JP6376764B2 - Display device and control method thereof - Google Patents

Description

  The present invention relates to a display device and a control method thereof.

  The liquid crystal display device includes a liquid crystal panel, a backlight disposed on the back side of the liquid crystal panel, a control circuit for controlling them, and the like. In recent years, when an image is displayed, a technique for improving the image quality such as improving the contrast and expanding the color gamut by adjusting the display characteristics of the display (for example, the luminance of the backlight) according to the color and luminance of the image (hereinafter, referred to as the image quality) Display high image quality technology) has been developed.

  A typical technique is local dimming. Local dimming is a technique in which a backlight is divided into a plurality of light emitting areas and the luminance of the light source is controlled for each light emitting area. Contrast can be improved by local dimming. Furthermore, as the light source of the backlight, an RGB-LED made up of three primary color LEDs, a red LED (R-LED), a green LED (G-LED), and a blue LED (B-LED), is used. The color gamut can be expanded by controlling the luminance. For example, when only the blue component is included in the image displayed in the display area of the liquid crystal panel corresponding to the light emitting area, it is possible to display an image with high color purity by causing only the B-LED to emit light. As described above, by causing only the necessary LEDs in the light emitting region to emit light, the color purity of each primary color is increased, and the color gamut of the display image can be expanded.

上記の式で分かるように、ＸＹＺ値は、表示装置の分光放射輝度によって決まる。 On the other hand, when matching colors between a plurality of display devices and display areas, color adjustment is performed so that the XYZ values match in the CIE-XYZ color system. The CIE-XYZ color system is a color system based on stimulus values by light of three primary colors (RGB). The wavelength of light is represented by λ, the color matching functions of R, G, B are x (λ), y (λ), z (λ), the spectral radiance of the display device is S (λ), and the normalization constant K To do. As shown below, the stimulation values X, Y, and Z of R, G, and B are obtained by integrating the product of the color matching function and spectral radiance of each color in the visible wavelength range (380 nm to 780 nm).

As can be seen from the above equation, the XYZ values are determined by the spectral radiance of the display device.

  By the way, a problem called observer metamerism is known. The observer metamerism is caused by the fact that the spectral sensitivity characteristics (visual sensitivity) of the eyes differ from person to person. In some cases, the spectral sensitivity characteristics of the eyes of an observer observing the display device are different from the standard spectral sensitivity characteristics (standard color matching function) of the eyes. In such a case, when the observer observes two regions that are color-matched based on the standard color matching function, if the spectral radiances of the two regions are different, depending on the spectral sensitivity characteristics of the observer, The color of the area may look different. This is recognized as color unevenness by this observer. In order to suppress color unevenness due to variations in spectral sensitivity characteristics by the observer, it is necessary to match the spectral radiance of the two regions.

  Conventional techniques for matching the spectral radiance of the display device are disclosed in, for example, Patent Document 1 and Patent Document 2. In the technique disclosed in Patent Document 1, in order to match colors between a plurality of devices, the spectral radiance of one device is approximated to the spectral radiance of the other device. Specifically, the spectral radiance of the six primary color display is adjusted by controlling the light emitting element, and approximated to the target to be matched. In the technique disclosed in Patent Document 2, in order to prevent color unevenness due to crosstalk between regions, the luminance of all the light emitting elements is controlled so that the light emission of each light emitting element approaches white light.

JP 2003-134351 A JP 2010-72360 A

  When the spectral radiance of the two areas is approximated by the above-described conventional technique, the color unevenness between the two areas can be suppressed, but the effect of improving the contrast by local dimming and improving the image quality of the color gamut expansion is diminished. .

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a technique capable of achieving both image quality improvement by local dimming and suppression of occurrence of color unevenness due to variation in spectral sensitivity characteristics for each observer in an image display device. To do.

The present invention comprises a light emitting means having a plurality of light emitting areas composed of light sources of a plurality of colors whose brightness can be controlled independently;
Display means for displaying an image by adjusting the transmittance of light from the light emitting means;
Storage means for storing a plurality of color matching functions corresponding to variations in spectral sensitivity characteristics of eyes due to individual differences;
Determining means for determining the luminance of each color of light source of the light emitting regions in accordance with the feature quantity of the image area corresponding to the light emitting regions,
Based on said each of the plurality of color matching functions, calculating a color difference between the appearance of two Keru you in the light-emitting area the color of the pixel corresponding to two image areas containing both the predetermined color matching satisfying color pixel Then, when the difference calculated based on at least one color matching function among the plurality of color matching functions is equal to or greater than the first threshold when compared with the first threshold, the light sources of the two light emitting regions Correction means for correcting the brightness;
It is a display apparatus provided with.

The present invention comprises a light emitting means having a plurality of light emitting areas composed of light sources of a plurality of colors whose brightness can be controlled independently;
Display means for displaying an image by adjusting the transmittance of light from the light emitting means;
A display device control method comprising:
A determination step of determining the luminance of each color of light source of the light emitting regions in accordance with the feature quantity of the image area corresponding to the light emitting regions,
An acquisition step of acquiring information on the color matching functions from a storage unit that stores a plurality of color matching functions corresponding to variations in the spectral sensitivity characteristics of the eye due to individual differences;
Based on said each of the plurality of color matching functions, calculating a color difference between the appearance of two Keru you in the light-emitting area the color of the pixel corresponding to two image areas containing both the predetermined color matching satisfying color pixel Then, when the difference calculated based on at least one color matching function among the plurality of color matching functions is equal to or greater than the first threshold when compared with the first threshold, the light sources of the two light emitting regions A correction process for correcting the brightness;
It is the control method of the display apparatus which has this.

