KR20060035025A - Liquid crystal display device and driving method thereof - Google Patents

Abstract

The present invention relates to a liquid crystal display device.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes: a memory configured to store a plurality of histograms having different data distribution curves corresponding to light amounts, and a plurality of backlight control signals having different control values corresponding to the light amounts; A system for generating image data and control signals; An external sensing system for generating a contrast control signal according to the amount of light in the external environment; An internal processing system for selecting a histogram and a backlight control signal corresponding to the contrast and luminance modulated in response to the image data and the control signal and the variable signal; And a lamp driver for controlling contrast and brightness of the liquid crystal panel in response to a backlight control signal from the internal processing system.

Description

Liquid Crystal Display Device and Driving Method             

1 is a view showing a conventional liquid crystal display device.

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

FIG. 3 is a detailed view of the external sensing system of FIG. 2.

4 is a detailed view of the internal processing system of FIG. 2.

5 is a view illustrating in detail the image quality processor of FIG. 4.

6 is a view showing in detail the lamp driving unit of FIG.

FIG. 7 illustrates an example of histogram types stored in the lookup table of FIG. 2.

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

11, 22: liquid crystal display panel 12: backlight unit

14 power supply 20 timing control unit

24: data driver 26: gate driver

28: gamma voltage supply unit 30: internal processing system                 

32: image quality processing unit 34: exchanger

35: system 36: memory

40: external sensing system 42: determination unit

44: detector 52: IC master controller

53: look-up table 54: luminance color separation unit

55: histogram analysis unit 56: MAX (RGB)

57: luminance color mixing unit 58: window

59: backlight control unit 60: lamp drive unit

62: feedback circuit 64: PWM controller

66: inverter 69: lamp

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of adjusting contrast according to an external environment.

In general, a liquid crystal display (LCD) displays an image by adjusting light transmittance of liquid crystal cells according to a video signal.

Among the liquid crystal display devices, an active matrix type liquid crystal display device is advantageous for realizing a moving image because active control of a switching element is possible. As a switching device used in an active matrix liquid crystal display device, a thin film transistor (hereinafter, referred to as TFT) is mainly used.

In recent years, the liquid crystal display device has been expanding its application field from display devices and monitors of office equipment to televisions.

1 is a view showing a conventional liquid crystal display device.

Referring to FIG. 1, a conventional liquid crystal display device is manufactured in a transmissive type in which a backlight unit 12 is provided on a rear surface of a liquid crystal display panel 11. The liquid crystal display panel 11 of the transmissive liquid crystal display device displays an image by adjusting the transmittance of light incident from the backlight unit 12 according to video data as shown in FIG. 1.

The backlight unit 12 includes a lamp, a light guide plate for converting a line light source from the lamp into a surface light source, and an optical sheet such as a diffusion sheet and a prism sheet for increasing the uniformity and efficiency of the light. The lamp of the backlight unit 12 generates a discharge in the discharge tube between the anode and the cathode in accordance with the tube current from the inverter 14 to generate white light.

The inverter 14 converts the DC power from the power source 13 into an AC power and boosts the AC power to generate a tube current.

The brightness of the backlight unit 12 is fixed. For this reason, the LCD cannot adjust the contrast ratio according to the change of the external environment, and as the external environment changes, the user feels the contrast deteriorated and the image quality deteriorates even though the same contrast is maintained. Accordingly, various techniques for improving contrast by adapting to changes in the external environment are required.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of adjusting contrast according to a change in an external environment.

In order to achieve the above object, a liquid crystal display according to an exemplary embodiment of the present invention includes a memory for storing a plurality of histograms having different data distribution curves corresponding to the amount of light and a plurality of backlight control signals having different control values corresponding to the amount of light; ; A system for generating image data and control signals; An external sensing system for generating a contrast control signal according to the amount of light in the external environment; An internal processing system for selecting a histogram and a backlight control signal corresponding to the contrast and luminance modulated in response to the image data and the control signal and the variable signal; And a lamp driver for controlling contrast and luminance of the liquid crystal panel in response to a backlight control signal from the internal processing system.

The external sensing system includes a sensing unit having at least one optical sensor for sensing a change in an external environment; And a determination unit generating a contrast variable signal according to the amount of light detected by the detection unit.

