Brightness compensation method

Abstract

A brightness compensation method includes determining a velocity of an object according to a pulse width modulation table of a current frame and a pulse width modulation table of a previous frame; generating a new pulse width modulation table according to the speed and the pulse width modulation table of the current frame; and performing brightness compensation according to the pulse width modulation table of the current frame and the new pulse width modulation table.

Description

TECHNICAL FIELD

[0001] The present application relates to local dimming, and in particular, to a brightness compensation method and system. BACKGROUND

[0002] Local dimming is a technology implemented in Light Emitting Diode (LED) TVs that improves contrast in dark scenes by dimming the backlight of specific areas of the screen. Local dimming enables dark parts of an image to appear darker, while bright parts of the image remain bright, thereby enhancing contrast and improving overall image quality.

[0003] Local dimming backlight technology is a direct-lit architecture, with LEDs located directly behind the Liquid-Crystal Display (LCD) panel. Each LED or LED region can be dimmed individually to illuminate the pixels required by the display. When an object moves across the LCD panel, it is important to maintain consistent brightness of the object, otherwise, brightness variations can cause flicker. However, due to the architecture, if the background environment of the moving object is dark or even black, the brightness uniformity of the moving object can be insufficient and cause flicker. SUMMARY

[0004] One embodiment of the present application provides a brightness compensation method. The method includes determining a speed of an object according to a pulse width modulation table of a current frame and a pulse width modulation table of a previous frame; generating a new pulse width modulation table according to the speed and the pulse width modulation table of the current frame; and performing brightness compensation according to the pulse width modulation table of the current frame and the new pulse width modulation table.

[0005] Another embodiment of the present application provides a brightness compensation system, including a gray scale to brightness module, a backlight brightness calculation module, a brightness compensation module, and a backlight module. The backlight brightness calculation module is coupled to the gray scale to brightness module, and is configured to determine a speed of an object according to a pulse width modulation table of a current frame and a pulse width modulation table of a previous frame, and to generate a new pulse width modulation table according to the speed and the pulse width modulation table of the current frame. The brightness compensation module is coupled to the backlight brightness calculation module, and is configured to perform brightness compensation according to the pulse width modulation table of the current frame and the new pulse width modulation table. The backlight module is coupled to the brightness compensation module. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 FIG. 1 is a schematic diagram of a brightness compensation system according to one embodiment of the present application.

[0007] Figure 2 FIG. 2 is a flowchart of a brightness compensation method implemented by the brightness compensation system of FIG. 1. Figure 1 FIG. 2 is a flowchart of a brightness compensation method implemented by the brightness compensation system of FIG. 1.

[0008] Figure 3 Fig. 2 is a flowchart of the steps of the brightness compensation method of Fig. 1. Figure 2 Fig. 3 is a flowchart of the step S206 of the brightness compensation method of Fig. 1.

[0009] Figure 4 Fig. 4 is a schematic diagram for determining the object motion speed.

[0010] Figure 5 Fig. 5 is a schematic diagram for generating a new pulse width modulation table.

[0011] Figure 6 Fig. 6 is a schematic diagram for determining the higher coefficient.

[0012] Figure 7 Fig. 7 is a flowchart of another brightness compensation method implemented by the brightness compensation system of Fig. 1. Figure 1

[0013] In the drawings:

