KR100843696B1 - Method and apparatus for correcting color of liquid crystal display - Google Patents

Abstract

The present invention relates to a color correction method and apparatus for a liquid crystal display device capable of correcting color reproducibility in the same way as a CRT.

The color correction method of the present invention uses the same color reproduction characteristics as that of the cathode ray tube using the tristimulus value modeling the characteristics of the cathode ray tube and the color leakage error and the black error by inputting the video data. Color correction to have; And converting the color-corrected video data into a video voltage signal which is an analog signal and supplying the same to the liquid crystal panel.

Description

METHOD AND APPARATUS FOR COLOR CALIBRATION OF LCD DEVICES             

1 is a block diagram showing a conventional liquid crystal display device.

2A to 2C are graphs showing color reproduction characteristics of a cathode ray tube.

3A to 3C are graphs showing color reproduction characteristics of a liquid crystal display.

4 is a color coordinate diagram of R, G, and B by tristimulus values of a conventional liquid crystal display.

5 is a color coordinate diagram of R, G, and B by tristimulus values applied to the liquid crystal display of the present invention.

6 is a block diagram illustrating a configuration of a color correction circuit according to an embodiment of the present invention.

7 is a block diagram illustrating a configuration of a color correction circuit according to another embodiment of the present invention.

8 is a block diagram showing a configuration of a liquid crystal display device to which a color correction device according to the present invention is applied.

<Brief description of symbols for the main parts of the drawings>

2, 50: video card 4, 52: timing controller

6, 56: data driver 8, 58: gate driver                 

10, 60: liquid crystal panel 20, 30: CRT matrix converter

22, 32: first scale factor part 24, 34: second scale factor part

26: CRT inverse matrix converter 36: RGB separation unit

38: R table 40: G table

42: B table 54: color correction unit

The present invention relates to a color correction method and apparatus for a liquid crystal display device capable of correcting the color reproduction characteristics of the liquid crystal display device in the same manner as a cathode ray tube.

The liquid crystal display displays an image by adjusting the light transmittance of the liquid crystal according to the image signal. In such a liquid crystal display, a gamma characteristic in which the gray level of an image does not change linearly but varies linearly with the voltage level of an image signal is displayed. This is due to the fact that the light transmittance of the liquid crystal does not change linearly with the voltage level of the image signal, and the gray scale of the image does not change linearly with the light transmittance of the liquid crystal. In order to prevent the image from deteriorating due to this gamma characteristic, gamma correction voltages are used to change the intervals between voltage levels of the image signal differently. In other words, the liquid crystal display corrects the gamma characteristic by adding a gamma voltage which is preset so as to have a different level according to the voltage level of the image signal as an offset voltage.                         

As shown in FIG. 1, the liquid crystal display includes a liquid crystal panel 10 in which liquid crystal cells are arranged in a matrix, a gate driver 8 for driving gate lines GL0 to GLn of the liquid crystal panel 10, and a liquid crystal panel 10. The data driver 6 for driving the data lines DL1 to DLm of the liquid crystal panel 10, the timing controller 4 for controlling the driving timing of the data driver 6 and the gate drive 8, and And a video card 2 for supplying video data to the timing controller 4.

The video card 2 converts and supplies the input video data R, G, and B to suit the resolution of the liquid crystal panel 10. The video card 2 also supplies synchronization signals such as a main clock signal, a vertical synchronization signal and a horizontal synchronization signal suitable for the resolution.

The timing controller 4 relays the video data R, G, and B from the video card 2 and supplies it to the data driver 6. The timing controller 4 also generates various control signals for controlling the drive of the data and gate drivers 6 and 8 using the synchronization signals from the video card 2.

The gate driver 8 sequentially supplies the gate high voltage signal to the gate lines GL1 to GLn of the liquid crystal panel 10 according to the control signal from the timing controller 4.

The data driver 6 converts video data from the timing controller 4 into a video voltage signal which is an analog signal using gamma voltages from a gamma circuit (not shown). The data driver 6 supplies one horizontal line of video voltage signals to the data lines DL1 through DLm every one horizontal period in which the gate high voltage signals are supplied to the gate lines GL1 through GLn. In this case, the gamma circuit supplies the gamma voltages pre-set to the data driver to have different voltage levels and offset voltages in consideration of gamma characteristics according to the video data, thereby allowing the gamma characteristics of the liquid crystal display to be corrected.

