Image data processing device and method for realizing local dimming

Abstract

The present invention provides an image data processing device and method for realizing local dimming. The present invention allows the power consumption of a backlight source to be reduced by reducing the dimming value through the brightness distribution of pixels.

Description

Technical Field

[0001] The present embodiment relates to a display technology for reducing power consumption of a backlight source. Background Art

[0002] Among the various components constituting the electronic device, the component with the highest power consumption is the display device. The display device remains in an on state during the time when information is provided to the user, and continues to emit light during the time when the display device is on, which results in higher power consumption in the display device compared to other components of the electronic device.

[0003] For this reason, manufacturers of electronic devices have been conducting research and development to reduce the power consumption of display devices. A typical example thereof is a technology for switching a display device to a standby mode or turning on only a portion of a display panel.

[0004] However, since these technologies aim to reduce the power consumption of the display device by actually constraining the user environment to a certain extent, they inevitably cause some inconvenience to the user.

[0005] On the other hand, technology capable of reducing power consumption of a display device without changing a user environment or while providing a user environment involving a small amount of change negligible to a user is under development, and a typical example thereof is a local dimming technology.

[0006] Local dimming is a technology for partially driving a backlight source at different brightnesses. According to local dimming, a display panel can be divided into several areas, and a plurality of backlight units (BLUs) can emit light to the divided areas at different brightnesses. Here, a large difference in the brightness of the backlight units emitting light to each area may cause artifacts.

[0007] Filtering is performed during image processing to remove artifacts, but the brightness of the backlight unit may increase during filtering. In particular, when the brightness of the surrounding backlight units is high, the brightness of the backlight unit may also increase. As the brightness of the backlight unit increases, power consumption may also increase.

[0008] Although the power consumption of the backlight unit is reduced compared to the state before the local dimming is applied, since the power consumption becomes slightly higher as filtering is performed, a more efficient reduction in power consumption may fail.

[0009] In this regard, the present embodiment will provide a local dimming technology for efficiently reducing power consumption. Summary of the invention

[0010] In this context, an object of the present embodiment is to provide a technique for controlling the dimming value to be low through the brightness distribution of pixels.

[0011] Another object of the present embodiment is to provide a technique for reflecting the fact that actual changes in pixel brightness corresponding to changes in dimming values ​​differ according to pixel levels, to the gain for changing the grayscale value of image data according to the dimming value.

[0012] In order to achieve the above-mentioned purpose, an embodiment provides an image data processing device, including: an image analysis circuit, which is configured to analyze original image data related to a video image divided into multiple areas, and calculate a representative brightness value for each area; a dimming value calculation circuit, which is configured to calculate a dimming value for each area according to the representative brightness value to adjust the brightness of the backlight source; a pixel analysis circuit, which is configured to analyze the brightness distribution of multiple pixels in each area; a dimming control circuit, which is configured to re-adjust the dimming value for an area according to the brightness distribution; and a dimming output circuit, which is configured to output a dimming control signal for driving the backlight source according to the dimming value to a backlight source driving device.

[0013] In the image data processing device, the pixel analysis circuit may analyze the distribution of grayscale values ​​for a plurality of pixels in each region, and the dimming control circuit may adjust the amount of reduction of the dimming value in the one region to correspond to the degree to which the grayscale value indicates low brightness.

[0014] The image data processing device may also include a gain calculation circuit configured to calculate a gain for compensating the original image data based on the dimming value; and a data conversion circuit configured to generate image data converted from the original image data for a pixel in the one area using the gain.

[0015] The image data processing device may further include a gain compensation circuit configured to calculate a first compensation gain for compensating for a difference in a reduction rate of the brightness of the one pixel relative to a reduction rate of the dimming value caused by readjustment of the dimming control circuit.

[0016] In the image data processing apparatus, the difference and the first compensation gain may be varied according to a pixel level including a grayscale value of the original image data.

[0017] In the image data processing apparatus, the gain compensation circuit may use a lookup table (LUT) including pixel levels and first compensation gains corresponding to the pixel levels.

[0018] In the image data processing apparatus, the gain compensation circuit may calculate the first compensation gains for some pixel levels, and may interpolate the first compensation gains for some pixel levels to calculate the first compensation gains for the remaining pixel levels.

[0019] In the image data processing apparatus, the gain compensation circuit may calculate a second compensation gain for compensating for a difference in brightness depending on a position of one pixel or the backlight source.