  According to the present invention, the image display apparatus can achieve both high image quality by local dimming and suppression of occurrence of color unevenness due to variations in spectral sensitivity characteristics for each observer.

The figure which represented typically the structure of the image display apparatus 1 of Example 1. FIG. Schematic diagram showing the arrangement of the light sources of the backlight 101 of the first embodiment. 1 is a block diagram illustrating a configuration of an image display device 1 according to a first embodiment. Example of pixel count histogram of all colors in the light emitting region 102 of the first embodiment Example of representative color and color similarity information table in embodiment 1 Comparison chart of standard color matching function, personal color matching function 1 and personal color matching function 2 of Example 1 Processing Flow of Backlight Brightness Determination Unit 17 of Embodiment 1 Relative value of each LED emission characteristic and color filter transmission characteristic of Example 1 Item Example of Input Image and Color Similarity Information Table in Embodiment 1 Backlight luminance before correction, similar color spectral radiance, color difference of Example 1 Backlight luminance after correction of Example 1, similar color spectral radiance, color difference Processing Flow of Backlight Brightness Determination Unit 17 of Embodiment 2 Example of distance k and reference color difference kΔE _base between region 6 and each region in Example 2 The figure which showed the vicinity area | region of the area | region 6 of Example 3.

Hereinafter, specific embodiments of the image display device and the control method thereof according to the present invention will be described.
Example 1
FIG. 1 is a diagram schematically illustrating the structure of an image display device 1 according to the first embodiment of the invention. As shown in FIG. 1, the image display apparatus 1 includes a backlight 101, a diffusion plate 201, an optical sheet 202, a liquid crystal panel 301, and the like. The light emitted from the backlight 101 is diffused by the diffusion plate 201, and the light directivity is adjusted by the optical sheet 202, and is incident on the back surface of the liquid crystal panel 301.

  The liquid crystal panel 301 includes a pixel having a liquid crystal element capable of adjusting the transmittance of incident light, and a color filter provided for each pixel. The color filter is composed of red, green, and blue color filters (R-CF, G-CF, B-CF). Each color filter transmits only light of each wavelength of red light, green light, and blue light. Blocks light of wavelengths other than. An image based on the image data is displayed on the liquid crystal panel 301 by adjusting the transmittance of light transmitted through the liquid crystal element for each pixel in accordance with the image data.

FIG. 2 is a schematic diagram showing the arrangement of the light sources of the backlight 101. The backlight 101 is composed of 16 light emitting areas 102 as indicated by broken lines, and a light source R-LED 103 a, G-LED 103 b, and B-LED 103 c is provided for each light emitting area 102. That is, the backlight 101 has a plurality of light-emitting areas each composed of light sources of a plurality of colors whose brightness can be controlled independently. The light source R-LED 103a is an LED that emits red light, the light source G-LED 103b is an LED that emits green light, and the light source B-LED 103c is an LED that emits blue light. The backlight 101 can control the luminance of each color LED for each light emission unit, with one or more light emission regions 102 as one light emission unit. For each light emitting unit, the transmittance of the liquid crystal element in the region of the liquid crystal panel 301 corresponding to the light emitting unit is controlled based on the luminance of the light emitting unit. As a result, according to the image displayed in the area corresponding to the light emission unit, only the light source of the necessary color is emitted for each light emission unit, or the light intensity is emitted with the necessary luminance, so that the color purity of the display image is improved. By improving, the display color gamut is expanded and the contrast can be improved. In Example 1, it is assumed that the backlight 101 emits light with a luminance determined for each light emitting unit, with one light emitting region 102 serving as one light emitting unit.

  FIG. 3 is a block diagram illustrating the configuration of the image display device 1 according to the first embodiment of the invention. The image data input unit 11 receives image data (image signal) output from an image output device such as a personal computer. The input image data is output to the gradation level calculation unit 12, the image processing unit 13, and the color similarity region determination unit 15.

  The gradation degree calculation unit 12 calculates the gradation degree L for the pixel values of the three primary colors of the image displayed in the area of the liquid crystal panel 301 corresponding to each light emitting area 102 of the backlight 101. The gradation L is calculated by the maximum gradation value n / maximum gradation value × 100 in the light emitting area for each of the RGB pixel values of the pixels in the light emitting area 102. The maximum gradation value n in the light emitting area is the maximum value among the pixel values of the pixels in the light emitting area 102. The maximum gradation value is a constant determined by the gradation accuracy. For example, in the first embodiment, the maximum gradation value is 255 because 8-bit accuracy is used.

The maximum gradation value n in the red (R) light emitting area of a pixel in a certain light emitting area 102 is 50, the maximum gradation value n in the green (G) light emitting area is 20, and the maximum floor in the blue (B) light emitting area. It is assumed that the adjustment value n is 110. In this case, the gradations L _R , L _G , and L _B of the three primary colors RGB in the light emitting region 102 are as follows.

L _R = 50/255 × 100 = 19.6
L _G = 20/255 × 100 = 7.8
L _B = 110/255 × 100 = 43.1

Gradient calculation unit 12, for all the light-emitting region 102, the three primary colors respectively grayscales _{L R,} L G, and calculates the _{L B,} and outputs to the backlight luminance determining unit 17.

