KR101461033B1 - Driving apparatus for liquid crystal display device and method for driving the same - Google Patents

Abstract

The present invention relates to a driving apparatus for a liquid crystal display apparatus and a driving method thereof, which can improve the visual contrast of an image while reducing the power consumption of a backlight and maintain the brightness of a displayed subtitle at a constant level.

To this end, a liquid crystal display device of the present invention includes: a liquid crystal panel formed with a plurality of pixel regions; A subtracter for subtracting subtitle data from externally input video data, generating a dimming control signal to correspond to the luminance information of the video data, and converting the gradation level of the subtitle data according to the dimming control signal, A conversion processing unit; A timing controller for supplying the converted data to a data driver for driving the liquid crystal panel in accordance with driving of the liquid crystal panel, and controlling the data driver; And a backlight unit for emitting light to the liquid crystal panel according to the dimming control signal.

Backlight unit, dimming control signal, contrast enhancement, subtitle data,

Description

Technical Field [0001] The present invention relates to a driving apparatus for a liquid crystal display,

The present invention relates to a liquid crystal display, and more particularly, to a driving apparatus and a driving method of a liquid crystal display which can improve the visual contrast of an image while reducing the power consumption of a backlight, ≪ / RTI >

2. Description of the Related Art Recently, flat panel display devices that have emerged include a liquid crystal display, a field emission display, a plasma display panel, and a light emitting display.

Of the flat panel display devices, the liquid crystal display devices are excellent in resolution, color display, and image quality, and are actively applied to notebook computers, desktop monitors, and mobile terminals.

Such a liquid crystal display device displays a desired image by adjusting the transmittance of light emitted from the backlight unit according to a video signal. To this end, the liquid crystal display device includes a liquid crystal panel having a plurality of liquid crystal cells for displaying an image, a driving circuit for driving the liquid crystal panel, and a backlight unit for irradiating light to the liquid crystal panel.

 Conventionally, a backlight unit uses a blinking driving technique that causes light of constant brightness to be constantly generated at a constant period regardless of a video signal. In this case, although power consumption of a liquid crystal display device increases, motion blurring ) And ghost phenomenon have occurred.

Accordingly, recently, a technique of controlling the on-off timing of the backlight according to the brightness of the displayed image to reduce the power consumption is also applied. At this time, if the on / off timing of the backlight is controlled without the conversion of the image data, the brightness of the display image is lowered and the feeling of liveliness is reduced. Therefore, the brightness value of the image data must be converted.

However, when the caption is inserted in the display image, since the on-off timing of the backlight can not be controlled, there is a disadvantage that the power consumption reduction effect described above is lost. In other words, when the on-off timing of the backlight is controlled in the case where the caption is inserted, the brightness of the caption is continuously changed according to the brightness of the surrounding image.

Accordingly, since the on / off timing of the backlight can not be controlled when the caption is inserted, the caption of the display image is mostly composed of the maximum brightness data even when the caption is inserted. The effect of reducing the amount of water is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and it is an object of the present invention to provide a driving apparatus for a liquid crystal display device capable of reducing the power consumption of a backlight while improving the visual contrast of a display image, And a driving method thereof.

According to an aspect of the present invention, there is provided an apparatus for driving a liquid crystal display, including: a liquid crystal panel including a plurality of pixel regions; A subtracter for subtracting subtitle data from externally input video data, generating a dimming control signal to correspond to the luminance information of the video data, and converting the gradation level of the subtitle data according to the dimming control signal, A conversion processing unit; A timing controller for controlling the data driver to supply the converted data to a data driver for driving the liquid crystal panel in accordance with driving of the liquid crystal panel; And a backlight unit for emitting light to the liquid crystal panel according to the dimming control signal.

Wherein the image conversion processing unit detects the brightness information from the input image data and generates extension data by expanding a card contrast of the image data according to the detected brightness information, A caption image processor for detecting caption data from the image data and collectively converting the gradation level of the caption data according to the level of the dimming control signal and outputting the result, And an image integration processing unit for combining the data and the subtitle data converted with the gradation level to generate the converted data and supplying the generated converted data to the timing controller.

Wherein the image quality improving unit includes a video modulator that extracts the brightness information from the input video data and generates the extension data so that the contrast of the video data is expanded using the extracted brightness information, And a backlight control section for generating the dimming control signal whose duty ratio is converted so as to correspond to the information, and supplying the generated dimming control signal to the caption image processing section and the backlight unit.

