Method for controlling backlight of display device and display device

Abstract

To reduce power consumption of a display device.SOLUTION: In a display device including a display panel and backlight, a method for controlling the backlight is disclosed. The backlight includes a plurality of backlight blocks. The method determines a provisional luminance value for each of the plurality of backlight blocks according to an input video frame. Then, the method corrects each provisional luminance value by a sum total of the provisional luminance values and a reduction amount based on each provisional luminance value.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to controlling the backlight of a display device. [Background technology]

[0002] In order to reduce the power consumption of the backlight of an LCD display device and improve the contrast ratio, local dimming technology is used, in which the light-emitting surface of the backlight is divided into multiple blocks and the light intensity of each block is individually increased or decreased depending on the brightness within the video frame.

[0003] For example, when a white window is displayed on an all-black background, local dimming technology increases the lighting level (brightness) of the backlight area (block) facing the area where white is displayed, and reduces the light emission level of the backlight area (block) in the background (black) part.

[0004] This control reduces the power consumption of the backlight compared to when the entire backlight area is always lit at 100%, and further increases the difference in brightness between areas with low and high backlight emission, thereby increasing the contrast ratio within the same plane and improving display quality. Examples of local dimming technology are disclosed in Patent Document 1 and Patent Document 2, for example. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent Application Publication No. 2014 / 0002335 [Patent Document 2] U.S. Patent Application Publication No. 2014 / 0232760 Summary of the Invention [Problem to be solved by the invention]

[0006] In local dimming, when a bright image is input across the entire screen, each of the divided blocks will contain high-gradation pixels, resulting in 100% light emission for each block, making it impossible to achieve a reduction in backlight power consumption. [Means for solving the problem]

[0007] One aspect of the present disclosure is a method for controlling a backlight in a display device including a display panel and a backlight, the backlight including multiple backlight blocks, the method including: determining a provisional luminance value for each of the multiple backlight blocks in response to an input video frame; and correcting each of the provisional luminance values ​​by a reduction amount based on the sum of the provisional luminance values ​​and each of the provisional luminance values.

[0008] A display device according to one aspect of the present disclosure includes a display panel, a backlight disposed on a rear side of the display panel and including multiple backlight blocks, and a control device that controls the luminance values ​​of the multiple backlight blocks and the transmission of light from the backlight through the display panel. The control device determines a provisional luminance value for each of the multiple backlight blocks according to an input video frame, and corrects each of the provisional luminance values ​​by a reduction amount based on the sum of the provisional luminance values ​​and each of the provisional luminance values. [Effects of the Invention]

[0009] According to one aspect of the present disclosure, the power consumption of a display device can be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] 1 illustrates an example of the configuration of a display device according to an embodiment of the present specification. [Figure 2] 2 shows a schematic diagram of an example of the functional configuration of a video signal processing circuit. [Figure 3] 10A and 10B are diagrams illustrating an outline of a method for correcting a provisional luminance value by a backlight luminance control unit. [Figure 4A]10 shows an example of the luminance distribution of pixels in a display area of ​​a liquid crystal display panel according to an input video frame. [Figure 4B] 4B shows a provisional luminance distribution of the backlight, corresponding to the display area luminance distribution of the display area of ​​FIG. 4A. [Figure 5] An example of a method for correcting the provisional luminance value distribution of the backlight shown in FIG. 4B will be described. [Figure 6A] 10 shows another example of the luminance distribution of pixels in the display area of ​​the liquid crystal display panel 20 according to an input video frame. [Figure 6B] 6B shows a provisional luminance distribution of the backlight, corresponding to the display area luminance distribution of the display area of ​​FIG. 6A. [Figure 7] An example of a method for correcting the provisional luminance value distribution of the backlight 30 shown in FIG. 6B will be described. [Figure 8A] 10 shows another example of the luminance distribution of pixels in the display area of ​​the liquid crystal display panel according to an input video frame. [Figure 8B] 8B shows a provisional luminance distribution of the backlight, corresponding to the display area luminance distribution of the display area of ​​FIG. 8A. [Figure 9] An example of a method for correcting the provisional luminance value distribution of the backlight shown in FIG. 8B will be described. [Figure 10A] 10 shows another example of the luminance distribution of pixels in the display area of ​​the liquid crystal display panel according to an input video frame. [Figure 10B] 10B shows a provisional luminance distribution of the backlight, corresponding to the display area luminance distribution of the display area of ​​FIG. 10A. [Figure 11] An example of a method for correcting the provisional luminance value distribution of the backlight shown in FIG. 10B will be described. [Figure 12] The correction of the backlight provisional luminance value distribution in the configuration where the parameter A is set to 1.05 and the multiplying factor function is set as described above is shown. [Figure 13] 1 illustrates an example of the configuration of a display device according to an embodiment of the present specification. [Figure 14] 10 shows an example of an image displayed on a liquid crystal display panel and a corresponding provisional luminance value distribution of the backlight. [Figure 15A]10 shows an example of the configuration of a luminance management table held by the video signal processing circuit. [Figure 15B] 10 shows an example of the configuration of a luminance management table held by the video signal processing circuit. [Figure 15C] 10 shows an example of the configuration of a luminance management table held by the video signal processing circuit. [Figure 15D] 10 shows an example of the configuration of a luminance management table held by the video signal processing circuit. [Figure 16A] 10 shows the brightness management table updated based on the communication results of the video signal processing circuit. [Figure 16B] 10 shows the brightness management table updated based on the communication results of the video signal processing circuit. [Figure 16C] 10 shows the brightness management table updated based on the communication results of the video signal processing circuit. [Figure 16D] 10 shows the brightness management table updated based on the communication results of the video signal processing circuit. [Figure 17] 10 shows the luminance value distribution of the backlight block after correction. [Figure 18] 10 shows an example of an image displayed on a liquid crystal display panel and a corresponding provisional luminance value distribution of the backlight. [Figure 19A] 10 shows an example of the configuration of a luminance management table held by the video signal processing circuit. [Figure 19B] 10 shows an example of the configuration of a luminance management table held by the video signal processing circuit. [Figure 20] 10 shows the brightness management table updated based on the communication results of the video signal processing circuit. [Figure 21] 10 shows the luminance value distribution of the backlight block after correction. [Figure 22] 10 shows an example of data communicated between video signal processing circuits. [Figure 23] 10 shows examples of waveforms of a clock signal SCK, a data signal SDA, and a control signal CS. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that this embodiment is merely an example for realizing the present disclosure and does not limit the technical scope of the present disclosure. The same reference numerals are used to designate common components in each drawing. For clarity of explanation, the dimensions and shapes of the illustrated objects may be exaggerated.

[0012] A display device according to an embodiment of the present specification disclosed below includes a backlight including multiple backlight blocks and a display panel. The display device determines a provisional brightness value for each backlight block based on an input video frame. Furthermore, the display device determines and corrects a reduction amount for each provisional brightness value based on the sum of the provisional brightness values ​​and each provisional brightness value. A configuration according to an embodiment of the present specification can reduce the power consumption of the backlight while suppressing discomfort felt by viewers of the video. The embodiment of the present specification will be described in more detail below.

[0013] <Embodiment 1> FIG. 1 shows an example of the configuration of a display device according to an embodiment of the present specification. The display device displays an image by controlling the amount of light transmitted from a backlight. FIG. 1 shows an example of the configuration of a liquid crystal display device 1 as an example of a display device. The liquid crystal display device 1 includes a signal processing board 10, a power supply source 13, a video signal supply source 14, a liquid crystal display panel 20, a display driver 21, and a scan driver 22. The liquid crystal display device 1 further includes a backlight 30, a backlight drive board 31, and a backlight power supply source 32. The signal processing board 10 includes a power generation circuit 11 and a video signal processing circuit 12. For example, the signal processing board 10, the display driver 21, and the scan driver 22 may be connected to each other. 2 is included in a control device that controls the liquid crystal display panel 20.

