KR20020061908A - Driving Method For Reducing Contour Noise Between Frames of Plasma Display Panel and Multi Path Driving Apparatus Using the same - Google Patents

Abstract

PURPOSE: A method for driving a plasma display panel(PDP) to reduce a moving picture pseudo contour noise between frames and an apparatus for driving multi path using the same are provided, which removes the moving picture pseudo contour noise and also can improve a display quality. CONSTITUTION: The multi path driving apparatus of the PDP comprises a next screen data path to process picture data of the next screen, and a frame memory(50) to store inputted picture data of one frame. A present screen data main path maps an input picture signal of the present screen to sub fields where gray levels are expressed in detail. A present screen data sub path maps the input picture signal of the present screen to sub fields corresponding to an MPD(Moving Picture Distortion) free code. And an MPD judgement part(60) selects picture data supplied from the present screen data main path and the present screen data sub path by judging the moving picture distortion between an interface region of the input picture signal and the screen.

Description

Driving Method and Reducing Contour Noise Between Frames of Plasma Display Panel Plasma Display Panel and Multi Path Driving Apparatus Using the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for driving a plasma display panel, and more particularly, to a method and a multi-pass driving apparatus for a plasma display panel which removes inter-frame video pseudo contour noise and improves display quality.

Plasma Display Panel (hereinafter referred to as "PDP") displays an image including text or graphics by emitting phosphors by 147 nm ultraviolet rays generated during discharge of He + Xe or Ne + Xe inert mixed gas. . Such a PDP is not only thin and easy to enlarge, but also greatly improved in quality due to recent technology development. In particular, the three-electrode AC surface discharge type PDP has advantages of low voltage driving and long life because wall charges are accumulated on the surface during discharge and protect the electrodes from sputtering caused by the discharge.

Referring to FIG. 1, a discharge cell of a three-electrode AC surface discharge type PDP is formed on a scan / sustain electrode 30Y and a common sustain electrode 30Z formed on an upper substrate 10, and a lower substrate 18. An address electrode 20X is provided. Each of the scan / sustain electrode 30Y and the common sustain electrode 30Z has a line width smaller than the line widths of the transparent electrodes 12Y and 12Z and the transparent electrodes 12Y and 12Z, and is formed on one edge of the transparent electrode. (13Y, 13Z). The transparent electrodes 12Y and 12Z are usually formed on the upper substrate 10 by indium tin oxide (ITO). The metal bus electrodes 13Y and 13Z are usually formed of metals such as chromium (Cr) and formed on the transparent electrodes 12Y and 12Z to reduce voltage drop caused by the transparent electrodes 12Y and 12Z having high resistance. The upper dielectric layer 14 and the passivation layer 16 are stacked on the upper substrate 10 formed parallel to the scan / sustain electrode 30Y and the common sustain electrode 30Z. In the upper dielectric layer 14, wall charges generated during plasma discharge are accumulated. The protective layer 16 prevents damage to the upper dielectric layer 14 due to sputtering generated during plasma discharge and increases emission efficiency of secondary electrons. As the protective film 16, magnesium oxide (MgO) is usually used. The lower dielectric layer 22 and the partition wall 24 are formed on the lower substrate 18 on which the address electrode 20X is formed, and the phosphor layer 26 is coated on the surfaces of the lower dielectric layer 22 and the partition wall 24. The address electrode 20X is formed in the direction crossing the scan / sustain electrode 30Y and the common sustain electrode 30Z. The partition wall 24 is formed in parallel with the address electrode 20X to prevent ultraviolet rays and visible light generated by the discharge from leaking to the adjacent discharge cells. The phosphor layer 26 is excited by ultraviolet rays generated during plasma discharge to generate visible light of any one of red, green, and blue. An inert mixed gas such as He + Xe or Ne + Xe for discharging is injected into the discharge space of the discharge cells provided between the upper and lower substrates 10 and 18 and the partition wall 24.

