KR101927862B1 - Image display device and method of driving the same - Google Patents

Abstract

According to another aspect of the present invention, Changing a luminance of the input video signal according to a color coordinate to output a modulated video signal; Generating a data signal from the modulated image signal; And displaying the image using the data signal, wherein the luminance of the input image signal corresponding to the cyan, magenta, and blue color coordinates is lowered to output the modulated image signal, to provide.

Description

TECHNICAL FIELD [0001] The present invention relates to a video display device and a driving method thereof.

The present invention relates to a video display device, and more particularly, to a video display device having a high luminance and a low power consumption and a driving method thereof.

2. Description of the Related Art As an information society has developed, there has been an increasing demand for a display device for displaying images. Recently, a liquid crystal display (LCD), a plasma display panel (PDP) Various flat panel displays (FPDs) such as an organic light emitting diode display (OLED display) have been utilized.

In general, a flat panel display includes a plurality of pixels arranged in a matrix, and each pixel is composed of red, green, and blue subpixels. The three colors from each sub-pixel are combined to determine one color, and the flat panel display displays the desired image by controlling the luminance of each sub-pixel.

However, flat panel displays that display images by such red, green, and blue sub-pixels have limitations on brightness and power consumption of the displayed image.

In order to improve this, a method of increasing the brightness of an image by adding white subpixels in addition to red, green, and blue subpixels to display images by four color subpixels has been proposed. However, in the flat panel display device including such a four-color sub-pixel, a drive for displaying a color using only two of the three primary colors of red, green, and blue, i.e., yellow, cyan, or magenta There is a drawback that the voltage is high and the power consumption is large.

This will be described in more detail with reference to FIG.

1 is a diagram showing the power consumption required for displaying the maximum luminance in a flat panel display device including four color subpixels on a chromaticity diagram of CIE (International Commission on Illumination).

In this case, the triangle in FIG. 1 represents the gamut of the sRGB color space, and the end point of the triangle represents the red, green, and blue primaries of the sRGB color space. Here, the sRGB color space is a standard RGB color space created by the cooperation of the American computer company Microsoft and HP in 1996, and the sRGB color gamut is the high definition television (HDTV) standard ITU-R BT. 709, the color temperature of white is 6500K, and gamma is designated as 2.2.

For example, the color coordinates of the red, green, and blue sub-pixels are made the same as the red, green, and blue primary colors of sRGB, the color coordinates of the white sub-pixel are set to (0.3, 0.3), and the white color coordinates are set to (0.3127, 0.3290) , And the luminous efficiencies of red, green, blue, and white subpixels are assumed to be 5 cd / A, 20 cd / A, 2.5 cd / A, and 50 cd / A, respectively. At this time, when the white luminance is 500 cd / m < ² >, the power consumption by the color coordinates in the 45-inch display device is as shown in Fig. 1. The closer the color coordinates are to the white sub-pixel, the lower the power consumption, It can be seen that the power consumption is higher.

In order to lower the total power consumption, the luminance of the region where the power consumption is high can be lowered. However, in this case, there is a difference between the luminance lowering region and the lower luminance region in the color space.

Fig. 2 is a graph showing the ratio of the maximum luminance to each color coordinate when the power consumption is limited to 25 W on the CIE chromaticity diagram, with the sRGB gamut as a reference.

As shown in Fig. 2, when the power consumption is limited, continuity of the luminance change is deteriorated. Therefore, the image quality deteriorates.

An object of the present invention is to provide an image display apparatus and a driving method thereof that can improve brightness and power consumption while maintaining image quality.

According to an aspect of the present invention, there is provided an image processing method comprising: inputting an input video signal; Changing a luminance of the input video signal according to a color coordinate to output a modulated video signal; Generating a data signal from the modulated image signal; And displaying the image using the data signal, wherein the luminance of the input image signal corresponding to the cyan, magenta, and blue color coordinates is lowered to output the modulated image signal, to provide.

The step of outputting the modulated image signal may include: calculating a gray level of the input image signal; Calculating the color coordinate xy and the luminance Y from the gradation of the input video signal; And decreasing or outputting the luminance of the input video signal according to the color coordinates.

The step of calculating the color coordinate xy and the luminance Y includes the steps of obtaining an XYZ tristimulus value from the grayscale of the input video signal and calculating the color coordinate xy and the luminance Y from the XYZ tristimulus value.

