JP2010010754A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of improving the visibility of an area made of pixels, having low brightness and an area made of pixels having high brightness. <P>SOLUTION: A setting section 220 sets a first contrast-intensifying function f<SB>1</SB>(Y<SB>IN</SB>) for converting a video input signal by video frames. When an average luminance Y<SB>AVG</SB>is lower than a center luminance Y<SB>CENTER</SB>, a correction section 230 allows a first inflection point Q<SB>1</SB>to shift so that luminance Y<SB>OUT</SB>of a video output signal becomes high. Meanwhile, when the average luminance Y<SB>AVG</SB>is higher than the center luminance Y<SB>CENTER</SB>, the correction section 230 allows a second inflection point Q<SB>2</SB>to shift so that the luminance Y<SB>OUT</SB>of the video output signal becomes low. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a display device that acquires a video output signal by converting a video input signal using a contrast enhancement function.

  First, in order to enhance contrast, a display device that acquires a video output signal by converting a video input signal using a contrast enhancement function is known. The contrast enhancement function is a function that converts the brightness level of a video input signal having a low brightness level to a lower level and converts the brightness level of a video input signal having a higher brightness level to a higher level. For example, when the vertical axis is a video output signal and the horizontal axis is a video input signal, the contrast enhancement function is on the low level side in an area defined by the vertical axis and the horizontal axis (hereinafter, input / output coordinate area). Has a first inflection point and a second inflection point provided on the high level side. That is, the contrast enhancement function has a shape that draws an S shape in the input / output coordinate area.

Here, the first inflection point is provided below the linear reference function g (Y _IN ) that defines the video input signal and the video output signal on a one-to-one basis. On the other hand, the second inflection point is provided above the linear reference function g (Y _IN ). Thereby, it is possible to enhance the contrast. Hereinafter, such a technique is referred to as a contrast enhancement technique.

  Secondly, there is also known a display device that acquires a video output signal by correcting a video input signal in accordance with an average value (APL; Average Picture Level) of a plurality of pixels constituting a video frame. The display device corrects the video input signal using an APL correction function. The APL correction function is a function that uniformly corrects the video input signal to the low level side or the high level side. Hereinafter, such a technique is referred to as an APL correction technique.

  Here, in contrast enhancement technology and APL correction technology, the gradation of pixels with low brightness level disappears (so-called “blackout”), and the gradation of pixels with high brightness level disappears. (So-called “white jump”) is a problem.

In the APL correction technique, a technique for suppressing “blackout” and “whiteout” has been proposed (for example, Patent Document 1). Specifically, in order to suppress “blackout”, a low level correction function is applied to a video input signal having a low brightness level instead of an APL correction function. The low level correction function has a uniform slope in the input / output coordinate region. On the other hand, in order to suppress “overexposure”, not the APL correction function but the high level correction function is applied to the video input signal having a high brightness level. The high level correction function has a uniform slope in the input / output coordinate region.
JP 2006-311102 A

  Here, in the contrast enhancement technique, for example, the luminance is used as an index indicating the brightness level, and the first inflection point and the second inflection point are determined according to the average luminance or the central luminance of the video input signal constituting the video frame. It is conceivable to change the position of the music point. According to this, the contrast enhancement function is set so that “complete blackout” in which the gradation of the low-luminance pixel is completely eliminated and “complete whiteout” in which the gradation of the high-luminance pixel is completely eliminated are not generated. It is possible. On the other hand, “blackout” in which the gradation of low-luminance pixels is reduced and “whiteout” in which gradation of high-luminance pixels is reduced may occur.

  As described above, in the contrast enhancement technique described above, when the average luminance of the plurality of pixels constituting the video frame is low, the tone of the low luminance pixel is reduced by “blackout”, which is configured by low luminance pixels. There is a problem that the visibility of the area to be reduced is lowered. On the other hand, when the average brightness of a plurality of pixels that make up a video frame is high, the “whiteout” that reduces the gradation of the high-brightness pixels reduces the visibility of the area that consists of high-brightness pixels. There is a problem of end.

  Such a problem also occurs when the brightness of the HSV color space defined by the hue (H), saturation (S), and brightness (V) is used as an index indicating the brightness level.

  Accordingly, the present invention has been made to solve the above-described problems, and improves the visibility of an area constituted by pixels having a low brightness level and an area constituted by pixels having a high brightness level. It is an object of the present invention to provide a display device that can be made to operate.

  The display device according to the first feature corrects the first contrast enhancement function based on a setting unit that sets a first contrast enhancement function for converting the video input signal and a brightness level obtained from the video input signal. A correction unit that obtains the second contrast enhancement function, and a conversion unit that obtains the video output signal by converting the video input signal using the second contrast enhancement function. The first contrast enhancement function has a first inflection point or a second inflection point. The first inflection point is an inflection point provided at a position where the video input signal is converted so that the brightness level of the video output signal is lower than the brightness level of the video input signal. The second inflection point is an inflection point provided at a position where the video input signal is converted so that the brightness level of the video output signal is higher than the brightness level of the video input signal.