  When the backlight luminance is input from the backlight luminance determining unit 17, the image processing unit 13 performs image processing on the image data input from the image data input unit 11 for each light emitting area 102, and the image after image processing is performed. Data is output to the liquid crystal panel 301. In this image processing, the RGB gradation values corresponding to the backlight luminance are expanded so that the colors of the same color pixels (CIEXYZ values obtained by the standard color matching function) match between the light emitting regions 102 having different backlight luminances. Etc. are calculated.

  The backlight control unit 14 controls the luminance of the light source R-LED 103a, G-LED 103b, and B-LED 103c of the backlight 101 for each light emitting area 102 based on the backlight luminance input from the backlight luminance determining unit 17. Control information is generated. The backlight control unit 14 outputs backlight control information to the backlight 101 and controls light emission of the backlight 101.

  The color similarity region determination unit 15 is a color that is included in the plurality of light emitting regions 102 and may be recognized by the observer as color unevenness (the color in each light emitting region is originally the same, but different colors). Can be recognized). The color similarity region determination unit 15 outputs the determination result to the backlight luminance determination unit 17 as a color similarity information table.

First, the color similarity region determination unit 15 analyzes the pixel number histogram of all colors included in the light emitting region 102 for each light emitting region 102. Then, a color with a frequency that has a predetermined threshold (the threshold is 50 pixels in the first embodiment) that the observer may recognize as color unevenness (
It is determined as a representative color of each light emitting area 102

  FIG. 4 shows an example of a pixel count histogram of all colors in a certain light emitting area 102, and FIG. 5A is a list of examples of representative colors determined by the color similar area determining unit 15 for each light emitting area 102. It is shown. As shown in FIGS. 4 and 5A, a plurality of representative colors may or may not exist.

  Next, the color similar area determination unit 15 compares the representative colors of the two light emitting areas 102, and determines that the representative color is “similar color” when both include the same representative color. Further, when there is a color that is a similar color in relation to the other light emitting area 102 among the representative colors, the light emitting area 102 and the other light emitting area 102 are determined as “color similar areas”. In other words, the color similar region determination unit 15 determines two light emitting regions that include pixels having a color condition that satisfies the equal color condition as a color similar region. The color similarity region determination unit 15 stores the determination result of the similar color and the color similarity region in the color similarity information table. The color similarity region determination unit 15 performs the determination of the “similar color” and the “color similarity region” for all combinations of the light emitting regions 102, stores the determination result in the color similarity information table, and the color similarity information table. Create

  In the above example, the conditions for determining similar colors (color matching conditions) are the same in RGB values, but the color matching conditions are not limited to this. For example, the color matching condition may be that the distance in the RGB space between the representative color of one light emitting area 102 and the representative color of another light emitting area 102 is less than a threshold value (for example, 10). Two light emitting areas 102 including both pixels of a color satisfying the equal color condition are determined as color similar areas.

  FIG. 5B is an example of a color similarity information table. The identification information of two light emitting regions 102 having “No.” indicating a similar color identification number and representative colors (similar colors) satisfying the similarity condition are shown. “Color similarity region” shown, and “similar color” items showing RGB components of similar colors. FIG. 5B is an example, and the RGB values of similar colors and the number of similar colors differ depending on the image.

  The color matching function management unit 16 stores information on a plurality of color matching functions corresponding to variations in the spectral sensitivity characteristics of the eyes due to individual differences, which are different from the standard color matching functions used for determining the luminance of the backlight. In the first embodiment, the color matching function management unit 16 holds two color matching functions (personal color matching function 1 and personal color matching function 2) different from the standard color matching function. FIG. 6 is a comparison diagram of the standard color matching function, the personal color matching function 1, and the personal color matching function 2. As shown in FIG. 6, the individual color matching function has a spectral sensitivity characteristic different from the standard color matching function, and different personal color matching functions also have different spectral sensitivity characteristics. The number of personal color matching functions held by the color matching function management unit 16 is not limited to two.

  In order to be able to deal with a wide range of variations in color matching functions due to individual differences, it is preferable to store information on a plurality of personal color matching functions that have significantly different spectral sensitivity characteristics. For example, among color matching functions that vary depending on individual differences, a color matching function having a spectral sensitivity peak on the shorter wavelength side and a color matching function on the longer wavelength side may be included. Further, the data of the personal color matching function managed by the color matching function management unit 16, the type of personal color matching function, the presence / absence of use, etc. may be editable from the outside (for example, a personal computer).

  The backlight luminance determination unit 17 acquires the gradation of each light emitting region 102 acquired from the gradation calculation unit 12, the color similarity information table acquired from the color similar region determination unit 15, and the color matching function management unit 16. The backlight luminance is determined based on the color function. A method for determining the backlight luminance will be described later. The backlight luminance determining unit 17 outputs the determined backlight luminance to the image processing unit 13 and the backlight control unit 14.

  The backlight 101 emits the light source 103 of each color based on the backlight control information input from the backlight control unit 14. Each color light source 103 a, 103 b, 103 c in each light emitting area 102 of the backlight 101 emits light based on the backlight luminance control information determined for each light emitting area 102.

  In the liquid crystal panel 301, the transmittance of each liquid crystal element is controlled for each pixel based on the image data after image processing input from the image processing unit 13, and the light emitted from the backlight 101 is transmitted with the transmittance. Thus, an image based on the image data is displayed.

