KR20100075046A - Driving apparatus for liquid crystal display device and method for driving the same - Google Patents

Abstract

PURPOSE: A driving apparatus for a liquid crystal display device and a method for driving the same are provided to improve the production yield of LED by compensating a color coordinate dissemination problem in LED used in a backlight unit. CONSTITUTION: A liquid crystal panel(2) comprises a plurality of pixel regions. A gate driver(6) and a data driver(4) drive a plurality of gates and data line. The liquid crystal panel comprises the gate driver and the data driver. A memory unit(10) stores and outputs compensation data. A timing controller(8) generates conversion image data. A timing controller generates a dimming control signal, a gate control signal, and a data control signal. A backlight unit(12) applies light to the liquid crystal panel according to the dimming control signal.

Description

DRIVING APPARATUS FOR LIQUID CRYSTAL DISPLAY DEVICE AND METHOD FOR DRIVING THE SAME

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and in particular, to compensate for the problem of color coordinate scattering of LEDs used in a backlight unit on data, thereby improving the process yield of the LEDs and reducing the manufacturing cost of the backlight unit. It relates to a driving device and a driving method thereof.

As the information society develops, the demand for image display devices is increasing in various forms. Recently, liquid crystal displays, field emission displays, plasma display panels, Various flat panel displays, such as a light emitting display, are utilized.

Among these, the liquid crystal display device displays a desired image by controlling the transmission amount of light supplied from the back light unit by the liquid crystal panel having a plurality of liquid crystal cells arranged in a matrix form.

Conventionally, fluorescent lamps are mainly used as a light source of a backlight unit, but in recent years, light emitting diodes (LEDs) that are advantageous in terms of power consumption, weight, and brightness are used instead of fluorescent lamps according to the trend of miniaturization, thinning, and weight reduction of the backlight unit. A backlight unit using a diode is used.

As such, when the above-mentioned LEDs are used as the light source in the backlight unit, white LEDs are mainly used. However, the white LEDs have a low process yield, resulting in an increase in the cost of the backlight unit.

Specifically, the white LEDs used in the backlight unit implement white light by molding a yellow phosphor on a blue LED chip. Accordingly, due to the difference in the main wavelength dispersion of the blue LED chip and the content of the yellow phosphor, the white LEDs have a wider spread of white light even though the high brightness LEDs realize the same white light.

Conventionally, in order to prevent a decrease in white reproducibility and luminance uniformity caused by the color coordinate scattering problem of the white light as described above, full color coordinate inspection of the white LEDs was performed. However, when the white LEDs are determined by performing color coordinate inspection, the yield of the white LEDs is lowered and the manufacturing cost of the backlight unit is increased because many LEDs that do not meet the reference value cannot be used as a defect determination.

The present invention is to solve the above problems, the liquid crystal display to improve the process yield of the LEDs and to reduce the manufacturing cost of the backlight unit by compensating the color coordinate distribution problem of the LEDs used in the backlight unit on the data It is an object of the present invention to provide a driving device and a driving method thereof.

In order to achieve the above object, a driving apparatus of a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel having a plurality of pixel regions; A gate and data driver for driving a plurality of gates and data lines provided in the liquid crystal panel; A memory unit for storing and outputting compensation data corresponding to the LED information of the backlight input from the user; Converts the image data input from the outside according to the compensation data from the memory unit to generate the converted image data, supply it to the data driver, and generate a gate and data control signal together with a dimming control signal to generate the gate and data driver. A timing controller controlling the; And a backlight unit including the backlight and irradiating light to the liquid crystal panel according to the dimming control signal.

The memory unit stores each of the LED information corresponding to the distribution degree of the white LEDs used in the backlight and the compensation data corresponding to the respective LED information, and any one LED information selected from the user is inputted. If it is characterized in that for supplying the red, green and blue compensation data corresponding to the input LED information to the timing controller.

