KR101075088B1 - Display device and driving method thereof - Google Patents

Abstract

According to an embodiment of the present invention, there is provided a luminance control unit configured to calculate a representative gradation that can represent gradations of first, second, and third input image signals corresponding to each of the first, second, and third colors; When the representative gradation is located in each of the first, second, and third gradation regions, light having first, second, and third luminance is emitted, and the second luminance is higher than the first, third luminance, and the second gradation. A region comprising a light source unit positioned between the first and third gray scale regions; Signal generation for generating first, second and third output video signals corresponding to each of the first, second and third colors and white output video signals corresponding to a white color using the first, second and third input video signals Wealth; Provided is a display including first, second and third sub-pixels corresponding to the first, second and third output image signals and a white sub-pixel corresponding to the white output image signal.

Description

Display and driving method thereof             

1A and 1B show an RGB display and a conventional RGBW display, respectively, as light receiving displays.

2 illustrates an RGBW display according to an embodiment of the invention.

3 is a view showing a liquid crystal panel as the image display unit of FIG.

4 is a diagram illustrating a signal converter of FIG. 2.

5 is a view showing the brightness control unit of FIG.

6 is a view showing the light source unit of FIG.

7 is a view illustrating signal waveforms when driving a light source unit in an analog mode and a digital mode according to an exemplary embodiment of the present invention.

8 to 10 are diagrams showing the relationship between the gray level distribution of an input video signal and the duty on time of a lamp in a dark image, a bright image, and a medium brightness image according to an exemplary embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

250: luminance control unit 251: gray scale extraction unit                 

252: gradation distribution calculation unit 253: analysis unit

254: light source control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display and a driving method thereof, and more particularly to red, green, and white, which display red, green, blue, and white colors, respectively. A display including a blue and white sub-pixel, and a driving method thereof.

As a widely used display, a television or a monitor such as a cathode ray tube (CRT) is used. Meanwhile, there is a need for a flat panel display having excellent characteristics such as thinness, light weight, and low power consumption, such as a liquid crystal display, a plasma display panel, and a field emission display. Various flat panel display devices such as field emission displays and electroluminescent displays (or electroluminescent displays (ELDs)) have been researched and developed.

The display includes a luminescent display that emits light by itself to display an image, such as a plasma display device, and a non-luminescent display that displays an image by using light supplied from a separate light source, such as a liquid crystal display. display).

1A and 1B show a light receiving type display, respectively, showing an RGB display and a conventional RGBW display.

As shown in FIG. 1A, in an RGB display, three sub-pixels of R (red), G (green), and B (blue) form one pixel Pa to display an image.

On the other hand, as shown in FIG. 1B, the conventional RGBW display further includes one W (white) sub-pixel in the R, G, and B sub-pixels to form one pixel Pb.

In the case where the RGB display and the conventional RGBW display use a light source having the same brightness, the conventional RGBW display has more W subpixels, thereby increasing the brightness of the image and making the image brighter at all gray-levels. Is displayed.

However, in the conventional RGBW display, as the image is displayed brightly in all the gray scales, not only the high gray scale image but also the low gray scale image may increase the luminance, so that the dark image cannot be emphasized, and the contrast ratio and sharpness of the image may decrease. It becomes possible.

It is an object of the present invention to provide a display and a driving method thereof capable of emphasizing a dark image in an RGBW display and improving contrast ratio and sharpness of the image.

In order to achieve the object as described above, the present invention, the luminance control unit for calculating a representative gradation that can represent the gradation of the first, second, third input video signal corresponding to each of the first, second, and third colors; ; When the representative gradation is located in each of the first, second, and third gradation regions, light having first, second, and third luminance is emitted, and the second luminance is higher than the first, third luminance, and the second gradation. A region comprising a light source unit positioned between the first and third gray scale regions; Signal generation for generating first, second and third output video signals corresponding to each of the first, second and third colors and white output video signals corresponding to a white color using the first, second and third input video signals Wealth; Provided is a display including first, second and third sub-pixels corresponding to the first, second and third output image signals and a white sub-pixel corresponding to the white output image signal.

Here, the brightness control unit, a gray scale extraction unit for extracting the gray scale of the input image signal; A gradation distribution calculating unit calculating a distribution of the extracted gradations; And analyzing the gray distribution to calculate the representative gray. The representative gradation may include an average gradation and a mode gradation.

