KR101354367B1 - Liquid crystal display device and method driving of the same - Google Patents

Abstract

A liquid crystal display device capable of improving image quality is disclosed.

According to an exemplary embodiment of the present invention, an LCD includes: an input unit for inputting data into a liquid crystal panel; and a data voltage to be input to the pixels on the liquid crystal panel by one line in response to the data from the input unit and using a gamma voltage set. The gamma voltage set is changed by varying a voltage level range of the gamma voltage set that varies a compensation ratio of data to be emphasized and compensated according to a distribution amount of grayscale values of data included in data from a data driver and the input unit and ambient illumination. And an environment-adaptive gamma voltage generator for supplying the data driver.

Gamma Compensation, Luminance, Environment

Description

[0001] The present invention relates to a liquid crystal display device and a driving method thereof,

1A-1C are characteristic diagrams illustrating gamma error characteristics.

2 is a view showing a liquid crystal display device according to the present invention.

3 is a view illustrating in detail the environment-adaptive gamma voltage generator of FIG.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

102: liquid crystal panel 104: gate driver

106: Data driver 108: Timing controller

110: frame delay unit 112: environment adaptive gamma voltage generator

114: mobile luminance detector 116: luminance detector

118: transmitter 120: receiver

122: optical sensor 124: analog-to-digital converter

126: tone distribution analyzer 128: correction coefficient determiner

130: programmable gamma voltage generator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof capable of improving image quality by generating an optimum gamma voltage in consideration of a surrounding environment.

Recently, a liquid crystal display device using an active matrix liquid crystal panel as a display screen has been widely used. The liquid crystal panel included in the liquid crystal display device displays an image by adjusting the amount of planar light passing through the liquid crystal layer from the rear in pixel units.

In the liquid crystal panel, the amount of light passing through the liquid crystal cell (that is, the luminance of the liquid crystal panel) according to the voltage level of the pixel driving signal (i.e., the gradation value of the video data) supplied to the liquid crystal cells arranged in a matrix form is shown in FIG. 1A. It should change linearly, such as LLC, but in practice it will change non-linearly low, such as ULC of FIG. Thus, in the liquid crystal panel, a gamma error occurs, which is an all-optical conversion error that appears when an electrical signal is converted into an optical signal.

To correct this gamma error, it is assumed that the liquid crystal display has gamma error characteristics such as UDL1 to UDL3 of FIG. 1B for video data. The LCD uniformly corrects all grayscale values that video data may have in a form in which nonlinear gamma correction characteristics corresponding to the gamma error characteristics UDL1 to UDL3 are selectively applied based on the linear gamma characteristic ULD. do. Since all of the gray scale values that video data can have are gamma-corrected uniformly according to the nonlinear gamma correction characteristic, image degradation occurs in an area of a lower gray scale that becomes larger as the brightness of the image to be displayed becomes darker. In order to improve the deterioration of the image in such a lower gray scale region, the gamma error characteristic of the S-shape is assumed based on the gamma characteristic (SDL) of the linear characteristic, assuming the gamma error characteristic of the S-shape as shown in UDL4 of FIG. 1C. A method of highlighting-correcting video data of a lower gray level region of the video data has been applied according to a gamma correction characteristic corresponding to. Even if gamma correction is performed in this way, the image quality felt by the user differs depending on the surrounding conditions such as the luminance perceived by the user according to the illuminance and the distance of the user around the liquid crystal display.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device and a driving method thereof capable of displaying an image having an optimum gamma characteristic in response to surrounding conditions.

It is another object of the present invention to provide a liquid crystal display device capable of improving image quality and a driving method thereof.

According to an exemplary embodiment of the present invention, an LCD includes: an input unit for inputting data into a liquid crystal panel; and a data voltage to input to pixels on the liquid crystal panel in response to data from the input unit and using a gamma voltage set. The voltage level range of the gamma voltage set differs from the data driver for supplying each line by the line and the compensation rate of the data to be emphasized compensated according to the distribution amount of the grayscale values of the data included in the data from the input unit and the ambient illuminance. And an environment-adaptive gamma voltage generator for supplying the gamma voltage set to the data driver.

