Remove unevenness compensation device and data processing circuit for driving display panel

Abstract

This invention provides a non-uniformity compensation device and a data processing circuit for driving a display panel. It provides a technique for resolving non-uniformity in a display panel to which gamma is applied, wherein a non-uniformity compensation value is generated in the logarithmic domain to improve the non-linearity problem caused by gamma.

Description

Technical Field

[0001] This invention relates to a technique for solving the mura phenomenon in display panels. Background Technology

[0002] Multiple pixels are arranged on a display panel, and an image is formed on the display panel according to the brightness of each pixel. The brightness of each pixel is controlled according to grayscale values, and the driving device used in the display panel generates a data voltage to be supplied to each pixel based on the grayscale values. In addition, the brightness of each pixel is controlled by adjusting the light-emitting device (e.g., organic light-emitting diode (OLED)) or open element (e.g., liquid crystal (LC)) according to the data voltage.

[0003] A crucial factor in determining image quality during the driving process of a display panel is brightness uniformity. If the brightness is uneven, the image quality of the display panel is perceived as low. When the same grayscale value is applied to multiple pixels on a display panel, brightness variations between pixels can degrade image quality.

[0004] However, due to manufacturing issues or pixel arrangement problems, most display panels inherently possess brightness variations. This brightness variation is also known as murras. If the pixels of an uncompensated display panel are driven with the same grayscale value, an image with patterns such as imperfections may not be displayed. Images with patterns such as imperfections occur due to the brightness variations of individual pixels.

[0005] To eliminate unevenness, several demura compensation devices have been developed. However, these devices suffer from the following problems: the calculation of compensation values ​​is complex and inaccurate. This issue arises because gamma is applied to the display panel.

[0006] Gamma is applied to display panels to reflect human visual characteristics. The application of gamma makes the relationship between grayscale and brightness values ​​non-linear, and the calculation of compensation values ​​is complex, with its accuracy decreasing due to the non-linear relationship. Summary of the Invention

[0007] This invention provides a non-uniformity compensation technique with high accuracy without complicating computational processing.

[0008] In one aspect, an unevenness compensation device includes: a receiving circuit configured to acquire a plurality of brightness values ​​corresponding to a plurality of grayscale values ​​for a region of a display panel to which gamma is applied; and a calculation circuit configured to calculate a compensation value for the grayscale values ​​by mapping the plurality of brightness values ​​to a logarithmic domain, thereby resolving unevenness caused by the difference between a target brightness value and the plurality of brightness values.

[0009] In another aspect, a data processing circuit includes: a receiving circuit configured to receive image data, the image data including grayscale values ​​of each pixel arranged in a display panel; a memory configured to store compensation values ​​for grayscale values ​​for each region; a compensation circuit configured to compensate the grayscale values ​​according to the compensation values ​​and generate converted image data having the compensated grayscale values; and a transmitting circuit configured to transmit the converted image data to a source driver, wherein the compensation values ​​are calculated by mapping the brightness values ​​of the display panel to a logarithmic domain.

[0010] As described above, according to this embodiment, the unevenness compensation value can be accurately calculated through a simple process. Attached Figure Description

[0011] Figure 1 This is a configuration diagram of a display device according to an embodiment.

[0012] Figure 2 This is a diagram illustrating the signal flow of the non-uniformity compensation process according to an embodiment.

[0013] Figure 3 This is a diagram illustrating a typical process for removing unevenness compensation.

[0014] Figure 4 This is a graph showing the shape of the gamma curve when transformed into the logarithmic domain.

[0015] Figure 5 This is a configuration diagram of the unevenness compensation device according to an embodiment.

[0016] Figure 6 This is a diagram illustrating a method for calculating compensation values ​​in the logarithmic domain according to an embodiment.

[0017] Figure 7 This is a block diagram of a data processing circuit according to an embodiment. Detailed Implementation

[0018] Figure 1 This is a block diagram of a display device according to an embodiment.

[0019] refer to Figure 1 The display device 100 may include a data processing circuit 110, a source driver 120, a gate driver 130, and a display panel 140, etc.

[0020] Multiple pixels can be arranged on the display panel 140. Alternatively, multiple pixels can be grouped into multiple regions. For ease of description, the regions in block form will be described below.

