector 10 is tilted relative to the screen SC, namely, performs
vertical keystone correction and horizontal keystone correction. The keystone
correcting unit 22 includes a coordinate transformer 31 that performs transformation of
the coordinates for horizontal and/or vertical keystone correction and a filter (pixel in
terpolator) 32 that performs pixel interpolation associated with keystone correction.
[0032] To perform keystone correction, an image is displayed on the liquid crystal display
panel 24A such that the trapezoidal distortion is compensated for. When keystone
correction is typically performed in the projector including the liquid crystal display
panel, the liquid crystal display panel 24A displays an image smaller than an original
image to be subjected to trapezoidal distortion correction. Fundamentally, the original
image is reduced. If the original image is angled significantly, part of the image may
be enlarged.
[0033] For reduction of the original image, simply thinning image data results in a jagged
image. The filter 32 performs pixel interpolation to avoid jagged distortions. The filter
32 performs pixel interpolation on the basis of a filtering coefficient associated with
keystone correction. The coordinate transformer 31 and the filter 32 may include a
variety of known components.
[0034] The panel driving unit 23 drives the liquid crystal display panel 24A of the image
projecting unit 24. The panel driving unit 23 drives the liquid crystal display panel 24A
on the basis of corrected image data subjected to image processing (including keystone
correction) to display an image.
[0035] The image projecting unit 24 includes a light source device 25A functioning as a
light source, the liquid crystal display panel (also termed a liquid crystal light valve)
24A, and a projection lens 25B. The liquid crystal display panel 24A includes a
transmissive liquid crystal display panel including a plurality of pixels arranged in a
matrix. The liquid crystal display panel 24A is driven by the panel driving unit 23 such
that the transmittance ratio of each pixel is changed to modulate illumination light
from the light source to image light representing an image.
[0036] When the projector 10 is a 3-chip LCD projector, three liquid crystal display panels
24A for the three colors of red, green, and blue or RGB and mirrors and a prism for
splitting light from the light source device 25A and combining light are arranged. In
the present embodiment, the apparatus includes a single liquid crystal display panel
24A for the convenience of description.
[0037] The projection lens 25B enlarges and projects image light modulated by the liquid
crystal display panel 24A. An optical system of the image projecting unit 24 may
include a lens array for adjusting light distribution, a polarization adjusting element, a
mirror, a dustproof glass, and the like. The image projecting unit 24 may include a
variety of known components.
[0038] The sensor unit 26 functions as an angle detecting unit that detects a tilt angle in the
top and bottom direction (the vertical direction or the longitudinal direction) of the
projector 10, namely, the vertical tilt angle thetal illustrated in Fig. 2A. The sensor unit
26 includes a G-sensor (accelerometer) detecting the inclination of the projector 10
with respect to the vertical direction, detects the vertical tilt angle thetal using the Gsensor,
and transmits data indicating the detected vertical tilt angle thetal to the control
unit 30.
[0039] The memory 27 stores various programs, such as a control program, and various data
items. The memory 27 further stores conversion data 27A, which will be described
later.
[0040] The control unit 30 reads the control program stored in the memory 27 and executes
the program, thus functioning as a computer for controlling the components of the
projector 10.
[0041] Referring to Fig. 3, the projector 10 includes an analog-to-digital (A/D) converter 33
that converts an output voltage, which is in analog form, of the keystone operation unit
12 into digital form. A digital value indicating the output voltage is transmitted as an
operation output value Dl from the A/D converter 33 to the control unit 30. The
control unit 30 functions as a correction amount setting unit that sets a keystone
correction amount on the basis of the operation output value Dl.
[0042] In this case, the control unit 30 allows the keystone correcting unit 22 to perform an
automatic keystone correction process of automatically performing vertical keystone
correction on the basis of the vertical tilt angle thetal detected by the sensor unit 26
and a manual keystone correction process of performing horizontal keystone correction
on the basis of the operation output value Dl associated with the keystone operation
unit 12.