The liquid crystal panel 10 includes a thin film transistor TFT formed at an intersection of the gate lines GL1 to GLn and the data lines DL1 to DLm, and a liquid crystal arranged in a matrix form connected to the thin film transistor TFT. With cells. The thin film transistor TFT supplies a video signal from the data lines DL1 to DLm to the liquid crystal cell in response to the gate high voltage signal from the gate lines GL1 to GLn. The liquid crystal cell is equivalently represented by the liquid crystal capacitor Clc because the liquid crystal cell is composed of a common electrode facing the liquid crystal and a pixel electrode connected to the thin film transistor. The liquid crystal cell also includes a storage capacitor Cst connected to the previous gate line to maintain the data voltage charged in the liquid crystal capacitor Clc until the next data voltage is charged.

In a display device including such a liquid crystal display device, a gamma characteristic in which a gray level of an image does not change linearly but varies linearly according to a voltage level of an image signal appears. These gamma characteristics are different depending on the display device. In a cathode ray tube (hereinafter referred to as a CRT) using phosphor emission by electrons, red (hereinafter referred to as R), green (hereinafter referred to as G), and blue (hereinafter referred to as CRT) as shown in FIGS. 2A to 2C. Each color has the same gamma characteristic.

2A to 2C illustrate graphs of brightness characteristics of the CRT according to input luminance values.

Referring to FIG. 2A, it can be seen that the R, G, B, and white (hereinafter referred to as W) brightness characteristics (Yr, Yg, Yb, and Yw) of the CRT have a gamma characteristic that varies nonlinearly according to the digital input luminance value. have. FIG. 2B illustrates normalized brightness characteristics of R, G, B, and W shown in FIG. In other words, it can be seen that it has the same gamma value (2.2). Accordingly, in the CRT, the gamma value (2.2) is used to correct the gamma characteristics of R, G, and B, thereby enabling accurate color reproduction. In addition, since CRT has almost independent independence between R, G, and B channels, as shown in FIG. 2C, the W brightness (Yw) and the sum of the Y, R, G, and B brightnesses (Yr, Yg, and Yb) are approximately equal to each other. And the difference between the sum of R, G, and B brightnesses ((Yr + Yg + Yb) -Yw) are almost zero. In other words, CRT satisfies Color Additivity for color reproduction since there is little interference between R, G, and B channels, thereby enabling accurate color reproduction.

On the other hand, in the liquid crystal display, color reproducibility is inferior to that of the CRT due to the electro-optical characteristics of the liquid crystal. This is because the gamma characteristics of R, G, and B are different as shown in FIGS. 3A to 3C because the liquid crystal transmittance varies depending on the wavelength.

3A to 3C illustrate graphs of brightness characteristics of liquid crystal displays according to input luminance values.

Referring to FIG. 3A, it can be seen that the R, G, B, and W brightness characteristics (Yr, Yg, Yb, and Yw) of the liquid crystal display have a gamma characteristic that varies linearly with the digital input luminance value. FIG. 3B illustrates normalized brightness characteristics of R, G, B, and W shown in FIG. It can be seen. In FIG. 3B, the gamma value 2.7 means an average gamma value of the normalized brightness of the liquid crystal display. As such, since the gamma characteristics of R, G, B, and W are not the same, accurate gamma correction is difficult, so accurate color reproduction is impossible. In particular, since the liquid crystal display device implements an image by transmitting the light generated from the backlight through the liquid crystal, the color filter, and the polarizing plate, it is limited in the color gamut that can be expressed than the CRT. In addition, since the independence between the R, G, and B channels is not established, the liquid crystal display does not have the same W brightness (Yw) and the sum (Yr, Yg, Yb) of the R, G, and B brightnesses as shown in FIG. 3C. As a result, the difference between the W brightness and the sum of the R, G, and B brightnesses ((Yr + Yg + Yb) -Yw) has a relatively large value. The reason that the independence between the R, G, and B channels is not established is that a portion of the light emitted through an arbitrary subpixel is refracted and This is because a light leakage phenomenon affecting adjacent subpixels occurs due to reflection or the like. Due to such a light leakage phenomenon, color additivity for color reproduction cannot be satisfied in the liquid crystal display, so accurate color reproduction is impossible.