[0014] The liquid crystal display panel 20 is disposed in front of (on the viewing side of) the backlight 30, and displays video frames (images) sequentially input from outside by controlling the amount of light transmitted from the backlight 30. The power supply generation circuit 11 includes, for example, a DC-DC converter, and generates power for operating other circuits and supplies power to them. The video signal processing circuit 12 performs processing related to video display, such as generating signals for displaying images on the liquid crystal display panel 20 and signals for controlling the backlight 30. The power supply source 13 supplies power to the power supply generation circuit 11. The video signal supply source 14 supplies video signals to the video signal processing circuit 12.

[0015] The power supply generating circuit 11 generates power for driving ICs such as the video signal processing circuit 12, the display driver 21, and the scan driver 22. The display driver 21 and the scan driver 22 are configured to operate using the power supplied from the power supply generating circuit 11 and to perform their respective processes.

[0016] The display driver 21 generates a data signal from the video signal transmitted from the video signal processing circuit 12 and supplies the data signal to the liquid crystal display panel 20. The scan driver 22 sequentially selects scan lines of the liquid crystal display panel 20 in accordance with a timing signal transmitted from the video signal processing circuit 12. The video signal processing circuit 12 also transmits a timing signal to the display driver 21, and the display driver 21 generates a data signal from the received video signal in accordance with the timing signal and supplies the data signal to the liquid crystal display panel 20.

[0017] The video signal processing circuit 12 uses power supplied from the power generation circuit 11 to convert data arrays for transmitting externally input video signals to the display driver 21, and to generate and transmit timing signals for operating the drivers 21 and 22. The video signal processing circuit 12 further generates drive control signals for driving and controlling the multiple backlight blocks included in the backlight 30, and transmits these to the backlight drive board 31. Examples of drive control signals include a backlight ON / OFF control signal and a dimming signal. The dimming signal is a PWM (Pulse Width Modulation) signal for time-division control of the lighting time of the light source, and a signal for controlling the amount of current flowing through the light source.

[0018] The backlight 30 is a planar light source device disposed on the rear side of the liquid crystal display panel 20, and emits light necessary for the liquid crystal display panel 20 to display an image. The backlight drive board 31 includes a backlight drive circuit, and controls the lighting (brightness) of the backlight 30 in response to a drive control signal transmitted from the video signal processing circuit 12. The backlight drive board 31 is powered by a power supply source 32 for the backlight.

[0019] As shown in Figure 1, the liquid crystal display device 1 employs local dimming technology, dividing the backlight 30 into X blocks (regions) along the X axis and Y blocks along the Y axis. The liquid crystal display device 1 can individually control the brightness value (lighting level) of each of the (X x Y) blocks. To reduce power consumption and improve the contrast ratio, the liquid crystal display device 1 individually increases or decreases the lighting level of each block depending on the brightness of the video frame.

[0020] The backlight 30 is, for example, a direct-type backlight, and may include a light source array arranged in the backlight plane so as to face the liquid crystal display panel 20, and a diffusion plate between the light source array and the liquid crystal display panel 20. A typical example of a light source is an LED. A plurality of LEDs may be arranged in blocks. The number of LEDs in one block is arbitrary. An optimal number of LEDs are arranged in optimal positions based on the luminance efficiency and luminance distribution of the LEDs.

[0021] The backlight 30 may be an edge type including a light guide plate and a light source disposed on a side surface, instead of the direct type as described above. The light-emitting region of the backlight 30 may be configured, for example, of blocks arranged in a matrix, or may be configured of blocks arranged in a horizontal or vertical row.

[0022] The video signal processing circuit 12 generates a drive control signal for controlling the brightness of each block of the backlight 30 and transmits it to the backlight drive board 31. The backlight drive board 31 drives and controls the light sources of the backlight 30, such as LEDs, so that the blocks emit light at the brightness values ​​(lighting levels) of the blocks indicated by the drive control signals from the video signal processing circuit 12.

[0023] The video signal processing circuit 12 generates timing signals for the display driver 21 and the scan driver 22 in accordance with the timing signals of the input video signal, and sequentially transmits signals for each video frame (frame signals) in the video signal to the display driver 21. The frame signals indicate, for example, the gradation levels of red (R), green (G), and blue (B) of each pixel in the video frame.

[0024] The video signal processing circuit 12 further analyzes the video frame and, based on the analysis results, generates and transmits a drive control signal to the backlight 30 that illuminates the liquid crystal display panel 20 from behind. As described above, the liquid crystal display device 1 employs local dimming technology. The video signal processing circuit 12 determines a provisional brightness value for each block of the backlight 30 based on the analysis results of the video frame.

[0025] Furthermore, the video signal processing circuit 12 determines the amount of reduction for each provisional luminance value based on the provisional luminance value of the block. The video signal processing circuit 12 corrects the provisional luminance value by each reduction amount and determines the luminance value for each block. In this way, by correcting the provisional luminance values ​​determined based on the video frame so as to decrease them, the power consumption of the backlight 30 can be reduced. Furthermore, by correcting each provisional luminance value determined based on the video frame based on those provisional luminance values, the discomfort felt by the viewer due to the decrease in luminance can be reduced.

[0026] The control of the backlight 30 by the video signal processing circuit 12 will be described in detail below. Fig. 2 schematically shows an example of the functional configuration of the video signal processing circuit 12. The video signal processing circuit 12 includes a display control drive signal generation unit 231, a gradation-to-luminance conversion unit 201, a block luminance value calculation unit 202, a block luminance value arrangement unit 203, a backlight luminance control unit 210, and a backlight drive control signal generation unit 221. The backlight luminance control unit 210 includes a block luminance sum calculation unit 211, a block luminance maximum value calculation unit 212, a multiplying factor coefficient calculation unit 213, and a coefficient multiplication unit 214.

[0027] The display control drive signal generation unit 231 generates signals to be transmitted to the display drive driver 21 and the scan driver 22 from the video signal received from the video signal supply source 14. The display control drive signal generation unit 231 transmits signals of RGB gradation levels of each pixel indicated by the video frame together with timing signals to the display drive driver 21, and transmits the timing signals to the scan driver 22.

[0028] The gradation-to-luminance converter 201, block luminance value calculator 202, and block luminance value array unit 203 are circuits for determining a provisional luminance value (provisional illumination level) for each block of the backlight 30 based on a video frame. Specifically, the gradation-to-luminance converter 201 converts the gradation level of a pixel indicated by a video frame into a relative luminance value. The luminance value of a pixel is the maximum luminance value of the red, blue, and green elements (also called sub-pixels) that make up that pixel.

[0029] The block luminance value calculation unit 202 determines a provisional luminance value for each block of the backlight 30 based on the luminance values ​​of the pixels in the video frame. For example, the block luminance value calculation unit 202 sets the luminance value of the block to a luminance value determined from the maximum luminance value of the pixels in a portion of the display area opposite the block (also called a display area block). To distinguish from the display area blocks, the backlight blocks are sometimes called backlight blocks. The backlight blocks are each associated with the opposite display area block.

[0030] In the following, the luminance value of a pixel and the luminance value of a block are each assumed to be relative luminance values ​​ranging from 0 to 1. The block luminance value calculation unit 202 determines the maximum luminance value of the pixels in the corresponding display area block as the provisional luminance value of the backlight block.

[0031] The block luminance value array unit 203 generates an array of provisional luminance values ​​for each block calculated by the block luminance value calculation unit 202. The array associates the blocks of the backlight 30 with their provisional luminance values. The block luminance value array unit 203 transmits the generated array of provisional luminance values ​​to the backlight luminance control unit 210.

[0032] The backlight luminance control unit 210 corrects each of the received provisional luminance values ​​to determine the luminance value of each block. The backlight luminance control unit 210 determines the amount of reduction from the provisional luminance value of each block based on the provisional luminance value array. The correction method will be described in detail later.

[0033] The backlight drive control signal generation unit 221 acquires the determined luminance value for each block from the backlight luminance control unit 210 and generates a drive control signal corresponding to each luminance value. The backlight drive control signal generation unit 221 generates a drive control signal for a specified luminance value according to, for example, the physical characteristics of the light source included in each block. The backlight drive control signal generation unit 221 transmits the drive control signal for each block to the backlight drive board 31.