[0043] The projector 10 is configured such that information regarding a keystone correction
amount (for example, the current value of the keystone correction amount) is not
provided to the user, so that the user directs the projector 10 through the sliding
keystone operation unit 12 to perform horizontal keystone correction without relying
on an indication. More specifically, the user operates the operation member 12A of the
keystone operation unit 12 from side to side within an operation range to set a
horizontal keystone correction amount in the range of -30 degrees to +30 degrees (one
of the right and left ends is set to the minus end and the other end is set to the plus
end).
[0044] In this case, an equal assignment method may be used which sets a point at the
middle of the operation range to a zero position where the horizontal keystone
correction amount is zero, assigns a correction amount of -30 degrees to one end of the
operation range, assigns a correction amount of +30 degrees to the other end, and
equally assigns correction amounts for horizontal keystone angles excluding -30
degrees, 0 degree, and +30 degrees, to operation positions between these ends.
[0045] According to this equal assignment method, however, it is difficult for the user to
operate the operation member 12A to the single middle position where the keystone
correction amount is zero. If the user has intended to operate the operation member
12A to the zero position, the operation member 12A may be deviated from the zero
position. Such an event will be called a first event alpha where the operation member
12A is deviated from the zero position despite the user's intention.
[0046] For example, when the user accurately places the projector 10 such that the
horizontal tilt of the optical axis OA is zero, the user intends to operate the operation
member 12A to the zero position such that horizontal keystone correction is not
performed but the operation member 12A is slightly deviated from the zero position. In
this case, horizontal keystone correction is performed unnecessarily. It is therefore
preferable to avoid the first event alpha.
[0047] In addition, individual variations of the variable resistor in the keystone operation
unit 12, variation in the power supply voltage VI, temperature drift, and noise are
factors causing the first event alpha.
[0048] If the operation position of the operation member 12A of the keystone operation unit
12 is not changed, the operation output value Dl may vary due to variation in the
power supply voltage VI applied to the keystone operation unit 12, temperature drift,
and/or noise. In this case, an event in which the horizontal keystone correction amount
is changed despite the user's intention is caused. This event will be called a second
event beta where the horizontal keystone correction amount is changed due to a factor
other than operation. It is preferable to avoid the second event beta.
[0049] The projector 10 with the present configuration has the following countermeasures
against the first event alpha and the second event beta.
Countermeasure against First Event Alpha
[0050] According to this countermeasure, as illustrated in Fig. 4, the middle position in the
operation range, indicated at H, is set to a zero reference position C where the
horizontal keystone correction amount is zero, and a continuous region CH
(hereinafter, "central dead zone") including the zero reference position C and an area
surrounding the zero reference position C is set to a zone where the horizontal
keystone correction amount is zero.
[0051] Specifically, the operation range H of the keystone operation unit 12 in this coun
termeasure is 0.1m as illustrated in Fig. 4. An area extending from the zero reference
position C, which corresponds to the middle position at a distance of 0.05 m from each
end, to each side by a distance of 0.01 m is the central dead zone CH. Accordingly, if
the operation member 12A is positioned within the central dead zone CH, the
horizontal keystone correction amount is set to zero (corresponding to a horizontal
keystone angle of 0 degree). For example, when the operation member 12A is in a
position indicated at (I) or (II) in Fig. 4, the horizontal keystone correction amount is
set to zero.
[0052] A region (left operation region LH in Fig. 4) between one end (left end) of the central
dead zone CH and one end (left end) of the operation range H is allocated for ad
justment of horizontal keystone correction amounts of 0 to -30 degrees (up to a
maximum horizontal keystone angle on the one end).
[0053] In this region LH, as the operation member 12A moves to the one end, the horizontal
keystone correction amount continuously decreases. In this countermeasure, the
horizontal keystone correction amount decreases in proportion to the movement of the
operation member 12A toward the one end in the region LH. For example, if the
operation member 12A is in a position (III) in Fig. 4, the horizontal keystone
correction amount is set to a correction amount of -15 degrees.
[0054] A region (right operation region RH in Fig. 4) between the other end (right end) of
the central dead zone CH and the other end (right end) of the operation range H is
allocated for adjustment of horizontal keystone correction amounts of 0 to +30 degrees
(up to a maximum horizontal keystone angle on the other end).