Wherein the caption image processing unit detects the caption data by detecting the position information of the caption by extracting edge information and closed-form information from the image data, and detecting the caption data by at least one frame by using the detected position information, And a subtitle data conversion unit for converting the gradation levels of the subtitle data according to the level of the dimming control signal input from the improvement unit and outputting the converted gradation levels.

Wherein the caption data conversion section detects the level change width of the dimming control signal in units of at least one frame and collectively converts the tone value of the caption data so as to be in inverse proportion to the level change width of the dimming control signal and supplies the tone value to the image integration processing section Feature.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display, including the steps of: extracting caption data from image data; Generating a dimming control signal to correspond to luminance information of the image data; Generating converted data by converting the gradation level of the extracted caption data according to the dimming control signal; Supplying the converted data to a data driver for driving the liquid crystal panel by aligning the converted data according to driving of the liquid crystal panel; And irradiating the liquid crystal panel with light according to the dimming control signal.

Wherein the dimming control signal generating step includes the steps of detecting the brightness information from the input image data, generating extended data by expanding a card contrast of the image data according to the detected brightness information, And generating the dimming control signal so as to correspond to the information.

Wherein the conversion data generation step comprises the steps of: extracting subtitle data in at least one frame unit; collectively converting the gradation level of the subtitle data according to the level of the dimming control signal and outputting the converted data; And generating the converted data by integrating the subtitle data whose level has been converted.

Extracting edge information from the image data, extracting closed-curve information using the edge information, detecting position information of the subtitle, and extracting at least one frame using the detected position information, And detecting the caption data in the unit of the caption data.

The step of converting the caption data includes a step of detecting the level change width of the dimming control signal in at least one frame unit and a step of collectively converting the tone value of the caption data in inverse proportion to the level change width of the dimming control signal .

The driving apparatus and the driving method of the liquid crystal display according to the present invention have the following effects.

First, brightness information of image data input from the outside is analyzed, and the contrast of the display data is enlarged and displayed according to the analyzed brightness information, thereby improving the visual contrast of the display image.

Second, by controlling the on / off timing of the backlight so as to correspond to the luminance information of the image data, it is possible to display a dynamic and dynamic image on the liquid crystal panel while reducing the power consumption of the backlight unit.

Third, the subtitle image is extracted every frame and the gradation level of the extracted subtitle image is inversely proportional to the luminance level of light generated in the backlight, so that the luminance of the subtitle displayed on the liquid crystal panel can be always maintained constant.

Hereinafter, a driving apparatus and a driving method of a liquid crystal display according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a driving apparatus of a liquid crystal display according to an embodiment of the present invention.

The liquid crystal display device shown in FIG. 1 includes a liquid crystal panel 2 formed with a plurality of pixel regions; A data driver 4 for driving a plurality of data lines DL1 to DLm; A gate driver 6 for driving the plurality of gate lines GL1 to GLn; A dimming control signal (Dim) is generated so as to correspond to luminance information of the image data (RGB), and the gradation level of the caption data is converted into the dimming control signal Dim), thereby generating transform data (M_RGB); And supplies the converted data M_RGB to the data driver 4 in accordance with the driving of the liquid crystal panel 2 and generates the gate and data control signals GCS and DCS to control the gate and data drivers 4 and 6 A timing controller 8 for controlling the timing controller 8; And a backlight unit 18 for emitting light to the liquid crystal panel 2 according to the dimming control signal Dim.

The liquid crystal panel 2 includes a thin film transistor (TFT) formed in each pixel region defined by a plurality of gate lines GL1 to GLn and a plurality of data lines DL1 to DLm, and a liquid crystal capacitor (Clc). The liquid crystal capacitor Clc is composed of a pixel electrode connected to the TFT, and a common electrode facing the pixel electrode and the liquid crystal. The TFT supplies a video signal from each of the data lines DL1 to DLm to the pixel electrode in response to a scan pulse from each of the gate lines GL1 to GLn. The liquid crystal capacitor Clc charges the difference voltage between the video signal supplied to the pixel electrode and the common voltage supplied to the common electrode, and adjusts the light transmittance by varying the arrangement of the liquid crystal molecules according to the difference voltage. The storage capacitor Cst is connected in parallel to the liquid crystal capacitor Clc so that the voltage charged in the liquid crystal capacitor Clc is maintained until the next data signal is supplied. The storage capacitor Cst is formed by overlapping the pixel electrode with the previous gate line and the insulating film interposed therebetween. Alternatively, the storage capacitor Cst may be formed by overlapping the pixel electrode with the storage line and the insulating film interposed therebetween.