The internal processing system includes a switch for receiving a variable signal from the external processing system; An image quality processor which receives a signal from the switch and modulates image data and a control signal from the system; The image processing unit includes a memory for supplying different histogram types and backlight control signals according to the histogram types.

The image quality processing section (IC) which communicates with the memory and the exchanger to receive a histogram from the memory and receives a variable signal from the exchange; A luminance color separator for separating the image data from the system into luminance and color; A maximum value detector for detecting a color signal having a maximum value among the image data from the system; A window for varying a control signal from the system and setting a histogram analysis area; A histogram analyzer for analyzing the histogram using a luminance signal from the luminance color separator and a color signal having a maximum value, a variable signal from an IC master controller, and a histogram in the histogram analysis region set by the window; A look-up table for selecting a histogram and a backlight control signal corresponding to a combination of the histogram analysis unit, the variable signal from the IC master controller, and the luminance signals; A luminance color mixing unit for generating image data by combining the luminance signal of the histogram selected by the lookup table and the color signal separated by the luminance color separation unit; And a backlight controller for supplying a backlight control signal selected by the lookup table to the lamp driver.

A lamp for generating light of the lamp driver; A feedback circuit for detecting a signal flowing through the lamp; An inverter configured to adjust a voltage level in response to a backlight control signal from the backlight controller; A PWM controller connected between the inverter and the feedback circuit and modulating a pulse width by a backlight control signal from the backlight control unit; And a transformer for boosting the AC signal from the inverter and supplying it to the lamp.

The backlight control signal changes one of the duty ratio of the tube current applied to the lamp and the intensity of the tube current.

A luminance extractor which receives image data and extracts luminance components from the image data; A histogram parameter generator for indicating an attribute of the image data according to the luminance component; An external sensing system for generating a contrast control signal according to the amount of light in the external environment; A memory for storing a plurality of histograms having different data distribution curves corresponding to the amount of light and a plurality of backlight control signals having different control values corresponding to the amount of light; And a selector configured to receive the plurality of histograms and the plurality of other backlight control signals from the memory and select the histogram and the backlight control signal based on the luminance component, the histogram parameter, and the contrast control signal.

The external sensing system includes a sensing unit having at least one optical sensor for sensing a change in an external environment; And a determination unit generating a contrast variable signal according to the amount of light detected by the detection unit.

A liquid crystal display panel; A first system for generating a contrast control signal in accordance with the amount of light in the external environment; A plurality of histogram type information that selects different contrast characteristics of the image data based on the contrast control signal, and a plurality of control values are set differently according to the histogram type information based on the contrast control signal. A second system for selecting any one of the light source control signals; A panel driver supplying image data modulated with the selected histogram type information to the liquid crystal display panel; And a light source for irradiating the liquid crystal display panel with light whose brightness is controlled by the selected light source control signal.

According to an exemplary embodiment of the present invention, there is provided a liquid crystal display driving method comprising the steps of: providing a plurality of histograms having different data distribution curves corresponding to light amounts and a plurality of backlight control signals having different control values corresponding to the light amounts; Generating a contrast control signal according to an external environment; Generating a histogram parameter indicative of a property of the image data according to the input of the image data and the luminance component extracted from the image data;

Selecting the histogram and backlight control signal based on the histogram parameter and the contrast control signal; And supplying the image data modulated with the selected histogram type information to a liquid crystal display panel displaying an image and controlling the brightness of a light source irradiated to the liquid crystal display panel by the selected backlight control signal.

Selecting the histogram and the backlight control signal based on the histogram parameter and the contrast control signal selects a histogram and a backlight control signal having high luminance and contrast when the external environment is bright, and a luminance and Select low-contrast histogram and backlight control signals.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 2 to 7.

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

Referring to FIG. 2, a liquid crystal display according to an exemplary embodiment of the present invention supplies data from a system 35 for generating a signal corresponding to image data, an external sensing system 40, and an external sensing system 40. An internal processing system 30 that receives and generates a modulated image data signal in combination with the image data signal, a backlight unit and a lamp driver 60 that adjust brightness according to a signal generated from the internal processing system 30, and a liquid crystal. A panel 22 and a panel driver are provided.

