KR100503601B1 - Method and apparatus for eliminating contour noise of plasma display panel - Google Patents

Abstract

The present invention relates to a method and apparatus for removing contour of a plasma display panel to completely remove moving image pseudo contour noise.

The method and apparatus for removing the contour of the plasma display panel reduce the pseudo contour noise existing in the motion detection area, detect the motion of the image based on the motion detection area, and derive a compensation value according to the motion of the image.

Description

Method and apparatus for removing contour of plasma display panel {METHOD AND APPARATUS FOR ELIMINATING CONTOUR NOISE OF PLASMA DISPLAY PANEL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display panel, and more particularly, to a method and an apparatus for removing an outline of a PDP to completely remove moving picture pseudo contour noise.

As the information processing system develops and its spread is expanded, the importance of the display device as a means of transmitting visual information is increasing. Cathode ray tubes (CRTs), which dominate the display device, have large size, high operating voltage, and display distortion. Recently, liquid crystal displays (LCDs), field emission displays (FEDs), and plasma display panels (hereinafter referred to as "PDPs") can solve the disadvantages of cathode ray tubes. Flat panel display devices are being developed.

The PDP displays an image by excitation of phosphors by vacuum ultraviolet rays generated when the inert gas is discharged. Such a PDP is not only thin and large in size, but also simple in structure, and has a high luminance and high luminous efficiency as compared to other flat display devices. In particular, 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 electrodes from sputtering caused by discharge.

Referring to FIG. 1, an AC surface discharge type PDP includes a front glass substrate 1 on which an upper electrode 9 is formed, and a back glass substrate 2 on which an address electrode 4 is formed.

The front glass substrate 1 and the rear glass substrate 2 are spaced apart in parallel with the partition 3 therebetween. A mixed gas such as Ne + Xe, He + Xe, He + Ne + Xe is injected into the discharge space provided by the front glass substrate 1, the rear glass substrate 2, and the partition wall 3. The upper electrode 9 is paired with two in one plasma discharge channel. Each of the upper plate electrodes 9 includes a wide transparent electrode and a narrow metal bus electrode connected to one side edge of the transparent electrode. Any one of the pair of top electrodes 9 causes an opposite discharge with the address electrode 4 in response to the scan pulse supplied in the address period, and then the adjacent top electrodes 9 in response to the sustain pulse supplied in the sustain period. ) And the scan electrode causing surface discharge. In addition, the other upper electrode 9 paired with the scan electrode is used as a sustain electrode to which a sustain pulse is commonly supplied.

The top dielectric layer 7 and the passivation layer 8 are stacked on the front glass substrate 1 on which the top electrodes 9 are formed. The upper dielectric layer 7 serves to limit the discharge current during plasma discharge and to accumulate wall charges during discharge. The protective film 8 is usually made of magnesium oxide (MgO), and prevents damage to the top dielectric layer 7 caused by sputtering generated during plasma discharge and improves the emission efficiency of secondary electrons.

A lower dielectric layer 6 is formed on the rear glass substrate 2 to cover the address electrodes 4. The lower dielectric layer 6 serves to protect the address electrodes 4. On the lower dielectric layer 6, partition walls 3 for dividing the discharge space are formed. On the surfaces of the lower dielectric layer 6 and the partition walls 3, phosphors 4 are excited by vacuum ultraviolet rays to generate visible light of red, green and blue (R, G, B).

The discharge mechanism of the PDP is as follows. When a voltage is applied between two electrodes of the PDP, a potential is formed in the discharge space, and a potential is generated in the pixel as the gas atoms and molecules collide with each other and ionization proceeds. The charged particles generated by the gas discharge are accumulated on the surface of the dielectric layer 7 according to the polarity of the electrode. The negative and positive charges accumulated on the surface of the dielectric layer 7 are called wall charges, and the voltage of the pixel charged by the wall charges is called a wall voltage. If the polarity of the wall charge sufficiently accumulated on the surface of the dielectric layer 7 is opposite to the polarity of the external voltage applied to the electrode, the discharge is erased while the wall voltage and the external voltage are canceled out. When the polarities of the external voltages are reversed and the polarities of the wall voltages and the external voltages are the same, the total voltage applied to the discharge space is the sum of the external voltages and the wall voltages. .

