JP2019101189A - Image display unit and image display method - Google Patents

Abstract

To suppress color gamut expansion effect from decreasing owing to filter processing.SOLUTION: An image display unit according to the present invention has: light emitting means which has a light source group consisting of a plurality of light source parts differing in light emission color; display means which displays an image by modulating light that the light emitting means emits according to image data; and control means which sets first light emission intensity of each light source part, color by color, based upon a first feature quantity associated with lightness of a color of a part of the image data corresponding to each light source group, and controls light emission of each light source part, based upon second light emission intensity of each light source part obtained through filter processing for smoothing a distribution of first light emission intensity of the light emitting means. The control means makes settings so that filter intensity of smoothing by the filter processing on a light source part of a light emission color larger in value of the first feature quantity at a part of corresponding image data among the plurality of light source parts of an object light source group is higher than filter intensity of smoothing by the filter processing on light source parts of other light emission colors.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image display apparatus and an image display method.

  As a technique related to a liquid crystal display device, a technique is known which enhances the contrast by adjusting the light emission intensity for each light source (light source group) (local dimming). Further, the contrast of the display image can be further improved by correcting the image data in accordance with the light emission intensity of the light source.

  In addition, technology that controls the luminous intensity of the light source color by color using three elements of an R element that emits red light, a G element that emits green light, and a B element that emits blue light as light emitting elements of a light source It is known (patent document 1). Thereby, the color gamut of the display image can be expanded. Furthermore, in the case of individually controlling the light emission intensity of the light source, it is generally performed to filter the light emission intensity of the light source in order to prevent visual recognition of the luminance boundary between the light sources. For example, the luminance boundary is made less visible by applying a low pass filter to the emission intensity of the adjacent light source (Patent Document 2).

JP 2007-322944 A JP, 2009-282451, A

  However, in the prior art disclosed in the above-mentioned patent documents, there is a problem that the color gamut expansion effect of the light source is reduced by the filter processing. Therefore, an object of the present invention is to provide a technique for suppressing the reduction of the color gamut expansion effect by the filter processing.

The first aspect of the present invention is
A light emitting unit having a plurality of light source groups each including a plurality of light source units having different luminescent colors;
Display means for displaying an image by modulating light emitted by the light emitting means according to image data;
The first light emission intensity of each light source unit is set for each color based on the first feature amount related to the brightness of the color of the part of the image data corresponding to each light source group, and the first light emission unit Control means for controlling light emission of each light source unit based on the second light emission intensity of each light source unit obtained by filter processing for smoothing the distribution of light emission intensity;
Have
The control means performs smoothing filter intensity for the light source unit of the light emission color with a large value of the first feature amount in the corresponding image data portion among the plurality of light source units of the target light source group, Make it higher than the filter strength of smoothing by the filter processing for light source parts of other luminescent colors,
An image display apparatus characterized by

The second aspect of the present invention is
It is an image display method of an image display apparatus provided with the light emission means which has multiple light source groups which consist of several light source parts from which luminescent color mutually differs, Comprising:
The first light emission intensity of each light source unit is set for each color based on the first feature amount related to the brightness of the color of the part of the image data corresponding to each light source group, and the first light emission unit A control step of controlling light emission of each light source unit based on the second light emission intensity of each light source unit obtained by filter processing for smoothing the distribution of light emission intensity;
A display step of displaying an image by modulating light emitted by the light emitting means according to image data;
Have
In the control step, of the plurality of light source units of the target light source group, the filter intensity of the smoothing by the filter processing with respect to the light source unit of the luminescent color having a large value of the first feature amount in the corresponding image data portion, Make it higher than the filter strength of smoothing by the filter processing for light source parts of other luminescent colors,
It is an image display method characterized by the above.

  A third aspect of the present invention is a program for causing a computer to execute the steps of the above method.

  According to the present invention, it is possible to suppress the reduction of the color gamut expansion effect by the filter processing.

Functional block diagram showing an example of the image display device according to the first embodiment The figure which shows an example of the backlight unit which concerns on Embodiment 1. A figure showing an example of a liquid crystal panel concerning Embodiment 1. FIG. 6 shows an example of the spectral transmission characteristic of the color filter according to the first embodiment. Functional block diagram showing an example of the filter processing unit according to the first embodiment A diagram showing an example of the arrangement of the backlight unit according to the first embodiment Flow chart showing a flow of filter processing according to the first embodiment Figure showing an example of the characteristic of light intensity distribution of backlight A diagram showing an example of a diffusion plate when a plurality of backlights are lit A diagram showing an example of a diffusion plate when a plurality of backlights are lit Diagram showing light intensity distribution when multiple backlights are lit Functional block diagram showing an example of the pixel value correction unit according to the first embodiment Functional block diagram showing an example of an image display device according to the second embodiment Functional block diagram showing an example of a filter processing unit according to the second embodiment Flow chart showing a flow of filter processing according to the second embodiment Functional block diagram showing an example of an image display device according to the third embodiment Functional block diagram showing an example of a filter processing unit according to the third embodiment Flow chart showing the flow of filter processing according to the third embodiment Diagram showing an example of filter processing

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described.
The image display apparatus according to the present embodiment performs image display by using light-emitting diodes (light-emitting diodes) of a plurality of colors as a light source (light source unit) and modulating light emitted from the light source with a liquid crystal panel according to image data. It is an apparatus. In addition, the image display apparatus which concerns on this embodiment can also use display elements (MEMS shutter etc.) other than a liquid crystal display element.

<Overall configuration>
FIG. 1 is a functional block diagram showing an example of an image display apparatus according to the present embodiment. The image display apparatus according to the present embodiment includes a backlight control function unit 10, an image data correction function unit 11, a display unit 12, and the like. The backlight control function unit 10 includes a feature amount acquisition unit 101, a provisional strength calculation unit 102, a filter processing unit 103, a backlight drive unit 104, and the like. Further, the image data correction function unit 11 includes a light emission intensity estimation unit 105, a chromaticity calculation unit 106, a pixel value correction unit 107, and the like. Furthermore, the display unit 12 is configured of a backlight unit 108, a liquid crystal panel 109, and the like.