According to an aspect of the present invention, there is provided a driving method of a liquid crystal display device including a liquid crystal panel and a data driver for supplying data voltages to be input to pixels on the liquid crystal panel by one line. The method may include: inputting data into the liquid crystal panel, calculating a distribution amount of grayscale values of data included in the input data, and a compensation rate of data to be emphasized and compensated according to a distribution amount of the grayscale values of the data and ambient illuminance; Generating a gamma voltage set different from the above, supplying the gamma voltage set to the data driver, applying the gamma voltage set to the input data, and converting the gamma voltage set to a data voltage; and an image corresponding to the data voltage. It is characterized by including the step of displaying.

Hereinafter, embodiments according to the present invention will be described with reference to the accompanying drawings.

2 is a view showing a liquid crystal display device according to the present invention.

As shown in FIG. 2, the liquid crystal display according to the present invention includes a liquid crystal panel 102 in which an image is displayed and a gate driver 104 connected to a plurality of gate lines GL1 to GLn on the liquid crystal panel 102. ) And a data driver 106 connected to a plurality of data lines DL1 to DLm on the liquid crystal panel 102, a timing controller 108 that controls the gate and data drivers 104 and 106, and an external system. And a frame delay unit 110 for delaying the supplied data for one frame.

The plurality of gate lines GL1 to GLn and the plurality of data lines DL1 to DLm are formed on the liquid crystal panel 102 so as to cross each other so that the plurality of pixel areas are separated. Each of the plurality of pixel regions includes a thin film transistor TFT that switches a pixel driving signal to be supplied to a corresponding liquid crystal cell Clc from a corresponding data line DL in response to a scan signal on a corresponding gate line GL. Is formed. The liquid crystal cell Clc adjusts the amount of light that passes through the pixel region according to the voltage level of the pixel driving signal so that an image can be displayed. As a result, a pixel including one thin film transistor TFT and one liquid crystal cell Clc is formed in each pixel area.

The gate driver 104 enables the plurality of gate lines GL1 to GLn for one frame sequentially and exclusively for a predetermined period (that is, for each period of one horizontal synchronization signal). To this end, the gate driver 104 generates a plurality of scan signals exclusively having enable pulses that are sequentially shifted for each period of the horizontal synchronization signal. The gate enable pulse included in each of the plurality of scan signals has a width corresponding to a period of the horizontal synchronization signal. The gate enable pulse included in each of the plurality of scan signals is generated once every frame period.

Whenever one of the plurality of gate lines GL1 to GLn is enabled, the data driver 106 corresponds to the number of data lines DL1 to DLm corresponding to one pixel driving signal. That is, the pixel driving signals corresponding to the number of pixels arranged in one gate line are generated. Each pixel driving signal for one line is supplied to a corresponding pixel (ie, a liquid crystal cell) on the liquid crystal panel 102 via a corresponding data line DL. Each of the pixels arranged on one of the gate lines GL passes an amount of light corresponding to a voltage level of the pixel driving signal. In order to generate pixel driving signals for one line, the data driver 106 sequentially inputs one line of pixel data for each period of one horizontal synchronization signal, and sequentially inputs one line of pixel data for the environment. The gamma voltage set from the adaptive gamma voltage generator 112 is used to simultaneously convert the pixel driving signal in analog form.

The timing controller 108 is a data clock DCLK, a horizontal synchronization signal Hsync, a vertical synchronization signal from an external system (for example, a graphic module of a computer system or an image demodulation module of a television reception system), which is not shown. The gate control signals GCS, the data control signals DCS, and the polarity inversion signal POL are generated using the Vsync and data enable DE signals. The gate control signals GCS are supplied to the gate driver 104 and the data control signals DCS and polarity reversal signals POL are supplied to the data driver 106. In addition, the pixel data for the frame rearranged by the timing controller 108 is sequentially supplied to the data driver 106 one line at a time.

The environment-adaptive gamma voltage generator 112 uses data from an external system (for example, an image signal demodulator of a television receiver module or a graphics card of a computer system) in consideration of an environment in which the liquid crystal display device is located. An optimal gamma voltage is generated and supplied to the data driver 106. The environment-adaptive gamma voltage generator 112 may vary the size and compensation rate of data to be emphasized and compensated according to how much gray level values of data supplied from an external system are distributed around which gray level. The gamma voltage generated by the environment-adaptive gamma voltage generator 112 is supplied to the data driver 106. A detailed description of the environmentally adaptive gamma voltage generator 112 will be described later with reference to FIG. 3.