The step of lowering or outputting the luminance of the input video signal according to the color coordinates may further comprise the steps of: 0.24? A? 0.27, 0.17? B? 0.2, 2.4? C? 2.7, 4.5? D? Calculating an f value satisfying f = a - by - cxy + dx ³ y + exy ⁴ using a, b, c, d and e in the range of 4.5? E? 4.8; Determining whether the f value is greater than zero; The f value is greater than zero, the luminance Y and Y the input video signal from a '= Y / 10 ^f corrected luminance Y satisfying "the color coordinates xy and the corrected luminance Y', and calculated from the f-number Changing the gradation of the input image signal if the f value is not greater than 0; And outputting the modulated input image signal with the gradation changed or the input image signal with the gradation unchanged as the modulated image signal.

The luminance of the input image signal corresponding to the color coordinates of green and yellow is the same as the luminance of the modulated image signal.

The step of generating the data signal may include generating an output video signal from the modulated video signal and generating the data signal from the output video signal, wherein the modulated video signal is an RGB three-color signal, The output video signal is an RGBW four-color signal.

According to another aspect of the present invention, there is provided a display device comprising: a display panel including a plurality of pixels and displaying an image; A data modulator for modulating the brightness of the input image signal according to the color coordinates to output a modulated image signal; And a data driver for generating a data signal from the modulated image signal and supplying the data signal to the display panel, wherein the data modulator lowers the luminance of the input image signal corresponding to cyan, magenta, A video display device for outputting a signal is provided.

The data modulator includes an arithmetic unit for calculating the color coordinate xy and the luminance Y by calculating a gray level of the input video signal and a modulator for lowering or outputting the luminance of the input video signal according to the color coordinates.

The arithmetic operation section obtains an XYZ tristimulus value from the grayscale of the input video signal, and calculates the color coordinate xy and the luminance Y from the XYZ tristimulus value.

Wherein the data modulating unit is configured to calculate the color coordinates xy from a, b, c, and d in the range of 0.24? A? 0.27, 0.17? B? 0.2, 2.4? C? 2.7, 4.5? D? , e is used to calculate an f value satisfying f = a - by - cxy + dx ³ y + exy ⁴ , and judges whether the f value is greater than 0, calculating the luminance Y and 'corrected luminance Y satisfying a = Y / 10 ^f' Y from the f value, and changes the gray level of the input video signal from the color coordinates xy and the corrected luminance Y ', wherein the f-number And outputs the modulated video signal as the input video signal in which the gradation is changed or the input video signal in which the gradation is not changed, without changing the gradation of the input video signal.

The image display apparatus of the present invention further includes a data conversion unit for generating an output image signal from the modulated image signal and supplying the generated image signal to the data driver, wherein the modulated image signal is an RGB three-color signal, and the output image signal is RGBW 4 Color signal.

In the video display device according to the present invention, by reducing the luminance of a specific color in consideration of human visual characteristics, power consumption and power supply voltage can be lowered while maintaining image quality.

At this time, colors can be implemented from the four color sub-pixels of red, green, blue, and white, and the luminance can also be improved.

1 is a diagram showing the power consumption required for displaying the maximum luminance in a flat panel display device including four color subpixels on a CIE chromaticity diagram.
2 is a graph showing the ratio of the maximum luminance to each color coordinate when the power consumption is limited to 25 W on the CIE chromaticity diagram.
3 is a schematic view of an organic electroluminescent display device according to an embodiment of the present invention.
4 is a diagram schematically showing a data modulator according to an embodiment of the present invention.
5 is a flowchart illustrating a data modulation process according to an embodiment of the present invention.
6 is a diagram showing a luminance ratio when the luminance is adjusted by the data modulation method according to the present invention on a CIE chromaticity diagram

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

3 is a schematic view of an organic electroluminescent display device according to an embodiment of the present invention.

3, the organic EL display device 110 includes a display panel 120, a gate driver 130, a data driver 140, a timing controller 150, A data transformation unit 160, and a data modulation unit 170. The data transformation unit 170 transforms the transformed data to transformed data.

The display panel 120 includes a plurality of gate lines GL1 to GLm, a plurality of data lines DL1 to DLn, and a plurality of power lines PL1 to PLn.

A plurality of gate lines GL1 to GLm, a plurality of data lines DL1 to DLn and a plurality of power lines PL1 to PLn intersect each other to define a plurality of pixel regions P. [ The display panel 120 may include red, green, blue, and white sub-pixels as one unit pixel, and each of the red, green, blue, and white sub-pixels corresponds to one pixel region P.