  The backlight control function unit 10 is a function unit that controls the light emission intensity (light emission luminance) of each light source. The image data correction function unit 11 is a function unit that corrects image data based on the light emission intensity controlled by the backlight control function unit 10. The display unit 12 is a functional unit (display device) that lights a light source or displays an image based on input image data. The respective functional units will be described in detail below.

<Display 12>
The display unit 12 is a functional unit (display device) that lights a light source or displays an image based on input image data. The display unit 12 includes a backlight unit 108 in which a plurality of light sources (groups) are disposed, a liquid crystal panel 109 formed of liquid crystal elements, and the like.

FIG. 2 shows a backlight unit 108 according to the present embodiment.
The backlight unit 108 is a member that emits light to the back surface of the liquid crystal panel 109. The backlight unit 108 has a backlight area 80 of width p × length q corresponding to the light source. In the backlight area 80, a plurality of light source groups 800 are arranged at appropriate intervals. The light source group 800 includes a plurality of light sources having different emission colors. In the backlight unit 108 shown in FIG. 2, each light source group 800 includes an R light source 801 that emits red light, a G light source 802 that emits green light, and a B light source 803 that emits blue light. The backlight unit 108 has a plurality of light source groups, and light emitted from the light source groups is diffused in the surface direction by a diffusion plate (not shown) and illuminates the liquid crystal panel 109 from behind as a backlight having a predetermined spread. .

  In the following description, the j-th horizontal and k-th vertical areas of the backlight area 80 will be described as backlight areas (j, k). In the present embodiment, an example in which LEDs of three colors are used as light emitting elements of the light source will be described, but the light source (light emitting element) is not limited to LEDs. For example, a laser element, an organic EL element, a cold cathode tube element, a plasma element or the like may be used as the light emitting element. The color of light emitted from the light source is not limited to three colors of red, green and blue. For example, the light emitted from the light source may be ultraviolet light or the like. Furthermore, the number of light sources included in one light source group is not limited to three, and any number of light sources may be included. In addition, one light source group may have light emitting elements of one or two colors, or may have light emitting elements of four or more colors. In addition, in the display unit 12, a plurality of backlight panels may be provided.

FIG. 3 is a view showing a liquid crystal panel 109 according to the present embodiment.
In the liquid crystal panel 109, liquid crystal shutter elements 901 and color filters 902 are arranged in a matrix. The liquid crystal shutter element 901 forms an image on the panel by changing the transmittance of the corresponding element according to the RGB value of each pixel of the image data. In the liquid crystal shutter element 901, pixels of width m × length n are arranged. Each pixel is provided with R ^′ , G ^′ , and B ^′ as sub-pixels (sub-pixels). The color filter 902 is a member that separates the light emitted from the backlight unit 108 into light of wavelengths corresponding to R, G, and B, respectively. FIG. 4 shows an example of the transmission characteristic of the color filter used in the present embodiment. FilterR, G and B respectively show the spectral transmission characteristics of the filters transmitting the light of red, green and blue components.

<Backlight Control Function Unit 10>
The backlight control function unit 10 is a function unit that controls the light emission intensity (light emission luminance) of the light source. The backlight control function unit 10 performs filter processing for smoothing the temporary luminance determined for each color based on the image data, and the light source emits light with the emission intensity after the filter processing. The control of the light emission intensity is performed by the feature amount acquisition unit 101, the temporary intensity calculation unit 102, the filter processing unit 103 and the like, and the control of the light emission intensity of the light source is performed by the backlight drive unit 104 and the like.

The feature amount acquisition unit 101 is a functional unit that acquires a feature amount (STAT) based on input image data (ID). In the present embodiment, the feature amount acquisition unit 101 acquires a feature amount (first feature amount) based on image data associated with each light source group 800 (target light source group). Specifically, from the image data associated with the backlight area 80, the feature quantity acquisition unit 101 calculates the maximum value ( _Rmax , _Gmax , _Bmax ) of the pixel values of each of R, G, and B as a feature quantity. Get as. The image data associated with the backlight area 80 is image data related to an image displayed on the area of the liquid crystal panel 109 to which light is emitted from the light source group of the backlight area 80.

  In addition, the acquisition method of a feature-value is not specifically limited. For example, as the feature amount, an upper predetermined number of average values of pixel values of image data associated with each light source may be used. Further, the target for acquiring the feature amount is not limited to only the image data associated with the light source group 800. For example, the feature amount acquisition unit 101 includes at least one or both of the image data associated with the light source group 800 and the image data associated with the light source group located around the light source group 800. The feature amount can be acquired from the pixel value of. Furthermore, the feature amount acquisition unit 101 may smooth the image data with a spatial smoothing filter as pre-processing for acquiring the feature amount so that noise or small bright spots in the image data are not detected as the maximum value.

ここで、Ｐ_０＿Ｒ，Ｐ_０＿Ｇ，Ｐ_０＿Ｂは、それぞれＲ，Ｇ，Ｂ光源の暫定強度Ｐ_０として算出される値である。また、Ｖ_ｍａｘは、各光源に対応する画素データがとりうる値の最大値である。例えば、画像信号のビット数が８ビットである場合、Ｖ_ｍａｘは２５５である。 The provisional intensity calculation unit 102 is a functional unit that calculates the provisional intensity P ₀ (first light emission intensity) of the light source based on the feature quantity acquired by the feature quantity acquisition unit 101. The temporary intensity calculation unit 102 calculates the temporary intensity P ₀ for each light source by dividing the feature amount for each light source by the maximum value that the pixel value can take, using the following equation (1).

_{Here, P 0_R, P 0_G, P} 0_B is a value calculated respectively R, G, as a provisional intensity _{P 0} of the B light source. Further, V _max is the maximum value of values that pixel data corresponding to each light source can take. For example, when the number of bits of an image signal is eight, V _max is 255.

The filter processing unit 103 calculates the light emission intensity P _f (second light emission intensity) by performing filter processing for each color on the temporary intensity P ₀ calculated by the temporary intensity calculation unit 102, and performs backlight drive described later. It is a functional unit that outputs data to the unit 104. FIG. 5 shows a functional block diagram of the filter processing unit 103. As shown in FIG. The filter processing unit 103 includes a filter coefficient determination unit 1031, a first filter processing unit 1032, a second filter processing unit 1033, and the like. Hereinafter, each functional unit will be described with respect to an example in which the filter processing of the filter size 3 is performed in the space direction according to the present embodiment. The details of the processing content of the filter processing unit 103 will be described later using the flowchart of FIG. 7.

