JP2011197084A - Image display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display apparatus wherein a false color is not easily recognized at the end of a screen.SOLUTION: When an arbitrary red subpixel 152 at the left end of an image display region 23A is defined as a first subpixel and an arbitrary red subpixel 152 at a part other than the left end of the image display region 23A is defined as a second subpixel, the brightness of an image displayed by the first subpixel is lower than the brightness of an image displayed by the second subpixel when the image data of the same gradation are supplied from the outside to the first subpixel and the second subpixel. Also, when an arbitrary blue subpixel 154 at the right end of the image display region 23A is defined as a first subpixel and an arbitrary blue subpixel 154 at a part other than the right end of the image display region 23A is defined as a second subpixel, the brightness of an image displayed by the first subpixel is lower than the brightness of an image displayed by the second subpixel when the image data of the same gradation are supplied from the outside to the first subpixel and the second subpixel.

Description

  The present invention relates to an image display device.

  Conventionally, there has been known an image display device including a plurality of sub-pixels in one pixel. In this type of image display device, it is known that a false color is generated at an edge portion of an image according to the arrangement of sub-pixels. For example, in an image display device in which three types of sub-pixels of red, green, and blue are arranged in order from the left end of the screen, if one black line is displayed in a white background image, the left edge portion of the black line In addition, a blue false color corresponding to the blue sub-pixel may be generated, and a red false color corresponding to the red sub-pixel may be generated at the right edge of the black line.

  Such false colors appear to have red or blue coloring in the portion where white is originally displayed because the color of the sub-pixel at the edge of the image is strongly recognized by the human eye. It is a phenomenon that can be felt. When viewing the screen from a distance, such false colors are hardly recognized, but when viewing the screen up close like a portable information terminal or the like (for example, the distance between the screen and human eyes is 30 cm to 50 cm). In the case of), the influence of false color cannot be ignored.

  Thus, in Patent Document 1, the generation of false colors is suppressed by devising the arrangement of the sub-pixels to four or more types of sub-pixels. For example, FIG. 2 of Patent Document 1 proposes a method in which five sub-pixels are arranged in one pixel: red, green, blue, emerald green, and yellow, and they are arranged in a stripe shape in this order.

JP 2007-240659 A

  The image display device of Patent Document 1 is a device in which all sub-pixels in an image display area are arranged in a specific arrangement. Therefore, the occurrence of false colors is suppressed on the entire screen. However, the image display device of Patent Document 1 is limited to a specific type and arrangement of sub-pixels. Therefore, an image display device in which three types of normal red, green, and blue sub-pixels are arranged in a stripe shape. It cannot be applied.

  Further, such a false color usually appears at the edge of the screen. For example, at the left end and the right end of the screen, only the subpixels of a specific color are arranged according to the arrangement of the subpixels. Therefore, the color is impressed by human eyes. Also, in the vicinity of the edge of the screen, an achromatic image such as white or gray is often displayed as a background image. Since these background images are often fixed for a long time in the same color tone, false colors are easily recognized by human eyes at the edge of the background image, which is the left and right edges of the screen. Cause false color.

  An object of the present invention is to provide an image display device in which false colors are not easily recognized at the edge of a screen.

  The image display apparatus according to the present invention includes an image display region in which a plurality of pixels are arranged in the first direction and the second direction, and a plurality of sub-pixels are provided in one pixel, and display a plurality of different colors. The sub-pixels are arranged in the first direction, and a plurality of sub-pixels displaying the same color are arranged in the second direction, and an end of the first direction in the image display region An arbitrary sub-pixel located in a portion is defined as a first sub-pixel, and is a sub-pixel located at a position other than the end portion in the first direction in the image display area and displays the same color as the first sub-pixel. When the sub-pixel is the second sub-pixel, an image displayed on the first sub-pixel when image data of the same gradation is supplied from the outside to the first sub-pixel and the second sub-pixel Is expressed by the second sub-pixel. Characterized in that less than the brightness of the image to be.

  According to this configuration, since the brightness of the sub pixel at the end of the image display area that causes the false color is reduced, the color of the sub pixel is not strongly recognized by human eyes. Therefore, generation of false colors can be suppressed, and an image display device with high image quality can be provided.

  The subpixel adjacent to the first subpixel in the first direction is a third subpixel, and the subpixel is adjacent to the second subpixel in the first direction and displays the same color as the third subpixel. When the sub-pixel to be processed is the fourth sub-pixel, when the image data having the same gradation is supplied from the outside to the third sub-pixel and the fourth sub-pixel, the third sub-pixel is displayed. It is desirable that the brightness of the image is smaller than the brightness of the image displayed by the fourth subpixel.

  According to this configuration, generation of false colors can be suppressed as compared with a case where only the brightness of the first sub-pixel is reduced.

  The brightness of the image displayed by the sub-pixel is preferably adjusted by changing the aperture ratio of the sub-pixel.

  According to this configuration, since it is not necessary to adjust the brightness of the sub-pixels by correcting the image data, driving becomes easy.

  In one pixel, it is desirable that a red sub-pixel for displaying red, a green sub-pixel for displaying green, and a blue sub-pixel for displaying blue are arranged in this order along the first direction. In this case, the aperture ratio of each sub-pixel can be determined by the following method.

  As a first method, an aperture ratio of the red sub-pixel is set to Ar, at an end portion of the image display area where the red sub-pixel is the first sub-pixel and the green sub-pixel is the third sub-pixel. When the aperture ratio of the green subpixel is Ag, the Ar and the Ag can be determined so as to satisfy the following relational expression (1).

  As a second method, the aperture ratio of the blue sub-pixel is set to Ab at the end of the image display area where the blue sub-pixel is the first sub-pixel and the green sub-pixel is the third sub-pixel. When the aperture ratio of the green sub-pixel is Ag, the Ab and the Ag can be determined so as to satisfy the following relational expression (2).