The gray level of the input video signal may correspond to the maximum value of the first, second, and third input video signals.

In addition, the grayscale of the input image signal has a range of 0 to H, the first grayscale region is about 0 to 0.078H, the second grayscale region is about 0.078H to 0.90H, and the third grayscale region is 0.90H to H. It can have a range. H may be 255.                     

In addition, the third brightness may be higher than the first brightness.

The brightness controller may include a light source controller for controlling the brightness of the emitted light by outputting a brightness control signal to the light source according to the representative gradation.

In addition, the light source unit may include an inverter and a lamp.

In addition, the light source unit may be driven in one selected from an analog mode and a digital mode. When driving the light source unit in the digital mode, the light source unit has first, second and third duty on time corresponding to each of the first, second and third luminance, and the second duty on time is the It may be longer than the first and third duty on times.

In addition, as the representative gradations located in the first and third gradation regions are increased, the first and third luminance may be increased.

In addition, the first, second, and third colors may be different ones of red, green, and blue.

In addition, the first, second, and third colors may be different from one of cyan, magenta, and yellow.

A first signal region converter for converting a signal region of the input image signal and outputting the signal region to the signal generator; The apparatus may further include a second signal region changer configured to convert the signal region of the output image signal. The first signal region converter may convert from the L * signal region to the Y signal region, and the second signal region converter may convert from the Y signal region to the L * signal region.

The apparatus may further include a signal controller configured to output the output image signal to the image display unit according to a timing.

The image display unit may be a liquid crystal panel.

In addition, the representative gradation may be calculated from the input image signal during one frame.

In another aspect, the present invention includes the steps of calculating a representative gradation that can represent the gradation of the first, second, third input video signal corresponding to each of the first, second, and third colors; Emitting light having first, second, and third luminance when the representative gradation is located in each of the first, second, and third gradation regions; Generating first, second and third output image signals corresponding to the first, second and third colors and white output image signals corresponding to a white color using the first, second and third input image signals; ; And displaying an image using the first, second, and third sub-pixels corresponding to the first, second, and third output image signals, and the white sub-pixel corresponding to the white output image signal. Is higher than the first and third luminance, and the second gradation region is located between the first and third gradation regions.

The calculating of the representative gray level may include extracting a gray level of the input image signal; Calculating a distribution of the extracted gray levels; And analyzing the gray level distribution to calculate the representative gray level. The representative gradation may include an average gradation and a mode gradation.

The gray level of the input video signal may correspond to the maximum value of the first, second, and third input video signals.                     

In addition, the grayscale of the input image signal has a range of 0 to H, the first grayscale region is about 0 to 0.078H, the second grayscale region is about 0.078H to 0.90H, and the third grayscale region is 0.90H to H. It can have a range. H may be 255.

In addition, the third brightness may be higher than the first brightness.

The method may further include outputting a brightness control signal according to the representative gradation to adjust the brightness of the emitted light.

In addition, the step of emitting the light may be one selected from the analog mode and the digital mode. When the light is emitted in the digital mode, the light is emitted during the first, second, and third duty on time corresponding to each of the first, second, and third luminance, and the second duty on time is the same. It may be longer than the first and third duty on times.

In addition, as the representative gradations located in the first and third gradation regions are increased, the first and third luminance may be increased.

In addition, the first, second, and third colors may be different ones of red, green, and blue.

In addition, the first, second, and third colors may be different from one of cyan, magenta, and yellow.

The method may further include converting a signal region of the input video signal before generating the output video signal; The method may further include converting a signal region of the output image signal. The first signal region converter may convert from the L * signal region to the Y signal region, and the second signal region converter may convert from the Y signal region to the L * signal region.                     

The method may further include outputting the output image signal to the image display unit according to a timing.

In addition, the display may be a liquid crystal display device.

In addition, the representative gradation may be calculated from the input image signal during one frame.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

2 is a view showing an RGBW display according to an embodiment of the present invention, FIG. 3 is a view showing a liquid crystal panel as the image display unit of FIG. 2, FIG. 4 is a view showing a signal conversion unit of FIG. 5 is a diagram illustrating the luminance adjusting unit of FIG. 2, and FIG. 6 is a diagram illustrating the light source unit of FIG. 2. 7 is a view illustrating signal waveforms when the light source unit is driven in an analog mode and a digital mode according to an exemplary embodiment of the present invention.