The filter coefficient determination unit 1031 is a functional unit that determines filter coefficients f ₁ , f ₂ , and f ₃ indicating the filter strength of each of RGB for each luminescent color from the region of interest and the peripheral region. Here, the attention area is the backlight area 80 of interest, and the example of FIG. 6 shows the backlight area (j, k). Further, the peripheral area is an area located in the upper, lower, left, right and diagonal directions of the backlight area (j, k) which is the area of interest, and in the example of filter size 3 in FIG. It is eight areas located in the periphery.

The first filter processing unit 1032 is a functional unit that performs filter processing in the vertical direction based on the filter coefficient calculated by the filter coefficient determination unit 1031. The second filter processing unit 1033 is a functional unit that performs filter processing in the horizontal direction based on the filter coefficient calculated by the filter coefficient determination unit 1031. Although an example of applying a weighted averaging filter has been described in the present embodiment, the type of filter is not limited, and an arbitrary smoothing filter (low pass filter) can be applied. Also, the filter size is not particularly limited, and may be larger than three. Furthermore, the number of filter coefficients and the number of peripheral regions increase or decrease according to the filter size. For example, in the case of the filter size 5, the filter coefficients are f ₁ to f ₅ and the peripheral region is 24.

The backlight drive unit 104 drives the light source of the backlight unit 108 based on the light emission intensity P _f calculated by the filter processing unit 103. Specifically, the backlight driving unit 104 drives the R light source 801, the G light source 802, and the B light source 803 shown in FIG. Here, the signal controlled by the backlight driver 104 represents, for example, the pulse width of a pulse signal (a pulse signal of current or voltage) applied to the light source. In that case, the light emission intensity of the light source is adjusted (PWM control) by the backlight drive unit 104 adjusting the control signal. The control signal may be a signal representing the peak value of the pulse signal applied to the light source (PAM control), or may be a signal representing both the pulse width and the peak value (PWAM control).

<Image data correction function unit 11>
The image data correction function unit 11 is a function unit that corrects a pixel value of image data according to the present embodiment. The correction of the pixel value of the image data is performed by the light emission intensity estimation unit 105, the chromaticity calculation unit 106, the pixel value correction unit 107, and the like. The image data correction function unit 11 corrects the image data so that the desired image is displayed according to the light emission intensity of the backlight determined by the backlight control function unit 10, so that the image is corrected based on the chromaticity of the backlight. Correct the luminance or chromaticity indicated by the pixel value of the data.

The light emission intensity estimation unit 105 is a functional unit that estimates the light intensity distribution P _d on the liquid crystal panel 109 when each light source is driven with the light emission intensity P _f calculated by the filter processing unit 103. Here, the light emitted from the light source group 800 is diffused by a diffusion plate (not shown) provided between the backlight and the liquid crystal panel 109, and is irradiated to the back side of the liquid crystal panel 109. The light intensity distribution indicating the extent of the light irradiated to the liquid crystal panel 109 is determined by the light emission characteristics of the light source group 800, the characteristics of the diffusion plate, the distance between the light source group 800 and the diffusion plate, and the like. When light is emitted from a light source group 800 of a certain backlight area 80, it is desirable that the light intensity distribution be uniform within the region (portion of image data) of the liquid crystal panel 109 corresponding to the backlight area 80. In addition, it is desirable that the light intensity distribution be a distribution having a small amount of leaked light to the area of the liquid crystal panel 109 corresponding to the peripheral backlight area 80.

FIG. 8 is a schematic view showing a light intensity distribution formed on the liquid crystal panel 109 when a certain light source group 800 is lighted alone. The horizontal axis indicates the distance from the light source group 800 (light emitting point), and the vertical axis indicates the light intensity of the irradiation light in the liquid crystal panel 109. pf (x−x ₀ ) represents a light emission intensity distribution (characteristic function) of light. This characteristic function has a maximum value of 1, and is a distribution function that relatively indicates the degree to which the light intensity of the irradiation light decreases due to the change in distance from the light source group 800. The light intensity decreases in accordance with the distance from the center (light emitting point: x ₀ ) of the light source group 800. The intensity distribution of light irradiated to the liquid crystal panel 109 is determined by a value obtained by multiplying the light emission luminance of the light source group 800 by the above-described characteristic function.

  FIG. 9 is a schematic view showing a light intensity distribution irradiated on the liquid crystal panel 109 in the above-mentioned case. FIG. 9 shows the light intensity distribution when the liquid crystal panel 109 is viewed from the front side. As indicated by the characteristic function described above, on the liquid crystal panel 109, the intensity of the emitted light decreases radially in accordance with the distance from the light emission point. This characteristic function can be obtained in advance by measurement using the backlight unit 108. The characteristic function may be theoretically obtained by calculation.

FIG. 10 illustrates the case where the peripheral light source is on. Figure 10 shows an example of a diffusion plate when the light source is located in x _a point and x _b point is emitting light. FIG. 11 is a view showing a light intensity distribution corresponding to the point between the point α and the point β on the diffusion plate in FIG. pf _a (x-x _a ) and pf _b (x-x _b ) are emission intensity distributions of the light sources a and b, respectively. x _a and x _b indicate light emission points of the light sources a and b, and P _a and P _b indicate light emission intensities of the light sources a and b, respectively. The light intensity P _d (Y) at the Y point located between the α point and the β point can be estimated to be the superposition of the light intensities contributed by the light sources a and b respectively, and is expressed by the following equation (2) Ru.

ここで、Ｐ_ｄ＿Ｒ（ｘ，ｙ）は、画素座標（ｘ，ｙ）におけるＲ光源に関する光強度を示し、Ｐ_ｊｋ＿Ｒは、バックライトエリア（ｊ，ｋ）に位置するＲ光源の発光強度（Ｐ_ｆ）を示す（ＧおよびＢ光源も同様）。 In practice, the light intensity distribution formed in the backlight unit 108 is a superposition of the light emission intensity distributions of the plurality of light sources. Below, the example which applied the above-mentioned example on the liquid crystal panel concerning this embodiment is demonstrated. Hereinafter, the pixel coordinates of the liquid crystal panel 109 of the light source group 800 corresponding to the light source located in the backlight area (j, k) disposed on the backlight unit 108 are (x _jk , y _jk ) Do. Also, let the light emission intensity distribution of each light source be pf (x, y). Using these, the light intensity P _d (x, y) at the pixel coordinates (x, y) on the liquid crystal panel 109 can be obtained using the following equation (3).