[0055] In this region RH, as the operation member 12A moves to the other end, the
horizontal keystone correction amount continuously increases. In this countermeasure,
the horizontal keystone correction amount increases in proportion to the movement of
the operation member 12A to the other end in the region RH. For example, if the
operation member 12A is in a position (IV) in Fig. 4, the horizontal keystone
correction amount is set to a correction amount of +20 degrees.
[0056] The above-described allocation is achieved by previously storing the conversion data
27A (refer to Fig. 3) in table form, indicating the relationship between the operation
output value Dl of the keystone operation unit 12 and the horizontal keystone
correction amount, to the memory 27. More specifically, the control unit 30 refers to
the conversion data 27A to determine a horizontal keystone correction amount corre
sponding to the current operation output value Dl, and controls the keystone correcting
unit 22. The conversion data 27A is not limited to data in table form. The conversion
data 27A may be information (conversion data) indicating a relational expression in
dicating the relationship in Fig. 4.
[0057] Consequently, if the user operates the operation member 12A such that the operation
member 12A enters the central dead zone CH, the horizontal keystone correction
amount can be set to zero. As compared with a configuration in which the horizontal
keystone correction amount is set to zero at only the zero reference position C, the
horizontal keystone correction amount can be easily and reliably set to zero.
[0058] In this configuration, the operation direction for adjustment of the horizontal
keystone correction amount coincides with the right and left direction, serving as the
direction in which the optical axis OA is tilted and horizontal keystone correction has
to be performed. Accordingly, the user can intuitively adjust the horizontal keystone
correction amount.
[0059] Furthermore, according to this countermeasure, the projector 10 is provided with a
click mechanism 41, schematically illustrated in Fig. 3, which allows the keystone
operation unit 12 to provide a mechanical click state when the operation member 12A
of the keystone operation unit 12 is operated to the zero reference position C. The click
mechanism 4 1 is a mechanism which generates, for example, a sense of clicking and a
click using a spring material and a latching mechanism such that the user can recognize
a clicked position tactually and aurally. The click mechanism 4 1 may include a known
mechanism.
[0060] Since this kind of click mechanism 4 1 is a mechanical component, a position where
the sense of clicking is generated varies depending on the influence of an error, change
over time, or the like.
[0061] In this configuration, in the use of the click mechanism 41, the keystone operation
unit 12 provides the click state at least in the vicinity of the zero reference position C.
In other words, the keystone operation unit 12 reliably provides the click state within
the central dead zone CH. Accordingly, the user can reliably operate the operation
member 12A of the keystone operation unit 12 to the vicinity of the zero reference
position C, namely, into the central dead zone CH without relying on vision. The user
can therefore easily and reliably set the horizontal keystone correction amount to zero
while viewing an image projected by the projector 10 in a dark room.
[0062] The central dead zone CH is allocated to an area of 20% of the operation range H. If
individual variations of the variable resistor in the keystone operation unit 12, variation
in the power supply voltage VI, temperature drift, or noise occurs while the operation
member 12A of the keystone operation unit 12 is operated to the vicinity of the zero
reference position C, therefore, a variation in the operation output value Dl is not
beyond a voltage range, initially set, corresponding to the central dead zone CH.
[0063] Accordingly, if individual variations of the variable resistor in the keystone operation
unit 12, variation in the power supply voltage, temperature drift, or noise occurs, the
horizontal keystone correction amount can be held at zero.
[0064] The central dead zone CH is not limited to 20% of the operation range H. The central
dead zone CH may be below or above 20% of the operation range H such that a
variation in the operation output value Dl is not beyond the initial set range even when
individual variations of the variable resistor, variation in the power supply voltage VI,
temperature drift, or noise occurs. As described above, the countermeasure against the
first event alpha is provided.
Countermeasure against Second Event Beta
[0065] According to this countermeasure, the projector 10 has, as operation modes, an ad
justment mode in which the keystone correction amount is changed in accordance with
an operation of the keystone operation unit 12, i.e., the operation output value Dl as
described above and a non-adjustment mode in which the keystone correction amount
is fixed without depending on an operation of the keystone operation unit 12, i.e., the
operation output value Dl. The control unit 30 performs an operation mode switching
process.
