JP2013068905A - Backlight device and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both the reduction of color shading due to light leakage from adjacent light emitting blocks and the suppression of degradation in color reproducibility, in a backlight device which comprises light sources of a plurality of colors and is capable of local dimming control.SOLUTION: It is determined whether color shading occurs or not per light emitting block. If color shading occurs in a light emitting block, one of adjacent light emitting blocks which causes the color shading is determined, and prescribed partial light sources located in positions close to a boundary to the adjacent light emitting block determined to cause the color shading, out of light sources of the light emitting block where the color shading occurs are taken as a correction object to perform brightness correction. Brightness of light sources as the correction object is corrected so that a color tone of a prescribed boundary area including the light sources as the correction object and prescribed partial light sources located in positions close to the boundary out of a plurality of light sources of the adjacent light emitting block determined to cause the color shading is approximated to a color tone of the adjacent light emitting block determined to cause the color shading.

Description

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

  Conventionally, there is a local dimming control technique in which a backlight is divided into a plurality of light emission blocks and the luminance is controlled and changed for each light emission block according to the luminance level of an input image signal. Each light emitting block is composed of one or more light sources (LEDs, etc.). This local dimming control is also applied to a backlight using LEDs of three colors of red, green, and blue as light sources (see Patent Document 1).

  In local dimming control of a backlight in which each light-emitting block is composed of LEDs of a plurality of colors, the color of each light-emitting block changes little by little due to leakage light from adjacent light-emitting blocks. In particular, when the luminance difference between adjacent light emitting blocks is large, color unevenness due to the color components of the LEDs of the adjacent light emitting blocks occurs.

  Detects the image signal displayed for each area of the liquid crystal panel, determines whether color unevenness occurs from the detected image signal, and emits light from the light source of the light-emitting block corresponding to the area where color unevenness is determined to occur There is a technique for reducing color unevenness by approaching light (Patent Document 2).

JP 2005-338857 A Japanese Patent No. 4487006

  However, in Patent Document 1, only luminance and color are locally changed in units of light emission blocks. Therefore, when the luminance difference between the adjacent light emitting blocks increases, the light of the specific color LED in the light emitting block that emits bright light strongly emerges as leakage light. For this reason, the light emission block which emits light darkly changes its color and causes uneven color.

  Further, in Patent Document 2, the light emission block corresponding to the region where the occurrence of the color unevenness is detected is controlled to be white light, and the light emission color of the light emission block in the periphery of the light emission block is also controlled to be white. In this case, since the color of the light emission block is set to white in order to correct the color unevenness, the backlight cannot be emitted with the light emission color originally assumed for the light emission block that has been corrected.

  Even if the light emitting block including the peripheral portion emits white light, the light of the specific color LED in the light emitting block that emits light brightly emits as strong leakage light when the luminance difference between adjacent light emitting blocks exceeds a certain level. The taste changes and uneven color occurs. This is due to the fact that the light emission center of each color is shifted depending on the arrangement position of the LED of each color when the light emission block is composed of LEDs of a plurality of colors. Even if a certain light emitting block emits white light as a whole, the color of light leaking to the adjacent light emitting block tends to be strong in the color of the LED arranged at the position closest to the adjacent light emitting block.

Further, in Patent Document 2, since the light emission rate is changed so that the light emission is changed to white light in all the light emission blocks adjacent to the light emission block corresponding to the region where the occurrence of the color unevenness is detected, the color unevenness is reduced. There are many light-emitting blocks that are affected by the light-emitting rate adjustment. That is, there is a problem that the color reproducibility is deteriorated because it is not possible to emit light with the originally assumed emission color.

  Accordingly, the present invention reduces color unevenness caused by light leakage from adjacent light emitting blocks and colors in a backlight device that is divided into light emitting blocks composed of light sources of a plurality of colors, and the luminance of each light emitting block can be controlled independently. The object is to achieve both reduction in reproducibility.

The present invention is divided by a plurality of light emitting blocks capable of independently controlling light emission, and each light emitting block has a backlight in which a plurality of light sources of a plurality of light emitting colors are arranged,
A local dimming control unit that determines luminance for each light-emitting block and light source according to an input image signal;
For each light-emitting block, based on the luminance determined by the local dimming control unit, it is determined whether or not color unevenness that is a change in color caused by light leakage from an adjacent light-emitting block occurs, and color unevenness A color unevenness determination unit that determines which light emission block of a plurality of adjacent light emission blocks generates color unevenness with respect to the light emission block determined to generate
Among a plurality of light sources of light emitting blocks determined to cause color unevenness, a predetermined part arranged at a position close to a boundary with an adjacent light emitting block determined to generate color unevenness for the light emitting block A color unevenness correction unit that corrects luminance with the light source of
A backlight control unit that emits light at a luminance corrected by the color unevenness correction unit for the light source to be corrected, and a light source other than the light source to be corrected at a luminance determined by the local dimming control unit;
Is a backlight device.

The present invention is a method for controlling a backlight device including a backlight that is divided by a plurality of light emitting blocks that can independently control light emission, and each light emitting block is provided with a plurality of light sources of a plurality of light emitting colors. ,
A local dimming control step for determining luminance for each light-emitting block and each light source according to an input image signal;
For each light-emitting block, based on the luminance determined by the local dimming control step, it is determined whether or not color unevenness that is a color change caused by light leakage from an adjacent light-emitting block occurs, and color unevenness A color unevenness determination step of determining which light emission block among a plurality of adjacent light emission blocks generates color unevenness with respect to the light emission block determined to be generated;
Among a plurality of light sources of light emitting blocks determined to cause color unevenness, a predetermined part arranged at a position close to a boundary with an adjacent light emitting block determined to generate color unevenness for the light emitting block Color unevenness correction step of correcting the brightness with the light source of
A backlight control step of causing the light source to be corrected to emit light at a luminance corrected by the color unevenness correction step, and a light source other than the light source to be corrected to emit light at a luminance determined by the local dimming control step;
Is a control method of a backlight device having

  According to the present invention, in a backlight device that is divided into light-emitting blocks composed of light sources of a plurality of colors and can independently control the luminance for each light-emitting block, color unevenness and color caused by light leakage from adjacent light-emitting blocks are reduced. It is possible to achieve both suppression of reproducibility degradation.

1 is a block diagram illustrating a configuration of an image display device according to a first embodiment. Schematic diagram showing time variation of input image signal and light emission block Schematic diagram showing the LED arrangement in one light-emitting block Schematic diagram showing changes in light emission luminance for each light emission block Flow chart for determining occurrence of uneven color Schematic diagram showing the arrangement of adjacent light-emitting blocks Color unevenness correction flowchart Schematic diagram showing an application example of uneven color correction processing

Example 1
A first embodiment will be described. FIG. 1 is a block diagram showing the configuration of an image display apparatus to which the present invention is applied.
The display control apparatus in FIG. 1 includes a local dimming control unit 101, a color unevenness determination unit 102, a color unevenness correction unit 103, a backlight control unit 104, a backlight unit 105, a display unit 106, and an image processing unit 107. In this embodiment, the backlight unit 105 is divided into a plurality of light emission blocks, and light emission can be controlled independently for each light emission block. The display unit 106 is a transmissive liquid crystal panel, and displays an image based on the input image signal by adjusting the transmittance of light from the backlight unit 105 for each pixel according to the input image signal. A display area of the display unit 106 corresponding to each light emission block of the backlight unit 105 is hereinafter referred to as a “divided area”.