[0021] For the purpose of describing the embodiments, in Figure 1 The diagram shows a first region B1 and a second region B2. Each of the first region B1 and the second region B2 may contain N×M pixels (N and M are natural numbers). For example, each of the first region B1 and the second region B2 may contain 4×4 pixels. The first region B1 and the second region B2 may be arranged adjacent to each other and may have different brightness characteristics. For example, pixels in the first region B1 and pixels in the second region B2 may have different brightness values ​​for the same grayscale value.

[0022] The data processing circuit 110 can compensate for the grayscale values ​​included in the image data RGB to resolve the brightness difference between different areas, and generate image data RGB' using the compensated grayscale values.

[0023] The data processing circuit 110 can store compensation values ​​for each region and use these compensation values ​​to compensate for the grayscale values ​​of each pixel. Storing compensation values ​​for each region is to minimize the storage capacity of the compensation values, and according to the embodiment, compensation values ​​can be stored for each pixel.

[0024] The data processing circuit 110 can send the converted image data RGB' to the source driver 120.

[0025] Additionally, the data processing circuit 110 can send control signals (e.g., timing control signals) to the source driver 120. The data processing circuit 110 can also send control signals (e.g., timing control signals) to the gate driver 130. In terms of using these control signals to control the timing of the source driver 120 and the gate driver 130, the data processing circuit 110 can also be referred to as a timing controller.

[0026] The source driver 120 can use the converted image data RGB' to control the brightness of the pixels arranged in the display panel 140.

[0027] The converted image data RGB' includes the grayscale value of each pixel (i.e., the grayscale value with the actual applied compensation value), and the source driver 120 can generate a data voltage based on the grayscale value and supply the generated data voltage to each pixel. For example, the source driver 120 can supply a first data voltage Vd1 to a pixel in the first region B1 and apply a second data voltage Vd2 to a pixel in the second region B2.

[0028] The source driver 120 can supply gamma data voltage to each pixel to reflect human visual characteristics.

[0029] The source driver 120 may include a digital-to-analog converter (DAC) that converts grayscale values ​​into data voltages. Additionally, gamma may be applied to the DAC.

[0030] Multiple gamma voltages corresponding to 2.0 to 2.8 gamma can be supplied to the DAC. Furthermore, the DAC can select one of these gamma voltages based on the grayscale value and output the selected gamma voltage as the data voltage.

[0031] The gamma voltage circuit that generates multiple gamma voltages can be located in the source driver 120 or in a separate device.

[0032] Multiple gamma voltages can be used to form a gamma curve to which 2.2 gamma can be applied. Because gamma is applied exponentially, the gamma curve can have the form of a non-linear exponential function.

[0033] On the other hand, a non-uniformity compensation device can be used to generate the compensation value used in the data processing circuit 110. The non-uniformity compensation device can capture an image of the display panel and generate compensation values ​​for each area using the captured image data. In this case, since gamma has been applied to the display panel, the non-uniformity compensation device can apply inverse gamma to the captured image data and use the captured image data with inverse gamma applied to calculate the compensation value. The non-uniformity compensation device can map the brightness values ​​included in the captured image data to the logarithmic domain to apply inverse gamma. Additionally, the non-uniformity compensation device can calculate the compensation grayscale value by performing logarithmic operations in the logarithmic domain and apply inverse logarithm to the calculated value to calculate the final compensation grayscale value. Furthermore, the non-uniformity compensation device can generate compensation values ​​based on the compensation grayscale values. In the logarithmic domain, the gamma curve is linearized, therefore, the calculation can be simplified and accurate.

[0034] Figure 2 This is a diagram illustrating the signal flow of the non-uniformity compensation process according to an embodiment.

[0035] refer to Figure 2 The data processing circuit 110 can send image data RGB with certain grayscale values ​​to the source driver 120. Additionally, the source driver 120 can convert these grayscale values ​​into a data voltage Vd and supply the data voltage Vd to the display panel 140. In this case, gamma can be applied to the data voltage Vd.

[0036] Additionally, the brightness Lx of each pixel on the display panel 140 can be controlled based on the data voltage Vd. The brightness Lx of each pixel can be different from each other. The deviation of the brightness Lx of the pixels is also called unevenness.