The timing controller may include an image data alignment unit for aligning the image data to be suitable for driving the liquid crystal panel using at least one signal from an external synchronization signal, and a gray value of the image data aligned from the image data alignment unit. Compensating and converting the data according to the compensation data supplied from the memory unit to generate the converted image data, and supply the converted image data to the data driver using the at least one signal of the synchronization signal and the data control signal. And a control signal generator for generating the gate control signal and the dimming control signal and then supplying the data, the gate driver, and the backlight unit, respectively.

The image data compensation unit adds or subtracts or multiplies the compensation value of the compensation data by the gray value of each sub-pixel of the aligned image data input in units of horizontal periods, thereby multiplying the gray value of each sub-pixel of the aligned image data. And converts the converted image data sequentially into the data driver every horizontal period.

The backlight unit may be configured to generate a pulse width modulation signal according to a dimming control signal from the timing controller and the backlight including the plurality of white LEDs generating light and an optical unit for improving efficiency of light incident from the plurality of white LEDs. And a backlight controller configured to generate an AC driving signal for driving the plurality of white LEDs according to the generated pulse width modulation signal and to control the white LEDs of the backlight.

In addition, a method of driving a liquid crystal display according to an exemplary embodiment of the present invention for achieving the above object includes a liquid crystal panel having a plurality of pixel regions, a gate, a data driver, and a timing controller for driving the liquid crystal panel. A method of driving a liquid crystal display, the method comprising: storing and outputting compensation data corresponding to LED information of a backlight input from a user using at least one memory unit; Converting the image data input from the outside according to the compensation data to generate the converted image data and supplying the converted image data to the data driver, and generating a gate and data control signal together with a dimming control signal to control the gate and data driver. ; And irradiating light to the liquid crystal panel according to the dimming control signal using the backlight.

The storing and outputting of the compensation data may include storing respective LED information corresponding to a distribution degree of the white LEDs used in the backlight and the compensation data corresponding to the respective LED information, and selecting the user. And outputting compensation data of red, green, and blue corresponding to the inputted LED information when any one of the LED information is input.

The generating of the converted image data, the gate, the data, and the dimming control signal may include arranging the image data to be suitable for driving the liquid crystal panel using at least one signal from an external synchronization signal. Generating the converted image data by compensating the gray level values of the image data arranged from the memory unit according to the compensation data supplied from the memory unit, and supplying the converted image data to the data driver and at least one of the synchronization signals. And generating the data control signal, the gate control signal, and the dimming control signal and supplying the data control signal, the gate control signal, and the dimming control signal to the data, gate driver, and backlight unit, respectively.

The generating of the converted image data may include adding or subtracting or multiplying a compensation value of the compensation data by a gray value of each sub pixel of the aligned image data input in units of horizontal periods, and then gray level of each sub pixel of the aligned image data. And converting the value and sequentially supplying the converted image data to the data driver every horizontal period.

The irradiating light onto the liquid crystal panel may include irradiating light onto the liquid crystal panel and the dimming control by including a plurality of white LEDs generating light and an optical unit for improving the efficiency of light incident from the plurality of white LEDs. Generating a pulse width modulated signal according to the signal and generating an AC driving signal for driving the plurality of white LEDs according to the generated pulse width modulated signal to control the white LEDs of the backlight; .

The driving apparatus and driving method thereof of the liquid crystal display according to the exemplary embodiment of the present invention having the above characteristics improve the process yield of the LEDs by compensating the color coordinate scattering problem of the LEDs used in the backlight unit on the data and back light unit. Reduce manufacturing costs.

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

1 is a configuration diagram illustrating a driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