The PDP is time-divisionally driven in a so-called ADS (Address and Display Seperated) method, which is divided into an address period for selecting a pixel and a sustain period for causing display discharge in the selected pixel, in order to realize the gradation of the image. That is, one frame period is divided into several subfields in which the sustain discharge number is set differently according to the luminance weight, and each subfield is divided into a reset period, an address period, and a sustain period. For example, when the image is to be displayed with 256 gray levels, a frame period (16.67 ms) corresponding to 1/60 second is divided into eight subfields SF1 to SF8 as shown in FIG. As described above, each of the eight subfields SF1 to SF8 is divided into a reset period, an address period, and a sustain period. The reset period and the address period of each subfield are the same for each subfield, while the sustain period and the number of sustain pulses allocated thereto are 2 ⁿ (n = 0,1,2,3,4,5,6) in each subfield. , 7).

However, when the moving image is displayed by the subfield method, unobtrusive outlines appear around the moving object according to the gray level, resulting in a poor display quality. Such pseudo contour noise is also called 'false contour'. Pseudo contour noise is the tendency of the human eye to follow a moving object on the screen, the tendency of the human eye to follow a moving object at a fixed position of the retina for one frame period, and the vicinity of the moving object at a fixed position of the retina for one frame period. The brightness of the pixels is accumulated together to cause the human to perceive the brightness different from the actual brightness. For example, when an object moves to the right at a speed of 2 pixels / frame as shown in FIG. 3, the gray level of '127' and the '128' are shifted to the right, and the pixel is discharged to the gray level of '127' and then '128'. Discharge occurs with a gray scale of '. At this time, the contour noise of the brightness brighter than the brightness due to the gray level change is generated in the contour portion of the moving object. In other words, when the gray level of '127' and the gray level of '128' are shifted to the right, the observer in FIG. 4 follows the gray level of 127 when following an object moving in the A trajectory and 128 when following an object moving in the trajectory of C. The brightness is recognized by the gray scale of, but the brightness is recognized by the gray scale of 255 when following the moving object with the trajectory of B of the boundary portion.

In order to solve this problem, a method of reordering subfields, a method of dividing a subfield corresponding to the most significant subfield (MSB), a multi-level subfield method of multiplexing weights of subfields, an equalization pulse (or a driving pulse) A method of inserting an equalizing pulse and a motion compensation method using a motion vector have been proposed. Among these methods, a method of inserting equalization pulses using a motion vector or a motion compensation method has been known as the best method of removing contour noise without loss of sharpness or small detail.

However, the conventional method of inserting equalization pulses using a motion vector or a motion compensation method generates contours in real time due to excessive computation and large computational algorithms and hardware complexity in calculating motion vectors by motion estimation. There is a problem that it is difficult to compensate for noise.

Accordingly, it is an object of the present invention to provide a method and apparatus for removing outlines of a PDP to completely remove moving picture pseudo contour noise.

In order to achieve the above object, the method for removing the contour of the PDP according to an embodiment of the present invention comprises the steps of detecting the area of generation of pseudo contour noise; Reducing pseudo contour noise present in the motion detection region; Detecting motion of an image based on the motion detection area; Deriving a compensation value according to the movement of the image and adding and subtracting the compensation value to the image data.

The compensation value is determined according to the speed and direction of the movement.

An outline removing device of a PDP according to an embodiment of the present invention includes: a pseudo outline area detecting unit for detecting a generation area of pseudo outline noise; A filter for reducing pseudo contour noise present in the motion detection region; A motion detector configured to detect motion of an image based on the motion detection area; And a compensation unit for deriving a compensation value according to the movement of the image and adding or subtracting the compensation value to the image data.

The filter converts data values such that only one pseudo contour noise exists in the motion detection region.

The filter may copy a specific pixel value in the motion detection region to adjacent pixels.

The filter may remove all pseudo contour noise in the motion detection region.

The compensation unit is characterized in that for determining the compensation value according to the speed and direction of the movement.

Other objects and features of the present invention in addition to the above object 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. 5 to 12.

Referring to FIG. 2, the PDP according to the embodiment of the present invention includes a pseudo contour compensator 30 for detecting a motion and compensating for pseudo contour noise in a region where only a pseudo contour is generated.

The digital video data RGB is gamma corrected and gain corrected for each of the red data R, the green data G, and the blue data B by the gamma & gain adjusting unit 32 via the frame memory 31.

The error diffusion & dither processing unit 33 spreads the unrepresentable error components of the digital video data RGB input from the gamma & gain adjustment unit 32 to adjacent pixels using a Floyd-Stenber error diffusion filter. Dithering is performed on the digital video data RGB in units of a window including a number of cells.