[0020] In the image data processing apparatus, the data conversion circuit may generate the converted image data using a gain reflecting the first compensation gain or the second compensation gain.

[0021] The image data processing device may further include a filtering circuit configured to adjust the dimming value by filtering so as to reduce a difference in dimming values ​​between regions and a difference in dimming values ​​between frames.

[0022] Another embodiment provides a method for processing image data, the method comprising the following steps: analyzing original image data related to a video image divided into multiple areas to calculate a representative brightness value for each area; calculating a dimming value for each area based on the representative brightness value to adjust the brightness of the backlight source; adjusting the dimming value through spatial filtering so as to reduce the difference in dimming values ​​between areas; analyzing the brightness distribution of multiple pixels in each area; readjusting the dimming value for one area based on the brightness distribution; calculating a gain for compensating the original image data based on the dimming value; and using the gain to generate image data converted from the original image data for a pixel in the one area.

[0023] The step of re-adjusting the dimming value may be performed after the step of adjusting the dimming value through the spatial domain filtering, and when the one area has a low brightness distribution, the dimming value of the one area may be reduced to reduce the brightness of the backlight source for the one area.

[0024] The method of processing image data may further include the step of adjusting the dimming value by time domain filtering so as to reduce the difference in dimming values ​​between frames.

[0025] The step of adjusting the dimming value by spatial domain filtering may include the step of: in a case where there is a difference in dimming values ​​between two areas, increasing the dimming value in the area with a lower dimming value to reduce the difference between the two areas.

[0026] The step of analyzing the brightness distribution may include the step of analyzing the brightness distribution of each region using cumulative density function data (CDF data) related to the grayscale values ​​of the plurality of pixels.

[0027] As described above, according to the present embodiment, the power consumption of the backlight unit can be reduced by a low dimming value and a gain for compensating for it. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other aspects, features and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings, in which:

[0029] Figure 1 is a block diagram of a display device according to an embodiment.

[0030] Figure 2 is a block diagram of an image data processing apparatus according to an embodiment.

[0031] Figure 3 is a diagram showing an example of reducing a dimming value by analyzing brightness distribution of pixels according to an embodiment;

[0032] Figure 4 is a graph showing actual measurements of a reduction in pixel brightness in response to a reduction in dimming value according to an embodiment;

[0033] Figure 5 is a diagram showing an example of calculating a compensation gain according to an embodiment; and

[0034] Figure 6 is a flowchart of the operation of the image data processing apparatus according to the embodiment. DETAILED DESCRIPTION

[0035] Figure 1 is a block diagram of a display device according to an embodiment.

[0036] refer to Figure 1 The display device 100 may include a host 140, an image data processing device 110, a data driving device 150, a gate driving device 160, a display panel 130, and a backlight source driving device 120, etc.

[0037] The host 140 may recognize the user manipulation, and may generate image data or a dimming control signal according to the user manipulation.

[0038] The image data may be converted into various forms in the display device 100. Hereinafter, the image data generated and transmitted by the host 140 will be referred to as "raw image data" RGB (red, green, and blue) to be distinguished from the converted image data below, and the image data generated and transmitted by the image data processing device 110 will be referred to as "converted image data" RGB'. In addition, the dimming value included in the dimming control signal may be adjusted in the display device 100. Hereinafter, the dimming control signal generated and transmitted by the host 140 will be referred to as "unadjusted dimming control signal" DMS (dimming signal) to be distinguished from the adjusted dimming control signal below, and the dimming control signal generated and transmitted by the image data processing device 110 will be referred to as "adjusted dimming control signal" DMS'.

[0039] Referring to the signal flow, the image data is generated by the host 140, converted by the image data processing device 110, and then sent to the data driving device 150. In addition, the dimming control signal is generated by the host 140, adjusted by the image data processing device 110, and then sent to the backlight driving device 120.

[0040] The image data processing device 110 converts the image data and adjusts the dimming control signal.

[0041] The image data processing device 110 can analyze the original image data RGB of the plurality of pixels P arranged in the display panel 130, and can calculate representative brightness values ​​of the plurality of pixels P. Since the plurality of pixels P have brightness values ​​different from each other, the image data processing device 110 calculates representative brightness values ​​representing the plurality of pixels P. The representative brightness value may be, for example, an average brightness value of the plurality of pixels P. Alternatively, for example, the representative brightness value may be the brightness value that occurs most frequently among the plurality of pixels P, or may be the maximum brightness value of the plurality of pixels P. The image data processing device 110 may calculate representative brightness values ​​of the plurality of pixels P using a CDF (cumulated density function) algorithm or an APL (average pixel level) algorithm. The representative brightness value may include a value of a CDF or an APL.

