KR20080002394A - Liquid crystal display - Google Patents

Abstract

The present invention relates to a liquid crystal display device suitable for enhancing perspective and stereoscopic display of an image.

The liquid crystal display device includes a liquid crystal panel in which pixels are formed; A data driver for supplying a pixel driving signal input by the pixels on the liquid crystal panel by one line; A luminance-chromation correction unit for compensating the chromaticity component of the video data to be supplied to the data driver according to a predetermined gamma characteristic and selectively correcting the luminance component of the video data; And an area discriminator which detects an area in which video data to be supplied to the data driver is displayed on the liquid crystal panel and selectively performs luminance and chromaticity correction operations of the brightness-chromatity correction unit according to the detected area.

Description

Liquid Crystal Display Device Gamma-error}

In order to better understand the drawings used in the detailed description of the invention, a brief description of each drawing is provided.

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

FIG. 2A is a diagram illustrating gamma characteristics of luminance and chromaticity components of input video data input to the luminance-chromatity correcting unit of FIG. 1.

2B and 2C are diagrams for describing gamma characteristics of luminance and chromaticity components of video data output from the luminance-chromatic correction unit of FIG. 1.

FIG. 3 is a detailed block diagram illustrating in detail the luminance-chromatic correction unit shown in FIG. 1.

`` Explanation of symbols for main parts of drawings ''

10 liquid crystal panel 12 gate driver

14: data driver 16: timing control unit

18: luminance-chromatity correction unit 20: region discrimination unit

100: matrix 102: histogram analysis unit

104,106: first and second delayers 108: luminance gamma compensation unit

110, 114: first and second mixer 112: chroma gamma compensation unit

116: reverse matrix SW1, SW2: switch for the first and second control

The present invention relates to a liquid crystal display device capable of faithful reproduction of an image.

A cathode ray tube (hereinafter referred to as a "CRT") has been commonly used as a display device to date, but an active matrix liquid crystal display device (hereinafter referred to as "LCD") has recently been widely used. The LCD displays an image by adjusting the amount of planar light passing through the liquid crystal layer from the rear in units of pixels.

Such LCDs have been used as screens in notebook computers or as monitors in desktop computers, but recently they have also been used in television receivers. LCDs used as video display devices of television receivers must display images clearly.

In addition, LCDs used as video display devices of television receivers are being enlarged in order to make a movie feel like watching a movie. As LCDs become larger, viewers' eyes have no choice but to disperse. In addition, in large LCDs, perspective and stereoscopic display of images may be weakened. As a result, the sharpness of the image displayed on the LCD is also reduced.

Accordingly, an object of the present invention is to provide a liquid crystal display device suitable for enhancing perspective and stereoscopic display of an image.

Another object of the present invention is to provide a liquid crystal display device suitable for displaying an image more clearly.

According to an embodiment of the present invention, a liquid crystal display device includes: a liquid crystal panel in which pixels are formed; A data driver for supplying a pixel driving signal input by the pixels on the liquid crystal panel by one line; A luminance-chromation correction unit for compensating the chromaticity component of the video data to be supplied to the data driver according to a predetermined gamma characteristic and selectively correcting the luminance component of the video data; And an area discriminator which detects an area in which video data to be supplied to the data driver is displayed on the liquid crystal panel and selectively performs luminance and chromaticity correction operations of the brightness-chromatity correction unit according to the detected area.

In addition to the objects of the present invention as described above, other objects, other advantages and other features of the present invention will become apparent from the detailed description of the preferred embodiment with reference to the accompanying drawings.

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

1 is a block diagram schematically illustrating a liquid crystal display according to an exemplary embodiment of the present invention. Referring to FIG. 1, a gate driver 12 connected to a plurality of gate lines GL1 to GLn on a liquid crystal panel 10 and a data driver connected to a plurality of data lines DL1 to DLm on a liquid crystal panel 10. (14) is provided. The plurality of gate lines GL1 to GLn and the plurality of data lines DL1 to DLm are formed on the liquid crystal panel 10 to cross each other so that the plurality of pixel regions are distinguished. In each of the plurality of pixel regions, a thin film transistor MN for switching a pixel driving signal to be supplied to a corresponding liquid crystal cell CLC from a corresponding data line DL is formed in response to a scan signal on a corresponding gate line GL. do. The liquid crystal cell CLC adjusts the amount of light passing through the pixel region according to the voltage level of the pixel driving signal, thereby allowing an image to be displayed.

