KR20140092159A - Display device and driving method thereof - Google Patents

Abstract

The present invention relates to a display device and a driving method thereof, which comprise a conversion unit for extracting luminance information from an original video signal; a video analyzing unit for calculating a luminance distribution ratio corresponding to the original video signal by analyzing the luminance information; a contrast ratio determination unit for determining a contrast ratio by a plurality of gray levels depending on the luminance distribution ratio; a contrast ratio control unit for compensating the contrast of the original video signal according to the contrast ratio and generating the compensated video signal; and a brightness control unit for adjusting and outputting the brightness of the compensated video signal in response to a control signal for a user.

Description

DISPLAY DEVICE AND DRIVING METHOD THEREOF [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device and a driving method thereof, and more particularly to an organic light emitting display device and a driving method thereof.

Typical flat panel display devices include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an organic light emitting display OLED).

Among the flat panel display devices, an organic light emitting display device using an organic light emitting diode (OLED) generally refers to a flat panel display device using electroluminescence of an organic material. The organic light emitting diode emits electrons and holes by injecting electrons and holes through a mechanism that combines injected electrons and holes through an excitation state.

Since the organic light emitting display device does not require a separate light source, it can be reduced in volume and weight, has a fast response speed, is driven at low power consumption, and has excellent luminous efficiency, luminance and viewing angle. And the like.

Since the organic light emitting display device displays an image using an organic light emitting device that is a self light emitting device and emits light according to a change in the amount of current according to an image data signal, It is necessary to reduce power consumption.

On the other hand, in general, a color model in which a mixture of red, green, and blue is displayed on a display device can be used as a method of displaying colors of an image in an organic light emitting display device. Further, a color model in which a mixture of typical cyan, magenta, and yellow of print colors is displayed on the display device can be used.

The color can be displayed using gamma-converted luminance and chrominance component signals using Y (Luminance), Cb (B-color difference), and Cr (R-color difference) signal models. In addition, a method of extracting feature vectors of an image using H (Hue), S (Saturation) and V (Value) signal models can be used. In this case, in order to drive the organic light emitting display device with low power, the image signal may be clipped during the color conversion of the image, or the maximum luminance may be limited by performing inverse conversion to RGB signals at a ratio smaller than 1.

In general, a method for driving an organic light emitting display device at a low power level uses a method of reducing the contrast or reducing the RGB value itself. Such a method may cause the saturation to increase or decrease according to the change of brightness, decrease the contrast ratio, and decrease the visibility.

Therefore, the embodiment of the present invention can prevent the phenomenon that the display is supersaturated or low-saturation by adjusting the brightness at the same time in the organic light emitting display device, can display a natural image in a state where the maximum brightness of the original image is limited, A display device capable of improving the visibility of an image and a driving method thereof are provided.

According to an embodiment of the present invention, there is provided a display apparatus including a conversion unit that extracts luminance information from an original image signal, an image analysis unit that analyzes the luminance information and calculates a luminance distribution ratio corresponding to the original image signal, A contrast ratio adjusting unit for adjusting the contrast ratio of the original image signal according to the contrast ratio to generate a corrected image signal according to the contrast ratio, And a brightness adjusting unit for adjusting the brightness of the corrected video signal and outputting the adjusted brightness signal.

Here, the conversion unit may include a luminance-color separation unit that converts the red, green, and blue gradation data of the original image signal into a luminance component and a chrominance component, and analyzes the luminance component to output the luminance information. do. The image analysis unit may divide the entire gradation range of the original image signal into a plurality of gradation periods having a predetermined range, generate a distribution ratio of pixels belonging to each gradation period as a brightness distribution graph, Is calculated.

Also, the contrast ratio determination unit may generate the contrast ratio graph using the brightness distribution graph as a correction trend line having a slope for increasing or decreasing the slope of the reference trend line for each of the gradation periods. The contrast ratio determining unit may adjust the inclination of the correction trend line so that the boundary points of the respective gradation periods are continuously connected.