The system 35 includes 'Vsyn1', 'Hsyn1', 'DCLK1' and 'DE1', that is, vertical / horizontal sync signals Vsyn1, Hsyn1, dot clock DCLK1 and digital video data for sampling of digital video data. A data enable signal DE1 or the like indicating a period in which (Ri, Gi, Bi) is present is generated. An example of such a system 35 is a graphics card.

As illustrated in FIG. 3, the external sensing system 40 includes a sensing unit 44 that senses a change in the external environment, and a determination unit 42 that determines whether the change is made based on data from the sensing unit 44. do.

The detector 44 detects the external light using an optical sensor or the like that can detect a change in the external light. At least one optical sensor may be installed, and the external optical change may be calculated by averaging each optical change amount from one or more optical sensors.

The determination unit 42 generates a contrast ratio adjustment signal corresponding to the amount of light change supplied from the detection unit 44 and supplies it to the internal processing system 30. For example, the detector 44 divides the amount of external light detected by the class, and generates a different signal according to each class. When the amount of external light is the highest, that is, the brightest case is set to 16 grades, and when the amount of the external light is the least, that is, the darkest case is set to grade 1, different signals are generated according to each grade. Here, if the digitization according to the class, it is possible to generate different signals using four bits. However, the liquid crystal display according to the exemplary embodiment of the present invention is not limited to the brightness class in the above-described example. That is, the brightness grade of the external light source according to the embodiment of the present invention can be classified and processed into 2 to 256 grades, and more detailed classification can be made according to a user's request.

The internal processing system 30 that adjusts the contrast according to the data supplied from the determination unit 42 of the external sensing system 40 exchanges data with the external sensing system 40 as shown in FIG. 4. An exchanger 34, an image quality processor 32 that receives data from the switch 34 and generates a signal according thereto, and a histogram type and a backlight control signal which are required for the image quality processor 32 to generate a signal The memory 36 is provided.

The exchanger 34 is positioned between the external sensing system 40 and the image quality processing unit 32 to supply the contrast variable signal generated from the external sensing system 40 to the image quality processing unit 32.

The memory 36 is composed of an EEPROM, and a modulation luminance signal corresponding to the brightness information Y of the input image, a backlight control signal set according to the modulation contrast signal, and a histogram type are pre-registered. The backlight control signal is a control signal for varying the duty ratio of the lamp tube current of the backlight unit 8 according to the low brightness mode and the low contrast mode, the normal mode and the high brightness mode, and the high contrast mode, and the tube current intensity according to each mode. It includes a control signal to do differently. Here, the histogram type is determined as an experimental value for expressing the brightness and contrast optimized for each image quality and is selectively used according to a specific image.

The image quality processor 32 is supplied to the IC master controller 52 that receives data from the memory 36 and the external sensing system 40, and to the image quality processor 32 from the system 35 as shown in FIG. 5. A luminance color separation converter 54 for converting three primary color digital video data signals of 'Ri', 'Gi' and 'Bi' into YUV signals, and 'Ri', 'Gi' and 'Bi' for histogram analysis. MAX (RGB) (56) for calculating the maximum RGB value, window (58) for setting histogram analysis area, gray histogram and analyzing the histogram's pole and mean values The histogram analysis unit 55 for calculating the H, the histogram analyzed by the histogram analyzer 55 and the contrast variable signal supplied from the external sensing system 40 and the brightness information from the luminance color separation unit 54. A lookup table 53 for selecting the histogram type corresponding to the Y signal, The luminance color mixing unit 57 which restores the RGB signal according to the histogram, the pole value and the average value of the histogram, and the backlight control signal of the histogram selected by the lookup table 53 are supplied to the PWM controller, or the DAC A backlight control unit 59 is provided to supply the inverter at a voltage level using a digital analog converter.

The IC master controller 52 initializes the image quality processor 32 as a whole. At this time, the initial histogram stored in the memory 36 is stored in the lookup table 53, and then the image quality processing unit 32 is initialized according to the histogram stored in the lookup table 53. This IC master controller 52 communicates with the exchange 34 and the memory 36 to supply respective data to the lookup table 53.