[0066] Fig. 5 is a flowchart illustrating the operation mode switching process. Figs. 6A and
6B are diagrams explaining operations in these modes. The operation mode switching
process is repeated during turn-on of the projector 10. The operation mode switching
process may be stopped in accordance with setting by the user.
[0067] As a precondition of the operation mode switching process, while the keystone
operation unit 12 is not operated for predetermined set time (two seconds in this coun
termeasure) TO, namely, while the operation output value Dl of the keystone operation
unit 12 is not changed for the set time TOor more, the operation mode is switched to
the non-adjustment mode. Accordingly, if a state where the user does not operate the
keystone operation unit 12 continues, the operation mode is switched to the nonadjustment
mode. An operation in the non-adjustment mode will be described below.
[0068] In the non-adjustment mode, the control unit 30 fixes the keystone correction
amount. In Fig. 6A, the horizontal keystone correction amount is fixed to -15 degrees.
[0069] Referring to Fig. 5, in the non-adjustment mode, the control unit 30 detects an
operation of the keystone operation unit 12 (step SI) to determine whether an
operation has been performed such that the operation output value is beyond a prede
termined region (step S2). This operation means an operation performed such that the
operation output value Dl is beyond a continuous region (hereinafter, also referred to
as the "output-value-based dead zone") GH (refer to Fig. 6A) including the operation
output value Dl corresponding to the fixed keystone correction amount and an area
surrounding the output value. The output- value-based dead zone GH is set such that a
variation in the operation output value Dl is not beyond the dead zone GH even if
variation in the power supply voltage VI, temperature drift, or noise occurs. The
output- value-based dead zone GH is set so as to include a variation range of the
operation output value Dl.
[0070] For example, when a variation due to a factor (voltage variation, temperature drift, or
noise) other than operation is in the voltage range of -0.2 V to +0.2 V, the dead zone
GH is set to a variation range (of -0.2 V to +0.2 V) in which the operation output value
Dl is set to the center value (reference).
[0071] More specifically, the control unit 30 detects the operation output value Dl as
processing in step SI and determines, as processing in step S2, whether the operation
output value Dl is outside the output-value-based dead zone GH. If the value is inside
the output-value-based dead zone GH (NO in step S2), the control unit 30 returns the
process to step SI and maintains the current operation mode, i.e., the non-adjustment
mode until the operation output value Dl is beyond the output-value-based dead zone
GH.
[0072] Whereas, if the operation output value Dl is outside the output- value-based dead
zone GH (YES in step S2), the control unit 30 starts keystone adjustment (horizontal
keystone correction), namely, switches the operation mode to the adjustment mode
(step S3).
[0073] In the adjustment mode, the control unit 30 changes a horizontal keystone correction
amount in accordance with an operation of the keystone operation unit 12 (namely, the
operation output value Dl) to perform keystone adjustment (keystone correction) (step
S4). Then, the control unit 30 finishes the adjustment (correction) (step S5).
[0074] Subsequently, the control unit 30 determines whether the keystone operation unit 12
has been operated within a predetermined period, i.e., the set time (two seconds in this
countermeasure) TO (step S6). Specifically, the control unit 30 acquires the operation
output value Dl of the keystone operation unit 12 at time intervals and determines on
the basis of the difference between the previous and following operation output values
Dl whether the keystone operation unit 12 has been operated. If the keystone operation
unit 12 has been operated (YES in step S6), the control unit 30 returns the process to
step S3 to continue the keystone adjustment, namely, the adjustment mode.
[0075] Fig. 6B illustrates a case where a horizontal keystone correction amount of -5
degrees is set in the adjustment mode. In the adjustment mode, if the keystone
operation unit 12 is operated, the horizontal keystone correction amount is adjusted in
accordance with the position of the operation member 12A in steps S3 to S6. For
example, when the operation member 12A is positioned in an area corresponding to the
central dead zone CH, the horizontal keystone correction amount is set to zero. When
the operation member 12A is in the left end, the horizontal keystone correction amount
is set to -30 degrees. When the operation member 12A is in the right end, the
horizontal keystone correction amount is set to +30 degrees.
