Color difference compensation circuit and driving device for display using the same

Abstract

A color difference compensation circuit and a driving device for a display using the color difference compensation circuit are provided. The color difference compensation circuit includes: a data remapping unit configured to remap display data of pixels having color difference so that the original grayscale range of the display data has a changed grayscale range, and provide display data having a grayscale range obtained by remapping, in which the highest grayscale level of the original grayscale range is lowered to the second grayscale range and the lowest grayscale level of the original grayscale range is raised to the first grayscale range; and a color difference compensation unit configured to perform color difference compensation on the display data having the changed grayscale range, and provide the display data on which the color difference compensation has been performed.

Description

Technical Field

[0001] The present disclosure relates to color difference compensation, and more particularly, to a color difference compensation circuit for performing color difference compensation on pixels having color difference and a driving device for a display applying the color difference compensation circuit. Background Art

[0002] Recently, LCD panels or OLED panels are widely used as display panels.

[0003] Display panels can exhibit color differences due to factors such as errors during the manufacturing process. This means that pixels or areas of the displayed image have uneven brightness in the form of smears. Defects caused by color differences are called chromatic aberration defects.

[0004] In order to provide a display panel with improved image quality, it is necessary to compensate for the color difference defect.

[0005] Various methods may be used to calculate a compensation value for compensating for color difference of a pixel. Typically, a compensation value having a gain of 100% is applied.

[0006] To compensate for color difference, a convergence function may be added. A convergence function is a technique for applying gain to a compensation value differently depending on the input grayscale level.

[0007] In a high grayscale range, if a color difference compensation value having a gain of 100% is applied for color difference compensation, the grayscale may be quickly saturated. In addition, in the case of a low grayscale range, it is difficult to predict the compensation value.

[0008] Therefore, the convergence function is implemented to weakly apply the compensation gain from a specific gray level toward the lowest gray level in the low gray level range, or to weakly apply the compensation gain from a specific gray level toward the highest gray level in the high gray level range.

[0009] However, the color difference compensation method has problems in compensating for the color difference.

[0010] Illustratively, a pixel may include a combination of three colors: red (R), blue (B), and green (G). To represent the color of a pixel, the grayscale level of red (R) may fall within a range where a compensation value having a gain of 100% is applied. The grayscale level of blue (B) or green (G) may fall within a high grayscale level range or a low grayscale level range where a convergence function is applied.

[0011] In this case, in order to compensate for the color difference of the pixel, the grayscale of red R may be compensated by a gain of 100%, but the grayscale of blue B or green G has a compensation range where the gain is lower than 100%.

[0012] As described above, if the color difference of a pixel is compensated by the gain having the same level for each color, the ratio of red R, blue B, and green G constituting the color of the pixel changes. As a result, the color of the pixel changes.

[0013] Schematically, the skin color may change to green.

[0014] Since color difference compensation is performed by applying gains having the same level to grayscale levels, a change in color occurs.

[0015] Therefore, when color difference compensation is performed on the color of a pixel, it is necessary to develop a color difference compensation method that can suppress color changes.

[0016] Furthermore, there are difficulties in performing color difference compensation for high and low gray levels of pixels.

[0017] Illustratively, if the grayscale range is set based on 8 bits, the display data has grayscales of 0 to 255. Grayscale 0, which is a lower grayscale, cannot be compensated, and grayscale 255, which is a higher grayscale, cannot be compensated.

[0018] As described above, since the range of high and low gray levels that can be compensated is limited, it is difficult to apply color difference compensation at a desired level.

[0019] Therefore, it is necessary to solve the limitation of the chromatic aberration compensation range of pixels. Summary of the Invention

[0020] Various embodiments are directed to providing a color difference compensation circuit capable of performing color difference compensation for high grayscale levels and low grayscale levels, and a driving device for a display applying the color difference compensation circuit.

[0021] Furthermore, various embodiments are directed to providing a color difference compensation circuit capable of preventing color changes of pixels when color difference compensation is performed on the pixels, and a driving device for a display using the color difference compensation circuit.

[0022] In addition, various embodiments aim to provide a color difference compensation circuit and a driving device for a display applying the color difference compensation circuit, which can suppress the color change of pixels caused by color difference compensation by applying adjustment gains with the same ratio to colors to compensate for the color differences of pixels.