[0014] 100, 700: brightness compensation system

[0015] 102: gray scale to brightness module

[0016] 104: backlight brightness calculation module

[0017] 106: brightness compensation module

[0018] 108: backlight module

[0019] 200: brightness compensation method

[0020] S202-S206, S302-S312, S702-S708: steps

[0021] v1, v2, v3: arrow

[0022] T1, T2, T3: pulse width modulation table

[0023] P1, P2: position

[0024] L1, L2, L3, L4, L5, L6: coefficient

[0025] W1: weight matrix

[0026] Rg1, Rg2, Rg3: compensation rangeDETAILED DESCRIPTION

[0027] Figure 1 ​FIG. 1 is a schematic diagram of a brightness compensation system 100 according to an embodiment of the present application. The brightness compensation system 100 can be implemented in a display. The brightness compensation system 100 includes a gray scale to brightness module 102, a backlight brightness calculation module 104, a brightness compensation module 106, and a backlight module 108. The gray scale to brightness module 102 can receive input image data in gray scale and convert the gray scale information to brightness. The image data includes a plurality of frames, and the backlight brightness calculation module 104 can generate a pulse width modulation (PWM) table corresponding to a frame according to the input image data. Then, the brightness compensation module 106 can perform brightness compensation according to the PWM table.

[0028] Figure 2 FIG. 2 is a flowchart of a brightness compensation method 200 implemented by the brightness compensation system 100 of FIG. 1. The brightness compensation method 200 includes steps S202 to S206. Any reasonable modification or adjustment of the steps is within the scope of the present application. Figure 1

[0029] Step S202: receiving input image data in gray scale and converting the gray scale to brightness.

[0030] Step S204: generating a pulse width modulation table.

[0031] Step S206: performing brightness compensation.

[0032] In step S202, the gray scale to brightness module 102 can receive input image data in gray scale and convert the gray scale to brightness. For example, the gray scale of a pixel is (R, G, B), and the brightness can be Max(R, G, B), i.e., the maximum value among R, G, and B, but is not limited thereto.

[0033] A frame (specifically, a backlight module of a display) can be divided into a plurality of blocks. For example, the frame can be divided into M*N blocks, where M and N are positive integers. In step S204, the backlight brightness calculation module 104 can generate an M*N pulse width modulation table corresponding to a current frame in the input image data and an M*N pulse width modulation table corresponding to a previous frame. Each coefficient in the pulse width modulation table corresponds to a block of the frame and can be generated according to information of the corresponding block by a local dimming algorithm.

[0034] In step S206, the brightness compensation module 106 can perform brightness compensation according to the pulse width modulation table. Figure 3 FIG. 3 is a flowchart of step S206 of the brightness compensation method 200 of FIG. 2. Step S206 includes steps S302 to S312. Any reasonable modification or adjustment of the steps is within the scope of the present application. Figure 2 Step S302: receiving a pulse width modulation table corresponding to a current frame and a pulse width modulation table corresponding to a previous frame.Step S304: determining a brightness compensation value corresponding to a block of the current frame according to the pulse width modulation table corresponding to the current frame and the pulse width modulation table corresponding to the previous frame. Step S306: determining a brightness compensation value corresponding to the block of the current frame according to the brightness compensation value corresponding to the block of the current frame and a brightness compensation value corresponding to the block of the previous frame. Step S308: determining a brightness compensation value corresponding to the block of the current frame according to the brightness compensation value corresponding to the block of the current frame and a brightness compensation value corresponding to the block of the previous frame. Step S310: determining a brightness compensation value corresponding to the block of the current frame according to the brightness compensation value corresponding to the block of the current frame and a brightness compensation value corresponding to the block of the previous frame. Step S312: performing brightness compensation according to the brightness compensation value corresponding to the block of the current frame.

[0035] Steps S302 to S312 are as follows:

[0036] Step S302: Is the object moving? If yes, proceed to step S304; if no, end.

[0037] Step S304: Determine the speed of the object.

[0038] Step S306: Generate a new pulse width modulation table.

[0039] Step S308: Determine the higher coefficient between the coefficient in the pulse width modulation table of the current frame and the corresponding coefficient in the new pulse width modulation table.

[0040] Step S310: Determine the dimming speed of the block.

[0041] Step S312: Perform brightness compensation.