[0076] Whereas, if the keystone operation unit 12 has not been operated (NO in step S6), the
control unit 30 finishes the operation mode switching process. In this case, the fixed
keystone correction amount is kept, namely, the operation mode is switched to the nonadjustment
mode. At the completion of processing in step S6, the operation mode
switching process is restarted from step SI immediately or in accordance with an in
terruption signal output at predetermined interruption intervals. Thus, if an operation
has been performed such that the operation output value Dl is beyond the prede
termined region in the non-adjustment mode (YES in step S2), the operation mode is
switched to the adjustment mode, such that keystone correction can be performed.
[0077] As described above, if the keystone operation unit 12 has not been operated in the ad
justment mode, the operation mode is switched to the non-adjustment mode in which
the keystone correction amount is fixed. Even when the operation output value Dl
varies due to a factor (variation in the power supply voltage VI, temperature drift, or
noise) other than operation, such an event that the keystone correction amount is
changed can be avoided. As described above, the countermeasure against the second
event beta is provided.
[0078] In some cases, the output-value-based dead zone (first dead zone) GH, which is set in
the non-adjustment mode, overlaps the central dead zone (second dead zone) CH. In
this case, if the operation output value Dl enters the central dead zone CH because of a
factor (voltage variation, temperature drift, or noise) other than operation and the
keystone correction amount is adjusted to zero, an even in which the keystone
correction amount varies due to the factor other than operation.
[0079] According to this countermeasure, in order to avoid such an event, when the
operation output value Dl is inside the central dead zone CH in the adjustment mode,
the keystone correction amount is adjusted to zero. When the operation output value
Dl is inside the central dead zone CH in the non-adjustment mode, the control unit 30
fixes the keystone correction amount on the basis of the conversion data 27A without
setting the keystone correction amount to zero.
[0080] Accordingly, in the case where the operation output value Dl is inside the outputvalue
-based dead zone (first dead zone) GH and is also inside the central dead zone
(second dead zone) CH, the keystone correction amount is fixed in the non-adjustment
mode. In the adjustment mode, the keystone correction amount is adjusted to zero.
Consequently, the event in which the keystone correction amount is adjusted to zero
when the operation output value Dl enters the central dead zone CH because of a
factor other than operation can be avoided.
[0081] Control by the filter 32 will now be described. The filter 32 has a function of cal
culating a filtering coefficient for pixel interpolation and performing pixel interpolation
based on the filtering coefficient under the control of the control unit 30.
[0082] Fig. 7 is a flowchart of a control process of the filter 32. The control process is
performed when vertical keystone correction is not performed. Referring to Fig. 7,
when the operation mode is the adjustment mode (YES in step SI 1), the control unit 30
determines whether the keystone operation unit 12 has been operated outside the
central dead zone CH (step SI 2). In the non-adjustment mode (NO in step SI 1), the
control unit 30 terminates the process and again performs the process immediately or
in accordance with an interruption signal output at predetermined interruption
intervals.
[0083] When determining in step S12 that an operation has been performed outside the
central dead zone CH (YES in step S12), the control unit 30 allows the filter 32 to
calculate a filtering coefficient for pixel interpolation in accordance with a horizontal
keystone correction amount and perform pixel interpolation (step S13). Thus, pixel in
terpolation for horizontal keystone correction is performed.
[0084] Whereas, if an operation has been performed within the central dead zone CH (NO in
step S12), the control unit 30 allows the filter 32 to set a filtering coefficient to zero
(step S14). When a filtering coefficient of zero is set, an input of the filter 32 agrees
with an output thereof. Accordingly, filtering is not performed. In other words, pixel
interpolation is not performed (pixel interpolation is inhibited).
[0085] In the present configuration, therefore, when an operation has been performed within
the central dead zone CH, pixel interpolation can be inhibited while an image data
processing path is not changed. When vertical keystone correction is performed, this
process is not carried out and pixel interpolation according to vertical and horizontal
keystone corrections is performed. In some cases, pixel interpolation reduces jagged
distortions of an image but causes the image to be blurred. In the present configuration,
when an operation has been performed within the central dead zone CH, pixel inter
polation is inhibited. Accordingly, an input image can be faithfully displayed, thus
improving image quality.