The data driver 4 receives a data control signal DCS from the timing controller 8, for example, a source start pulse SSP, a source shift clock SSC, a source output enable SOE (Source Output Enable) signal from the timing controller 8 to an analog voltage, that is, a video signal. Specifically, the data driver 4 latches the data (Data) subjected to the gamma conversion through the timing controller 8 in accordance with the SSC, and supplies a scan pulse to each of the gate lines GL1 to GLn in response to the SOE signal And supplies a video signal for one horizontal line to each of the data lines DL1 to DLm for every one horizontal period to be supplied. At this time, the data driver 4 selects a positive or negative gamma voltage having a predetermined level according to the gradation value of the aligned data Data, and outputs the selected gamma voltage to each of the data lines DL1 to DLm Supply.

The gate driver 6 outputs a gate control signal GCS from the timing controller 8, for example, a gate start pulse GSP, a gate shift clock GSC, a gate output enable Sequentially generates a scan pulse in response to a Gate Output Enable (GOE) signal, and sequentially supplies the scan pulse to the gate lines GL1 to GLn. In other words, the gate driver 6 shifts the GSP from the timing controller 8 according to the GSC to sequentially supply a scan pulse, for example, a gate-on voltage to the gate lines GL1 to GLn. Then, the gate-off voltage is supplied during the period when the gate-on voltage is not supplied to the gate lines GL1 to GLn. Here, the gate driver 6 controls the pulse width of the scan pulse in accordance with the GOE signal.

The image conversion processing unit 10 detects luminance information or gradation information of the image data (RGB) input from the outside, for example, a graphics system (not shown) to generate a histogram. Then, the generated histogram is analyzed and the contrast of the input image data (RGB) is expanded to correspond to the analyzed result. The image conversion processing unit 10 extracts the caption data from the input image data RGB and generates a dimming control signal (Dim) corresponding to the detected brightness information or gradation information. Then, the extracted subtitle data is converted according to the dimming control signal (Dim), and the transformed data (M_RGB) is generated by integrating the expanded and contrasted subtitle data with the converted subtitle data. Hereinafter, the image conversion processing unit 10 will be described in more detail with reference to the accompanying drawings.

The timing controller 8 arranges the converted data (M_RGB) input from the image conversion processing section 10 so as to be suitable for driving the liquid crystal panel 2 and supplies the data to the data driver 4. [ The timing controller 8 receives at least one of the synchronizing signals input through the image conversion processing unit 10, that is, the dot clock DCLK, the data enable signal DE, and the horizontal and vertical synchronizing signals Hsync and Vsync To control the gate and data drivers 6 and 4 by generating gate and data control signals GCS and DCS and supplying them to the gate and data drivers 6 and 4, respectively.

The backlight unit 18 includes a backlight 12 having a plurality of light sources for generating light in the liquid crystal panel 2 and an optical unit for improving the efficiency of light incident from the respective light sources, An inverter control unit 14 for generating a pulse width modulation (PWM) signal in accordance with the control signal Dim, and an AC drive signal ADS for driving the light sources in response to the PWM signal And an inverter 16 for supplying the light to the light sources.

As the light source of the backlight 12, cylindrical lamps such as CCFL (Cold Cathode Fluorescent Lamp) and EEFL (External Electrode Fluorescent Lamp) are mainly used. The lamps generate light by the AC drive signal ADS from the inverter 16. The backlight 12 generates light by simultaneously or sequentially turning on / off the plurality of lamps according to the AC driving signal ADS. In addition, the optical unit diffuses and condenses the incident light from the light source to improve the light efficiency.

The inverter control unit 14 generates a PWM signal corresponding to the duty ratio of the dimming control signal (Dim) input from the image conversion processing unit (10) and supplies it to the inverter (16). Here, the PWM signal is a signal in which the on / off period of the ramp, for example, the high / low period is varied according to the duty ratio information of the dimming control signal Dim.