  According to this feature, the first contrast enhancement function having the first inflection point or the second inflection point is corrected based on the brightness level of the video input signal. Therefore, it is possible to enhance the contrast of the video frame, and to suppress a reduction in visibility in a region constituted by pixels having a low brightness level or a region constituted by pixels having a high brightness level.

  The correction unit according to the first feature shifts the first inflection point so that the brightness level of the video output signal becomes higher when the brightness level of the video input signal is lower than the predetermined brightness. The second contrast enhancement function is obtained.

  The correction unit according to the first feature shifts the second inflection point so that the brightness level of the video output signal is lowered when the brightness level of the video input signal is higher than the predetermined brightness. The second contrast enhancement function is obtained.

  In the display device according to the first feature, as the brightness level of the video input signal is lower than the predetermined brightness, the conversion amount for converting the video input signal by the first contrast enhancement function is reduced, and the correction unit performs the first conversion. The image processing apparatus further includes a control unit that increases a correction amount for correcting the one contrast enhancement function.

  In the display device according to the first feature, as the brightness level of the video input signal is higher than the predetermined brightness, the conversion amount for converting the video input signal by the first contrast enhancement function is reduced, and the correction unit performs the first conversion. The image processing apparatus further includes a control unit that increases a correction amount for correcting the one contrast enhancement function.

  The setting unit according to the first feature sets the first inflection point or the second inflection point based on the brightness level of the video input signal.

  ADVANTAGE OF THE INVENTION According to this invention, the display apparatus which makes it possible to improve the visibility of the area | region comprised with a pixel with a low brightness level, and the area | region comprised with a pixel with a high brightness level can be provided. .

  Hereinafter, a projection display apparatus according to an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Therefore, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

[First Embodiment]
(Configuration of projection display device)
Hereinafter, the configuration of the projection display apparatus according to the first embodiment will be described with reference to the drawings. FIG. 1 is a diagram showing a projection display apparatus 100 according to the first embodiment.

  As shown in FIG. 1, the projection display apparatus 100 includes a light source 10, a UV / IR cut filter 20, a fly-eye lens unit 30, a PBS array 40, and a plurality of liquid crystal panels 50 (a liquid crystal panel 50R, a liquid crystal). Panel 50G, liquid crystal panel 50B), cross dichroic prism 60, and projection lens unit 70.

  The light source 10 is a UHP lamp that emits white light. The light emitted from the light source 10 includes red component light, green component light, and blue component light.

  The UV / IR cut filter 20 transmits visible light components (red component light, green component light, and blue component light). On the other hand, the UV / IR cut filter 20 blocks out-of-sight light components (for example, infrared components and ultraviolet components).

  The fly-eye lens unit 30 makes the light emitted from the light source 10 uniform. Specifically, the fly eye lens unit 30 includes a fly eye lens 30a and a fly eye lens 30b.

  The fly-eye lens 30a and the fly-eye lens 30b are each composed of a plurality of minute lenses. Each microlens condenses the light emitted from the light source 10 so that the light emitted from the light source 10 is irradiated on the entire surface of the liquid crystal panel 50.

  The PBS array 40 aligns the polarization state of the light emitted from the fly-eye lens unit 30. For example, the PBS array 40 aligns the light emitted from the fly-eye lens unit 30 with S-polarized light.

  The liquid crystal panel 50R modulates the red component light by rotating the polarization direction of the red component light. On the light incident surface side of the liquid crystal panel 50R, a compensation plate 51R that suppresses light diffusion and improves the contrast ratio and transmittance is provided.

  An incident-side polarizing plate 52R that transmits light having one polarization direction (for example, P-polarized light) and shields light having another polarization direction (for example, S-polarized light) on the light incident surface side of the compensation plate 51R. Is provided. On the light incident surface side of the incident-side polarizing plate 52R, an incident-side pre-polarizing plate 53R that reduces the amount of light incident on the incident-side polarizing plate 52R and the thermal burden is provided.

  On the other hand, on the light exit surface side of the liquid crystal panel 50R, an exit-side pre-polarizer 54R that reduces the amount of light incident on an exit-side polarizer 55R, which will be described later, and the thermal burden is provided. On the light exit surface side of the exit side pre-polarizing plate 54R, the exit side that blocks light having one polarization direction (for example, P polarization) and transmits light having another polarization direction (for example, S polarization). A polarizing plate 55R is provided.

  Similarly, the liquid crystal panel 50G modulates the green component light by rotating the polarization direction of the green component light. A compensation plate 51G, an incident side polarizing plate 52G, and an incident side pre-polarizing plate 53G are provided on the light incident surface side of the liquid crystal panel 50G. On the other hand, an exit side pre-polarizing plate 54G and an exit side polarizing plate 55G are provided on the light exit surface side of the liquid crystal panel 50G.