Next, a processing flow of the backlight luminance determination unit 17 will be described with reference to FIG.
When the backlight luminance determination unit 17 acquires the gradation in each light emitting region 102 from the gradation calculation unit 12 and the color similarity information from the color similarity region determination unit 15, the backlight luminance determination unit 17 obtains the color matching function from the color matching function management unit 16. Obtain (S101).

  The backlight luminance determining unit 17 calculates the initial backlight luminance from the obtained gradation in each light emitting region 102 (S102). The initial backlight luminance is the luminance of the light source 103 in each light emitting region 102 determined by the same method as in conventional local dimming. In the first embodiment, for example, when the gradation level of R is 80, the initial backlight of the light source 103 in the light emitting area 102 is based on the gradation degree of the light emitting area 102 so that the luminance of the light source R-LED 103a is 80%. Determine the brightness. Note that the method of determining the initial backlight luminance is not limited to this, and any method may be used as long as it determines the initial backlight luminance of the light sources of the respective colors in the light emitting region 102 according to the feature amount of the image in the region corresponding to the light emitting region 102. . For example, the initial backlight luminance may be determined based on the gradation obtained by multiplying the coefficient.

  The backlight luminance determination unit 17 sets the smallest identification number in the color similarity information table as a reference number, and refers to information on a similar color corresponding to the reference number (S103).

  The backlight luminance determining unit 17 calculates (or measures) the spectral radiance (spectrum) of the similar color in the color similar region (two light emitting regions 102) corresponding to the reference number (S104). When calculating the spectral radiance, the backlight luminance determining unit 17 calculates the similar color based on the emission characteristics of each LED, the current luminance of each LED, the transmission characteristics of the color filter, the RGB value (color filter transmittance), and the like. Calculate the spectral radiance. FIG. 8 is a diagram showing the relative values of the light emission characteristics of each color LED (R-LED, G-LED, B-LED) and the transmission characteristics of each color filter (R-CF, G-CF, B-CF). It is. Alternatively, the backlight luminance determining unit 17 may actually display a similar color in each of the color similar regions, measure the spectral radiance with an external spectrocolorimeter that can measure the spectral radiance, and obtain a measurement value.

The backlight luminance determining unit 17 uses the individual color matching function 1 and the spectral radiance of the similar color in each of the color similar regions, so that an individual having the sensitivity of the personal color matching function 1 sees the similar color in each of the color similar regions. calculating the color difference Delta] E ₁ when the (S105). The backlight luminance determining unit 17 calculates an XYZ value from the result of integrating the spectral reflection luminance of the similar color and the personal color matching function 1 in each color similar region, and converts it into an L * a * b * value. The backlight luminance determining unit 17 calculates a difference between the obtained L * a * b * values (a distance between two points in the L * a * b * space) to calculate a color difference ΔE of similar colors between the color similar regions. . Here, ΔE is used as the color difference in the first embodiment. However, ΔEa * b * may be used as the color difference according to the purpose, and the color difference is calculated using another color system such as the L * C * h color system. You may do it.

Similarly to S105, the backlight luminance determination unit 17 determines that the individual having the sensitivity of the personal color matching function 2 uses the color similarity region from the individual color matching function 2 and the spectral radiance of the similar color in each of the color similar color regions. The color difference ΔE ₂ when viewed in each of the above is calculated (S106).

The backlight luminance determining unit 17 compares the color difference ΔE ₁ and the color difference ΔE ₂ with the reference color difference ΔE _base . Here, the reference color difference ΔE _base is a threshold value (first threshold value) for determining the difference in appearance color that the user recognizes as color unevenness. In the first embodiment, ΔE _base = 2.0. If at least one of the color difference ΔE ₁ and the color difference ΔE ₂ is greater than or equal to the reference color difference ΔE _base (greater than or equal to the first threshold), the backlight luminance determination unit 17 proceeds to S108, and otherwise proceeds to S109 (S107). ).

If at least one of the color difference ΔE ₁ and the color difference ΔE ₂ is greater than or equal to the reference color difference ΔE _{base in} S107, the backlight luminance determining unit 17 corrects the backlight luminance of each color-similar region (S108). Here, the brightness of each color LED in each color-similar area is compared, and correction is made in the direction of increasing the smaller brightness. For example, the backlight luminance in one of the color-similar regions is R-LED 80%, G-LED 50%, and B-LED 30%, and the backlight luminance in the other color-similar region is R-LED 20%, G-LED 50%. , B-LED 70%. At this time, a difference of 60% in the R-LED and 40% in the B-LED occurs in the backlight luminance between the color similar regions. In the first embodiment, 10% of the difference in backlight luminance, that is, in the above example, the R-LED is 6% and the B-LED is 4% as a unit correction amount. Add the light brightness by the unit correction amount. Then, the corrected backlight luminance is R-LED 80%, G-LED 50%, and B-LED 34% in one of the color-similar areas, and R-LED 26%, G-LED 50%, B-in the other of the color-similar areas. -LED 70%. Such correction processing is repeated until both the color difference ΔE ₁ and the color difference ΔE ₂ are less than the reference color difference ΔE _{base in} the comparison in S107. Accordingly, it is possible to suppress the occurrence of color unevenness between color similar regions due to variations in individual spectral sensitivity characteristics while suppressing a reduction in image quality improvement effect due to local dimming.

