KR20100012965A - Image data processing apparatus having function of adjusting luminance of backlight according to input image data, liquid crystal display, and method of driving the same - Google Patents

Abstract

PURPOSE: An image data processing device, an LCD including the same and a driving method thereof are provided to reduce power consumption of the LCD by decreasing the brightness of a backlight according to input video data. CONSTITUTION: An image data processing unit generates a backlight driving signal(27) for driving a backlight comprised of a plurality of respective partial areas based on an input video data(21). The image data processing unit generates image data(23) which is a result of changing the brightness of the input video data based on the backlight data. An LCD panel displays an image corresponding to changed image data. A backlight unit controls the brightness of the backlight based on the backlight driving signal and supplies a backlight with adjusted brightness to the LCD panel. The image data processing unit includes a storage unit(110) providing input video data of one frame after receiving data and a signal generating unit(140) generating backlight driving signal.

Description

Image data processing apparatus having a backlight brightness control function according to input image data, a liquid crystal display device having the same and a method of driving the liquid crystal display device {Image data Processing Apparatus having function of adjusting luminance of backlight according to input image data, Liquid Crystal Display, and Method of driving the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to an image data processing apparatus having a backlight brightness control function according to input image data, a liquid crystal display having the same, and a method of driving the liquid crystal display.

Among the display devices, liquid crystal displays have advantages of thinning and low power consumption, and are widely used for displaying images in laptop computers, monitors, TVs, and the like. In particular, an active matrix liquid crystal display device using a thin film transistor (hereinafter referred to as "TFT") as a switch element is suitable for displaying a dynamic image.

In general, a liquid crystal display device is largely divided into a liquid crystal pixel unit and a driver.

The liquid crystal pixel unit includes a lower glass substrate on which pixel electrodes and a thin film transistor (TFT) are arranged in a matrix, an upper glass substrate on which a common electrode and a color filter layer are formed, and a liquid crystal layer filled between the upper and lower glass substrates. do. A plurality of data lines are arranged in a first direction in the liquid crystal pixel portion, and a plurality of scan lines are arranged in a second direction substantially perpendicular to the first direction.

The driving unit processes an image signal input from an external graphic card or the like and outputs a composite synchronization signal, and receives a composite synchronization signal output from the image signal processor and receives a horizontal synchronization signal and a vertical synchronization signal. A timing controller for separating and outputting a signal and controlling timing according to a mode selection signal, a data driver for supplying a data signal to the data line based on a control signal output from the timing controller, and the timing controller And a gate driver for sequentially applying a driving voltage to the scan line based on a control signal output from the same. The conventional liquid crystal display further includes a lamp unit for supplying a backlight to the liquid crystal display panel and a lamp driver for driving the lamp unit. The lamp driver receives a dimming control signal from the timing controller to drive the lamp unit to control the brightness of the lamp unit.

However, in the conventional liquid crystal display device, since the backlight supplied to the liquid crystal display panel is turned on at the maximum luminance regardless of the image data input, the liquid crystal display device consumes a lot of power.

Accordingly, a first object of the present invention is to solve the above problems of the prior art, and provides an image data processing apparatus for minimizing degradation of display quality of an image while reducing luminance of a backlight according to input image data. Its purpose is to.

A second object of the present invention is to provide a liquid crystal display device having the image data processing device.

In addition, a third object of the present invention is to provide a method of driving a liquid crystal display device for minimizing degradation of display quality of an image while reducing luminance of a backlight according to input image data.

In order to achieve the first object of the present invention, an image data processing apparatus for providing a backlight driving signal for adjusting a brightness of a backlight according to an aspect of the present invention to a liquid crystal display panel may receive input image data from an external source. A backlight driving signal generator configured to separate the input image data into a plurality of divided regions, and generate a backlight driving signal for driving the backlight for each of the divided plurality of divided regions, and a boundary surface of the divided plurality of regions. And a converted image data generation unit configured to generate converted image data obtained by converting the luminance of the input image data based on the backlight data having the gray level corrected by the predetermined gray level per pixel, and provide the converted image data to the liquid crystal display panel. The image data processing apparatus may further include a storage unit configured to receive and provide one frame of input image data, wherein the input image data is a digital value of n (natural numbers) bits representing 2 ⁿ gray levels. The backlight driving signal generator may include an initial value extractor configured to obtain an initial value corresponding to a ratio of pixels having a luminance equal to or greater than a predetermined gray level among the input image data of the one frame stored in the storage, and the input image data of the one frame. And a backlight driving signal calculator configured to generate a backlight driving signal for driving the backlight for each of the plurality of divided regions. The backlight driving signal calculating unit obtains a maximum value and an average value of input image data in units of pixels for each of the plurality of divided regions, and the difference value is the difference value, wherein the difference value is a luminance difference value between the maximum value and the average value. The backlight driving signal is generated by adding a value multiplied by a change rate, and the change rate is expressed by the following equation.