  As a third method, at the edge of the image display area where the red sub-pixel is the first sub-pixel and the green sub-pixel is the third sub-pixel, the aperture ratio of the red sub-pixel is Ar, When the aperture ratio of the green sub-pixel is Ag, Ar and Ag can be determined so as to satisfy the following relational expression (3).

  As a fourth method, the aperture ratio of the blue sub-pixel is set to Ab at the end of the image display area where the blue sub-pixel is the first sub-pixel and the green sub-pixel is the third sub-pixel. When the aperture ratio of the green sub-pixel is Ag, the Ab and the Ag can be determined so as to satisfy the following relational expression (4).

  An image processing unit that corrects image data input from the outside to the sub-pixel, and the brightness of the image displayed by the sub-pixel varies the correction amount of the image data by the image processing unit. It is desirable to adjust by this.

  According to this configuration, it is not necessary to partially adjust the aperture ratio of the sub-pixels, so that the configuration of a conventionally used image display device can be used as it is. Since it is not necessary to change the design when manufacturing the image display device, manufacturing is facilitated.

When the gradation value of image data input from the outside is α _i , the maximum displayable gradation value is α _M , the gamma correction value is γ, and the correction amount is β, It is desirable to determine the gradation value α _o of the corrected image data input to the sub-pixel based on the equation (5).

  According to this configuration, gradation correction can be performed accompanying gamma correction. A conventional configuration of the sub-pixel of the image display device can be used. Therefore, the effect of the present invention can be easily obtained only by changing the contents of the lookup table describing the calculation result of gamma correction.

It is a block diagram which shows schematic structure of the image display apparatus of 1st Embodiment. It is a perspective view which shows the specific structure of the display part of the image display apparatus. It is a top view of the image display area provided in the display part. It is a figure which shows the calculation procedure of S-CIELAB. It is a parameter used in the calculation procedure of S-CIELAB. It is a parameter used in the calculation procedure of S-CIELAB. It is a figure which shows the combination of the aperture ratio of the sub pixel of the left end part of an image display area. It is a figure which shows the combination of the aperture ratio of the sub pixel of the right end part of an image display area. It is the evaluation result of the image quality of the left half area of the image display area. It is the evaluation result of the image quality of the right half area of the image display area. It is an image quality evaluation result on the left half of the screen when the image quality evaluation index is an average value of color differences. It is an image quality evaluation result at the right end of the screen when the image quality evaluation index is an average value of color differences. It is the image quality evaluation result at the left end of the screen when the image quality evaluation index is the maximum value of the color difference. It is the image quality evaluation result at the right end of the screen when the image quality evaluation index is the maximum value of the color difference. It is a block diagram which shows schematic structure of the image display apparatus of 2nd Embodiment. It is a top view of the image display area provided in the display part of the image display device. It is a figure which shows the combination of the corrected amount of the sub pixel of the left end part of an image display area. It is a figure which shows the combination of the corrected amount of the sub pixel of the right end part of an image display area. It is the evaluation result of the image quality of the left half area of the image display area. It is the evaluation result of the image quality of the right half area of the image display area.

[First Embodiment]
FIG. 1 is a block diagram illustrating a schematic configuration of an image display device 100 according to the first embodiment.

  The image display apparatus 100 mainly includes an image processing unit 10, a data line driving circuit 21, a scanning line driving circuit 22, and a display unit 23. The image display device 100 is configured to be able to display an image using three sub-pixels: a red sub-pixel that displays red, a green sub-pixel that displays green, and a blue sub-pixel that displays blue. In the following, “red”, “green”, and “blue” may be simply referred to as “R”, “G”, and “B”.

  The image processing unit 10 includes an I / F control circuit 11, a color conversion circuit 12, a VRAM 13, an address control circuit 14, a table storage memory 15, and a γ correction circuit 16. The I / F control circuit 11 acquires image data and a control command from the outside (for example, a camera) and supplies the image data d1 to the color conversion circuit 12. Image data supplied from the outside is composed of three colors, R, G, and B.

  The color conversion circuit 12 performs image processing such as color conversion with reference to data stored in the table storage memory 15. The image data d2 subjected to image processing by the color conversion circuit 12 is written in the VRAM 13. The image data d2 written in the VRAM 13 is read out as image data d3 by the γ correction circuit 16 based on a control signal d21 from the address control circuit, and at the same time, the address data (scanning line driving circuit 22 is read by the scanning line driving circuit 22). Read as d4) (to synchronize based on address data). The γ correction circuit 16 performs gamma correction on the acquired image data d3 with reference to data (lookup table) stored in the table storage memory 15 or the like. The γ correction circuit 16 supplies the image data d5 after the gamma correction to the data line driving circuit 21.

When the gradation value of image data input from the outside is α _i , the maximum gradation value that can be displayed is α _M , and the gamma correction value is γ, the image processing unit 10 uses the following equation (6). Based on this, the gradation value α _o of the corrected image data input to the sub-pixel is determined. The calculation result is stored as a lookup table in the table storage memory 15, and the γ correction circuit 16 performs gamma correction on the image data d3 with reference to the lookup table.

  The data line drive circuit 21 supplies data line drive signals X1 to X3072 to 3072 data lines. The scanning line driving circuit 22 supplies scanning line driving signals Y1 to Y768 to 768 scanning lines. The data line driving circuit 21 and the scanning line driving circuit 22 drive the display panel 23 in synchronization. The display unit 23 is composed of a liquid crystal (LCD) and displays an image using three colors of RGB. The display unit 23 is configured with an XGA size having “768 vertical pixels × 1024 horizontal pixels” unit pixels (hereinafter simply referred to as “pixels”) having three sub-pixels corresponding to RGB as a set. . Therefore, the number of data lines is “1024 × 3 = 3072”. The display unit 23 displays images such as characters and video to be displayed by applying voltages to the scanning lines and the data lines.

