KR20070069411A - Gamma correction device, gamma correction method and liquid crystal display device having the same - Google Patents

Abstract

A gamma compensating apparatus and method, and an LCD device using the same are provided to equalize luminance of light emitting diodes by adjusting red, green, and blue light emitting diodes to be emitted based on a predetermined duty value. An LCD(Liquid Crystal Display) device includes a liquid crystal panel(35), a gate driver(32), a data driver(33), a backlight unit(17), and a gamma compensating unit(10). The liquid crystal panel includes plural gate and data lines arranged in a matrix form. The gate driver supplies a predetermined scan signal to the gate lines of the liquid crystal panel. The data driver supplies a data voltage, which is modulated from an image, to data lines of the liquid crystal panel. The backlight unit includes first to third light emitting diodes, which emit first to third lights to be radiated to the liquid crystal panel. The gamma compensating unit obtains duty values about first to third data of the image. The first to third light emitting diodes are driven by the duty values.

Description

Gamma correction device, gamma correction method and liquid crystal display device having same {Gamma correction device, gamma correction method and liquid crystal display device having the same}

1 is a block diagram schematically illustrating a general liquid crystal display device.

2 is a diagram illustrating a gamma correction device according to the present invention.

3 is a block diagram illustrating in detail the image analyzer of FIG. 2;

4 is a graph showing a histogram distribution calculated by the histogram calculator of FIG. 3.

5 is a graph depicting each gamma curve of red, green, and blue light emitting diodes.

6 is a block diagram showing a liquid crystal display device having a gamma correction device according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: gamma correction device 11: the image analysis unit

13: Duty control unit 15: LUT table

17: backlight unit 22: data alignment unit

24: histogram calculator 26: average luminance calculator

30: timing controller 31: signal controller

32: gate driver 33: data driver

34: backlight driver 35: liquid crystal panel

The present invention relates to a gamma correction device, and more particularly, to a gamma correction device, a gamma correction method, and a liquid crystal display device having the same of an RGB light emitting diode.

Flat panel displays that have the advantages of light and thin have been in the spotlight. The flat panel display includes a plasma display panel, a field emission display, a light emitting diode, and a liquid crystal display.

In the liquid crystal display, a data signal is supplied to pixels arranged in an active matrix form, and a predetermined image is displayed by the amount of light transmitted adjusted according to the supplied data signal.

However, since the liquid crystal display device does not spontaneously generate light, the liquid crystal display device includes a backlight unit capable of irradiating light to the bottom of the liquid crystal panel.

1 is a block diagram schematically illustrating a general liquid crystal display.

As shown in FIG. 1, a general liquid crystal display device includes a timing controller 1, a gate driver 2, a data driver 3, a liquid crystal panel 4, a backlight driver 5, and a backlight unit 6. Include.

The timing controller 1 receives a video signal and vertical / horizontal synchronization signals Vsync and Hsync from an external device (eg, a video system), and uses the vertical / horizontal synchronization signal to control the gate driver 2 and data driver ( 3) generate first and second control signals for driving 3) and backlight control signals for driving the backlight driver 5.

The gate driver 2 sequentially supplies a predetermined scan signal to the liquid crystal panel 4 in response to the first control signal.

The data driver 3 converts the video signal into an analog data voltage reflecting a gamma value according to the second control signal and supplies the converted video signal to the liquid crystal panel 4.

The backlight driver 5 generates a backlight driving voltage for driving the backlight unit 6 according to the backlight control signal.

In the liquid crystal panel 4, a plurality of gate lines and a plurality of data lines are vertically intersected, a thin film transistor is disposed at an intersection point of each line, and a pixel electrode is connected to the thin film transistor. The common electrode corresponding to the pixel electrode is disposed in the liquid crystal panel.

In the backlight unit 6, a red (R) light emitting diode 7a, a green (G) light emitting diode 7b, and a blue (B) light emitting diode 7c are arranged in basic units. White light is produced by mixing the red (R) light emitting diode 7a, the green (G) light emitting diode 7b, and the blue (B) light emitting diode 7c.