[0034] An example of a method for correcting the luminance value of each block of the backlight 30 by the backlight luminance control unit 210 will be described below. The backlight luminance control unit 210 determines the amount of reduction from each provisional luminance value determined according to the video frame, based on each provisional luminance value. The backlight luminance control unit 210 corrects each provisional luminance value by the amount of reduction. This makes it possible to reduce the power consumption of the backlight 30 while minimizing the sense of discomfort felt by the viewer.

[0035] 3 is a diagram illustrating an outline of a method for correcting provisional luminance values ​​by backlight luminance control unit 210. In this example, a multiplying factor of 1 or less is calculated using a predetermined method, and the luminance value of each block is determined based on the product of the multiplying factor and each provisional luminance value. In one example, the multiplying factor is determined based on the sum of the provisional luminance values ​​and the maximum value of the provisional luminance values.

[0036] Graph 301 in FIG. 3 shows an example of a function representing a multiplying factor. The input to the function is the area ratio of the current provisional brightness value to the state in which all blocks are lit at the provisional maximum brightness value. This value is the ratio of the sum of the provisional brightness values ​​to the product of the maximum provisional brightness value and the number of blocks. In other words, it can be obtained by dividing the sum of the provisional brightness values ​​by the product of the maximum provisional brightness value and the number of blocks. The value obtained by subtracting the multiplying factor from 1 represents the reduction rate from the provisional brightness value.

[0037] As shown in Fig. 3, the multiplying factor coefficient decreases as the area ratio increases, that is, the reduction rate of the provisional luminance value increases. In the example shown in Fig. 3, the maximum value of the multiplying factor coefficient is value A, and the minimum value of the multiplying factor coefficient is value B. The maximum value A and the minimum value B are set in advance in the backlight luminance control unit 210. In the example shown in Fig. 3, the multiplying factor coefficient is a linear function, and is a monotonically decreasing function in the strict sense.

[0038] For example, if the input video frame is all white (maximum brightness value for all pixels), the corresponding provisional brightness value distribution 323 of the backlight 30 indicates a brightness value of 1.0 (maximum normalized brightness value) for all blocks. The area ratio of the provisional brightness values ​​of this distribution is 1, which corresponds to point 313 on the graph 301. Therefore, the multiplying coefficient is determined to be the B value of point 313.

[0039] Another example 322 of the provisional brightness value distribution shows a white window with an area ratio of approximately 50% against a black background. The provisional brightness value of the white window block is 1.0, and the provisional brightness values ​​of the other blocks are 0.0. The area ratio for determining the multiplying factor is the area ratio relative to the total area of ​​the blocks with a provisional brightness value of 1.0. In the example of FIG. 3, this area ratio corresponds to point 312. Therefore, the multiplying factor is determined to be the value of point 312, which is greater than the minimum value B and less than the maximum value A.

[0040] Another example 321 of the provisional brightness value distribution shows a white window with an area ratio of about 1% against a black background. The provisional brightness value of the white window block is 1.0, and the provisional brightness values ​​of the other blocks are 0.0. The area ratio for determining the multiplying factor is the area ratio relative to the total area of ​​the blocks with a provisional brightness value of 1.0. In the example of FIG. 3, this area ratio corresponds to point 311. Therefore, the multiplying factor is determined to be the value of point 311, which is greater than the value of point 312 and less than maximum value A. The value of point 311 is close to maximum value A.

[0041] In conventional local dimming driving, when the video frame is all black (minimum brightness of all pixels), the backlight 30 is completely turned off. In other words, the provisional brightness value of each block is 0.0, so the brightness value after multiplication by the coefficient of 1.0 is 0.0, the same as when the backlight is completely turned off, and it can be seen that the driving is as intended. Furthermore, as the white window size becomes infinitely smaller, it shows that the multiplying factor coefficient A approaches the value A = 1.0.

[0042] In the above example, the multiplying factor is expressed as a strictly monotonically decreasing linear function. In other examples, the multiplying factor may be expressed as a nonlinear function or a generally decreasing function. In the example described here, the multiplying factor, i.e., the luminance reduction rate, is common to all blocks, but different reduction rates may be assigned to different blocks.

[0043] The calculation method for the multiplying factor coefficients shown in graph 301 in Fig. 3 will be specifically described below. The maximum value of the provisional brightness values ​​in all blocks of the backlight 30 is represented as MAX. The sum of the provisional brightness values ​​in all blocks of the backlight 30 is represented as SUM. Furthermore, the number of all blocks in the backlight 30 is represented as BL_number.

[0044] The maximum and minimum values ​​of the multiplying factor are represented by values ​​A and B. The area ratio of the current provisional brightness value distribution to all blocks lit at the provisional maximum brightness value is represented by Sq. The area ratio Sq can be expressed by the following formula. Sq=SUM / (MAX*BL_number)

[0045] Furthermore, the relationship between the area ratio Sq and the multiplying factor mult_coef can be expressed by the following formula. mult_coef=Sq*B+(1.0-Sq)*A

[0046] The luminance value of each block is determined by multiplying the provisional luminance value of each block by a multiplying coefficient mult_coef. In the configuration example shown in Fig. 2, a block luminance sum calculation unit 211 calculates the sum SUM of the provisional luminance values ​​of all blocks. A block luminance maximum value calculation unit 212 selects the maximum value MAX from the provisional luminance values ​​of all blocks.

[0047] The multiplying factor calculation unit 213 obtains the sum SUM of the provisional brightness values ​​from the block brightness sum calculation unit 211 and the maximum value MAX of the provisional brightness values ​​from the block brightness maximum value calculation unit 212. The multiplying factor calculation unit 213 calculates the area ratio Sq from these two values ​​according to the above formula, and further calculates the multiplying factor mult_coef from the area ratio Sq and the parameters A and B. The coefficient multiplication unit 214 multiplies the provisional brightness value of each block by the multiplying factor mult_coef to determine the brightness value of each block.

[0048] The maximum value A and minimum value B of the multiplying factor are preset to appropriate values ​​to reduce discomfort felt by the viewer due to the reduction in brightness. According to the inventors' research, if the minimum value B is smaller than 0.7, that is, if the maximum reduction rate is greater than 0.3 (30%), the viewer is more likely to feel discomfort. For example, the maximum value A is set to 1.0. The minimum value B is set to a value equal to or greater than 0.7. From the viewpoint of reducing power consumption, the minimum value B is set to a value less than 1.

[0049] In the above example, the brightness value (MAX*BL_number) when all blocks are lit at the provisional maximum brightness value is used as the reference value for calculating the multiplying factor. preliminary Depending on the brightness value, it is possible to obtain a significant power consumption reduction effect while suppressing discomfort caused by reduced brightness. In another example, the reference value may be a constant, for example, the number of backlight blocks.

[0050] The following describes a specific example of calculating the multiplying factor coefficient according to the above method example and reducing the provisional luminance value of each block of the backlight 30. In the example described below, the maximum multiplying factor value A of the parameters is set to 1.0, and the minimum multiplying factor value B is set to 0.8.

[0051] 4A shows an example of the luminance distribution of pixels in a display area 400 of the liquid crystal display panel 20 according to an input video frame. The display area is made up of 15 × 16 pixels 411. In FIG. 4A, one pixel is indicated by the reference numeral 411 as an example. The pixels 411 are arranged in a matrix. The number in the rectangle representing the pixel 411 indicates the relative luminance value of that pixel.

[0052] As described above, when a pixel is composed of sub-pixels of different colors, the luminance of the pixel is, for example, the maximum luminance of the sub-pixels. Although Figure 4A shows pixel 411 as a rectangle, the shape of the pixel is not limited to a rectangle, and the arrangement layout of the pixel is also arbitrary.

[0053] The display area 400 is made up of a plurality of display area blocks 421. Each display area block 421 faces one block of the backlight 30 and is associated with each other. In Fig. 4A, the display area blocks 421 are indicated by dashed lines, and one of them is designated by reference numeral 421 as an example.