  FIG. 2 is a perspective view showing a specific configuration of the display unit 23. A pixel electrode 23f is formed inside the TFT array substrate 23g, and a common electrode 23d is formed inside the counter substrate 23b. A color filter 23c is formed between the counter substrate 23b and the common electrode 23d. A backlight unit 23i and upper and lower polarizing plates 23a and 23h are formed outside the TFT array substrate 23g and the counter substrate 23b.

  The TFT array substrate 23g and the counter substrate 23b are made of a transparent substrate such as glass or plastic. The pixel electrode 23f and the common electrode 23d are formed of a transparent conductor such as ITO (indium tin oxide). The pixel electrode 23f is connected to a TFT (Thin Film Transistor) provided on the TFT array substrate 23g, and applies a voltage to the liquid crystal layer 23e between the common electrode 23d and the pixel electrode 23f in accordance with the switching driving of the TFT. It is supposed to be. The liquid crystal layer 23e includes liquid crystal molecules whose arrangement changes according to the voltage value applied by the common electrode 23d and the pixel electrode 23f.

  In the liquid crystal layer 23e and the upper and lower polarizing plates 23a and 23h, the amount of light transmitted through the liquid crystal layer 23e and the upper and lower polarizing plates 23a and 23h is changed by changing the arrangement of the liquid crystal molecules according to the voltage value applied to the liquid crystal layer 23e. change. The liquid crystal layer 23e controls the amount of light incident from the backlight unit 23i side, and transmits the light to the observer side with a predetermined light transmission amount. The backlight unit 23i includes a light source and a light guide plate. The light emitted from the light source is uniformly spread inside the light guide plate, and the light source light is emitted in the direction indicated by the arrow in FIG. A light source is comprised from a fluorescent tube, white LED, etc., and a light-guide plate is comprised from resin, such as an acryl. The display unit 23 is a transmissive liquid crystal display device that emits light emitted from the backlight unit 23 i in a direction indicated by an arrow and extracts the light from the counter substrate 23 b side. That is, liquid crystal display is performed using the light source light of the backlight unit 23i.

  FIG. 3 is a plan view of the image display area 23 </ b> A provided in the display unit 23. In FIG. 3, four pixels 151 in the horizontal direction and four pixels 151 in the vertical direction are illustrated, but actually, 1024 pixels 151 in the horizontal direction and 768 pixels 151 in the vertical direction are provided in the image display region 23A. It has been. The “lateral direction” is a direction parallel to the scanning line and corresponds to the “first direction” of the present invention. The “longitudinal direction” is a direction perpendicular to the scanning line and corresponds to the “second direction” of the present invention.

  In the image display area 23A, a plurality of pixels 151 are arranged in the vertical direction and the horizontal direction. One pixel 151 is provided with three sub-pixels, a red sub-pixel 152, a green sub-pixel 153, and a blue sub-pixel 154, in order from the left side. The aspect ratio of the pixel 151 is 1: 1, and the aspect ratio of each sub-pixel is approximately 3: 1. In the red sub-pixel 152, the green sub-pixel 153, and the blue sub-pixel 154, red, green, and blue color filters corresponding to the respective colors are arranged. Each sub-pixel is provided with a pixel electrode 23f, and a region where the pixel electrode 23f and the color filter overlap is a sub-pixel region. The image display area 23A employs a stripe arrangement, in which subpixels that display the same color are arranged in the vertical direction, and subpixels that display different colors are arranged in the horizontal direction.

  In FIG. 3, reference numeral 155 denotes a first pixel constituted by a plurality of pixels 151 arranged in the vertical direction at the left end portion of the image display area 23 </ b> A among the plurality of pixels 151 positioned at the outermost peripheral portion of the image display area 23 </ b> A. One pixel column is shown. Reference numeral 156 denotes a second pixel constituted by a plurality of pixels 151 arranged in the vertical direction at the right end portion of the image display region 23A among the plurality of pixels 151 located at the outermost peripheral portion of the image display region 23A. Indicates a column.

  At the position overlapping the red sub-pixel 152 of the first pixel column 155, the aperture ratio of any red sub-pixel 152 included in the first pixel column 155 is the aperture ratio of any red sub-pixel 152 other than the first pixel column 155. A light shielding film 157 is provided to make the size smaller than the above.

  At the position overlapping the green sub-pixel 153 of the first pixel column 155, the aperture ratio of the arbitrary green sub-pixel 153 of the first pixel column 155 is set to an arbitrary green sub-pixel other than the first pixel column 155 and the second pixel column 156. A light shielding film 158 for reducing the aperture ratio of 153 is provided.

  The aperture ratio of any blue subpixel 154 in the second pixel column 156 is set to be higher than the aperture ratio of any blue subpixel 154 other than the second pixel column 156 at a position overlapping the blue subpixel 154 in the second pixel column 156. A light shielding film 159 for reducing the size is provided.

  At the position overlapping the green sub-pixel 153 of the second pixel column 156, the aperture ratio of the arbitrary green sub-pixel 153 of the second pixel column 156 is set to an arbitrary green sub-pixel other than the second pixel column 156 and the first pixel column 155. A light shielding film 160 is provided to make the aperture ratio smaller than 153.

  In the image display device 100, when an arbitrary red sub-pixel 152 included in the first pixel column 155 is a first sub-pixel and an arbitrary red sub-pixel 152 not included in the first pixel column 155 is a second sub-pixel, The aperture ratio of the first subpixel is smaller than the aperture ratio of the second subpixel. Therefore, when image data having the same gradation is supplied from the outside to the first sub-pixel and the second sub-pixel, the brightness of the image displayed by the first sub-pixel is the brightness of the image displayed by the second sub-pixel. Smaller than this.

  Further, if any blue subpixel 154 included in the second pixel column 156 is a first subpixel and any blue subpixel 154 not included in the second pixel column 156 is a second subpixel, the first subpixel Is smaller than the aperture ratio of the second sub-pixel. Therefore, when image data of the same gradation is supplied from the outside to the first subpixel and the second subpixel, the brightness of the image displayed by the first subpixel is the same as that of the image displayed by the second subpixel. It becomes smaller than the brightness.