[0042] In step S302, it is determined whether the object is moving according to the pulse width modulation table of the current frame and the pulse width modulation table of the previous frame. The object can be an image. If the coefficients in the pulse width modulation table of the current frame are different from the corresponding coefficients in the pulse width modulation table of the previous frame, it indicates that there is an object moving on the panel, and the object is determined to be a moving object. If each coefficient in the pulse width modulation table of the current frame is the same as the corresponding coefficient in the pulse width modulation table of the previous frame, it indicates that the object is stationary. When the object is stationary, steps S304 to S312 can be omitted, and brightness compensation can be omitted to avoid halos.

[0043] After determining that the object is a moving object, in step S304, the speed of the object is determined according to the pulse width modulation table of the current frame and the pulse width modulation table of the previous frame. One frame (specifically, the backlight module of one display) can be divided into multiple regions. For example, the frame can be divided into J*K regions, where J and K are positive integers. The position of the moving object can be determined according to the regions in which the coefficients in the pulse width modulation table are different, and the speed of the moving object can be determined according to the position of the moving object. Please refer to Figure 4 , Figure 4 A schematic diagram for determining the speed of the object is shown. As shown in Figure 4 , the frame is divided into 21*15 blocks and 7*5 regions; each region contains 3*3 blocks. Each region can be represented in the form of (C, R), where C represents the column and R represents the row. Figure 4In the example shown in FIG. 4, the object in the previous frame is located in region (4,3). When the object moves to region (5,3) in the current frame, the coefficients in region (4,3) and region (5,3) of the pulse width modulation table of the current frame can be different from the corresponding coefficients in the pulse width modulation table of the previous frame. The velocity of the moving object is determined according to the location of the object in the previous frame and the location of the object in the current frame. According to the distance between a region and the location of the object in the previous frame, the regions can be classified into several categories, and the velocity of the object can be determined according to the category of the region in which the object is located in the current frame.

[0044] For example, assume that the location of the object in the previous frame is (C, R) and the location of the object in the current frame is (C', R'). If |C'-C| = 0 and |R'-R| < 1, or |C'-C| < 1 and |R'-R| = 0, then the object is located in a first category region and has a first velocity. As shown in FIG. 5, if the object in the previous frame is located in region (4,3) and the object moves to region (5,3) in the current frame, as indicated by arrow vl, since |4-5| < 1 and |3-3| = 0, the object is located in a first category region and has a first velocity. Similarly, if the object moves to (4,2), (3,3), or (4,4), the object is located in a first category region and has a first velocity. Figure 4 Figure 4 As shown in FIG. 6, if the object in the previous frame is located in region (4,3) and the object moves to (5,2) in the current frame, as indicated by arrow v2. Since |4-5| = 1 and |3-2| = 1, the object is located in a second category region and has a second velocity. Similarly, if the object moves to (3,2), (3,4), or (5,4), the object is located in a second category region and has a second velocity. Figure 4 ​As shown, if the object in the previous frame is located in the area (4,3), and the object moves to (6,4) in the current frame, as shown by arrow v3. Since |4-6|=2 and |3-4|=1, the object is located in the third category area and has the third speed. Similarly, if the object moves to (3,1), (5,1), (2,2), (6,2), (2,4), (3,5) or (5,5), the object is located in the third category area and has the third speed. Since the farther the object moves means the faster the object moves, the first speed is less than the second speed, and the second speed is less than the third speed. In this embodiment, the first speed can be considered as a low speed, the second speed can be considered as a medium speed, and the third speed can be considered as a high speed. By dividing the area into multiple categories and judging the speed of the object according to the category, the speed of the object can be defined. This embodiment uses Figure 4 This is described as an example. However, the definition and number of area categories are not limited thereto. In other embodiments, the areas can be divided into more categories and correspond to different speeds.