Accordingly, the plurality of gate lines of the liquid crystal panel 4 are sequentially driven by a predetermined scan voltage, and the thin film transistors on the gate lines are turned on. In this case, the analog data voltage supplied from the data driver 3 is supplied to the plurality of data lines of the liquid crystal panel 4. The analog data voltage supplied to the data line is supplied to the pixel electrode via the thin film transistor. In addition, a predetermined common voltage is supplied to the common electrode. Accordingly, a potential difference corresponding to a difference between the analog data voltage and the common voltage is generated between the pixel electrode and the common electrode, an electric field is generated by the potential difference, and the liquid crystal is displaced by the electric field, and the displaced liquid crystal According to the red (R) light emitting diode (7a), green (G) light emitting diode (7b) and blue (B) light emitting diode (7c) of the backlight unit 6 according to the red (R) light, green (G) ) A predetermined image is displayed by the transmission or blocking of white light, which is a mixed light of light and blue (B) light.

The conventional backlight unit 6 can achieve high luminance light by using a red (R) light emitting diode 7a, a green (G) light emitting diode 7b, and a blue (G) light emitting diode 7c. In addition, by using the light emitting diodes 7a, 7b, and 7c, power consumption is reduced, and since it is semi-permanent, a long lifetime backlight can be obtained.

However, the red (R) light emitting diode, the green (G) light emitting diode, and the blue (B) light emitting diode have different gamma curves due to their different characteristics and the characteristics of the panel.

Therefore, since the luminance of each light emitting diode is not the same, a luminance deviation occurs between the light emitting diodes, and the color tone also becomes different according to each gamma curve, which causes a problem of poor image quality.

According to the present invention, by supplying an optimum duty value according to an image for each frame, the luminance of the red, green, and blue light emitting diodes is the same, and the color tone of each light emitting diode is the same, so that the image quality is improved by uniform brightness and color tone. An object of the present invention is to provide a gamma correction device, a gamma correction method, and a liquid crystal display device having the same.

According to a first exemplary embodiment of the present invention for achieving the above object, a gamma correction method includes: extracting first to third grayscales corresponding to average luminance of first to third data of an image; And obtaining a duty value according to the extracted first to third grayscales using the LUT table.

According to a second embodiment of the present invention, a gamma correction apparatus includes: an image analyzer extracting first to third gray levels corresponding to average luminance of first to third data of an image; And a duty controller for obtaining a duty value according to the extracted first to third grayscales using the LUT table.

According to a third embodiment of the present invention, a liquid crystal display device includes: a liquid crystal panel in which a plurality of gate lines and a plurality of data lines are arranged in a matrix form; A gate driver for supplying a predetermined scan signal to the plurality of gate lines of the liquid crystal panel; A data driver for supplying a data voltage obtained by modulating a predetermined image to the plurality of data lines of the liquid crystal panel; A backlight unit in which first to third light emitting diodes emitting first to third light for irradiating the liquid crystal panel are arranged; And a gamma correction unit configured to obtain a duty value for the first to third data of the image, and drive the first to third light emitting diodes with the duty value for the first to third data.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

2 is a diagram illustrating a gamma correction apparatus according to the present invention.

Referring to FIG. 2, the gamma correction apparatus 10 according to the present invention includes an image analyzer 11, a duty controller 13, and an LUT table 15. A backlight unit 17 is connected to the duty controller 13 to emit red (R), green (G), and blue (B) light emitting diodes of the backlight unit 17 under the control of the duty controller 13. .

A backlight driver (not shown) may be added between the duty controller 13 and the backlight unit 17, but will be omitted for convenience of description.