The gate driver 12 enables the plurality of gate lines GL1 to GLn for one frame sequentially and exclusively for a predetermined period (that is, for each period of one horizontal sync signal). To this end, the gate driver 12 generates a plurality of scan signals exclusively having enable pulses sequentially shifted for each period of the horizontal synchronization signal. The gate enable pulse included in each of the plurality of scan signals has a width corresponding to the period of the horizontal synchronization signal. The gate enable pulse included in each of the plurality of scan signals is generated once every frame period.

Whenever one of the plurality of gate lines GL1 to GLn is enabled, the data driver 14 corresponds to the number of data lines DL1 to DLm corresponding to one pixel line (ie, one gate line). Pixel driving signals corresponding to the number of pixels arranged in the. Each of the pixel driving signals for one line is supplied to a corresponding pixel on the liquid crystal panel 10 (ie, the liquid crystal cell CLC) via the corresponding data line DL. Each of the pixels arranged on one gate line GL passes an amount of light corresponding to a voltage level of the pixel driving signal. In order to generate one line of pixel driving signals, the data driver 14 sequentially inputs one line of pixel data from the data transmission line DTL every period of one horizontal synchronization signal, and sequentially inputs one of the pixel driving signals. Simultaneously converts pixel data for lines into an analog form.

The gate driver 12 and the data driver 14 are controlled by the timing controller 16. The timing control unit 16 receives a synchronization signal from an external video data source (for example, an image signal demodulation unit included in a television reception module or a graphics card included in a computer system) not shown via a control transmission line CTL. Enter SYNC. The synchronization signals SYNC supplied from an external video data source include a data clock Dclk, a horizontal synchronization signal Hsync, a vertical synchronization signal Vsync, and the like. The timing controller 16 generates the gate control signals GCS necessary for the gate driver 12 to generate a plurality of scan signals every frame using the synchronization signals SYNC. In addition, the timing controller 16 inputs one line of pixel data sequentially in the data driver 12 every cycle of the horizontal synchronization signal, and converts the sequentially input one line of pixel data into an analog pixel drive signal. Generates data control signals (DCS) necessary to convert and output.

In the liquid crystal display of FIG. 1, the luminance-chromatity correcting unit 18 connected in series between the data transmission line DTL and the data driver 14 and the area determining unit 20 connected to the control transmission line CTL are provided. Included. The luminance-chromatity correcting unit 18 corrects the luminance component or the chromaticity component according to the area of the screen of the pixel data stream VD including the red, green, and blue sub-pixel data from the data transmission line DTL. The luminance-chromatity correcting unit 18 performs low luminance gamma correction so that the luminance component of the pixel data to be displayed in the edge region of the liquid crystal panel 10 has a linear characteristic. The luminance-chromatity correcting unit 18 performs chromatic gamma correction on the pixel data to be displayed in the center portion of the liquid crystal panel 10 so that the chromaticity component has a linear characteristic. The pixel data of the edge region low luminance gamma corrected by the luminance-chromatity correcting unit 18 and the pixel data of the central portion subjected to chroma gamma correction are converted into pixel driving signals by one line by the data driver 14, thereby converting the liquid crystal panel ( The image is displayed on the liquid crystal panel 10 by being supplied to the data lines DL1 to DLm on the image 10.