[0045] In step S306, a new pulse width modulation table is generated according to the object speed, the pulse width modulation table of the current frame and the weight matrix. According to the speed of the object determined in step S304, the compensation range can be determined in the weight matrix. Figure 5 , Figure 5 Schematic diagram of generating a new pulse width modulation table. Pulse width modulation table T1 is a region in the pulse width modulation table for the current frame. The coefficients in this region differ from the corresponding coefficients in the pulse width modulation table for the previous frame. W1 is the weight matrix corresponding to this region. Based on the speed of the object determined in step S304, a compensation range can be determined in weight matrix W1. The larger the compensation range, the higher the corresponding object speed. For example, if the object's speed is determined to be low, the compensation range corresponding to this speed can be a small compensation range Rg1. If the object's speed is determined to be medium, the compensation range corresponding to this speed can be a medium compensation range Rg2. If the object's speed is determined to be high, the compensation range corresponding to this speed can be a large compensation range Rg3. This embodiment uses small, medium, and large compensation ranges as examples, but the present invention is not limited thereto. In other embodiments, more different compensation ranges can be used depending on the speed. After determining the compensation range, the coefficients in the pulse width modulation table of the current frame are multiplied by the corresponding coefficients in the weight matrix within the compensation range, and then divided by the sum of the coefficients in the weight matrix within the compensation range to generate a new pulse width modulation table. Figure 5 For example, assuming that the speed of the object is judged to be low speed, the compensation range corresponding to the speed is the small compensation range Rg1, such as Figure 5As shown, the small compensation range Rg1 is overlapped with the pulse width modulation table T1. When the small compensation range Rg1 is located at the position P1, the center coefficient is the coefficient L1, the pulse width modulation table T2 is the region in the new pulse width modulation table corresponding to the pulse width modulation table T1, and the coefficient in the pulse width modulation table T2 corresponding to the coefficient L1 is the coefficient L3. The calculation of the coefficient in the new pulse width modulation table is to sum the product of the coefficient in the pulse width modulation table of the current frame and the corresponding coefficient in the weight matrix in the compensation range, and then divide the sum by the sum of the coefficients in the weight matrix in the compensation range. For example, the coefficient L3 is (41*0+41*0+41*0+41*0+192*0+41*0+41*0+41*0+41*255) / weight sum. The weight sum is the sum of the coefficients in the weight matrix in the compensation range. For example, the weight sum of the small compensation range Rg1 is 41+41+41+41+192+41+41+41+41=520. Therefore, the coefficient L3 is (41*0+41*0+41*0+41*0+192*0+41*0+41*0+41*0+41*255) / 520, which is 20 after rounding down. The coefficients in the new pulse width modulation table can be calculated by sliding the compensation range to change the center, for example, when the small compensation range Rg1 is slid to the position P2, the center coefficient is the coefficient L2. The coefficient in the pulse width modulation table T2 corresponding to the coefficient L2 is the coefficient L4. The coefficient L4 is (41*0+41*0+41*0+41*255+192*180+41*0+41*0+41*0+41*0) / 520, which is 86 after rounding down. The coefficients in the pulse width modulation table T2 can be calculated by similar calculation. If each coefficient in a region in the pulse width modulation table of the current frame is the same as the corresponding coefficient in the pulse width modulation table of the previous frame, the corresponding region in the new pulse width modulation table can be the same as the region in the pulse width modulation table of the current frame. The new pulse width modulation table can be generated by step S306.