The inverter 16 generates an AC drive signal ADS for driving the plurality of lamps. At this time, the AC drive signal ADS is supplied or cut off according to the PWM signal from the inverter control unit 14, Off mode (Burst Mode).

FIG. 2 is a configuration diagram specifically showing the image conversion processing unit shown in FIG. 1. FIG.

The image conversion processing unit 10 shown in FIG. 2 detects luminance information from externally input image data (RGB) and expands the business card contrast of the input image data (RGB) according to the detected luminance information to generate expanded data C_RGB (20) for generating a dimming control signal (Dim) so as to correspond to the detected luminance information, a controller (20) for detecting the caption data (TI) from the image data (RGB) A subtitle image processor 40 for collectively converting the gradation level of the subtitle data TI according to the dimming control signal Dim from the subtitle decoder 20 and outputting the converted gradation level, And an image integration processing unit 50 for generating the conversion data M_RGB by integrating the caption data D_TI and supplying the generated conversion data M_RGB to the timing controller 8. [

The image quality improving unit 20 extracts luminance information from the image data RGB and converts the gradation level of the image data RGB so that the contrast of the image data RGB is expanded according to the extracted luminance information. The picture quality improvement unit 20 generates a dimming control signal Dim so as to correspond to the detected luminance information, and supplies the dimming control signal Dim to the caption image processing unit 40 and the inverter control unit 14, respectively.

3, the image quality improving unit 20 extracts luminance information from the image data RGB and extracts extended data C_RGB so that the contrast of the image data RGB is expanded using the extracted luminance information And a dimming control signal (Dim) whose duty ratio is converted so as to correspond to the extracted luminance information and supplies the dimming control signal (Dim) to the caption image processing unit (40) and the backlight unit (18) And a control unit 30.

The video modulator 50 extracts the luminance component Y from the image data RGB and generates the extended data C_RGB so that the contrast of the image data RGB is expanded by using the extracted luminance component Y do. The image modulator 50 includes a luminance / color separation unit 21, a delay unit 22, a luminance / color mixing unit 23, a histogram analysis unit 25, a histogram modulation unit 26, a memory 27 and a look-up table 28 as shown in Fig.

The luminance / color separation unit 21 separates the image data RGB into a luminance component Y and a chrominance component U and V. The luminance / Here, each of the luminance component (Y) and the chrominance components (U, V) is obtained by Equations (1) to (3).

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

U = 0.493 x (Bi-Y)

V = 0.887 x (Ri-Y)

The histogram analyzing unit 25 divides the luminance component Y into gradations on a frame basis. In other words, the histogram analyzer 25 arranges the luminance components Y in units of frames so as to correspond to the respective gradations, and obtains a histogram as shown in FIG. At this time, by analyzing the histogram, brightness information of the image, that is, brightness information and the like can be grasped. For example, if the histogram is shifted to the right (high grayscale), a bright screen is determined, and if the histogram is shifted to the left (low grayscale), a dark screen is determined. On the other hand, the histogram analyzing unit 25 analyzes the histogram indicating the luminance component Y of one frame, and grasps the luminance information (the minimum value, the maximum value, the average value, the mode value, etc.) of the current frame. In addition, the histogram analyzer 25 supplies the backlight control unit 30 with the control signal CS corresponding to the detected brightness information.

The histogram modulating unit 26 receives the luminance information and the histogram from the histogram analyzing unit 25 and generates a modulated luminance component YM by enlarging the contrast of the inputted histogram. At this time, the histogram modulating unit 26 refers to the reference modulation data stored in the look-up table 28 to generate the modulated luminance component YM.

The lookup table 28 stores various reference modulation data corresponding to luminance information. In other words, the lookup table 28 stores various types of reference modulated data so that the contrast can be extended corresponding to predetermined luminance information. For example, when the histogram is input to the histogram modulating unit 26 as shown in FIG. 4, the histogram modulating unit 26 refers to the reference modulating data stored in the lookup table 28, (YM). At this time, the gradation of the modulated luminance component YM is expanded and distributed in the entire area. As described above, when the luminance component YM is expanded and distributed over the entire area, the contrast of dark luminance and bright luminance can be conspicuous. Meanwhile, the reference modulation data stored in the look-up table 28 is experimentally determined so that the contrast can be extended corresponding to various histograms. The actual lookup table 28 is stored in the memory 27. In the present invention, the memory 27 and the lookup table 28 are shown separately to clearly show the lookup table 28.)