As shown in FIG. 3, the image analyzer 11 includes a data aligner 22 for arranging red (R) data, green (G) data, and blue (B) data from an image of one frame, and A histogram calculator 24 for calculating a histogram distribution for each of the red (R) data, the green (G) data, and the blue (B) data arranged by the data arranging unit 22, and the histogram calculator 24. And an average brightness calculator 26 for calculating the average brightness for each data based on the histogram distribution and extracting a gray level corresponding to the calculated average brightness.

If an image of one frame has a size of 6 * 9, 18 pieces of red (R) data, green (G) data, and blue (B) data exist. Accordingly, the data alignment unit 22 sorts 18 red (R) data, 18 green (G) data, and 18 blue (B) data from an image of one frame.

The histogram calculator 24 calculates individual histogram distributions of 18 pieces of red (R), green (G), and blue (B) data.

For example, the histogram distribution for the red (R) data can be calculated as shown in FIG. 4. That is, one 10 gradation, three 38 gradations, four 68 gradations, five 125 gradations, four 143 gradations, one 178 gradations, and five 256 gradations can be calculated.

The average luminance calculator 26 calculates a luminance average based on the number of grays calculated by the histogram calculator 24, and extracts a gray level corresponding to the calculated luminance average. For example, the average luminance of the histogram distribution shown in FIG. 4 is calculated to be (1 + 3 + 4 + 5 + 4 + 1 + 5) /7=3.29. Therefore, the average luminance will be the average luminance represented by the gray scale having approximately 3.3 distributions. Therefore, when 3.3 pieces are applied to the histogram distribution shown in Fig. 4, approximately 40 tones (red tones) can be extracted.

Similarly, the green and blue gray levels corresponding to the average luminance can be extracted for the green (G) data and the blue (B) data by the same process.

The duty controller 13 compares the red, green, and blue gray levels of the red (R), green (G), and blue (B) data extracted by the image analyzer 11 to the LUT table 15 to determine the duty. Adjust the value.

To this end, the duty value for each gray level is set in the LUT table 15 as a table.

The LUT table 15 may be set based on data measured through an experiment. Hereinafter, a method of setting the LUT table 15 will be described in detail.

As shown in FIG. 5, red (R) gamma curves, green (G) gamma curves, and blue (B) gamma curves for red (R) light emitting diodes, green (G) light emitting diodes, and blue (B) light emitting diodes. Have different curve distributions.

In this case, the gamma curve is first selected in a predetermined gradation unit (for example, 64 gradations). For example, if it is selected in units of 64 gray levels, 64 gray levels, 128 gray levels, 192 gray levels, and 256 gray levels are selected.

The luminance difference between the reference value and the measured value for the selected gray scale is calculated. As illustrated in FIG. 5, the reference value refers to a luminance value for each gray scale unit shown on each gamma curve, and the measured value refers to a value actually measured through experiments for each gray scale unit.

Therefore, the luminance difference between the reference value and the measured value is calculated for each of the 64, 128, 192, and 256 gray levels for the red gamma curve. Similarly, the luminance difference between the reference value and the measured value is calculated for each of the 64, 128, 192, and 256 gray levels for the green (G) gamma curve, and the 64, 128, 192 gray levels for the blue (B) gamma curve. And a luminance difference value between the reference value and the measured value every 256 gradations.

The duty value corresponding to this luminance difference value is calculated. The duty value may be calculated through an experiment or may be calculated by a calculation formula. In the present invention, it does not matter whether the result is an experiment or a calculation formula, but only a duty value is calculated based on the luminance difference value.

Therefore, the duty values calculated for each unit gray level are tabled in the LUT table 15 for each of the red (R) gamma curve, the green (G) gamma curve, and the blue (B) gamma curve. The LUT table 15 thus comprises a red (R) LUT table, a green (G) LUT table and a blue (B) LUT table. In the red (R) LUT table, the duty value for each gray level is set for red (R), and in the green (G) LUT table, the duty value for each gray level is set for green (G), and blue (B) In the LUT table, a duty value for each gray level for blue (B) is set.