  Similarly, the liquid crystal panel 50B modulates the blue component light by rotating the polarization direction of the blue component light. A compensation plate 51B, an incident side polarizing plate 52B, and an incident side pre-polarizing plate 53B are provided on the light incident surface side of the liquid crystal panel 50B. On the other hand, an emission side pre-polarizing plate 54B and an emission side polarizing plate 55B are provided on the light emission surface side of the liquid crystal panel 50B.

  The cross dichroic prism 60 combines light emitted from the liquid crystal panel 50R, the liquid crystal panel 50G, and the liquid crystal panel 50B. The cross dichroic prism 60 emits combined light to the projection lens unit 70 side.

  The projection lens unit 70 projects the combined light (image light) emitted from the cross dichroic prism 60 onto a screen or the like.

  Further, the projection display apparatus 100 includes a mirror group (dichroic mirror 111, dichroic mirror 112, reflection mirror 121 to reflection mirror 123) and lens group (condenser lens 131 to condenser lens 133, condenser lens 140R, condenser lens 140G, A condenser lens 140B, a relay lens 151 to a relay lens 153).

  The dichroic mirror 111 transmits red component light out of the light emitted from the PBS array 40. The dichroic mirror 111 reflects green component light and blue component light in the light emitted from the PBS array 40.

  The dichroic mirror 112 transmits blue component light out of the light reflected by the dichroic mirror 111. The dichroic mirror 112 reflects green component light out of the light reflected by the dichroic mirror 111.

  The reflection mirror 121 reflects the red component light and guides the red component light to the liquid crystal panel 50R side. The reflection mirror 122 and the reflection mirror 123 reflect the blue component light and guide the blue component light to the liquid crystal panel 50B side.

  The condenser lens 131 is a lens that collects white light emitted from the light source 10. The condenser lens 132 condenses the red component light that has passed through the dichroic mirror 111. The condenser lens 133 condenses the green component light and the blue component light reflected by the dichroic mirror 111.

  The condenser lens 140R collimates the red component light so that the liquid crystal panel 50R is irradiated with the red component light. The condenser lens 140G collimates the green component light so that the liquid crystal panel 50G is irradiated with the green component light. The condenser lens 140B makes the blue component light substantially parallel so that the liquid crystal panel 50B is irradiated with the blue component light. A UV cut filter 21 that shields the ultraviolet component is provided on the light exit surface side of the condenser lens.

  The relay lenses 151 to 153 substantially form an image of the blue component light on the liquid crystal panel 50B while suppressing the expansion of the blue component light.

(Function of projection display device)
Hereinafter, functions of the projection display apparatus according to the first embodiment will be described with reference to the drawings. FIG. 2 is a block diagram showing a configuration of the projection display apparatus 100 (signal processing apparatus 200) according to the first embodiment.

The signal processing device 200 acquires a video input signal including a red input signal Rin, a green input signal Gin, and a blue input signal Bin. The signal processing device 200 outputs a video output signal including a red output signal Rout, a green output signal Gout, and a blue output signal Bout. The signal values of the red input signal Rin, the green input signal Gin, and the blue input signal Bin are the minimum value Rin _MIN , Gin _MIN , Bin _MIN (for example, “0”) to the maximum value Rin _MAX , Gin _MAX , Bin, respectively. It is a value in the range of _MAX (for example, “255”). Similarly, the signal values of the red output signal Rout, the green output signal Gout, and the blue output signal Bout are respectively the minimum value Rout _MIN , Gout _MIN , Bout _MIN (for example, “0”) to the maximum value Rout _MAX , Gout _MAX , A value in a range of Bout _MAX (for example, “255”).

In the first embodiment, description will be given using “brightness” of each of the video input signal and the video output signal as one index indicating the “brightness level” of each of the video input signal and the video output signal. Here, the luminance is a value obtained by multiplying signal values of Rin, Gin, and Bin at a certain ratio, and ranges from the minimum luminance Y _MIN (for example, “0”) to the maximum luminance Y _MAX (for example, “255”). Is the value of

  As illustrated in FIG. 2, the signal processing device 200 includes a GAIN acquisition unit 210, a setting unit 220, a correction unit 230, and a conversion unit 240.

As shown in FIG. 3, the GAIN acquisition unit 210 frequency-distributes the frequency of the luminance Y _IN obtained from the video input signal. Accordingly, the GAIN acquisition unit 210 acquires the average luminance Y _AVG , the central luminance Y _CENTER , the first reference luminance Y _1, and the second reference luminance Y ₂ of the video input signal. The GAIN acquisition unit 210 calculates, for example, a region P including a predetermined number of pixels (for example, 80% of the total number of pixels) around the average luminance Y _AVG , so that the first reference luminance Y ₁ and the second reference luminance are calculated. to set the Y _2. Thus, the luminance Y _IN of the video input signal is divided into a low luminance region Y _{MIN to} Y ₁ , an intermediate luminance region Y _{1 to} Y ₂ , and a high luminance region Y _{2 to} Y _MAX .