  In the image display device 100, the green subpixel 153 that is adjacent to the arbitrary red subpixel 152 included in the first pixel column 155 in the horizontal direction is set as the third subpixel, and the first pixel column 155 and the second pixel column 156 are used. If the green subpixel 153 that is adjacent to any red subpixel 152 that is not included in the horizontal direction is the fourth subpixel, the aperture ratio of the third subpixel is smaller than the aperture ratio of the fourth subpixel. Therefore, when image data having the same gradation is supplied from the outside to the third sub-pixel and the fourth sub-pixel, the brightness of the image displayed by the third sub-pixel is the brightness of the image displayed by the fourth sub-pixel. It becomes smaller than the brightness.

  In addition, a green subpixel 153 that is adjacent to an arbitrary blue subpixel 154 included in the second pixel column 156 in the horizontal direction is set as a third subpixel, and an arbitrary blue subpixel 154 that is not included in the second pixel column 156 is horizontally aligned. When the green subpixel 153 adjacent in the direction is the fourth subpixel, the aperture ratio of the third subpixel is smaller than the aperture ratio of the fourth subpixel. Therefore, when image data having the same gradation is supplied from the outside to the third sub-pixel and the fourth sub-pixel, the brightness of the image displayed by the third sub-pixel is the brightness of the image displayed by the fourth sub-pixel. It becomes smaller than the brightness.

  The aperture ratios of the red sub-pixel 152 and the green sub-pixel 153 included in the first pixel column 155 and the aperture ratios of the blue sub-pixel 154 and the green sub-pixel 153 included in the second pixel column 156 are S-CIELAB (Spatial CIELAB ) Determined by visual simulation.

  S-CIELAB is an image evaluation method proposed by X Zhang et al. And is known as an objective evaluation method that can appropriately evaluate the color reproducibility of a color image correlated with subjective evaluation. The evaluation method of S-CIELAB incorporates visual spatial frequency characteristics into the distance in uniform color space. By using S-CIELAB, it is possible to reproduce the human appearance when an image displayed on the image display device 100 is observed from a certain distance, and to evaluate the image quality.

  FIG. 4 is a diagram showing a calculation procedure of S-CIELAB.

  First, an original image (Ideal Image) and a display image (RGB-Stripe Image) are input as input images. The original image is an image of an ideal display having no sub-pixel structure, and the display image is an image of a display having a sub-pixel structure. Examples of the original image include simultaneous additive color mixture in which a plurality of color images are simultaneously superimposed, and an image obtained by successive additive color mixture in which a plurality of color images are superimposed in a time division manner. The display image is obtained by juxtaposing and mixing the colors of a plurality of sub-pixels as shown in FIG.

  In the present embodiment, gray images are displayed as the original image and the display image. The gray image is an image composed of 127 gradations of red, 127 gradations of green, and 127 gradations of blue when the maximum displayable gradation is 255 gradations.

  Next, according to the following procedure, the human appearance when the original image and the display image are observed from a certain distance is reproduced.

First, the RGB image is converted from the XYZ color system XYZ value (predicted value) to the opposite color signal O ₁ O ₂ O ₃ in the opposite color space by Expression (7). Luminance O ₁ corresponds to Luminance, color difference O ₂ corresponds to Red-Green, and color difference O ₂ corresponds to Yellow-Blue.

Next, according to the equation (8), the image (O ₁ , O ₂ , O ₃ ) in the S-CIELAB opposite color space is convolved with three different visual filters corresponding to each channel, and the visual filter processing is performed. Later images (O ₁ ′, O ₂ ′, O ₃ ′) are calculated.

The visual filter of each channel is obtained by synthesizing a plurality of Gaussian functions having different dispersions shown in FIG. 5 by the equations (9) and (10), and the spatial resolution of the color difference with respect to the luminance is greatly reduced. ing. Finally, O ₁ ′, O ₂ ′, and O ₃ ′ are inversely converted to XYZ and converted to L ^* a ^* b ^* .

As a reproduced image of the original image obtained by the above procedure, a reproduced image of the display display image is obtained for each pixel in the L ^* c ^* h ^* space to obtain a color difference ΔE ^* _94, and a difference image (Difference Image) is obtained.

Next, an average value and a maximum value of the color difference ΔE ^* ₉₄ in the left half area of the image display area 23A including the first pixel column 155 are obtained and calculated as an evaluation index for image quality. Further, an average value and a maximum value of the color difference ΔE ^* ₉₄ in the right half area of the image display area 23A including the second pixel row 156 are obtained and calculated as an evaluation index for image quality.

The calculation conditions of S-CIELAB are as follows.
-Viewing distance: 30cm
・ Pixel structure: RGB stripe arrangement ・ Resolution: 132ppi
(Number of pixels: 1024 x 768 pixels)
(Size: 9.7 inches)
-Color characteristics: Fig. 6
・ Γ: 2.2
Input image: Gray image (RGB = [127, 127, 127]. However, the maximum displayable gradation is 255)
The aperture ratio of each sub-pixel in the first pixel column (normalized with the blue sub-pixel being 100%): FIG.
The aperture ratio of each sub-pixel in the second pixel row (normalized assuming the red sub-pixel as 100%): FIG.

FIG. 9 shows the evaluation result of the image quality of the left half area of the image display area 23 </ b> A including the first pixel column 155. The aperture ratio Ar of the red sub-pixel 152 is changed in six steps of 100%, 80%, 60%, 40%, 20%, and 0%, and the aperture ratio Ag of the green sub-pixel 153 is changed to 100%, 80%, and 60%. , 40%, 20%, and 0%. Note that “Ar” and “Ag” in FIG. 9 are normalized by setting the aperture ratio Ab of the blue sub-pixel 154 to 100%. In FIG. 9, the numerical value on the upper side is the average value of the color difference ΔE ^* ₉₄ , and the numerical value on the lower side is the maximum value of the color difference ΔE ^* ₉₄ .