  First, in FIG. 1, the local dimming control unit 101 calculates the luminance control value for each light emission block from the input image signal. The luminance control value for each light emitting block is a luminance control value for controlling the brightness of the LEDs constituting each light emitting block. Here, a case will be described in which one light-emitting block includes a plurality of light-emitting color light sources, that is, one red LED, two green LEDs, and one blue LED. In the backlight unit 105, the luminance control value of the red LED in the light emitting block (i, j) in the i-th row in the vertical direction and the j-th column in the horizontal direction is BD_R (i, j). The luminance control value of the first green LED of the light emission block (i, j) is BD_G1 (i, j), the luminance control value of the second green LED is BD_G2 (i, j), and the luminance control value of the blue LED Is BD_B (i, j).

  FIG. 2 schematically shows an example of the time change of the image signal input to the local dimming control unit 101 and the lighting state of the light emitting block. 2A shows a frame image of an input image signal, and FIG. 2B shows each light emission block of the backlight unit 105 when each frame image of FIG. 2A is displayed on the display unit 106. Indicates the lighting state. Here, the case where the backlight unit 105 is divided into a total of 15 light emission blocks of 5 horizontal x 3 vertical is illustrated, but the method of dividing the backlight unit 105 by the light emission blocks is not limited to this.

  Here, a uniform dark image is displayed in the frame 1011 of the image signal. In the image signal frames 1012 and 1013, there is a bright windmill image in the center of the screen against the dark background, and the windmill blades change with time. When the image signal of the frame 1011 is input, the local dimming control unit 101 calculates the luminance control value of each light emission block so that the light emission block lighting state 1014 is obtained. When the image signals of the frames 1012 and 1013 are input, the local dimming control unit 101 calculates the luminance control value of each light emission block so that the light emission block lighting states 1015 and 1016 are obtained.

In this light emitting block lighting state 1014, 1015, 1016, one square frame painted with diagonal lines indicates a light emitting block that is lit with a dark luminance control value, and one square frame painted with white has a bright luminance control value. Illuminated light-emitting blocks are shown. As shown in FIG. 2B, for example, the light emission block 1017 does not change the image signal input to the divided area of the corresponding display unit 106, but the light emission block 1018 is input to the divided area of the corresponding display unit 106. The image signal to be changed changes.

  In the light-emitting block lighting states 1015 and 1016, only one light-emitting block 1018 corresponding to the divided area in which the images of the windmills of the frames 1012 and 1013 are displayed is lighted with a bright luminance control value. Is the control that lights up all the time. As described above, the local dimming control unit 101 calculates the luminance control value for each light emission block based on the input image signal, and outputs the luminance control value to the color unevenness determination unit 102 and the color unevenness correction unit 103.

  FIG. 3 is a schematic diagram showing the LED arrangement in one light emitting block. As shown in FIG. 3, each light-emitting block has four LEDs, a red LED (R) 1021, a first green LED (G1) 1022, a second green LED (G2) 1023, and a blue LED (B) 1024. Consists of LEDs. In FIG. 3, four LEDs are schematically represented by four rectangles. However, an actual LED is a point light source, and light emitted from the LED diffuses around the point light source to become a surface light source.

  FIG. 4 schematically shows changes in the light emission luminance of the respective color LEDs of the light emission block 1017 and the light emission block 1018 of FIG. FIG. 4A shows a light emission state of each color LED of the light emission blocks 1017 and 1018 when the image signal of the frame 1011 in FIG. 2 is input. FIG. 4B shows a light emission state of each color LED of the light emission blocks 1017 and 1018 when the image signal of the frame 1012 in FIG. 2 is input.

  The color unevenness determination unit 102 receives the luminance control values BD_R (i, j), BD_G1 (i, j), BD_G2 (i, j), and BD_B (BD_B () of each color LED of each light-emitting block input from the local dimming control unit 101. Based on i, j), it is determined whether color unevenness occurs in each light emitting block.

FIG. 5 is a flowchart illustrating a determination process performed by the color unevenness determination unit 102 for each frame to determine whether color unevenness that is a color change caused by light leakage from an adjacent light emission block occurs for each light emission block. It is.
First, in step S1051, the color unevenness determination unit 102 calculates the luminance ratio of the red LED, the luminance ratio of the green LED, and the luminance ratio of the blue LED for each light emitting block, and proceeds to step S1052. Calculation of the luminance ratio of each color LED is performed using equations (1) to (4). Here, the luminance ratio of the red LED, the luminance ratio of the green LED, and the luminance ratio of the blue LED of the light emitting block in the i-th row in the vertical direction and the j-th column in the horizontal direction are respectively Rh (i, j) and Gh (i , J) and Bh (i, j). In addition, the luminance of the light-emitting block in the i-th row in the vertical direction and the j-th column in the horizontal direction is Sh (i, j).

Sh (i, j) = BD_R (i, j) + BD_G1 (i, j) + BD_G2 (i, j) + BD_B (i, j) (1)
Rh (i, j) = BD_R (i, j) ÷ Sh (i, j) (2)
Gh (i, j) = {BD_G1 (i, j) + BD_G2 (i, j)} / Sh (i, j) (3)
Bh (i, j) = BD_B (i, j) ÷ Sh (i, j) (4)

  In step S1052, the color unevenness determination unit 102 calculates the luminance ratio of the red LED, the luminance ratio of the green LED, and the luminance ratio of the blue LED for each light emitting block in the boundary region with the adjacent light emitting block, and the process proceeds to step S1053. . Here, a method of calculating the luminance ratio of each color LED in a boundary region between a light emitting block and a light emitting block adjacent to the light emitting block will be described with reference to FIGS.

  FIG. 6A is a schematic diagram in which the light emission block 1018 and eight light emission blocks adjacent thereto are extracted in the light emission block lighting state 1015 of FIG. In FIG. 6A, the light emitting block 1018 is set to coordinates (i, j) (i-th row in the vertical direction and j-th row in the horizontal direction), and the vertical coordinates are i-1, i, i + 1, A light emitting block of 3 rows × 3 columns with horizontal coordinates j−1, j, j + 1 is shown. FIG. 6B schematically shows the arrangement of each color LED in each light emitting block shown in FIG. Hereinafter, a case where color unevenness determination is performed for the light emission block 1018 will be described as an example.

  The color unevenness determination unit 102 determines whether or not color unevenness can occur in the light emission block (i, j) to be determined for each of the 8 light emission blocks adjacent to the light emission block (i, j) to be determined. judge. In other words, it is determined in which direction of the eight directions the color unevenness occurs in the light emission block (i, j) to be determined. The eight directions are up / down / left / right, left upper left, right upper right, left lower left, right right lower. Here, the expression “adjacent” is also used for the light-emission block to be determined and the four light-emission blocks that are obliquely left upper, upper right, lower left, and lower right.