[0042] The image data processing device 110 can calculate the adjusted dimming value for driving the backlight source 132 based on the representative brightness value or the representative brightness value modified based on a specific configuration. Here, the dimming value can be understood as a dimming brightness value. The higher the dimming value, the higher the brightness value of the backlight source 132. For example, if the dimming value is 100%, the backlight source 132 can be driven at the maximum brightness, and if the dimming value is 0%, the backlight source 132 can be driven at the minimum brightness, or the backlight source 132 can be turned off.

[0043] As the representative brightness value decreases, the image data processing device 110 may reduce the adjusted dimming value of the backlight source 132. In other words, the image data processing device 110 may reduce the brightness of the backlight source 132 as the representative brightness value decreases.

[0044] The image data processing device 110 can convert the original image data RGB to compensate the grayscale value of each pixel according to the adjusted dimming value. The image data processing device 110 can calculate a factor called "gain", the original image data RGB can be converted using the gain, and the grayscale value can be compensated. Although the brightness (or illumination) of the pixel can change with the adjustment of the dimming value, if the grayscale value displayed by the pixel is adjusted according to the gain to correspond to the adjusted dimming value, the pixel can maintain the original brightness. For example, the image data processing device 110 can convert the original image data RGB so that the grayscale value of each pixel increases as the adjusted dimming value decreases. Therefore, the brightness of each pixel can remain the same. Here, the gain can have the characteristic of increasing the grayscale value. The rate of decrease of the dimming value and the rate of increase of the grayscale value of the pixel can be different from each other and can be different according to the pixel level.

[0045] The image data processing device 110 may generate an adjusted dimming control signal DMS′ according to the adjusted dimming value and may output the adjusted dimming control signal DMS′ to the backlight source driving device 120 .

[0046] On the other hand, a plurality of pixels P may be arranged in the display panel 130, and data lines and gate lines connected to the plurality of pixels P may be arranged in the display panel 130. The gate driving device 160 may transmit a scan signal SS to the gate line to connect each pixel P to the data line, and the data driving device 150 may supply a data voltage Vdata corresponding to image data to the data line to drive each pixel P.

[0047] The image data processing device 110 may transmit a gate control signal GCS to the gate driving device 160, and may transmit a data control signal DCS to the data driving device 150, thereby controlling the driving timing of each pixel P. In this regard, the gate driving device 160 may be referred to as a "gate driving IC (GDIC)", the data driving device 150 may be referred to as a "source driver IC (SDIC)", and the image data processing device 110 may be referred to as a "timing controller (TCON)".

[0048] The backlight source 132 may be disposed in the background of the display panel 130 , and the backlight source 132 may be driven by the backlight source driving device 120 .

[0049] The backlight driving device 120 may control the brightness of the light source constituting the backlight 132. For example, the light source may be provided by a fluorescent lamp (FL) type or a light emitting diode (LED) type.

[0050] The backlight driver 120 may control the dimming of the backlight 132. For example, the backlight driver 120 may control the dimming of the backlight 132 using an analog dimming scheme for reducing the amount of power PBL supplied to the backlight 132 when the backlight 132 is continuously driven. As another example, the backlight driver 120 may control the dimming of the backlight 132 using a pulse width modulation (PWM) scheme for adjusting the ratio of the on time to the off time when the backlight 132 is discontinuously driven. According to an embodiment, the PWM scheme may be a method of controlling the brightness of the backlight using the magnitude of a voltage charged to a capacitor or the like through a PWM signal. The adjustment of the dimming value may be understood as the adjustment of the duty cycle of the PWM signal in the PWM scheme.

[0051] In the analog dimming scheme, the dimming control signal DMS or DMS′ may be implemented in the form of an analog voltage or an analog current, and in the PWM scheme, the dimming control signal DMS or DMS′ may be implemented in the form of a PWM signal.

[0052] Figure 2 is a block diagram of an image data processing apparatus according to an embodiment.

[0053] refer to Figure 2 The image data processing device 110 may include an image analysis circuit 210, a dimming value calculation circuit 220, a filtering circuit 230, a pixel analysis circuit 240-1, a signal analysis circuit 240-2, a dimming control circuit 250, a dimming output circuit 260, a gain compensation circuit 270, a gain calculation circuit 280 and a data conversion circuit 290.