Accordingly, it is an object of the present invention to provide a color correction method and apparatus for a liquid crystal display device which can correct color reproducibility in the same way as a CRT.

In order to achieve the above object, the color correction method of the liquid crystal display according to the present invention is to model the color reproduction characteristics of the liquid crystal display by correcting the tristimulus value, color leakage error and black error modeling the color reproduction characteristics of the cathode ray tube Calculating tristimulus values; And performing color correction such that the input video data has the same color reproduction characteristics as the cathode ray tube by using the calculated tristimulus value of the cathode ray tube and the tristimulus value of the liquid crystal display.

The driving method of the liquid crystal display according to the present invention uses the tristimulus value modeling the color reproduction characteristics of the liquid crystal display device by correcting the tristimulus value modeling the color reproduction characteristics of the cathode ray tube, the color leakage error and the black error. Color correction to have the same color reproduction characteristics as that of the cathode ray tube; And converting the color-corrected video data into a video voltage signal which is an analog signal and supplying the same to the liquid crystal panel.

Wherein the color correction step comprises: transforming the input video data using a tristimulus value of a cathode ray tube; Normalizing the matrix-converted tristimulus values to tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; And converting the tristimulus values of the liquid crystal display device into the inverse matrix using the tristimulus values of the liquid crystal display device to calculate color corrected video data.

In contrast, the color correction step includes the step of matrix converting the input video data using the tristimulus values of the cathode ray tube; Normalizing the matrix-converted tristimulus values to tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; Separating the tristimulus values of the liquid crystal display by color; And linearly converting the tristimulus values separated by colors into color correction video data using a color-specific lookup table using video data obtained when the tristimulus values of the liquid crystal display are calculated.

The color correction apparatus of the liquid crystal display according to the present invention is a tristimulus value modeling the color reproduction characteristics of the liquid crystal display device by correcting the tristimulus value, color leakage error and black error modeling the color reproduction characteristics of the cathode ray tube It characterized in that it comprises a color correction circuit for color correction to have the same color reproduction characteristics as the cathode ray tube.

The liquid crystal display according to the present invention includes a liquid crystal panel in which liquid crystal cells are arranged in a matrix, a gate driver for driving gate lines of the liquid crystal panel, a data driver for driving data lines of the liquid crystal panel, a data driver and a gate. The timing controller for controlling the driving timing of the drive and the video data inputted from the timing controller model the color reproduction characteristics of the liquid crystal display by correcting the tristimulus value, the color leakage error, and the black error modeling the color reproduction characteristics of the cathode ray tube. It is characterized in that it comprises a color correction circuit for correcting the color to have the same color reproduction characteristics as that of the cathode ray tube using a tristimulus value and supplying it to the data driver.

The color correction circuit includes: a cathode ray tube matrix converter for matrix converting input video data using a tristimulus value of a cathode ray tube; A scale factor unit for normalizing the matrix-converted tristimulus values to tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; And an inverse matrix converting unit configured to inverse matrix transform the tristimulus values of the liquid crystal display device to calculate color corrected video data using the tristimulus values of the liquid crystal display device.

In contrast, the color correction circuit comprises: a cathode ray tube matrix converter for matrix converting input video data using a tristimulus value of the cathode ray tube; A scale factor unit for normalizing the converted tristimulus values into tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; A color separation unit for separating tristimulus values of the liquid crystal display by color; And a red, green, and blue lookup table for linearly converting tristimulus values separated by colors into color correction video data using video data obtained when calculating tristimulus values of the liquid crystal display.

In particular, the color correction circuit is integrated with any one of a data driver and a timing controller.

Other objects and advantages of the present invention in addition to the above object will be apparent from the description of the preferred embodiment of the present invention with reference to the accompanying drawings.                     

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 4 to 8.

First, in order to model LCD characteristics, a color coordinate system based on tristimulus values (X, Y, Z) representing a physical quantity of light as a wavelength function is used. The LCD color coordinate system shown in FIG. 4 shows chromaticity coordinates of R, G, and B as the 1976 CIE u'v 'coordinate system. In FIG. 4, the coordinates u 'and v' are defined by Equation 1 by tristimulus values (X, Y, Z).