The contrast ratio determination unit may calculate the change in slope of the correction trend line with respect to the slope of the reference trend line as the contrast ratio. In addition, the contrast ratio controller may correct the red, green, and blue tone data of the original image signal with the contrast ratio. Wherein the brightness controller limits the brightness of the corrected video signal to a ratio smaller than at least one.

According to another aspect of the present invention, there is provided a method of driving a display device, including the steps of extracting luminance information from an original video signal, calculating a luminance distribution ratio corresponding to the original video signal by analyzing the luminance information, Determining a contrast ratio for each of a plurality of gradation periods according to the luminance distribution ratio; generating a corrected image signal by correcting brightness and darkness of the original image signal according to the contrast ratio; And adjusting the brightness of the signal and outputting the adjusted signal.

Here, the extracting of the luminance information may include converting the red, green, and blue tone data of the original image signal into a luminance component and a chrominance component. The step of calculating the luminance distribution ratio may further include the steps of: dividing the entire gradation range of the original image signal into a plurality of gradation sections having a predetermined range; and calculating a distribution ratio of the pixels belonging to each gradation section, And a step of generating the generated signal.

The step of determining the contrast ratio may include generating a contrast ratio graph using the brightness distribution graph as a correction trend line having a slope for increasing or decreasing the slope of the reference trend line for each of the gradation periods. The step of determining the contrast ratio may include adjusting the slope of the correction trend line so that the boundary points of the respective gradation sections are continuously connected to each other.

The contrast ratio corresponds to a slope change of the correction trend line with respect to a slope of the reference trend line. The step of generating the corrected video signal may further include correcting each of the red, green, and blue tone data of the original video signal with the contrast ratio. The step of adjusting the brightness of the corrected video signal may further include limiting the brightness of the corrected video signal to a ratio of at least one.

Embodiments of the present invention relate to a display device and a driving method thereof. The brightness and contrast of an original image are adaptively adjusted according to a luminance distribution, And enhances the visibility of the original image within a limited brightness, thereby improving the visibility.

1 shows a display device according to an embodiment of the present invention.
Figure 2 illustrates one of a plurality of pixels in accordance with an embodiment of the present invention.
3 is a detailed block diagram illustrating the image processing unit 112 of the display device according to an embodiment of the present invention shown in FIG.
4 is a diagram illustrating an example of the conversion unit 1121 according to an embodiment of the present invention.
5 is a graph showing a brightness distribution graph according to an embodiment of the present invention.
FIGS. 6 and 7 are graphs showing a contrast ratio according to an embodiment of the present invention. FIG.
8 is a detailed block diagram illustrating an image processing unit 112_1 according to another embodiment of the present invention.
9 is a detailed block diagram illustrating an image processing unit 112_2 according to another embodiment of the present invention.
10 is a detailed block diagram illustrating an image processing unit 112_3 according to another embodiment of the present invention.
11 is a detailed block diagram illustrating an image processing unit 112_4 according to another embodiment of the present invention.
12 is a view for explaining the effect of the display device according to the embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention in the drawings, parts not related to the description are omitted. Like numbers refer to like parts throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between. Also, when a part is referred to as "including " an element, it does not exclude other elements unless specifically stated otherwise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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

1 is a view showing a display device according to an embodiment of the present invention.

Referring to FIG. 1, a display device 100 according to an exemplary embodiment of the present invention includes a controller 110, a scan driver 120, a data driver 130, and a display 140. Here, the controller 110 according to the embodiment of the present invention includes an image processor 112. The image processing unit 112 generates the corrected video signal R'G'B 'by adjusting the brightness and darkness of the original video signal RGB according to the luminance distribution ratio of the original video signal RGB and outputs the user control signal UC, And adjusts the brightness of the corrected video signal R'G'B 'to generate an input video signal RGB.

The original image signal RGB according to the embodiment of the present invention will be described by way of example with reference to a video signal including red (R), green (G) and blue (B) gray scale data. The user control signal UC is a signal for limiting the maximum brightness of the image displayed on the display unit 140 and can be controlled by an external user.