[0037] The camera device 220 can capture images of the display panel 140, measure the brightness values ​​for each pixel or area, and store the measured brightness values.

[0038] In addition, the unevenness compensation device 210 can receive digital brightness values ​​DLx from the camera device 220 and use the brightness values ​​DLx of each pixel to calculate compensation values ​​to resolve unevenness.

[0039] This processing can be repeated for specific grayscale values. For example, the brightness value DLx can be stored in the unevenness compensation device 210 for each pixel or region for five major grayscale values ​​(e.g., 32, 64, 128, 192 and 200) among the five major grayscale values ​​from 0 to 225.

[0040] The unevenness compensation device 210 can acquire multiple brightness values ​​DLx corresponding to multiple grayscale values ​​and calculate compensation values ​​DCp corresponding to multiple grayscale values, thereby resolving the unevenness caused by the difference between the target brightness value and the brightness value DLx. Here, the target brightness value can be mainly determined based on the brightness value of the area located in the center of the display panel.

[0041] In addition, the unevenness compensation device 210 can send the compensation value DCp to an external device so that the calculated compensation value DCp is stored in the memory of the data processing circuit 110.

[0042] Figure 3 This is a diagram illustrating a typical process for removing unevenness compensation.

[0043] exist Figure 3 In the example, a region of the display panel represents a first brightness value Lxa for grayscale value 32, and the target brightness value for removing unevenness compensation at grayscale value 32 can be a second brightness value Lxb.

[0044] Because there is a difference ΔC between the measured luminance value Lxa and the target luminance value Lxb, the data processing circuit needs to use the grayscale value D to compensate for the grayscale value 32, and then send the compensated grayscale value to the source driver. Based on the measured gamma curve (i.e.... Figure 3 (The solid line in the image) When the grayscale value D is input, the pixels in the corresponding area can emit light with a second brightness value Lxb.

[0045] However, in order to inspect the unevenness compensation device Figure 3 The solid line in the graph indicates the gamma curve. To remove unevenness, the luminance value of all grayscale values ​​must be measured. Therefore, a typical luminance removal device uses an interpolation function between the measured luminance values ​​(i.e., ...). Figure 3 The grayscale value after compensation is calculated using the dashed line (in the image). Figure 3 In the diagram, the grayscale value calculated by the interpolation function corresponds to D'.

[0046] In this method, the compensated gray value can be calculated relatively simply by using an interpolation function with a linear function form. However, the actual brightness value of the gray value D' is the third brightness value Lxc, not the second brightness value Lxb, which leads to a decrease in the accuracy of the compensation.

[0047] To improve the accuracy of compensation, the interpolation function can be configured as a second-order or higher-order function. However, the problem with higher-order functions is that they are computationally complex and, in some cases, do not improve accuracy.

[0048] To improve this problem, embodiments of the present invention propose a method for calculating compensated grayscale values ​​by mapping the obtained luminance values ​​to the logarithmic domain.

[0049] Figure 4 This is a graph showing the form of the gamma curve when transformed into the logarithmic domain.

[0050] exist Figure 4 In the middle, on the left, is a graph showing the brightness values ​​of each grayscale value acquired when photographing a display panel to which gamma was applied. Because gamma was applied to the display panel, this graph has an exponential function form.

[0051] Figure 4 The right side of the graph shows a logarithmic curve applied to the grayscale and brightness values. When... Figure 4 As shown on the right, when logarithms are applied to grayscale and brightness values, the graph changes linearly. In this embodiment, the ease and accuracy of calculation can be improved by calculating the compensated grayscale value within the linear graph.

[0052] Figure 5 This is a configuration diagram of the unevenness compensation device according to an embodiment.

[0053] refer to Figure 5 The unevenness compensation device 210 may include a receiving circuit 510, a calculation circuit 520, and a transmitting circuit 530, etc.

[0054] The receiving circuit 510 can acquire multiple brightness values ​​corresponding to multiple grayscale values ​​for each area of ​​the display panel to which gamma is applied. The receiving circuit 510 can receive the brightness values ​​through communication with a camera device.

[0055] The computing circuit 520 can calculate the compensation value of the grayscale value, so that the unevenness caused by the difference between the target brightness value and the measured brightness value can be resolved.