[0023] In addition, various embodiments aim to provide a chromatic aberration compensation circuit and a driving device for a display applying the chromatic aberration compensation circuit, which can suppress the color change of pixels caused by chromatic aberration compensation by performing chromatic aberration compensation on pixels considering different brightness change characteristics for each color.

[0024] In an embodiment, a color difference compensation circuit may include: a data remapping unit configured to remap display data of pixels having color difference so that an original grayscale range of the display data has a changed grayscale range, and provide display data having the following grayscale range by remapping, in which the highest grayscale level of the original grayscale range is lowered to the second grayscale level of the grayscale range, and the lowest grayscale level of the original grayscale range is raised to the first grayscale level; and a color difference compensation unit configured to perform color difference compensation on the display data having the changed grayscale range, and provide the display data on which color difference compensation has been performed.

[0025] In an embodiment, a driving device for a display may include: a recovery unit configured to recover display data from a data group; a data remapping unit configured to remap display data of pixels having color difference so that an original grayscale range of the display data has a changed grayscale range, and provide display data having the following grayscale range by remapping, in which the highest grayscale level of the original grayscale range is lowered to the second grayscale level of the grayscale range, and the lowest grayscale level of the original grayscale range is raised to the first grayscale level; a color difference compensation unit configured to perform color difference compensation on the display data having the changed grayscale range, and provide the display data on which color difference compensation has been performed; a gamma circuit configured to provide a gamma voltage for each grayscale level; a digital-to-analog converter configured to select a gamma voltage corresponding to the display data output by the color difference compensation unit, and output the selected gamma voltage as an analog signal; and an output circuit configured to output a source signal for driving the analog signal.

[0026] The advantage of the present disclosure is that it can ensure a margin for correcting the highest grayscale level and the lowest grayscale level by changing the grayscale range so as to lower the highest grayscale level of the display data by remapping and increase the lowest grayscale level of the display data to change the grayscale range, and it can perform color difference compensation for high grayscale levels and low grayscale levels using the ensured margin range.

[0027] Furthermore, the present disclosure applies adjustment gains having the same ratio to the colors of the pixels when performing color difference compensation on the pixels.

[0028] Therefore, the present disclosure can maintain the color of the pixel on which the color difference compensation is performed because the color combination ratio for expressing the pixel does not significantly change despite the color difference compensation being performed.

[0029] Furthermore, since color difference compensation can be performed in consideration of luminance variation characteristics that differ for each color of a pixel, the present disclosure can suppress color variation of a pixel due to the color difference compensation.

[0030] Therefore, the present disclosure has the effect that, since color difference compensation can be performed without significant change in the original color of a pixel, image quality can be improved and reliability of a driving circuit and a display device can be ensured.

[0031] Furthermore, the present disclosure is advantageous in that various options can be provided to a driving circuit and a display device by selectively performing remapping and color difference compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a block diagram illustrating a color difference compensation circuit according to an embodiment of the present disclosure and a driving device for a display to which the color difference compensation circuit is applied.

[0033] Figure 2 is a schematic diagram illustrating color difference.

[0034] Figure 3 is a graph used to describe remapping.

[0035] Figure 4 is a graph showing the relationship between the input grayscale level and the gain of the convergence function.

[0036] Figure 5 is a graph illustrating application of adjustment gains having given ratios according to an embodiment of the present disclosure.

[0037] Figure 6 is a graph showing luminance change characteristics corresponding to the grayscale level of each color of a pixel. DETAILED DESCRIPTION

[0038] Embodiments of the present disclosure are configured to apply remapping to allow for compensation of color differences in both low and high grayscale levels.

[0039] Furthermore, an embodiment of the present disclosure is configured to apply adjustment gains having the same ratio to compensation values ​​to prevent color variation of pixels due to color difference compensation.

[0040] For the driving device for a display according to the embodiment of the present disclosure, reference may be made to Figure 1 .exist Figure 1 In the embodiment, the color difference compensation circuit can be understood as including a color difference compensation unit 40, a gain adjustment unit 30 and a color difference memory 20.

[0041] exist Figure 1 In the embodiment, the driving apparatus 100 includes a restoration unit 10, a color difference memory 20, a gain adjustment unit 30, a data remapping unit 80, a color difference compensation unit 40, a digital-to-analog converter (DAC) 50, a gamma circuit 60, and an output circuit 70.