Here, GAIN acquisition unit 210 sets the conversion amount to convert a video input signal by the first contrast enhancement function _{f 1} to be described later _{(Y IN).} Specifically, GAIN acquisition unit 210, as shown in FIG. 4, in accordance with the variance S of the luminance in the intermediate luminance region _Y 1 to Y _2, a first conversion gain GAIN ₁ and the second conversion gain GAIN ₂ get. The first conversion gain GAIN ₁ is a negative value, and increases as the variance value S increases. The first conversion gain GAIN ₁ is maintained at the maximum value (= 0) when the variance value S exceeds the threshold value Th1. The second conversion gain GAIN ₂ is a positive value, and the smaller the variance value S, the smaller the value. The second conversion gain GAIN ₂ is kept at the minimum value (= 0) when the variance value S exceeds the threshold Th1.

The GAIN acquisition unit 210 sets a correction amount for correcting a first contrast enhancement function f ₁ (Y _IN ) described later. Specifically, the GAIN acquisition unit 210 acquires the correction gain GAIN _H according to the average luminance Y _AVG as shown in FIG. The correction gain GAIN _H is 0 when the average luminance Y _AVG is equal to the central luminance Y _CENTER . The correction gain GAIN _H increases as the average luminance Y _AVG is lower than the central luminance Y _CENTER . In this case, the correction gain GAIN _H is a value in the range of 0 to the maximum value (> 0). The correction gain GAIN _H becomes smaller as the average luminance Y _AVG is higher than the central luminance Y _CENTER . In this case, the correction gain GAIN _H is a value in the range of 0 to the minimum value (<0). Thus, the absolute value of the correction gain GAIN _H increases as the average luminance Y _AVG becomes farther from the central luminance Y _CENTER . In the first embodiment, as shown in FIG. 3, since the average luminance Y _AVG is lower than the central luminance Y _CENTER , the correction gain GAIN _H is a positive value.

The setting unit 220 sets the first contrast enhancement function f ₁ (Y _IN ) for converting the video input signal for each video frame. FIG. 6 is a diagram illustrating the first contrast enhancement function f ₁ (Y _IN ) in the input / output coordinate area. The input / output coordinate area is defined by a horizontal axis indicating the luminance Y _IN of the video input signal and a vertical axis indicating the luminance Y _OUT of the video output signal.

The setting unit 220 sets a first contrast enhancement function f ₁ (Y _IN ) having an S shape as shown in FIG. Specifically, the first contrast enhancement function f ₁ (Y _IN ) is a two-point line graph having a first inflection point Q ₁ and a second inflection point Q ₂ in the input / output coordinate region. The first inflection point Q ₁ represents a video output signal is the inflection point which is positioned to convert a video input signal such that the luminance lower than the video input signal. The second inflection point Q ₂ is an inflection point video output signal is provided at a position which converts the video input signal such that the luminance higher than the video input signal. As described above, the first contrast enhancement function f ₁ (Y _IN ) further converts the low-brightness video input signal to the low-brightness side and further converts the high-brightness video input signal to the high-brightness side.

Setting unit 220, based on the luminance Y _IN obtained from the video input signal is set to the first inflection point Q _1, and a second inflection point Q _2. Specifically, the setting unit 220, based on a first conversion gain GAIN ₁ and the second conversion gain GAIN ₂ acquired by the GAIN acquisition unit 210, the first inflection point to _{Q 1} coordinate (Y _{1, f 1} (Y ₁ )) and the coordinates (Y ₂ , f ₁ (Y ₂ )) of the second inflection point Q ₂ are set. Here, the vertical coordinate f ₁ (Y ₁ ) of the first inflection point Q ₁ is the sum of the first reference luminance Y ₁ and the first conversion gain GAIN ₁ (<0). The vertical coordinate f ₁ (Y ₂ ) of the second inflection point Q ₂ is the sum of the second reference luminance Y ₂ and the second conversion gain GAIN ₂ (> 0). Accordingly, the slope of the first contrast enhancement function f ₁ (Y _IN ) in the intermediate luminance range Y _{1 to} Y ₂ is 1 (linear reference function) as the absolute values of the first conversion gain GAIN ₁ and the second conversion gain GAIN ₂ increase. g (Y _IN ) slope).

Thus, the first inflection point Q ₁ is located lower than the linear criterion function g (Y _IN). On the other hand, the second inflection point Q ₂ are located above the linear criterion function g (Y _IN). Therefore, the gradation of the region constituted by the pixels in the intermediate luminance region Y _{1 to} Y _{2 in} the video frame is expanded to f ₁ (Y ₁ ) to f ₁ (Y ₂ ). As a result, the visibility of the area formed by the pixels in the intermediate luminance area Y _{1 to} Y ₂ is improved. On the other hand, the gradation region constituted by pixels the low brightness area _{Y MIN} to Y ₁ is compressed _{Y MIN ~f 1 (Y 1)} , composed of pixels of the high brightness area _Y 2 to Y _MAX The gradation of the area is compressed to f ₁ (Y ₂ ) to Y _MAX . As a result, the visibility of the region constituted by the pixels in the low luminance region Y _{MIN to} Y _{1 and} the pixels in the high luminance region Y _{2 to} Y _MAX is lowered. In the first embodiment, as shown in FIG. 3, since the average luminance Y _{AVG of the} pixels constituting the video frame is biased toward the low luminance side, it is configured by pixels in the low luminance region Y _{MIN to} Y _1. “Blackout” tends to occur in the area.