The delay unit 22 delays the chrominance components U and V while the luminance component Y is analyzed in the histogram analysis unit 25 and the histogram modulation unit 26. The delay unit 22 supplies the chrominance components UD and VD synchronized with the modulated luminance component YM and delayed to the luminance / color mixing unit 23.

The luminance / color mixing unit 23 generates the extended data C_RGB using the modulated luminance component YM and the delayed chrominance components UD and VD. Here, the extended data (C_RGB) is obtained by Equations (4) to (6).

C_R = Y + 0.000 x U + 1.140 x V

C_G = Y - 0.396 x U - 0.581 x V

C_B = Y + 2.029 x U + 0.000 x V

The operation of the image modulator 50 will be described in detail. First, the luminance / color separator 21 converts the image data RGB into luminance components Y and chrominance components (U, V). Here, the luminance component Y is input to the histogram analyzer 25 and the chrominance components U and V are input to the delay unit 22.

The histogram analyzing unit 25 that receives the luminance component Y divides the luminance component Y into gradations on a frame basis and extracts luminance information from the divided luminance components Y based on luminance information (minimum value, maximum value, average value, Etc.). Thereafter, the histogram analyzer 25 generates a control signal CS so that light can be generated from the backlight unit 18 in proportion to the luminance information, and outputs the generated control signal CS to the backlight controller 30 ). Then, the histogram analyzing unit 25 supplies the luminance information and the histogram information to the histogram modulating unit 26. [

The histogram modulating section 26 refers to the lookup table 28 and expands the contrast of the histogram inputted to the histogram modulating section 26. [ In other words, the histogram modulating section 26 generates a modulated luminance component YM in which the histogram is extended so that the histogram is distributed in the entire gradation region, and supplies the modulated luminance component YM to the luminance / color mixing section 23.

The luminance / color mixing unit 23 receiving the delayed chrominance components UD and VD and the modulated luminance component YM generates the extended data C_RGB using equations (4) to (6). At this time, the extended data (C_RGB) is generated by the modulated luminance component (YM), so that it has a distinct brightness. That is, according to the present invention, the modulated luminance component YM can be distributed in the entire gradation range to generate extended data (C_RGB) having a clear contrast, and accordingly, a biased image can be displayed on the liquid crystal panel 2 have. In other words, the bright color becomes brighter, the darker color becomes darker, and the contrast is enhanced, and the power consumption of the backlight 12 can be reduced.

The backlight control unit 30 generates the dimming control signal Dim so as to correspond to the control signal CS supplied from the histogram analyzing unit 30 and supplies the generated dimming control signal Dim to the inverter control unit 14 do. The dimming control signal Dim is a digital control signal that allows light to be generated in the backlight 12 so as to be proportional to the luminance information analyzed by the histogram analyzer 25. [ In other words, if the brightness information analyzed by the histogram analyzer 25 has a high level, a high-level digital control signal, that is, a dimming control signal (Dim) is generated so that light of high luminance can be generated. And generates a low level dimming control signal Dim so that low brightness light can be generated if the luminance information analyzed in the unit 25 has a low luminance level. Accordingly, the backlight control unit 30 of the present invention controls the light of the backlight 12 so that the bright color is displayed more brightly and the dark color is displayed more darkly so that an image having a sharp contrast can be displayed on the liquid crystal panel 2 To be displayed.

The caption image processing unit 40 of FIG. 2 extracts edge information and closed-curve information from the image data (RGB), detects the position information of the caption, and outputs the caption data (TI) in at least one frame unit using the detected position information. And a subtitle data detector 41 for detecting the subtitle data TI in accordance with the gradation level of the subtitle data TI in inverse proportion to the level change width of the dimming control signal Dim sequentially input from the image quality improving section 20, And a data conversion unit 42.