The luminance color separation unit 54 converts the three primary color digital video data signals 'Ri', 'Gi' and 'Bi' supplied from the system 35 into YUV signals. This conversion is according to the following equations (1), (2) and (3).

Y = 0.229 x Ri + 0.587 x Gi + 0.114 x Bi

U = 0.493 × (Bi-Y)

V = 0.887 × (Ri-Y)

MAX (RGB) 56 calculates the maximum value of three primary color digital video data signals of 'Ri', 'Gi' and 'Bi' supplied from the system 35 for histogram analysis. It is supplied to the unit 55.

Window 58 sets the analysis area of the histogram. In addition, the window 58 is configured for sampling of 'Vsyn1', 'Hsyn1', 'DCLK1' and 'DE1', that is, vertical / horizontal synchronization signals Vsyn1 and Hsyn1 and digital video data supplied from the system 35. 'Vsyn2', 'Hsyn2', 'DCLK2' and the data enable signal DE1 indicating the period during which the dot clock DCLK1 and the digital video data Ri, Gi, and Bi are modulated according to the modulated video signal. Modulate to 'DE2'.

The histogram analyzing unit 55 performs a histogram set from the Y signal supplied from the luminance color separation unit 54, the maximum value of the video signal data signal supplied from the Max (RGB) 56, and the window 58. The histogram is analyzed by combining the gram setting areas. As a result, the gray histogram is calculated and the pole value and the average value of the histogram are supplied to the lookup table 53 and the backlight control unit 59.

The lookup table 53 reads histogram types corresponding to various luminance and contrast from the memory 36 and stores them in a table form. The look-up table 53 is a value calculated by calculating a boundary value of the histogram distribution supplied from the histogram analyzer 55, a contrast variable signal supplied from the external sensing system 40, and a luminance color separation unit 54. A histogram type corresponding to each combination of Y signal values supplied from the same is selected and supplied to the luminance color mixing unit 57. In addition, different backlight control signals are supplied to the backlight controller 59 according to the histogram type stored in the lookup table 53.

The luminance color mixing unit 57 combines the curves supplied from the lookup table 53 and the U and V signals supplied from the luminance color separation unit 54 to generate modulated R0, G0, and B0 signals. Here, the luminance color mixing unit 57 modulates using the following equations (4), (5), (6).

R = YM + (0.000 × U) + (1.140 × V)

G = YM-(0.396 × U)-(0.581 × V)

B = YM + (2.029) × U + (0.000 × V)

The backlight controller 59 adjusts the signal supplied to the PWM controller according to the backlight control signal of the histogram type selected by the pole value and the average value of the histogram of the histogram analyzer 55 and the lookup table. In addition, the backlight control unit 59 adjusts the brightness of the lamp by supplying the voltage level of the DAC to the inverter according to the histogram pole value and the average value and the histogram type selected by the lookup table 53.

As shown in FIG. 6, the lamp driving unit 60 driving the lamp boosts the AC power supplied from the outside to AC, and boosts the AC power of the inverter 66 to supply the lamp 69. A feedback circuit 62 connected between the transformer 68 and the transformer 68 and the lamp 69 to detect current, and connected between the feedback circuit 62 and the inverter 66 to the inverter 66. And a PWM controller 64 for controlling the supplied pulse. Here, the PWM controller 64 adjusts the brightness of the lamp 69 by adjusting the pulse according to the signal from the backlight controller 59.

The backlight unit adjusts contrast by adjusting light according to the signal of the lamp driver 60. The backlight unit includes a lamp for generating light, a lamp housing surrounding the lamp, a light guide plate for scattering light generated from the lamp, a reflector plate disposed on the rear surface of the light guide plate to prevent light leakage, and a light guide plate disposed at the front of the light guide plate. An optical sheet for converting the exit angle is provided.