The area determining unit 20 may adjust the luminance-chromation correcting unit in response to the vertical synchronizing signal Vsync, the horizontal synchronizing signal Hsync, and the data clock Dclk among the synchronizing signals SYNC from the control transmission line CTL. A position on the liquid crystal panel 10 with respect to pixel data input to 18 is determined. In other words, the area discriminating unit 20 detects whether the pixel data input to the luminance-chromatity correcting unit 18 is displayed at the edge or the center of the liquid crystal panel 10 and determines the area according to the detected result. The signal is supplied to the luminance-chromatity correction unit 18. The area discrimination signal has a specific logic (for example, high or low logic) if the pixel data input to the luminance-chromatity corrector 18 is to be displayed at the edge of the liquid crystal panel 10, while the luminance-chromatity corrector If the pixel data inputted to (18) is to be displayed in the center portion of the liquid crystal panel 10, it has a basis logic (for example, low or high logic).

If this area discrimination signal has a specific logic, the luminance chromaticity correction unit 18 corrects the luminance component of the pixel data having the average luminance among the pixel data of the edge area according to the high gamma curve characteristic. Accordingly, the luminance component of the pixel data of the edge region having the same gamma characteristic as that of Dy of FIG. 2A has the same gamma characteristic as that of Dy of FIG. 2B by the luminance-chromatity correcting unit 18. In this way, among the luminance components of the pixel data of the edge region, the luminance component of the low luminance is gamma-corrected so that an image displayed on the liquid crystal panel 10 has a high contrast ratio at the boundary between the edge and the center portion. As a result, the perspective and stereoscopic effects of the image are improved.

On the contrary, if the area discrimination signal has a basis logic, the luminance-chromatity correcting unit 18 causes the chromaticity components of the halftone values in the pixel data in the center to be corrected according to the high gamma curve characteristic. By chromaticity correction of the luminance-chromatity correcting unit 18, the chromaticity component of the pixel data of the central region having a low gamma characteristic as shown in Dc in FIG. It is calibrated to have characteristics. In this way, the chromaticity component of the middle grayscale value section among the chromaticity components of the pixel data of the central region is gamma-corrected to improve the chromaticity component of the image displayed in the central region of the liquid crystal panel 10. As a result, the image is clearly displayed in the center region of the liquid crystal panel.

FIG. 3 is a detailed block diagram illustrating an embodiment of the luminance-chromatity correcting unit 18 shown in FIG. 1 in detail. Referring to FIG. 3, the luminance-chromatity corrector 18 includes a matrix 100 and a histogram analyzer 102 connected in series with a data transmission line DTL. The matrix 100 collects the red, green, and blue subpixel data sequentially input from the data transmission line DTL, and combines the collected red, green, and blue subpixel data to generate luminance data and chromaticity data. . The luminance data generated in the matrix 100 is supplied to the histogram analyzer 102 and the first retarder 104, while the chromaticity data generated in the matrix 100 is supplied to the second retarder 106. .

The histogram analyzer 102 integrates the luminance data from the matrix 100 for each image (that is, in units of frames) to calculate an average of luminance data in one image. The average luminance data thus calculated is supplied to the luminance gamma correction unit 108. The first retarder 104 delays the luminance data from the matrix 100 by the propagation delay time (ie, one frame period) in the histogram analyzer 102, and delays the delayed luminance data with the first control switch SW1. To feed. The second delayer 106 also delays the chromaticity data from the matrix 100 by the propagation delay time (that is, one frame period) in the histogram analyzer 102, and delays the delayed chromaticity data into the second control switch SW2. To feed. As a result, the first and second delayers 104 and 106 have an average of the luminance data to be supplied to the first control switch SW1 and the chromaticity data to be supplied to the second control switch SW2 generated by the histogram analyzer 102. Synchronize with luminance data.