[0054] The image analysis circuit 210 may receive a video image including a plurality of regions including a plurality of pixels. The backlight source 132 may adjust dimming so that each region of the video image has a different dimming value.

[0055] The image analysis circuit 210 can analyze the original image data RGB about the video image to calculate the representative brightness value of each area. The image analysis circuit 210 can calculate the representative brightness value of the original R image data, the original G image data, and the original B image data to generate an appropriate dimming value for local dimming. The representative brightness value may include an average pixel level (APL). The representative brightness value may include an average value, a median value, or a value obtained by a histogram or pooling.

[0056] For example, the image analysis circuit 210 may use the maximum value among the original R image data, the original G image data, and the original B image data as the representative brightness value. Alternatively, the image analysis circuit 210 may use a value obtained by applying appropriate weights to the original R image data, the original G image data, and the original B image data and summing them as the representative brightness value. Alternatively, the image analysis circuit 210 may use a value where the original image data RGB is mapped to a specific curve as the representative brightness value.

[0057] The dimming value calculation circuit 220 can calculate the dimming value. The dimming value calculation circuit 220 can calculate the initial dimming value DMV of each area according to the representative brightness value. The dimming value calculation circuit 220 can use a logarithmic function, an exponential function, or a user function to calculate the initial dimming value DMV of the representative brightness value.

[0058] The filtering circuit 230 can filter the dimming value. The filtering circuit 230 can adjust the initial dimming value DMV by filtering to generate a filtered dimming value DMV'. The filtering circuit 230 can perform spatial filtering. The initial dimming value DMV is different between multiple areas of the video image, which causes a difference, so the filtering circuit 230 can adjust the difference. Generally, if the initial dimming value DMV in one area is less than the initial dimming value DMV in an adjacent area, the filtering circuit 230 can increase the initial dimming value DMV of the one area, thereby reducing the difference between them. Optionally, if the initial dimming value DMV in one area is greater than the initial dimming value DMV in an adjacent area, the filtering circuit 230 can reduce the initial dimming value DMV of the one area, thereby reducing the difference between them. Therefore, the filtering circuit 230 can prevent artifacts caused by the difference.

[0059] The filter circuit 230 may use the weighted sum to adjust the dimming value. The filter circuit 230 may receive the weighted sum as feedback and may generate a new weighted sum to perform a stable filtering operation.

[0060] In addition, the filtering circuit 230 can perform time domain filtering. The filtering circuit 230 can adjust the difference in dimming values ​​between frames by time domain filtering. The dimming value can change between the current frame and the subsequent frame, and the filtering circuit 230 can reduce the difference in dimming values ​​between the current frame and the subsequent frame. The filtering circuit 230 can prevent flickering that occurs when the difference in dimming values ​​between frames increases.

[0061] The pixel analysis circuit 240-1 may analyze the brightness distribution of a plurality of pixels in each region. The pixel analysis circuit 240-1 may determine whether the brightness distribution of the pixels in each region tends to be low brightness. The pixel analysis circuit 240-1 may send the result of analyzing the brightness distribution of the pixels to the dimming control circuit 250. The result of analyzing the brightness distribution of the pixels may be reflected in the adjustment of the dimming value. For example, if the brightness distribution of the pixels in one region tends to be low brightness, the dimming control circuit 250 may adjust the filtered dimming value DMV' to be low.

[0062] The pixel analysis circuit 240-1 may use a histogram to analyze the brightness distribution of the pixels. The pixel analysis circuit 240-1 may compare the number of low brightness pixels with the number of high brightness pixels based on the histogram result. Alternatively, the pixel analysis circuit 240-1 may receive a representative brightness value calculated by the image analysis circuit 210 as feedback, and may use the representative brightness value to determine the brightness distribution of the pixels.

[0063] The signal analysis circuit 240-2 may analyze an input signal used as a dimming control signal. For example, the dimming control signal may be implemented in the form of a PWM signal, and the backlight source may be driven to correspond to the ratio of the on-time of the PWM signal. Here, the PWM signal may correspond to the input dimming control signal DMS analyzed by the signal analysis circuit 240-2. The signal analysis circuit 240-2 may analyze the characteristics (e.g., frequency, period, level, or duty cycle) of the PWM signal. The signal analysis circuit 240-2 may send the result of analyzing the input dimming control signal DMS to the dimming control circuit 250. The result of analyzing the input dimming control signal DMS may be reflected in the adjustment of the dimming value.