The control unit 110 receives the processed input image signals RGB and the synchronizing signals through the image processing unit 112 and generates first and second driving control signals CONT1 and CONT2 and a plurality of data signals. Here, the synchronizing signal includes a horizontal synchronizing signal Hsync, a vertical synchronizing signal Vsync, and a main clock signal CLK. The control unit 110 divides the input video signal RGB in units of frames according to the vertical synchronization signal Vsync and outputs the input video signals RGB in units of the scan lines S [1] to S [n] according to the horizontal synchronization signal Hsync. Generates a plurality of data signals by dividing the signals RGB and transmits the first drive control signal CONT1 and a plurality of data signals to the data driver 130. [

The scan driver 120 delivers a plurality of scan signals to the scan lines S [1] to S [n] according to the second drive control signal CONT2. The data driver 130 transfers a plurality of data signals to each of the plurality of data lines D [1] to D [m] according to the first drive control signal CONT1.

The display unit 140 includes a plurality of data lines D [1] to D [m], a plurality of scanning lines S [1] to S [n] A plurality of wirings connected to the power source VDD and VSS are formed. Each of the pixels PX according to the embodiment of the present invention may include a sub-pixel of RGB color (not shown).

2 is a diagram illustrating one of a plurality of pixels according to an embodiment of the present invention.

Referring to FIG. 2, a pixel PX according to an embodiment of the present invention is connected to an i-th scan line S [i] and a j-th data line D [j]. The pixel PX includes a switching transistor TR1, a driving transistor TR2, a capacitor C, and an organic light emitting diode OLED.

The switching transistor TR1 and the driving transistor TR2 are implemented as a PMOSFET that is a p-channel type transistor. The switching transistor TR1 includes a gate electrode connected to the scanning line S [i], a source electrode connected to the data line D [j], and a drain electrode connected to the gate electrode of the driving transistor TR2 .

The driving transistor TR2 includes a source electrode connected to the voltage VDD through a wiring, a drain electrode connected to the anode electrode of the organic light emitting diode OLED, and a data line D2 for a period during which the switching transistor TR1 is turned on. And a gate electrode to which the signal D [j] is transferred.

The capacitor C is connected between the gate electrode and the source electrode of the driving transistor TR2. The cathode electrode of the organic light emitting diode (OLED) is connected to the voltage VSS through the wiring.

When the switching transistor TR1 is turned on by the scanning signal transmitted through the scanning line S [i], the data signal transmitted through the data line D [j] is transmitted to the gate electrode of the driving transistor TR2 do. The gate electrode voltage of the driving transistor TR2 by the data signal is held by the capacitor C. [

The voltage difference between the gate electrode and the source electrode of the driving transistor TR2 is held by the capacitor C, and a driving current flows through the driving transistor TR2. And the organic light emitting diode OLED emits light according to the driving current.

FIG. 3 is a detailed block diagram illustrating an image processing unit 112 of a display device according to an embodiment of the present invention shown in FIG. 1, FIG. 4 is a block diagram illustrating an example of a conversion unit 1121 according to an embodiment of the present invention Fig. FIG. 5 is a graph illustrating a brightness distribution according to an embodiment of the present invention, and FIGS. 6 and 7 are graphs illustrating a contrast ratio graph according to an exemplary embodiment of the present invention.

3, an image processing unit 112 according to an exemplary embodiment of the present invention includes a conversion unit 1121, an image analysis unit 1123, a contrast ratio determination unit 1125, a contrast ratio control unit 1127, and a brightness control unit 1129). The converting unit 1121 receives the original image signal RGB and extracts the luminance information Y from the original image signal RGB and transmits the extracted luminance information Y to the image analyzing unit 1123 . The converting unit 1121 transmits the input original image signal RGB to the contrast ratio adjusting unit 1127. [

The converting unit 1121 according to the embodiment of the present invention extracts the luminance information Y from the original image signal RGB by using a signal model such as YCbCr, YUV, or the like. For example, as shown in FIG. 4, the conversion unit 1121 may include a luminance-color separation unit 1122. FIG. The luminance-color separation unit 112 separates the original image signal RGB into luminance and chrominance components, and analyzes the histogram of luminance components to generate luminance information Y.