(1-initial value) X (difference value / 2 ⁿ ) + initial value

Can be obtained by The converted image data generation unit generates a boundary data corrector for generating backlight data by correcting a gray level near the boundary of the divided regions by a predetermined gray level value per pixel, and adjusts the luminance of the input image data based on the backlight data. The image data converter may generate the converted converted image data. The boundary plane correcting unit corrects a gray level near the boundary plane by a predetermined gray level per pixel in the vertical direction near the boundary plane of the plurality of divided areas to correct the diagonal effect between the plurality of divided areas. The backlight data may be generated by correcting the gray level near the boundary surface by a predetermined gray level per pixel in the horizontal direction near the boundary surface of the regions of the pixel. The image data converter may generate the converted image data by increasing the luminance of the input image data by the amount of decrease of the backlight data.

In addition, the liquid crystal display according to an aspect of the present invention for achieving the second object of the present invention generates a backlight driving signal for driving the backlight for each of the plurality of divided regions based on the input image data, An image data processor configured to generate converted image data in which brightness of the input image data is converted based on backlight data obtained by correcting a gray level of a boundary of a plurality of divided regions by a predetermined gray level per pixel; And a backlight unit for supplying the brightness-adjusted backlight to the liquid crystal display panel by adjusting the brightness of the backlight based on the backlight driving signal.

In addition, the liquid crystal display device driving method according to an aspect of the present invention for achieving the third object of the present invention is the input image data of one frame, wherein the input image data is of the n (natural number) bits representing 2 ⁿ gray scales Dividing the digital value into a plurality of divided regions to generate a backlight driving signal for driving a backlight for each of the divided plurality of divided regions, and setting a gray level of a boundary of the divided plurality of regions to a predetermined gray level per pixel. Generating converted image data in which brightness of the input image data is converted based on the backlight data corrected for each time, and adjusting the brightness of the backlight based on the backlight driving signal to display the brightness-adjusted backlight with a liquid crystal display panel. Supplying the converted image data to the liquid crystal display panel; Displaying an image corresponding to the image data.

 As described above, according to the present invention, the luminance of the backlight may be reduced while reducing the display quality of the image according to the input image data.

In addition, there is an advantage that can significantly reduce the power consumption of the liquid crystal display device while minimizing the degradation of the display quality of the image.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and, unless expressly defined in this application, are construed in ideal or excessively formal meanings. It doesn't work.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the same reference numerals will be used for the same means regardless of the reference numerals in order to facilitate the overall understanding.

1 is a block diagram illustrating a configuration of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 10, a backlight unit, and an image data processor 100. The backlight unit includes a backlight 30 and a backlight controller 40.

The backlight unit adjusts the brightness of the backlight based on the backlight driving signal 27 from the image data processor 100 to supply the brightness-controlled backlight to the liquid crystal display panel 10.

The image data processor 100 generates a backlight driving signal for driving the backlight 30 for each of the plurality of divided regions based on the input image data 21 input from the outside such as a graphic memory. The image data processor 100 converts the luminance of the input image data 21 based on the backlight data after generating backlight data by correcting the grays of the boundary of the divided regions by predetermined grays per pixel. Image data is generated and provided to the liquid crystal display panel 10.

The liquid crystal display panel 10 includes a pixel unit 1, a data driver 4, and a gate driver 6. The liquid crystal display panel 10 receives the converted image data 23 and displays an image corresponding to the converted image data 23.

The gate driver 6 includes a plurality of scan line signals G1, G2,..., Gn-1, and Gn for selecting at least one of the plurality of scan lines in response to the scan control signal 25. Provided by (1). The data driver 4 receives the converted image data 23 from the image data processor 100 and receives the image data signal through the plurality of data lines D1, D2,..., Dn-1, Dn. Provided by (1).

In the pixel unit 1, liquid crystal pixels including a thin film transistor connected to the data line and the scan line are formed in a matrix. Image data applied to the data line is input to the liquid crystal pixel by switching the thin film transistor by a scan line signal applied to the scan line.

FIG. 2 is a block diagram illustrating a detailed configuration of the image data processing unit of FIG. 1, and FIG. 8 is a flowchart illustrating a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

2, the image data processor 100 may include a storage 110, a backlight driving signal generator 150, and a converted image data generator 180.