  First, the luminance ratio of the red LED and the luminance of the green LED in the boundary region between the light emitting block (i, j) to be determined and the light emitting block (i−1, j−1) adjacent to the left oblique upper direction. The example which calculates a ratio and the luminance ratio of blue LED is shown. A boundary region between the light emission block (i, j) to be determined and the adjacent light emission block (i-1, j-1) is a region surrounded by a solid line 1601 in FIG. This boundary area includes the following four LEDs. The red LED of the light emission block (i, j) to be determined, the green LED (G2) of the upper adjacent light emission block (i-1, j), and the adjacent light emission block (i-1, j-1) in the upper left direction. ) Blue LED, and green LED (G1) of the adjacent light emitting block (i, j-1) in the left direction. The luminance ratio of the red LED, the luminance ratio of the green LED, and the luminance ratio of the blue LED in the boundary region 1601 are Rh00 (i, j), Gh00 (i, j), and Bh00 (i, j), respectively. The luminance of the light emission block (i, j) is Sh00 (i, j).

  Here, the code “00” is 0th in the vertical direction and 0 in the horizontal direction from the upper left among the eight boundary regions defined between the light-emitting block to be determined and the eight light-emitting blocks adjacent thereto. Indicates that this is the th boundary region. Similarly, a boundary region between the light emission block (i, j) to be determined and the light emission block (i−1, j) is represented by reference numeral 01. A boundary region between the light emission block (i, j) to be determined and the light emission block (i−1, j + 1) is represented by reference numeral 02. A boundary region between the light emission block (i, j) to be determined and the light emission block (i, j-1) is denoted by reference numeral 10. A boundary region between the light emission block (i, j) to be determined and the light emission block (i, j + 1) is denoted by reference numeral 11. A boundary region between the light emission block (i, j) to be determined and the light emission block (i + 1, j−1) is represented by reference numeral 20. A boundary region between the light emission block (i, j) to be determined and the light emission block (i + 1, j) is denoted by reference numeral 21. A boundary region between the light emission block (i, j) to be determined and the light emission block (i + 1, j + 1) is represented by reference numeral 22.

  As the luminance of the blue LED used in the luminance ratio calculation of the boundary region 00, the luminance BD_B (i-1, j-1) of the blue LED of the light emitting block (i-1, j-1) adjacent in the diagonally upper left direction is used. Use. Further, as the luminance of the green LED, the luminance BD_G2 (i−1, j) of the second green LED of the light emitting block (i−1, j) adjacent in the upward direction, and the light emitting block (i, j, adjacent in the left direction). The luminance BD_G1 (i, j-1) of the first green LED of j-1) is used. Further, as the luminance of the red LED, the luminance BD_R (i, j) of the red LED of the light emission block (i, j) to be determined is used.

The luminance ratio Rh00 (i, j) of the red LED in the boundary area 00, the luminance Gh00 of the green LED
Formulas for obtaining (i, j), the luminance ratio Bh00 (i, j) of the blue LED and the luminance Sh00 (i, j) of the boundary region 00 are shown in the following equations (5) to (8).

Sh00 (i, j) = BD_R (i, j) + BD_G2 (i-1, j) + BD_G1 (i, j-1) + BD_B (i-1, j-1) (5)
Rh00 (i, j) = BD_R (i, j) ÷ Sh00 (i, j) (6)
Gh00 (i, j) = {BD_G1 (i, j-1) + BD_G2 (i-1, j)} / Sh00 (i, j) (7)
Bh00 (i, j) = BD_B (i-1, j-1) / Sh00 (i, j) (8)

  Similarly, the color unevenness determination unit 102 calculates the luminance ratio of each color LED in the boundary region between the light emission block (i, j) to be determined and the remaining seven light emission blocks.

The luminance ratio of each color LED in the boundary region 01 between the light emitting block (i, j) to be determined and the light emitting block (i-1, j) is Rh01 (i, j), Gh01 (i, j), Bh01 (i, j) The luminance of the boundary region 01 is Sh01 (i, j).
The luminance ratio of each color LED in the boundary region 02 between the light emission block (i, j) to be determined and the light emission block (i-1, j + 1) is Rh02 (i, j), Gh02 (i, j), Bh02 (i, j) The brightness of the boundary region 02 is Sh02 (i, j).
The luminance ratio of each color LED in the boundary region 10 between the light emission block (i, j) to be determined and the light emission block (i, j-1) is Rh10 (i, j), Gh10 (i, j), Bh10 (i, j) The brightness of the boundary region 10 is Sh10 (i, j).
The luminance ratio of each color LED in the boundary region 11 between the light emitting block (i, j) to be determined and the light emitting block (i, j + 1) is Rh11 (i, j), Gh11 (i, j), Bh11 (i, j). The brightness of the boundary region 11 is Sh11 (i, j).
The luminance ratio of each color LED in the boundary region 20 between the light emission block (i, j) to be determined and the light emission block (i + 1, j-1) is Rh20 (i, j), Gh20 (i, j), Bh20 (i, j) The luminance of the boundary region 20 is Sh20 (i, j).
The luminance ratio of each color LED in the boundary region 21 between the light emitting block (i, j) to be determined and the light emitting block (i + 1, j) is Rh21 (i, j), Gh21 (i, j), Bh21 (i, j). The brightness of the boundary region 21 is Sh21 (i, j).
The luminance ratio of each color LED in the boundary region 22 between the light emission block (i, j) to be determined and the light emission block (i + 1, j + 1) is Rh22 (i, j), Gh22 (i, j), Bh22 (i, j). The brightness of the boundary area 22 is Sh22 (i, j).

  In step S1053, the color unevenness determination unit 102 determines the boundary ratio between the luminance ratio of each color LED of the determination target light emission block (i, j) and the light emission block adjacent to the determination target light emission block (i, j). The difference between the luminance ratio of each color LED in FIG. The color unevenness determination unit 102 calculates a difference between the luminance ratios of the boundary areas in the eight directions with respect to the determination target light emission block (i, j) and the luminance ratio of the determination target light emission block (i, j), and step The process proceeds to S1054. The color unevenness determination unit 102 uses the brightness ratio of each color LED of the light emission block (i, j) to be determined, calculated in step S1051. Further, the color unevenness determination unit 102 uses the one calculated in step S1052 as the luminance ratio of each color LED in each of the boundary areas in the eight directions.

In FIG. 6A, the luminance ratio of each color LED of the determination target light emission block (i, j), and the determination target light emission block (i, j) and the adjacent light emission block (i-1, j-1). An example is shown in which the difference between the luminance ratio of each color LED in the boundary region 00 is calculated. Where red L
The difference of the luminance ratio of the ED is CR00 (i, j), the difference of the luminance ratio of the green LED is CG00 (i, j), and the difference of the luminance ratio of the blue LED is CB00 (i, j). Formulas for calculating these difference values CR00 (i, j), CG00 (i, j), and CB00 (i, j) are shown in the following formulas (9) to (11).

CR00 (i, j) = | 1-Rh00 (i, j) / Rh (i, j) | ... Formula (9)
CG00 (i, j) = | 1-Gh00 (i, j) / Gh (i, j) | ... Formula (10)
CB00 (i, j) = | 1-Bh00 (i, j) / Bh (i, j) | ... Formula (11)

  Next, in step S1054, the color unevenness determination unit 102 determines whether or not the difference CR00 (i, j) in the luminance ratio of the red LED calculated in step S1053 is greater than or equal to the threshold value HRth. The threshold value HRth is a threshold value for determining whether or not red color unevenness occurs. The color unevenness determination unit 102 proceeds to step S1057 if the luminance ratio difference CR00 (i, j) of the red LED calculated in step S1053 is greater than or equal to HRth, and proceeds to step S1055 if the value is smaller than HRth.