The liquid crystal display shown in FIG. 1 includes a liquid crystal panel 2 formed with a plurality of pixel regions; A data driver 4 for driving the plurality of data lines DL1 to DLm; A gate driver 6 driving a plurality of gate lines GL1 to GLn; A memory unit 10 for storing and outputting compensation data M_RGB corresponding to the LED information Offset of the backlight input from the user; The converted image data Data is generated by converting the image data RGB inputted from the outside according to the compensation data M_RGB from the memory unit 10, supplying them to the data driver 4, and dimming them. A timing controller 8 for generating the control signal Dim and the gate and data control signals GCS and DCS to control the gate and data drivers 4 and 6; And a backlight unit 12 including the backlight and radiates 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) and a liquid crystal capacitor connected to a TFT formed in each pixel area defined by the plurality of gate lines GL1 to GLn and the plurality of data lines DL1 to DLm. (Clc). The liquid crystal capacitor Clc is composed of a pixel electrode connected to a TFT, and a common electrode facing each other with the pixel electrode and the liquid crystal interposed therebetween. The TFT supplies the image signals from the respective data lines DL1 to DLm to the pixel electrodes in response to the scan pulses from the respective gate lines GL1 to GLn. The liquid crystal capacitor Clc charges the difference voltage between the image 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 liquid crystal molecules according to the difference voltage. The storage capacitor Cst is connected to the liquid crystal capacitor Clc in parallel 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 layer interposed therebetween. In contrast, the storage capacitor Cst is formed by overlapping the pixel electrode with the storage line and the insulating layer interposed therebetween.

The data driver 4 includes a data control signal DCS from the timing controller 8, for example, a source start pulse (SSP), a source shift clock (SSC), and a source output enable (SCS). The data converted by compensation from the timing controller 8 is converted into an analog voltage, that is, an image signal, using a source output enable (SOE) signal or the like. Specifically, the data driver 4 latches the converted image data Data that is compensated and gamma-converted and aligned through the timing controller 8 according to the SSC, and then, in response to the SOE signal, each gate line GL1 to GLn. An image signal for one horizontal line is supplied to each of the data lines DL1 to DLm every horizontal period in which a scan pulse is supplied to the data. At this time, the data driver 4 selects a positive or negative gamma voltage having a predetermined level according to the gray value of the compensated-converted image data Data and uses the selected gamma voltage as an image signal for each data line DL1 to DLm. Supplies).

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

The memory unit 10 stores the LED information Offset according to the distribution degree of the white LEDs of the backlight 14 and the compensation data M_RGB corresponding to the respective LED information Offset. When any one of the LED information Offset selected by the user is input, red, green, and blue compensation data M_RGB corresponding to the input LED information Offset is supplied to the timing controller 8. The memory unit 10 may include at least one look-up table or the like, and may use any area of the memory provided in the timing board or the like.

The timing controller 8 aligns the image data RGB input from the outside to be suitable for driving the liquid crystal panel 2, and compensates the gradation value of the aligned image data from the memory unit 10. By converting according to the conversion, the converted video data Data having the gray level value converted therein is generated. The generated converted image data Data is supplied to the data driver 4.

In addition, the timing controller 8 controls the gate and the data by using at least one of a synchronization signal input from an external device, that is, a dot clock DCLK, a data enable signal DE, and horizontal and vertical synchronization signals Hsync and Vsync. The gate and data drivers 6 and 4 are controlled by generating signals GCS and DCS and supplying them to the gate and data drivers 6 and 4, respectively. In addition, the timing controller 8 generates a dimming control signal Dim by using at least one of the synchronization signals according to the converted image data Data in which the gray scale value is converted, and transmits the dimming control signal Dim to the backlight unit 12. The backlight unit 12 is controlled by supplying. The timing controller 8 and the above-described memory configuration and driving methods thereof will be described in more detail with reference to the accompanying drawings.

The backlight unit 12 includes a plurality of white LEDs generating light in the liquid crystal panel 2, a backlight 14 having an optical unit for improving the efficiency of light incident from the plurality of white LEDs, and a timing controller 8. Generates a pulse width modulation (PWM) signal according to the dimming control signal (Dim) from the control panel, and generates an AC driving signal (ADS) for driving the plurality of white LEDs according to the generated PWM signal. A backlight control unit 16 is provided to control white LEDs of the backlight.

The backlight 14 generates light by turning on / off a plurality of white LEDs simultaneously or sequentially according to the AC driving signal ADS. In addition, the optical unit improves the light efficiency by diffusing and condensing the incident light from the light source.