[0056] The calculation circuit 520 can map the measured luminance value to the logarithmic domain. Assuming the grayscale value of the measured luminance value has been determined beforehand, the calculation circuit 520 can calculate the logarithmic luminance value by applying a logarithm to the measured luminance value. The value obtained by applying a logarithm to a target luminance value (logarithmic target luminance value) can be pre-stored.

[0057] In the logarithmic domain, one axis may include gray values ​​applied logarithmically (logarithmic gray values), while the other axis may include brightness values ​​applied logarithmically (logarithmic brightness values).

[0058] In addition, the computing circuit 520 can generate an interpolation function between logarithmic brightness values ​​in the logarithmic domain, and match the logarithmic target brightness value with the interpolation function to generate a logarithmically compensated gray value (logarithmically compensated gray value).

[0059] Here, the interpolation function can include a linear function.

[0060] In addition, the computing circuit 520 can calculate the compensated gray value by applying the inverse logarithm (e.g., an exponential function) to the logarithmically compensated gray value.

[0061] Additionally, the computing circuit 520 can calculate a compensation value used to convert the grayscale value of the measured brightness value into a compensation grayscale value. For example, the data processing circuit can generate a compensation grayscale value by applying the grayscale value to a linear function, and here, the gain value and offset value applied to the linear function can be calculated as compensation values.

[0062] The compensation values ​​are finally inserted into the memory of the data processing circuitry used to drive the display panel. For this purpose, the transmitting circuit 530 can send these compensation values ​​to a means for storing the compensation values ​​in the memory of the data processing circuitry.

[0063] Figure 6 This is a diagram illustrating a method for calculating compensation values ​​in the logarithmic domain according to an embodiment.

[0064] refer to Figure 6 The measured brightness values ​​can be mapped to the logarithmic domain, with one axis including logarithmic gray values ​​and the other axis including logarithmic brightness values.

[0065] The luminance value measured for grayscale value 32 can be mapped to a first logarithmic luminance value log(Lxa) (refer to A' in the figure). For grayscale value 32, the logarithmic target luminance value can be mapped to a second logarithmic luminance value log(Lxb) (refer to B' in the figure).

[0066] Additionally, in the interpolation function (the dashed line connecting the measured brightness values), the logarithmic gray value log(D) corresponding to the second logarithmic brightness value log(Lxb) can be calculated as the logarithmic compensation gray value. Finally, the compensation gray value D can be calculated by applying the inverse logarithm to the logarithmic compensation gray value.

[0067] In addition, the unevenness compensation device can calculate the gain and offset values ​​used to convert grayscale value 32 with compensation grayscale value D as the compensation value.

[0068] The calculated compensation value can be stored in the memory of the data processing circuit and can be used for image data compensation.

[0069] Figure 7 This is a block diagram of a data processing circuit according to an embodiment.

[0070] refer to Figure 7 The data processing circuit 110 may include a receiving circuit 710, a compensation circuit 720, a memory 730, and a transmitting circuit 740, etc.

[0071] The receiving circuit 710 can receive image data. The receiving circuit 710 can receive image data through communication with a host device or the like.

[0072] The compensation circuit 720 can convert image data. The compensation circuit 720 can convert image data by considering various factors. The compensation circuit 720 can convert image data to compensate for pixel degradation, and can also convert image data to add specific effects to the image. Additionally, the compensation circuit 720 can convert image data to perform unevenness compensation.

[0073] The memory 730 can store compensation values ​​used for image data conversion. The memory 730 can store compensation values ​​for unevenness removal for each region. The memory 730 can store compensation values ​​for specific grayscale values, referred to as planes.

[0074] When the gray values ​​included in the image data correspond to a specific gray value, the compensation circuit 720 can convert the corresponding gray value according to the compensation value, calculate the compensation value of gray values ​​other than the specific gray value according to the interpolation technique, and use the calculated compensation value to convert the corresponding gray value.

[0075] The compensation circuit 720 can identify the position of the pixel corresponding to the gray value included in the image data, select an area based on the position, determine the compensation value for the corresponding area in the memory 730, and compensate the gray value.

[0076] The converted image data is generated based on the compensated grayscale values, and the transmitting circuit 740 can send the converted image data to the source driver.

[0077] The above describes an embodiment. According to this embodiment, the non-uniformity compensation value can be accurately calculated without complicated processing.