  In step S1055, the color unevenness determination unit 102 determines whether or not the difference CG00 (i, j) in the luminance ratio of the green LED calculated in step S1053 is greater than or equal to the threshold HGth. The threshold HGth is a threshold for determining whether or not green color unevenness occurs. The color unevenness determination unit 102 proceeds to step S1057 if the luminance ratio difference CG00 (i, j) of the green LED calculated in step S1053 is greater than or equal to HGth, and proceeds to step S1056 if the value is smaller than HGth.

  In step S1056, the color unevenness determination unit 102 determines whether or not the difference CB00 (i, j) in the luminance ratio of the blue LED calculated in step S1053 is greater than or equal to the threshold HBth. The threshold value HBth is a threshold value for determining whether or not green color unevenness occurs. The color unevenness determination unit 102 proceeds to step S1057 if the difference CB00 (i, j) in the luminance ratio of the blue LED calculated in step S1053 is equal to or larger than HBth, and proceeds to step S1058 if the value is smaller than HBth.

  In step S1057, the color unevenness determination unit 102 determines whether or not the luminance of the light-emitting block to be determined calculated in step S1051 is smaller than the luminance Sh (i−1, j−1) of the adjacent light-emitting block calculated in step S1051. Determine. The color unevenness determination unit 102 proceeds to step S1059 when the luminance of the determination target light emission block−the luminance of the adjacent light emission block <0, and proceeds to step S1059 when the determination target light emission block luminance−the luminance of the adjacent light emission block ≧ 0. The process proceeds to step S1058.

  In step S1058, the color unevenness determination unit 102 sets the color unevenness determination value in the direction of the boundary region 00 (the direction of the adjacent light emission block (i-1, j-1)) to 0, and the process proceeds to step S1060. When the color unevenness determination value in a certain direction is 0, it is determined that the color unevenness determination unit 102 has determined that color unevenness caused by light leakage from the adjacent light emitting block in that direction does not occur in the light emitting block to be determined. means.

In step S1059, the color unevenness determination unit 102 sets the color unevenness determination value in the direction of the boundary region 00 (the direction of the adjacent light emission block (i-1, j-1)) to 1, and proceeds to step S1060. When the color unevenness determination value in a certain direction is 1, it means that the color unevenness determination unit 102 has determined that color unevenness due to light leakage from the adjacent light emitting block in that direction occurs in the light emitting block to be determined.

  Hereinafter, the color unevenness determination value in the boundary region 00 direction (light emission block (i-1, j-1) direction) is set to TUL (i, j) for the light emission block (i, j) to be determined. The color unevenness determination value in the boundary region 01 direction (light emission block (i-1, j) direction) is assumed to be TU (i, j). The color unevenness determination value in the boundary area 02 direction (light emission block (i-1, j + 1) direction) is assumed to be TUR (i, j). Let TL (i, j) be the color unevenness determination value in the boundary region 10 direction (light emission block (i, j-1) direction). The color unevenness determination value in the boundary region 11 direction (light emission block (i, j + 1) direction) is assumed to be TR (i, j). The color unevenness determination value in the boundary area 20 direction (light emission block (i + 1, j-1) direction) is assumed to be TDL (i, j). Let TD (i, j) be the color unevenness determination value in the boundary region 21 direction (light emission block (i + 1, j) direction). The color unevenness determination value in the boundary region 22 direction (light emission block (i + 1, j + 1) direction) is assumed to be TDR (i, j).

In step S1060, the color unevenness determination unit 102 determines whether the color unevenness determination has been completed for all the adjacent light emitting blocks in the eight directions of the determination target light emitting block. The color unevenness determination unit 102 proceeds to step S1061 if the color unevenness determination is completed in all eight directions, and returns to step S1053 if not completed.
In step S1061, the color unevenness determination unit 102 determines whether or not the color unevenness determination has been completed for all the light-emitting blocks. If the color unevenness determination has been completed for all the light-emitting blocks, the process proceeds to step S1062 and must be completed. Return to step S1053.
In step S <b> 1062, the color unevenness determination unit 102 outputs the color unevenness determination value in each direction of each light emitting block to the color unevenness correction unit 103.

  As described above, in this embodiment, the difference between the luminance ratio of each color LED of the light emitting block to be determined and the luminance ratio of each color LED in the boundary region between the light emitting block to be determined and the adjacent light emitting block is calculated. . Then, it is determined whether or not color unevenness occurs for each direction of the adjacent light-emitting block depending on whether or not the difference is equal to or greater than a predetermined threshold for the light source of at least one of the colors. A light emission block in which at least one of eight directions of color unevenness determination values TUL, TU, TUR, TL, TR, TDL, TD, and TDR is 1 is determined as a light emission block in which color unevenness occurs.

  The color unevenness correction unit 103 is based on the luminance control value of each light emission block input from the local dimming control unit 101 and the color unevenness determination value input from the color unevenness determination unit 102, and the luminance control value of each light emission block. The brightness correction control value that is the correction value of is calculated. The color unevenness correction unit 103 outputs the calculated luminance correction control value to the backlight control unit 104. The backlight control unit 104 causes the LEDs of the respective light emission blocks of the backlight unit 105 to emit light based on the luminance correction control value input from the color unevenness correction unit 103. The luminance correction control value of the red LED of the light emission block (i, j) is D_R (i, j), the luminance correction control value of the green LED (G1) is D_G1 (i, j), and the luminance correction control value of the green LED (G2). The value is D_G2 (i, j), and the luminance correction control value of the blue LED is D_B (i, j).

Hereinafter, control for calculating the luminance correction control value of each color LED of each light-emitting block for each frame and correcting color unevenness will be described with reference to the flowchart of FIG. 7 and the schematic diagram of FIG.
FIG. 7 is a flowchart showing a process for calculating the luminance correction control value of each color LED of each light emitting block.
First, in step S1701, the color unevenness correction unit 103 initializes the coordinates i and j of the light emission block to be corrected to 0. i is a variable for counting the coordinates in the vertical direction (row direction), and j is a variable for counting the coordinates in the horizontal direction (column direction).

  In step S1702, the color unevenness correction unit 103 determines whether the color unevenness determination values TL (i, j) and TR (i, j) of the light emission block (i, j) to be corrected are 1. The color unevenness correction unit 103 proceeds to step S1703 if at least one of the color unevenness determination values TL (i, j) and TR (i, j) is 1, and proceeds to step S1704 if both are 0.

  In step S <b> 1703, the color unevenness correction unit 103 determines that color unevenness does not occur in the right and left direction of the light emission block (i, j) to be corrected, and uses the luminance control value of the light emission block (i, j) as it is. Let i, j) be the brightness correction control value. That is, the color unevenness correction unit 103 outputs the luminance control value of each color LED of the light emission block (i, j) input from the local dimming control unit 101 as it is as the luminance correction control value of each color LED of the light emission block (i, j). Then, the process proceeds to step S1705. That is, the color unevenness correction unit 103 uses BD_R (i, j), BD_G1 (i, j), BD_G2 (i, j), and BD_B (i, j) as they are as D_R (i, j) and D_G1 (i, j, respectively). j), D_G2 (i, j), and D_B (i, j).