The image analyzing unit 1123 analyzes the luminance information Y to generate a brightness distribution graph (Y-Histogram) corresponding to the original image signal RGB. Specifically, the image analyzing unit 1123 divides the entire gradation range indicated by the original image signal RGB into a plurality of sections, and generates a brightness distribution graph of the distribution ratios of the pixels PX belonging to each section. Although the embodiment of the present invention has been described by exemplifying the case where the entire gradation range is divided into three sections, that is, the low gradation section GB1, the relay section GB2, and the high gradation section GB3, It does not.

5, when the original image signal RGB is an 8-bit image, the image analyzing unit 1123 determines the three gradations GB1 to GB3 based on the entire gradation range of 0 to 255, . The distribution ratio of the pixels PX belonging to the low gray level section GB1 is equal to the number of all the pixels PX of the display section 140 by a and the distribution ratio of the pixels PX belonging to the relay gray level GB2 Is equal to b and the distribution ratio of the pixel PX belonging to the high gradation period GB3 is c.

The contrast ratio determining unit 1125 determines the contrast ratio for each of the low gradation, the intermediate gradation, and the high gradation period GB1 to GB3 using the brightness distribution graph, and transmits the corresponding contrast ratio to the contrast ratio adjusting unit 1127. [ The contrast ratio determining unit 1125 applies the reference trend line SL1 to the brightness distribution graph and calculates the contrast ratio of the reference trend line SL1 with respect to the slope of the reference trend line SL1 according to the distribution ratio of the pixels PX of the respective regions GB1 to GB3 The contrast ratio graph is generated by the correction trend lines (L1 to L3).

The contrast ratio determining unit 1125 adjusts the slopes of the correction trend lines L1 to L3 corresponding to the respective sections GB1 to GB3 using the reference distribution ratio of the pixels PX predetermined for each of the sections GB1 to GB3 . In the embodiment of the present invention, when the distribution ratio of the pixel PX is larger than the reference distribution line SL1, it is increased compared to the reference distribution line SL1. When the distribution ratio is smaller than the reference distribution ratio, . In addition, it is preferable to adjust the inclination so that the boundary points of the sections GB1 to GB3 are continuously connected.

6, when the distribution curve a of the pixel PX in the low gradation section GB1 is larger than the reference distribution ratio, the reference trend line SL1 is used as a reference, The slope of the correction trend line L1 of the low gradation section GB1 is corrected to be higher than the reference trendline SL1. When the distribution ratio b of pixels PX in the relay tile section GB2 is smaller than the reference distribution ratio, the slope of the correction tendency line L2 in the relay tile section GB2 is corrected to be smaller than the reference trendline SL1 . Further, when the distribution ratio c of the pixels PX in the high gradation section GB3 is larger than the reference distribution ratio, the slope of the correction trend line L3 in the high gradation section GB3 is corrected to be larger than the reference trendline SL1 .

The contrast ratio determining unit 1125 determines the periods GB1 to GB3 to which the luminance value belongs according to the luminance information Y and generates the contrast ratio information corresponding to the gradient change with respect to the luminance value. For example, as shown in FIG. 7, the contrast ratio determining unit 1125 determines that the luminance value of the input first original image signal (R1, G1, B1) is Y1 and the luminance value Y1 belongs to the low gradation period GB1 The ratio Ratio_Y1 between the luminance values Histo_Y1 changed in accordance with the slope L1 corrected based on the original luminance value Org_Y1 corresponding to the reference trend line SL1 is calculated.

Likewise, if the luminance value of the input second original image signal (R2, G2, B2) is Y2 and the luminance value Y2 belongs to the high gradation section GB3, the original luminance value Org_Y2 corresponding to the reference trendline SL3, (Ratio_Y2) between the luminance value (Histo_Y2) changed in accordance with the corrected slope (L3) on the basis of the luminance value (Histo_Y2). The contrast ratio determining unit 1125 generates the calculated ratio (Ratio_Y1, Y2) as the contrast ratio information, and transmits the ratio to the contrast ratio adjusting unit 1127. [ The contrast ratio information is expressed by the following equation (1).