In the liquid crystal display panel 22, liquid crystal is injected between two glass substrates. The data lines D1 to Dm and the gate lines G1 to Gn formed on the lower glass substrate of the liquid crystal display panel 22 are perpendicular to each other. Thin-Film Transistors (hereinafter referred to as TFTs) formed at the intersections of the data lines D1 to Dm and the gate lines G1 to Gn respond to scan signals from the gate lines G1 to Gn. As a result, the data voltages from the data lines D1 to Dm are supplied to the liquid crystal cell Clc. For this purpose, the gate electrodes of the TFTs are connected to the corresponding gate lines G1 to Gn, and the source electrodes are connected to the corresponding data lines D1 to Dm. The drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc. A black matrix, a color filter, and a common electrode (not shown) are formed on the upper glass substrate of the liquid crystal display panel 22. On the light exit surface of the upper glass substrate and the light incidence surface of the lower glass substrate of the liquid crystal display panel 22, polarizing plates having an optical axis orthogonal to each other are attached, and on each of the liquid crystal facing surface of the lower glass substrate and the liquid crystal facing surface of the upper glass substrate, respectively. An alignment film for setting the pretilt angle of the liquid crystal is formed. In addition, a storage capacitor Cst is formed in each of the liquid crystal cells Clc of the liquid crystal display panel 22. The storage capacitor Cst is formed between the pixel electrode of the liquid crystal cell Clc and the front gate line, or is formed between the pixel electrode of the liquid crystal cell Clc and the common electrode line (not shown) to form a voltage of the liquid crystal cell Clc. It keeps constant.

The panel driver includes a data driver 24 for supplying a data voltage to the data line, a gate driver 26 for sequentially supplying scan pulses to the gate line, and a gamma voltage supply unit for supplying a gamma voltage of the data driver 24 ( 28 and a timing controller 20 for supplying control signals to the data driver 24 and the gate driver 26.

The data driver 24 converts the digital video data Ro, Go, and Bo into analog analog gamma compensation voltages from the gamma voltage supply 28 in response to the control signal DDC from the timing controller 20. The gamma compensation voltage is supplied to the data lines D1 to Dm of the liquid crystal display panel 22 as a data voltage.

The gate driver 26 generates a scan pulse of the gate voltage in response to the control signal GDC from the timing controller 20, and sequentially supplies the scan pulse to the gate lines G1 to Gn to supply a data signal. The horizontal line of the liquid crystal display panel 22 is selected.

The timing controller 20 supplies the digital video data Ro, Go, Bo input from the internal processing system 30 to the data driver 24 and uses the timing control signals Vsync2, Hsync2, DCLK2, and DE2. The control signals DDC and GDC for controlling the gate driver 26 and the data driver 24 are generated. The control signal DDC of the gate driver 26 includes a gate start pulse (GSP), a gate shift clock (GSC), a gate output enable (GOE), and the like. The control signal DDCS of the driver 24 includes a source start pulse (GSP), a source shift clock (SSC), a source output signal (SOC), and a polarity signal (POL). ), And the like.                     

The driving method of the liquid crystal display according to the exemplary embodiment of the present invention having the above structure will be described.

First, in the case of initialization of the liquid crystal display, the internal processing system 30 is supplied with the backlight control signal corresponding to the initial histogram type and the histogram type stored in the memory 36. Specifically, as shown in FIG. 7, the backlight control signal according to the normal histogram type B and the histogram type B is supplied to the IC master controller 52 of the image quality processing unit 32 and the IC master. The controller 52 stores the normal histogram type B and the backlight control signal according to the histogram type B in the look up table 53. Thereafter, the image data Ri, Gi, Bi signals supplied from the system 35 are modulated according to the histogram type stored in the lookup table 53 and supplied to the timing controller 20. Here, the type of histogram stored in the lookup table 53 does not consider the contrast variable signal supplied from the external sensing system 40. That is, the histogram type selected by the look-up table 53 is determined according to the brightness information Y of the image data Ri, Gi, Bi supplied from the system 35 and the image data Ri, Gi, Bi. By histogram analysis.