  In step S1704, the color unevenness correction unit 103 determines that color unevenness occurs in the left-right direction of the light emission block (i, j) to be corrected, and the direction in which color unevenness occurs in the light emission block (i, j). The brightness correction control value corresponding to is calculated, and the process proceeds to step S1705.

First, a method of calculating the luminance correction control value when the color unevenness determination value TL (i, j) is 1, that is, when color unevenness in the left direction occurs will be described.
The color unevenness correction unit 103 is a part of the LEDs (red LEDs) included in the boundary region 10 with the left adjacent light emitting block (i, j-1) among the respective color LEDs of the light emitting block (i, j) to be corrected. The luminance correction control value is calculated with (R) and the green LED (G2)) as correction targets. The color unevenness correction unit 103 calculates the luminance correction control value of the correction target LED so that the color of the boundary region 10 approaches the color of the light emitting block (i, j-1) on the left side. The color unevenness correction unit 103 sets the luminance ratio of each color light source included in the boundary region 10 to the luminance of the boundary region 10 to the luminance ratio of each color light source included in the left adjacent light emission block to the luminance of the left adjacent light emission block. The brightness correction control value of the correction target LED is calculated so as to approach. As will be described later, the backlight control unit 104 causes light sources other than the light source to be corrected to emit light based on the luminance control value output from the local dimming control unit 101.

The uneven color correction unit 103 calculates the luminance correction control value D_R (i, j) of the red LED of the light emission block (i, j) to be corrected as follows. That is, the color unevenness correction unit 103 sets the luminance control value BD_R (i, j) of the red LED of the light emitting block (i, j) to be corrected and the red LED of the light emitting block (i, j-1) adjacent to the left side. The luminance control value BD_R (i, j-1) is weighted and added.
Further, the color unevenness correction unit 103 calculates the luminance correction control value D_G2 (i, j) of the green LED (G2) of the light emission block (i, j) to be corrected as follows. That is, the color unevenness correction unit 103 determines the luminance control value BD_G2 (i, j) of the green LED (G2) of the light emission block (i, j) to be corrected and the light emission block (i, j-1) on the left side. The luminance control value BD_G2 (i, j-1) of the green LED (G2) is weighted and added.

On the other hand, the color unevenness correction unit 103 is an LED (green LED) that is not included in the boundary region 10 with the left adjacent light emitting block (i, j-1) among the respective color LEDs of the light emitting block (i, j) to be corrected. The luminance correction control values for (G1) and blue LED (B)) are calculated as follows.
That is, the color unevenness correction unit 103 receives the luminance control value BD_G1 (i, j) of the green LED (G1) of the light emission block (i, j) to be corrected, which is input from the local dimming control unit 101, as it is. ) Brightness correction control value D_G1 (i, j).
Further, the color unevenness correction unit 103 directly uses the luminance control value BD_B (i, j) of the blue LED of the light emitting block (i, j) to be corrected input from the local dimming control unit 101 as it is. Let D_B (i, j).

The formulas for calculating the brightness correction control value when TL (i, j) is 1 are shown in the following formulas (12) to (15).

D_R (i, j) = α × BD_R (i, j−1) + (1−α) × BD_R (i, j) (12)
D_G1 (i, j) = BD_G1 (i, j) (13)
D_G2 (i, j) = β × BD_G2 (i, j−1) + (1-β) × BD_G2 (i, j) (14)
D_B (i, j) = BD_B (i, j) (15)

α is a constant for changing the correction amount of the red LED. When α = 1, the luminance control value BD_R (i, j−1) of the red LED of the light emitting block (i, j−1) on the left is directly used as the red LED of the light emitting block (i, j) to be corrected. The brightness correction control value D_R (i, j) is obtained.
β is a constant that changes the correction amount of the green LED. When β = 1, the luminance control value BD_G2 (i, j-1) of the green LED of the light emitting block (i, j-1) on the left is directly used as the green LED of the light emitting block (i, j) to be corrected. The brightness correction control value D_G2 (i, j) is obtained.
When α and β are 1, the luminance ratio of the red LED, the luminance ratio of the green LED, and the luminance ratio of the blue LED are equal in the boundary region 10 and the light emitting block (i, j−1) on the left side.

  When the light emitting block (i, j-1) on the left side of the light emitting block (i, j) to be corrected has high luminance, the low luminance correction is performed from the light emitting block (i, j-1) on the left side with high luminance. Light leakage occurs to the target light-emitting block (i, j). This light leakage is light leakage derived from the LED arranged at a position close to the boundary with the light emitting block (i, j) to be corrected among the LEDs of the light emitting block (i, j-1) on the left side. Due to this light leakage, in the light emitting block (i, j) to be corrected, the region close to the boundary with the left adjacent light emitting block (i, j-1) changes in color and causes color unevenness. However, this color unevenness is suppressed when each color LED of the light emission block (i, j) to be corrected emits light based on the brightness correction control value calculated as described above. This is because the luminance ratio of each color LED in the boundary region 10 between the light emission block (i, j) to be corrected and the left adjacent light emission block (i, j-1) is equal to the left adjacent light emission block (i, j). This is because the luminance ratio of each color LED in -1) is equal.

  If α and β are smaller than 1, LEDs (R, G2) arranged near the boundary with the light emitting block (i, j−1) on the left side among the LEDs of the light emitting block (i, j) to be corrected The amount of correction of the brightness control value becomes smaller. However, since the luminance ratio of each color LED in the boundary region 10 and the luminance ratio of each color LED in the light emitting block (i, j−1) on the left side are close to each other in accordance with the values of α and β, Color unevenness in the light emission block (i, j) to be corrected is suppressed. The coefficients α and β may be predetermined values, or may be arbitrarily set by the user within the range of 0 <α ≦ 1 and 0 <β ≦ 1.

Next, formulas for calculating the brightness correction control value when TR (i, j) is 1 are shown in the following formulas (16) to (19).

D_R (i, j) = BD_R (i, j) (16)
D_G1 (i, j) = β × BD_G1 (i, j + 1) + (1-β) × BD_G1 (i, j) (17)
D_G2 (i, j) = BD_G2 (i, j) (18)
D_B (i, j) = γ × BD_B (i, j + 1) + (1−γ) × BD_B (i, j) (19)

  γ is a constant that changes the correction amount of the blue LED. When γ = 1, the luminance control value BD_B (i, j + 1) of the blue LED of the light emitting block (i, j + 1) on the right is directly used as the luminance correction control value of the blue LED of the light emitting block (i, j) to be corrected. D_B (i, j). If β and γ are smaller than 1, the luminance of the LED (G1, B) arranged near the boundary with the right adjacent light emitting block (i, j + 1) among the LEDs of the light emitting block (i, j) to be corrected. The correction amount of the control value is reduced. However, since the luminance ratio of each color LED in the boundary region 11 and the luminance ratio of each color LED in the right-side light emitting block (i, j + 1) are close to each other according to the values of β and γ, the correction target The color unevenness in the light emission block (i, j) is suppressed.