[ Equation 1 ]

Ratio_Yx = Histo_Yx / Org_Yx (where x is a natural number)

The contrast ratio adjuster 1127 generates the corrected video signal R'G'B 'by correcting the contrast of the original video signal RGB according to the contrast ratio information. The contrast ratio adjusting unit 1127 corrects the input original image signal RGB by multiplying the contrast ratio calculated. The contrast ratio controller 1127 can maintain the color coordinates of the original image by applying the same contrast ratio to the red original image signal R, the green original image signal G, and the blue original image signal B, respectively .

For example, the contrast ratio controller 1127 multiplies the original image signals R1, G1, and B1 by the contrast ratio Ratio_Y1 for the first original image signals R1, G1, and B1. In this case, the contrast of the first original image signals (R1, G1, B1) belonging to the low gradation section GB1 is adjusted and output.

Likewise, the contrast ratio (Ratio_Y2) of the input second original image signals (R2, G2, B2) is multiplied by the original image signals (R2, G2, B2). In this case, the intensity of the second original image signal (R2, G2, B2) belonging to the high gradation section GB3 is adjusted and output. This can be expressed by the following equation (2).

& Quot; (2 ) & quot ;

Rx '= Rx * Ratio_Yx

Gx '= Gx * Ratio_Yx

Bx '= Bx * Ratio_Yx

The brightness adjusting unit 1129 generates the input video signal RGB by limiting the brightness ratio of the corrected video signal R'G'B 'according to the user control signal UC. Here, the brightness controller 1129 preferably limits the brightness ratio to 1 or less in order to implement a low-power display device. For example, the brightness adjusting unit 1129 may multiply the brightness of the image by multiplying the brightness adjusting constant d corresponding to the user control signal UC by the corrected video signal R'G'B '. This can be expressed by the following equation (3).

& Quot; (3 ) & quot ;

R '* d = R

G '* d = G

B '* d = B (where 0 <d? 1)

FIG. 8 is a detailed block diagram illustrating an image processing unit 112_1 according to another embodiment of the present invention.

8, an image processing unit 112_1 according to another embodiment of the present invention includes a converting unit 1121, an image analyzing unit 1123, a contrast ratio determining unit 1125, a contrast ratio adjusting unit 1127, A frame memory 1129, and a frame memory 1131. Here, the converting unit 1121, the image analyzing unit 1123, the contrast ratio determining unit 1125, the contrast ratio adjusting unit 1127, and the brightness adjusting unit 1129 are the same as those shown in FIG. 2, A detailed description will be omitted. The frame memory 1131 stores the input video signal RGB in frame units. In this case, the control unit 110 displays the image on the display unit 140 using the input image signal RGB separated in units of frames.

FIG. 9 is a detailed block diagram illustrating an image processing unit 112_2 according to another embodiment of the present invention. The image processing unit 112_2 shown in FIG. 9 stores the input image signal RGB on a frame basis in the frame memory 1131 in the configuration of the image processing unit 112_1 in FIG. 8, There are differences in configuration.

10 is a detailed block diagram illustrating an image processing unit 112_3 according to another embodiment of the present invention. The image processing unit 112_3 shown in FIG. 10 stores the corrected video signal R'G'B 'on a frame basis in the frame memory 1131 in the configuration of the video processing unit 112_1 of FIG. 8, (1129).

11 is a detailed block diagram illustrating an image processing unit 112_4 according to another embodiment of the present invention. The image processor 112_4 shown in Fig. 11 converts the original image signal RGB and luminance information Y received from the converting unit 1121 into the frame memory 1131 in the configuration of the image processor 112_1 of Fig. (RGB) to the contrast ratio adjusting unit 1127, and transmits the luminance information Y to the image analyzing unit 1123. The image processing unit 1123 of FIG.