[0054] In the example of Fig. 4A, the display area is composed of 12 display area blocks 421 arranged in a 3 x 4 matrix. In the configuration example of Fig. 4A, one display area block 421 is composed of 20 pixels arranged in a 5 x 4 matrix. In this example, all display area blocks 421 have the same shape and number of pixels, but these may be different.

[0055] 4B shows a provisional luminance distribution of the backlight 30 corresponding to the display area luminance distribution of the display area 400 of FIG. 4A. The backlight 30 is composed of 12 backlight blocks 451 arranged in a 3×4 matrix. B 4, one backlight block is designated by reference numeral 451 as an example.

[0056] (x, y) in the backlight block 451 indicates the coordinates (column, row) of the backlight block 451 in the backlight 30. The number in the center of the backlight block 451 indicates the provisional luminance value of the backlight block 451. The backlight block 451 is a display area 400 421 at the same position in the display area block 421.

[0057] The provisional brightness value of the backlight block 451 is determined based on the brightness value of the opposing display area block 421. In this example, the provisional brightness value of all the backlight blocks 451 is 1.0.

[0058] 5 shows an example of a method for correcting the provisional brightness value distribution of the backlight 30 shown in FIG. 4B. The provisional brightness distribution of the backlight 30 shows a provisional brightness value of 1.0 in all backlight blocks 451. Therefore, the power reduction effect of local dimming based on the video frame is 0%.

[0059] The backlight luminance control unit 210 calculates the multiplying factor coefficient mult_coef as described above. The correction amount is determined so that the power reduction effect due to the correction is large for an image in which the power reduction effect due to the local dimming that determines the provisional luminance value is small (an image in which the sum of the provisional luminance values ​​is large).

[0060] The area ratio Sq in this example is calculated as follows.

[0061] Sq=SUM / (MAX*BL_number)=12 / (1*12)=1.0 Furthermore, the multiplying factor mult_coef is calculated as follows: mult_coef=Sq*B+(1.0-Sq)*A =1.0*0.8+(1.0-1.0)*1.0=0.8 In this way, the value of the multiplying factor coefficient mult_coef in this example is set in advance. Minimum is 0.8.

[0062] The backlight luminance control unit 210 calculates the product of the calculated multiplying factor mult_coef and each provisional luminance value to indicate the corrected luminance value of each backlight block 451. The luminance value of all backlight blocks 451 is 0.8. Therefore, the power reduction effect after correction is -20%.

[0063] In this example, the power reduction effect of local dimming based on the video frame is 0%, which is the minimum value. Therefore, to maximize the power reduction effect due to the correction, the multiplying factor mult_coef is set to the minimum value of 0.8, that is, the reduction rate is set to the maximum value of 0.2. As shown in FIG. 4 A, Figure 4B, The calculation example shown in FIG. 5 corresponds to the state in which ALLWHITE 323 is displayed and point 313 in FIG.

[0064] 6A shows another example of the luminance distribution of pixels in the display area 400 of the liquid crystal display panel 20 according to an input video frame. The luminance value of some pixels is less than 1.0, and some pixels have a luminance value of 0.

[0065] 6B shows the interim luminance distribution of the backlight 30 corresponding to the display area luminance distribution of the display area 400 in FIG. 6A. The interim luminance value of the backlight block 451 is equal to the maximum luminance value of the opposite display area block 421. Some backlight blocks 451 have a interim luminance value of 1.0, while other backlight blocks 451 have a interim luminance value less than 1.0.

[0066] 7 shows an example of a method for correcting the provisional brightness value distribution of the backlight 30 shown in FIG. 6B. In the provisional brightness distribution of the backlight 30, the sum of the provisional brightness values ​​of all backlight blocks 451 is 6.0. If all backlight blocks 451 exhibit a maximum brightness value of 1.0, the sum of the brightness values ​​is 12. Therefore, the power reduction effect of local dimming based on the video frame is -50%.

[0067] The backlight luminance control unit 210 calculates the multiplying factor mult_coef as described above. The correction amount is determined so that the power reduction effect by the correction is large for an image in which the power reduction effect by the local dimming for determining the provisional luminance value is small.

[0068] The area ratio Sq in this example is calculated as follows. Sq=SUM / (MAX*BL_number)=6.0 / (1*12)=0.5 Furthermore, the multiplying factor mult_coef is calculated as follows: mult_coef=Sq*B+(1.0-Sq)*A =0.5*0.8+(1.0-0.5)*1.0=0.9 Thus, the value of the multiplying factor mult_coef in this example is 0.9, which is larger than the value in the above example.

[0069] The backlight luminance control unit 210 calculates the product of the calculated multiplying factor mult_coef and each of the provisional luminance values, and indicates the corrected luminance value of each backlight block 451. The power reduction effect after correction is −55%.

[0070] The power reduction effect of local dimming based on the video frame in this example is -50%, which is greater than 0% in the example described with reference to FIG. 5. Therefore, the multiplying factor mult_coef is determined so that the power reduction effect due to the correction is smaller than that in the example shown in FIG. 5. In other words, the multiplying factor is determined to be 0.9, which is greater than 0.8 in the example of FIG. 5. A, Figure 6B, The calculation example shown in FIG. 7 corresponds to the state in which a white window display (50% area) is displayed on an all-black background and point 312 in FIG.

[0071] 8A shows another example of the brightness distribution of pixels in the display area 400 of the liquid crystal display panel 20 according to an input video frame. Only the display area block 421 at coordinates (2, 3) contains a pixel 411 with a brightness value of 1.0, while all the pixels 411 in the other display area blocks have a brightness value of 0.

[0072] 8B shows the provisional luminance distribution of the backlight 30 corresponding to the display area luminance distribution of the display area 400 in FIG. 8A. The provisional luminance value of the backlight block 451 is equal to the maximum luminance value of the opposite display area block 421. Only the backlight block 451 at coordinates (2, 3) has a provisional luminance value of 1.0, and the provisional luminance values ​​of the other backlight blocks 451 are 0.

[0073] 9 shows an example of a method for correcting the provisional luminance value distribution of the backlight 30 shown in FIG. 8B. In the provisional luminance distribution of the backlight 30, the total of the provisional luminance values ​​of all the backlight blocks 451 is 1.0 is . all When all backlight blocks 451 exhibit a maximum brightness value of 1.0, the total brightness value is 12. Therefore, the power reduction effect of local dimming based on the video frame is −91.7% (−11 / 12%).

[0074] As shown in Figure 8 A, Figure 8B, The calculation example shown in Figure 9 corresponds to the state in Figure 3 where a small white window (1 / 12 = 8.3% of the area) is displayed on an all-black background. A, Figure 8B In Figure 9, the display area blocks and backlight blocks are divided into 12 parts, so even if one block is lit, only 8.3% is achieved. However, if the number of blocks (number of divisions) is increased to, for example, 100 or more divisions, the brightness of each block can be controlled more precisely, so it is possible to light up one block to 1% or less, as shown by point 321.

[0075] The backlight luminance control unit 210 calculates the multiplying factor mult_coef as described above. The correction amount is determined so that the power reduction effect by the correction is large for an image in which the power reduction effect by the local dimming for determining the provisional luminance value is small.

[0076] The area ratio Sq in this example is calculated as follows. Sq=SUM / (MAX*BL_number)=1.0 / (1*12)=0.083 Furthermore, the multiplying factor mult_coef is calculated as follows: mult_coef=Sq*B+(1.0-Sq)*A =0.083*0.8+(1.0-0.083)*1.0 =0.9834 Thus, the value of the multiplying factor mult_coef in this example is 0.9834, which is larger than the value in the two examples above.

[0077] The backlight luminance control unit 210 calculates the product of the calculated multiplying factor mult_coef and each provisional luminance value, and indicates the corrected luminance value of each backlight block 451. The power reduction effect after correction is −91.8%.

[0078] The power reduction effect of local dimming based on the video frame in this example is −91.7%, which is greater than 0% and 50% in the examples described with reference to Figures 5 and 7. Therefore, the multiplying factor mult_coef is determined so that the power reduction effect due to correction is smaller than in the examples shown in Figures 5 and 7. In other words, the multiplying factor is determined to be 0.9834, which is greater than 0.8 and 0.9 in the examples of Figures 5 and 7.