In step S1705, the color unevenness correction unit 103 determines whether or not the column count value j of the light emission block has reached the maximum value. If j is not the maximum value, the process proceeds to step S1706. The process proceeds to step S1707.
In step S1706, the color unevenness correction unit 103 increments the column count value j and proceeds to step S1702.
In step S1707, the color unevenness correction unit 103 determines whether or not the row count value i has reached the maximum value. If i is not the maximum value, the process proceeds to step S1708, and if i is the maximum value, the process proceeds to step S1709. .
In step S1708, the color unevenness correction unit 103 increments the row count value i, initializes j to 0, and proceeds to step S1702.

In step S1709, the color unevenness correction unit 103 initializes the coordinates i and j of the light emission block to be corrected to 0, and the process proceeds to step S1710.
In step S1710, the color unevenness correction unit 103 determines whether the color unevenness determination values TU (i, j) and TD (i, j) of the light emission block (i, j) to be corrected are 1. The color unevenness correction unit 103 proceeds to step S1712 when at least one of the color unevenness determination values TU (i, j) and TD (i, j) is 1, and proceeds to step S1711 when both are 0.

  In step S1711, the color unevenness correction unit 103 determines that no color unevenness occurs in the vertical direction of the light emission block (i, j) to be corrected, and uses the luminance control value of the light emission block (i, j) as it is. Let i, j) be the brightness correction control value. That is, the color unevenness correction unit 103 uses the luminance control value of each color LED of the light emission block (i, j) input from the local dimming control unit 101 as the luminance correction control value of each color LED of the light emission block (i, j). The data is output as it is, and the process proceeds to step S1713. That is, the color unevenness correction unit 103 uses BD_R (i, j), BD_G1 (i, j), BD_G2 (i, j), and BD_B (i, j) as they are as D_R (i, j) and D_G1 (i, j, respectively). j), D_G2 (i, j), and D_B (i, j).

  In step S1712, the color unevenness correction unit 103 determines that color unevenness occurs in the vertical direction of the light emission block (i, j) to be corrected, and the direction in which color unevenness occurs in the light emission block (i, j). The brightness correction control value corresponding to is calculated, and the process proceeds to step S1713.

First, a method of calculating the luminance correction control value when the color unevenness determination value TU (i, j) is 1, that is, when an upward color unevenness occurs will be described.
In this case, the color unevenness correction unit 103 includes LEDs (red LEDs) included in the boundary region 01 with the upper adjacent light emission block (i−1, j) among the respective color LEDs of the light emission block (i, j) to be corrected. The luminance correction control value of (R) and the green LED (G1)) is calculated as follows.

The uneven color correction unit 103 calculates the luminance correction control value D_R (i, j) of the red LED of the light emission block (i, j) to be corrected as follows. That is, the color unevenness correction unit 103 determines the luminance control value BD_R (i, j) of the red LED of the light emission block (i, j) to be corrected and the red LED of the upper adjacent light emission block (i-1, j). The luminance control value BD_R (i-1, j) is weighted and added.
Further, the color unevenness correction unit 103 calculates the luminance correction control value D_G1 (i, j) of the green LED (G1) of the light emission block (i, j) to be corrected as follows. That is, the color unevenness correction unit 103 determines the luminance control value BD_G1 (i, j) of the green LED (G1) of the light emission block (i, j) to be corrected and the light emission block (i−1, j) adjacent to the upper side. The luminance control value BD_G1 (i-1, j) of the green LED (G1) is weighted and added.

On the other hand, the color unevenness correction unit 103 is an LED (green LED) that is not included in the boundary region 01 with the upper adjacent light emitting block (i-1, j) among the respective color LEDs of the light emitting block (i, j) to be corrected. The luminance correction control values of (G2) and blue LED (B)) are calculated as follows.
That is, the color unevenness correction unit 103 directly inputs the luminance control value BD_G2 (i, j) of the green LED (G2) of the light emission block (i, j) to be corrected, which is input from the local dimming control unit 101, as the green LED (G2 ) Brightness correction control value D_G2 (i, j).
Further, the color unevenness correction unit 103 directly uses the luminance control value BD_B (i, j) of the blue LED of the light emitting block (i, j) to be corrected input from the local dimming control unit 101 as it is. Let D_B (i, j).

The formulas for calculating the brightness correction control value when TU (i, j) is 1 are shown in the following formulas (20) to (23).

D_R (i, j) = α × BD_R (i−1, j) + (1−α) × BD_R (i, j) (20)
D_G1 (i, j) = β × BD_G1 (i−1, j) + (1−β) × BD_G1 (i, j) (21)
D_G2 (i, j) = BD_G2 (i, j) Equation (22)
D_B (i, j) = BD_B (i, j) (23)

  When α and β are 1, the adjacent light emission block (i−1, j) and the boundary region 01 between the light emission block (i, j) to be corrected and the adjacent light emission block (i−1, j) The luminance ratio of the red LED, the luminance ratio of the green LED, and the luminance ratio of the blue LED are equal. Even when α and β are smaller than 1, the luminance ratio of each color LED of the adjacent light emission block (i−1, j), the light emission block (i, j) to be corrected, and the adjacent light emission block (i−1, j) The luminance ratio of each color LED in the boundary region 01 between the values becomes close to the extent corresponding to the values of α and β. Therefore, in the light emission block (i, j) to be corrected, color unevenness due to leakage light from the adjacent light emission block (i-1, j) is suppressed.

Next, the formulas for calculating the brightness correction control value when TD (i, j) is 1 are shown in the following formulas (24) to (27).

D_R (i, j) = BD_R (i, j) (24)
D_G1 (i, j) = BD_G1 (i, j) Expression (25)
D_G2 (i, j) = β × BD_G2 (i + 1, j) + (1-β) × BD_G2 (i, j) (26)
D_B (i, j) = γ × BD_B (i + 1, j) + (1−γ) × BD_B (i, j) ·
... Formula (27)

In step S1713, the color unevenness correction unit 103 determines whether or not the column count value j of the light emission block has reached the maximum value. If j is not the maximum value, the process proceeds to step S1714. If j is the maximum value, The process proceeds to step S1715.
In step S1714, the color unevenness correction unit 103 increments the column count value j and proceeds to step S1710.
In step S1715, the color unevenness correction unit 103 determines whether or not the row count value i has reached the maximum value. If i is not the maximum value, the process proceeds to step S1716. If i is the maximum value, the process proceeds to step S1717. .
In step S1716, the color unevenness correction unit 103 increments the row count value i, initializes j to 0, and proceeds to step S1710.

In step S1717, the color unevenness correction unit 103 initializes the coordinates i and j of the light emission block to be corrected to 0, and the process advances to step S1718.
In step S1718, the color unevenness correction unit 103 performs color unevenness determination values TUL (i, j), TUR (i, j), TDL (i, j), TDR (i) of the light emission block (i, j) to be corrected. , J) is 1. The color unevenness correction unit 103 proceeds to Step S1720 when at least one of the color unevenness determination values TUL (i, j), TUR (i, j), TDL (i, j), and TDR (i, j) is 1. If all 0, proceed to step S1719.