In FIG. 4 using these tristimulus values (X, Y, Z), a triangular region shows a color gamut that can be expressed in an LCD. Referring to FIG. 4, it can be seen that the R, G, and B chromaticities expressed in the LCD are changed toward the central portion at each vertex according to their gray scale values. The phenomenon in which the R, G, and B chromaticities of the LCD are not constant at each vertex but changes toward the center portion is caused by color interference due to color leakage from each of the R, G, and B subpixels to adjacent subpixels. This color leakage occurs because part of the light passes through adjacent subpixels due to refraction and reflection by the liquid crystal. In particular, in the liquid crystal display, color interference due to color leakage of the G and B sub-pixels is prominent. In addition, in the liquid crystal display, when the sub-pixel displays black, a black error occurs because the luminance of the black becomes high as the sub-pixel is not completely blocked by the backlight.                     

Modeling LCD characteristics using the LCD correction algorithm that calculates the ideal color stimulus values (X _{MOD_R (i)} , Y _{MOD_R (i)} , Z _{MOD_R (i)} ) by correcting black errors and color interference in the LCD. Shall be. The LCD calibration algorithm was disclosed in January 1999 under the name "On the Color Calibration of Liquid Crystal Displays" at IS & T / SPIE Conference on Display Metrology. The three stimulus values (X _{MOD_R (i)} , Y _{MOD_R (i)} , Z _{MOD_R (i)} of ideal R, which corrected black errors and color interference using this LCD correction algorithm, are defined as in Equation 2 below.

Where X _{R (i)} Y _{R (i)} Z _{R (i)} is a tristimulus value passing only R subpixels in an existing LCD, and X _{g (0)} Y _{g (0)} Z _{g (0)} and X _{b (0)} Y _{b (0)} Z _{b (0)} is the tristimulus value of the black error in the G and B subpixels, X _{LE_R (i)} Y _{LE_R (i)} Z _{LE_R (i)} represents tristimulus values of color leakage error to adjacent G and B subpixels according to the intensity of light passing through the R subpixel. According to Equation 2, ideal tristimulus values (X _{MOD_R (i)} , Y _{MOD_R (i)} , Z _{MOD_R (i)} ) for the R component can be obtained. In addition, the same three stimulus values (X _{MOD_G (i)} , Y _{MOD_G (i)} , Z _{MOD_G (i)} ) (X _{MOD_B (i)} , Y _{MOD_B (i)} , Z _{MOD_B (i)} ) can be obtained.

The color coordinate system based on the ideal tristimulus values (X _MOD , Y _MOD , Z _MOD ) obtained by correcting the color leakage error and the black error is as shown in FIG. 5. Referring to FIG. 5, the color coordinates of R, G, and B represented by the LCD are concentrated around each vertex by ideal tristimulus values (X _MOD , Y _MOD , Z _MOD ) so that a constant color coordinate is independent of the gray level values of R, G, and B. It can be seen that it has.

Using the method of obtaining the ideal tristimulus values, the corrected gradation values of R, G, and B for reproducing the same color coordinates as the CRT on the LCD can be obtained as follows. First, tristimulus values are modeled from digital R, G, and B in the CRT as shown in Equation 3 below.

Where δ _CRT is the scaling factor for the CRT, X _Rmax , X _Gmax , X _Bmax , Y _Rmax , Y _Gmax , Y _Bmax , Z _Rmax , Z _Gmax , Z _Bmax represent the tristimulus values of CRT representing the maximum brightness of R, G and B respectively, and L _Rmax (R _CRT / 255) ^γ , L _Rmax (G _CRT / 255) ^γ , L _Rmax (B _CRT / 255) ^γ represents the brightness according to the grayscale values R _CRT , G _CRT , and B _CRT of R, G, and B, respectively. Next, the tristimulus values are modeled from digital R, G, and B on the LCD as shown in Equation 4 below.