Here, the white LEDs of the backlight 14 are composed of a blue LED chip that generates light, a yellow phosphor, and a lens covering the white LED, thereby implementing white light through the blue LED chip and the phosphor. Specifically, the plurality of white LEDs are composed of a blue light emitted by a blue LED chip and a Yttrium Aluminum Garnet (YAG) series, a Terbium Aluminum Garnet (TAG) series, or a silicate (silicate) series emitted by blue light. Yellow light emitted from the yellow phosphor is combined to emit white light.

Therefore, due to the difference in the main wavelength distribution of the blue LED chip and the content of the yellow phosphor in the manufacturing process of the white LEDs, as shown in the CIE color coordinate of FIG. Wide spread of light Therefore, in the present invention, the LED information (Offset) is grasped so as to correspond to the degree of dispersion of the white LEDs of the backlight 14 formed in each liquid crystal display.

For example, as shown in the CIE color coordinates of FIG. 2, when the degree of dispersion of the white LEDs used in the backlight 14 corresponds to a reference value, the P0 level signal is set to the LED information (Offset). . If one of the other backlights 14 uses white LEDs whose scattering degree is less than one level, the P-1 level signal is set to LED information (Offset). In addition, in the case of using the white LEDs in which the dispersion degree exceeds the reference value by two levels in another backlight 14, the signal of the P2 level is set as the LED information (Offset). As described above, according to the present invention, each LED information (Offset) corresponding to the scattering degree of the white LEDs used in each backlight 14 is set, and the set LED information (Offset) is stored in the memory unit 10. It will be input in advance.

On the other hand, the backlight controller 16 included in the backlight unit 12 generates a PWM signal to correspond to the duty ratio of the dimming control signal Dim input from the timing controller 8. In addition, the backlight controller 16 operates in a burst mode for turning on / off the white LEDs by supplying or blocking the AC driving signal ADS to the backlight 14 according to the generated PWM signal. Here, the PWM signal is a signal in which the on / off period of the lamp, for example, the high / low period is variable according to the duty ratio information of the dimming control signal Dim.

FIG. 3 is a detailed block diagram illustrating the memory unit and the timing controller illustrated in FIG. 1. 4 is a diagram illustrating LED information and compensation data corresponding thereto stored in the memory of FIG. 3.

As shown in FIG. 4, the memory unit 10 illustrated in FIG. 3 stores red, green, and blue compensation data M_RGB corresponding to LED information offsets set by a user. Here, the red, green, and blue compensation data M_RGB may be a value that is added to, or multiplied with, the external image data RGB, that is, the gray, red, green, and blue gray values.

For example, when the red, green, and blue values multiplied by the gray, green, and blue grayscale values are set to the compensation data M_RGB, the compensation value corresponding to the LED information (Offset) input as the P0 signal is Can be 1. In addition, the red compensation value M_R corresponding to the LED information Offset input as the P1 signal may be 0.9, the green compensation value M_G may be 0.9, and the blue compensation value M_B may be 1. In addition, the red compensation value M_R corresponding to the LED information Offset input as the P-2 signal may be 0.9, the green compensation value M_G may be 0.8, and the blue compensation value M_B may be 0.9.

The timing controller 8 illustrated in FIG. 3 uses the at least one signal from the external synchronization signals DCLK, DE, Hsync, and Vsync to adjust the image data RGB to be suitable for driving the liquid crystal panel 2. The image data aligning unit 24 to be aligned and the gradation value of the image data C_RGB arranged by the image data aligning unit are compensated and converted according to the compensation data M_RGB from the memory unit 10 to convert the converted image data Data. The data control signal DCS and the gate control signal GCS using the image data compensator 22 for generating and supplying the same to the data driver and at least one of the synchronization signals DCLK, DE, Hsync, and Vsync. And a control signal generator 26 for generating a dimming control signal Dim and then supplying the data and the gate drivers 4 and 6 and the backlight unit 12, respectively.