Here, P _{d —} R (x, y) represents the light intensity of the R light source at pixel coordinates (x, y), and P _{jk —} R represents the light emission intensity (P of the R light source located in the backlight area (j, k) _f ) is shown (the same applies to the G and B light sources).

  The chromaticity calculation unit 106 calculates the chromaticity C for each pixel on the liquid crystal panel 109 based on the light intensity distribution calculated by the light emission intensity estimation unit 105. First, chromaticity coordinates X, Y, Z when the light emission intensity of the light source is 1.0 are obtained in advance. The light emission intensity can be measured in advance using the backlight unit 108 or can be calculated from the wavelength light emission characteristics obtained from the data sheet of the part. Hereinafter, the present invention will be described in detail using X, Y, and Z which are chromaticity coordinates when the light emission intensity is 1.0.

以上の式（４）を用いて、Ｒ，Ｇ，Ｂそれぞれについて算出することで、画素座標（ｘ，ｙ）におけるＲ，Ｇ，Ｂ画素毎の色度を求めることができる。 The chromaticity at the pixel coordinates (x, y) on the liquid crystal panel 109 can be obtained by superimposing chromaticity values according to the backlight intensity at each pixel position. An example of the chromaticity of the R light source is shown in equation (4).

By calculating for each of R, G, and B using the above equation (4), the chromaticity for each of R, G, and B pixels at pixel coordinates (x, y) can be determined.

The pixel value correction unit 107 is a functional unit that corrects the pixel value of the image data associated with the light source. The pixel value correction unit 107 determines the luminance or chromaticity indicated by the pixel value (R, G or B) of the image data in the color space defined in the input image data, under the chromaticity corresponding to each pixel. The reproduced pixel value (D _T ) after correction is calculated. FIG. 12 shows a functional block diagram of the pixel value correction unit 107 according to the present embodiment. Pixel value correction unit 107, XYZ conversion unit 1071, and a transformation matrix generating unit 1072, R ^'G' B ^'conversion unit 1073 and the like. Hereinafter, an example in the case where an RGB signal is input as image data will be described.

The XYZ conversion unit 1071 is a functional unit that converts RGB values of each pixel of the input video data into pixel values of the XYZ color system. When the assumed color gamut of the image data is sRGB, the conversion procedure is as follows according to the definition of the CIE 1931 color system. First, the XYZ conversion unit 1071 performs inverse γ conversion on the values of R, G, and B of the image data, and calculates LR, LG, and LB, which are values after conversion. Next, the XYZ conversion unit 1071 performs conversion from sRGB to XYZ according to the following equation (5) using the conversion matrix M.

Converting matrix generating unit 1072, an inverse transformation matrix _M ^{C -1} to convert R ^'G' B ^'values to generate the definition of CIE1931 colorimetric system from the XYZ color system based on the backlight chromaticity C for each pixel It is a functional unit. This inverse transformation matrix M _C ⁻¹ is the inverse of the matrix of XYZ values of red, green and blue light sources.

以上により求められる補正後の画像データが液晶パネル１０９へ出力される。液晶パネル１０９が、補正後の画像データに応じて各画素に対応する液晶素子の透過率を制御することにより、液晶パネル１０９に照射する光の輝度に分布がある場合でも、入力画像データに対応する表示輝度で画像を表示することが可能となる。 R ^'G' B ^'conversion unit 1073 is a functional unit that calculates the corrected pixel value from the input XYZ values and inverse transformation matrix _M ^{C -1.} R ^'G' B ^'values of the corrected pixel value _{(D T)} is determined using the following equation (6).

The corrected image data obtained as described above is output to the liquid crystal panel 109. By controlling the transmittance of the liquid crystal element corresponding to each pixel according to the image data after correction, the liquid crystal panel 109 corresponds to the input image data even when the luminance of the light irradiated to the liquid crystal panel 109 has a distribution. It is possible to display an image with the display brightness.

<Content of filter processing>
The processing content of the filter processing unit 103 according to the present embodiment will be described using the flowchart shown in FIG.

<< step S101 >>
In step S101, the filter coefficient determination unit 1031 determines the color priority (preferential color) based on the feature quantities (R _max, G _max and B _{max in the} above example) of the attention area and the peripheral area. Specifically, the filter coefficient determination unit 1031 determines the priority by comparing maximum values such as R _max in the attention area and the peripheral area using R _{max and the} like defined for each area. In the present embodiment, the filter coefficient determination unit 1031 determines the color priority in the descending order of the maximum value such as R _max . That is, the filter coefficient determination unit 1031 determines that the color having the largest value among the maximum values (R _max, G _max and B _max ) of each color in the attention area and the peripheral area has the highest priority. . Also, the filter coefficient determination unit 1031 determines the priority such that the color with the next largest maximum value is the next priority, and the color with the smallest maximum value is the lowest priority. In addition, the determination method of the priority of color is not specifically limited. For example, the feature amount may be in ascending order, or the priority may be obtained from the statistic of the image data without using the feature amount. Also, the color priority may be determined using only the feature amount of the region of interest. The color priority is determined for each area (area of interest).

«Step S102»
In step S102, the filter coefficient determination unit 1031 calculates the level difference (second feature amount) of the second and third priority colors of the attention area and the peripheral area. Assuming that the signal level of the second priority color in the region of interest is L _M2 and the maximum value of the signal levels of the second priority color in the peripheral region is L _S2 , the level difference ΔL ₂ of the second priority color is Calculated using 7).

なお、領域毎のレベル差は、光源に対応する領域（注目領域または周辺領域）の画素値の最大値の差に限定されず、最小値、平均値、中間値等の差でもよい。 Similarly, for the third priority color, assuming that the signal level of the third priority color in the attention area is L _M3 and the maximum value of the signal levels of the third priority color in the peripheral area is L _S3 , the third priority color The level difference ΔL _{3 of} is calculated using the following equation (8).

The level difference for each area is not limited to the difference between the maximum values of the pixel values of the area corresponding to the light source (the area of interest or the surrounding area), and may be a difference such as the minimum value, the average value, or the intermediate value.