Next, when the external environment is dark, the sensing unit 44, that is, the optical sensor included in the external sensing system 40 senses the reduced amount of light and supplies it to the determination unit 42. Accordingly, the determination unit 42 generates a contrast variable signal corresponding to the reduced amount of light. The contrast variable signal thus generated is supplied to an exchange 34 of the internal processing system 30. The exchanger 34 supplies the contrast variable signal to the IC master controller 52 of the image quality processing section 32. At this time, the IC master controller 52 selects a histogram type A having a low contrast ratio, that is, a low contrast, among various types of histogram types stored in the memory 36 as shown in FIG. 7. The histogram type A having the low contrast ratio selected in this way is the brightness information Y extracted from the image data Ri, Gi, Bi supplied from the system 35 and the pole value and the average value extracted by the histogram analyzer 55. Is supplied to the lookup table 53. Accordingly, the lookup table 53 selects a histogram type A having a low luminance and contrast ratio and supplies the histogram type A to the luminance color mixing unit 57 and the backlight control unit 59. Here, the backlight control signal corresponding to each histogram type is stored together in the lookup table 53. Thereafter, the luminance color mixing unit 57 generates a modulated RGB signal by combining the selected histogram and the U and V signals from the luminance color separation unit 54. In addition, the backlight controller 59 generates a backlight control signal from the lookup table 53 and a signal corresponding to the pole value and the average value from the histogram analyzer 55 to supply the PWM controller and the inverter. Accordingly, the brightness of the lamp 69 is adjusted to be darker so that the overall contrast is reduced to provide a more sensational image to the user.

Next, when the external environment is bright, the sensing unit 44 included in the external sensing system 40, that is, the optical sensor, senses the increased amount of light and supplies it to the determination unit 42. Accordingly, the determination unit 42 generates a contrast variable signal corresponding to the increased amount of light. The contrast variable signal thus generated is supplied to an exchange 34 of the internal processing system 30. The exchanger 34 supplies the contrast variable signal to the IC master controller 52 of the image quality processing section 32. At this time, the IC master controller 52 selects a histogram type C having a high contrast ratio, that is, a high contrast, among various types of histogram types stored in the memory 36 as shown in FIG. 7. The selected histogram type C having a high contrast ratio includes brightness information Y extracted from the image data Ri, Gi, and Bi supplied from the system 35 and the pole value and the average value extracted by the histogram analyzer 55. Is supplied to the lookup table 53. Accordingly, the lookup table 53 selects the histogram type C having a high contrast ratio and supplies the histogram type C to the luminance color mixing unit 57 and the backlight control unit 59. Here, the backlight control signal corresponding to each histogram type is stored together in the lookup table 53. Thereafter, the luminance color mixing unit 57 generates modulated RO, GO, and BO signals by combining the selected histogram and the U and V signals from the luminance color separation unit 54. In addition, the backlight controller 59 generates a backlight control signal from the lookup table 53 and a signal corresponding to the pole value and the average value from the histogram analyzer 55 to supply the PWM controller and the inverter. Accordingly, the brightness of the lamp 69 is adjusted to be brighter so that the overall contrast is increased to provide a more sensational image to the user.

Herein, the liquid crystal display according to the exemplary embodiment may generate a luminance variable signal according to a change in an external environment, and apply a histogram according to the luminance variable signal. For example, when the external environment is dark, in order to prevent glare of the user, a dark luminance signal is generated and supplied to the image processing unit 32. Accordingly, a histogram type having a low luminance is selected in the lookup table 53. The brightness of the backlight can be reduced by supplying to the luminance color mixing unit 57 and supplying the backlight control signal of the histogram type having low luminance to the backlight control unit 59. Accordingly, by reducing the brightness of the panel according to the external environment, it is possible to provide a more sensational image to the user.

As described above, the liquid crystal display according to the exemplary embodiment of the present invention may provide a more sensational image to the user by adaptively controlling the contrast and luminance of the liquid crystal panel according to the change of the external environment. In more detail, the liquid crystal display according to the exemplary embodiment of the present invention reduces contrast and brightness of the liquid crystal panel in a dark environment to prevent glare of the user and prevent light blurring, thereby recognizing a better image, and a bright environment. In this case, the image quality can be improved by increasing the contrast and luminance of the liquid crystal panel to make the bright part of the image brighter so that the user can recognize the image better.