[0046] In step S308, the coefficients in the pulse width modulation table of the current frame are compared with the corresponding coefficients in the new pulse width modulation table to obtain the higher coefficients. And in step S312, the luminance compensation is performed according to the higher coefficients between the coefficients in the pulse width modulation table of the current frame and the corresponding coefficients in the new pulse width modulation table. Please refer to Figure 6 , Figure 6 The diagram for determining the higher coefficients. As shown, Figure 6As shown, PWM table T1 is a region of the PWM table for the current frame, and PWM table T2 is a region of the new PWM table corresponding to PWM table T1. PWM table T3 is a region in the final PWM table corresponding to PWM table T1 and PWM table T2. In step S312, brightness compensation is performed according to the final PWM table. Figure 6 As shown, the coefficients in pulse width modulation table T3 are the higher of the corresponding coefficients in the pulse width modulation table for the current frame and the corresponding coefficients in the new pulse width modulation table. For example, coefficient L1 in pulse width modulation table T1 is 0, and the corresponding coefficient L3 in pulse width modulation table T2 is 20. Since 20 > 0, the corresponding coefficient L5 in pulse width modulation table T3 is 20. Similarly, coefficient L2 in pulse width modulation table T1 is 180, and the corresponding coefficient L4 in pulse width modulation table T2 is 86. Since 180 > 86, the corresponding coefficient L6 in pulse width modulation table T3 is 180. Similar calculations can be used to calculate the coefficients in the final pulse width modulation table. Brightness compensation is performed based on the higher of the coefficients in the pulse width modulation table for the current frame and the corresponding coefficients in the new pulse width modulation table, ensuring that the brightness after brightness compensation is no lower than the brightness before brightness compensation.

[0047] In step S310, the dimming speed of the block is determined based on the PWM table for the current frame and the PWM table for the previous frame. When the coefficient of a block in the PWM table for the current frame is greater than the coefficient of the corresponding block in the PWM table for the previous frame, the dimming speed of the block is increased. When the coefficient of a block in the PWM table for the current frame is less than the coefficient of the corresponding block in the PWM table for the previous frame, the dimming speed of the block is decreased. In other words, as the block becomes brighter, the dimming speed is increased to prevent uneven brightness, while as the block becomes darker, the dimming speed is decreased to prevent streaking. Then, in step S312, brightness compensation is performed based on the final PWM table calculated in step S308 and the dimming speed determined in step S310. The brightness compensation method 200 performs brightness compensation by determining the speed of an object and the brightness changes between frames to reduce flicker when the object moves and achieve continuous uniform brightness during local dimming.

[0048] Figure 7 for the reason Figure 1 Flowchart of another brightness compensation method 700 implemented by the brightness compensation system in FIG. Brightness compensation method 700 includes steps S702 to S708. Any reasonable technical changes or step adjustments are within the scope of the present invention. Steps S702 to S708 are as follows:

[0049] Step S702: receiving the input image data of the gray scale and converting the gray scale to luminance;

[0050] Step S704: whether the object in the previous frame is a moving object? If yes, proceed to step S706; if no, end;

[0051] Step S706: generating a pulse width modulation table;

[0052] Step S708: performing luminance compensation.

[0053] Steps S702, S706 and S708 are similar to steps S202, S204 and S206 respectively, and are not described again here. In step S704, whether the object in the previous frame is a moving object is determined by judging whether the object in a frame before the previous frame and the object in the previous frame are in different blocks. If the coefficient in the pulse width modulation table of the previous frame is different from the corresponding coefficient in the pulse width modulation table of a frame before the previous frame, it indicates that the object is in different blocks. If the object is a moving object in the previous frame, proceed to step S706. If the object is not a moving object in the previous frame, steps S706 and S708 can be omitted to avoid flicker. The luminance compensation method 700 is an example for illustration, but the present application is not limited thereto. In some embodiments, if it has been determined that the object is a moving object in the previous frame, step S704 can be omitted.

[0054] The present application discloses luminance compensation methods 200 and 700. Through the luminance compensation methods, luminance compensation can be performed by determining the speed of the object and the luminance change of the frame to reduce flicker when the object moves, and to achieve consistent and uniform luminance when performing local dimming.

[0055] The above only describes the preferred embodiments of the present application, and any equivalent changes and modifications made according to the claims of the present application shall be within the scope of the present application.

Claims

1. A brightness compensation method, comprising: determining a velocity of an object according to a pulse width modulation (PWM) table of a current frame and a pulse width modulation table of a previous frame; generating a new pulse width modulation table according to the velocity and the pulse width modulation table of the current frame; and performing brightness compensation according to the pulse width modulation table of the current frame and the new pulse width modulation table.