Where δ _LCD is the scale factor for the LCD, _{X Mod_R, X Mod_G, X Mod_B} , Y Mod_R, Y Mod_G, Y Mod_B, Z Mod_R, Z Mod_G, Z Mod_B represents the R, G, tristimulus values of B each ideal LCD obtained by the above-mentioned equation 2 R _LCD , G _LCD and B _LCD indicate the R, G and B gray scale values of the calibrated LCD. The same color as CRT is assumed in the LCD on the assumption that the tristimulus values (X _CRT , Y _CRT , Z _CRT ) of the _CRT and the tristimulus values (X _LCD , Y _LCD , Z _LCD ) of the CRT modeled as The gray scale values (R _LCD , G _LCD , B _LCD ) of the corrected R, G, and B for reproduction can be obtained as shown in Equation 5 below.

Here, the matrix M may be obtained by using Equations 3 and 4 above. The color correction circuit using the method of obtaining the gray value of the corrected R, G, B for the same color reproduction as the CRT in the LCD can be implemented as shown in FIG.

Referring to FIG. 6, the LCD color correction circuit according to the first embodiment converts input digital R, G, and B values into a matrix to output tristimulus values (X _CRT , Y _CRT , Z _CRT ) according to CRT characteristics. First and second scale factor units 22 and 24 for normalizing the tristimulus values (X _CRT , Y _CRT , Z _CRT ) from the transform unit 20 and the CRT matrix transform unit 20 using the scale factor. And digital R, G, and B values of the LCD corrected to have the same color reproducibility as the CRT by inverse matrix conversion of the tristimulus values (X _LCD , Y _LCD , and Z _LCD ) from the second scale factor unit 24. i) CRT inverse matrix converter 26 for outputting _LCD , G (j) _LCD , B (k) _LCD ).

The CRT matrix converter 20 converts the input digital R, G, and B values into a matrix by using the CRT matrices shown in Equation 3 to generate tristimulus values (X _CRT , Y _CRT) by R, G, and B in the _CRT. , Z _CRT ).

The first and second scale factor units 22 and 24 have a predetermined first considering the CRT and LCD brightness characteristics in the tristimulus values X _CRT , Y _CRT , and Z _CRT of the CRT calculated from the CRT matrix converter 20. And second scale factors to normalize. Here, the first scale factor unit 22 multiplies the tristimulus values (X _CRT , Y _CRT , Z _CRT ) from the CRT matrix converter 20 by the first scale factor in consideration of the brightness characteristics of the CRT, and the second scale factor. unit 24 first tristimulus values from the first scale factor unit 22, the tristimulus value on the LCD by multiplying the second-scale factor taking into account the brightness characteristic of the LCD to (X _LCD, Y _LCD, Z _LCD) (X _LCD, Y _LCD , Z _LCD ).

The CRT inverse matrix converter 26 is an ideal tristimulus value for correcting the black error and color interference of the tristimulus values (X _LCD , Y _LCD , Z _LCD ) from the second scale factor unit 24 as shown in Equation 4. The R, G, and B gray scale values (R (i) _LCD , G (j) _LCD , and B (k) _LCD ) are calculated by performing matrix transformation using an inverse matrix for a matrix representing.

When the digital R, G, and B gray scale values (R (i) _LCD , G (j) _LCD , B (k) _LCD ), which are corrected through the color correction circuit, are supplied to the LCD, the LCD has the same color reproduction characteristics as the CRT. Will have

Meanwhile, the tristimulus values (X _LCD , Y _LCD , Z _LCD ) of the LCD modeled as in Equation 4 may be separated by R, G, and B items as shown in Equation 6 below.

Here, the tristimulus values for R, G, and B separated from each other may be expressed by Equation 7 by multiplying the color coordinates of R having a constant coordinate with each of the scale factors a, b, and c.                     

는 상기 수학식 2의 X_{MOD R(i)}의 x좌표들을 평균한 값이다. 상기 수학식 7에서 a, b, c는 다음 수학식 8에 의해 얻어낼 수 있게 된다.here,

Is an average value of x coordinates of X _{MOD R (i)} of Equation 2 above. In Equation 7, a, b, and c can be obtained by Equation 8 below.