[0042] The driving device 100 may provide a source signal to a display panel (not shown) according to an input data packet, and may perform color difference compensation on color difference pixels.

[0043] In the driving apparatus 100, the restoration unit 10 receives the data packet and restores the display data from the data packet.

[0044] A pixel may have a color represented by a combination of three colors: red R, blue B, and green G. Therefore, the data packet includes display data corresponding to red R, blue B, and green G. The restoration unit 10 restores the display data of red R, blue B, and green G corresponding to one pixel in sequence.

[0045] In addition to display data, the data packet may also include a clock required for display, control data, etc. The recovery unit 10 may also recover the clock and control data and provide the clock and control data to necessary components.

[0046] In a display panel, color difference can appear in pixel or block units. Figure 2 To understand the color difference formed in the block unit. Figure 2 In FIG, “MB” indicates a color difference block. Each pixel included in the color difference block MB can be understood as having color difference.

[0047] like Figure 2 As shown, each pixel may have position information. The pixel P may be configured to have position information for row and column position values. Schematically, Figure 2 The position information of the upper leftmost pixel P may be defined as (188, 80).

[0048] In addition, Figure 2 In the embodiment, a compensation value for color difference for compensating for distorted color may be set for each pixel included in the color difference block MB.

[0049] In case of a color mode (or RGB mode), compensation values ​​for color difference compensation may be defined for display data corresponding to red R, display data corresponding to blue B, and display data corresponding to green G, respectively.

[0050] As described above, the position information of the pixel with color difference and the compensation value for the color may be obtained during the test process.

[0051] A method of calculating a compensation value during a test may be variously set according to a manufacturer's intention, and a detailed description thereof is omitted.

[0052] The compensation values ​​calculated during the test as described above may be stored in the color difference memory 20 of the driving device 100 .

[0053] Therefore, the color difference memory 20 may store color difference information including position information of pixels having color difference and compensation values ​​for their colors.

[0054] The gain adjustment unit 30 is configured to provide an adjustment compensation value, wherein the adjustment compensation value is generated by applying an adjustment gain having the same ratio to a compensation value of a color of a pixel. Figure 4 and Figure 5 The detailed operation of the gain adjustment unit 30 is described.

[0055] The data remapping unit 80 receives the display data of the pixel from the restoration unit 10 , performs remapping on the display data, and provides the color difference compensation unit 40 with the display data of the pixel whose grayscale range has been changed after the remapping.

[0056] The data remapping unit 80 remaps display data of pixels having color differences so that the original grayscale range of the display data has a changed grayscale range, and provides display data having a grayscale range by remapping, in which the highest grayscale level of the original grayscale range is lowered to the second grayscale level of the grayscale range, and the lowest grayscale level of the original grayscale range is raised to the first grayscale level.

[0057] The remapping of the data remapping unit 80 changes the highest grayscale level to the second grayscale level by further increasing the upper limit of the grayscale level range than the original grayscale level range, and changes the lowest grayscale level to the first grayscale level by further decreasing the lower limit of the grayscale level range than the original grayscale level range.

[0058] To this end, the data remapping unit 80 may add at least one bit representing an upper limit of the grayscale range and at least one bit representing a lower limit of the grayscale range to the display data.

[0059] Furthermore, the data remapping unit 80 may perform the same remapping on the display data of the colors of the pixels.

[0060] Illustratively, the data remapping unit 80 may increase the upper limit of the grayscale range by adding 1 bit representing the upper limit to the original grayscale range of 8 bits whose highest grayscale level is 255.

[0061] In this case, if Figure 3As shown, the grayscale level of the highest grayscale level 255 of the original grayscale range can be relatively lowered by increasing the upper limit of the grayscale range. In this case, the highest grayscale level 255 of the previous original grayscale range can be set to, for example, grayscale level 236 in the grayscale range whose upper limit has been increased. Therefore, the margin grayscale for color difference compensation of the highest grayscale level 255 of the previous original grayscale range can form up to 16 grayscale levels (i.e., grayscale level 255 - grayscale level 239) within the grayscale range.

[0062] Furthermore, the data remapping unit 80 may lower the lower limit of the gray level range by adding 1 bit representing the lower limit to the original gray level range of 8 bits whose lowest gray level is 0.