[0064] The dimming control circuit 250 may finally determine the dimming value. The dimming control circuit 250 may reflect the result of analyzing the brightness distribution of the pixel and the result of analyzing the input dimming control signal DMS to the filtered dimming value DMV′.

[0065] If the brightness distribution of pixels in one area tends to be low brightness, the dimming control circuit 250 can reduce the dimming value of the one area to reduce the brightness of the backlight source in the one area. For example, the dimming control circuit 250 can calculate the adjusted dimming value DMV" by reflecting the result of the brightness distribution to the filtered dimming value DMV'. The dimming control circuit 250 can send the adjusted dimming value DMV" to the dimming output circuit 260.

[0066] The dimming control circuit 250 may change the dimming value. The dimming control circuit 250 may compare the dimming value with a target dimming value and may gradually change the dimming value so that after a predetermined transition time, the dimming value reaches the target dimming value.

[0067] The dimming output circuit 260 can convert the dimming value into a dimming control signal, and can output the dimming control signal to the backlight source driving device. The dimming output circuit 260 can convert the adjusted dimming value DMV" into an adjusted dimming control signal DMS'. Preferably, the input dimming control signal DMS and the adjusted dimming control signal DMS' are of the same type. To this end, the dimming output circuit 260 must control the period or frequency of the adjusted dimming control signal DMS' to match the period or frequency of the input dimming control signal DMS.

[0068] The gain calculation circuit 280 can calculate a factor, i.e., a gain Q, for compensating the original image data RGB according to the dimming value. The brightness (or illumination) of the pixel can change as the dimming value is adjusted, and the gain Q can adjust the grayscale value of the pixel to correspond to the adjusted dimming value. Then, regardless of the adjustment of the dimming value, the pixel can maintain the original brightness. In order to adjust the grayscale value displayed by the pixel, the gain Q can compensate the original image data RGB, thereby generating the converted image data RGB'. The pixel can display the adjusted grayscale value through the converted image data RGB'.

[0069] For example, the gain calculation circuit 280 may receive an adjusted dimming value DMV" from the dimming control circuit 250, and may calculate a gain based on the adjusted dimming value DMV". Here, the adjusted dimming value DMV" may be a dimming value generated by reflecting the brightness distribution to the filtered dimming value DMV'. Although the adjusted dimming value DMV" is lower than the initial dimming value DMV, the data conversion circuit 290 may compensate the original image data by the gain Q, and may generate converted image data RGB', and the pixel may output the grayscale value of the converted image data RGB'. Therefore, the pixel may have the same brightness as before the dimming value was adjusted.

[0070] The gain compensation circuit 270 may compensate for the gain Q. The gain compensation circuit 270 may compensate for the gain Q in consideration of various situations.

[0071] In the first example, the gain compensation circuit 270 can compensate for the phenomenon that the rate of change of the dimming value and the rate of change of the brightness of the pixel vary according to the pixel level. Hereinafter, the pixel level may be understood as a concept including the grayscale value or brightness of the image data for one pixel. In order to compensate for the difference in the adjustment ratio of the brightness of the pixel relative to the adjustment ratio of the adjusted dimming value DMV" according to the pixel level, the gain compensation circuit 270 may calculate the compensation gain Qc. For example, the gain compensation circuit 270 may calculate the compensation gain Qc that compensates for the difference between the reduction rate of the brightness and the reduction rate of the adjusted dimming value DMV". Since the rate of change of the dimming value and the rate of change of the brightness of the pixel vary according to the pixel level, the compensation gain Qc may also vary according to the pixel level.

[0072] For example, in a first pixel having a first pixel level, a ratio of a reduction rate of pixel brightness to a reduction rate of an adjusted dimming value DMV" may be greater than 1, but in a second pixel having a second pixel level, a ratio of a reduction rate of pixel brightness to a reduction rate of an adjusted dimming value DMV" may be less than 1. Therefore, the compensation gain Qc for the first pixel level and the compensation gain Qc for the second pixel level may be different from each other.