In FIG. 9, (Ar, Ag) = (100%, 100%) is a conventional configuration. The average value of the color difference ΔE ^* ₉₄ at (Ar, Ag) = (100%, 100%) is 3.80, and the maximum value of the color difference ΔE ^* ₉₄ is 18.55. If the average value or the maximum value of the color difference ΔE ^* ₉₄ is smaller than this, it means that the occurrence of false colors can be suppressed more than before. The size of the false color may be evaluated by an average value of color differences or may be evaluated by a maximum value.

  As shown in FIG. 9, by appropriately adjusting the aperture ratio Ar of the red sub-pixel and the aperture ratio Ag of the green sub-pixel, generation of false colors can be suppressed. If the aperture ratio Ar of the red sub-pixel is reduced, the generation of false color is generally suppressed, but if the aperture ratio Ar of the red sub-pixel is too small, the false color is increased. The reason is considered as follows.

  First, at the left end of the image display area, the red sub-pixel constitutes the outer frame of the image display area. Therefore, red is strongly impressed by human eyes, and the peripheral portion of the image display area is recognized as reddish. This is the reason why a red false color occurs at the left end of the image display area. Therefore, if the aperture ratio Ar of the red sub-pixel arranged at the left end portion of the image display area is reduced, such red color can be reduced, and the occurrence of red false color can be suppressed.

  However, if the aperture ratio Ar of the red sub-pixel is too small, the color of the green sub-pixel is impressed strongly to the human eye, which causes a green false color. Therefore, by appropriately designing the aperture ratio Ar of the red sub-pixel within a predetermined range, it is possible to effectively suppress the occurrence of red false color.

  This is true even when the aperture ratio Ag of the green sub-pixel is too small. If the aperture ratio Ag of the green sub-pixel is made too small, the color of the blue sub-pixel is strongly impressed by the human eye, which may cause a blue false color.

  Therefore, if the aperture ratio Ar of the red sub-pixel and the aperture ratio Ag of the green sub-pixel are set to a predetermined size or more and the aperture ratio Ar of the red sub-pixel is made smaller than the aperture ratio Ag of the green sub-pixel, false Color generation is generally suppressed.

FIG. 10 shows the evaluation result of the image quality of the right half of the image display area 23A including the second pixel row 156. The aperture ratio Ab of the blue sub-pixel 154 is changed in six steps of 100%, 80%, 60%, 40%, 20%, and 0%, and the aperture ratio Ag of the green sub-pixel 153 is 100%, 80%, and 60%. , 40%, 20%, and 0%. Note that “Ab” and “Ag” in FIG. 10 are normalized by setting the aperture ratio Ar of the red sub-pixel 152 to 100%. In FIG. 10, the numerical value on the upper side is the average value of the color difference ΔE ^* ₉₄ , and the numerical value on the lower side is the maximum value of the color difference ΔE ^* ₉₄ .

In FIG. 10, (Ab, Ag) = (100%, 100%) is a conventional configuration. The average value of the color difference ΔE ^* ₉₄ at (Ab, Ag) = (100%, 100%) is 5.58, and the maximum value of the color difference ΔE ^* ₉₄ is 17.98. If the average value or the maximum value of the color difference ΔE ^* ₉₄ is smaller than this, it means that the occurrence of false colors can be suppressed more than before.

  In FIG. 10, the same tendency as in FIG. 9 is observed. That is, if the aperture ratio Ab of the blue subpixel is reduced, the occurrence of false color is generally suppressed. However, if the aperture ratio Ab of the blue subpixel is too small, the false color is increased. If the aperture ratio Ab of the blue subpixel and the aperture ratio Ag of the green subpixel are set to be equal to or larger than a predetermined size, and the aperture ratio Ab of the blue subpixel is made smaller than the aperture ratio Ag of the green subpixel, a false color Occurrence is generally suppressed.

FIG. 11 and FIG. 12 show the evaluation results of the image quality when the image quality evaluation index is the average value of the color difference ΔE ^* ₉₄ by ◯ ×. FIG. 11 shows the evaluation result of the image quality of the left half region of the image display area including the first pixel column, and FIG. 12 shows the evaluation result of the image quality of the right half region of the image display region including the second pixel column. is there. In FIG. 11 and FIG. 12, “◯” indicates that the false color is suppressed as compared with the conventional case, and “X” indicates that the false color is the same as or larger than the conventional one.

  According to FIG. 11, a preferable range of the aperture ratio Ar of the red subpixel and the aperture ratio Ag of the green subpixel at the left end of the image display area is defined by the following formula (11).

  Also, according to FIG. 12, a preferable range of the aperture ratio Ab of the blue subpixel and the aperture ratio Ag of the green subpixel at the right end of the image display area is defined by the following formula (12).

FIG. 13 and FIG. 14 show the evaluation results of the image quality when the evaluation index of the image quality is the maximum value of the color difference ΔE ^* ₉₄ by ○ ×. FIG. 13 shows the evaluation result of the image quality of the left half region of the image display area including the first pixel column, and FIG. 14 shows the evaluation result of the image quality of the right half region of the image display region including the second pixel column. is there. In FIG. 13 and FIG. 14, “◯” indicates that the false color is suppressed as compared with the conventional case, and “X” indicates that the false color is the same as or larger than the conventional one.

  According to FIG. 13, a preferable range of the aperture ratio Ar of the red sub-pixel and the aperture ratio Ag of the green sub-pixel at the left end of the image display area is defined by the following equation (13).

  Further, according to FIG. 14, a preferable range of the aperture ratio Ab of the blue subpixel and the aperture ratio Ag of the green subpixel at the right end of the image display area is defined by the following formula (14).

  According to the image display device 100 of the present embodiment, the following effects can be obtained. First, since the brightness of the sub-pixel at the outermost periphery of the image display area 23A that causes false color is reduced, the color of the sub-pixel is not strongly recognized by human eyes. Therefore, generation of false colors can be suppressed, and an image display device with high image quality can be provided. Further, by adjusting not only the sub-pixel located in the outermost peripheral portion of the image display area 23A but also the aperture ratio of the sub-pixel adjacent to the sub-pixel in the horizontal direction, generation of false color can be further suppressed.