[0063] In this case, if Figure 3 As shown, the grayscale level of the lowest grayscale level 0 of the original grayscale range can be relatively increased by lowering the lower limit of the grayscale range. In this case, the lowest grayscale level 0 of the previous original grayscale range can be set to, for example, grayscale level 16 in the grayscale range whose lower limit has been lowered. Therefore, the color difference compensation margin grayscale level for the lowest grayscale level 0 of the previous original grayscale range can form up to 16 grayscale levels (i.e., 16 grayscale levels minus 0 grayscale levels) in the grayscale range.

[0064] The data remapping unit 80 can change the upper limit and lower limit of the grayscale range by adding 1 bit indicating the upper limit and 1 bit indicating the lower limit respectively to the original grayscale range of 8 bits with the highest grayscale level being 255. The obtained effect is the same as above, so its redundant description is omitted.

[0065] As described above, the color difference compensation unit 40 performs color difference compensation on the display data having the grayscale range changed by remapping.

[0066] The color difference compensation unit 40 may provide the position information of the pixel to the gain adjustment unit 30. In addition, the color difference compensation unit 40 receives the adjustment compensation value corresponding to the position information provided by the gain adjustment unit 30.

[0067] Furthermore, the color difference compensation unit 40 performs color difference compensation on the display data of the color of the pixel using the adjustment compensation value corresponding to the position information, and outputs the display data of the color of the pixel on which the color difference compensation has been performed.

[0068] The color difference compensation of the display data of the color of the pixel can be understood to be performed in sequence.

[0069] The DAC 50 may output the display data output by the color difference compensation unit 40 as an analog signal.

[0070] The DAC 50 may be understood to include a latch for latching display data, a shift register for shifting the latched display data, and a digital-to-analog conversion circuit for converting the shifted display data into an analog signal, and is briefly illustrated for ease of description.

[0071] The gamma circuit 60 is configured to provide the DAC 50 with the same number of gamma voltages as the number of gray levels within the gray level range.

[0072] Therefore, the DAC 50 may select a gamma voltage corresponding to a digital value of display data and may output the selected gamma voltage as an analog signal.

[0073] The output circuit 70 may output a source signal for driving the analog signal output by the DAC 50 , and may be configured to use an output buffer, for example.

[0074] As described above, the gain adjustment unit 30 is configured to prevent the color of the pixel from being changed when color difference compensation is performed on the pixel, and to provide adjustment gains having the same ratio to be applied to the colors of the pixel.

[0075] To this end, the gain adjustment unit 30 receives the display data and the position information of the pixel from the color difference compensation unit 40. The position information may be included in the control data corresponding to the display data, and a detailed example thereof is omitted.

[0076] The gain adjustment unit 30 receives compensation values ​​of colors corresponding to position information from the color difference memory 20 , generates adjustment compensation values ​​by applying adjustment gains having the same ratio to the compensation values ​​of the colors, and provides the adjustment compensation values ​​to the color difference compensation unit 40 .

[0077] Illustratively, the gain adjustment unit 30 may select a lowest compensation ratio of compensation ratios applied to grayscale levels of display data as an adjustment gain for a color of a pixel, and may generate and provide an adjustment compensation value.

[0078] Reference Figure 4 and Figure 5 Describe this in detail.

[0079] Ke Ru Figure 4 Set the compensation ratio of the input grayscale level, that is, the compensation gain.

[0080] exist Figure 4, the lowest gray level is indicated as "LE", the first gray level is indicated as "LS", the second gray level is indicated as "HS", and the highest gray level is indicated as "HE". In this case, the second gray level HS is higher than the first gray level, and if the gray level range is set from gray level 0 to gray level 255, illustratively, the first gray level can be set to gray level 64, and the second gray level can be set to gray level 192.

[0081] In addition, "LC" indicates a low gray level range of the lowest gray level LE or greater to less than the first gray level LS. "NC" indicates an intermediate gray level range of the first gray level LS or greater to the second gray level HS or less. "HC" indicates a high gray level range of greater than the second gray level HS to the highest gray level HE or less.

[0082] like Figure 4 As shown, if the input grayscale level corresponds to the middle grayscale level range NC, a compensation ratio of 100% is applied.

[0083] If the input gray level belongs to the low gray level range LC, a lower compensation ratio is applied as the gray level becomes lower.

[0084] Furthermore, if the input grayscale level belongs to the high grayscale level range HC, a lower compensation ratio is applied as the grayscale level becomes higher.