The duty controller 13 applies red, green, and blue gray levels to the red (R), green (G), and blue (B) data extracted from the image analyzer 11 using the LUT table 15. Get duty value accordingly.

As described above, since the duty value according to the unit gray level is set in the LUT table 15, an optimal duty value is obtained by matching the gray level for each data extracted by the image analyzer 11 to the LUT table 15. Get Since the duty value is set only for arbitrary unit gray scales (eg, 64 gray scales, 128 gray scales, 192 gray scales, 256 gray scales, etc.) in the LUT table 15, there is no gray scale extracted by the image analyzer 11. You may not. That is, the gradation extracted by the image analyzer 11 may extract any gradation between 0 and 255 gradations. On the other hand, the LUT table 15 selects only a few unit grays having representativeness and has a corresponding duty value.

Therefore, in most cases, the duty value corresponding to the gray level extracted by the image analyzer 11 may obtain an appropriate duty value by using interpolation between arbitrary unit grays set in the LUT table 15.

Of course, the duty controller 13 may obtain not only the red gray level extracted by the image analyzer 11, but also the red duty value, the green duty value, and the blue duty value corresponding to the green and blue gray levels.

The duty controller 13 obtains a red duty value, a green duty value, and a blue duty value corresponding to the red, green, and blue grays extracted by the image analyzer 11 using the LUT table 15. The ground, the red duty value, the green duty value and the blue duty value cause the corresponding red (R) light emitting diode, green (G) light emitting diode and blue (B) light and the diode of the backlight unit 17 to emit light.

6 is a block diagram showing a liquid crystal display device having a gamma correction device according to the present invention.

Referring to FIG. 6, the liquid crystal display of the present invention includes a timing controller 30, a gate driver 32, a data driver 33, a liquid crystal panel 35, a backlight driver 34, and a backlight unit 17. It includes.

The timing controller 30 receives a video signal (e.g., an image in a frame unit, hereinafter referred to as a frame) and a vertical / horizontal synchronization signal (Vsync, Hsync) from the outside (eg, a video system).

The timing controller 30 includes a signal controller 31 for generating first and second control signals for driving the gate driver 32 and the data driver 33 by using the vertical / horizontal synchronization signal, and frame unit. According to the image of the red (R) light emitting diode 18a, the green (G) light emitting diode 18b, and the blue (B) light emitting diode 18c of the backlight unit 17, the red and green colors are the same. And a gamma correction device for varying the blue duty value to emit the red (R) light emitting diode 18a, the green (G) light emitting diode 18b, and the blue (B) light emitting diode 18c of the backlight unit 17. 10) including.

The gamma correction apparatus 10 includes an image analyzer 11, a duty controller 13, and an LUT table 15.

The image analyzer 11 extracts a gray level corresponding to the average luminance of the red (R), green (G), and blue (B) data from the image of one frame unit.

In the LUT table 15, a duty value for each gray level is set for each gamma curve through experiments with red (R), green (G), and blue (B) gamma curves.

The duty controller 13 may perform the LUT table based on the red, green, and blue gray levels corresponding to the average luminance of the red (R), green (G), and blue (B) data extracted by the image analyzer 11. By using (15), red, green and blue duty values corresponding to red, green and blue gray levels corresponding to average luminance of the red (R), green (G) and blue (B) data are obtained.

This duty value is continuously obtained for each frame image. As a result, the duty value is changed for each image.

Since the LUT table 15 has a duty value for each gamma curve set for each gamma curve through experiments with red (R), green (G), and blue (B) gamma curves, the LUT table 15 is replaced with the LUT table 15. The duty value obtained by using means the value so that it may become the same brightness | luminance and the same color tone with respect to each gamma curve.

The gate driver 32 sequentially supplies a predetermined scan signal to the liquid crystal panel 35 in response to the first control signal.

The data driver 33 converts the video signal into an analog data voltage reflecting a gamma value and supplies the converted video signal to the liquid crystal panel 35 according to the second control signal.