The PDP is driven by dividing one frame into several subfields having different number of emission times in order to realize gray level of an image. Each subfield is further divided into a reset period for uniformly generating discharge, an address period for selecting a discharge cell, and a sustain period for implementing gray levels according to the number of discharges. For example, when the image is to be displayed with 256 gray levels, the frame period (16.67 ms) corresponding to 1/60 second is divided into eight subfields. In addition, each of the eight subfields is divided into an address period and a sustain period. Here, the reset period and the address period of each subfield are the same for each subfield, while the sustain period is 2 ⁿ (n = 0,1,2,3,4,5,6,7) in each subfield. Is increased. As described above, since the sustain period is changed in each subfield, gray levels of an image can be realized.

FIG. 2 schematically shows a driving device of the PDP shown in FIG. 1.

Referring to FIG. 2, the PDP driving apparatus includes an inverse gamma correction unit 32 to which an image signal is input, an error diffusion unit 34 and a subfield connected in series between the inverse gamma correction unit 32 and the PDP 42. And a waveform generator 40 for inputting a synchronization signal Sync and generating a driving waveform of the PDP 42. The inverse gamma correction unit 32 performs a reverse gamma correction on the gamma corrected video signal to linearly convert luminance values according to grayscale values of the video signal. The error diffusion unit 34 finely adjusts luminance values between adjacent cells in the unit pixel area. The subfield mapping unit 36 separates the data from the error diffusion unit 34 bit by bit and allocates bit data corresponding to the subfield according to the luminance relative ratio. The data aligning unit 38 converts the image data input from the subfield mapping unit 36 in accordance with the resolution format of the PDP 42 to convert the address data into an integrated circuit (IC) hereinafter. To serve). The waveform generator 40 generates a driving waveform for discharging the cells of the PDP 42 in the reset period, the address period, and the sustain period, and supplies the waveform to the PDP 42.

In the PDP, contour noise may be generated in a moving image due to a characteristic of realizing the gray level of an image by a combination of subfields. If pseudo contour noise occurs, pseudo contour appears on the screen, and thus the display quality is deteriorated. For example, as shown in FIGS. 3 and 4, the left half of the screen is displayed with 127 gradation values and the right half of the screen is displayed with 128 gradation values, and then the screen is moved to the right. Since the emitted light is viewed simultaneously with the naked eye, peak white, or white band, appears at the boundary between the gray scale values 127 and 128. On the contrary, when the left half of the screen is displayed with a gradation value of 128 and the right half of the screen is displayed with a gradation value of 127, the screen is moved to the right. A black belt will appear.

Such video pseudo contour noise may be generated in subfields within one frame, and may also be generated between frames if a large number of emission or gray level difference occurs between the frames.

As a method for removing the pseudo pseudo contour noise, a subfield is divided into one or two subfields, a subfield is rearranged, a subfield is added, and the subfields are ordered. The rearrangement method and error diffusion method have been proposed. However, adding subfields causes insufficient sustain periods, making it difficult to increase the resolution and complicate the circuit configuration. Recently, in order to remove video pseudo contour noise, a code in which subfields having a low luminance relative ratio are sequentially turned on in a subfield having a low luminance relative ratio has been proposed to correspond to the gray scale value as shown in FIG. 5. . Such a code is called a "Moving Picture Distortion Free Code" (hereinafter referred to as "MPD precode"), which can be seen in FIG. The gray level value of each subfield is determined such that the emission of light increases linearly in the time axis and the time axis, but MPD precode has a disadvantage in that the expressible gray value is limited to the number of subfields. The MPD precode equal to 5 corresponds to the luminance relative ratios 1, 2, 4, 8, 16, 24, 32, 40, 56, 72 of each subfield, and its gray level value is 0, 1, 3, 7, 15, 31, 55, 87, 183, and 255. For this reason, when an image is displayed using the MPD precode, the image cannot be represented in detail.

Accordingly, an object of the present invention is to provide a driving method of a PDP and a multi-pass driving device using the same to remove video pseudo contour noise and improve display quality.

1 is a perspective view showing a discharge cell structure of a conventional three-electrode AC surface discharge type plasma display panel.

FIG. 2 is a block diagram schematically illustrating a driving device of the plasma display panel shown in FIG. 1.