[0079] As explained above, even for display screens where conventional general local dimming drive is difficult to achieve a backlight power reduction effect, by using the drive method of the present invention, it is possible to achieve a backlight power reduction effect while minimizing the discomfort that viewers may experience in terms of image quality due to reduced luminance. Another feature of the present invention is that by linearly changing the multiplying coefficient with respect to the number of backlights turned on, the average rate of change becomes continuous and small, thereby realizing an operation that minimizes discomfort in image quality.

[0080] Furthermore, from the perspective of reducing backlight power consumption, it is possible to consider a method such as always using a fixed multiplying factor of 0.8 (20% reduction), but in this case, the contrast of each divided area on the display surface would uniformly deteriorate.In this invention, the multiplying factor is increased when the white area is small, making it possible to perform local dimming drive without uniformly deteriorating the contrast of the entire display area.

[0081] Below, we will explain another example of a method for determining a provisional brightness value based on a video frame (another example of local dimming). In the example described below, the provisional brightness value is corrected using the same method as above, and the power consumption of the backlight can be reduced while suppressing visual discomfort.

[0082] 10A shows another example of the brightness distribution of pixels in the display area 400 of the liquid crystal display panel 20 according to an input video frame. Only the display area block 421 at coordinates (2, 3) contains a pixel 411 with a brightness value of 1.0, while all the pixels 411 in the other display area blocks have a brightness value of 0.

[0083] 10B shows a provisional luminance distribution of the backlight 30 corresponding to the display area luminance distribution of the display area 400 in FIG. 10A. The provisional luminance value of the backlight block 451 is determined based on the luminance values ​​of the opposing display area block and the display area block adjacent to that display area block in the X-axis direction or the Y-axis direction.

[0084] 10B, the block luminance value calculation unit 202 assigns a coefficient of 0.5 to the display area block adjacent to the opposing display area block along the X-axis or Y-axis. The block luminance value calculation unit 202 determines the maximum luminance value of the opposing display area block and the maximum luminance value of the adjacent display area block multiplied by the coefficient 0.5 as the provisional luminance value of the backlight block 451.

[0085] 10A and 10B, only the display area block 421 at (2,3) includes a pixel 411 with a luminance value of 1.0. Therefore, the provisional luminance value of the backlight block 451 at (2,3) is 1.0. Furthermore, the provisional luminance values ​​of the backlight blocks 451 adjacent to that backlight block 451 along the X-axis or Y-axis are each 0.5. The provisional luminance values ​​of the other backlight blocks 451 are 0.0.

[0086] 11 shows an example of a method for correcting the provisional luminance value distribution of the backlight 30 shown in FIG. 10B. In the provisional luminance distribution of the backlight 30, the total of the provisional luminance values ​​of all the backlight blocks 451 is 3.0. . all When all backlight blocks 451 exhibit a maximum brightness value of 1.0, the total brightness value is 12. Therefore, the power reduction effect due to local dimming based on the video frame is −75.0% (−9 / 12%).

[0087] The backlight luminance control unit 210 calculates the multiplying factor mult_coef as described above. The correction amount is determined so that the power reduction effect by the correction is large for an image in which the power reduction effect by the local dimming for determining the provisional luminance value is small.

[0088] The area ratio Sq in this example is calculated as follows. Sq=SUM / (MAX*BL_number)=3.0 / (1*12)=0.25 Furthermore, the multiplying factor mult_coef is calculated as follows: mult_coef=Sq*B+(1.0-Sq)*A =0.25*0.8+(1.0-0.25)*1.0 =0.95 Thus, the value of the multiplying factor mult_coef in this example is 0.95.

[0089] The backlight luminance control unit 210 calculates the product of the calculated multiplying factor mult_coef and each of the provisional luminance values, and indicates the corrected luminance value of each backlight block 451. The power reduction effect after correction is −76.25%.

[0090] The example described with reference to Fig. 11 shows a larger correction amount (smaller multiplying factor or larger reduction rate) than the correction of the provisional backlight luminance value for the same video frame. In the design of the display device 1, the multiplying factor may be too small. In this example, the parameters A and B for determining the correction amount and the function for determining the multiplying factor are determined to be appropriate values ​​according to the design of the display device 1 and set in the display device.

[0091] For example, the value of parameter A indicating the maximum value of the multiplying factor can be set to a value greater than 1, and the upper limit of the multiplying factor function can be set to 1.0. The multiplying factor function indicates 1.0 when the area ratio is from 0 to a predetermined value, and monotonically decreases from 1.0 to a minimum value B as the area ratio increases from the predetermined value to 1.0. In terms of the reduction rate of the brightness value, the reduction rate is 0 when the area ratio is from 0 to a predetermined value, and increases linearly as the area ratio increases from the predetermined value to the maximum reduction rate.

[0092] 12 shows correction of the provisional backlight luminance value distribution in a configuration in which the parameter A is set to 1.05 and the multiplying factor function is set as described above. The provisional backlight luminance value distribution is the same as the example in FIG.

[0093] The backlight luminance control unit 210 calculates the multiplying factor mult_coef as described above. The correction amount is determined so that the power reduction effect by the correction is large for an image in which the power reduction effect by the local dimming for determining the provisional luminance value is small.

[0094] The area ratio Sq in this example is calculated as follows. Sq=SUM / (MAX*BL_number)=3.0 / (1*12)=0.25 Furthermore, the multiplying factor mult_coef is calculated as follows: mult_coef =min(Sq*B+(1.0-Sq)*A,1.0) =min(0.25*0.8+(1.0-0.25)*1.05,1.0) =0.9875

[0095] Thus, the value of the multiplying factor mult_coef in this example is 0.9875, which is larger than 0.95 in the example described with reference to FIG.

[0096] The backlight luminance control unit 210 calculates the product of the calculated multiplying factor mult_coef and each of the provisional luminance values, and indicates the corrected luminance value of each backlight block 451. The power reduction effect after correction is −75.3%.

[0097] <Other embodiments> Figure 13 shows an example of the configuration of a display device according to an embodiment of the present specification. The following mainly describes the differences from the example configuration shown in Figure 1. The display device 1 includes video signal supply sources 14A-14D and display drivers 21A-21D. The signal processing board 10 includes video signal processing circuits 12A-12D. This configuration can be adopted when the display area has a high resolution that exceeds the resolution that can be driven by a single IC, and multiple ICs are used to drive the display area divided into top, bottom, left, right, etc.

[0098] In such a configuration, if each video signal processing circuit processes only the video data for its assigned area and controls the drive of the backlight block for the corresponding area based only on the brightness information of the assigned area, the brightness of the backlight will vary significantly depending on the area handled by the different video signal processing circuits, resulting in a deterioration in display quality.

[0099] In one embodiment of the present specification, video signal processing devices communicate information about the luminance values ​​of the backlight block groups they are responsible for, and each video signal processing device determines the luminance value of each backlight block it is responsible for based on the luminance values ​​of the backlight blocks of the other video signal processing devices as well as the luminance values ​​of the backlight blocks of the other video signal processing devices, thereby suppressing unnatural luminance differences between the backlight block groups of different video signal processing devices.

[0100] 13, the entire display area of ​​the liquid crystal display panel 20 is divided into four partial display areas 250A to 250D. The video signal processing circuits 12A to 12D perform video display processing, such as generating signals for displaying images in the partial display areas 250A to 250D and signals for controlling the backlight 30.

[0101] That is, for partial display region 250A, video signal processing circuit 12A controls the backlight block facing partial display region 250A. For partial display region 250B, video signal processing circuit 12B controls the backlight block facing display region 250B. For partial display region 250C, video signal processing circuit 12C controls the backlight block facing partial display region 250C. For display region 250D, video signal processing circuit 12D controls the backlight block facing display region 250D.