[0073] The gain compensation circuit 270 may use a lookup table (LUT) or an equation to calculate the compensation gain Qc. The lookup table or equation may reflect the actual situation of the change in the ratio of the reduction rate of the pixel brightness to the reduction rate of the adjusted dimming value DMV". The lookup table may be configured to correspond to the compensation gain Qc for all pixel levels. The gain compensation circuit 270 may retrieve the compensation gain Qc for a pixel level (e.g., grayscale value) from the lookup table, and may send the compensation gain Qc to the gain calculation circuit 280. In addition, the equation may reflect factors that occur in the process of manufacturing the panel and measuring the brightness of the panel. The gain compensation circuit 270 may use an equation to calculate the compensation gain Qc.

[0074] In the second example, the gain compensation circuit 270 can compensate for the phenomenon that the brightness of the pixel corresponding to the dimming value varies according to the position of the pixel and the distance from the backlight source. The gain compensation circuit 270 can obtain information about the brightness of the pixel by using a Gaussian function, or a polynomial function of 1 or 2 according to the sampling point combination, etc. The gain compensation circuit 270 can calculate a compensation gain Qc for compensating for the phenomenon that the brightness of the pixel corresponding to the dimming value DMV" varies according to the position of the pixel and the distance from the backlight source.

[0075] The gain calculation circuit 280 may finally determine the gain for compensating the original image data RGB according to the adjusted dimming value DMV″. The gain calculation circuit 280 may finally determine the gain Q by reflecting the compensation gain Qc calculated in the first example or the compensation gain Qc calculated in the second example.

[0076] The gain calculation circuit 280 may use an algorithm for finally determining the gain Q. If the original image data RGB is in a linear domain, the gain calculation circuit 280 may determine the gain Q using an equation that simply applies the gain Q. Alternatively, if the original image data RGB is in a nonlinear domain, the gain calculation circuit 280 may determine the gain Q using an equation obtained by simply applying a combination of an equation for the gain Q and a gamma curve. In this process, if a gain Q of a high pixel level that falls outside the allowable range of the panel is applied, the gain calculation circuit 280 may perform an operation of appropriately adjusting the gain Q and an operation of applying the same gain Q to the R channel, the G channel, and the B channel, respectively, thereby preventing degradation.

[0077] The data conversion circuit 290 may generate image data RGB′ converted from the original image data RGB using the gain Q. The data conversion circuit 290 may generate converted image data RGB′ by applying the finally determined gain Q to the R image data, the G image data, and the B image data.

[0078] Figure 3 is a diagram illustrating an example of reducing a dimming value by analyzing brightness distribution of pixels according to an embodiment.

[0079] refer to Figure 3 , shows an example in which the pixel analysis circuit 240 - 1 determines the amount of reduction of the dimming value by analyzing the brightness distribution of the pixels.

[0080] The pixel analysis circuit 240 - 1 may identify brightness distributions of multiple regions of a video image, and if the brightness distribution of one region corresponds to low brightness, the dimming value of the region may be reduced, thereby reducing power consumption of the backlight source.

[0081] The pixel analysis circuit 240-1 may analyze the brightness distribution of pixels in an area, thereby obtaining a curve indicating the relationship between the number of pixels and the pixel level. Here, the number of pixels may be histogram data or NCDF (normalized cumulated density function) data.

[0082] For example, if the first area has a low brightness distribution, and if the second area has a high brightness distribution, the brightness distribution of the first area may have a first curve I, and the brightness distribution of the second area may have a second curve II. The number of pixels of the brightness distribution curve may be represented by adding high-level pixels to low-level pixels. On the horizontal axis indicating the pixel level, the pixel level may change from a low level to a high level as it goes from left to right. Since the first area includes a large number of low-brightness pixels, the first curve I may be biased toward a lower level. On the other hand, since the second area includes a large number of high-brightness pixels, the second curve II may be relatively biased toward a higher level compared to the first curve I.

[0083] In the case where a specific number of pixels is configured as a threshold value Th on the vertical axis indicating the number of pixels, the pixel analysis circuit 240-1 can obtain the pixel level at the point where the threshold value Th intersects with each curve. The pixel analysis circuit 240-1 can obtain the first pixel level VAL_1 as the pixel level at the point where the first curve I intersects with the threshold value Th and the second pixel level VAL_2 as the pixel level at the point where the second curve II intersects with the threshold value Th. Since the pixel level changes from a lower level to a higher level as going from left to right on the horizontal axis indicating the pixel level, the first pixel level VAL_1 may be smaller than the second pixel level VAL_2.