«Step S103»
In step S103, the filter coefficient determination unit 1031 determines filter coefficients based on the level difference. The filter coefficient determination unit 1031 determines filter coefficients for each color. The filter coefficients f ₁ , f ₂ and f ₃ correspond to the filter coefficients of the first to third preferred colors. The initial values (predetermined filter coefficients) of these filter coefficients are common filter coefficients, and are read out in advance from a storage device such as a ROM. In addition, a predetermined value is used as the filter coefficient or the size. For example, if the size is 3, the filter coefficients consist of three elements, and filter coefficients such as (1/4, 2/4, 1/4) are determined. At this time, the value of the filter coefficient takes a value in the range of 0 to 1, and an example in which the total value of all the values is 1 will be described.

  Here, the filter strength in each filter coefficient indicates the degree of averaging in the filter process using the filter coefficient. That is, high filter strength means that the weight of the filter coefficient is set to be close to uniform, for example, a value such as (1/3, 1/3, 1/3) is set as the filter coefficient. . The low filter strength means that the weight of the value position close to the center of the filter coefficient is set to a large value. For example, the filter coefficient has a value such as (1/16, 14/16, 1/16) Is set. Therefore, by performing the setting as described above, the influence of the second or third priority color on the peripheral region of the second or third priority color is suppressed.

The filter coefficient determination unit 1031 sets the filter coefficient f1 of the _first priority color as a predetermined filter coefficient of a predetermined filter strength. Also, the filter coefficient determining unit 1031 determines the filter coefficient f ₂ of the second priority color based on the level difference [Delta] L ₂ of predetermined filter coefficients and second priority color. Specifically, the filter coefficient determining unit 1031, as the level difference value of [Delta] L ₂ of the second priority color is large, it determines the filter coefficient f ₂ such that the filter strength is lower than the predetermined filter coefficients. Similarly, the filter coefficient determining unit 1031, as the value of the third priority color level difference [Delta] L ₃ is large, so that the filter strength is lower than the predetermined filter coefficients, determines the filter coefficient f _3.

  The filter coefficient determination unit 1031 may select and read the filter coefficients of the respective colors from a plurality of filter coefficients stored in a memory (not shown) or the like based on the above-described determination method. Also, the filter coefficient determination unit 1031 may calculate and determine the filter coefficients of the respective colors based on the predetermined filter coefficients and the level difference.

  The filter processing unit 103 may determine the filter coefficient of each color so that the filter coefficient of the third priority color is lower than the filter coefficient of the second priority color. For example, the filter processing unit 103 may control the filter strength to be further lower for the second priority color than the third priority color, and the filters for the second priority color and the third priority color may be controlled. The intensity may be set to be the same.

ここで、フィルタのサイズに応じて上記式（９）のＡの範囲は適宜変更される。また、発光強度Ｐ_ｖは、第１から第３の優先色それぞれについて算出される。 «Step S104»
In step S104, vertical and horizontal filtering processes are performed.
First, the first filter processing unit 1032 performs filter processing in the vertical direction according to the filter coefficient calculated by the filter coefficient determination unit 1031. When the filter coefficient size is 3 with respect to the temporary intensity P ₀ calculated by the temporary intensity calculation unit 102, the first filter processing unit 1032 obtains the light emission intensity P _v using the following equation (9) Can.

Here, the range of A in the above equation (9) is appropriately changed according to the size of the filter. In addition, the light emission intensity P _v is calculated for each of the first to third preferred colors.

ここで、上記と同様にフィルタのサイズに応じて上記式（１０）のＡの範囲は適宜変更される。また、発光強度Ｐ_ｆは、第１から第３の優先色それぞれについて算出され、光源Ｒ，Ｇ，Ｂそれぞれの発光強度として割り当てられる。また、これらの発光強度Ｐ_ｆは、発光強度推定部１０５およびバックライト駆動部１０４へ出力される。 Next, the second filter processing unit 1033 performs filter processing in the horizontal direction. Relative emission intensity P _v calculated by the first filter processing section 1032, it is possible to obtain the luminous intensity P _f using the following equation (10).

Here, the range of A in the above equation (10) is appropriately changed according to the size of the filter as described above. Further, the light emission intensity P _f is calculated for each of the first to third preferred colors, and is assigned as the light emission intensity of each of the light sources R, G, and B. Further, these light emission intensities P _f are output to the light emission intensity estimation unit 105 and the backlight drive unit 104.

In the above example, the filter processing is divided into vertical and horizontal directions. However, even if filter coefficients are defined in two dimensions, the filter processing may be performed using the following equation (12). Good.

  The filtering process is performed by the process described above. Below, the specific example of the filter processing which concerns on this embodiment is shown. For the sake of simplicity, only the filtering process in the horizontal direction will be described.

  FIG. 19A shows an example in which image data having a strong red component is input. Further, the bar graph in FIG. 19A shows an example of the feature amount (the maximum value of each of R, G, and B) in each area of the attention area or the surrounding area. In this case, since the maximum value for each color is in the order of R (255), B (245), and G (240) from the feature amounts in the region of interest and the peripheral region, the first priority color (first priority color) It is determined that the color of degree is R (red), the second preferred color is B (blue), and the third preferred color is G (green). FIG. 19B shows the emission intensity of each light source when the filter coefficients are uniformly provided regardless of the color. FIG. 19C shows the emission intensity of each light source when the filter coefficient is determined for each color. Specifically, for the second and third preferred colors B and G, the filter coefficients are determined such that the filter strength is low. As described above, the light emission intensity of unnecessary color components (green and blue) is reduced with respect to the image data of the target area where the red component is strong, and the purity of the red component is increased. Reduction is suppressed.

<Effect of this embodiment>
As described above, by determining the filter strength at the time of performing the filter process based on the level difference for each color of the attention area and the peripheral area, the reduction of the color gamut expansion effect at the time of the filter process is suppressed It is possible.