[0102] The video signal supply sources 14A to 14D supply video signals to the corresponding circuits of the video signal processing circuits 12A to 12D, respectively. The power supply generation circuit 11 generates power supplies for driving ICs such as the video signal processing circuits 12A to 12D and the display drive drivers 21A to 21D. The display drive drivers 21A to 21D generate data signals from the video signals transmitted from the corresponding circuits of the video signal processing circuits 12A to 12D, and supply the data signals to the liquid crystal display panel 20.

[0103] The video signal processing circuit 12A converts the data array for transmitting an externally input video signal to the display driver 21A, and generates and transmits timing signals for operating the drivers 21A and 22. The video signal processing circuit 12A further generates drive control signals for driving and controlling the backlight block facing the display area 250A, and transmits them to the backlight drive board 31.

[0104] The video signal processing circuit 12B converts the data array for transmitting an externally input video signal to the display driver 21B, and generates and transmits a timing signal for operating the driver 21B. The video signal processing circuit 12B further generates a drive control signal for driving and controlling the backlight block facing the display area 250B, and transmits it to the backlight drive board 31.

[0105] The video signal processing circuit 12C performs data array conversion and driver processing for transmitting an externally input video signal to the display driver 21C. 21C The video signal processing circuit 12C further generates and transmits to the backlight driving board 31 a drive control signal for driving and controlling the backlight block facing the display area 250C.

[0106] The video signal processing circuit 12D performs data array conversion and driver processing for transmitting an externally input video signal to the display driver 21D. 21D The video signal processing circuit 12D further generates and transmits to the backlight driving board 31 a drive control signal for driving and controlling the backlight block facing the display area 250D.

[0107] As described above for the video signal processing circuit 12 of the first embodiment, the video signal processing circuits 12A to 12D each control a backlight block to be controlled based on the luminance values ​​of pixels that constitute the corresponding display area in a video frame. Each of the video signal processing circuits 12A to 12D determines a provisional luminance value for each backlight block to be controlled, and further determines a multiplying coefficient and corrects the provisional luminance value with the multiplying coefficient to determine a final luminance value.

[0108] The provisional brightness value and multiplying factor can be determined as in the first embodiment. The multiplying factor is calculated from the maximum value MAX of the provisional brightness values ​​in all blocks and the sum SUM of the provisional brightness values ​​in all blocks of the backlight 30. Therefore, each of the video signal processing circuits 12A to 12D obtains information necessary to obtain these values ​​from one or more other video signal processing circuits. This makes it possible to reduce the discomfort felt by the viewer due to local dimming in a display device controlled by multiple video signal processing circuits.

[0109] 13, four video signal processing circuits control four partial display areas and their corresponding backlight block groups, but the number of these is not particularly limited. In addition, the partial display areas may have different shapes.

[0110] 14 shows an example of an image displayed on the liquid crystal display panel 20 and the corresponding provisional brightness value distribution of the backlight 30. The backlight 30 is made up of backlight block groups 350A to 350B, each of which faces a corresponding area of ​​the partial display areas 250A to 250B. Each of the backlight block groups 350A to 350B is made up of 12 backlight blocks in a 4×3 array.

[0111] The video signal processing circuit 12A controls the upper left backlight block group 350A. The video signal processing circuit 12B controls the upper right backlight block group 350B. The video signal processing circuit 12C controls the lower left backlight block group 350C. The video signal processing circuit 12D controls the lower right backlight block group 350D.

[0112] In the example of FIG. 14, the liquid crystal display panel 20 displays a white area in the upper right corner against a black background. The provisional brightness values ​​of the backlight blocks correspond to the displayed image. Specifically, in the upper left backlight block group 350A, the provisional brightness value of the backlight block in the rightmost column is 1.0, and the provisional brightness values ​​of the other backlight blocks are 1.0. preliminaryThe brightness value is 0. In the upper right backlight block group 350B, the provisional brightness values ​​of all backlight blocks are 1.0.

[0113] In the lower left backlight block group 350C, the provisional brightness value of one backlight block in the right corner is 1.0, and the provisional brightness values ​​of the other backlight blocks are preliminary The brightness value is 0. In the lower right backlight block group 350D, the provisional brightness value of the backlight block in the top row is 1.0, and the brightness values ​​of the other backlight blocks are preliminary The brightness value is 0.

[0114] Each video signal processing circuit can determine the provisional brightness value of each backlight block in the backlight block group it is responsible for from the brightness value of the corresponding partial display area. That is, the video signal processing circuit 12A determines the provisional brightness value of each backlight block of the backlight block group 350A from the brightness value of the pixels in the partial display area 250A shown in the video frame. The method for determining the provisional brightness value is the same as in the first embodiment. For example, the brightness value associated with the maximum brightness value of the opposing pixel is the provisional brightness value of the backlight block.

[0115] Similarly, the video signal processing circuit 12B determines a provisional brightness value for each backlight block of the backlight block group 350B from the brightness values ​​of the pixels in the partial display area 250B indicated by the video frame. The video signal processing circuit 12C determines a provisional brightness value for each backlight block of the backlight block group 350C from the brightness values ​​of the pixels in the partial display area 250C indicated by the video frame. The video signal processing circuit 12D determines a provisional brightness value for each backlight block of the backlight block group 350C from the brightness values ​​of the pixels in the partial display area 250B indicated by the video frame. D From the pixel brightness values, the backlight block group 350 D 2. Determine a provisional brightness value for each backlight block.

[0116] Furthermore, each video signal processing circuit calculates the maximum value MAX of the provisional luminance values ​​for the backlight block group it is responsible for and the sum SUM of the provisional luminance values ​​of all the blocks in the backlight block group, and stores these values ​​in the management table.

[0117] In the configuration example shown in FIG. 14, the video signal processing circuit 12A calculates the maximum provisional luminance value MAX and the provisional luminance value sum SUM as follows. MAX=1.0 SUM=(0.0+0.0+1.0+0.0+0.0+1.0+0.0+0.0 +1.0+0.0+0.0+1.0)=4.0

[0118] The video signal processing circuit 12B calculates the maximum provisional luminance value MAX and the sum of provisional luminance values ​​SUM as follows. MAX=1.0 SUM=(1.0+1.0+1.0+1.0+1.0+1.0+1.0+1.0 +1.0+1.0+1.0+1.0)=12.0

[0119] The video signal processing circuit 12C calculates the maximum provisional luminance value MAX and the sum of provisional luminance values ​​SUM as follows. MAX=1.0 SUM=(0.0+0.0+1.0+0.0+0.0+0.0+0.0+0.0 +0.0+0.0+0.0+0.0)=1.0

[0120] The video signal processing circuit 12D calculates the maximum provisional luminance value MAX and the provisional luminance value sum SUM as follows. MAX=1.0 SUM=(1.0+1.0+1.0+0.0+0.0+0.0+0.0+0.0 +0.0+0.0+0.0+0.0)=3.0

[0121] 15A to 15D are luminance management tables 123A to 123D held by the video signal processing circuits 12A to 12D, respectively. D1 shows an example of the configuration of the brightness management table 123A. The brightness management table 123A stores the MAX and SUM of the provisional brightness values ​​of the backlight block group 350A calculated by the video signal processing circuit 12A. Other values ​​are not input. The brightness management table 123B stores the MAX and SUM of the provisional brightness values ​​of the backlight block group 350B calculated by the video signal processing circuit 12B. Other values ​​are not input.

[0122] The brightness management table 123C stores the MAX and SUM of the provisional brightness values ​​of the backlight block group 350C calculated by the video signal processing circuit 12C. Other values ​​are not input. The brightness management table 123D stores the MAX and SUM of the provisional brightness values ​​of the backlight block group 350D calculated by the video signal processing circuit 12D. Other values ​​are not input.

[0123] Each video signal processing circuit communicates with other video signal processing circuits to receive necessary information in order to obtain values ​​to be input into other items in the brightness management table. An example of communication between video signal processing circuits will be described below.

[0124] The video signal processing circuits 12A and 12C communicate with each other to share information. Fig. 16A shows brightness management tables 123A and 123C updated based on the results of communication between the video signal processing circuits 12A and 12C. The video signal processing circuit 12A receives the MAX and SUM of the backlight block group 350C from the video signal processing circuit 12C and stores them in the brightness management table 123A. The video signal processing circuit 12C receives the MAX and SUM of the backlight block group 350A from the video signal processing circuit 12A and stores them in the brightness management table 123C.