[0078] In the exemplary systems described above, although the methods have been described based on flowcharts using a series of steps or blocks, the present invention is not limited to the sequence of steps, and some of the steps may be performed in a different sequence from the remaining steps, or may be performed simultaneously with the remaining steps. Furthermore, those skilled in the art will understand that the steps shown in the flowcharts are not exclusive and may include other steps, or one or more steps in the flowcharts may be removed without affecting the scope of the invention.

[0079] Cross-reference to related applications

[0080] This application claims priority to Korean Patent Application No. 10-2020-0156209, filed on November 20, 2020, which is incorporated herein by reference for all purposes as if fully set forth in the text.

Claims

1. A non-uniformity removing compensation device, comprising: receiving circuitry configured to acquire, for one area of a display panel to which gamma is applied, a plurality of luminance values corresponding to a plurality of gradation values; and computing circuitry configured to compute compensation values of the gradation values by mapping the plurality of luminance values to a logarithmic domain so that a non-uniform phenomenon due to a difference between a target luminance value and the plurality of luminance values is resolved, wherein the computing circuitry is configured to generate a compensation gradation value by applying inverse logarithm to the computed values in the logarithmic domain, and to generate the compensation values from the compensation gradation value.

2. The removal non-uniformity compensation apparatus according to claim 1, wherein, One axis of the logarithmic domain includes gradation values to which logarithm is applied, and the other axis includes luminance values to which logarithm is applied.

3. A non-uniformity removing compensation device, comprising: receiving circuitry configured to acquire, for one area of a display panel to which gamma is applied, a plurality of luminance values corresponding to a plurality of gradation values; and computing circuitry configured to compute compensation values of the gradation values by mapping the plurality of luminance values to a logarithmic domain so that a non-uniform phenomenon due to a difference between a target luminance value and the plurality of luminance values is resolved, wherein the computing circuitry is configured to generate a compensation gradation value by generating an interpolation function corresponding to the luminance values in the logarithmic domain and matching the target luminance value to the interpolation function, and to generate the compensation values from the compensation gradation value.

4. The removal non-uniformity compensation apparatus according to claim 3, wherein, The interpolation function includes a linear function.

5. The removal non-uniformity compensation apparatus of claim 3, wherein, The compensation values include a gain value and an offset value of a function that converts the gradation values to the compensation gradation values.

6. The unevenness removing compensation device according to claim 1 or 3, wherein The target luminance value is generated from luminance values of an area located in the middle of the display panel.

7. The unevenness removing compensation device according to claim 1 or 3, wherein 2.0 to 2.8 gamma is applied to the display panel.

8. The unevenness removing compensation device according to claim 1 or 3, wherein N x M pixels are arranged in the one area, where N and M are natural numbers.

9. A data processing circuit, comprising: receiving circuitry configured to receive image data including gradation values of pixels arranged in a display panel; a memory configured to store, for each area, compensation values of the gradation values; compensation circuitry configured to compensate the gradation values from the compensation values, and generate converted image data having compensated gradation values; and transmitting circuitry configured to transmit the converted image data to a source driver, wherein the compensation values are computed by mapping luminance values of the display panel to a logarithmic domain, and wherein the compensation values are generated from compensation gradation values, and the compensation gradation values are generated by applying inverse logarithm to the computed values in the logarithmic domain.

10. The data processing circuit of claim 9, wherein, The source driver is configured to drive the display panel using a digital-to-analog converter (DAC) to which gamma is applied.

11. The data processing circuit according to claim 10, wherein the source driver is configured to generate or be supplied with a plurality of gamma voltages corresponding to 2.0 to 2.8 gamma, and the DAC is configured to convert a signal in a manner that selects one of the plurality of gamma voltages.

12. The data processing circuit according to claim 9, wherein The memory is configured to store compensation values for specific gray scale values, and The compensation circuit is configured to calculate compensation values for gray scale values other than the specific gray scale values according to an interpolation technique.

13. The data processing circuit of claim 9, wherein, Each region includes N x M pixels, where N and M are natural numbers.

14. The data processing circuit of claim 13, wherein, The compensation circuit is configured to select a region according to a position of each pixel, and to compensate the gray scale value by determining a compensation value of a corresponding region in the memory.

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