  In step S1719, the color unevenness correction unit 103 determines that the light emission block (i, j) to be corrected does not generate color unevenness in an oblique direction, and uses the luminance control value of the light emission block (i, j) as it is. Let i, j) be the brightness correction control value. That is, the color unevenness correction unit 103 uses the luminance control value of each color LED of the light emission block (i, j) input from the local dimming control unit 101 as the luminance correction control value of each color LED of the light emission block (i, j). The data is output as it is, and the process proceeds to step S1721. That is, the color unevenness correction unit 103 uses BD_R (i, j), BD_G1 (i, j), BD_G2 (i, j), and BD_B (i, j) as they are as D_R (i, j) and D_G1 (i, j, respectively). j), D_G2 (i, j), and D_B (i, j).

  In step S1720, the color unevenness correction unit 103 determines that color unevenness occurs in the light emitting block (i, j) to be corrected in an oblique direction, and the direction in which color unevenness occurs in the light emitting block (i, j). The brightness correction control value corresponding to is calculated, and the process proceeds to step S1721.

First, a method for calculating the luminance correction control value when the color unevenness determination value TUL (i, j) is 1, that is, when color unevenness in the diagonally upper left direction occurs will be described.
In this case, the color unevenness correction unit 103 includes the LEDs included in the boundary area 00 with the light emission block (i−1, j−1) on the upper left among the color LEDs of the light emission block (i, j) to be corrected. The brightness correction control value of (red LED (R)) is calculated as follows.
That is, the color unevenness correction unit 103 calculates the luminance correction control value D_R (i, j) of the red LED of the light emission block (i, j) to be corrected as follows. That is, the color unevenness correction unit 103 determines the luminance control value BD_R (i, j) of the red LED of the light emission block (i, j) to be corrected and the light emission block (i-1, j-1) on the upper left. The luminance control value BD_R (i-1, j-1) of the red LED is weighted and added.

On the other hand, the color unevenness correction unit 103 includes LEDs that are not included in the boundary area 00 with the light emission block (i−1, j−1) on the upper left among the color LEDs of the light emission block (i, j) to be corrected. The brightness correction control value is calculated as follows.
That is, the color unevenness correction unit 103 receives the luminance control value BD_G1 (i, j) of the green LED (G1) of the light emission block (i, j) to be corrected, which is input from the local dimming control unit 101, as it is. ) Brightness correction control value D_G1 (i, j).
Further, the color unevenness correction unit 103 directly inputs the luminance control value BD_G2 (i, j) of the green LED (G2) of the light emission block (i, j) to be corrected, which is input from the local dimming control unit 101, as the green LED (G2 ) Brightness correction control value D_G2 (i, j).
Further, the color unevenness correction unit 103 directly uses the luminance control value BD_B (i, j) of the blue LED of the light emitting block (i, j) to be corrected input from the local dimming control unit 101 as it is. Let D_B (i, j).

The formulas for calculating the brightness correction control value when TUL (i, j) is 1 are shown in the following formulas (28) to (31).

D_R (i, j) = α × BD_R (i−1, j−1) + (1−α) × BD_R (i, j) (28)
D_G1 (i, j) = BD_G1 (i, j) (29)
D_G2 (i, j) = BD_G2 (i, j) (30)
D_B (i, j) = BD_B (i, j) (31)

The formulas for calculating the luminance correction control value when TUR (i, j) is 1 are shown in the following formulas (32) to (35).

D_R (i, j) = BD_R (i, j) (32)
D_G1 (i, j) = β × BD_G1 (i−1, j + 1) + (1−β) × BD_G1 (i, j) (33)
D_G2 (i, j) = BD_G2 (i, j) Equation (34)
D_B (i, j) = BD_B (i, j) Equation (35)

The formulas for calculating the luminance correction control value when TDL (i, j) is 1 are shown in the following formulas (36) to (39).

D_R (i, j) = BD_R (i, j) (36)
D_G1 (i, j) = BD_G1 (i, j)... (37)
D_G2 (i, j) = β × BD_G2 (i + 1, j−1) + (1-β) × BD_G2 (i, j) Expression (38)
D_B (i, j) = BD_B (i, j) Equation (39)

The formulas for calculating the luminance correction control value when TDR (i, j) is 1 are shown in the following formulas (40) to (43).

D_R (i, j) = BD_R (i, j) Equation (40)
D_G1 (i, j) = BD_G1 (i, j)... Formula (41)
D_G2 (i, j) = BD_G2 (i, j) (42)
D_B (i, j) = γ × BD_B (i + 1, j + 1) + (1-γ) × BD_B (i, j)... (43)

In step S1721, the color unevenness correction unit 103 determines whether or not the column count value j of the light emission block has reached the maximum value. If j is not the maximum value, the process proceeds to step S1722, and if j is the maximum value, The process proceeds to step S1723.
In step S1722, the color unevenness correction unit 103 increments the column count value j and proceeds to step S1718.
In step S1723, the color unevenness correction unit 103 determines whether or not the row count value i has reached the maximum value. If i is not the maximum value, the process proceeds to step S1724, and if i is the maximum value, the process proceeds to step S1725. .
In step S1724, the color unevenness correction unit 103 increments the row count value i, initializes j to 0, and proceeds to step S1718.

In step S1725, the color unevenness correction unit 103 causes the backlight control unit 104 to perform luminance correction control values D_R (i, j), D_G1 (i, j), D_G2 ( i, j) and D_B (i, j) are output.
In this way, the luminance correction control value for reducing the color unevenness is calculated.

Next, the uneven color correction effect when the uneven color determination process of FIG. 5 and the uneven color correction process of FIG. 7 are performed according to the input image signal will be described with reference to the schematic diagram of FIG.
FIG. 8A is a schematic diagram illustrating an example of the brightness control value (the brightness control value output from the local dimming control unit 101) of each color LED in each light-emitting block before color unevenness correction illustrated in FIG. 6A. It is.

An example of the color unevenness determination value calculated by the color unevenness determination process of FIG. 5 with respect to the luminance control value of each light emitting block of FIG. 8A is shown in the schematic diagram of FIG. Here, the thresholds HRth = 0.2, HGth = 0.2, and HBth = 0.2 in the color unevenness determination process of FIG. In the luminance control value of each light emitting block in FIG. 8A, the luminance control value of the light emitting block (i, j) and the luminance control value of the adjacent light emitting block are greatly different. Accordingly, in FIG. 8B, the color unevenness determination value in the direction adjacent to the light emission block (i, j) is determined to be 1 for all the light emission blocks other than the light emission block (i, j).
FIG. 8C is a diagram schematically showing a region where color unevenness occurs when the LEDs of the respective light-emitting blocks are caused to emit light with the luminance control value of FIG. In FIG. 8C, a region 1802 around the light emission block (i, j) indicates a region where color unevenness occurs.