(Modification of Embodiment 1)
In the above-described embodiment, an example in which the filter strength is determined based on the level difference between the attention area and the peripheral area has been described. However, the filter coefficient determination unit 1031 determines the filter strength based on the color priority. It is also good. Specifically, the filter coefficient determination unit 1031 increases the filter strength as the priority is higher for each color, and lowers the filter strength as the priority is lower. By doing this, it is possible to suppress the influence of the peripheral region on the low priority (weak color component) color, and therefore, it is possible to suppress the reduction of the color gamut expansion effect at the time of filter processing. Also, the filter coefficient determination unit 1031 may determine the filter strength in accordance with both the level difference and the priority described above. The filter coefficient determination unit 1031 may determine the filter strength to be lower as the level difference is larger, and to be higher as the level difference is smaller, using only the level difference obtained for each color.

Second Embodiment
In this embodiment, an example will be described in which the filter coefficient in each color is determined in consideration of the “motion amount” (second feature amount) which is the temporal change amount of the image data in addition to the level difference. Hereinafter, configurations and processes different from the first embodiment will be described in detail, and the same configurations and processes as the first embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

FIG. 13 shows a functional block diagram of the image display device according to the present embodiment. The image display apparatus according to the present embodiment includes a motion information acquisition unit 210 in addition to the configuration of the first embodiment. In the present embodiment, the motion information acquisition unit 210 acquires motion information M _i (x, y) for each pixel of image data. Then, the motion information acquisition unit 210 acquires motion information M _blk (j, k) for each area from the motion information M _i (x, y) of the image data corresponding to each area. The filter processing unit 203 obtains the motion amount M _v (j, k) in the attention area from the total value of the motion information M _blk (j, k) in the attention area and the peripheral area. Then, the filter processing unit 203 determines the filter strength based on the motion amount M _v.

ここで、ｆ_０は、現フレームの画素値を表し、ｆ_−１は１フレーム前の画素値を示す。本実施形態では、フレーム差分として、Ｒ，Ｇ，Ｂそれぞれ対する差分のうち最大値をΔｆ（ｘ，ｙ）とする。なお、フレーム差分の算出方法は特に限定されず、Ｒ，Ｇ，Ｂそれぞれ対する差分の平均値等でもよい。 The motion information acquisition unit 210 (second acquisition unit) performs motion information M _i (x, y) for each pixel of the image data and motion information M _blk (j, k) for each area with respect to the input image data. Is a functional unit that acquires The motion information M _i (x, y) according to the present embodiment is obtained based on the frame difference in each pixel. The motion information acquisition unit 210 acquires motion information for each area corresponding to the light source arranged in horizontal p × vertical q, which is a division unit of the backlight unit 108 shown in FIG. 2. First, the motion information acquisition unit 210 calculates a frame difference Δf (x, y) between the image data of the current frame and the image data of the previous frame with respect to the input image data using the following equation (11). Is acquired for each pixel.

Here, f ₀ represents a pixel value of the current frame, and f ₋₁ represents a pixel value of one frame before. In this embodiment, as the frame difference, the maximum value among differences for each of R, G, and B is taken as Δf (x, y). The method of calculating the frame difference is not particularly limited, and an average value of differences with respect to each of R, G, and B may be used.

動き情報取得部２１０は、フレーム間の画素値の差分Δｆ（ｘ，ｙ）が所定の閾値ｓ_１以上である（差分が大きい）場合は「動きあり（Ｍ_ｉ（ｘ，ｙ）＝１）」と判定する。また、動き情報取得部２１０は、フレーム間の画素値の差分が所定の閾値ｓ_１未満である（差分が小さい）場合は「動きなし（Ｍ_ｉ（ｘ，ｙ）＝０）」と判定する。ここで、所定の閾値ｓ_１は、動きの感度を設定するパラメータである。値を小さく設定すると「動きあり」と判定されやすく、値を大きくすると「動きなし」と判定されやすくなる。 Next, the motion information acquisition unit 210 compares the frame difference Δf (x, y) with a predetermined threshold value s ₁ to obtain motion information M _i (x, y) for each pixel according to the following equation (14) Acquire using.

If the difference Δf (x, y) of pixel values between frames is equal to or larger than a predetermined threshold value s ₁ (the difference is large), the motion information acquisition unit 210 “moves (M _i (x, y) = 1) It is determined that In addition, the motion information acquisition unit 210 determines that “no motion (M _i (x, y) = 0)” when the difference in pixel value between frames is less than a predetermined threshold value s ₁ (the difference is small). . Here, the predetermined threshold value s ₁ is a parameter for setting the motion sensitivity. When the value is set small, it is easy to be judged as "moving", and when the value is made large, it is easy to be judged as "moving".

動き情報取得部２１０は、領域内の各画素のうち「動きあり」と判定された画素数が所定の閾値ｓ_２以上である場合は、「動きあり（Ｍ_ｂｌｋ（ｊ，ｋ）＝１）」と判定する。また、動き情報取得部２１０は、「動きあり」と判定された画素数が所定の閾値ｓ_２未満である場合は、「動きなし（Ｍ_ｂｌｋ（ｊ，ｋ）＝０）」と判定する。ここで、所定の閾値ｓ_２は、上述と同様、動きの感度を設定するパラメータである。なお、上述の閾値ｓ_１と同じ値を用いてもよく、異なっていてもよい。 Next, the motion information acquisition unit 210 acquires motion information M _blk (j, k) for each area corresponding to each light source. In the present embodiment, the motion information acquisition unit 210 acquires motion information M _blk (j, k) using the following equation (15) based on the number of pixels determined to be “with motion” for each region.

If the number of pixels determined to be “moving” among the pixels in the region is equal to or _larger than a predetermined threshold s _{2, the} motion information acquisition unit 210 “moves (M _blk (j, k) = 1) It is determined that In addition, when the number of pixels determined to be “moving” is less than the predetermined threshold value s ₂ , the motion information acquisition unit 210 determines that “no motion (M _blk (j, k) = 0)”. Here, the predetermined threshold value s ₂ is a parameter for setting the motion sensitivity as described above. Note that the same value as the above-described threshold value s ₁ may be used or may be different.

  In the present embodiment, the motion is determined using the frame difference, but the determination method is not particularly limited. For example, the presence or absence of motion may be determined by detecting motion vectors between different frames.

The filter processing unit 203 performs filter processing on the temporary intensity P ₀ for each region determined by the temporary intensity calculation unit 102 based on the feature amount of the input image data and the motion information M _blk (j, k). Do.