  In this embodiment, the light shielding film 157 is disposed so as to shield the left end side of the red sub-pixel. However, the position of the light shielding film 157 is not limited to this, and the central portion or the right end side of the red sub-pixel is shielded. You may arrange as follows. The same applies to the light shielding films 158 to 160. Even if the position of the light shielding film is changed, the evaluation results shown in FIGS.

  In this embodiment, the S-CIELAB calculation condition is that the input image is a gray image. However, the red subpixel, the green subpixel, and the blue subpixel all have a maximum gradation (for example, 255 gradations). An image may be used as an input image. Also in this case, the evaluation results shown in FIGS.

[Second Embodiment]
FIG. 15 is a block diagram illustrating a schematic configuration of an image display apparatus 200 according to the second embodiment.

  In the present embodiment, the same reference numerals are assigned to configurations common to the first embodiment, and detailed description thereof is omitted.

The difference between the image display apparatus 200 of the present embodiment and the image display apparatus 100 of the first embodiment is that the aperture ratios of the sub-pixels of the display unit 231 are all equal in the entire image display area, and the image processing unit 210 is described below. The gradation value α _o of the corrected image data input to the sub-pixel is determined based on the equation (15).

However, α _i is a gradation value of image data inputted from the outside, α _M is a maximum gradation value that can be displayed, γ is a gamma correction value, and α _o is a correction input to the sub-pixel. It is a gradation value of the subsequent image data, and β is a correction amount set for each sub-pixel.

  As the correction amount β, different values are set for the central portion and the peripheral portion of the image display area. That is, the correction amount β of the red sub-pixel and the green sub-pixel included in the pixel at the left end of the image display area and the blue sub-pixel and the green sub-pixel included in the pixel at the right end of the image display area is the other sub-pixel. Is set to a value smaller than the correction amount β.

  FIG. 16 is a plan view of an image display area 231A provided in the display unit 231. FIG. In FIG. 16, four pixels 1511 in the horizontal direction and three pixels 1511 in the vertical direction are illustrated, but actually, 1024 pixels 1511 in the horizontal direction and 768 pixels 1511 in the vertical direction are provided in the image display area 231A. It has been. The “lateral direction” is a direction parallel to the scanning line and corresponds to the “first direction” of the present invention. The “longitudinal direction” is a direction perpendicular to the scanning line and corresponds to the “second direction” of the present invention. In addition, the numerical values displayed in the sub-pixels 1521, 1531, and 1541 in FIG. 16A are the gradation values of the image data supplied from the outside, and the sub-pixels 1521, 1531, and 1541 in FIG. The numerical value displayed in is the gradation value of the image data after the gamma correction corrected by the γ correction circuit 216.

  In the image display area 231A, a plurality of pixels 1511 are arranged in the vertical direction and the horizontal direction. One pixel 1511 includes three sub-pixels, a red sub-pixel 1521, a green sub-pixel 1531, and a blue sub-pixel 1541. The aspect ratio of the pixel 1511 is 1: 1, and the aspect ratio of each sub-pixel is approximately 3: 1. In the red sub-pixel 1521, the green sub-pixel 1531, and the blue sub-pixel 1541, red, green, and blue color filters corresponding to the respective colors are arranged. Each subpixel is provided with a pixel electrode, and a region where the pixel electrode and the color filter overlap is a subpixel region. The image display area 231A employs a stripe arrangement, in which sub-pixels displaying the same color are arranged in the vertical direction, and sub-pixels displaying different colors are arranged in the horizontal direction.

  In FIG. 16, reference numeral 1551 denotes a first pixel constituted by a plurality of pixels 1511 arranged in the vertical direction at the left end portion of the image display area 231A among the plurality of pixels 1511 positioned at the outermost peripheral portion of the image display area 231A. One pixel column is shown. Reference numeral 1561 denotes a second pixel constituted by a plurality of pixels 1511 arranged in the vertical direction at the right end portion of the image display region 231A among the plurality of pixels 1511 positioned at the outermost peripheral portion of the image display region 231A. Indicates a column.

  In the image display device 200, when an arbitrary red sub-pixel 1521 included in the first pixel column 1551 is a first sub-pixel and an arbitrary red sub-pixel 1521 not included in the first pixel column 1551 is a second sub-pixel, The correction amount β of the first subpixel is smaller than the correction amount β of the second subpixel. Therefore, when image data having the same gradation is supplied from the outside to the first sub-pixel and the second sub-pixel, the brightness of the image displayed by the first sub-pixel is the brightness of the image displayed by the second sub-pixel. Smaller than this.

  Further, if an arbitrary blue subpixel 1541 included in the second pixel column 1561 is a first subpixel and an arbitrary blue subpixel 1541 not included in the second pixel column 1561 is a second subpixel, the first subpixel Is smaller than the correction amount β of the second sub-pixel. Therefore, when image data of the same gradation is supplied from the outside to the first subpixel and the second subpixel, the brightness of the image displayed by the first subpixel is the same as that of the image displayed by the second subpixel. It becomes smaller than the brightness.

  In the image display device 200, an arbitrary green subpixel 1531 included in the first pixel column 1551 is set as a third subpixel, and an arbitrary green subpixel 1531 not included in the first pixel column 1551 and the second pixel column 1561 is used. Is the fourth subpixel, the correction amount β of the third subpixel is smaller than the correction amount β of the fourth subpixel. Therefore, when image data having the same gradation is supplied from the outside to the third sub-pixel and the fourth sub-pixel, the brightness of the image displayed by the third sub-pixel is the brightness of the image displayed by the fourth sub-pixel. It becomes smaller than the brightness.