The backlight drive signal generator 150 may include an initial value extractor 120, an area separator 130, and a backlight drive signal calculator 140. The converted image data generator 180 may include an interface compensator 160 and an image data converter 170.

The storage unit 110 stores input image data 21 for one frame of display to be displayed on the liquid crystal display panel (step S810). Here, the input image data 21 is n-bit digital data in which m gray levels can be expressed, and has a relationship of m = 2 ⁿ . For example, when the input image data 21 is 8-bit data capable of R, G, and B expressions, the R, G, and B input image data may each express 2 ⁸ = 26, that is, 256 gray levels.

The initial value extractor 120 extracts an initial value corresponding to a ratio of pixels having luminance equal to or greater than a predetermined gray level value from among input image data of one frame stored in the storage 110 (step S820). For example, the initial value may be determined according to a ratio of pixels having luminance corresponding to 1/2 or more of the maximum luminance among the input image data of one frame. Extract the initial value accordingly. For example, in the case of 8-bit data, that is, input image data capable of expressing 256 gray levels, an initial value may be extracted by obtaining a ratio of pixels having luminance equal to or greater than 128 gray levels among pixel data of one frame.

The region separator 130 separates the input image data 21 into a plurality of divided regions determined according to the size and resolution of the liquid crystal display (step S830). For example, if the Full-HD resolution (1920 x 1080) is divided into 8 x 8 (64) partitions, one partition has 32,400 (240 X 135) pixels.

The backlight driving signal calculator 140 calculates the maximum value, the average value and the difference value of the data from the divided image data (step S840) to obtain a backlight driving signal 27 (step S850). The divided image data is all compared in units of pixels to calculate a maximum value and an average value, and a difference value is calculated using the calculated maximum value and the average value. The difference value represents a luminance difference value between the maximum value and the average value of the image data.

The backlight driving signal 27 may be obtained by adding a product of the difference value and the change rate to the average value.

FIG. 3 is a graph for describing a process of calculating a rate of change in the backlight driving signal calculator of FIG. 1.

The change rate can be obtained by the following Equation 1 as shown in FIG.

Rate of change = (1-initial value) X (difference value / m) + initial value

For example, when the initial value extracted from the 8-bit (m = 256) input image data 21 is 0.5, the maximum value of the divided region is 200 gray levels and the average value is 100 gray levels, the calculated difference value is 100. The change rate is 0.695. Accordingly, the backlight driving signal of the divided area becomes a backlight power signal corresponding to 170 gray levels.

The backlight drive signal 27 generated by the backlight drive signal calculator 140 is input to the backlight controller 40 to drive the backlight 30. The backlight 30 supplies light to the liquid crystal display panel 10. For example, the backlight 30 may be implemented as a fluorescent lamp or an LED lamp capable of supplying light by dividing each area into the liquid crystal display panel 10.

4 is a conceptual diagram illustrating a compensation operation in the interface compensation unit of FIG. 1. 5 to 7 are conceptual diagrams for describing a two-step backlight data operation in the interface compensation unit of FIG. 1.

The interface compensator 160 generates backlight data by correcting the grayscales near the boundary surfaces of the divided regions by a predetermined grayscale value per pixel (step S860). As shown in FIG. 5, the interface compensator 160 corrects the diagonal effect between the divided regions, as shown in FIG. 6, in the vertical direction near the boundary surface of the divided regions. As shown in FIG. 6, the grayscale near the boundary is corrected by a predetermined gray level, and as shown in FIG. 6, the grayscale near the boundary is corrected by a predetermined gray level per pixel in the horizontal direction near the boundary of the divided regions. Can be generated. Here, the case of correcting in the vertical direction and then correcting in the horizontal direction has been described as an example. However, the correction in the horizontal direction may also be corrected in the vertical direction.

As shown in FIG. 4, the interface compensator 160 linearly changes data near the boundary of the divided region in consideration of the illuminance range of the LED, and calculates an operation on the edge of the divided region as illustrated in FIG. 5. In order to perform the correction in two steps by generating the data corrected in the vertical direction using the data corrected in the horizontal direction. For example, in the case of two divided regions adjacent to each other, having 100 gray levels and 160 gray levels, and having a crosstalk distance of 30 pixels in which light is dispersed, the backlight changes by two gray levels between pixels at the boundary of the two divided areas. You can generate data.

The image data converter 170 generates the converted image data 23 by increasing the input image data 21 by a decrease amount of the backlight data generated by the interface compensator 160 relative to the maximum luminance (step S870). For example, if the pixel data of the 8-bit input image data is 150 gray scales and the backlight data is 200 gray scales, the amount of reduction of the backlight data becomes 55 (255-200), so that the pixel data is changed to 205 gray scales. The converted image data may be generated.