[0125] 16B shows brightness management tables 123B and 123D updated based on the communication results between video signal processing circuits 12B and 12D. Video signal processing circuit 12B receives the MAX and SUM of backlight block group 350D from video signal processing circuit 12D and stores them in brightness management table 123B. Video signal processing circuit 12D receives the MAX and SUM of backlight block group 350B from video signal processing circuit 12B and stores them in brightness management table 123D.

[0126] Next, the video signal processing circuits 12A and 12B communicate with each other to share information. Fig. 16C shows the brightness management tables 123A and 123B updated based on the communication results between the video signal processing circuits 12A and 12B. The video signal processing circuit 12A receives the MAX and SUM of the backlight block groups 350B and 350D from the video signal processing circuit 12B and stores them in the brightness management table 123A. The video signal processing circuit 12B receives the MAX and SUM of the backlight block groups 350A and 350C from the video signal processing circuit 12A and stores them in the brightness management table 123A. B Store in.

[0127] The video signal processing circuits 12C and 12D communicate with each other to share information. FIG. 16D shows brightness management tables 123C and 123D that have been updated based on the results of communication between the video signal processing circuits 12C and 12D. The video signal processing circuit 12C receives the MAX and SUM of the backlight block groups 350B and 350D from the video signal processing circuit 12D and stores them in the brightness management table 123C. The video signal processing circuit 12D receives the MAX and SUM of the backlight block groups 350A and 350C from the video signal processing circuit 12C and stores them in the brightness management table 123C. D Store in.

[0128] Through the communication between the video signal processing circuits, all necessary information can be stored in the brightness management tables of all the video signal processing circuits. Note that the above communication method is merely an example, and as long as each video signal processing circuit can acquire the necessary information, there are no limitations on the pair of video signal processing circuits that communicate and the content of the communication. For example, each video signal processing circuit may communicate with all the other video signal processing circuits to receive the necessary information. Furthermore, as long as each video signal processing circuit can acquire the multiplying factor coefficient, there are no particular limitations on the information that is communicated.

[0129] Each video signal processing circuit may obtain the MAX and SUM calculated by another video signal processing circuit by receiving them directly from that video signal processing circuit, or may obtain them via yet another video signal processing circuit. In the above example, for example, video signal processing circuit 12A obtains the MAX and SUM of backlight block groups 350B and 350C by receiving them from video signal processing circuits 12C and 12C, and obtains the MAX and SUM of backlight block group 350D from video signal processing circuit 12D via video signal processing circuit 12B.

[0130] The video signal processing circuit calculates the multiplying factor mult_coef from the information in the brightness management table and determines the final brightness value (corrected brightness value) for each backlight block to be controlled. The video processing circuit calculates the MAX and SUM of the entire backlight 30 from the MAX and SUM of all backlight block groups 350A to 350D. From these values, the multiplying factor is calculated in the same way as in the first embodiment. The multiplying factor is common to all video signal processing circuits 12A to 12D.

[0131] An example of a method for calculating a multiplying factor will be described. Each video signal processing circuit calculates the sum MAXall of all MAXs indicated in the brightness management table and the sum SUMall of all SUMs. In the example shown in FIGS. 16A to 16D, the sum MAXall of MAXs is 4.0, and the sum SUMall of SUMs is 20.0. The total number BL_number of all backlight blocks in the backlight 30 is 48. Here, as described with reference to FIG. 3, the maximum value A of the multiplying factor is set to 1.0, and the minimum value B of the multiplying factor is set to 0.8.

[0132] The area ratio Sq in this example is calculated as follows. Sq=SUMall / (MAXall*BL_number) =20.0 / (1.0*48)=0.417

[0133] Furthermore, the multiplying factor mult_coef is calculated as follows: mult_coef=0.417*0.8+(1.0-0.417)×1.0 =0.917

[0134] The final brightness value of each backlight block is a value obtained by correcting the provisional brightness value using a multiplying coefficient. Fig. 17 shows the brightness distribution of the backlight blocks after correction. As shown in Fig. 17, since the multiplying coefficient is common, the brightness of the backlight blocks is continuous at the boundary between different backlight block groups. In this way, in a configuration in which multiple video signal processing circuits individually control backlight block groups, this embodiment can suppress the discomfort felt by the viewer due to local dimming.

[0135] Next, an example will be described in which the entire display area of ​​the liquid crystal display panel 20 is divided into two partial display areas. Two video signal supply sources, two display drivers, and two video signal processing circuits are implemented for the two partial display areas.

[0136] 18 shows an example of an image displayed on the liquid crystal display panel 20 and the corresponding provisional luminance value distribution of the backlight 30. The entire display area of ​​the liquid crystal display panel 20 is divided into two partial display areas 270A and 270B. The backlight 30 is made up of backlight block groups 370A and 370B, which respectively correspond to the partial display areas 270A and 270B. A and 270B. 7 0A, 3 7 0B consists of 12 backlight blocks arranged in a 4x3 pattern.

[0137] The video signal processing circuit 120A controls the left backlight block group 370A. The video signal processing circuit 120B controls the right backlight block group 370B. In the example of FIG. 18, the liquid crystal display panel 20 displays a black area on the left side and a white area on the right side. The provisional brightness values ​​of the backlight blocks correspond to the displayed image. Specifically, in the left backlight block group 370A, the provisional brightness value of the backlight block in the rightmost column is 1.0, and the provisional brightness values ​​of the other backlight blocks are 1.0. preliminary The brightness value is 0. In the right backlight block group 370B, the provisional brightness value of all backlight blocks is 1.0.

[0138] Each video signal processing circuit can determine the provisional brightness value of each backlight block in its assigned backlight block group from the brightness value of the corresponding partial display area. That is, video signal processing circuit 120A determines the provisional brightness value of each backlight block in backlight block group 370A from the brightness values ​​of the pixels in partial display area 270A shown in the video frame. The method for determining the provisional brightness value is the same as in the above example, and for example, the brightness value associated with the maximum brightness value of the opposing pixel is the provisional brightness value of the backlight block.

[0139] Similarly, the video signal processing circuit 120B determines the provisional luminance value of each backlight block of the backlight block group 370B from the luminance value of the pixels in the partial display area 270B indicated by the video frame.

[0140] Furthermore, each video signal processing circuit calculates the maximum value MAX of the provisional luminance values ​​for the backlight block group it is responsible for and the sum SUM of the provisional luminance values ​​of all the blocks in the backlight block group, and stores these values ​​in the management table.

[0141] In the configuration example shown in FIG. 18, the video signal processing circuit 120A calculates the maximum provisional luminance value MAX and the provisional luminance value sum SUM as follows. MAX=1.0 SUM=(0.0+0.0+1.0+0.0+0.0+1.0+0.0+0.0 +1.0+0.0+0.0+1.0)=4.0

[0142] The video signal processing circuit 120B calculates the maximum provisional luminance value MAX and the provisional luminance value sum SUM as follows. MAX=1.0 SUM=(1.0+1.0+1.0+1.0+1.0+1.0+1.0+1.0 +1.0+1.0+1.0+1.0)=12.0

[0143] 19A and 19B show configuration examples of brightness management tables 127A and 127B held by the video signal processing circuits 120A and 120B, respectively. The brightness management table 127A stores the MAX and SUM of the provisional brightness values ​​of the backlight block group 370A calculated by the video signal processing circuit 120A. Other values ​​are not input. The brightness management table 127B stores the MAX and SUM of the provisional brightness values ​​of the backlight block group 370B calculated by the video signal processing circuit 120B. Other values ​​are not input.

[0144] Each video signal processing circuit communicates with the other video signal processing circuits to receive necessary information in order to obtain values ​​to be entered into other items in the brightness management table. The video signal processing circuits 120A and 120B communicate with each other to share information. Figure 20 shows brightness management tables 127A and 127B updated based on the communication results of the video signal processing circuits 120A and 120B.