FIG. 3 is a view for explaining video pseudo contour noise appearing in the plasma display panel shown in FIG. 1. FIG.

FIG. 4 is a diagram illustrating subfields set to fine grayscale values at which a pseudo pseudo contour noise as shown in FIG. 3 is generated.

FIG. 5 is a diagram illustrating subfields set to grayscale values corresponding to an MPD precode for removing video pseudo-contour noise as shown in FIG. 3; FIG.

FIG. 6 is a diagram for explaining that video pseudo contour noise is removed by subfields as shown in FIG. 5; FIG.

7 is a block diagram illustrating a multi-pass driving apparatus of a plasma display panel according to an exemplary embodiment of the present invention.

FIG. 8 is a block diagram illustrating in detail the MPD determining unit illustrated in FIG. 7.

<Description of Symbols for Main Parts of Drawings>

10: upper substrate 12Y, 12Z: transparent electrode

13Y, 13Z: metal bus electrode 14, 22: dielectric layer

16: protective film 18: lower substrate

20X: address electrode 24: partition wall

26: phosphor 30Y: scan / sustain electrode

30Z: common sustain electrode 32, 52A, 52B, 52C: reverse gamma correction unit

34,54A, 54B, 54C: Error diffusion unit 36,56A, 56B, 56C: Subfield mapping unit

38,62: data alignment unit 40: waveform generator

42: PDP 50: frame memory

58A to 58I: line memory 60: MPD discrimination unit

64: calculator 66: MUX controller

68: multiplexer

In order to achieve the above objects, the multi-pass driving method of the PDP according to the present invention comprises the steps of mapping the image data of the current screen to the sub-fields in which the gray scale value is represented fine; Mapping image data of the current screen to subfields without video distortion; Mapping image data of a next screen, which is input subsequent to the current screen, to subfields; Selecting one of the subfield data in which the gray scale value is expressed finely on the current screen and the subfield data without the video distortion, according to the video distortion value between the current screen and the next screen.

According to an aspect of the present invention, there is provided a multipath driving apparatus for a PDP, comprising: a memory connected to an input line and storing image data of a current screen; A current screen main path for mapping image data from the memory to subfields in which gray level values are expressed finely; A current picture subpath for mapping image data from the memory to subfields without moving picture distortion; A next screen path for mapping image data of a next screen inputted from an input line to subfields; And selecting means for selecting any one of subfield data in which gray level values are minutely expressed on the current screen and subfield data without video distortion in accordance with the video distortion value between the current screen and the next screen.

Other objects and features of the present invention in addition to the objects will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 7 and 8.

Referring to FIG. 7, the apparatus for driving a multipath of a PDP according to the present invention includes a next screen data path for processing image data of a next screen, a frame memory 50 for storing one frame of input image data; The current screen data main path for mapping the input video signal of the current screen to subfields in which grayscale values are expressed, and the current screen for mapping the input video signal of the current screen to subfields corresponding to the MPD precode. MPD determining unit 60 for determining whether the data subpath, the boundary region of the input video signal and the video distortion between the screen, and selecting the video data supplied from the current screen data main path and the current screen data subpath according to the result. It is provided.

The next screen data path includes the third inverse gamma correction unit 52C, the third error diffusion unit 54C, the third subfield mapping unit 56C, and the seventh to the third lines connected between the input line and the MPD determination unit 60. Ninth line memories 58G, 58H, 58I. The third inverse gamma correction unit 52C inversely gamma corrects an input video signal corresponding to a next screen (frame) and linearly converts a luminance value according to a gray value of the video signal. The third error diffusion unit 54C finely adjusts the luminance value between adjacent pixels in the unit pixel area with respect to the pixel data input from the third inverse gamma correction unit 52C. The third subfield mapping unit 56C separates the data from the third error diffusion unit 54C bit by bit and allocates bit by bit corresponding to the subfield according to the luminance relative ratio. The seventh through ninth line memories 58G, 58H, and 58I respectively store one line of image data and supply the stored data to the MPD determination unit 60. The seventh line memory 58G stores one line of data input from the third subfield mapping unit 56C and supplies it to the MPD determination unit 60 for each line. The eighth line memory 58H stores one line of data input from the seventh line memory 58G and supplies it to the MPD determination unit 60 for each line. Similarly, the ninth line memory 58I stores one line of data input from the eighth line memory 58H and supplies the line to the MPD determination unit 60 one by one. Therefore, the seventh to ninth line memories 58G to 58I supply the data of three adjacent lines of the next screen to the MPD determination unit 60.