The caption data detector 41 detects the position information of the area where the caption is displayed from the input image data RGB as shown in FIG. To this end, the caption data detector 41 detects edge information using a Sobel operator (Edge Detection). Here, the Sobel operator is a typical first derivative slope operator, and is mainly used for detecting an edge of an image or smoothly converting an image. In order to detect the position of the caption, a connected component method, a texture classification method, and the like, which are generally known in addition to the above-described edge information detection, may be used. Normally, the caption of an image is made up of a similar gradation level or a luminance level, and is set to have a gradation or a luminance level of a large difference from the surrounding image. Since most of such subtitles are displayed at a certain position of the horizontal lower portion or the vertical side portion of the display image, it is desirable to detect the edge information mainly on the region where the subtitles are mainly displayed in the image data (RGB).

When the edge information is detected, the caption data detector 41 performs a morphological closing method to obtain the inclination of the detected edge information to form a closed curve between the edge information. Here, the morphological crossing method is a method of forming a closed curve by connecting edge information to at least one line according to the inclination of an edge. Since the images displayed on the image display device do not form a closed curve except for the letters, information of positions where many closed lines are formed can be the position information of the subtitles. However, in order to more reliably detect the position information of the caption, it is possible to check the position of the caption by filling the inside of the closed curves with the same gradation data by performing a morphological opening method, The position can be clearly set as the position information of the caption. Here, the morphological opening is a method of equally filling the inside of the closed curve with one gray level by converting the gradation levels in the closed curve to each other by converting them to the largest or smallest level of gradation.

Thus, the caption data detector 41 obtains edge information of the image data (RGB), connects it with a closed curve, and then fills the inside of the closed curve with the same gradation to check the position of the caption. The caption data detector 41 stores the recognized position information and sequentially detects the caption data TI on the basis of, for example, at least one frame in the input image data RGB.

At the time of detecting the subsequent caption data TI, the first extracted caption data TI is used as a mask or the caption data TI is detected in an area corresponding to the position information of the stored caption. Here, the caption data TI detected through the above process may be subjected to a predetermined filtering process to clearly correct the outline thereof. When the subtitle data TI thus detected is displayed as an image, it can be displayed as shown in FIG.

The caption data converter 42 receives the caption data TI from the caption data detector 41 at least every one frame. Then, the gradation levels of the subtitle data TI are converted so as to be inversely proportional to the level change width of the dimming control signal Dim sequentially input from the image quality improving section 20. [ Specifically, the caption data converter 42 detects the level change width of the dimming control signal (Dim) input from the image quality improvement unit (20) in units of at least one frame and adjusts the level change width of the dimming control signal The gradation value of the subtitle data TI is converted in a batch manner.

As described above, the dimming control signal Dim is a digital signal for controlling the on / off timing of the lamps provided in the backlight 12, and represents the ON / OFF timing of the lamps, that is, the duty ratio. The luminance BL_Y of the light generated in the backlight 12 varies in units of at least one frame according to the level of the dimming control signal Dim. Thus, the subtitle data converter 42 detects the level change width of the dimming control signal (Dim) supplied in units of at least one frame in units of at least one frame and outputs the dimming control signal (Dim) The tone value of the subtitle data TI is converted in a batch manner in inverse proportion to the level change width of the subtitle data TI. Specifically, as the level of the dimming control signal Dim increases, the on-time of the lamp also becomes longer, so that the luminance BL_Y of the backlight 12 also increases. At this time, since the subtitle data converter 42 lowers the tone value of the caption data D_TI in inverse proportion to the level variation width of the dimming control signal Dim, the luminance D_TI_Y of the caption image is lowered. On the other hand, when the level of the dimming control signal Dim is lowered, the ON time of the lamp is shortened, so that the brightness BL_Y of the backlight 12 is also lowered. The subtitle data converter 42 increases the tone value of the subtitle data D_TI so as to be in inverse proportion to the level variation width of the dimming control signal Dim so as to increase the luminance D_TI_Y of the subtitle image. Since the brightness D_TI_Y of the caption image and the brightness BL_Y of the light generated in the backlight 12 maintain inversely proportional relation to each other, the caption brightness (text_Y) of the image displayed on the liquid crystal panel 2 is always constant .

As described above, the driving apparatus of the liquid crystal display and the driving method thereof according to the embodiment of the present invention analyze the luminance information (Y) of the input image data (RGB) Since the contrast of the image data (RGB) is expanded and displayed, the visual contrast of the display image can be improved. In addition, by controlling the light luminance of the backlight 12 so as to correspond to the luminance information Y of the image data (RGB), a lively and dynamic image can be displayed on the liquid crystal panel 2. [ In the present invention, the caption image is extracted at least one frame unit, and the gradation level of the extracted caption image is converted and outputted in inverse proportion to the brightness (BL_Y) level change width of the light generated in the backlight 12, 2 can always be kept constant.