The first and second control switches SW1 and SW2 respond to the area discrimination signal from the area discrimination unit 20 in FIG. 1. The first control switch SW1 transmits the delayed luminance data from the first retarder 104 to the luminance data to be displayed in the edge region of the liquid crystal panel 10 and the central region of the liquid crystal panel 10 in response to the region determination signal. Separate the luminance data to be displayed. To this end, the first control switch SW1 causes the first retarder 104 to be connected to the luminance gamma correction unit 108 when the area discrimination signal maintains a specific logic (for example, high or low logic). On the contrary, if the region discrimination signal has a basis logic (eg, low or high logic), then the first retarder 104 is connected to the first mixer 110. Accordingly, the luminance data of the edge region separated by the first control switch SW1 is supplied to the luminance gamma correction unit 108, while the luminance data of the central region separated by the first control switch SW1 is generated. 1 is supplied to the mixer 110. The second control switch SW2 separates the delayed chromaticity data from the second retarder 106 into chromaticity data of the edge region of the liquid crystal panel 10 and chromaticity data of the central region in response to the region determination signal. To this end, the second control switch SW2 causes the first retarder 106 to be connected to the second mixer 114 if the area discrimination signal maintains a certain logic (eg, high or low logic), On the contrary, if the area discrimination signal has a basis logic (for example, low or high logic), the second delay unit 106 is connected to the chroma gamma correction unit 112. Accordingly, chromaticity data of the edge region separated by the second control switch SW2 is supplied to the second mixer 114, while luminance data of the central region separated by the second control switch SW2 is chroma gamma. The correction unit 112 is supplied. As a result, the first and second control switches SW1 and SW2 perform complementary switching operations. In other words, when the luminance data of the edge separated by the first control switch SW1 is supplied with the luminance gamma correction unit 108, the chromaticity data of the edge region separated by the second control switch SW2 is obtained. When the luminance data of the central region, which is supplied to the second mixer 114 and separated by the first control switch SW1, is supplied to the first mixer 110, the second mixer 114 is separated by the second control switch SW2. Chromaticity data of the central region is supplied to the chroma gamma correction unit 112.

The luminance gamma correction unit 108 gamma-corrects the luminance data of the edge region from the first control switch SW1 selectively in response to the average luminance data from the histogram analyzer 102. Specifically, the luminance gamma correction unit 108 separates luminance data of an edge region of a gray scale value lower than a logic value (that is, a gray scale value) of the average luminance data. In other words, the luminance gamma correction unit 108 checks whether the luminance data from the first control switch SW1 is lower than the logical value (gradation value) of the average luminance data. When luminance data lower than the gray scale value of the average luminance data is input from the first control switch SW1, the luminance gamma correction unit 108 corrects the low luminance data to have a high gray scale value according to the high gamma characteristic curve. The luminance data of the gamma corrected edge region is supplied to the first mixer 110. On the other hand, when luminance data higher than the logical value (i.e., gradation value) of the average luminance data is input from the first control switch SW1, the luminance gamma correction unit 108 outputs the luminance data of the edge region of the high gradation value. It is supplied to the first mixer 110 as it is to maintain the original value. As a result, the luminance data of the edge region having the same gamma characteristics as Dy of FIG. 2A is corrected by the luminance gamma correction unit 108 such that luminance data having an average gray scale value or less, as shown by Dy in FIG. 2B, has a linear characteristic. . The first mixer 110 is configured by the luminance gamma correction unit 108 from the luminance data of the edge region corrected according to the high gamma characteristic and the first control switch SW1 so that luminance data below the average luminance has a linear gamma characteristic. The luminance data of the central region of the image is collected to form luminance data for one image. The luminance data of one image mixed by the first mixer 110 is supplied to the inverse matrix 116.

The chroma gamma correction unit 112 corrects chromaticity data having intermediate grayscale values among chromaticity data of the central region from the second control switch SW2 to have a high grayscale value according to a high gamma characteristic curve. The chroma gamma correction unit 112 supplies the chromaticity data having the grayscale value lower or higher than the intermediate grayscale values among the chromaticity data of the central region from the second control switch SW2 to the second mixer 114 as it is. Accordingly, the chromaticity data of the central region having a low gamma characteristic curve as shown in Dc of FIG. 2A has a linear gamma characteristic in the middle gray value range as shown in Dc of FIG. 2C, and also has a low gray value range and a high gray value. The interval is corrected to have a low gamma characteristic. The chromaticity data of the central region corrected according to the high gamma characteristic by the chroma gamma correction unit 112 so that the chromaticity data of the intermediate grayscale value section has a linear gamma characteristic is controlled by the second mixer 114 by the second control switch SW2. ) Is combined with chromaticity data of the edge area to form chromaticity data for one screen.