Details of a method of calculating the light emission intensity P _f in the filter processing unit 203 will be described. The filter processing unit 203 performs filter processing on the temporary intensity P ₀ determined by the temporary intensity calculation unit 102. Hereinafter, the filter processing method in the present embodiment will be described. FIG. 14 shows a functional block diagram of the filter processing unit 203.

具体的には、フィルタ係数決定部２０３１は、注目領域および周辺領域のうち「動きあり（Ｍ_ｂｌｋ（ｊ，ｋ）＝１」」と判定される領域数を求める。例えば、フィルタサイズ３の場合、動き量Ｍ_ｖ（ｊ，ｋ）は０から９の値をとりうる。 The filter coefficient determination unit 2031 is a functional unit that determines, from the region of interest and the peripheral region, the filter coefficients indicating the filter strength of each of RGB. The definitions of the region of interest and the peripheral region are the same as in the first embodiment. The filter coefficient determination unit 2031 determines a filter coefficient based on the feature amount acquired by the feature amount acquisition unit 101 and the motion information M _blk (j, k) acquired by the motion information acquisition unit 210. Here, the filter coefficient determination unit 2031 obtains the motion amount M _v (j, k) from the following equation (16) based on the motion information motion information M _blk of the attention area and the peripheral area.

Specifically, the filter coefficient determination unit 2031 obtains the number of regions determined as “motion (M _blk (j, k) = 1)” in the region of interest and the peripheral region. The motion amount M _v (j, k) can take values of 0 to 9.

<Content of filter processing>
The method of calculating the filter coefficient according to the present embodiment will be described with reference to the flowchart shown in FIG. First, the filter coefficient determination unit 2031 determines the priority of color as in the above-described embodiment (S101). Then, the filter coefficient determination unit 2031 calculates the second and third priority color level differences between the attention area and the surrounding area (S102).

Next, in the present embodiment, the filter coefficient determination unit 2031 calculates the motion amount M _v from the motion information M _blk of the attention area and the surrounding area using the above equation (16) (S2031). Then, the filter coefficient determining unit 2031, a predetermined filter coefficient, the second determining priority color filter coefficient f ₂ of the basis of the second priority color level differences and the motion amount M _v of (S2032). Specifically, the filter coefficient determination unit 2031 performs a filter such that the filter strength becomes lower with respect to a predetermined filter coefficient as the value of the level difference of the second preferred color is larger and the amount of movement M _v is larger. Determine the coefficients. Here, the reason why the filter strength is reduced as the level difference of the second preferred color is larger is as described in the first embodiment. Further, as the amount of movement M _v is large, why filter strength is set to be low, as the image of the motion amount M _v is large, the difference in color between the peripheral region is due to hard to be visually. Similarly, to determine the predetermined filter coefficients, the third filter coefficient f ₃ of the priority color on the basis of the third priority color level differences and the motion amount M _v of. The filter coefficient f1 of the _first preferred color is a predetermined filter coefficient as in the above-described embodiment. Then, each filter processing unit performs vertical and horizontal filter processing based on the filter coefficient, as in the above-described embodiment (S104).

The light emission intensity P _f calculated by the filter processing unit 203 is output to the light emission intensity estimation unit 105 and the backlight drive unit 104. By performing the above processing, it is possible to further suppress the reduction of the color gamut expansion effect with respect to the area determined to have motion.

(Modification of Embodiment 2)
In the above embodiment, an example of determining the filter strength based on the level difference between the attention area and the surrounding area and the movement amount of the attention area and the surrounding area has been described, but the filter strength is determined based only on the movement amount You may Specifically, the filter coefficient determination unit 2031 obtains the amount of movement for each color, lowers the filter strength as the amount of movement is larger, and increases the filter strength as the amount of movement is smaller. By doing this, the difference in color between the peripheral regions becomes less visible.

(Embodiment 3)
In this embodiment, in addition to the above-described level difference, an example of determining the filter coefficient of each color according to the color difference (second feature amount) of the attention area and the peripheral area will be described. Hereinafter, configurations and processes different from the first embodiment will be described in detail, and the same configurations and processes as the first embodiment will be assigned the same reference numerals and descriptions thereof will be omitted.

  FIG. 16 shows a functional block diagram of the image display device according to the present embodiment. The image display apparatus according to the present embodiment includes a color difference calculation unit 310 in addition to the configuration of the first embodiment. In the present embodiment, the color difference calculation unit 310 calculates, for input image data, the color difference between the attention area and the surrounding area for each area corresponding to each light source. Then, the filter processing unit 303 determines the filter strength based on the color difference.

  The method of calculating the color difference in the color difference calculation unit 310 will be described. The color difference calculation unit 310 calculates the color difference between the attention area and the surrounding area based on the image data associated with the light source group. In the present embodiment, the color difference calculation unit 310 uses the value of ΔE as an index of color difference. Note that ΔE is an index indicating that the color difference is larger as the value is larger.

ΔE can be determined using the difference between the average of the pixel values of the region of interest and the average of the pixel values of the peripheral region. For example, the color difference calculation unit 310 can obtain the Euclidean distance between the average value of the pixel values of the region of interest and the average value of the pixel values of the peripheral region and use it as ΔE. The method of calculating ΔE is not particularly limited. For example, each backlight area 80 of the attention area and the peripheral area
The ΔE may be calculated from the sum or average of the differences for each pixel value.

The filter processing unit 303 performs filter processing on the temporary strength P ₀ determined by the temporary strength calculation unit 102. Hereinafter, the filter processing method in the present embodiment will be described. In the present embodiment, an example in which filter processing is performed in the space direction will be described.

FIG. 17 is a functional block diagram of the filter processing unit 303 according to the present embodiment.
The filter coefficient determination unit 3031 is a functional unit that determines, from the region of interest and the peripheral region, the filter coefficients indicating the filter strength of each of RGB. The definition of the attention area and the peripheral area is the same as that of the above-described embodiment. The filter coefficient determination unit 3031 determines the filter coefficient based on the feature amount acquired by the feature amount acquisition unit 101 and the color difference calculated by the color difference calculation unit 310.

<Content of filter processing>
The method of calculating the filter coefficient will be described using the flowchart shown in FIG. First, the filter coefficient determination unit 3031 determines the priority of color as in the above-described embodiment (S101). Then, the filter coefficient determination unit 3031 calculates the level difference of the second and third priority colors between the attention area and the surrounding area (S102).