[0084] In addition, the pixel analysis circuit 240-1 can obtain the final size of the dimming value for reducing power consumption according to the pixel level at the point where the threshold value Th intersects each curve. For example, the pixel analysis circuit 240-1 can determine a larger dimming value reduction amount as the pixel level decreases, and can determine a smaller dimming value reduction amount as the pixel level increases. Since the first pixel level VAL_1 is less than the second pixel level VAL_2, the pixel analysis circuit 240-1 can determine a larger dimming value reduction amount for the first pixel level VAL_1, and can determine a smaller dimming value reduction amount for the second pixel level VAL_2.

[0085] Figure 4 is a graph showing actual measurements of a decrease in brightness of a pixel in response to a decrease in dimming value according to an embodiment.

[0086] refer to Figure 4 , showing actual measurement results showing that the rate of change of dimming value and the rate of change of pixel brightness vary according to pixel level. The decrease of dimming value corresponding to the pixel level from 0 to 255 and the decrease of pixel brightness corresponding thereto can be actually measured in two setting environments. Figure 4A first graph 410 and a second graph 420 are shown, wherein the first graph 410 shows the ratio of the rate of change of pixel brightness depending on the pixel level from 0 to 255 to the rate of change of dimming value in a first setting environment (setting 1), and the second graph 420 shows the ratio of the rate of change of pixel brightness depending on the pixel level from 0 to 255 to the rate of change of dimming value in a second setting environment (setting 2).

[0087] When the pixel level in the first setting environment is 128, if the initial brightness (OFF brightness) is 77.58, if the subsequent brightness (ON brightness) is 39.09, and if the rate of change of the dimming value (duty cycle, %) is 45.75, the rate of change of brightness (brightness ratio, %) can be 50.38, and the ratio of the rate of change of brightness (ratio, %) to the rate of change of the dimming value can be 110.13.

[0088] On the other hand, in the case where the pixel level in the second setting environment is 128, if the initial brightness (OFF brightness) is 77.58, if the subsequent brightness (ON brightness) is 56.06, and if the rate of change of the dimming value (duty cycle, %) is 77.83, the rate of change of brightness (brightness ratio, %) can be 72.27, and the ratio of the rate of change of brightness (ratio, %) to the rate of change of dimming can be 92.85.

[0089] Referring to the first graph 410 and the second graph 420, it can be understood that the ratio of the rate of change (ratio, %) of brightness to the rate of change of dimming value varies according to the pixel level. In addition, the ratio of the rate of change (ratio, %) of brightness to the rate of change of dimming value at the same pixel level can vary according to the setting environment.

[0090] Figure 5 is a diagram illustrating an example of calculating a compensation gain according to an embodiment.

[0091] refer to Figure 5 , shows an example in which a gain compensation circuit of an image data processing device calculates a compensation gain by reflecting the fact that a ratio of a change rate of brightness to a change rate of a dimming value differs according to a pixel level.

[0092] The gain compensation circuit can be reflected by Figure 4 The actual characteristics shown in the curve diagram in FIG. 1 are used to configure several points (e.g., several points at the pixel level), and these points can be interpolated to calculate the compensation gain. That is, the gain compensation circuit can obtain the compensation gain of some pixel levels, and the compensation gain of some pixel levels can be interpolated to calculate the compensation gain of the remaining pixel levels.

[0093] The gain compensation circuit may use a lookup table for all pixel levels to calculate the accurate compensation gain.

[0094] Figure 6 is a flowchart illustrating a local dimming operation of the image data processing apparatus according to the embodiment.

[0095] refer to Figure 6 , the image data processing apparatus may receive a video image including a plurality of regions including a plurality of pixels (step S602).

[0096] The image data processing device may analyze the original image data regarding the video image, and may calculate a representative brightness value of each area (step S604 ).

[0097] The image data processing apparatus may calculate a dimming value for each area according to the representative brightness value to adjust the brightness of the backlight source (step S606 ).

[0098] The image data processing device may filter the dimming value (step S608). The image data processing device may increase the dimming value so that the difference in the dimming value is reduced by filtering.

[0099] The image data processing apparatus may analyze the brightness distribution of pixels in each region (step S610 ).

[0100] The image data processing device may adjust the dimming value and may output the adjusted dimming value (step S612). The image data processing device may output a dimming control signal to the backlight source driving device according to the adjusted dimming value. The image data processing device may reduce the dimming value of an area to reduce the brightness of the backlight source of an area with low brightness distribution.