The image data alignment unit 24 receives at least one of the synchronization signals DCLK, Hsync, Vsync, and DE together with image data RGB from the outside. The input image data RGB is aligned according to the size and resolution of the liquid crystal panel 2 by using the supplied at least one synchronization signal DCLK, Hsync, Vsync, or DE. The aligned image data C_RGB is sequentially supplied to the image data compensator 22 every horizontal period.

The image data compensator 22 compensates and converts the grayscale values of the image data C_RGB arranged by the image data arranging unit 24 according to the compensation data M_RGB from the memory unit 10, thereby converting the converted image data Data. Is generated and supplied to the data driver 4. In detail, the image data compensator 22 subtracts or multiplies the compensation value of the compensation data M_RGB to the gray level value of each sub-pixel of the aligned image data C_RGB input in units of horizontal periods, or performs a multiplication operation. The gray level of each sub pixel of the sorted image data C_RGB is converted. The converted image data Data generated in this way is sequentially supplied to the data driver 4 in units of horizontal periods.

The control signal generator 26 includes a data control signal generator (not shown) and uses an SSP, SSC, and POL signal by using at least one of synchronization signals DCLK, DE, Hsync, and Vsync input from the outside. Create The generated SSP, SSC, and POL signals are supplied to the data driver 4. The data control signal DCS is a signal for controlling the driving timing of the data driver 4, and the POL signal is a signal for converting the polarity of the video signal supplied to each of the data lines DL1 to DLm.

In addition, the control signal generator 26 includes a gate control signal generator (not shown) and generates a GSP, GSC, GOE signal, etc. using at least one of the input synchronization signals DCLK, DE, Hsync, and Vsync. Create The generated GSP, GSC, and GOE signals are supplied to the gate driver 6. The gate control signal GCS is a signal for controlling the driving timing of the gate driver 6.

In addition, the control signal generator 26 includes a dimming control signal generator, which is not shown, from at least one of the input synchronization signals DCLK, DE, Hsync, and Vsync and the image data compensator 22. The dimming control signal Dim is generated using the converted image data Data. Here, the dimming control signal Dim is a signal for controlling the driving timing of the white LEDs included in the backlight 14 and is determined by an average or maximum gray value of the converted image data Data corresponding to at least one frame. The duty ratio is converted. As such, the driving timing of the white LEDs may be converted in units of at least one frame by the dimming control signal Dim in which the duty ratio is converted. To this end, the control signal generator 26 may separately receive or share the converted image data Data from the image data compensator 22.

As described above, the driving device and the driving method of the liquid crystal display according to the exemplary embodiment of the present invention are supplied with LED information corresponding to the color coordinate distribution of the white LEDs used in each backlight unit. The image data RGB input from the outside is converted using the compensation data M_RGB corresponding to the supplied LED information Offset.

As such, the present invention can improve the utilization rates of the LEDs by compensating the problems caused by the color coordinate distribution of the white LEDs on the image data. Therefore, since LEDs are not wasted, it is possible to improve the process yield of LEDs, thereby reducing the manufacturing cost of the backlight unit.

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. Will be clear to those who have knowledge of.

1 is a block diagram illustrating a driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a CIE color coordinate illustrating the distribution of luminance characteristics of LEDs generating white light.

FIG. 3 is a diagram illustrating in detail the memory unit and the timing controller shown in FIG. 1; FIG.

4 is a view showing LED information stored in a memory unit of FIG. 3 and corresponding compensation data;

* Brief description of symbols for the main parts of the drawings.