When the color difference ΔE ₁ and the color difference ΔE ₂ are both less than the reference color difference ΔE _{base in} S107, the backlight luminance determination unit 17 determines that the color unevenness of the similar color in the color similar region with the reference number is an acceptable level. The reference number is incremented (S109).

  The backlight luminance determining unit 17 compares the reference number with the maximum value of the identification number in the color similarity information table, and if the reference number has reached the maximum value, the process proceeds to S111, and if not, the process proceeds to S104. (S110).

  The backlight luminance determination unit 17 outputs the determined backlight luminance to the image processing unit 13 and the backlight control unit 14 (S111).

Next, a specific example in the case where the processing of S104 to S109 in FIG. 7 is applied to a similar color with a certain reference number in the color similarity information table will be described.
FIG. 9A shows an input image example. FIG. 9B shows a color similarity information table created by the color similarity region determination unit 15 performing similar color determination on the input image of FIG. 9A. Here, only the item of the identification number n used for description is described, and description of other items is omitted. In the identification number n, the color similarity region is “region 10 and region 11”, the similarity color is “(3, 7, 181)”, and the color contains a lot of blue components.

FIG. 10A shows each of the color similarity regions (regions) before correcting the backlight luminance based on the information in the color similarity information table using the identification number n as a reference number (executing S104 to S109 in FIG. 7). 10 and area 11). Here, the R gradation degree of the region 10 is 0%, the G gradation degree is 10%, and the B gradation degree is 100%. The R gradation degree of the region 11 is 0%, the G gradation degree is 80%, and the B gradation degree is 100%. %. Due to local dimming, in the region 10 where the B gradation is 100%, the luminance of the B-LED increases at 100%, and the B gradation is 100%.
% And G gradation is 80%, the luminance of the G-LED is 80% and the luminance of the B-LED is 100%.

  FIG. 10B shows the result of calculating the spectral radiance when the similar color (3, 7, 181) is displayed in the region 10 and the region 11 in S104 of FIG. The spectral radiance of the similar color in the region 10 is substantially constituted by the light emission characteristics of the B-LED, whereas the spectral radiance of the similar color in the region 11 is affected by the light emission of the G-LED. The characteristics are different with respect to the spectral radiance at.

  This is a phenomenon that occurs when the transmission wavelength range of B-CF includes the emission wavelength range of G-LED. In such a case, XYZ values calculated using the standard color matching function can be matched by performing image processing for reducing the transmittance of the B-CF. For example, (3, 7, 181) in area 11 is corrected to (3, 7, 171) by image processing. In FIG. 10B, the backlight luminance of the area 10 is set as shown in FIG. 10A, and the calculation is performed using the standard color matching function when the RGB values are (3, 7, 181). XYZ values are shown. Further, the XYZ values calculated using the standard color matching function when the backlight luminance of the area 11 is set as shown in FIG. 10A and the RGB values are (3, 7, 171) after correction are obtained. Show. As shown in FIG. 10B, the XYZ values calculated using the standard color matching function are X = 10, Y = 10, and Z = 80 for both the area 10 and the area 11. That is, the same color (here, (3, 7, 181)) in two regions having different spectral radiances can be matched with the XYZ values calculated using the standard color matching function by image processing.

Next, in S105 and S106 in FIG. 7, the results of calculating the color difference Delta] E ₁ of similar color in the region 10 and the region 11 using a personal color matching functions 1 and, individual color matching function 2 region 10 and the region 11 using FIG. 10C shows the result of calculating the color difference ΔE ₂ of similar colors in FIG. As shown in FIG. 10C, the color difference ΔE ₁ of similar colors calculated using the personal color matching function ₁ is 2.5, and the color difference ΔE ₂ of similar colors calculated using the personal color matching function ₂ is 0. 8

In S107 of FIG. 7, when the color difference ΔE ₁ and the color difference ΔE ₂ are compared with the reference color difference ΔE _base (= 2.0), the color difference ΔE ₁ is equal to or greater than the reference color difference ΔE _base (= 2.0). The determination unit 17 proceeds to S108.

  In S108 of FIG. 7, the backlight luminance determination unit 17 corrects the backlight luminance. When the backlights of the region 10 and the region 11 are compared, a difference of 70% is generated in the G-LED luminance. Therefore, the backlight luminance determination unit 17 determines 7% which is 10% of the difference as a unit correction amount. , The G-LED brightness of region 10 is added to 10%. FIG. 11A shows the backlight luminance after correction. The backlight luminance of the corrected region 10 is increased by 17% for the G-LED.

  FIG. 11B shows the result of calculating the spectral radiance of the similar color in the region 10 and the region 11 based on the corrected backlight luminance in FIG. It can be seen that the spectral radiance characteristic of the region 10 approaches the spectral radiance characteristic of the region 11 by increasing the luminance of the G-LED. Again, although the spectral radiances between the regions are different, the XYZ values calculated by the standard color matching function by image processing are the same.

Next, in S105 and S106 in FIG. 7, the results of calculating the color difference Delta] E ₁ of similar color in the region 10 and the region 11 using a personal color matching functions 1 and, individual color matching function 2 region 10 and the region 11 using FIG. 11C shows the result of calculating the color difference ΔE ₂ of similar colors in FIG. As shown in FIG. 11C, the color difference ΔE ₁ of the similar color calculated using the personal color matching function ₁ is 1.7, and the color difference ΔE ₂ of the similar color calculated using the personal color matching function ₂ is 0.8. 5 It can be seen that both the color difference ΔE ₁ and the color difference ΔE ₂ decrease as the spectral radiances of the region 10 and the region 11 approach each other.