In addition, the liquid crystal display according to the exemplary embodiment of the present invention may further include a frame delay unit 110 that delays data supplied from an external system for one frame. The frame delay unit 110 delays the time from which data from an external system is supplied toward the data driver 106 by the time for generating the gamma voltage in the environment-adaptive gamma voltage generator 112. The period delayed by the frame delay unit 110 corresponds to a period of one vertical synchronization signal (that is, one frame period).

3 is a view illustrating in detail an environment-adaptive gamma voltage generator of FIG. 2.

As shown in FIG. 2 and FIG. 3, the environment-adaptive gamma voltage generator 112 includes a gray scale distribution analyzer 126 that analyzes a histogram of the data using data supplied from an external system, and a user. The mobile luminance sensor 114, which is carried by the user and detects the luminance perceived by the user at the user's location, the optical sensor 122 that detects external light, and the luminance sensed by the movable luminance detector 114 and the The correction coefficient determination unit 128 and the correction coefficient determination unit 128 determine the compensation ratio of the gamma voltage using the external light sensed by the optical sensor 122 and the histogram analyzed by the gray scale distribution analyzer 126. The programmable gamma voltage generator 130 generates a gamma voltage according to the compensation rate determined by the controller.

The movable luminance detector 114 may include a luminance detector 116 for detecting a luminance perceived by a user, and a receiver in the environment-adaptive gamma voltage generator 112 for the luminance detected by the luminance detector 116. And a transmitter 118 for supplying to 120. The mobile luminance detector 114 is carried by the user and senses the luminance perceived by the user according to the distance at which the user is located and supplies it to the transmitter 118. The luminance detector 114 may detect, for example, a luminance perceived by the user according to a distance at which the user is located by using an image photographing apparatus such as a CCD.

The luminance sensed by the luminance detector 114 is supplied to the transmitter 118. The transmitter 118 converts the sensed luminance into digital and supplies it to the receiver 120 in the environment-adaptive gamma voltage generator 112. The transmitter 118 converts the luminance sensed by the luminance detector 116 into a digital data form and supplies the converted luminance data to the receiver 120. The transmitter 118 may include an analog-to-digital converter for converting the luminance sensed by the luminance detector 116 into a digital form.

The receiver 120 receives the luminance data from the transmitter 118 and supplies the received luminance data to the correction coefficient determiner 128.

The optical sensor 122 senses external light. In this case, the optical sensor 122 may be a photo diode, an illuminometer, a photo transistor, and the like. The optical sensor 122 senses the luminance of the external light and supplies the sensed luminance value to the analog-digital converter 124. The analog-digital converter 124 converts the luminance value detected by the optical sensor 122 into a digital form and supplies the converted external light luminance data to the correction relay determiner 128.

The gradation distribution analyzer 126 analyzes a histogram of pixel data of one frame and detects how much the pixel data is distributed in which gradation level region. In other words, the gradation distribution analyzer 126 detects a distribution gradation region and a distribution amount of pixel data of one frame through histometry.

The correction coefficient determiner 128 applies the luminance data supplied from the receiver 120 to the distribution gradation region and the distribution amount of the pixel data from the gradation distribution analyzer 126 of the gradation region of the pixel data to be emphasized and compensated. The gamma characteristics of magnitude and emphasis compensation are calculated. In addition, the correction coefficient determiner 128 determines a correction coefficient having a logic value for designating a gamma voltage set corresponding to the calculated gamma characteristic.

The correction coefficient determiner 128 converts the external light luminance data supplied from the optical sensor 122 and the analog-to-digital converter 124 into the distribution gradation region and the distribution amount of the pixel data from the gradation distribution analyzer 126. The gamma characteristics of the gray scale region of the pixel data to be emphasized compensated and the highlight compensation ratio are calculated. In addition, the correction coefficient determiner 128 determines a correction coefficient having a logic value for designating a gamma voltage set corresponding to the calculated gamma characteristic.

The correction coefficient determiner 128 provides luminance data supplied from the receiver 120 and external light supplied from the optical sensor 122 to the distribution gray area and the distribution amount of the pixel data from the gray distribution analyzer 126. The luminance data is applied to calculate the size of the gradation region of the pixel data to be emphasized and the gamma characteristics of the enhancement compensation ratio. In addition, the correction coefficient determiner 128 determines a correction coefficient having a logic value for designating a gamma voltage set corresponding to the calculated gamma characteristic.