[0101] The image data processing device may calculate a gain (step S614). The image data processing device may calculate a gain by reflecting the fact that a ratio of a change rate of pixel brightness to a change rate of a dimming value differs according to a pixel level.

[0102] The image data processing apparatus may generate image data converted from the original image data using the calculated gain (step S616 ).

[0103] CROSS-REFERENCE TO RELATED APPLICATIONS

[0104] This application claims priority to Korean Patent Application No. 10-2019-0170329, filed on Dec. 19, 2019, which is hereby incorporated by reference for all purposes as if fully set forth herein.

Claims

1. An image data processing device, comprising: an image analysis circuit configured to analyze raw image data related to a video image segmented into a plurality of regions and calculate a representative brightness value for each region; a dimming value calculation circuit configured to calculate a dimming value for each area according to the representative brightness value to adjust the brightness of the backlight source; a pixel analysis circuit configured to analyze a brightness distribution for a plurality of pixels in each region; a dimming control circuit configured to readjust a dimming value for a zone according to the brightness distribution; a dimming output circuit configured to output a dimming control signal for driving the backlight source according to the dimming value to a backlight source driving device; a gain calculation circuit configured to calculate a gain for compensating the original image data according to the dimming value; a data conversion circuit configured to generate image data converted from the original image data for one pixel in the one area using the gain; as well as A gain compensation circuit is configured to calculate a first compensation gain for compensating for a difference in a reduction rate of the brightness of the one pixel relative to a reduction rate of the dimming value caused by readjustment of the dimming control circuit.

2. The image data processing device according to claim 1, wherein: The pixel analysis circuit analyzes distribution of grayscale values ​​for a plurality of pixels in each area, and the dimming control circuit adjusts a reduction amount of a dimming value in the one area according to a degree to which the grayscale values ​​indicate low brightness.

3. The image data processing device according to claim 1, wherein: The difference and the first compensation gain vary according to a pixel level including a grayscale value of the original image data.

4. The image data processing device according to claim 3, wherein: The gain compensation circuit uses a lookup table, or LUT, including pixel levels and first compensation gains corresponding to the pixel levels.

5. The image data processing device according to claim 3, wherein: The gain compensation circuit calculates first compensation gains for some pixel levels and interpolates the first compensation gains for some pixel levels to calculate first compensation gains for remaining pixel levels.

6. The image data processing device according to claim 1, wherein: The gain compensation circuit calculates a second compensation gain for compensating for a difference in brightness depending on a position of one pixel or the backlight source.

7. The image data processing device according to claim 6, wherein: The data conversion circuit generates converted image data using a gain reflecting the first compensation gain or the second compensation gain. 8 . The image data processing apparatus according to claim 1 , further comprising a filtering circuit configured to adjust the dimming value by filtering so as to reduce a difference in dimming values ​​between areas and a difference in dimming values ​​between frames.

9. A method for processing image data, the method comprising the following steps: analyzing raw image data associated with a video image segmented into a plurality of regions to calculate a representative brightness value for each region; Calculating a dimming value for each area according to the representative brightness value to adjust the brightness of the backlight source; Adjusting the dimming value by spatial filtering so as to reduce the difference in dimming values ​​between the regions; Analyzing brightness distribution of a plurality of pixels in each region; Adjusting the dimming value for an area according to the brightness distribution; Calculating a gain for compensating the original image data according to the dimming value; generating image data converted from the original image data for one pixel in the one region using the gain, and A first compensation gain for compensating for a difference in a reduction rate of the luminance of the one pixel due to the readjustment with respect to a reduction rate of the dimming value is calculated.

10. The method according to claim 9, wherein: After the step of adjusting the dimming value by the spatial domain filtering, a step of re-adjusting the dimming value is performed, and Wherein, in a case where the one area has a low brightness distribution, the dimming value of the one area is reduced to reduce the brightness of the backlight source for the one area.

11. The method according to claim 9, further comprising the steps of: The dimming value is adjusted by time domain filtering so as to reduce the difference of dimming values ​​between frames.

12. The method according to claim 9, wherein: In the step of adjusting the dimming value by spatial domain filtering, in the case where there is a difference in dimming values ​​between two areas, the dimming value in the area with the lower dimming value is increased to reduce the difference between the two areas.

13. The method according to claim 9, wherein: In the step of analyzing the brightness distribution, the brightness distribution of each region is analyzed using cumulative density function data, ie, CDF data, related to the grayscale values ​​of the plurality of pixels.

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