In S107 of FIG. 7, for the color difference Delta] E ₁ and color difference Delta] E ₂ are both less than the reference color difference ΔE _base (= 2.0), the backlight luminance determining unit 17, based on the similar color and color similar area of the reference number n It is determined that the backlight brightness correction has been completed. Then, the process proceeds to S109 to increment the reference number.

  As described above, in the first embodiment, the backlight luminance is corrected for each similar color and each region including the similar color until the color difference due to the variation in the individual spectral sensitivity characteristics becomes smaller than the threshold value. As a result, the backlight luminance is corrected so that the spectral radiance between the regions is brought close to only the light-emitting region including a similar color having a large color difference due to variations in individual spectral sensitivity characteristics. Backlight luminance correction for reducing the color difference is not performed for the light emitting region including a similar color that does not have a large color difference due to variations in individual spectral sensitivity characteristics. Therefore, it is possible to suppress the reduction in image quality improvement effect due to local dimming while suppressing the occurrence of color unevenness due to variations in individual spectral sensitivity characteristics.

(Example 2)
In the first embodiment, the example in which the reference value at the time of color difference determination is the same for all color similar regions has been described. In the second embodiment, by changing the reference value at the time of color difference determination according to the distance between the regions, it is possible to further suppress the reduction in image quality due to the local dimming by the backlight luminance correction processing. explain. Note that description of the same processing as in the first embodiment is omitted.
A processing flow of the backlight luminance determination unit 17 according to the second embodiment will be described with reference to FIG. In addition, since the process of S101-S111 is the same process as Example 1, description is abbreviate | omitted.

The backlight luminance determining unit 17 weights the reference color difference ΔE _base (= 2.0) based on the distance between the color similar regions (S201). The backlight luminance determination unit 17 calculates the distance k between the color similar regions by setting the distance between adjacent regions to 1, and multiplies the reference color difference ΔE _base (= 2.0) to weight the reference color difference. Perform. FIG. 13A is a diagram illustrating distances k to the respective regions when the region 6 is used as a reference. For example, the distance k between the region 6 and the region 16 is 2.8. FIG. 13B is a diagram showing a reference color difference kΔE _base that is used when color difference determination is performed with respect to each region with the region 6 as a reference. For example, if the color similarity region is the region 6 and the region 16, the reference color difference 5.7 weighted by the weight k = 2.8 is used in the color difference determination of S107 in S201 of FIG. In Example 2, the reference color difference is increased as the distance between the two light emitting regions is increased. For this reason, if the color-similar areas are distant light-emitting areas, a negative determination (No) is made in S107 even if the color difference between the similar-color-similar areas is somewhat large, and the backlight luminance correction is not executed. This is because even if there is a color difference between light emitting regions that are far away from each other, it is difficult to be recognized as color unevenness.

  As described above, weighting the reference value at the time of color difference determination according to the distance between the areas reduces the amount of backlight brightness correction between the color-similar areas that are far away from each other, resulting in high image quality by local dimming. The effect is not easily reduced.

(Example 3)
In the first embodiment, the example in which the color similarity determination is performed on all combinations of the color similarity regions has been described. In the third embodiment, the color similarity determination is performed only for the color similarity region that is a combination of the light emitting regions in the vicinity, thereby further suppressing the reduction in the image quality improvement effect due to the local dimming by the backlight luminance correction process. Explain that you can. In addition,
A description of the same processing as in the first embodiment will be omitted.

  In FIG. 3, the color similarity region determination unit 15 determines colors that are included in the plurality of light emitting regions 102 and may be recognized by the observer as color unevenness, and the determination results are backed up as a color similarity information table. Output to the light luminance determination unit 17. Here, the color similarity region determination unit 15 performs the same “similar color” and “color similarity region” determination as in the first embodiment only on the combination of the light emitting regions 102 that are close to each other. Create an information table. Here, the light emitting region in the vicinity is a light emitting region in which the distance between adjacent light emitting regions is 1, and the distance between the light emitting regions is less than 2. FIG. 14 is a diagram showing the vicinity region of the region 6. In the third embodiment, eight regions 1, 2, 3, 5, 7, 9, 10, and 11 indicated by oblique lines are the vicinity of the region 6. It becomes an area. It should be noted that the distance threshold (second threshold) used for determining whether or not the region is the vicinity region is not limited to the above example. Further, the method for determining whether or not the region is the vicinity region is not limited to the above example.

  As described above, according to the third embodiment, only the combination of the neighboring regions is set as the target of the color similarity determination, thereby suppressing the color similarity determination and the backlight luminance correction between the light emitting regions that are separated from each other. Thereby, it can suppress that the image quality improvement effect by local dimming is attenuated by correction of backlight luminance.

In each of the above embodiments, an example in which the display device is a transmissive liquid crystal display device has been described. However, the display device is not limited to a transmissive liquid crystal display device. The display device may be a display device having a display panel that transmits light from the backlight with a transmittance according to image data. For example, the display device may be a MEMS shutter type display using a MEMS (Micro Electro Mechanical System) shutter instead of the liquid crystal element.