The correction unit 230 corrects the first contrast enhancement function f ₁ (Y _IN ) based on the luminance Y _IN obtained from the video input signal, and acquires the second contrast enhancement function f ₂ (Y _IN ). Specifically, the correction unit 230 sets a correction function h (Y _IN ) based on the correction gain GAIN _H. FIG. 7 is a diagram showing the correction function h (Y _IN ) in the input / output coordinate area. As shown in FIG. 7, the correction function h (Y _IN ) is a one-point line graph having a corrected inflection point R in the input / output coordinate area.

The correction unit 230 sets the coordinates (Y _AVG , h (Y _AVG )) of the correction inflection point R based on the average luminance Y _AVG and the correction gain GAIN _H. The vertical coordinate h (Y _AVG ) of the correction inflection point R is the sum of the average luminance Y _AVG and the correction gain GAIN _H. In the first embodiment, as shown in FIG. 5, since the correction gain GAIN _H is a positive value, the correction inflection point R is located above the linear reference function g (Y _IN ).

Next, the correction unit 230 corrects the first contrast enhancement function f ₁ (Y _IN ) based on the correction function h (Y _IN ). Specifically, the correction unit 230 acquires the second contrast enhancement function f ₂ (Y _IN ) according to the following equation (1).
f ₂ (Y _IN ) = f ₁ (Y _IN ) × h (Y _IN ) × Y _IN (1)

Here, as described above, the correction function h (Y _IN ) is set based on the correction gain GAIN _H. Correction gain GAIN _H, the average luminance _{Y AVG} becomes lower than the center luminance _{Y CENTER} a positive value, an average luminance _{Y AVG} is higher than the center luminance _{Y CENTER} a negative value. Accordingly, the correction unit 230, the average luminance _{Y AVG} is lower than the center luminance _{Y CENTER,} shifts the first inflection point _{Q 1} as the video output signal is high luminance. That is, the correction unit 230, the input / output coordinate area, shifts the first inflection point Q ₁ upward. On the other hand, the correction unit 230, when the average luminance _{Y AVG} is higher than the center luminance _{Y CENTER,} shifts the second inflection point _{Q 2} as a video output signal has a low luminance. That is, the correction unit 230, the input / output coordinate area, shifts the second inflection point Q ₂ downward.

FIG. 8 is a diagram illustrating the second contrast enhancement function f ₂ (Y _IN ) in the input / output coordinate area. In the first embodiment, the average luminance _{Y AVG} is lower than the center luminance _{Y CENTER,} correcting unit 230, as shown in FIG. 8, shifts the first inflection point _{Q 1} upward.

The converter 240 converts the video input signal using the second contrast enhancement function f ₂ (Y _IN ) to obtain a video output signal. That is, the conversion unit 240 calculates the luminance Y _OUT of the video output signal by converting the luminance Y _IN of the video input signal using the second contrast enhancement function f ₂ (Y _IN ).

(Operation of projection display device)
Hereinafter, the operation of the projection display apparatus according to the first embodiment will be described with reference to the drawings. FIG. 9 is a flowchart showing the operation of the projection display apparatus 100 (signal processing apparatus 200) according to the first embodiment.

As shown in FIG. 9, in step 10, the signal processing device 200 sets a first contrast enhancement function f ₁ (Y _IN ) for converting the luminance Y _IN obtained from the video input signal.

In step 11, the signal processing device 200 sets a correction function h (Y _IN ) based on the luminance Y _IN obtained from the video input signal.

In step 12, the signal processing apparatus 200 corrects the first contrast enhancement function f ₁ (Y _IN ) with the correction function h (Y _IN ) to obtain the second contrast enhancement function f ₂ (Y _IN ).

In step 13, the signal processing device 200 converts the video input signal using the second contrast enhancement function f ₂ (Y _IN ) to obtain a video output signal.

(Function and effect)
In the first embodiment, the setting unit 220 sets a first contrast enhancement function f ₁ (Y _IN ) for converting a video input signal for each video frame. Thus, it is possible to improve the visibility of the region constituted by pixels the intermediate brightness area Y ₁ to Y ₂ in the video frame.

Here, the correction unit 230, when the average luminance _{Y AVG} is lower than the center luminance _{Y CENTER,} shifts the first inflection point _{Q 1} as luminance _{Y OUT} of the video output signal is high luminance. Therefore, a low luminance level region Y _MIN to Y ₁ of the pixel is reduced by "underexposure", it is possible to suppress the visibility of the region constituted by pixels the low brightness area Y _MIN to Y ₁ is reduced.