As shown, the RGBW display 200 according to the embodiment of the present invention is an image display unit 210, a signal converter 220, a signal controller 230, a light source 240, a brightness control unit ( 250, and a data driver and gate drivers 260 and 270.

The image display unit 210 includes R, G, B, and W subpixels for displaying red, green, blue, and white colors, respectively, and each of the R, G, B, and W subpixels includes one pixel ( P) is achieved. Each of the R, G, B, and W sub-pixels receives the Ro, Go, Bo, and Wo output image signals and displays corresponding colors. The data wirings and the gate wirings DL and GL, which cross each other, transmit an output image signal and a scanning signal to the subpixel, respectively. Meanwhile, as illustrated in FIG. 2, the R, G, B, and W subpixels may be arranged in a stripe type along one row, and in addition, various shapes such as a quad type and the like. It can be arranged as.

When the liquid crystal display device is used as the display 200, the liquid crystal panel 211 illustrated in FIG. 3 may be used as the image display unit 210. The liquid crystal panel 211 is filled with a liquid crystal (not shown) between two substrates (not shown) facing each other, and displays an image by an electric field applied to the liquid crystal. The liquid crystal panel 211 includes a thin film transistor T positioned at a portion where data wirings and gate wirings DL and GL intersect each other to define sub-pixels, and data data and gate wirings DL and GL intersect each other. The liquid crystal capacitor C _LC connected to the thin film transistor T and the storage capacitor C _ST may be positioned as a storage capacitor.

The data driver 260 and the gate driver 270 output the output image signal and the scan signal to the data line DL and the gate line GL, respectively.

The signal converter 220 receives the Ri, Gi, and Bi input video signals and outputs Ro, Go, Bo, and Wo output video signals. The signal converter 220 may include first and second signal region converters 221 and 223 and a signal generator 222.

The first signal region converter 221 converts the signal region of the Ri, Gi, Bi input video signal output from the signal input system 300 from the L ^* signal region to the Y signal region. The first signal region conversion unit 221 may use a first signal region transformation equation, Y = (L ^* ) ^γ,. Where γ is the gamma value of the display.

The signal generator 222 converts the Ri, Gi, and Bi input video signals converted from the signal region into Ro, Go, Bo, and Wo output video signals using a signal generation algorithm. Signal generation algorithm,

(Ro, Go, Bo) = (MAX + Wo) / MAX * (Ri, Gi, Bi)-Wo

Wo = f (MIN, MAX)

You can use a conversion equation like this: Here, MIN = Min (Ri, Gi, Bi), MAX = Max (Ri, Gi, Bi).

The signal generation algorithm follows the function f (MIN, MAX), that is, the white signal generation algorithm, for generating the white output image signal Wo. The white signal generation algorithm is, for example,

Wo = MAX * MIN / (MAX-MIN) (when MAX <2 * MIN) Wo = MAX (when MAX ≥ 2 * MIN),

^{Wo = -MIN 3/255 2 +} MIN 2/255 + MIN,

Wo = MIN,

Wo = MIN ²

As described above, the first, second, third and fourth white signal generation algorithms can be used.

The second signal region converter 223 converts the signal region of the Ro, Go, Bo, and Wo output image signals output from the signal generator 222 from the Y signal region to the L ^* signal region. The second signal region conversion unit 223 may use the second signal region transformation equation, L ^* = Y ^{1 / γ} , which is an inverse function of the first signal region transformation equation.

The signal controller 230 outputs the Ro, Go, Bo, and Wo output image signals output from the signal converter 220 to the data driver 260 according to timing. Meanwhile, the signal controller 230 outputs various control signals for controlling the data driver 260 and the gate driver 270.

The brightness adjusting unit 250 adjusts the brightness I of the light emitted through the light source unit 240 by analyzing the gray level, which is an image attribute of the input image signal. The brightness adjusting unit 250 includes a gray extracting unit 251, a gray distribution calculating unit 252, an analyzing unit 253, and a light source control unit 254.

The gray level extractor 251 extracts the gray level of the input image signal during one frame. In order to extract the gradation, the gradation expression is used. For example,

G = Max (Ri, Gi, Bi)

You can use the gradation expression as Here, G is the gray level of the Ri, Gi, Bi input video signal, and Max (Ri, Gi, Bi) corresponds to the maximum value of the Ri, Gi, Bi input video signal.