  Further, if an arbitrary green sub-pixel 1531 included in the second pixel column 1561 is a third sub-pixel and an arbitrary green sub-pixel 1531 not included in the second pixel column 1561 is a fourth sub-pixel, the third sub-pixel Is smaller than the correction amount β of the fourth sub-pixel. Therefore, when image data having the same gradation is supplied from the outside to the third sub-pixel and the fourth sub-pixel, the brightness of the image displayed by the third sub-pixel is the brightness of the image displayed by the fourth sub-pixel. It becomes smaller than the brightness.

  In the image display device 100 according to the first embodiment, as illustrated in FIG. 3, the aperture ratios of arbitrary red subpixels 152 and green subpixels 153 of the pixels 151 included in the first pixel column 155, and the second pixel column The aperture ratio of an arbitrary blue sub-pixel 154 and green sub-pixel 153 of the pixel 151 included in the pixel 156 is smaller than the aperture ratio of the other sub-pixels of the same color of the pixel 151.

  On the other hand, in the image display device 200 of the second embodiment, the aperture ratios of the sub pixels are all the same in the entire image display area. Instead, by adjusting the correction amount β for each sub-pixel based on Expression (15), the brightness of the image of any red sub-pixel 152 and green sub-pixel 153 included in the first pixel column 155, and The brightness of the image of any blue sub-pixel 154 and green sub-pixel 153 included in the second pixel column 156 is smaller than the brightness of the image displayed by the other sub-pixels of the same color.

  The result calculated based on the above equation (15) is stored in the table storage memory 215 as a lookup table. The γ correction circuit 216 performs gamma correction on the image data d3 with reference to the lookup table.

  The correction amount β of the red subpixel 1521 and the green subpixel 1531 included in the first pixel column 1551 and the correction amount β of the blue subpixel 1541 and the green subpixel 1531 included in the second pixel column 1561 are S-CIELAB ( Determined by visual simulation by Spatial CIELAB).

The calculation procedure is the same as that shown in FIG. The calculation conditions are as follows.
-Viewing distance: 30cm
・ Pixel structure: RGB stripe arrangement ・ Resolution: 132ppi
(Number of pixels: 1024 x 768 pixels)
(Size: 9.7 inches)
-Color characteristics: Fig. 6
・ Γ: 2.2
Input image: Gray image (RGB = [127, 127, 127]. However, the maximum displayable gradation is 255)
-Correction amount of each sub-pixel in the first pixel column (normalized by setting the blue sub-pixel as 100%): FIG.
Correction amount of each sub-pixel in the second pixel column (normalized with red sub-pixel as 100%): FIG.

FIG. 19 shows the evaluation results of the image quality of the left half area of the image display area 231A including the first pixel column 1551. The correction amount βr of the red sub-pixel 1521 is changed in six stages of 100%, 80%, 60%, 40%, 20%, and 0%, and the correction amount βg of the green sub-pixel 1531 is changed to 100%, 80%, and 60%. , 40%, 20%, and 0%. Note that “βr” and “βg” in FIG. 19 are normalized by setting the aperture ratio βb of the blue sub-pixel 1541 to 100%. In FIG. 19, the numerical value on the upper side is the average value of the color difference ΔE ^* ₉₄ , and the numerical value on the lower side is the maximum value of the color difference ΔE ^* ₉₄ .

In FIG. 19, (βr, βg) = (100%, 100%) is a conventional configuration. The average value of the color difference ΔE ^* ₉₄ at (βr, βg) = (100%, 100%) is 3.80, and the maximum value of the color difference ΔE ^* ₉₄ is 18.55. If the average value or the maximum value of the color difference ΔE ^* ₉₄ is smaller than this, it means that the occurrence of false colors can be suppressed more than before. The size of the false color may be evaluated by an average value of color differences or may be evaluated by a maximum value.

  As shown in FIG. 19, by appropriately adjusting the correction amount βr of the red sub-pixel and the correction amount βg of the green sub-pixel, generation of false colors can be suppressed. If the correction amount βr of the red sub-pixel is reduced, the occurrence of false color is generally suppressed. However, if the correction amount βr of the red sub-pixel is too small, the false color is increased. The reason is considered as follows.

  First, at the left end of the image display area, the red sub-pixel constitutes the outer frame of the image display area. Therefore, red is strongly impressed by human eyes, and the peripheral portion of the image display area is recognized as reddish. This is the reason why a red false color occurs at the left end of the image display area. Therefore, if the correction amount βr of the red sub-pixel arranged at the left end portion of the image display area is reduced, such red color can be reduced, and the occurrence of red false color can be suppressed.

  However, if the correction amount βr of the red sub-pixel is made too small, the color of the green sub-pixel is impressed strongly to the human eye, which causes a green false color. Therefore, by appropriately designing the correction amount βr of the red sub-pixel within a predetermined range, it is possible to effectively suppress the occurrence of red false color.

  This is true even when the correction amount βg of the green sub-pixel is made too small. If the correction amount βg of the green sub-pixel is too small, the color of the blue sub-pixel is strongly impressed by the human eye, and thus a blue false color may be generated.

  Therefore, if the correction amount βr of the red subpixel and the correction amount βg of the green subpixel are set to be equal to or larger than a predetermined size and the correction amount βr of the red subpixel is made smaller than the correction amount βg of the green subpixel, false Color generation is generally suppressed.

FIG. 20 shows the evaluation result of the image quality of the right half of the image display area 231A including the second pixel row 1561. The correction amount βb of the blue sub pixel 1541 is changed in six steps of 100%, 80%, 60%, 40%, 20%, and 0%, and the correction amount βg of the green sub pixel 1531 is changed to 100%, 80%, and 60%. , 40%, 20%, and 0%. Note that “βb” and “βg” in FIG. 20 are normalized by assuming that the correction amount βr of the red sub-pixel 1521 is 100%. In FIG. 20, the numerical value on the upper side is the average value of the color difference ΔE ^* ₉₄ , and the numerical value on the lower side is the maximum value of the color difference ΔE ^* ₉₄ .