The frame memory 50 stores one frame data of the current screen and supplies the common data to the current screen data main path and the current screen data subpath in common.

The current screen data main path includes a first inverse gamma correction unit 52A, a first error diffusion unit 54A, and a first subfield mapping unit 56A connected between the frame memory 50 and the MPD determination unit 60. And first to third line memories 58A, 58B, 58C. The first inverse gamma correction unit 52A inversely gamma corrects data input from the frame memory 50 to linearly convert luminance values according to grayscale values of the image signal. The first error diffusion unit 54A finely adjusts luminance values between adjacent pixels in the unit pixel area with respect to the pixel data input from the first inverse gamma correction unit 52A. The first subfield mapping unit 56A separates the data from the first error diffusion unit 54A bit by bit and allocates bit by bit corresponding to the subfield according to the luminance relative ratio. The first subfield mapping unit 56A corresponds to luminance relative ratios 2 ⁰ , 2 ¹ , 2 ² , 2 ³ , 2 ⁴ , 2 ⁵ , 2 ⁶ , 2 ⁷ when the image is displayed with 256 gray levels. Image data is mapped to three subfields. The mapped image data may linearly express grayscale values from 0 to 255 by binary coding of subfields. The first to third line memories 58A, 58B, and 58C respectively store one line of image data and supply the stored one line of data to the MPD determination unit 60.

The current screen data subpath includes a second inverse gamma correction unit 52B, a second error diffusion unit 54B, and a second subfield mapping unit 56B connected between the frame memory 50 and the MPD determination unit 60. And fourth through sixth line memories 58D, 58E, and 58F. The second inverse gamma correction unit 52B performs inverse gamma correction on data input from the frame memory 50, and the second error diffusion unit 54B performs data on the data input from the second inverse gamma correction unit 52B. The luminance value between adjacent cells in the unit pixel area is finely adjusted. The second subfield mapping unit 56B separates the data from the second error diffusion unit 54B bit by bit corresponding to the subfields whose luminance relative ratio is determined by the MPD precode, and divides each bit data into the MPD precode subfield. Assign to The subfields set in the second subfield mapping unit 56B have a luminance relative ratio determined such that emission of light linearly increases in gray scale and time axis so that moving image pseudo contour noise does not occur. These MPD precode subfields may be determined, for example, with a luminance relative ratio as shown in FIG. 5. The mapped image data may not appear as pseudo contour noise because the amount of light emitted from pixels on the boundary region between gray levels increases linearly when the gray level value changes. The fourth and fifth line memories 58D and 58E store data for one line corresponding to the lower rows of the I-th line determined by the MPD determining unit 60. The sixth line memory 58F stores one line of data corresponding to the I-th line, and stores the I-th line data stored in synchronization with the I-th line data output from the second line memory 58B. It supplies to 60.

Meanwhile, a gain adjuster may be provided between the inverse gamma correction units 52A, 52B, and 52C and the error diffusion units 54A, 54B, and 54C to adjust the gain of the input image data.

The MPD determining unit 60 detects a video distortion value for any one cell included in the I-th line and eight neighboring cells adjacent to the current screen and the next screen, that is, the image data corresponding to the 3 × 3 pixel area. In addition, it detects whether an edge image is detected. The MPD determining unit 60 determines that the video distortion value between the 3 × 3 pixel areas of the current screen and the next screen is small or that the 3 × 3 pixel area of the current screen includes a boundary part. The I-th line data D (I) input from the data is supplied to the data alignment unit 62. If it is determined that the video distortion value between the 3 × 3 pixel areas of the current screen and the next screen is greater than or equal to a predetermined threshold, and the 3 × 3 pixel area of the current screen does not include a boundary, The I-th line data D '(I) input from the six-line memory 58F is supplied to the data alignment unit 62.