On the other hand, the correction unit 230, the average luminance _{Y AVG} is higher than the center luminance _{Y CENTER,} shifts the second inflection point _{Q 2} as luminance _{Y OUT} of the video output signal has a low luminance. Therefore, it is possible to suppress the by the high luminance region Y ₂ to Y gradations _MAX shrink "overexposed", the visibility of the area formed by the pixel of the high luminance region Y ₂ to Y _MAX decreases.

Therefore, the visibility of the region constituted by the pixels in the intermediate luminance region Y _{1 to} Y ₂ is improved, and the region constituted by the pixels in the low luminance region Y _{MIN to} Y ₁ and the high luminance region Y _{2 to} Y _MAX are improved. The visibility of the area formed by the pixels can be improved.

[Second Embodiment]
Hereinafter, the second embodiment will be described with reference to the drawings. In the following, differences between the first embodiment and the second embodiment described above will be mainly described.

Specifically, in the second embodiment, the signal processing device 200 further includes a control unit 250. The control unit 20 sets the conversion gain contribution degree (α) and the correction gain contribution degree (1−α) based on the luminance Y _IN that is prominent in the video input signal.

(Function of projection display device)
As shown in FIG. 10, the GAIN acquisition unit 210 frequency-distributes the frequency of the luminance Y _IN obtained from the video input signal. The GAIN acquisition unit 210 acquires the average luminance Y _AVG , the central luminance Y _CENTER , the first reference luminance Y ₁ , and the second reference luminance Y ₂ of the video input signal, as in the first embodiment described above. In the second embodiment, the average luminance Y _AVG is biased toward the high luminance side.

Next, the GAIN acquisition unit 210 acquires the first conversion gain GAIN ₁ and the second conversion gain GAIN ₂ according to the luminance dispersion value S in the intermediate luminance range Y _{1 to} Y ₂ (see FIG. 4).

The GAIN acquisition unit 210 acquires a correction gain GAIN _H according to the average luminance Y _AVG (see FIG. 5). In the second embodiment, as shown in FIG. 11, since the average luminance Y _AVG is higher than the central luminance Y _CENTER , the correction gain GAIN _H is a negative value.

The controller 210 sets the conversion gain contribution (α) and the correction gain contribution (1−α) according to the average luminance Y _AVG . Specifically, as shown in FIG. 12, the control unit 210 sets the conversion gain contribution (α) according to the average luminance Y _AVG . As shown in FIG. 11, the conversion gain contribution (α) has a maximum value (= 1) when the average luminance Y _AVG is equal to the central luminance Y _CENTER . The conversion gain contribution (α) becomes smaller as the average luminance Y _AVG is lower than the central luminance Y _CENTER, and becomes the minimum value (= 0) at the lowest luminance Y _MIN . On the other hand, the conversion gain contribution (α) becomes smaller as the average luminance Y _AVG is higher than the central luminance Y _CENTER, and becomes the minimum value (= 0) at the highest luminance Y _MAX .

In other words, as the average luminance Y _AVG is lower than the central luminance Y _CENTER , the control unit 210 reduces the conversion amount for converting the video input signal by the first contrast enhancement function f ₁ (Y _IN ), and the first contrast. The correction amount for correcting the enhancement function f ₁ (Y _IN ) is increased. Similarly, as the average luminance Y _AVG is higher than the central luminance Y _CENTER , the control unit 210 reduces the conversion amount for converting the video input signal by the first contrast enhancement function f ₁ (Y _IN ), and the first contrast enhancement. The correction amount for correcting the function f ₁ (Y _IN ) is increased.

As illustrated in FIG. 13, the setting unit 220 sets the first contrast enhancement function f ₁ (Y _IN ) for each video frame. Specifically, the setting unit 220, the conversion gain contribution (alpha), on the basis of the first conversion gain GAIN ₁ and the second conversion gain GAIN _2, first inflection point to _{Q 1} coordinate (Y _{1, f 1} (Y ₁ )) and the coordinates (Y ₂ , f ₁ (Y ₂ )) of the second inflection point Q ₂ are set.

Here, in the second embodiment, the vertical coordinate f ₁ (Y ₁ ) of the first inflection point Q ₁ is the product of the conversion gain contribution (α) and the first conversion gain GAIN ₁ (<0), is the sum of the first reference luminance Y _1. The vertical coordinate f ₁ (Y ₂ ) of the second inflection point Q ₂ is the product of the conversion gain contribution (α) and the second conversion gain GAIN ₂ (> 0) and the second reference luminance Y ₂ . It is sum. In the second embodiment, since the average luminance Y _AVG is biased toward the high luminance side, “out-of-white” is likely to occur in a region constituted by pixels in the high luminance region Y _{2 to} Y _MAX .

The correction unit 230 sets a correction function h (Y _IN ) as shown in FIG. Specifically, the correction unit 230 sets the coordinates (Y _AVG , h (Y _AVG )) of the correction inflection point R based on the correction gain contribution (1-α) and the correction gain GAIN _H. The vertical coordinate h (Y _AVG ) of the correction inflection point R is the sum of the product of the correction gain contribution (1-α) and the correction gain GAIN _H and the average luminance Y _AVG . In the second embodiment, since the correction gain GAIN _H is a negative value, the correction inflection point R is located below the linear reference function g (Y _IN ).