Next, in the present embodiment, the filter coefficient determination unit 3031 determines the filter coefficient f1 of the _first priority color based on the predetermined filter coefficient and the color difference (S303). Specifically, the filter coefficient is determined such that the filter strength is lower for a predetermined filter coefficient as the value of the color difference is smaller. This is because when the color difference is small, the difference in color tone is small, so that it is difficult to visually recognize the difference in color tone between the peripheral regions. Then, the filter coefficient determination unit 3031 determines the filter coefficient f2 of the _second priority color based on the predetermined filter coefficient and the level difference and color difference of the second priority color. Specifically, the filter coefficient determination unit 3031 causes the filter strength to be lower for a predetermined filter coefficient as the value of the level difference of the second preferred color is larger and the color difference is smaller. Similarly, the filter coefficient f3 of the _third priority color is determined based on the predetermined filter coefficient and the level difference and color difference of the third priority color. Then, each filter processing unit performs vertical and horizontal filter processing based on the filter coefficient, as in the above-described embodiment (S104).

The light emission intensity P _f calculated by the filter processing unit 303 is output to the light emission intensity estimation unit 105 and the backlight drive unit 104. By performing the above processing, by controlling the filter strength based on the color difference in the peripheral area, it is possible to suppress the reduction of the color gamut expansion effect in consideration of the difference in visual tint. It is.

(Modification of Embodiment 3)
Although the above-mentioned embodiment demonstrated the example which determines a filter strength based on the level difference and color difference of an attention area | region and a surrounding area, you may determine a filter strength based only on a color difference. Specifically, the filter coefficient determination unit 3031 reduces the filter strength as the color difference is smaller, and increases the filter strength as the color difference is larger. By doing this, the difference in color between the peripheral regions becomes less visible. When the color difference is determined for each RGB, the filter coefficient determination unit 3031 may lower the filter strength as the color difference is larger, and may increase the filter strength as the color difference is smaller.

(Others)
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Can also be realized. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

  As mentioned above, although the preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

101: feature amount acquisition unit 102: temporary intensity calculation unit 103: filter processing unit 104: backlight drive unit 105: light intensity estimation unit 106: chromaticity calculation unit 107: pixel value correction unit 108: backlight unit 109: liquid crystal panel

Claims (13)

A light emitting unit having a plurality of light source groups each including a plurality of light source units having different luminescent colors;
Display means for displaying an image by modulating light emitted by the light emitting means according to image data;
The first light emission intensity of each light source unit is set for each color based on the first feature amount related to the brightness of the color of the part of the image data corresponding to each light source group, and the first light emission unit Control means for controlling light emission of each light source unit based on the second light emission intensity of each light source unit obtained by filter processing for smoothing the distribution of light emission intensity;
Have
The control means is configured to control the filter intensity of the smoothing process by the filter process for the light source unit of the light emission color having the large first feature amount in the corresponding image data portion among the plurality of light source units of the target light source group. Make it higher than the filter strength of smoothing by the filter processing for the light source part of the luminescent color,
An image display apparatus characterized by The first feature value is a maximum value of pixel values of at least one of image data portions corresponding to a light source group or a plurality of light source groups located in the periphery of the portion corresponding to the light source group for each color.
The image display apparatus according to claim 1, The control means is based on the maximum value of the first feature amount of the portion of the image data corresponding to the light source group and the first feature amount of the portion of the image data corresponding to the peripheral light source group. The color priority of the plurality of light source units is determined, and the filter strength is increased as the priority is higher, and the filter strength is decreased as the priority is lower.
The image display apparatus according to claim 2, characterized in that: The image processing apparatus further includes second acquisition means for acquiring a second feature amount different from the first feature amount from a portion of image data corresponding to each light source group,
The control means determines the filter strength based on the second feature amount.
The image display apparatus according to claim 2, characterized in that: The second feature amount is a level difference between the first feature amount of the portion of image data corresponding to the light source group and the first feature amount of the portion of image data corresponding to the peripheral light source group. Yes,
The control means lowers the filter strength as the level difference is larger, and increases the filter strength as the level difference is smaller.
The image display apparatus according to claim 4, characterized in that: The second feature amount is a motion amount which is a temporal change amount of a portion of image data corresponding to the light source group and the peripheral light source group,
The control means lowers the filter strength as the movement amount is larger, and increases the filter strength as the movement amount is smaller.
The image display apparatus according to claim 4, characterized in that: The second feature amount is a color difference between a portion of the image data corresponding to the light source group and a portion of the image data corresponding to the peripheral light source group.
The image display apparatus according to claim 4, characterized in that: The control means lowers the filter strength as the color difference is smaller, and increases the filter strength as the color difference is larger.
The image display apparatus according to claim 7, characterized in that: The control unit is configured to calculate the plurality of light source units based on maximum values of the first feature amount corresponding to the light source group and the first feature amount of a portion of image data corresponding to a peripheral light source group. The first priority color is a predetermined filter strength, and the other priority colors are filter strengths based on the second feature amount.
The image display apparatus according to any one of claims 5 to 8, characterized in that: The light source group includes a plurality of light source units that emit red light, green light and blue light.
The image display apparatus according to any one of claims 1 to 9, characterized in that: The filter used for the filter processing is a low pass filter,
The image display device according to any one of claims 1 to 10, characterized in that: It is an image display method of an image display apparatus provided with the light emission means which has multiple light source groups which consist of several light source parts from which luminescent color mutually differs, Comprising:
The first light emission intensity of each light source unit is set for each color based on the first feature amount related to the brightness of the color of the part of the image data corresponding to each light source group, and the first light emission unit A control step of controlling light emission of each light source unit based on the second light emission intensity of each light source unit obtained by filter processing for smoothing the distribution of light emission intensity;
A display step of displaying an image by modulating light emitted by the light emitting means according to image data;
Have
In the control step, of the plurality of light source units of the target light source group, the filter intensity of the smoothing by the filter processing with respect to the light source unit of the luminescent color having a large value of the first feature amount in the corresponding image data portion, Make it higher than the filter strength of smoothing by the filter processing for light source parts of other luminescent colors,
An image display method characterized by   A program for causing a computer to execute the steps of the method according to claim 12.

Images