To this end, the MPD determining unit 60 calculates a video distortion value MPD in each of the 3 × 3 pixel areas of the current screen and the next screen, and selects the largest value among the 3D video areas in the 3 × 3 pixel area. ) If this is expressed as an equation, Equation 1 below.

3 × 3 window MPD value = Max (sfmp (i, j), sfmp (p, q))

Here, sfmp (i, j) means subfield mapping pattern data D (i, j) of the reference cell located at the intersection of the i-th row and the j-th column in the 3x3 pixel area. And p and q are defined as p = i-1, i, i + 1 and q = j-1, j, j + 1, respectively. sfmp (p, q) means subfield mapping pattern data corresponding to each cell of a 3x3 pixel area.

In addition, the MPD determination unit 60 calculates a difference between the luminance value of the data corresponding to the reference cell (i, j) and the luminance value of eight adjacent cells in each of the 3 × 3 pixel areas of the current screen and the next screen. The maximum value of the absolute value of the difference is determined as the boundary value of the 3x3 pixel area. If this is expressed as an expression, Equation 2 below.

3 × 3 window edge value = Max ABS (pv (i, j), pv (p, q))

Here, pv (i, j) refers to the luminance value of the data D (i, j) corresponding to the reference cell located at the intersection of the i th row and the j th column in the 3 × 3 pixel region. pv (p, q) denotes a luminance value of data corresponding to each cell of a 3x3 pixel area.

When the video distortion value and the boundary value are calculated in the unit pixel area of the current screen and the next screen as described above, the MPD determination unit 60 compares the video distortion value and the boundary value with a predetermined threshold and codes the result with a fine gray value according to the result. Either data or MPD precoded data is selected.

The MPD determining unit 60 includes a calculating unit 64 connected to the first to third line memories 58A, 58B, 58C and the seventh to ninth line memories 58G, 58H, 58I, as shown in FIG. The multiplexer 68 connected to the sixth line memory 58F and a multiplexer control unit (hereinafter referred to as a "MUX control unit") 66 for controlling the multiplexer 68 are provided. The calculation unit 64 calculates the video distortion value and the boundary value of the 3 × 3 pixel area in the current screen and the next screen in the same manner as in Equation 1 and Equation 2, and supplies the same to the MUX controller 66. The MUX controller 66 compares the video distortion value input from the calculator 64 with a predetermined first threshold1 and compares the boundary value with a predetermined second threshold2 so that the video distortion value is equal to the first. When the threshold value is larger than the first threshold and smaller than the second threshold, the multiplexer 68 is controlled so that the subfield mapping pattern data from the sixth line memory 58F is supplied to the data alignment unit 62. That is, when it is determined that the subfield mapping pattern data for the corresponding 3x3 pixel area is data having a large video distortion value, the MUX controller 66 selects data coded by MPD precode. If the video distortion value input from the calculator 64 is smaller than the first threshold and the threshold is larger than the second threshold, the MUX controller 66 may convert the subfield mapping pattern data from the second line memory 58B to the data alignment unit. The multiplexer 68 is controlled to be supplied to 62. That is, when the subfield mapping pattern data for the 3x3 pixel area is determined as the boundary image, the MUX controller 66 selects the subfield data in which the gray scale value is finely expressed.

The data aligning unit 62 converts the image data input from the MPD determining unit 60 to the PDP address driver IC in accordance with the resolution format of the PDP.