Ri, Gi, Bi input video signal for displaying white color of maximum gradation H is (Ri, Gi, Bi) = (H, H, H). The gray level G = Max (Ri, Gi, Bi) = H of the signal. And, Ri, Gi, Bi input video signal for displaying black color of minimum gray level 0 is (Ri, Gi, Bi) = (0, 0, 0). The gray level G = Max (Ri, Gi, Bi) = 0 of the input video signal. Therefore, when the gray scale extraction equation is used, the gray scale of the input video signal can be extracted.

The gray scale calculation unit 252 calculates a distribution of gray scales extracted during one frame. For example, if the grayscale can range from 0 to H, the frequency of the grayscale for one frame is counted to calculate its distribution. The calculated distribution of gradations may be represented by a histogram.

The analyzing unit 253 analyzes the distribution of the gray scales calculated by the gray scale distribution calculating unit 252. For example, the analyzing unit 253 analyzes the histogram indicating the distribution of the gray scales and calculates a representative gray scale having a representative value that can represent the distribution of the gray scales, such as the mode or average value of the gray scales.

The light source controller 254 controls the luminance control signal (DS) output according to the representative gradation calculated by the analyzer 253, and the light source unit 240 controls the luminance according to the luminance control signal DS. I) emits controlled light.

The light source unit 240 may include an interleaver 241 and a lamp 242 which is a light source. The inverter 241 adjusts the power waveform output to the lamp 242 according to the brightness control signal DS, and the lamp 242 emits light whose brightness I is adjusted according to the power waveform.

The lamp 242 may be driven in an analog mode and a digital mode, as shown in FIG. 7. The analog mode is to emit light by applying an analog power to the lamp 242, the brightness control signal DS to adjust the brightness (I) of the light emitted by adjusting the amplitude (A) of the power waveform. Done. The digital mode is a burst mode, and emits light by applying a pulse type power to the lamp 242, and the luminance control signal DS is applied with a pulse in one frame F. The luminance T of the emitted light is controlled by adjusting the time T, that is, the duty on time T of the lamp.

In the above-described embodiment of the present invention, the luminance controller 250 and the signal controller 230 are configured separately, but the luminance controller 250 may be included in the signal controller 230.

8 to 10 are diagrams showing the relationship between the gray level distribution of the input image signal and the duty on time of a lamp in a dark image, a bright image, and a medium brightness image according to an exemplary embodiment of the present invention.

8 to 10, the lamp is driven in the digital mode as an example. The input image signal has 256 gray scales from 0 to 255, and the entire gray scale range is divided into first, second and third gray scale regions GS1, GS2 and GS3, and the first gray scale region GS1 is 0 to For example, the gradation range up to 20 gradations, the second gradation region GS2 has a gradation range of 20 to 230, and the third gradation region GS3 has a gradation range of 230 to 255. In addition, the case where the average gradation is used as the representative gradation is taken as an example.

As shown in FIG. 8, the gray level of the input video signal input during one frame F is entirely located in the first gray level area GS1. That is, in the gradation distribution of FIG. 8, the first representative gradation GR1 is positioned in the first gradation region GS1. Therefore, the image having the gradation distribution of FIG. 8 corresponds to the dark image as a whole. In this case, when the entire dark image is displayed, the lamp is driven during the first duty on time T1, and the emitted light has the first luminance Y1.

As shown in FIG. 9, the gray level of the input video signal input during one frame F is entirely located in the third gray level area GS3. That is, in the gradation distribution of FIG. 9, the second representative gradation GR2 is positioned in the third gradation region GS3. Therefore, the image having the gradation distribution of FIG. 9 corresponds to a bright image as a whole. In the case of displaying a bright image as a whole, the lamp is driven during the second duty on time T2, and the emitted light has the second luminance Y2.

8 and 9, the first duty on time T1 is smaller than the second duty on time T2, and thus the first luminance Y1 of the emitted light is the second luminance Y2. Small compared to Therefore, when the entire dark image is displayed as shown in FIG. 8, light of low luminance is emitted, and when the overall bright image is shown as shown in FIG. 9, light of high luminance is emitted. In particular, when the representative gradation GR is positioned in the first and third gradation regions GS1 and GS3, when the representative gradation GR increases, the duty on time T increases and the luminance Y of the light emitted is increased. ) Increases, and when the representative gradation (GR) decreases, the duty on time (T) decreases so that the luminance (Y) of emitted light decreases. Therefore, dark images become darker, bright images become brighter, dark images and bright images are more emphasized, and contrast ratios and sharpness of images are increased.