In each pixel region P, a switching transistor Ts, a driving transistor Td, a storage capacitor Cst, and a light emitting diode Del are formed.

The switching transistor Ts is connected to each of the plurality of gate lines GL1 to GLm and the plurality of data lines DL1 to DLn respectively and the driving transistor Td and the storage capacitor Cst are connected to the switching transistor Ts, Is connected between the wirings PL1 to PLn, and the light emitting diode Del is connected to the driving transistor Td.

The anode of the light emitting diode Del of each pixel region P receives the power supply voltage VDD through the power lines PL1 to PLn and the cathode receives the ground voltage VSS.

The data modulator 170 receives the input image signal RGB supplied from the external system and outputs the modulated image signal R'G'B '. At this time, the data modulator 170 does not change or change the gradation of the input image signal RGB according to human visual characteristics. Accordingly, the output modulated image signal R'G'B 'may have the same gray level as the input image signal RGB or have different gray levels. This will be described in detail later.

The data converting unit 160 receives the three-color modulated image signal R'G'B 'output from the data modulating unit 170 and converts the modulated image signal R'G'B' into a four-color output image signal RGBW. Various methods can be applied to convert a three-color video signal to a four-color video signal.

The timing controller 150 rearranges the output image signals RGBW supplied from the data converter 160 according to the resolution of the display panel 120 and supplies the rearranged image signals RGBW to the data driver 140. [ The timing controller 150 receives a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, and a data enable signal Data from outside through a Low Voltage Differential Signaling (LVDS) or a Transition Minimized Differential Signaling (TMDS) The gate driver 130 and the data driver 140 generate a gate control signal GCS and a data control signal DCS using the control signals such as Enable and DE and a clock signal CLK, Respectively. The gate control signal GCS includes a gate output enable signal, a gate shift clock signal and a gate start pulse signal and the data control signal DCS includes A source start pulse signal, a source output enable signal, and a source sampling clock signal. Here, the source start pulse signal and the source sampling clock signal may be omitted depending on the data transmission method.

The gate driver 130 generates gate signals using a plurality of gate control signals GCS and supplies the generated gate signals to the plurality of gate lines GL1 to GLm of the display panel 120. [ The data driver 140 generates a data signal using an output video signal RGBW and a plurality of data control signals DCS and supplies the generated data signal to the data lines DL1 to DLn of the display panel 120. [ DLn.

Although not shown, the organic EL display device 110 of the present invention includes a power supply voltage unit and supplies a power voltage to the gate driver 130 and the data driver 140.

Although the data modulator 170 and the data converter 160 are described as being separate from the timing controller 150 in the above description, the timing controller 150 controls the data modulator 170 and the data converter 160 And may include only the data conversion unit 160. [0050]

When the switching transistor Ts is sequentially turned on in response to a gate signal applied to the plurality of gate lines GL1 to GLm, The data signal applied to the data lines DL1 to DLn is applied to the gate electrode of the driving transistor Td and one electrode of the storage capacitor Cst through the switching transistor Ts.

The driving transistor Td is turned on in accordance with the data signal applied to the gate electrode so that a current proportional to the data signal is applied to the driving transistor Td by the power supply voltage VDD applied to the plurality of power lines PL1 to PLn, (Td), and the light emitting diode (Del) emits light at a luminance proportional to the current flowing through the driving transistor (Td).

At this time, the storage capacitor Cst is charged with a voltage proportional to the data signal so that the voltage of the gate electrode of the driving transistor Td is kept constant during one frame.

Accordingly, the organic EL display device 110 can display a desired image by a gate signal and a data signal.

The organic electroluminescent display device according to the present invention is characterized in that the modulated image signal R'G'B 'is output from the input image signal RGB by the data modulator 170 in consideration of human visual characteristics.

The human being feels a higher color saturation than the real one, which is called the Helmholtz-Kohlrausch effect (HK effect). P. K. Kaiser, "Models of Heterochromatic Brightness Matching," CIE Journal 5, pp. 57-59 (1986), the HK effect k for the CIE color coordinate xy can be expressed by the following equation (1).

k = 10 ^{f -} Equation (1)

Where f = 0.256 - 0.184 y - 2.527 x + 4.456 x ³ y + 4.657 x ⁴ .