The inverse matrix 116 reverse-combines the luminance data of one image having high gamma-corrected luminance data of the edge region of low gray scale and the chromaticity data of one image having high gamma chroma data of the central region of intermediate gray scale red and green. And blue sub-pixel data. The red, green, and blue sub-pixel data inversely combined by the inverse matrix 116 are divided into lines and supplied to the data driver 14 shown in FIG. The red, green, and blue sub-pixel data output from the inverse matrix 116 is corrected such that the luminance component below the average luminance value has a linear gamma characteristic and the sub pixel data of the edge region where the luminance component is corrected to have a linear gamma characteristic. The sub pixel data of the central region of the halftone value are included. Since the data driver 14 drives the liquid crystal panel 10 in response to the sub-pixel data, in the image displayed on the liquid crystal panel 10, the contrast ratio between the edge region and the center region becomes high and the chromaticity difference in the center region is different. Is improved. As a result, in the image displayed on the liquid crystal panel 10, the perspective and stereoscopic effects are improved and the image of the central region is clearly displayed.

As described above, in the liquid crystal display device according to the present invention, among the luminance components of the pixel data of the edge region, the luminance component of low luminance is highly gamma corrected. As a result, the contrast ratio at the edge and the center portion of the image displayed on the liquid crystal panel becomes high. As a result, the perspective and stereoscopic effects of the image are improved. In addition, among the chromaticity components of the pixel data to be displayed in the central region of the liquid crystal panel, the chromaticity component of the middle grayscale value section is highly gamma corrected. Accordingly, the chromaticity component of the image displayed in the central region of the liquid crystal panel 10 is improved. As a result, the image is displayed clearly at the center of the liquid crystal panel.

As described above, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and a person of ordinary skill in the art without departing from the spirit and scope of the present invention. It will be apparent that various modifications, changes, and equivalent other embodiments are possible. Accordingly, the scope of the present invention to be protected should be defined by the appended claims.

Claims (6)

A liquid crystal panel in which pixels are formed; A data driver for supplying a pixel driving signal input by the pixels on the liquid crystal panel by one line; And A luminance-chromation correction unit for compensating the chromaticity component of the video data to be supplied to the data driver according to a predetermined gamma characteristic and selectively correcting the luminance component of the video data; And And a region discriminating unit which detects a region in which video data to be supplied to the data driver is to be displayed on the liquid crystal panel and selectively performs luminance and chromaticity correction operations according to the detected region. Liquid crystal display device. The liquid crystal display of claim 1, wherein the luminance-chromatity correcting unit corrects a luminance component of the video data when an edge region is detected by the region discriminating unit. The method of claim 2, And the luminance-chromatity correcting unit compensates for a high luminance component of a low gray level among the luminance components of the video data. The method of claim 3, wherein And the luminance-chromatic correcting unit compensates for a luminance component equal to or less than an average luminance value among the luminance components of the video data. The liquid crystal display of claim 2, wherein the luminance-chromatity correcting unit corrects a chromaticity component of the video data when a center region is detected by the region discriminating unit. The apparatus of claim 1, wherein the luminance-chromatity correction unit A matrix for combining luminance and chroma components from the video data; A switch unit that separates the luminance and chroma components from the center and the luminance and chroma components from the edges in response to the luminance and chroma components from the matrix in response to a region detection result from the region discriminator; A histogram analyzer configured to calculate an average luminance value by histogram analysis of the luminance components from the matrix; A luminance gamma compensator for compensating only a luminance component equal to or less than the average luminance value among the luminance components of the edge from the switch unit; A chromaticity gamma correction unit for gamma-correcting the chromaticity component of the central portion from the switch unit at a constant compensation rate; A first mixing unit mixing a luminance component of the center portion from the switch unit and a luminance component from the luminance gamma compensation unit; A second mixing unit mixing the edge chromaticity component from the switch unit and the chromaticity component from the chromaticity gamma compensation unit; And And an inverse matrix for inversely combining video data from the luminance and chromatic components from the first and second mixing units and supplying the inversely combined video data to the data driver.

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