[0085] The convergence function is applied to the low gray level range LC and the high gray level range HC. In the low gray level range and the high gray level range, the compensation ratio of the compensation value is applied differently according to the gray level.

[0086] In an embodiment of the present disclosure, the gain adjustment unit 30 is configured to provide an adjustment compensation value generated by applying adjustment gains having the same ratio to compensation values ​​of colors of pixels.

[0087] That is to say, if Figure 5 As shown, the adjustment gain A having the same ratio may be applied to the compensation value of the color.

[0088] exist Figure 5 In the figure, F(Xr) is the compensation value for red R, A is the adjustment gain, and Yr is the adjustment compensation value for red R. Furthermore, F(Xg) is the compensation value for green G, and Yg is the adjustment compensation value for green G. Furthermore, F(Xb) is the compensation value for blue B, and Yb is the adjustment compensation value for blue B.

[0089] like Figure 5As shown, embodiments of the present disclosure may provide adjustment compensation values ​​Yr, Yg, and Yb, which are generated by applying adjustment gains A having the same ratio to compensation values ​​of colors of pixels.

[0090] In this case, although color difference compensation is performed on the pixel, the ratio of red R, blue B, and green G constituting the color of the pixel may be maintained. The color of the pixel represented by the combination of red R, blue B, and green G may be maintained.

[0091] For example, the lowest compensation ratio of the compensation ratios of the grayscale levels of the display data applied to the pixels may be selected and applied as the adjustment gain having the same ratio as that applied to the colors of the pixels.

[0092] An advantage of the present disclosure is that the color of a pixel on which color difference compensation is performed can be maintained because a color combination ratio for representing the pixel does not significantly change by applying an adjustment gain having the same ratio despite the color difference compensation being performed.

[0093] Colors can have different brightness variation characteristics. Figure 6 The luminance change characteristics corresponding to the grayscale level of the pixel color are shown.

[0094] Therefore, the gain adjustment unit 30 may have color characteristic compensation values ​​for one or two or more colors in order to compensate for brightness variation characteristics that differ for each color, and may additionally apply the characteristic compensation values ​​to the compensation values ​​of the colors.

[0095] In this case, the luminance variation characteristics that differ for each color of the pixel can be compensated when color difference compensation is performed on the pixel, and the variation in the color of the pixel due to the color difference compensation can be more effectively suppressed.

[0096] Therefore, the effect of the present disclosure is that, since color difference compensation can be performed on high grayscale levels and low grayscale levels, and color difference compensation can be performed without significant changes in the original color of the pixel, the image quality can be improved and the reliability of the driving circuit and the display device can be ensured.

Claims

1. A chromatic aberration compensation circuit, comprising: a data remapping unit configured to remap display data of pixels having color differences so that an original grayscale range of the display data has a changed grayscale range, and provide the display data having a grayscale range through the remapping, in which a highest grayscale level of the original grayscale range is lowered to a second grayscale level of the grayscale range and a lowest grayscale level of the original grayscale range is raised to a first grayscale level; as well as The color difference compensation unit is configured to perform color difference compensation on the display data of the color of the pixel using the adjustment compensation value corresponding to the position information, and output the display data of the color of the pixel on which the color difference compensation has been performed.

2. The color difference compensation circuit according to claim 1, wherein: The data remapping unit: changing the highest gray level to the second gray level by further increasing the upper limit of the gray level range compared to the original gray level range, and The lowest gray level is changed to the first gray level by further lowering a lower limit of the gray level range compared to the original gray level range.

3. The chromatic aberration compensation circuit according to claim 1, wherein: The data remapping unit performs the remapping for adding at least one bit representing an upper limit of the grayscale range and at least one bit representing a lower limit of the grayscale range to the display data.

4. The chromatic aberration compensation circuit according to claim 1, wherein: The data remapping unit performs the remapping on the display data of the color of the pixel.

5. The chromatic aberration compensation circuit according to claim 4 , further comprising: a color difference memory configured to store color difference information, the color difference information including position information of the pixel having color difference and a compensation value of the color; as well as a gain adjustment unit configured to provide an adjustment compensation value generated by applying an adjustment gain having a same ratio to the compensation value of the color of the pixel, The color difference compensation unit performs the color difference compensation on the display data of the color of the pixel using the adjustment compensation value corresponding to the position information.