Next, as illustrated in FIG. 15, the correction unit 230 acquires the second contrast enhancement function f ₂ (Y _IN ) according to the above equation (1). In the second embodiment, since the average luminance _{Y AVG} is higher than the center luminance _{Y CENTER,} correcting unit 230, as shown in FIG. 15, shift the second inflection point _{Q 2} as a video output signal has a low brightness To do. That is, the correction unit 230, the input / output coordinate area, shifts the second inflection point Q ₂ downward.

The converter 240 converts the video input signal using the second contrast enhancement function f ₂ (Y _IN ) to obtain a video output signal.

(Function and effect)
In the second embodiment, the control unit 210 sets the conversion gain contribution (α) and the correction gain contribution (1−α) according to the average luminance Y _AVG . Specifically, the control unit 210 decreases the conversion gain contribution (α) and increases the correction gain contribution (1−α) as the average luminance Y _AVG is further away from the central luminance Y _CENTER .

Thus, the control unit 210 increases the conversion gain contribution (α) as the average luminance Y _AVG is closer to the central luminance Y _CENTER . Therefore, it is possible to further improve the visibility in a region constituted by pixels in the intermediate luminance range Y _{1 to} Y _{2 in} the video frame.

On the other hand, the control unit 210 increases the correction gain contribution (1−α) as the average luminance Y _AVG is farther from the central luminance Y _CENTER . Therefore, it is possible to further suppress a decrease in visibility in an area configured by pixels of the low luminance area Y _{MIN to} Y ₁ and the high luminance area Y _{2 to} Y _MAX .

[Other Embodiments]
Although the present invention has been described with reference to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

In the embodiment described above, the first contrast enhancement function f ₁ (Y _IN ) has two inflection points, but the first contrast enhancement function f ₁ (Y _IN ) has at least one inflection point. It only has to have. For example, as shown in FIG. 16, when the luminance Y _IN of the video input signal is concentrated in the vicinity of the lowest luminance Y _MIN , the control unit 210 can set one reference luminance Y ₀ . In this case, the first contrast enhancement function f _{1 (Y IN),} as shown in FIG. 17, a single point line graph with one inflection point Q _0. On the other hand, although not shown, when the control unit 210 sets three or more reference luminances Y ₀ , the first contrast enhancement function f ₁ (Y _IN ) has three or more inflection points.

In the embodiment described above, the conversion amount of the first contrast enhancement function f _{1 (Y IN),} and the correction amount of the first contrast enhancement function f _{1 (Y IN)} is based on the average luminance Y _AVG of the video input signal control However, the present invention is not limited to this. The conversion amount and the correction amount may be controlled based on, for example, the median value of the highest luminance and the lowest luminance of a plurality of pixels constituting the video frame.

In the above-described embodiment, the “brightness” of each of the video input signal and the video output signal has been described as one index indicating the “brightness level” of each of the video input signal and the video output signal. It is not a thing. For example, the “brightness” of the HSV color space defined by the hue (H), the saturation (S), and the lightness (V) may be used as an index indicating the “brightness level”. Specifically, the correction unit 230 corrects the first contrast enhancement function f ₁ (Y _IN ) based on the lightness distribution, the average lightness, the central lightness, and the like, so that the second contrast enhancement function f ₂ (Y _IN ). Can be obtained.

  In the above-described embodiments, the projection display apparatus 100 (for example, a projector) has been described. However, the present invention is not limited to this. The present invention can be applied to commonly used displays.

Although not particularly mentioned in the above-described embodiment, the signal processing apparatus 200 applies the second contrast enhancement function f ₂ (Y _IN ) to a video frame different from the video frame from which the first contrast enhancement function f ₁ (Y _IN ) is acquired. You may apply. Specifically, when the processing cannot be completed in the video frame from which the first contrast enhancement function f ₁ (Y _IN ) has been acquired, the signal processing device 200 applies the second contrast enhancement function f ₂ ( Y _IN ) may be applied.

Although not particularly mentioned in the above-described embodiment, when the amount of displacement by the second contrast enhancement function f ₂ (Y _IN ) varies greatly between the video frames, the video may look unnatural. Therefore, in order to prevent the displacement amount due to the second contrast enhancement function f ₂ (Y _IN ) from greatly differing between the video frames, a process of smoothing the displacement amount in the time axis direction may be performed.

  In the embodiment described above, the liquid crystal panel 30 is used as the display device, but the present invention is not limited to this. As the display device, LCOS (Liquid Crystal on Silicon), DMD (Digital Micromirror Device), or the like may be used.

  In the embodiment described above, a solid light source is used as the light source, but the present invention is not limited to this. A UHP lamp that emits white light may be used as the light source.