These k values are low in yellow and high in blue. Accordingly, the luminance of the input image signal RGB is lowered to the region where the k value is high to reduce the power consumption. However, the human vision feels higher than the actual luminance, so that the image quality does not deteriorate.

4 is a diagram schematically showing a data modulator according to an embodiment of the present invention.

4, the data modulator 170 includes an arithmetic unit 172, a determination unit 174, and a modulation unit 176. [

The operation unit 172 calculates the gradation of the input image signal RGB and calculates the color coordinates x and y and the luminance Y from the gradation of the input image signal RGB. At this time, the color coordinates (x, y) and luminance (Y) of the input image signal RGB can be calculated from the XYZ tristimulus value after first obtaining the tristimulus value from the grayscale of the input image signal RGB have. XYZ tristimulus values are based on the light-object-sense, which is the basic three elements of color, and mean color (X), brightness (Y) and saturation (Z), respectively.

More specifically, the XYZ tristimulus value can be obtained from the matrix shown in the following equation (2), and xyY can be obtained from the equation shown in the following equation (3).

--------------- 식(2)

--------------- Equation (2)

--------------- 식(3)

--------------- Equation (3)

 The arithmetic unit 172 calculates the f value from the color coordinate (x, y) and calculates the corrected luminance Y 'from the luminance (Y) and the f value when adjustment of the luminance (Y) . At this time, the correction luminance Y 'can be expressed by the following equation (4).

Y '= Y / 10 ^f - (4)

The determination unit 174 determines whether the f value calculated by the operation unit 172 is greater than zero. Here, when the f value is not larger than 0, the gradation of the input image signal RGB is outputted unchanged. If the f value is larger than 0, the arithmetic operation unit 172 adjusts the luminance Y.

The modulating unit 176 inputs the corrected brightness Y 'from the color coordinates (x, y) and the corrected brightness Y' when the determining unit 174 determines that the f value is greater than 0 and calculates the corrected brightness Y ' The gradation of the video signal RGB is changed and output.

The structure of the data modulator 170 of the present invention is not limited to the above example, and can be changed to another structure capable of performing the same function.

5 is a flowchart illustrating a data modulation process according to an embodiment of the present invention. Referring to FIG. 5, a data modulation process in the data modulation unit will be described in detail.

As shown in Fig. 5, in the first step S210, an input video signal RGB is input from an external system (not shown) to the data modulation unit 170 (Fig. 4).

Next, in the second step S220, the gradation of the input image signal RGB is calculated.

Next, in the third step S230, the chromaticity coordinates and the luminance value xyY are calculated from the gradation of the calculated input image signal RGB. At this time, the XYZ tristimulus value can be obtained first from the grayscale of the input image signal (RGB), and then the xyY value can be calculated from the XYZ tristimulus value, and the above-mentioned equations (2) and (3) can be used.

Next, in the fourth step S240, the f value for the HK effect is calculated from the chromaticity coordinates (x, y). In this case, f = a - by - cxy + dx + exy ³ y ^4, and, a, b, c, d , e are each 0.24≤a≤0.27, 0.17≤b≤0.2, 2.4≤c≤2.7, 4.5≤d ≪ / = 4.8, 4.5 < / = e < / = 4.8.

Here, the second to fourth steps S220 to S240 are performed in the operation section (172 in Fig. 4) of the data modulation section (170 in Fig. 4).

In a fifth step S250, it is determined whether the calculated f value is greater than zero. If the calculated f value is greater than 0, the corrected brightness Y 'of the input image signal RGB is calculated in a sixth step S260. At this time, the correction luminance Y 'can be calculated from the luminance Y and the f value of the input image signal RGB by equation (4), and the correction luminance Y' is smaller than the luminance Y. [ The sixth step S260 is performed in the operation section (172 in Fig. 4) of the data modulation section (170 in Fig. 4). Next, in step 7-1 (S272), the gradation of the input video signal RGB is changed from the chromaticity coordinates (x, y) and the corrected luminance Y '.

On the other hand, if the f value is not larger than 0 in the fifth step S250, the gradation of the input video signal RGB is not changed in the seventh step S274. For example, in the yellow and green color coordinates, the f value becomes smaller than 0, so that the gradation of the input image signal RGB is not changed.