From the a, b and c obtained here, the tristimulus values of the LCD can be separated into the tristimulus values components of R, G and B. By comparing the tristimulus values of the R components thus separated with respect to the entire gray scale values using the lookup table, the corrected gray scale values of R can be obtained. The color correction circuit using the method of correcting the gray scale values of R, G, and B for the same color reproduction as the CRT in the LCD may be implemented as shown in FIG. 7.

Referring to FIG. 7, the LCD color correction circuit according to the second embodiment converts the input digital R, G, and B values into a matrix, and outputs a tristimulus value (X _CRT , Y _CRT , Z _CRT ) corresponding to the CRT characteristics. First and second scale factor units 32 and 34 for normalizing the tristimulus values (X _CRT , Y _CRT , Z _CRT ) from the transform unit 30 and the CRT matrix transform unit 30 using scale factors. And an RGB separator 36 for separating the tristimulus values (X _LCD , Y _LCD , Z _LCD ) from the second scale factor unit 34 by R, G, and B, and in the RGB separator 36. R-table for converting each of the tristimulus values for separated R, G, and B into corrected grayscale values (R (i) _LCD , G (j) _LCD , and B (k) _LCD ) 38, a G-table 40 and a B-table 42.

The CRT matrix converter 30 converts the input digital R, G, and B values by matrix transformation using the CRT matrices shown in Equation 3 (X _CRT , Y _CRT by R, G, and B in the _CRT). , Z _CRT ).

The first and second scale factor units 32 and 34 are a predetermined first considering the CRT and LCD brightness characteristics in the tristimulus values (X _CRT , Y _CRT , Z _CRT ) of the CRT calculated from the CRT matrix converter 30. And second scale factors to normalize. Here, the first scale factor unit 32 multiplies the tristimulus values (X _CRT , Y _CRT , Z _CRT ) from the CRT matrix converter 30 by the first scale factor considering the brightness characteristics of the CRT, and the second scale factor. The unit 34 multiplies the tristimulus values (X _LCD , Y _LCD , Z _LCD ) from the first scale factor unit 32 by the second scale factor in consideration of the brightness characteristics of the LCD, and the tristimulus values (X _LCD , Y _{LCD) on the LCD.} , Z _LCD ).

The RGB separation unit 36 uses three equations (X _{R LCD} , Y _{R LCD} , Z _{R LCD} ) for each of R, G, and B using Equations 6 to 7 (X _{G LCD} , Y _{G LCD} , and Z _{B). LCD} ) (X _{B LCD} , Y _{B LCD} , Z _{B LCD} ) will be separated.

The R-table 38 converts the gray level value R (R () corrected by linearly converting the tristimulus values (X _{R LCD} , Y _{R LCD} , Z _{R LCD} ) for _R from the RGB separation unit 36 to the corresponding gray level values. i) _LCD ) will be printed out. The G-table 40 converts the gray level value G (G () of the G value corrected by linearly converting the tristimulus values (X _{G LCD} , Y _{G LCD} , Z _{G LCD} ) for _G from the RGB separation unit 36 to the corresponding gray level values. j) _LCD ) will be displayed. The B-table 42 adjusts the gray scale value B of the B corrected by linearly converting the tristimulus values (X _{B LCD} , Y _{B LCD} , Z _{B LCD} ) for _B from the RGB separation unit 36 to the corresponding gray scale values. k) _LCD ) will be displayed. The R-table 38, G-table 40 and B-table 42 implement the ideal tristimulus values (X _MOD , Y _MOD , Z _MOD ) obtained by correcting the above equations for color leakage errors and black errors. The linear values are converted into the gray scale values (R (i) _LCD , G (j) _LCD , and B (k) _LCD ) of the corrected R, G, and B values using the values obtained during the test.

When the digital R, G, and B gray scale values (R (i) _LCD , G (j) _LCD , B (k) _LCD ), which are corrected through the color correction circuit, are supplied to the LCD, the LCD has the same color reproduction characteristics as the CRT. Will have

As described above, the method of applying the color correction circuit shown in FIGS. 6 and 7 to the liquid crystal display device is various. As an example, as shown in FIG. 8, the color compensator 54 is connected between the timing controller 52 and the data driver 56.