[0086] As described above, in the present configuration, the control unit 30 sets the central
dead zone CH including the zero reference position C, serving as a single point within
the operation range of the keystone operation unit 12, and sets the horizontal keystone
correction amount to zero in accordance with the operation output value Dl corre
sponding to the inside of the central dead zone CH. Advantageously, the user can set
the horizontal keystone correction amount to zero without relying on an indication of
the horizontal keystone correction amount.
[0087] The keystone operation unit 12 includes a sliding variable resistor and allows the
variable resistor to change the operation output value Dl in accordance with the
amount of operation. The control unit 30 sets the horizontal keystone correction
amount to zero in accordance with the operation output value Dl within a voltage
range corresponding to the central dead zone CH. Advantageously, the horizontal
keystone correction amount can be easily set to zero using the variable resistor which
is inexpensive. In the use of the variable resistor, the operation output value D1 varies
due to individual variations of the resistor, voltage variation, temperature drift, or
noise. If the operation output value Dl varies, however, the variation is inside the
central dead zone CH. Advantageously, an event in which the horizontal keystone
correction amount changes from zero to another value despite user's intention can be
avoided.
[0088] The keystone operation unit 12 is slidable in the direction orthogonal to the
projection direction in which an image is projected by the image projecting unit 24.
Since the user operates the keystone operation unit 12 to adjust a horizontal keystone
correction amount in the direction orthogonal to the projection direction, the user can
adjust the horizontal keystone correction amount intuitively. Furthermore, the user can
instinctively recognize the keystone operation unit 12 as an operation unit for
horizontal keystone correction. In addition, since the keystone operation unit 12
provides a click state at the zero reference position C, serving as a specific operation
position within the central dead zone CH, the click state can be ensured within the
central dead zone CH using the mechanical click mechanism. Thus, the user can easily
and reliably set the horizontal keystone correction amount to zero without relying on
vision.
[0089] When the operation output value Dl of the keystone operation unit 12 is inside the
central dead zone CH, the filter 32 does not perform pixel interpolation. Accordingly,
when an operation is performed within the central dead zone CH, pixel interpolation
can be inhibited. An input image can be therefore displayed faithfully, thus improving
image quality.
[0090] In the present configuration, in the adjustment mode in which the horizontal keystone
correction amount is varied in accordance with the operation output value Dl of the
keystone operation unit 12, the control unit 30 monitors the operation output value Dl
to determine whether the keystone operation unit 12 has not been operated. If the
keystone operation unit 12 has not been operated, the control unit 30 switches the
operation mode to the non-adjustment mode in which the horizontal keystone
correction amount is fixed. Advantageously, an event in which the horizontal keystone
correction amount varies due to a factor (voltage variation, temperature drift, or noise)
other than a user's operation can be avoided.
[0091] Particularly, in the present configuration, the keystone operation unit 12 includes the
variable resistor whose output value tends to vary due to voltage variation, temperature
drift, or noise. The variation of the variable resistor can be adequately avoided. While
the inexpensive variable resistor is used, therefore, the event in which the horizontal
keystone correction amount changes due to a factor other than a user's operation can be
avoided.
[0092] In the present configuration, since keystone correction amount information is not
provided to the user, an event in which the user does not notice a change in keystone
correction amount caused by a factor other than operation may occur. The present
invention can, however, avoid such an event. In other words, the present invention is
suitable for a configuration in which keystone correction amount information is not
provided to the user.
[0093] In the present configuration, in the non-adjustment mode, the control unit 30 sets the
output-value-based dead zone (first dead zone) GH including the variation range of the
operation output value Dl. While the operation output value Dl is inside the outputvalue-
based dead zone GH, the horizontal keystone correction amount is fixed. When
the operation output value Dl is outside the output-value-based dead zone GH, the
operation mode is switched to the adjustment mode. While an event in which the
horizontal keystone correction amount changes due to a factor other than a user's
operation is avoided, the horizontal keystone correction amount can be adjusted in ac
cordance with a user's operation, thus improving ease of use.
[0094] The output-value-based dead zone GH is set on the basis of the operation output
value Dl obtained when the operation mode is switched to the non-adjustment mode.