As described above, the converted image data 23 whose luminance is converted by the image data converter 170 is output, and the converted converted image data 27 is input to the liquid crystal display panel 10 to display an image. The image displayed on the liquid crystal display panel 10 by the converted image data 27 may display the same luminance as the input image data despite the backlight luminance.

The present invention having the above configuration will be described with reference to the flowchart of FIG. 5 for a method of driving a liquid crystal display according to the embodiment.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

1 is a circuit diagram of a conventional AMOLED (Active Matrix Organic Light Emitting Diode) pixel circuit.

1 is a block diagram illustrating a configuration of a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 2 is a block diagram illustrating a detailed configuration of the image data processor of FIG. 1. 3 is a graph for explaining a rate of change according to an embodiment of the present invention.

FIG. 3 is a graph for describing a process of calculating a rate of change in the backlight driving signal calculator of FIG. 1.

4 is a conceptual diagram illustrating a compensation operation in the interface compensation unit of FIG. 1.

5 to 7 are conceptual views illustrating a two-step backlight data operation in the interface compensation unit of FIG. 1.

8 is a flowchart illustrating a driving method of a liquid crystal display according to an exemplary embodiment of the present invention.

Claims (22)

Generating a backlight driving signal for driving the backlight for each of the plurality of divided regions based on input image data, and based on the backlight data obtained by correcting the gray level of the boundary surface of the divided plurality of regions by a predetermined gray level per pixel; An image data processor configured to generate converted image data obtained by converting luminance of input image data; A liquid crystal display panel configured to receive the converted image data and display an image corresponding to the converted image data; And And a backlight unit for supplying the brightness-adjusted backlight to the liquid crystal display panel by adjusting the brightness of the backlight based on the backlight driving signal. The method of claim 1, wherein the image data processing unit A storage unit for receiving and providing input image data of one frame, wherein the input image data is a digital value of n (natural numbers) bits representing 2 ⁿ gray levels; A backlight driving signal generator for separating the input image data of the one frame into a plurality of divided regions and generating a backlight driving signal for driving the backlight for each of the plurality of divided regions; And And a converted image data generation unit configured to generate converted image data in which luminance of the input image data is converted based on backlight data obtained by correcting the gray levels of pixels near boundaries of the plurality of divided regions by a predetermined gray level value per pixel. A liquid crystal display device characterized by the above-mentioned. The display device of claim 2, wherein the backlight driving signal generator An initial value extracting unit obtaining an initial value corresponding to a ratio of pixels having luminance equal to or greater than a predetermined gray level value among the input image data of the one frame stored in the storage unit; A region separator configured to separate the input image data of the one frame into a plurality of divided regions; And And a backlight driving signal calculator configured to generate a backlight driving signal for driving the backlight for each of the plurality of divided regions. The method of claim 3, wherein the initial value is And a ratio of pixels having luminance corresponding to at least 1/2 of the maximum luminance among the input image data of the one frame. The method of claim 3, wherein the backlight driving signal calculator Obtain a maximum value and an average value of the input image data in units of pixels for each of the plurality of divided regions, and add the difference value to the average value, wherein the difference value is the luminance difference value of the maximum value and the average value, and multiplying the change rate. And generating the backlight driving signal. The method of claim 5, wherein the rate of change is the following equation (1-initial value) X (difference value / 2 ⁿ ) + initial value It is calculated | required by the liquid crystal display device characterized by the above-mentioned. The method of claim 2, wherein the converted image data generating unit An interface correction unit for generating backlight data by correcting a gradation in the vicinity of the boundary of the divided regions by a predetermined gradation value per pixel; And And an image data converter configured to generate converted image data in which luminance of the input image data is converted based on the backlight data. The method of claim 7, wherein the interface correction unit In order to correct the diagonal effect between the plurality of divided regions, the gray level near the boundary surface in the vertical direction is corrected by a predetermined gray level per pixel in the vicinity of the boundary surface of the plurality of divided regions, and the boundary surface of the plurality of divided regions. And the backlight data is generated by correcting a gray level near the boundary surface in a horizontal direction from a vicinity by a predetermined gray level per pixel. The method of claim 8, wherein the image data converter And converting the brightness of the input image data by the amount of reduction of the backlight data to generate converted image data. An image data processing apparatus for providing a liquid crystal display panel with a backlight driving signal for adjusting a brightness of a backlight. A backlight driving signal generator configured to receive input image data from an external source, divide the input image data into a plurality of divided regions, and generate a backlight driving signal for driving the backlight for each of the divided plurality of divided regions; And A converted image