Referring to FIG. 8, a liquid crystal panel 60 in which liquid crystal cells are arranged in a matrix form, a gate driver 58 for driving gate lines G0 to Gn of the liquid crystal panel 60, and a liquid crystal panel 60. A data driver 56 for driving the data lines D1 to Dm, a timing controller 52 for controlling the driving timing of the data driver 56 and the gate drive 58, and a data driver 56. And a color compensator 54 provided between the timing controller 52 and the video card 50 for supplying video data to the timing controller 52.

The video card 50 converts and supplies the input video data R, G, and B to suit the resolution of the liquid crystal panel 60. The video card 50 also supplies synchronization signals such as a main clock signal, a vertical synchronization signal and a horizontal synchronization signal suitable for the resolution.

The timing controller 52 relays the video data R, G, and B from the video card 50 to the color compensator 54. The timing controller 52 also generates various control signals for controlling the driving of the data and gate drivers 56 and 58 using the synchronization signals from the video card 50.

The color compensator 54 corrects and outputs the video data R, G, and B from the timing controller 52 to have the same color reproducibility as the CRT as described above.

The gate driver 58 sequentially supplies the gate high voltage signal to the gate lines G1 to Gn of the liquid crystal panel 60 according to a control signal from the timing controller 52.

The data driver 56 converts the video data R, G, and B from the color compensator 54 into video voltage signals, which are analog signals, using gamma voltages from a gamma circuit (not shown). The data driver 56 supplies one horizontal line of video voltage signals to the data lines D1 through Dm every one horizontal period in which the gate high voltage signals are supplied to the gate lines G1 through Gn.

The liquid crystal panel 60 is a liquid crystal connected to the thin film transistor TFT formed at the intersection of the gate lines G1 to Gn and the data lines D1 to Dm, and the thin film transistor TFT and arranged in a matrix form. With cells. The thin film transistor TFT supplies a video signal from the data lines D1 to Dm to the liquid crystal cell in response to the gate high voltage signal from the gate lines G1 to Gn. The liquid crystal cell is equivalently represented by the liquid crystal capacitor Clc because the liquid crystal cell is composed of a common electrode facing the liquid crystal and a pixel electrode connected to the thin film transistor. The liquid crystal cell also includes a storage capacitor Cst connected to the previous gate line to maintain the data voltage charged in the liquid crystal capacitor Clc until the next data voltage is charged.

In the LCD, the color compensator 54 may be integrated with any one of the data driver 56 and the timing controller 52.

Alternatively, the color compensator 54 may be installed at any one of an input terminal and an output terminal of the video card 50 or may be installed inside the video card 50.

Alternatively, the color compensator 54 may be installed on a path through which the video data signal is transmitted in the system unit in which the video card 50 is mounted.

As described above, the color correction method and apparatus of the liquid crystal display according to the present invention correct the color data by using the tristimulus value modeling the CRT characteristics and the ideal tristimulus value modeling the characteristics of the LCD, so that the same color as the CRT in the LCD Reproduction characteristics can be obtained.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (15)