As described above, the PDP driving method and the multi-pass driving apparatus using the same according to the present invention provide an MPD precode sub that does not show video distortion between the main path and the input image data for subfield mapping the input image data to a fine gray level value. The subfield maps the input image data using the subpath for mapping to the field, determines whether the video is distorted and whether there is a boundary in the unit pixel area of the current screen and the next screen, and codes the data with a fine gray value according to the result. One of the data encoded with MPD precode is selected. As a result, the driving method of the PDP and the multi-pass driving apparatus using the same can display the input image data with a fine gray level value and display the data for which video distortion can be displayed using MPD precode. By doing so, the video distortion noise can be prevented, so that the display quality can be improved.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (10)

A method for dividing image data of one frame into a plurality of subfields and displaying the same on a plasma display panel; Mapping image data of the current screen to subfields in which grayscale values are expressed finely; Mapping image data of the current screen to subfields without video distortion; Mapping image data of a next screen input subsequent to the current screen to subfields; Selecting one of the subfield data in which the gray scale value is expressed finely on the current screen and the subfield data without video distortion in accordance with the video distortion value between the current screen and the next screen. How to drive the display panel. The method of claim 1, Selecting data according to the video distortion value comprises calculating a video distortion value of the input image data; Comparing the video distortion value with a first predetermined threshold; And selecting the data mapped to the subfields without the video distortion when the video distortion value is larger than the first threshold. The method of claim 2, The calculating of the video distortion value may include calculating a video distortion value for subfield mapping data corresponding to a unit pixel area including a plurality of cells; And determining the largest video distortion value among the video distortion values of each of the subfield mapping data of the unit pixel region as the video distortion value of the unit pixel region. The method of claim 1, Determining whether a boundary of the input image data exists; And selecting one of subfields in which the gray value is finely expressed and data mapped to subfields without video distortion, depending on whether the boundary exists. . The method of claim 4, wherein Selecting data according to whether the boundary exists or not includes calculating a boundary value of the input image data; Comparing the threshold with a second predetermined threshold; And selecting data mapped to subfields in which the gray value is finely expressed if the threshold value is larger than the second threshold value. The method of claim 5, The calculating of the boundary value may include detecting luminance values of subfield mapping data corresponding to a unit pixel area including a plurality of cells; Calculating a difference between the luminance value of the subfield mapping data corresponding to the reference cell in the unit pixel region and the luminance value of the subfield mapping data corresponding to the main cells adjacent to the reference cell; And determining an absolute value of the difference between the luminance values as a boundary value of the unit pixel area. The method of claim 4, wherein Selecting data according to the video distortion value includes selecting subfield mapping data without video distortion when the video distortion value is greater than a first predetermined threshold and the threshold value is less than a second predetermined threshold. Method of driving a plasma display panel comprising a. An apparatus for dividing image data of one frame into a plurality of subfields and displaying the same on a plasma display panel, A memory connected to an input line for storing image data of a current screen; A current screen main path for mapping image data from the memory to subfields in which gray level values are expressed finely; A current screen subpath for mapping image data from the memory to subfields without video distortion; A next screen path for mapping image data of a next screen inputted from the input line to subfields; And selecting means for selecting any one of subfield data in which gray level values are expressed finely on the current screen and subfield data without video distortion, according to the video distortion value between the current screen and the next screen. Multi-pass driving device of plasma display panel. The method of claim 8, The current screen main path includes: a subfield mapping unit for mapping the input image data to subfields in which gray level values are expressed finely; A first memory for storing upper first line data among data mapped to subfields in which the gray value is finely expressed; A second memory for storing reference line data corresponding to a lower row of the first line among data mapped to subfields in which the gray value is finely expressed; A third memory for storing lower one line data of the reference line among data mapped to subfields in which the gray value is finely expressed; The current screen subpath includes: a subfield mapping unit for mapping the input image data to subfields without video distortion; And a fourth memory for storing data corresponding to the reference line among the data mapped to the subfields without the video distortion. The method of claim 9, The selecting means includes a calculating unit for calculating a video distortion value for a unit pixel area including a plurality of cells in the current screen and the next screen, and calculating a boundary value indicating whether a boundary exists in the data of the unit pixel area; A multiplexer supplied with subfield mapping data from the second and fourth memories; If the video distortion value is greater than a first threshold and the threshold is less than a second threshold, the subfield mapping data input from the fourth memory is selected, and the video distortion value is smaller than or equal to the first threshold. And a control unit for controlling the multiplexer to select subfield mapping data input from the second memory when the threshold value is larger than a second threshold.