2: liquid crystal panel 4: data driver

6: gate driver 8: timing controller

10 memory unit 12 backlight unit

14: backlight 16: backlight control

22: image data compensation unit 24: image data alignment unit

26: control signal generator

Claims (10)

A liquid crystal panel formed with a plurality of pixel regions; A gate and data driver for driving a plurality of gates and data lines provided in the liquid crystal panel; A memory unit for storing and outputting compensation data corresponding to the LED information of the backlight input from the user; Converts the image data input from the outside according to the compensation data from the memory unit to generate the converted image data, supply it to the data driver, and generate a gate and data control signal together with a dimming control signal to generate the gate and data driver. A timing controller controlling the; And And a backlight unit which includes the backlight and irradiates light to the liquid crystal panel according to the dimming control signal. The method of claim 1, The memory unit Storing respective LED information corresponding to the degree of distribution of the white LEDs used for the backlight and the compensation data corresponding to the respective LED information; And when the LED information selected by the user is input, red, green, and blue compensation data corresponding to the input LED information is supplied to the timing controller. The method of claim 2, The timing controller is An image data alignment unit for aligning the image data to be suitable for driving the liquid crystal panel using at least one signal from an external synchronization signal; An image data compensator for compensating and converting the gray level values of the image data arranged by the image data arranging unit according to the compensation data supplied from the memory unit to generate the converted image data and supply the converted image data to the data driver; A control signal generator configured to generate the data control signal, the gate control signal, and the dimming control signal using at least one of the synchronization signals, and then supply the data control signal, the gate control signal, and the dimming control signal to the data, gate driver, and the backlight unit, respectively. A drive device for a liquid crystal display device, characterized in that. The method of claim 3, wherein The image data compensator The gray level value of each sub pixel of the sorted image data is converted or subtracted by adding or subtracting or multiplying the compensation value of the compensation data by the gray level value of each sub pixel of the aligned image data input every horizontal period, and converting the converted value. And an image data is sequentially supplied to the data driver every horizontal period. The method of claim 3, wherein The backlight unit is The backlight having the plurality of white LEDs generating light and an optical unit for improving the efficiency of light incident from the plurality of white LEDs, and Generating a pulse width modulated signal according to the dimming control signal from the timing controller and generating an AC driving signal for driving the plurality of white LEDs according to the generated pulse width modulated signal to control the white LEDs of the backlight; A drive device for a liquid crystal display device comprising a backlight control unit. A driving method of a liquid crystal display device comprising a liquid crystal panel formed with a plurality of pixel regions, a gate, a data driver, and a timing controller for driving the liquid crystal panel, Storing and outputting compensation data corresponding to the LED information of the backlight input from the user using at least one memory unit; Converting the image data input from the outside according to the compensation data to generate the converted image data and supply the converted image data to the data driver, and generate the gate and data control signals together with the dimming control signal to control the gate and the data driver. step; And And irradiating light to the liquid crystal panel according to the dimming control signal by using the backlight. The method of claim 6, The storing and outputting of the compensation data Storing respective LED information corresponding to a degree of distribution of the white LEDs used for the backlight and the compensation data corresponding to the respective LED information; and And outputting compensation data of red, green, and blue corresponding to the inputted LED information when any one of the LED information selected by the user is input. The method of claim 7, wherein The conversion image data and the gate, data and dimming control signal generation step Aligning the image data to be suitable for driving the liquid crystal panel using at least one signal from an external synchronization signal; Generating the converted image data by compensating the gray level values of the image data arranged by the image data alignment unit according to the compensation data supplied from the memory unit, and supplying the converted image data to the data driver; and And generating the data control signal, the gate control signal, and the dimming control signal using at least one of the synchronization signals, and supplying the data control signal, the gate control signal, and the dimming control signal to the data, the gate driver, and the backlight unit, respectively. Method of driving a liquid crystal display device. The method of claim 8, The converted image data generating step Converting the gradation value for each sub-pixel of the aligned image data by adding or subtracting or multiplying the compensation value of the compensation data by the gradation value for each sub-pixel of the aligned image data input every horizontal period; and And sequentially supplying the converted image data to the data driver every horizontal period. The method of claim 8, Irradiating light to the liquid crystal panel Irradiating the liquid crystal panel with light having a plurality of white LEDs for generating light and an optical unit for improving the efficiency of light incident from the plurality of white LEDs, and Generating a pulse width modulated signal according to the dimming control signal and generating an AC driving signal for driving the plurality of white LEDs according to the generated pulse width modulated signal to control the white LEDs of the backlight; A method of driving a liquid crystal display device.

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