  In each of the above-described embodiments, when the color difference between the color similar regions of similar colors is equal to or greater than the threshold value, the correction is performed to increase the luminance of the LED having the lower luminance among the LEDs of the same color in the color similar region. However, the correction may be to reduce the luminance of the LED having the higher luminance. What is necessary is just to correct | amend the brightness | luminance of LED of the same color between color similar areas. Thereby, even if the spectral radiance between the color similar regions approaches and the color matching function varies due to individual differences, it is possible to suppress the recognition of color unevenness between the color similar regions. In addition, although the example in which the luminance correction is performed using 10% of the luminance difference as a correction unit has been described, the correction method is not limited to this, for example, a predetermined correction amount is used as a unit.

  In each of the above embodiments, the example in which the present invention is applied to the liquid crystal display device having one each of the three primary color LEDs as the backlight light source has been described, but the configuration of the backlight light source is not limited thereto. For example, a plurality of LEDs may be provided for any of the three primary colors, or LEDs of colors other than the three primary colors may be provided. Moreover, the light emitting element which comprises a light source is not restricted to LED. The method for realizing the light emission of the three primary colors or more may be a method in which light emitting elements such as LEDs corresponding to the respective colors are provided in each light emitting region as in the above embodiment, but is not limited thereto. For example, a light source member capable of wavelength conversion by excitation, for example, a light source member that generates at least one of red light, green light, and blue light by ultraviolet light, or a combination of such a light source member and an LED may be used. . For controlling the light emission luminance of the LED, a method of adjusting the duty ratio between the lighting period and the extinguishing period by PWM control, a method of adjusting the current value to be applied, or the like can be adopted.

<Other embodiments>
The present invention is a system that performs one or more functions described in the above-described embodiments by reading and executing a computer-executable instruction recorded in a computer-readable recording medium that holds data temporarily. It can also be implemented by a computer of the apparatus. The present invention is also a method performed by a computer of a system or apparatus. For example, one or more functions described in the above-described embodiments of the present invention are performed by reading and executing instructions executable by the computer from a storage medium. The method can also be carried out. The computer includes one or more CPUs (central processing units), MPUs (micro processing units), and other circuits. Furthermore, a network of a plurality of separate computers or separate computer processors may be included. The instructions executable by the computer may be provided to the computer from, for example, a network or a storage medium. The storage medium may include, for example, one or more hard disks, random-access memory (RAM), read only memory (ROM), and a storage device of a distributed computing system. The storage medium may also include an optical disc (for example, a CD (compact disc), a DVD (digital versatile disc), a BD (Blu-ray Disc)), a flash memory, and a memory card. Although the invention has been described with reference to examples, it should be understood that the invention is not limited to the disclosure of the examples. The present invention should be construed most broadly to encompass all modifications and equivalent structures and functions within the scope of the present invention.

15: Color similarity region determination unit, 16: Color matching function management unit, 17: Backlight luminance determination unit, 101: Backlight, 301: Liquid crystal panel

Claims (26)