2. The method of claim 1, further comprising generating the pulse width modulation table of the current frame and the pulse width modulation table of the previous frame according to input image data.

3. The method of claim 1, wherein generating the new pulse width modulation table according to the velocity and the pulse width modulation table of the current frame comprises: determining a compensation range in a weight matrix according to the velocity; and summing products of coefficients in the pulse width modulation table of the current frame and corresponding coefficients in the weight matrix within the compensation range, and dividing the sum by a sum of the coefficients in the weight matrix within the compensation range to generate the new pulse width modulation table.

4. The method of claim 3, wherein a larger range of the compensation range corresponds to a higher velocity of the object.

5. The method of claim 1, wherein performing brightness compensation according to the pulse width modulation table of the current frame and the new pulse width modulation table comprises: performing brightness compensation according to a higher one of a coefficient in the pulse width modulation table of the current frame and a corresponding coefficient in the new pulse width modulation table.

6. The method of claim 1, further comprising increasing a dimming speed of a block when a coefficient of the block in the pulse width modulation table of the current frame is greater than a coefficient of the block in the pulse width modulation table of the previous frame.

7. The method of claim 1, further comprising decreasing a dimming speed of a block when a coefficient of the block in the pulse width modulation table of the current frame is less than a coefficient of the block in the pulse width modulation table of the previous frame.

8. The method of claim 1, wherein generating the new pulse width modulation table according to the velocity and the pulse width modulation table of the current frame comprises: determining whether the object in a frame before the previous frame is in a different block than the object in the previous frame; and generating the new pulse width modulation table according to the velocity and the pulse width modulation table of the current frame if the object in the frame before the previous frame is in a different block than the object in the previous frame.

9. A brightness compensation system, comprising: a gray scale to brightness module; a backlight brightness calculation module coupled to the gray scale to brightness module and configured to: determine a velocity of an object according to a pulse width modulation (PWM) table of a current frame and a pulse width modulation table of a previous frame; and generate a new pulse width modulation table according to the velocity and the pulse width modulation table of the current frame. ​ a brightness compensation module coupled to the backlight brightness calculation module, for performing brightness compensation according to the pulse width modulation table of the current frame and the new pulse width modulation table; and a backlight module coupled to the brightness compensation module.

10. The brightness compensation system of claim 9, wherein the backlight brightness calculation module is further for generating the pulse width modulation table of the current frame and the pulse width modulation table of the previous frame according to input image data.

11. The brightness compensation system of claim 9, wherein the backlight brightness calculation module is for: determining a compensation range in a weight matrix according to the speed; and summing up products of coefficients in the pulse width modulation table of the current frame and corresponding coefficients in the weight matrix in the compensation range, and dividing the sum by a sum of the coefficients in the weight matrix in the compensation range to generate the new pulse width modulation table.

12. The brightness compensation system of claim 11, wherein a larger range of the compensation range corresponds to a higher speed of the object.

13. The brightness compensation system of claim 9, wherein the brightness compensation module is for: performing brightness compensation according to a higher one of a coefficient in the pulse width modulation table of the current frame and a corresponding coefficient in the new pulse width modulation table.

14. The brightness compensation system of claim 9, wherein the brightness compensation module increases a dimming speed of a block when a coefficient of the block in the pulse width modulation table of the current frame is greater than a coefficient of the block in the pulse width modulation table of the previous frame.

15. The brightness compensation system of claim 9, wherein the brightness compensation module decreases a dimming speed of a block when a coefficient of the block in the pulse width modulation table of the current frame is less than a coefficient of the block in the pulse width modulation table of the previous frame.

16. The brightness compensation system of claim 9, wherein the backlight brightness calculation module is for: determining whether the object in a frame before the previous frame and the object in the previous frame are in different blocks; and generating the new pulse width modulation table according to the speed and the pulse width modulation table of the current frame if the object in the frame before the previous frame and the object in the previous frame are in different blocks.

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