[0145] The video signal processing circuit 12A receives the MAX and SUM of the backlight block group 370B from the video signal processing circuit 120B and stores them in the brightness management table 127A. The video signal processing circuit 120B receives the MAX and SUM of the backlight block group 370A from the video signal processing circuit 120A and stores them in the brightness management table 127B. This communication between the video signal processing circuits allows all necessary information to be stored in the brightness management tables of the two video signal processing circuits.

[0146] The video signal processing circuits 120A, 120B calculate the multiplying factor mult_coef from the information in the brightness management table and determine the final brightness value (corrected brightness value) for each backlight block to be controlled. The video signal processing circuits 120A, 120B calculate the MAX and SUM of the entire backlight 30 from the MAX and SUM of all backlight block groups 370A, 370B. From these values, the multiplying factor is calculated in the same way as in the first embodiment. The multiplying factor is common to all video signal processing circuits 120A, 120B.

[0147] An example of a method for calculating a multiplying factor will be described below. Each video signal processing circuit calculates the sum MAXall of all MAXs indicated in the brightness management table and the sum SUMall of all SUMs. In this example, the sum MAXall of MAXs is 2.0, and the sum SUMall of SUMs is 16.0. The total number BL_number of all backlight blocks in the backlight 30 is 24. Here, as described with reference to FIG. 3, the maximum value A of the multiplying factor is set to 1.0, and the minimum value B of the multiplying factor is set to 0.8.

[0148] The area ratio Sq in this example is calculated as follows. Sq=SUMall / (MAXall*BL_number) =16.0 / (1.0*24)=0.667

[0149] Furthermore, the multiplying factor mult_coef is calculated as follows: mult_coef=0.667*0.8+(1.0-0.667)×1.0 =0.867

[0150] The final brightness value of each backlight block is a value obtained by correcting the provisional brightness value using a multiplying coefficient. Fig. 21 shows the brightness distribution of the backlight blocks after correction. As shown in Fig. 21, since the multiplying coefficient is common, the brightness of the backlight blocks is continuous at the boundary between different backlight block groups. In this way, in a configuration in which multiple video signal processing circuits individually control backlight block groups, this embodiment can suppress the discomfort felt by the viewer due to local dimming.

[0151] Fig. 22 shows an example of data communicated between the video signal processing circuits 120A and 120B. A similar explanation can be applied to the communication between the video signal processing circuits shown in Fig. 13. The video signal processing circuit 120A uses a clock signal SCK1 and a control signal CS1 to send a data signal SDA1 indicating the MAX and SUM of the backlight block group it is responsible for to the video signal processing circuit 120B.

[0152] The video signal processing circuit 120B uses the clock signal SCK2 and the control signal CS2 to transmit one data signal SDA2 indicating the MAX and SUM of the backlight block group it is responsible for to the video signal processing circuit 120A. Note that some signal lines may be shared between the video signal processing circuits 120A and 120B to reduce the number of signal transmission lines.

[0153] Figure 23 shows example waveforms of the clock signal SCK, data signal SDA, and control signal CS. In the example of Figure 23, the data signal SDA transmits MAX=1.0 and SUM=3.0 for the video signal processing circuit. These values ​​are transmitted in 16 bits. Consider a case where MAX has 12-bit resolution and SUM has 30-bit resolution. MAX=1.0 is expressed as 4095. SUM=3.0 is expressed as 4095*3=12285. SUM and MAX can be transmitted with a number of bits that is set in advance taking into account the resolution. The resolution of SUM can be set in advance to the resolution at which MAX*BL_number is maximized.

[0154] As described above, in this embodiment, each video signal processing circuit determines the provisional brightness value of each assigned backlight block based on the video data of the corresponding region of the video frame. Each video signal processing circuit acquires information about the provisional brightness values ​​of other video processing circuits, and determines the multiplying factor (reduction amount) for the assigned backlight block group based on the acquired information and the provisional brightness value of each assigned backlight block. Each video signal processing circuit corrects the provisional brightness value of each assigned backlight block based on the reduction amount.

[0155] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. Those skilled in the art can easily modify, add, or convert each element of the above embodiments within the scope of the present disclosure. It is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. [Explanation of symbols]

[0156] 1 display device, 10 signal processing board, 11 power supply generation circuit, 12, 12A-12D video signal processing circuit, 13 power supply source, 14, 14A-12D video signal supply source, 20 liquid crystal display panel, 30 backlight, 201 gradation-luminance conversion unit, 202 block luminance value calculation unit, 203 block luminance value arrangement unit, 210 backlight luminance control unit, 211 block luminance sum calculation unit, 212 block luminance maximum value calculation unit, 213 multiplication factor coefficient calculation unit, 214 coefficient multiplication unit, 221 backlight drive control signal generation unit, 231 display control drive signal generation unit, 250A-250D partial display area, 323 provisional luminance value distribution, 350A-350D backlight block group, 400 display area, 411 pixel, 421 display area block, 451 backlight block

Claims

1. 1. A method for controlling a backlight in a display device including a display panel and a backlight, comprising: the backlight includes a plurality of backlight blocks; The method comprises: determining a provisional luminance value for each of the plurality of backlight blocks according to an input video frame; determining a reference value based on the maximum luminance value among the provisional luminance values ​​and the number of the plurality of backlight blocks; determining a brightness reduction rate common to the plurality of backlight blocks based on a ratio between the sum of the provisional brightness values ​​and the reference value; correcting the provisional luminance value by a reduction amount based on the luminance reduction rate and the provisional luminance value; method.

2. A method according to claim 1, The relationship between the luminance reduction rate and the sum of the provisional luminance values ​​can be expressed by a linearly changing function. method.

3. A method according to claim 1, The maximum luminance reduction rate from the provisional luminance value is 0.3 or less. method.

4. The method of claim 1, The luminance reduction rate is 0 when the value of the ratio is between 0 and a predetermined value, and increases linearly from the predetermined value to a maximum luminance reduction rate as the value of the ratio increases. method.

5. The method of claim 1, correcting each of the provisional luminance values ​​so that the sum of the reduction amounts increases as the sum of the provisional luminance values ​​increases; method.

6. A display device, A display panel; a backlight disposed on the rear side of the display panel and including a plurality of backlight blocks; a control device for controlling the luminance values ​​of the plurality of backlight blocks and the transmitted light of the light from the backlight through the display panel; Including, The control device determining a provisional luminance value for each of the plurality of backlight blocks according to an input video frame; determining a reference value based on the maximum luminance value among the provisional luminance values ​​and the number of the plurality of backlight blocks; determining a brightness reduction rate common to the plurality of backlight blocks based on a ratio between the sum of the provisional brightness values ​​and the reference value; correcting the provisional luminance value by a reduction amount based on the luminance reduction rate and the provisional luminance value; Display device.

7. The display device according to claim 6, The control device a plurality of processing circuits; Each of the plurality of processing circuits comprises: controlling a responsible partial area of ​​the display panel and a responsible backlight block group facing the responsible partial area; determining the provisional luminance value of each backlight block of the group of backlight blocks in charge based on video data of a corresponding region of the video frame; Calculating the maximum luminance value among the provisional luminance values ​​of the assigned partial region and the sum of the provisional luminance values; obtaining a maximum luminance value and a sum of the provisional luminance values ​​of the partial area assigned to the other processing circuit; determining a maximum luminance value of the display panel from the maximum luminance value of the assigned partial region and the maximum luminance value of the assigned partial region of the other processing circuit; determining a sum of the provisional luminance values ​​of the display panel from a sum of the provisional luminance values ​​of the assigned partial area and a sum of the provisional luminance values ​​of the assigned partial area of ​​the other processing circuit; determining a reference value based on a maximum luminance value of the display panel and the number of the plurality of backlight blocks; determining a luminance reduction rate common to the plurality of backlight blocks based on a ratio between the sum of the provisional luminance values ​​of the display panel and the reference value; correcting the provisional luminance value of the assigned partial region by a reduction amount based on the luminance reduction rate and the provisional luminance value of the assigned partial region; Display device.

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