The pseudo contour compensator 30 may include a pseudo contour area detector 34, a homogeneous filter 35, and a motion detector connected between the error diffusion and dither processor 33 and the subfield mapping unit 38. 36) and a compensating unit 37.

The pseudo contour area detector 34 detects a portion in which pseudo contour noise (or false contour) is to be generated from the data input from the error diffusion & dither processor 34. For example, neighboring pixels in which the most significant bit MSB changes among the on data are detected as shown in FIGS. 6 and 7.

FIG. 6 shows an example of a subfield pattern of the pixel area detected by the pseudo contour area detector 34 when it is assumed that 8 subfields are included within one frame period and the default subfield code implements 256 gray levels.

FIG. 7 shows a pseudo contour area detector 34 when two subfields corresponding to the most significant bit are divided into six subfields each having a weight of 32, and the number of subfields included in one frame period is twelve. An example of the subfield pattern of the pixel area detected by is shown.

As shown in FIGS. 6 and 7, neighboring pixels that may generate pseudo contour noise include '15'↔'16', '31'↔'32', '63'↔'64', and '127'↔. This is the case with a gray value such as '128'.

8 shows an example of a pseudo contour noise region (hatched portion) detected by the pseudo contour region detector 34.

When motion compensation is performed only on the pseudo contour noise area (or block) detected by the pseudo contour area detection unit 34 as described above, image quality deterioration in a portion where pseudo contour noise is not generated by the compensation value generated during motion compensation is performed. There is no.

The homogeneous filter 35 removes the pseudo contour noise region in the motion detection window before copying the motion, or copies the gray level value of a specific pixel to adjacent pixels so that only one pseudo contour noise region exists in the motion detection window. For example, if the digital video data RGB input to the homogeneous filter 35 is 127-128-127-127-128-128-127, the position where pseudo contour noise appears between those data is between 127 and 128. 4 pcs. For this data sequence, the homogeneous filter 35 copies the gray level value 127 of a specific pixel to adjacent pixels so as to eliminate the position where the pseudo contour noise appears as shown in FIG. 9 or convert the data value so that only one pseudo contour noise exists. . Also, if the digital video data RGB input to the homogeneous filter 35 is 127-127-127-128-100-100-100, the position where pseudo contour noise appears between these data is between 127 and 128, and 128 and 128. 2 between 100. The homogeneous filter 35 converts the data values such that only one position where pseudo contour noise appears as shown in FIG. 9 by copying or replacing the gray value 127 of a specific pixel to an adjacent pixel.

The reason for employing the homogeneous filter 35 is that it is difficult to find a motion if there are positions where a plurality of weft contour noises appear in the motion detection window at the time of motion detection.

On the other hand, pseudo contour noise appearing at an edge part, for example, at a boundary between a moving object and a background has an edge emphasis effect. In addition, when the data conversion of the pseudo contour noise of the edge portion is wrong, an edge blur phenomenon may occur. For this reason, the homogeneous filter 35 bypasses the data to the motion detector 36 without converting the data value at the edge portion.

The motion detector 36 sets a motion detection window including a predetermined number of pixels and how much the area where the pseudo contour noise appears between frames moves left and right as shown in FIG. 10 based on the motion detection window 40. The interframe motion information fmi is indicated and the interframe motion information fmi is supplied to the compensator 37.

The compensator 37 determines a compensation value (number of equalizing pulses) according to the inter-frame motion direction and speed based on the inter-frame motion information fmi from the motion detector 36, and the compensation value is homogeneous filter 35. The pseudo contour noise is removed by adding or subtracting to the input data. For example, as shown in FIG. 11, when an image adjacent to 127 gradations and 128 gradations moves to the left at a speed of 3 pixel / frame, dark pseudo contour noise corresponding to gradations of '121' and '101' between 127 and 128 Will appear. In this case, the compensator 37 derives the compensation value '31' and adds the compensation value '31' to 128 as shown in FIG. 12 to increase the brightness in the boundary area between 127 and 128. On the contrary, if an image adjacent to 127 gray levels and 128 gray levels moves to the right at a speed of 3 pixels / frame, bright pseudo contour noise appears between 127 and 128. In this case, the compensator 37 derives the compensation value and subtracts the compensation value from 127 to lower the brightness in the boundary area between 127 and 128. In addition, the compensator 37 sets the compensation value to a relatively large value when the movement speed is high, and sets the compensation value to a relatively small value when the movement speed is relatively low.