6. The color difference compensation circuit according to claim 5, wherein: The gain adjustment unit: receiving the position information from the chromatic aberration compensation unit, receiving the compensation value of the color corresponding to the position information from the color difference memory, generating the adjusted compensation value by applying the adjustment gain having the same ratio to the compensation value, and The adjustment compensation value is provided to the color difference compensation unit.

7. The chromatic aberration compensation circuit according to claim 6, wherein: The gain adjustment unit: further receiving the display data of the color of the pixel from the color difference compensation unit, and A lowest compensation ratio among compensation ratios applied to grayscale levels of the display data is selected as the adjustment gain of the color of the pixel, and the adjustment compensation value is generated and provided.

8. The chromatic aberration compensation circuit according to claim 7, wherein: The gain adjustment unit applies the compensation ratio that becomes lower as the grayscale level becomes lower in a low grayscale level range from a lowest grayscale level or greater to a preset first grayscale level or less, applies the same compensation ratio to each grayscale level in a middle grayscale level range from the first grayscale level or greater to a preset second grayscale level or less, and applies the compensation ratio that becomes lower as the grayscale level becomes higher in a high grayscale level range from the second grayscale level to a highest grayscale level or less, and The second grayscale level is higher than the first grayscale level.

9. A driving device for a display, comprising: a recovery unit configured to recover display data from the data packet; a data remapping unit configured to remap display data of pixels having color differences so that an original grayscale range of the display data has a changed grayscale range, and provide the display data having a grayscale range through the remapping, in which a highest grayscale level of the original grayscale range is lowered to a second grayscale level of the grayscale range and a lowest grayscale level of the original grayscale range is raised to a first grayscale level; a color difference compensation unit configured to perform color difference compensation on the display data of the color of the pixel using an adjustment compensation value corresponding to the position information, and output the display data of the color of the pixel on which the color difference compensation has been performed; a gamma circuit configured to provide a gamma voltage for each grayscale level; a digital-to-analog converter configured to select a gamma voltage corresponding to the display data output by the color difference compensation unit and output the selected gamma voltage as an analog signal; as well as The output circuit is configured to output a source signal for driving the analog signal.

10. The driving device according to claim 9, wherein: The data remapping unit: changing the highest gray level to the second gray level by further increasing the upper limit of the gray level range compared to the original gray level range, and The lowest gray level is changed to the first gray level by further lowering a lower limit of the gray level range compared to the original gray level range.

11. The driving device according to claim 9, wherein: The data remapping unit performs the remapping for adding at least one bit representing an upper limit of the grayscale range and at least one bit representing a lower limit of the grayscale range to the display data.

12. The driving device according to claim 9, wherein: The data remapping unit performs the remapping on the display data of the color of the pixel.

13. The driving device according to claim 12, further comprising: a color difference memory configured to store color difference information, the color difference information including position information of the pixel having color difference and a compensation value of the color; as well as a gain adjustment unit configured to provide an adjustment compensation value generated by applying an adjustment gain having a same ratio to the compensation value of the color of the pixel, The color difference compensation unit performs the color difference compensation on the display data of the color of the pixel using the adjustment compensation value corresponding to the position information.

14. The driving device according to claim 13, wherein: The gain adjustment unit: receiving the position information from the chromatic aberration compensation unit, receiving the compensation value of the color corresponding to the position information from the color difference memory, generating the adjusted compensation value by applying the adjustment gain having the same ratio to the compensation value, and The adjustment compensation value is provided to the color difference compensation unit.

15. The driving device according to claim 14, wherein: The gain adjustment unit: further receiving the display data of the color of the pixel from the color difference compensation unit, and A lowest compensation ratio among compensation ratios applied to grayscale levels of the display data is selected as the adjustment gain of the color of the pixel, and the adjustment compensation value is generated and provided.

16. The driving device according to claim 15, wherein: The gain adjustment unit applies the compensation ratio that becomes lower as the grayscale level becomes lower in a low grayscale level range from a lowest grayscale level or greater to a preset first grayscale level or less, applies the same compensation ratio to each grayscale level in a middle grayscale level range from the first grayscale level or greater to a preset second grayscale level or less, and applies the compensation ratio that becomes lower as the grayscale level becomes higher in a high grayscale level range from the second grayscale level to a highest grayscale level or less, and The second grayscale level is higher than the first grayscale level.

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