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. 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.

1 is a configuration diagram showing a driving apparatus of a liquid crystal display according to an embodiment of the present invention;

FIG. 2 is a configuration diagram specifically showing the image conversion processing unit shown in FIG. 1. FIG.

FIG. 3 is a block diagram specifically showing the image quality improving unit shown in FIG. 2. FIG.

4 is a diagram illustrating an operation process of the histogram analyzing unit shown in FIG.

5 is a diagram illustrating an operation process of the histogram modulating unit shown in FIG.

FIG. 6 is an input image showing an operation process of the caption data detecting unit shown in FIG. 2;

FIG. 7 is a caption extracting image showing an operation process of the caption data converting unit shown in FIG. 2. FIG.

FIG. 8 is a graph for explaining the operation of the subtitle data conversion unit shown in FIG. 2; FIG.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.

2: liquid crystal panel 4: data driver

6: Gate driver 8: Timing controller

10: image conversion processing unit 12: backlight

14: inverter control unit 16: inverter

18: backlight unit 20: image quality improvement unit

30: backlight control unit 40: caption image processing unit

41: caption data detection unit 42: caption data conversion unit

Claims (10)

A liquid crystal panel formed with a plurality of pixel regions; A subtracter for subtracting subtitle data from externally input video data, generating a dimming control signal to correspond to the luminance information of the video data, and converting the gradation level of the subtitle data according to the dimming control signal, A conversion processing unit; A timing controller for controlling the data driver to supply the converted data to a data driver for driving the liquid crystal panel in accordance with driving of the liquid crystal panel; And And a backlight unit for emitting light to the liquid crystal panel in accordance with the dimming control signal; The image conversion processing unit The method includes detecting brightness information from the input image data, expanding a card contrast of the image data according to the detected brightness information, generating expanded data, and generating the dimming control signal to correspond to the detected brightness information An image quality improvement unit; A caption image processing unit for detecting caption data from the image data and converting the gradation level of the caption data according to a level of the dimming control signal and outputting the converted gradation level; And And an image integration processing unit for combining the expanded data and the subtitle data converted with the gradation level to generate the converted data and supplying the generated converted data to the timing controller. . delete The method according to claim 1, The image quality improvement unit An image modulator for extracting the brightness information from the input image data and generating the extension data so that the contrast of the image data is expanded using the extracted brightness information; And And a backlight control unit for generating the dimming control signal whose duty ratio is converted so as to correspond to the extracted brightness information, and supplying the generated dimming control signal to the caption image processing unit and the backlight unit. The method of claim 3, The caption image processing unit A caption data detector for detecting the position information of the caption by extracting the edge information and the closed information from the image data and detecting the caption data by at least one frame by using the detected position information; And And a caption data converter for converting the gradation levels of the caption data according to the level of the dimming control signal input from the image quality improvement unit and outputting the converted gradation levels. 5. The method of claim 4, The subtitle data conversion unit Wherein the control unit detects the level change width of the dimming control signal in units of frames at a time and collectively converts the tone value of the caption data so as to be in inverse proportion to the level change width of the dimming control signal and supplies it to the image integration processing unit Device for driving a device. Extracting subtitle data from the video data; Detecting brightness information from the image data, expanding a card contrast of the image data according to the detected brightness information to generate expanded data, and generating a dimming control signal to correspond to the detected brightness information; Converting the gradation level of the extracted caption data according to the level of the dimming control signal; Generating converted data by combining the extension data and the subtitle data converted with the gradation level; Supplying the converted data to a data driver for driving the liquid crystal panel by aligning the converted data according to driving of the liquid crystal panel; And And irradiating the liquid crystal panel with light according to the dimming control signal. delete delete The method according to claim 6, The caption data extraction step Extracting edge information from the image data; Extracting closed-curve information using the edge information and detecting position information of a caption; And And detecting the caption data on at least one frame basis using the detected position information. 10. The method of claim 9, The subtitle data conversion step Detecting a level variation width of the dimming control signal in at least one frame unit; And And collectively converting tone values of the caption data so as to be in inverse proportion to the level variation width of the dimming control signal.

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