The subfield mapping unit 38 stores an average brightness of the current image based on an average picture level APL, which is prestored and input from the APL detector 39, in which subfield patterns having different gradation values and sustain pulse numbers are set in advance. If high, the data is mapped to the subfield pattern to which a relatively small number of sustain pulses are assigned. If the average brightness of the current image is small, the data is mapped to the subfield pattern to which a relatively large number of sustain pulses are assigned.

The APL detector 39 detects the average brightness level of the data input from the gamma & gain adjuster 32 in units of frames, derives the average image level information, and supplies the average image level information to the subfield mapping unit 38. do.

The data output from the subfield mapping unit 38 is supplied to the address electrode (or data electrode) of the PDP via the data alignment circuit and the data driving circuit of the PDP (not shown).

Meanwhile, although the embodiment has been described based on the example applied to the PDP, it may be applied to other flat panel display devices or DMDs that process digital image data.

As described above, the method and apparatus for removing contour of PDP according to the present invention detects the position where pseudo contour noise is generated to prevent image degradation in the area where pseudo contour noise is not generated and to generate pseudo contour noise in the motion detection region. By minimizing the position, the number of cases where contour noise is generated can be reduced, so that the contour noise can be reduced, and the motion can be detected more accurately. In addition, the method and apparatus for removing contour of a PDP according to the present invention can completely remove moving picture pseudo contour noise by deriving a compensation value according to the motion information and adding and subtracting the compensation value to data. Furthermore, according to the method and apparatus for removing the contour of the PDP according to the present invention, it is possible to reduce the complexity of hardware and algorithms in motion detection and to lower the probability of obtaining a wrong motion vector.

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.

1 is a perspective view showing a conventional three-electrode alternating surface discharge plasma display panel.

2 is a diagram illustrating a default subfield pattern obtained by dividing one frame period into eight subfields.

3 is a diagram illustrating an example in which pseudo contour noise appears.

FIG. 4 is a diagram illustrating a rule of an eye and an object in a moving image as shown in FIG. 3.

5 is a block diagram illustrating a contour removing apparatus of a plasma display panel according to an exemplary embodiment of the present invention.

6 and 7 are light emission patterns of a subfield pattern for explaining the pseudo contour noise detected by the pseudo contour area detector shown in FIG. 5.

FIG. 8 is a diagram illustrating an example of a pseudo contour noise area detected by the pseudo contour area detector shown in FIG. 5.

FIG. 9 is a diagram illustrating an example of a pseudo contour noise region removed by the homogeneous filter shown in FIG. 5.

FIG. 10 is a diagram illustrating an example of a motion detected by the motion detector shown in FIG. 5.

FIG. 11 is a diagram illustrating an example of pseudo contour noise that appears as a peak black between gradations '127' and '128'.

FIG. 12 is a diagram illustrating an example of a compensation value derived by the compensation unit illustrated in FIG. 5 and data to which the compensation value is assigned.

<Description of Symbols for Main Parts of Drawings>

1: front glass substrate 2: rear glass substrate

3: bulkhead 4: address electrode

5: phosphor 6,7: dielectric layer

8: protective film 9: top electrode

30: pseudo contour compensation unit 31: frame memory

32: gamma & gain adjusting unit 33: error diffusion & dither processing unit

34: pseudo contour area detection unit 35: homogeneous filter

36: motion detection unit 37: compensation unit

38: subfield mapping unit 39: APL detection unit

Claims (7)

Detecting a generation area of pseudo contour noise; Reducing pseudo contour noise present in the motion detection region; Detecting a motion of an image based on the motion detection area; Deriving a compensation value according to the movement of the image and adding or subtracting the compensation value to the image. The method of claim 1, And the compensation value is determined according to the speed and direction of the movement. A pseudo contour area detector for detecting a generation area of pseudo contour noise; A filter for reducing pseudo contour noise present in the motion detection region; A motion detector configured to detect motion of an image based on the motion detection area; And a compensation unit for deriving a compensation value according to the movement of the image and adding or subtracting the compensation value to the image. The method of claim 3, wherein And the filter converts data values such that only one pseudo contour noise exists in the motion detection region. The method according to claim 3 or 4, And the filter copies a specific pixel value in the motion detection region to adjacent pixels. The method according to claim 3 or 4, And the filter removes all of the pseudo contour noise in the motion detection region. The method of claim 3, wherein And the compensation unit determines the compensation value according to the speed and direction of the movement.