4). The seventh step S272 and the seventh step S274 are performed in the data modulating unit 170 of FIG. 4 (step 174 in FIG. 4) And is performed in the modulation section (176 in Fig. 4) of the modulation section (170 in Fig. 4).

Next, in the eighth step S280, the input video signal RGB in which the gradation in the 7-1th step S272 is changed or the input video signal RGB in which the gradation in the 7-2th step S274 is unchanged And outputs it as a modulated image signal (R'G'B ').

For example, when the color coordinates of the sRGB color space are used and the white luminance is fixed, a subjective luminance such as white can be obtained even when the red luminance is 0.794 times the maximum luminance and the blue luminance is 0.597 times the maximum luminance.

In the data modulation method according to the present invention, the brightness is adjusted in consideration of human visual characteristics, so that the image quality is not deteriorated.

FIG. 6 is a diagram showing the luminance ratio when the luminance is adjusted by the data modulation method according to the present invention on the CIE chromaticity diagram. FIG.

As shown in FIG. 6, it can be seen that the luminance of the input video signal whose color coordinates correspond to cyan, magenta and blue is lowered and the luminance of the input video signal whose color coordinate corresponds to red is also lowered. On the other hand, the luminance of the input video signal corresponding to the color coordinates of green and yellow does not change. Therefore, the luminance in cyan and magenta, which requires high power consumption, is lowered, and the power consumption is improved. In addition, even if the luminance of a specific color is adjusted, the luminance in the color space is continuously changed, so that the deterioration of image quality can be prevented.

The data modulation method according to the present invention, that is, the brightness adjustment may be applied to an area having a certain area, and the brightness may not be adjusted when the color is different in an area smaller than a specific value. Specifically, when the color coordinates of adjacent pixels are compared and the difference is greater than a predetermined value, it may not be applied. If the sum of the RGB gradation differences of adjacent pixels is 50 or more, the luminance may not be adjusted. For example, when the gradation of the first pixel is R1G1B1 and the gradation of the second pixel is R2G2B2 in adjacent first and second pixels, the sum of the RGB gradation differences of the two pixels is | R1-R2 | + | G1-G2 | + | B1-B2 |.

This non-use of data modulation can be judged between the second step S220 and the third step S230 in FIG.

Although the organic electroluminescent display device has been described in the embodiments of the present invention, the present invention is also applicable to other image display devices such as a liquid crystal display device and a plasma display device.

The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

110: video display device 120: display panel
130: Gate driver 140: Data driver
150: timing control unit 160: data conversion unit
170: Data modulation section

Claims (13)

delete delete delete delete delete delete A display panel including a plurality of pixels and displaying an image;
A data modulator for modulating the brightness of the input image signal according to the color coordinates to output a modulated image signal;
A data driver for generating a data signal from the modulated video signal and supplying the data signal to the display panel,
Lt; / RTI >
Wherein the data modulator reduces the luminance of the input video signal corresponding to cyan, magenta, and blue when the sum of the RGB gradation differences of adjacent pixels is less than 50, and outputs the modulated video signal, .
8. The method of claim 7,
Wherein the data modulator comprises: an arithmetic unit for calculating the color coordinate xy and the luminance Y by calculating the grayscale of the input video signal; and a modulator for lowering or outputting the luminance of the input video signal according to the color coordinates Device.
9. The method of claim 8,
Wherein the arithmetic operation section obtains an XYZ tristimulus value from the grayscale of the input video signal and calculates the color coordinate xy and the luminance Y from the XYZ tristimulus value.
9. The method of claim 8,
Wherein the data modulating unit is configured to calculate the color coordinates xy from a, b, c, and d in the range of 0.24? A? 0.27, 0.17? B? 0.2, 2.4? C? 2.7, 4.5? D? , e is used to calculate an f value that satisfies f = a - by - cxy + dx ³ y + exy ⁴ , and determines whether the f value is greater than 0,
The f value is greater than zero, the luminance Y and Y the input video signal from a '= Y / 10 ^f corrected luminance Y satisfying "the color coordinates xy and the corrected luminance Y', and calculated from the f-number And when the f value is not greater than 0, the gradation of the input video signal is not changed,
And outputs the input image signal with the gradation changed or the input image signal with the gradation unchanged as the modulated image signal.
8. The method of claim 7,
And a data converter for generating an output image signal from the modulated image signal and supplying the output image signal to the data driver, wherein the modulated image signal is an RGB three-color signal and the output image signal is an RGBW four-color signal.
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