  FIG. 8D shows a schematic diagram of the brightness correction control value of each color LED in each light emitting block calculated by the color unevenness correction process of FIG. Here, α = 1, β = 1, and γ = 1 in the color unevenness correction process of FIG. In the light emitting blocks determined to cause color unevenness (eight light emitting blocks other than the central light emitting block (i, j)), the luminance control value of the LED in the direction determined to cause color unevenness is corrected. Yes. For example, when focusing on the light emission block (i, j−1), the color unevenness determination value TR = 1 from FIG. 8B, and color unevenness due to light leakage from the light emission block (i, j) adjacent in the right direction. Is determined to occur. Among the LEDs of the light emitting block (i, j-1) of interest, the LEDs included in the boundary region between the light emitting block (i, j) on the right are the green LED (G1) and the blue LED. (B). The brightness control values of these LEDs are 3 and 1 in FIG. 8A, respectively, but are corrected to 6 and 2 respectively in the brightness correction control value of FIG. 8C.

The luminance correction control value of each color LED in the boundary area is (R, G1, G2, B) = (6, 6, 6, 2), and the right adjacent light-emitting block (i, j) The brightness control value (R, G1, G2, B) of each color LED is equal to (6, 6, 6, 2). For this reason, the occurrence of color unevenness in the region on the side close to the right adjacent light emitting block (i, j) in the light emitting block (i, j-1) of interest is suppressed. By causing the LEDs of the respective light emission blocks to emit light based on the brightness correction control value shown in FIG. 8D, the region where the color unevenness as shown in FIG. 8C occurs is eliminated. Therefore, color unevenness in the display area of the display unit 106 corresponding to the nine light-emitting blocks is suppressed, and high-quality display is possible.

The backlight control unit 104 performs backlighting based on the luminance correction control values D_R (i, j), D_G1 (i, j), D_G2 (i, j), and D_B (i, j) input from the color unevenness correction unit 103. A current is supplied to the light unit 105 to cause the LED to emit light.
Next, the backlight unit 105 emits light with a current value corresponding to the luminance correction control value determined for each light emission block output from the backlight control unit 104.
Next, the display unit 106 performs display based on the input image signal. At this time, the image signal input to the display unit 106 is a corrected image signal corrected by the image processing unit 107 in accordance with the luminance correction control value for each light emitting block and each light source calculated by the color unevenness correcting unit 103. It is.

  As described above, the image display apparatus according to the present embodiment determines whether or not color unevenness occurs for each light emitting block from the luminance control value for each light emitting block, and determines the direction in which the color unevenness occurs. . In the light emission block that is determined to cause color unevenness, the luminance control value of the LED in the direction in which the color unevenness is generated is corrected so that the color unevenness is reduced. As a result, in an image display device that performs local dimming control, it is possible to reduce the occurrence of color unevenness in the vicinity of the boundary between light emitting blocks having a luminance difference.

  The above-described example is an example of an embodiment of the present invention, and various modifications can be added to the above-described example without departing from the scope of the present invention. For example, the number of light sources constituting the light emission block is not limited to four. Further, the number of colors of the light source is not limited to the three colors in the above embodiment, such as four colors including white and yellow, and five colors. When three primary color light sources are used, each color light source may be one. In addition, the arrangement of the light sources in the light emitting block is not limited to 2 horizontal x 2 vertical, but may be triangular or rhombus-shaped.

101: Local dimming control unit, 102: Color unevenness determination unit, 103: Color unevenness correction unit, 104: Backlight control unit, 105: Backlight unit

Claims (7)

A backlight that is divided by a plurality of light-emitting blocks that can independently control light emission, and each light-emitting block is provided with a plurality of light sources of a plurality of light-emitting colors,
A local dimming control unit that determines luminance for each light-emitting block and light source according to an input image signal;
For each light-emitting block, based on the luminance determined by the local dimming control unit, it is determined whether or not color unevenness that is a change in color caused by light leakage from an adjacent light-emitting block occurs, and color unevenness A color unevenness determination unit that determines which light emission block of a plurality of adjacent light emission blocks generates color unevenness with respect to the light emission block determined to generate
Among a plurality of light sources of light emitting blocks determined to cause color unevenness, a predetermined part arranged at a position close to a boundary with an adjacent light emitting block determined to generate color unevenness for the light emitting block A color unevenness correction unit that corrects luminance with the light source of
A backlight control unit that emits light at a luminance corrected by the color unevenness correction unit for the light source to be corrected, and a light source other than the light source to be corrected at a luminance determined by the local dimming control unit;
A backlight device comprising:   The color unevenness correction unit includes a predetermined part of the light source to be corrected and a position close to the boundary among a plurality of light sources of the adjacent light-emitting blocks determined to generate color unevenness. And correcting the luminance of the light source to be corrected so as to bring the color of a predetermined boundary region including the light source closer to the color of the adjacent light-emitting block determined to cause color unevenness. The backlight device according to claim 1.   The color unevenness correction unit determines a ratio of the luminance of the light source of each color included in the boundary region to the luminance of the boundary region, and the adjacent light emitting block with respect to the luminance of the adjacent light emitting block determined to cause color unevenness. The backlight device according to claim 2, wherein the luminance of the light source to be corrected is corrected so as to approach the luminance ratio of the light sources of the respective colors.   The color unevenness correction unit is a position where each of the light sources to be corrected is arranged in the light emitting block determined to generate the color unevenness among the light sources of the adjacent light emitting blocks determined to generate the color unevenness. A correction value for each luminance of the light source to be corrected is calculated by weighted addition of the luminance of the light source arranged at a position corresponding to the above and the luminance of each light source to be corrected. 4. The backlight device according to any one of 3.   The color unevenness correction unit is a position where each of the light sources to be corrected is arranged in the light emitting block determined to generate the color unevenness among the light sources of the adjacent light emitting blocks determined to generate the color unevenness. The backlight device according to any one of claims 1 to 3, wherein the luminance of the light source arranged at a position corresponding to is a correction value of the luminance of each of the light sources to be corrected.   The color unevenness determination unit is adjacent to the light emitting block adjacent to the determination target light emission block when the luminance is higher than the luminance of the light emission block to be determined whether or not color unevenness occurs. The backlight device according to claim 1, wherein the light-emitting block is determined to cause color unevenness in the light-emitting block to be determined. A method of controlling a backlight device including a backlight that is divided by a plurality of light emitting blocks capable of independently controlling light emission, and each light emitting block is provided with a plurality of light sources of a plurality of light emitting colors,
A local dimming control step for determining luminance for each light-emitting block and each light source according to an input image signal;
For each light-emitting block, based on the luminance determined by the local dimming control step, it is determined whether or not color unevenness that is a color change caused by light leakage from an adjacent light-emitting block occurs, and color unevenness Color unevenness determination step for determining which light-emitting block among the plurality of adjacent light-emitting blocks generates color unevenness,
Among a plurality of light sources of light emitting blocks determined to cause color unevenness, correction is performed on a predetermined part of the light sources arranged near the boundary between adjacent light emitting blocks determined to generate color unevenness Color unevenness correction process for correcting the brightness as,
A backlight control step of causing the light source to be corrected to emit light at a luminance corrected by the color unevenness correction step, and a light source other than the light source to be corrected to emit light at a luminance determined by the local dimming control step;
Have
The color unevenness correcting step includes a predetermined part of the light source to be corrected and a position close to the boundary among a plurality of light sources of the adjacent light-emitting blocks determined to generate color unevenness. And correcting the luminance of the light source to be corrected so as to bring the color of a predetermined boundary region including the light source closer to the color of the adjacent light-emitting block determined to cause color unevenness. Method for controlling the backlight device.

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