The backlight driver 34 generates a backlight driving voltage for driving the backlight unit 17 according to the backlight control signal.

In the liquid crystal panel 35, a plurality of gate lines and a plurality of data lines are vertically intersected, a thin film transistor is disposed at an intersection point of each line, and a pixel electrode is connected to the thin film transistor. As a result, the liquid crystal panel 35 may have the plurality of gate lines and the plurality of data lines arranged in a matrix. The common electrode corresponding to the pixel electrode is disposed on the liquid crystal panel 35.

In the backlight unit 17, a red (R) light emitting diode 18a, a green (G) light emitting diode 18b, and a blue (B) light emitting diode 18c are arranged in basic units. White light is produced by mixing the red (R) light emitting diode 18a, the green (G) light emitting diode 18b, and the blue (B) light emitting diode 18c.

The backlight driver 34 converts the red, green, and blue current values according to the red, green, and blue duty values obtained by the duty controller 13 of the timing controller 30. The luminance of the red (R) light emitting diode 18a of the backlight unit 17 is controlled by the red current value changed in the backlight driver 34, and the green light emitting diode 18b of the green (G) current value is controlled. The luminance is controlled, and the luminance of the blue (B) light emitting diode 18c is controlled by the blue current value. When the light emitting diodes 18a, 18b, and 18c of the backlight unit 17 emit light by the red, green, and blue duty values obtained by the duty controller 13, the luminance of each light emitting diode is the same and the color tone is also the same. As a result, uniform luminance and color tone can be obtained, so that image quality can be improved.

As described above, the present invention sets the duty value for the representative unit gray level for each data so that the luminance and the color tone of each light emitting diode are the same, and red, green, and Red, green, and blue gray scales corresponding to the average luminance are extracted for the blue data, and the duty value corresponding to each gray scale is obtained using the set duty value, and the red, green, and blue colors are used. (B) By emitting light emitting diodes, the luminance of each light emitting diode is the same and the color tone is also the same, so that uniform brightness and color tone can be obtained, so that image quality can be improved.

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 (12)

Extracting first to third grayscales corresponding to average luminance of the first to third data of the image; And And obtaining a duty value according to the extracted first to third grayscales using an LUT table. The gamma correction method of claim 1, wherein a duty value for a representative gray level is set in the LUT table. The gamma correction method of claim 1, wherein the average luminance is calculated from a histogram distribution of the respective data. The gamma correction method of claim 1, wherein the first to third data are red data, green data, and blue data. The method of claim 1, further comprising performing the above steps on an image of every frame unit.  An image analyzer extracting first to third gray levels corresponding to average luminance of first to third data of the image; And And a duty controller to obtain a duty value according to the extracted first to third grayscales using an LUT table. The gamma correction device according to claim 6, wherein a duty value for a representative grayscale is set in the LUT table. 7. The gamma correction device of claim 6, wherein the average luminance is calculated from a histogram distribution for each of the data. The gamma correction device of claim 6, wherein the first to third data are red data, green data, and blue data. A liquid crystal panel in which a plurality of gate lines and a plurality of data lines are arranged in a matrix form; A gate driver for supplying a predetermined scan signal to the plurality of gate lines of the liquid crystal panel; A data driver for supplying a data voltage obtained by modulating a predetermined image to the plurality of data lines of the liquid crystal panel; A backlight unit in which first to third light emitting diodes emitting first to third light for irradiating the liquid crystal panel are arranged; A gamma correction unit configured to obtain a duty value for first to third data of the image, And driving the first to third light emitting diodes with a duty value for the first to third data. The method of claim 10, wherein the gamma correction unit, An image analyzer extracting first to third gray levels corresponding to average luminance of first to third data of the image; And And a duty controller configured to obtain a duty value according to the extracted first to third grayscales by using an LUT table. 12. The liquid crystal display device according to claim 11, wherein a duty value for a representative gray level is set in the LUT table.

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