12 is a view for explaining the effect of the display device according to the embodiments of the present invention.

Referring to FIG. 12, when the original image 200 is displayed at a low power of about 80%, the image 200a merely linearly decreases the RGB grayscales to cause a reduction in color saturation and a decrease in saturation. In contrast, the image 200b according to the embodiment of the present invention has improved visibility compared to the image 200a.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

110:
120:
130: Data driver
140:

Claims (16)

A conversion unit for extracting luminance information from an original video signal;
An image analyzer for analyzing the luminance information and calculating a luminance distribution ratio corresponding to the original image signal;
A contrast ratio determining unit that determines a contrast ratio for each of a plurality of gradation periods according to the luminance distribution ratio;
A contrast ratio adjusting unit for adjusting the contrast of the original image signal according to the contrast ratio to generate a corrected image signal; And
A brightness adjusting unit for adjusting the brightness of the corrected video signal according to a user control signal,
. The method according to claim 1,
The conversion unit
And a luminance-color separation unit for converting the red, green, and blue gradation data of the original image signal into luminance components and chrominance components, and analyzing the luminance components to output the luminance information. The method according to claim 1,
The image analysis unit
And the luminance distribution ratio is calculated by dividing the entire gradation range of the original video signal into a plurality of gradation intervals having a predetermined range and generating a distribution ratio of pixels belonging to each gradation interval as a brightness distribution graph, / RTI &gt; The method of claim 3,
The contrast ratio determining unit
Wherein the brightness distribution graph is used to generate a contrast ratio graph as a correction trend line having a slope for increasing or decreasing a slope of a reference trend line for each of the gradation sections using the brightness distribution graph. 5. The method of claim 4,
The contrast ratio determining unit
And adjusts the slope of the correction trend line so that the boundary points of the respective gradation sections are continuously connected to each other. 5. The method of claim 4,
The contrast ratio determining unit
And calculates the change in slope of the correction trend line with respect to the slope of the reference trend line as the contrast ratio. 3. The method of claim 2,
The contrast ratio controller
And corrects each of the red, green, and blue tone data of the original video signal by the contrast ratio. The method according to claim 1,
The brightness adjusting unit
And the brightness of the corrected video signal is limited to a ratio smaller than at least one. Extracting luminance information from an original video signal;
Analyzing the luminance information and calculating a luminance distribution ratio corresponding to the original image signal;
Determining a contrast ratio for each of a plurality of gradation periods according to the luminance distribution ratio;
Generating a corrected video signal by correcting brightness and darkness of the original video signal according to the contrast ratio; And
Adjusting the brightness of the corrected video signal according to a user control signal and outputting
And a driving method of the display device. 10. The method of claim 9,
The step of extracting the luminance information
And converting the red, green, and blue gradation data of the original image signal into a luminance component and a chrominance component. 10. The method of claim 9,
The step of calculating the luminance distribution ratio
Dividing the entire gradation range of the original image signal into a plurality of gradation intervals having a predetermined range; And
A step of generating distribution ratios of the pixels belonging to each of the gradation periods as a brightness distribution graph
And a driving method of the display device. 12. The method of claim 11,
The step of determining the contrast ratio
And generating a contrast ratio graph by using the brightness distribution graph as a correction trend line having a slope for increasing or decreasing a slope of a reference trend line for each of the gradation periods. 13. The method of claim 12,
The step of determining the contrast ratio
And adjusting a slope of the correction trend line so that boundary points of the respective gradation sections are continuously connected to each other. 13. The method of claim 12,
Wherein the contrast ratio corresponds to a slope change of the correction trend line with respect to a slope of the reference trend line. 11. The method of claim 10,
The step of generating the corrected video signal
And corrects each of the red, green, and blue tone data of the original video signal by the contrast ratio. 10. The method of claim 9,
The step of adjusting the brightness of the corrected video signal and outputting
Wherein the brightness of the corrected video signal is limited to a ratio smaller than at least one.

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