In FIG. 20, (βb, βg) = (100%, 100%) is a conventional configuration. The average value of the color difference ΔE ^* ₉₄ at (βb, βg) = (100%, 100%) is 5.58, and the maximum value of the color difference ΔE ^* ₉₄ is 17.98. If the average value or the maximum value of the color difference ΔE ^* ₉₄ is smaller than this, it means that the occurrence of false colors can be suppressed more than before.

  In FIG. 20, the same tendency as in FIG. 19 is observed. That is, if the correction amount βb of the blue subpixel is reduced, the occurrence of false color is generally suppressed. However, if the correction amount βb of the blue subpixel is too small, the false color is increased. If the correction amount βb of the blue subpixel and the correction amount βg of the green subpixel are set to be equal to or larger than a predetermined size and the correction amount βb of the blue subpixel is smaller than the correction amount βg of the green subpixel, a false color Occurrence is generally suppressed.

  According to the image display apparatus 200 of the present embodiment, the following effects can be obtained. First, since the brightness of the sub-pixel at the outermost periphery of the image display area 23A that causes false color is reduced, the color of the sub-pixel is not strongly recognized by human eyes. Therefore, generation of false colors can be suppressed, and an image display device with high image quality can be provided. Further, by adjusting not only the sub-pixel located in the outermost peripheral portion of the image display area 23A but also the aperture ratio of the sub-pixel adjacent to the sub-pixel in the horizontal direction, generation of false color can be further suppressed.

  Further, according to the image display apparatus 200 of the present embodiment, gradation correction can be performed in association with gamma correction, so that the conventional configuration of the sub-pixels of the image display apparatus 200 can be used. . Therefore, the effect of the present invention can be easily obtained only by changing the contents of the lookup table describing the calculation result of gamma correction.

  In the present embodiment, the input image is a gray image as a calculation condition of S-CIELAB. However, a white image having a maximum gradation (for example, 255 gradations) for all of the red subpixel, the green subpixel, and the blue subpixel. An image may be used as an input image. In this case, the same results as the evaluation results shown in FIGS. 19 and 20 are obtained.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

23A ... Image display area, 100 ... Image display device, 151 ... Pixel, 152 ... Red sub-pixel, 153 ... Green sub-pixel, 154 ... Blue sub-pixel, 200 ... Image display device, 210 ... Image processing unit, 231A ... Image display 1511 ... Pixel, 1521 ... Red subpixel, 1531 ... Green subpixel, 1541 ... Blue subpixel, Ar ... Red subpixel aperture ratio, Ag ... Green subpixel aperture ratio, Ab ... Blue subpixel aperture ratio , Βr: red sub-pixel correction amount, βg: green sub-pixel correction amount, βb: blue sub-pixel correction amount

Claims (10)

An image display area in which a plurality of pixels are arranged in a first direction and a second direction, a plurality of subpixels are provided in one pixel, and a plurality of subpixels displaying different colors are in the first direction A plurality of sub-pixels arranged in the second direction and displaying the same color with each other,
An arbitrary subpixel located at the end in the first direction in the image display area is defined as a first subpixel, and the subpixel located at a position other than the end in the first direction in the image display area is the first subpixel. When an arbitrary subpixel that displays the same color as one subpixel is a second subpixel,
When image data of the same gradation is supplied from the outside to the first subpixel and the second subpixel, the brightness of the image displayed by the first subpixel is displayed by the second subpixel. An image display device characterized by being smaller than the brightness of the image. The subpixel adjacent to the first subpixel in the first direction is a third subpixel, and the subpixel is adjacent to the second subpixel in the first direction and displays the same color as the third subpixel. When the sub-pixel to be used is the fourth sub-pixel,
When image data of the same gradation is supplied from the outside to the third subpixel and the fourth subpixel, the brightness of the image displayed by the third subpixel is displayed by the fourth subpixel. The image display device according to claim 1, wherein the image display device is smaller than brightness of an image to be displayed.   The image display apparatus according to claim 2, wherein brightness of an image displayed by the sub-pixel is adjusted by changing an aperture ratio of the sub-pixel.   In one pixel, a red sub-pixel displaying red, a green sub-pixel displaying green, and a blue sub-pixel displaying blue are arranged in this order along the first direction. The image display device according to claim 3. At the end of the image display area where the red sub-pixel is the first sub-pixel and the green sub-pixel is the third sub-pixel, the aperture ratio of the red sub-pixel is Ar, and the aperture ratio of the green sub-pixel is The image display apparatus according to claim 4, wherein when Ag is used, the Ar and the Ag satisfy the following relational expression (1).
At the edge of the image display area where the blue sub-pixel is the first sub-pixel and the green sub-pixel is the third sub-pixel, the aperture ratio of the blue sub-pixel is Ab and the aperture ratio of the green sub-pixel is The image display apparatus according to claim 4, wherein, when Ag is defined, the Ab and the Ag satisfy the following relational expression (2).
At the end of the image display area where the red sub-pixel is the first sub-pixel and the green sub-pixel is the third sub-pixel, the aperture ratio of the red sub-pixel is Ar, and the aperture ratio of the green sub-pixel is The image display apparatus according to claim 4, wherein, when Ag, the Ar and the Ag satisfy the following relational expression (3).
At the edge of the image display area where the blue sub-pixel is the first sub-pixel and the green sub-pixel is the third sub-pixel, the aperture ratio of the blue sub-pixel is Ab and the aperture ratio of the green sub-pixel is The image display apparatus according to claim 4, wherein, when Ag is defined, the Ab and the Ag satisfy the following relational expression (4).
  An image processing unit that corrects image data input from the outside to the sub-pixel, and the brightness of the image displayed by the sub-pixel varies the correction amount of the image data by the image processing unit. The image display device according to claim 2, wherein the image display device is adjusted by the adjustment. The image processing unit is configured such that the gradation value of image data input from the outside is α _i , the maximum displayable gradation value is α _M , the γ value by gamma correction is γ, and the correction amount is β The image display device according to claim 9, wherein a gradation value α _o of the corrected image data input to the sub-pixel is determined based on the following formula (5).