On the other hand, as shown in Fig. 10, the gray level of the input video signal input during one frame F is generally located in the first to third gray areas GS1 to GS3. That is, in the gradation distribution of FIG. 10, the third representative gradation GR3 is positioned in the second gradation region GS3. Therefore, the image having the gradation distribution of FIG. 10 corresponds to an image of medium brightness. In the case of displaying an image of medium brightness as described above, the lamp is driven for the same third duty on time T3 as one frame F, and the emitted light has the third luminance Y3.

Referring to FIG. 10 compared to FIGS. 8 and 9, the third duty on time T3 is larger than the first and second duty on times T1 and T2, and accordingly, the third luminance Y3 of the light emitted is It is larger than the first and second luminances Y1 and Y2. Accordingly, when the image of medium brightness is displayed as shown in FIG. 10, light of a higher luminance is emitted as compared with the case of displaying a dark image and a bright image as shown in FIGS. 8 and 9. It is possible to implement an image having a peak brightness. If the third brightness Y3 of the light emitted from the medium brightness image is located between the first brightness Y1 and the second brightness Y2, the medium brightness image has almost the same display characteristics as before. Rather, the overall brightness is reduced. In particular, when the brightness of the part is bright or dark, the contrast ratio or the sharpness of the image may decrease when the brightness of the emitted light is increased or decreased. Therefore, for the image of medium brightness, it is possible to realize the extreme brightness by maximizing the brightness of the emitted light.

8 to 10, the gray scale range is divided into the first to third gray scale regions GS1 to GS3 for the case of having 256 gray scale ranges from 0 to 255. Meanwhile, when the gradation range is 0 to H, the first gradation region GS1 is about 0 to 0.078H, the second gradation region GS2 is about 0.078H to 0.90H, and the third gradation region GS3 is 0.90H. It may have a gradation range of to H.

On the other hand, in the embodiment of the present invention has been described as an example of the red, green, blue as the primary color, as the primary color of the three colors of the same luminance combined to display a white color, for example, cyan (cyan), Magenta and yellow colors can be used, so C (cyan) and M (magenta) can display cyan, magenta, and yellow colors instead of the R, G, and B subpixels. , Y (yellow) subpixel can be used.

As described above, the present invention adjusts the luminance of the light emitted according to the gradation distribution of the image. Therefore, dark images become darker, bright images become brighter, dark images and bright images are more emphasized, and contrast ratios and sharpness of images are increased. In addition, it is possible to realize the extreme brightness by maximizing the luminance of the emitted light with respect to the image of the medium brightness.

Embodiment of the present invention as described above, as an example of the present invention, it is possible to change freely. It is apparent to those skilled in the art that such modifications fall within the scope of the present invention within the scope included in the spirit of the present invention.

The present invention adjusts the luminance of light emitted according to the gradation distribution of the image. Therefore, dark images become darker, bright images become brighter, dark and bright images are more emphasized, and the contrast ratio and sharpness of the images are increased. In addition, with respect to the image of the medium brightness, the maximum brightness of the emitted light can be maximized, thereby achieving the extreme brightness.

Claims (37)