Accordingly, a proper dead zone can be set such that the horizontal keystone correction
amount is not changed if the operation output value Dl varies due to a factor other than
an operation upon switching.
[0095] In the case where the operation output value Dl is inside the output-value-based dead
zone GH and is also inside the central dead zone (second dead zone) CH, the control
unit 30 fixes the horizontal keystone correction amount in the non-adjustment mode. In
the adjustment mode, the control unit 30 sets the horizontal keystone correction
amount to zero. While the keystone correction amount can be easily set to zero in the
adjustment mode, therefore, an event in which the horizontal keystone correction
amount is adjusted to zero if the operation output value Dl enters the central dead zone
CH because of a factor other than operation can be prevented.
[0096] The above-described embodiment is intended to merely describe an embodiment of
the present invention. Any modifications and applications can be made without
departing from the spirit of the present invention.
[0097] For example, in the above-described embodiment, the present invention is applied to
horizontal keystone correction. The present invention can be applied to vertical
keystone correction. The present invention can be applied widely to known keystone
correction.
[0098] In the above-described embodiment, the keystone operation unit 12 includes the
sliding variable resistor. The present invention is not limited to the embodiment. The
keystone operation unit 12 may include a rotary variable resistor or an operation device
other than a variable resistor.
[0099] In the above-described embodiment, the keystone operation unit 12 provides a click
state when operated to the zero reference position C. The present invention is not
limited to the embodiment. The keystone operation unit 12 may provide a click state in
a specific operation position other than the zero reference position C.
[0100] The above-described functional units, e.g., the image processing unit 21, the
keystone correcting unit 22, and the control unit 30 serve as functional components of
the projector 10. Concrete forms of them are not especially limited. In other words,
hardware corresponding to each functional unit does not always have to be installed. A
single processor may perform a program to realize functions of a plurality of functional
units.
[0101] The above-described projector 10 is of the type in which an image is projected onto
the screen SC using the transmissive liquid crystal display panel 24A. A projector with
a reflective liquid crystal display panel may be used. Alternatively, a DMD projector
with a digital micromirror device may be used. In addition to the 3-chip LCD projector
that projects a color image using three light valves, the present invention can be
applied to a projector that displays images corresponding RGB using a single liquid
crystal light valve in a time-division manner to project a color image, a single-chip
DMD projector including a color wheel, and a 3-chip DMD projector. As regards the
light source, any of various light sources, such as a xenon lamp, an ultra-high pressure
mercury lamp, an LED lamp, may be used. The above-described projector 10 may be
of the type which is disposed on the front side of the projection plane and projects
projection light to the front surface of the projection plane. Alternatively, the projector
10 may be of the type which is disposed on the rear side of the projection plane and
projects projection light to the rear surface of the projection plane. In other words, the
present invention can be applied widely to projection display apparatuses having a
function of modulating light emitted from a light source.
[0102] In the present embodiment, the image signal SA is supplied from the external device
17 to the projector 10. For example, the projector 10 may include a reading device that
reads data from an external recording medium, such as an optical disk or a flash
memory, and the reading device may read data stored in the recording medium to
acquire the image signal SA.
Reference Signs List
[0103] 10 Projector (projection display apparatus)
12 Keystone operation unit
12A Operation member
2 1 Image processing unit
22 Keystone correcting unit (trapezoidal distortion correcting unit)
23 Panel driving unit
24A Liquid crystal display panel
24 Image projecting unit
26 Sensor unit
27 Memory
30 Control unit (correction amount setting unit)
27A Conversion data
31 Coordinate transformer
32 Filter
33 A/D converter
4 1 Click mechanism
C Zero reference position
Dl Operation output value (output value)
CH Central dead zone (second dead zone)
GH Output-value-based dead zone (first dead zone)
WO 2012/035744 PCT/JP2011/005115

Claims
[Claim 1] A projection display apparatus comprising:
an image projecting unit that projects an image;
an operation unit whose output value changes depending on the amount
of operation;
a correction amount setting unit that changes a keystone correction
amount in accordance with an output value of the operation unit; and
a keystone correcting unit that performs keystone correction on an
image to be projected in accordance with the keystone correction
amount, wherein
a zero reference position in which the keystone correction amount is
zero is set within an operation range of the operation unit,
a dead zone, which includes the zero reference position and an area sur
rounding the zero reference position is set within the operation range of
the operation unit, and
the correction amount setting unit sets the keystone correction amount
to zero in accordance with the output value corresponding to the inside
of the dead zone.