The programmable gamma voltage generator 130 responsive to the correction coefficient determined by the correction coefficient determiner 128 generates a gamma voltage set corresponding to a logic value of the correction coefficient among the plurality of gamma voltage sets. The programmable gamma voltage generator 130 may include a gamma voltage data set read from the lookup table and a gamma voltage data set read from the lookup table, in which a set of gamma voltage data corresponding to the number of logic values that a correction coefficient may have is input. And a digital-to-analog converter for converting to a voltage set.

The gamma voltage set generated by the programmable gamma voltage generator 130 has a gamma characteristic of an area having a size corresponding to the gray level distribution of pixel data and an emphasis compensation ratio according to the distribution of pixel data. The gamma voltage set generated by the programmable gamma voltage generator 130 is supplied to the data driver 106 shown in FIG. 1.

As described above, the environment-adaptive gamma voltage generator 112 generates an optimum gamma voltage considering the surrounding environment by sensing luminance data recognized by the user and light supplied from the outside at a distance away from the liquid crystal display device. do. As the environment-adaptive gamma voltage generator 112 generates an optimal gamma voltage considering the surrounding environment, the image quality may be improved by displaying an image on the liquid crystal panel using the gamma voltage.

As described above, the liquid crystal display according to the present invention may be capable of displaying an image having an optimum gamma characteristic according to a surrounding situation by using brightness perceived by a user and luminance data of externally generated light.

In addition, the liquid crystal display according to the present invention can improve image quality.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the following claims. .

Claims (13)

An input unit for inputting data into the liquid crystal panel; A data driver responsive to data from the input unit and supplying a data voltage to be input to pixels on the liquid crystal panel by one line using a gamma voltage set; And The gamma voltage set is transferred to the data driver by varying a voltage level range of the gamma voltage set that makes a compensation rate of data to be emphasized compensated according to a distribution amount of grayscale values of data included in the data from the input unit and ambient illumination. Includes; environmentally adaptive gamma voltage generator for supplying, The environmentally adaptive gamma voltage generator, A gradation distribution analyzer for detecting a distribution gradation region and a distribution map in which one frame of data is distributed; An optical sensor for sensing a luminance of light supplied from the outside; A mobile luminance sensor configured to sense luminance perceived by the user at a user's location; A gamma characteristic of the magnitude and emphasis compensation ratio of the data to be compensated for compensation using the distribution gray area and the distribution detected by the gray distribution analyzer and the external light luminance data detected by the optical sensor and the brightness detected by the movable luminance detector A correction coefficient determiner for determining a; And And a programmable gamma voltage generator configured to generate a gamma voltage set corresponding to the gamma characteristic determined by the correction coefficient determiner and to supply the gamma voltage set to the data driver. delete delete delete delete The method according to claim 1, Wherein the optical sensor comprises any one of a photodiode, a phototransistor, and an illuminometer. The method according to claim 1, And an analog-to-digital converter for converting the external light brightness sensed by the optical sensor into digital. The method according to claim 1, And the environment-adaptive gamma voltage generator further includes a receiver configured to receive luminance data recognized by the user from the movable luminance detector. A driving method of a liquid crystal display device comprising a liquid crystal panel and a data driver for supplying data voltages to be input to pixels on the liquid crystal panel by one line. Inputting data into the liquid crystal panel; Calculating a distribution amount of grayscale values of data included in the input data by a grayscale distribution analyzer; Generating a gamma voltage set that makes a compensation rate of data to be emphasized compensated according to the distribution amount of the grayscale values of the data and ambient illumination; Supplying the gamma voltage set to the data driver and converting the gamma voltage set to a data voltage by applying the gamma voltage set to the input data; And Displaying an image corresponding to the data voltage; Generating the gamma voltage set, Sensing the brightness of light supplied from the outside through an optical sensor; Detecting a luminance perceived by the user at the user's position in the movable luminance detector; The size of the data to be emphasized and compensated using the distribution gray scale region and the distribution gray scale detected by the gray scale distribution analyzer in the correction coefficient determiner and the external light luminance data sensed by the optical sensor and the luminance sensed by the movable luminance sensor; Determining a gamma characteristic of the stress compensation factor; And And generating a gamma voltage set corresponding to the gamma characteristic determined by the correction coefficient determiner from the programmable gamma voltage generator and supplying the gamma voltage set to the data driver. delete delete delete The method according to claim 1, The liquid crystal display device, And a frame delay unit for delaying data provided from the input unit to the data driver for one frame.

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