It is a figure which shows the structure of the projection type video display apparatus concerning 1st Embodiment. It is a block diagram which shows the structure of the signal processing apparatus 200 which concerns on 1st Embodiment. It is a histogram showing the frequency of the luminance Y _IN obtained from the video input signal according to the first embodiment. Is a diagram illustrating a first conversion gain GAIN ₁ and the second conversion gain GAIN ₂ according to the first embodiment. It is a diagram showing a correction gain GAIN _H according to the first embodiment. It is a diagram illustrating a first contrast enhancement function f _{1 (Y IN)} according to the first embodiment. It is a figure which shows the correction function h ( _YIN ) based on 1st Embodiment. Is a diagram illustrating a second contrast enhancement function f _{2 (Y IN)} according to the first embodiment. It is a flowchart which shows operation | movement of the signal processing apparatus 200 which concerns on 1st Embodiment. It is a block diagram which shows the structure of the signal processing apparatus 200 which concerns on 2nd Embodiment. It is a frequency distribution diagram which shows the frequency of the brightness | luminance YIN _calculated | required from the video input signal which concerns on 2nd Embodiment. It is a figure which shows the conversion gain contribution ((alpha)) which concerns on 2nd Embodiment. It is a diagram illustrating a first contrast enhancement function f _{1 (Y IN)} according to the second embodiment. It is a figure which shows the correction function h ( _YIN ) based on 2nd Embodiment. Is a diagram illustrating a second contrast enhancement function f _{2 (Y IN)} according to the second embodiment. It is a histogram showing the frequency of the luminance Y _IN obtained from the video input signal according to the embodiment. It is a diagram illustrating a first contrast enhancement function f _{1 (Y IN)} according to the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light source, 20 ... Cut filter, 21 ... UV cut filter, 30 ... Fly eye lens unit, 30a ... Fly eye lens, 30b ... Fly eye lens, 40 ... PBS array, 50 ... Liquid crystal panel, 50B ... Liquid crystal panel, 50G ... Liquid crystal panel, 50R ... Liquid crystal panel, 51B ... Compensation plate, 51G ... Compensation plate, 51R ... Compensation plate, 52B ... Incident side polarizing plate, 52G ... Incident side polarizing plate, 52R ... Incident side polarizing plate, 53B ... Incident side pre Polarizing plate, 53G ... incident side pre-polarizing plate, 53R ... incident side pre-polarizing plate, 54B ... outgoing side pre-polarizing plate, 54G ... outgoing side pre-polarizing plate, 54R ... outgoing side pre-polarizing plate, 55B ... outgoing side polarizing plate, 55G: Emission side polarizing plate, 55R: Emission side polarizing plate, 60 ... Cross dichroic prism, 70 ... Projection lens unit, 100 ... Projection type image display device DESCRIPTION OF SYMBOLS 111 ... Dichroic mirror, 112 ... Dichroic mirror, 121-123 ... Reflection mirror, 131-133 ... Condenser lens, 140B ... Condenser lens, 140G ... Condenser lens, 140R ... Condenser lens, 151-153 ... Relay lens, 200 ... Signal processing Apparatus 210 ... GAIN acquisition unit 220 ... setting unit 230 ... correction unit 240 ... conversion unit 250 ... control unit g (Y _IN ) ... linear reference function, f ₁ (Y _IN ) ... first contrast enhancement function , _{f 2 (Y IN)} ... second contrast enhancement function, h _{(Y IN)} ... correction function

Claims (6)

A setting unit for setting a first contrast enhancement function for converting a video input signal;
A correction unit that corrects the first contrast enhancement function based on a brightness level obtained from the video input signal and obtains a second contrast enhancement function;
A conversion unit that converts the video input signal by the second contrast enhancement function to obtain a video output signal;
The first contrast enhancement function has a first inflection point or a second inflection point,
The first inflection point is an inflection point provided at a position where the video input signal is converted so that the brightness level of the video output signal is lower than the brightness level of the video input signal. ,
The second inflection point is an inflection point provided at a position where the video input signal is converted so that the brightness level of the video output signal is higher than the brightness level of the video input signal. A display device characterized by that.   The correction unit shifts the first inflection point so that the brightness level of the video output signal becomes higher when the brightness level of the video input signal is lower than a predetermined brightness, The display device according to claim 1, wherein a second contrast enhancement function is acquired.   The correction unit shifts the second inflection point so that the brightness level of the video output signal is lowered when the brightness level of the video input signal is higher than a predetermined brightness, The display device according to claim 1, wherein a second contrast enhancement function is acquired.   As the brightness level of the video input signal is lower than the predetermined brightness, the conversion amount for converting the video input signal by the first contrast enhancement function is reduced, and the first contrast enhancement function is corrected by the correction unit. The display device according to claim 2, further comprising a control unit that increases a correction amount for correcting.   As the brightness level of the video input signal is higher than the predetermined brightness, the conversion amount for converting the video input signal by the first contrast enhancement function is reduced, and the first contrast enhancement function is corrected by the correction unit. The display device according to claim 3, further comprising a control unit that increases a correction amount for correcting.   The display device according to claim 1, wherein the setting unit sets the first inflection point or the second inflection point based on a brightness level of the video input signal.

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