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 (11)

A memory for storing a plurality of histograms having different data distribution curves corresponding to the amount of light and a plurality of backlight control signals having different control values corresponding to the amount of light; A system for generating image data and control signals; An external sensing system for generating a contrast control signal according to the amount of light in the external environment; An internal processing system for selecting a histogram and a backlight control signal corresponding to the contrast and luminance modulated in response to the image data and the control signal and the variable signal; And a lamp driver for adjusting contrast and brightness of the liquid crystal panel in response to a backlight control signal from the internal processing system. The method of claim 1, The external sensing system A sensing unit having at least one optical sensor for sensing a change in an external environment; And a determination unit which generates a contrast variable signal according to the amount of light detected by the detection unit. The method of claim 1, The internal processing system An exchanger for receiving a variable signal from the external processing system; An image quality processor which receives a signal from the switch and modulates image data and a control signal from the system; And a memory for supplying different histogram types and a backlight control signal according to the histogram types to the image processing unit. The method of claim 3, wherein The image quality processing unit An IC master controller in communication with the memory and the exchange to receive a histogram from the memory and to receive a variable signal from the exchange; A luminance color separator for separating the image data from the system into luminance and color; A maximum value detector for detecting a color signal having a maximum value among the image data from the system; A window for varying a control signal from the system and setting a histogram analysis area; A histogram analyzer for analyzing a histogram using a luminance signal from the luminance color separator and a color signal having a maximum value, a variable signal from an IC master controller, and a histogram in the histogram analysis region set by the window; A look-up table for selecting a histogram and a backlight control signal corresponding to a combination of the histogram analysis unit, the variable signal from the IC master controller, and the luminance signals; A luminance color mixing unit for generating image data by combining the luminance signal of the histogram selected by the lookup table and the color signal separated by the luminance color separation unit; And a backlight control unit for supplying a backlight control signal selected by the lookup table to the lamp driver. The method of claim 4, wherein The lamp driving unit A lamp for generating light; A feedback circuit for detecting a signal flowing through the lamp; An inverter configured to adjust a voltage level in response to a backlight control signal from the backlight controller; A PWM controller connected between the inverter and the feedback circuit and modulating a pulse width by a backlight control signal from the backlight control unit; And a transformer for boosting an AC signal from said inverter and supplying it to a lamp. The method of claim 5, wherein The backlight control signal is And any one of a duty ratio of the tube current and an intensity of the tube current applied to the lamp. A luminance extractor which receives image data and extracts luminance components from the image data; A histogram parameter generator for indicating an attribute of the image data according to the luminance component; An external sensing system for generating a contrast control signal according to the amount of light in the external environment; A memory for storing a plurality of histograms having different data distribution curves corresponding to the amount of light and a plurality of backlight control signals having different control values corresponding to the amount of light; And a selector configured to receive the plurality of histograms and the plurality of other backlight control signals from the memory, and select the histogram and the backlight control signal based on the luminance component, the histogram parameter, and the contrast control signal. A liquid crystal display device. The method of claim 7, wherein The external sensing system A sensing unit having at least one optical sensor for sensing a change in an external environment; And a determination unit which generates a contrast variable signal according to the amount of light detected by the detection unit. A liquid crystal display panel; A first system for generating a contrast control signal in accordance with the amount of light in the external environment; A plurality of histogram type information that selects different contrast characteristics of the image data based on the contrast control signal, and a plurality of control values are set differently according to the histogram type information based on the contrast control signal. A second system for selecting any one of the light source control signals; A panel driver supplying image data modulated with the selected histogram type information to the liquid crystal display panel; And a light source for irradiating the liquid crystal display panel with light whose brightness is controlled by the selected light source control signal. Providing a plurality of histograms having different data distribution curves in response to the amount of light and a plurality of backlight control signals having different control values in correspondence with the amount of light; Generating a contrast control signal according to an external environment; Generating a histogram parameter indicative of a property of the image data according to the input of the image data and the luminance component extracted from the image data; Selecting the histogram and backlight control signal based on the histogram parameter and the contrast control signal; And supplying image data modulated with the selected histogram type information to a liquid crystal display panel displaying an image, and controlling brightness of a light source irradiated to the liquid crystal display panel by the selected backlight control signal. Driving method of liquid crystal display device. The method of claim 10, The step of selecting the histogram and the backlight control signal based on the histogram parameter and the contrast control signal If the external environment is bright, select histogram and backlight control signals with high brightness and contrast. A method of driving a liquid crystal display device, characterized by selecting a histogram and a backlight control signal having low luminance and contrast when the external environment is dark.

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