A luminance controller for calculating a representative gray scale that can represent the gray scales of the first, second, and third input video signals corresponding to the first, second, and third colors; When the representative gradation is located in each of the first, second, and third gradation regions, light having first, second, and third luminance is emitted, and the second luminance is higher than the first, third luminance, and the second gradation. A region comprising a light source unit positioned between the first and third gray scale regions; Signal generation for generating first, second and third output video signals corresponding to each of the first, second and third colors and white output video signals corresponding to a white color using the first, second and third input video signals Wealth; An image display unit including first, second and third sub-pixels corresponding to the first, second and third output image signals, and a white sub-pixel corresponding to the white output image signal; Display comprising a. The method of claim 1, The brightness control unit, A gray scale extraction unit for extracting gray scales of the input image signal; A gradation distribution calculating unit calculating a distribution of the extracted gradations; An analysis unit which calculates the representative gray level by analyzing the gray level distribution Display comprising a. The method of claim 2, The representative gradation display includes an average gradation and a most frequent gradation. The method of claim 1, The gray level of the input video signal corresponds to a maximum value of the first, second, and third input video signals. The method of claim 1, The gradation of the input image signal has a range of 0 to H, the first gradation region has a range of 0 to 0.078H, the second gradation region has a range of 0.078H to 0.90H, and the third gradation region has a range of 0.90H to H. . The method of claim 5, Wherein H is 255. The method of claim 1, Wherein the third brightness is higher than the first brightness. The method of claim 1, The brightness controller includes a light source controller for controlling the brightness of the emitted light by outputting a brightness control signal to the light source according to the representative gradation. The method of claim 1, And the light source unit includes an inverter and a lamp. The method of claim 1, And the light source unit is driven in one selected from an analog mode and a digital mode. 11. The method of claim 10, When driving the light source unit in the digital mode, the light source unit has first, second and third duty on time corresponding to each of the first, second and third luminance, and the second duty on time is the Display longer than the first and third duty on times. The method of claim 1, The first and the third luminance is increased as the representative gradation located in each of the first and third gradation regions is increased. The method of claim 1, And the first, second, and third colors are one of red, green, and blue. The method of claim 1, And the first, second, and third colors are one of cyan, magenta, and yellow. The method of claim 1, A first signal region converter for converting a signal region of the input image signal and outputting the signal region to the signal generator; A second signal region changer for converting a signal region of the output image signal Display further including. The method of claim 15, And the first signal region converter converts the L * signal region into the Y signal region, and the second signal region converter converts the Y signal region into the L * signal region. The method of claim 1, And a signal controller which outputs the output image signal to the image display unit according to a timing. The method of claim 1, And the image display unit is a liquid crystal panel. The method of claim 1, And the representative gradation is calculated from the input video signal during one frame. Calculating a representative gradation that can represent the gradation of the first, second, and third input video signals corresponding to each of the first, second, and third colors; Emitting light having first, second, and third luminance when the representative gradation is located in each of the first, second, and third gradation regions; Generating first, second and third output image signals corresponding to the first, second and third colors and white output image signals corresponding to a white color using the first, second and third input image signals; ; Displaying an image using first, second, and third sub-pixels corresponding to the first, second, and third output image signals, and white sub-pixels corresponding to the white output image signal; And the second luminance is higher than the first and third luminance, and the second gradation region is located between the first and third gradation regions. The method of claim 20, The step of calculating the representative gradation, Extracting a gray level of the input image signal; Calculating a distribution of the extracted gray levels; Calculating the representative gray scale by analyzing the gray scale distribution Display driving method comprising a. The method of claim 21, The representative gradation may include a mean gradation and a most frequent gradation. The method of claim 20, And a gray level of the input image signal corresponds to a maximum value of the first, second and third input image signals. The method of claim 20, The gradation of the input image signal has a range of 0 to H, the first gradation region has a range of 0 to 0.078H, the second gradation region has a range of 0.078H to 0.90H, and the third gradation region has a range of 0.90H to H. Driving method. The method of claim 24, Wherein H is 255. The method of claim 20, And the third brightness is higher than the first brightness. The method of claim 20, And outputting a brightness control signal according to the representative gradation to adjust brightness of the emitted light. The method of claim 20, And emitting the light comprises at least one of an analog mode and a digital mode. 29. The method of claim 28, When the light is emitted in the digital mode, the light is emitted during the first, second, and third duty on time corresponding to each of the first, second, and third luminance, and the second duty on time is the same. Display driving method longer than the first, third duty on time. The method of claim 20, And the first and third luminances increase as the representative gradation located in each of the first and third gradation regions increases. The method of claim 20, And the first, second, and third colors are different from one of red, green, and blue. The method of claim 20, And the first, second, and third colors are different from one of cyan, magenta, and yellow. The method of claim 20, Converting a signal region of the input video signal before generating the output video signal; Converting a signal region of the output image signal Display driving method further comprising. The method of claim 33, wherein And the first signal region converter converts the L * signal region into the Y signal region, and the second signal region converter converts the Y signal region into the L * signal region. The method of claim 20, And outputting the output image signal to display the image according to a timing. The method of claim 20, And the display is a liquid crystal display device. The method of claim 20, And the representative gradation is calculated from the input image signal during one frame.

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