A light-emitting means having a plurality of light-emitting areas composed of light sources of a plurality of colors whose brightness can be controlled independently;
Display means for displaying an image by adjusting the transmittance of light from the light emitting means;
Storage means for storing a plurality of color matching functions corresponding to variations in spectral sensitivity characteristics of eyes due to individual differences;
Determining means for determining the luminance of each color of light source of the light emitting regions in accordance with the feature quantity of the image area corresponding to the light emitting regions,
Based on said each of the plurality of color matching functions, calculating a color difference between the appearance of two Keru you in the light-emitting area the color of the pixel corresponding to two image areas containing both the predetermined color matching satisfying color pixel Then, when the difference calculated based on at least one color matching function among the plurality of color matching functions is equal to or greater than the first threshold when compared with the first threshold, the light sources of the two light emitting regions Correction means for correcting the brightness;
A display device comprising:   The correction means increases the brightness of the light source of the two light emitting areas for each color so that the difference in brightness between the two light emitting areas is reduced for each color, or The display device according to claim 1, wherein correction is performed to reduce the luminance of the light source having the higher luminance. In the two light emitting areas corresponding to the two image areas including both of the color pixels satisfying the color matching condition, the correction unit may determine which of the plurality of color matching functions has a difference in appearance color of the color pixel. 3. The display device according to claim 1, wherein, even when a color matching function is applied, the luminance of the light sources of the two light emitting regions is not corrected when the function is smaller than the first threshold value. The said correction | amendment means performs the said correction | amendment about all the combinations of the two light emission area | regions corresponding to the two image area | regions which include the pixel of the color which satisfy | fills the said color matching conditions. Display device. The correction means, of the combination of the two light emitting regions corresponding to two image areas containing both pixels of the color matching conditions are satisfied color, the distance between the two light emitting regions only for small combinations than the second threshold value The display device according to claim 1, wherein the correction is performed. The said correction | amendment means performs the said correction | amendment about two light emission area | regions corresponding to two image areas which contain the pixel of the color which satisfy | fills the said color matching condition more than a 3rd threshold value. Display device.   The display device according to claim 1, wherein the correction unit changes the first threshold value according to a distance between the two light emitting regions.   The display device according to claim 7, wherein the correction unit increases the first threshold value as the distance between the two light emitting regions increases.   For each of the two light-emitting areas, the correction unit includes the luminance of the light source of each color determined by the determination unit, the pixel value of a pixel of a color that satisfies the color matching conditions, and the color matching acquired from the storage unit The display device according to claim 1, wherein an appearance color of a pixel of the color is obtained by calculation based on the function, and the difference in the appearance color is compared with the first threshold value.   The correcting means emits light from each color light source at the brightness determined by the determining means for each of the two light emitting areas and displays pixels of the color satisfying the color matching conditions. Obtain a measurement value of the spectral radiance of the display means by a colorimeter, obtain an appearance color of the pixel of the color by calculation based on the obtained measurement value and the color matching function obtained from the storage means, The display device according to claim 1, wherein a difference in appearance color is compared with the first threshold value. The storage unit stores a plurality of color matching functions including a color matching function having a spectral sensitivity peak on a shorter wavelength side and a color matching function on a longer wavelength side among color matching functions that vary depending on individual differences. The display device according to claim 1. The determining means determines a luminance of a light source of each color of each light emitting region according to a feature amount of an image region corresponding to each light emitting region using a standard color matching function,
The display device according to claim 1, wherein the correction unit calculates the color difference based on each of a plurality of color matching functions different from the standard color matching function. The correction means repeats the correction until the color difference calculated using any color matching function of the plurality of color matching functions is smaller than the first threshold. The display device according to item. A light-emitting means having a plurality of light-emitting areas composed of light sources of a plurality of colors whose brightness can be controlled independently;
Display means for displaying an image by adjusting the transmittance of light from the light emitting means;
A display device control method comprising:
A determination step of determining the luminance of each color of light source of the light emitting regions in accordance with the feature quantity of the image area corresponding to the light emitting regions,
An acquisition step of acquiring information on the color matching functions from a storage unit that stores a plurality of color matching functions corresponding to variations in the spectral sensitivity characteristics of the eye due to individual differences;
Based on said each of the plurality of color matching functions, calculating a color difference between the appearance of two Keru you in the light-emitting area the color of the pixel corresponding to two image areas containing both the predetermined color matching satisfying color pixel Then, when the difference calculated based on at least one color matching function among the plurality of color matching functions is equal to or greater than the first threshold when compared with the first threshold, the light sources of the two light emitting regions A correction process for correcting the brightness;
A method for controlling a display device. In the correction step, the brightness of the light source of the two light emitting areas is increased for each color so that the difference in brightness between the two light emitting areas is reduced, or The method of controlling a display device according to claim 14 , wherein correction is performed to reduce the luminance of the light source having the higher luminance. In the correction step, in two light emitting regions corresponding to two image regions including both pixels of a color satisfying the color matching condition, a difference in appearance color of the pixel of the color is determined by which of the plurality of color matching functions. when the color matching function smaller than said even when applying the first threshold value, the control method of a display device according to claim 14 or 15 does not correct the luminance of the light source of the two light emitting regions. The correction process according to any one of claims 14 to 16 , wherein, in the correction step, the correction is performed for all combinations of two light emitting areas corresponding to two image areas including both pixels of a color satisfying the color matching condition. Display device control method. Wherein the correction step, of the combination of the two light emitting regions corresponding to two image areas containing both pixels of the color matching conditions are satisfied color, the distance between the two light emitting regions only for small combinations than the second threshold value control method for a display device according to any one of claims 14 to 16 for the correction. The correction in the step, according to any one of claims 14 to 16 for the correction for the two light emitting regions corresponding to the two image areas of pixels of the color matching conditions are satisfied color containing both above the third threshold Display device control method. The display device control method according to any one of claims 14 to 19 , wherein, in the correction step, the first threshold value is changed according to a distance between the two light emitting regions. 21. The display device control method according to claim 20 , wherein in the correction step, the first threshold value is increased as a distance between the two light emitting regions is increased. In the correction step, for each of the two light emitting areas, the luminance of the light source of each color determined in the determination step, the pixel value of the pixel of the color satisfying the color matching condition, and the color matching acquired from the storage unit The display device according to any one of claims 14 to 21 , wherein an appearance color of a pixel of the color is obtained by calculation based on a function, and the difference in the appearance color is compared with the first threshold value. Control method. In the correcting step, for each of the two light emitting regions, an external spectroscopic measurement is performed when the light source of each color is emitted with the luminance determined in the determining step and the color pixel satisfying the color matching condition is displayed. Obtain a measurement value of the spectral radiance of the display means by a colorimeter, obtain an appearance color of the pixel of the color by calculation based on the obtained measurement value and the color matching function obtained from the storage means, The display device control method according to any one of claims 14 to 21 , wherein a difference in appearance color is compared with the first threshold value. The storage unit stores a plurality of color matching functions including a color matching function having a spectral sensitivity peak on a shorter wavelength side and a color matching function on a longer wavelength side among color matching functions that vary depending on individual differences. The control method of the display apparatus of any one of Claims 14-23. The determining step uses a standard color matching function to determine the luminance of the light source of each color in each light emitting area according to the feature amount of the image area corresponding to each light emitting area,
The correction step is based on each of a plurality of color matching functions different from the standard color matching function.
The method for controlling a display device according to any one of claims 14 to 24, wherein the difference is calculated. 26. The correction process according to any one of claims 14 to 25, wherein the correction step repeats the correction until the color difference calculated using any color matching function of the plurality of color matching functions is smaller than the first threshold value. The display device control method according to the item.

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