Calculating tristimulus values modeling the color reproduction characteristics of the liquid crystal display by correcting the tristimulus values, the color leakage errors and the black errors of the color reproduction characteristics of the cathode ray tube; And color correcting the input video data using the calculated tristimulus values of the cathode ray tube and the tristimulus values of the liquid crystal display to have the same color reproduction characteristics as those of the cathode ray tube. Way. The method of claim 1, The color correction step Matrix converting the input video data using the tristimulus values of the cathode ray tube; Normalizing the matrix-converted tristimulus values into tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; And converting the tristimulus values of the liquid crystal display device into an inverse matrix using the tristimulus values of the liquid crystal display device to calculate color corrected video data. The method of claim 1, The color correction step Matrix converting the input video data using the tristimulus values of the cathode ray tube; Normalizing the matrix-converted tristimulus values into tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; Separating the tristimulus values of the liquid crystal display by color; And linearly converting the tristimulus values separated for each color into color correction video data using a color lookup table using video data obtained by calculating tristimulus values of the liquid crystal display. Color correction method. The input video data has the same color reproduction characteristics as the cathode ray tube by using the tristimulus value modeling the color reproduction characteristics of the cathode ray tube, the color leakage error and the black error to correct the color reproduction characteristics of the liquid crystal display device. Color correction; And converting the color corrected video data into a video voltage signal which is an analog signal and supplying the color data to a liquid crystal panel. The method of claim 4, wherein The color correction step Matrix converting the input video data using the tristimulus values of the cathode ray tube; Normalizing the matrix-converted tristimulus values into tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; And converting the tristimulus values of the liquid crystal display device into an inverse matrix using the tristimulus values of the liquid crystal display device to calculate the color corrected video data. The method of claim 4, wherein The color correction step Matrix converting the input video data using the tristimulus values of the cathode ray tube; Normalizing the matrix-converted tristimulus values into tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; Separating the tristimulus values of the liquid crystal display by color; And linearly converting the tristimulus values separated by color into the color correction video data using a color lookup table using video data obtained by calculating tristimulus values of the liquid crystal display. Driving method. The input video data has the same color reproduction characteristics as the cathode ray tube using the tristimulus value modeling the color reproduction characteristics of the cathode ray tube, and the tristimulus value modeling the color reproduction characteristics of the liquid crystal display device by correcting the color leakage error and black error. And a color correction circuit for color correction. The method of claim 7, wherein The color correction circuit A cathode ray tube matrix converter for matrix converting the input video data using the tristimulus values of the cathode ray tube; A scale factor unit for normalizing the matrix converted tristimulus values to tristimulus values of the liquid crystal display using at least one scale factor using brightness characteristics of the cathode ray tube and the liquid crystal display; And an inverse matrix converting unit configured to perform inverse matrix conversion of the tristimulus values of the liquid crystal display device to calculate color corrected video data using the tristimulus values of the liquid crystal display device. The method of claim 7, wherein The color correction circuit A cathode ray tube matrix converter for matrix converting the input video data using a tristimulus value of the cathode ray tube; A scale factor unit for normalizing the matrix-stimulated tristimulus values to tristimulus values of a liquid crystal display using at least one scale factor using brightness characteristics of a cathode ray tube and a liquid crystal display; A color separation unit for separating tristimulus values of the liquid crystal display by color; And a red, green, and blue lookup table for linearly converting the tristimulus values separated for each color into color correction video data using the video data obtained when calculating the tristimulus values of the liquid crystal display. Color correction device. A liquid crystal panel in which liquid crystal cells are arranged in a matrix form, A gate driver for driving gate lines of the liquid crystal panel; A data driver for driving data lines of the liquid crystal panel; A timing controller for controlling driving timing of the data driver and the gate drive using a synchronization signal input from a video card; The video data input from the timing controller is the same color as the cathode ray tube using the tristimulus value modeling the color reproduction characteristics of the cathode ray tube, and the tristimulus value modeling the color reproduction characteristics of the liquid crystal display device by correcting the color leakage error and black error. And a color correction circuit for correcting color to have reproduction characteristics and supplying the data driver to the data driver. The method of claim 10, The color correction circuit A cathode ray tube matrix converter for matrix converting the input video data using the cathode ray tube tristimulus values; A scale factor unit for normalizing the matrix-stimulated tristimulus values to tristimulus values of a liquid crystal display using at least one scale factor using brightness characteristics of a cathode ray tube and a liquid crystal display; And an inverse matrix converting unit configured to inversely matrix convert the tristimulus values of the liquid crystal display device using the tristimulus values of the liquid crystal display device to calculate the color-corrected video data. The method of claim 10, The color correction circuit A cathode ray tube matrix converter for matrix converting the input video data using a tristimulus value of the cathode ray tube; A scale factor unit for normalizing the matrix-stimulated tristimulus values to tristimulus values of a liquid crystal display using at least one scale factor using brightness characteristics of a cathode ray tube and a liquid crystal display; A color separation unit for separating tristimulus values of the liquid crystal display by color; And a red, green, and blue lookup table for linearly converting the tristimulus values separated for each color into color correction video data using the video data obtained when calculating the tristimulus values of the liquid crystal display. . The method of claim 10, And the color correction circuit is integrated with any one of the data driver and the timing controller. The method of claim 10, And the color correction circuit is installed at any one of an input terminal and an output terminal of the video card or is installed inside the video card. The method of claim 10, And the color correction circuit is provided on a path through which a video data signal is transmitted in a system unit in which the video card is mounted.

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