data generation unit configured to generate converted image data obtained by converting the luminance of the input image data based on the backlight data obtained by correcting the gray level of the boundary of the divided regions by a predetermined gray level per pixel and providing the converted image data to the liquid crystal display panel; Image data processing apparatus comprising a. The apparatus of claim 10, wherein the image data processing device is And a storage unit configured to receive and provide input image data of one frame, wherein the input image data is a digital value of n (natural numbers) bits representing 2 ⁿ gray levels. The display device of claim 11, wherein the backlight driving signal generator An initial value extracting unit obtaining an initial value corresponding to a ratio of pixels having luminance equal to or greater than a predetermined gray level value among the input image data of the one frame stored in the storage unit; A region separator configured to separate the input image data of the one frame into a plurality of divided regions; And And a backlight driving signal calculator configured to generate a backlight driving signal for driving the backlight for each of the plurality of divided regions. The apparatus of claim 12, wherein the backlight driving signal calculator is configured to obtain a maximum value and an average value of input image data in units of pixels for each of the plurality of divided regions, wherein the difference value is the difference value, wherein the difference value is the maximum value and the average value. The backlight driving signal is generated by adding the product of the difference in luminance and multiplied by the change rate, The change rate is represented by the following equation (1-initial value) X (difference value / 2 ⁿ ) + initial value The image data processing device, characterized by the above-mentioned. The method of claim 12, wherein the converted image data generating unit An interface correction unit for generating backlight data by correcting a gradation in the vicinity of the boundary of the plurality of divided regions by a predetermined gradation value per pixel; And And an image data converter configured to generate converted image data obtained by converting the luminance of the input image data based on the backlight data. The method of claim 14, wherein the interface correction unit In order to correct the diagonal effect between the plurality of divided regions, the gray level near the boundary surface in the vertical direction is corrected by a predetermined gray level per pixel in the vicinity of the boundary surface of the plurality of divided regions, and the boundary surface of the plurality of divided regions. And the backlight data is generated by correcting a gray level near the boundary surface by a predetermined gray level per pixel in the horizontal direction from the vicinity. The image data converting unit of claim 14, wherein the image data converter comprises: And converting the brightness of the input image data by the decrease amount of the backlight data to generate converted image data. To drive a backlight for each of the plurality of divided regions by dividing one frame of input image data, wherein the input image data is a digital value of n (natural numbers) bits representing 2 ⁿ gray levels. Generating a backlight driving signal for the device; Generating converted image data in which brightness of the input image data is converted based on backlight data obtained by correcting the gray levels of the boundary surfaces of the plurality of divided regions by a predetermined gray level per pixel; Supplying the brightness-adjusted backlight to a liquid crystal display panel by adjusting the brightness of the backlight based on the backlight driving signal; And And providing the converted image data to the liquid crystal display panel to display an image corresponding to the converted image data. 18. The method of claim 17, wherein generating the backlight driving signal Obtaining an initial value corresponding to a ratio of pixels having luminance equal to or greater than a predetermined gray level among the input image data of the one frame; Dividing the input image data of the one frame into a plurality of divided regions; And And generating a backlight driving signal for driving the backlight for each of the plurality of divided regions. The method of claim 18, wherein the backlight driving signal is Obtain a maximum value and an average value of the input image data in units of pixels for each of the plurality of divided regions, and add the difference value to the average value, wherein the difference value is the luminance difference value of the maximum value and the average value, and multiplying the change rate. Create, The change rate is represented by the following equation (1-initial value) X (difference value / 2 ⁿ ) + initial value It is calculated | required by the liquid crystal display drive method characterized by the above-mentioned. The method of claim 17, wherein generating the converted image data Generating backlight data by correcting a gray scale near a boundary of the divided regions by a predetermined gray scale value per pixel; And And generating converted image data obtained by converting the luminance of the input image data based on the backlight data. The method of claim 20, wherein the generating of the backlight data by correcting the grayscales near the boundary of the divided regions by a predetermined grayscale value per pixel is performed. Correcting the gray level near the boundary surface in the vertical direction by a predetermined gray level per pixel to correct the diagonal effect between the divided plurality of regions in a vertical direction near the boundary surface of the plurality of divided regions; And And generating the backlight data by correcting the gray level near the boundary surface by a predetermined gray level per pixel in a horizontal direction near the boundary surface of the divided regions. The method of claim 17, wherein generating the converted image data And generating converted image data by increasing the luminance of the input image data by the amount of decrease of the backlight data.

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