[Claim 2] The apparatus according to Claim 1, wherein
the operation unit includes a sliding or rotary variable resistor and
allows the variable resistor to change an output voltage in accordance
with the operation amount, and
the correction amount setting unit sets the keystone correction amount
to zero in accordance with the output voltage within a voltage range
corresponding to the dead zone.
[Claim 3] The apparatus according to Claim 1 or 2, wherein
the operation unit is a sliding operation device capable of being
operated in a direction orthogonal to a projection direction in which an
image is projected by the image projecting unit, and
the correction amount setting unit sets a keystone correction amount in
the direction orthogonal to the projection direction.
[Claim 4] The apparatus according to any one of Claims 1 to 3, wherein the
projection display apparatus performs keystone correction without
providing information regarding the keystone correction amount to a
user.
[Claim 5] The apparatus according to any one of Claims 1 to 4, further
comprising:
WO 2012/035744 PCT/JP2011/005115
a filter that performs pixel interpolation on the image, wherein if the
output value corresponds to the inside of the dead zone, the filter does
not perform pixel interpolation, and if the output value corresponds to
the outside of the dead zone, the filter performs pixel interpolation.
[Claim 6] The apparatus according to any one of Claims 1 to 5, wherein the
operation unit provides a click state at a specific operation position
within the dead zone.
[Claim 7] The apparatus according to Claim 6, wherein the operation unit
provides the click state at the zero reference position.
[Claim 8] A method of controlling a projection display apparatus that projects an
image, the apparatus including an operation unit whose output value
changes depending on the amount of operation, the method comprising:
changing a keystone correction amount in accordance with an output
value of the operation unit;
performing keystone correction on an image to be projected in ac
cordance with the keystone correction amount;
setting a zero reference position, in which the keystone correction
amount is zero, within an operation range of the operation unit;
setting a dead zone within the operation range of the operation unit
such that the dead zone includes the zero reference position and an area
surrounding the zero reference position; and
setting the keystone correction amount to zero in accordance with the
output value corresponding to the inside of the dead zone.
[Claim 9] The method according to Claim 8, wherein
the operation unit includes a sliding or rotary variable resistor and an
output voltage is changed through the variable resistor in accordance
with the operation amount, and
the keystone correction amount is set to zero in accordance with the
output voltage within a voltage range corresponding to the dead zone.
[Claim 10] The method according to Claim 8 or 9, wherein
the projection display apparatus further includes an image projecting
unit,
the operation unit is a sliding operation device capable of being
operated in a direction orthogonal to a projection direction in which an
image is projected by the image projecting unit, and
a keystone correction amount is set in the direction orthogonal to the
projection direction.
[Claim 11] The method according to any one of Claims 8 to 10, wherein keystone
WO 2012/035744 PCT/JP2011/005115
correction is performed while information regarding the keystone
correction amount is not provided to a user.
[Claim 12] The method according to any one of Claims 8 to 11, wherein if the
output value corresponds to the inside of the dead zone, pixel inter
polation is not performed on the image, and if the output value cor
responds to the outside of the dead zone, pixel interpolation is
performed on the image.
[Claim 13] The method according to any one of Claims 8 to 12, wherein the
operation unit provides a click state at a specific operation position
within the dead zone.
[Claim 14] The method according to Claim 13, wherein the operation unit provides
the click state at the zero reference position.
[Claim 15] A projection display apparatus comprising:
an image projecting unit that projects an image;
an operation unit, whose output value changes depending on the
amount of operation, that is a sliding operation device capable of being
operated in a direction orthogonal to a projection direction in which the
image is projected by the image projecting unit;
a correction amount setting unit that sets a keystone correction amount
in the direction orthogonal to the projection direction, and changes the
keystone correction amount in accordance with an output value of the
operation unit; and
a keystone correcting unit that performs keystone correction on an
image to be projected in accordance with the keystone correction
amount.