KR100509762B1 - Method and apparatus for eliminating pseudo contour noise of plasma display panel using selective dithering - Google Patents

Abstract

The present invention relates to a method and apparatus for removing pseudo contours of a plasma display panel using selective dithering to reduce moving image pseudo contour noise.

The pseudo contour removing method of the plasma display panel includes dithering all data; Detecting the position of the pixel data whose upper bit changes as a generation portion of pseudo contour noise; Dithering the generated portion of the pseudo contour noise and n pieces of pixel data (where n is a positive integer) adjacent thereto.

Description

Method and apparatus for removing pseudo contour of plasma display panel using selective dithering {METHOD AND APPARATUS FOR ELIMINATING PSEUDO CONTOUR NOISE OF PLASMA DISPLAY PANEL USING SELECTIVE DITHERING}

The present invention relates to a plasma display panel, and more particularly, to a method and apparatus for removing a pseudo contour of a plasma display panel using selective dithering to reduce moving image 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 the gray level of '127' and the gray level of '128' are shifted to the right, the observer in FIG. 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 an upper subfield (MSB), a multi-level subfield method of multiplexing weights of subfields, an equalization pulse to 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, conventional methods for inserting equalization pulses or motion compensation methods using motion vectors include contour noise 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 is difficult to compensate.

Accordingly, an object of the present invention is to provide a method and apparatus for removing pseudo contour of PDP using selective dithering to reduce moving image pseudo contour noise.

In order to achieve the above object, the method for removing the contour of the PDP using the selective dithering according to an embodiment of the present invention comprises the steps of performing dithering on all data; Detecting the position of the pixel data whose upper bit changes as a generation portion of pseudo contour noise; Dithering the generated portion of the pseudo contour noise and n pieces of pixel data (where n is a positive integer) adjacent thereto.

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An apparatus for removing outlines of a PDP using selective dithering according to an embodiment of the present invention includes a first dither processing unit for dithering all data; A detector for detecting the position of the pixel data whose upper bit changes as a generation part of the pseudo contour noise; And a second dither processor for dithering the generated portion of the pseudo contour noise and n pixel data adjacent thereto.

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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. 4 to 8.

Referring to FIG. 4, a PDP according to an embodiment of the present invention includes a pseudo contour area detection unit 33 for detecting a region in which a pseudo contour is generated, and a selective dithering for performing dithering only on the detected pseudo contour area. The processing part 34 is provided.

The PDP includes a sustain electrode pair including a scan electrode and a sustain electrode, and an address electrode intersecting the sustain electrode pair. Discharge cells are arranged in a matrix form between the sustain electrode pairs and the address electrodes.

The digital video data RGB is input to the pseudo outline area detector 33 through the gamma & gain adjuster 31 and the error diffusion & dither processor 32.

The gamma & gain adjusting unit 31 performs gamma correction and gain correction on the digital video data RGB for each of the red data R, the green data G, and the blue data B. FIG.

The error diffusion & dither processing unit 32 diffuses the quantization error component of the digital video data RGB input from the gamma & gain adjustment unit 31 to adjacent pixel data using a Floyd-Steinberg error diffusion filter. Relax In addition, the error diffusion & dither processor 32 dithers the input data by thresholding it with a dither mask (or dither matrix) having a threshold set corresponding to each pixel. The error diffusion & dither processing unit 32 processes error diffusion and dithering for data RGB on the full screen.

The pseudo contour area detector 33 detects a portion in which pseudo contour noise (or false contour) is to be generated from data input from the error diffusion & dither processor 32. For example, as shown in FIGS. 5 and 6, the pseudo contour area detector 33 detects neighboring pixels whose upper bit MSB changes.

FIG. 5 shows an example of a subfield pattern of the pixel region detected by the pseudo contour region detector 34 when it is assumed that 8 subfields are included within one frame period and the default subfield code implements 256 gray levels. 6 shows an example of a region in which pseudo contour noise is generated as a hatched portion.

As shown in FIGS. 5 and 6, neighboring pixels which may generate pseudo contour noise include '15 (11110000) '↔'16 (00001000)', '31 (11111000) '↔'32 (00000100)', This is the case with '63 (11111100) '↔'64 (0000010)', '127 (11111110)' ↔'128 (00000001) '.

When dithering is performed only on the pseudo contour noise region detected by the pseudo contour region detection unit 33 as described above, the pseudo contour noise can be removed without deterioration in image quality due to dithering.

The selective dither processing unit 34 dithers only the pseudo contour noise area detected by the pseudo contour area detection unit 33 to change the position where the pseudo contour noise appears every frame period, thereby distributing the pseudo contour noise.

The observer feels the pseudo contour noise severely when the pseudo contour noise is continuously present at the same position, but the observer hardly feels the pseudo contour noise when the position where the pseudo contour noise is generated in each frame period by the above-mentioned selective dithering process is injected in each frame period. .

The data dithered by this selective dither processor 34 is supplied to the subfield mapping unit 38 via the display data processor 35.

When the logo is displayed on a dark background, the display data processing unit 35 fades out logo data that causes the brightness of the logo to gradually decrease and disappear.

The subfield mapping unit 36 maps data from the selective dither processing unit 34 to a preset subfield pattern. The output data of the subfield mapping unit 36 is supplied to the data driver 37.

The data driver 37 latches the data from the subfield mapping unit 36 and supplies the latched data to the address electrodes for one line every one horizontal period.

The scan driver 38 supplies the reset pulse of the reset period, the scan pulse of the address period, the sustain pulse of the sustain period, and the erase signal to the scan electrodes of the PDP 40.

The sustain driver 39 alternately operates with the scan driver 38 to supply a sustain pulse to the sustain electrode of the PDP 40.

7 and 8 show an example of data conversion by selective dithering.

Referring to FIG. 7, one frame period is divided into 12 subfields, and the luminance weight of the subfield pattern is SF1 (1) -SF2 (2) -SF3 (4) -SF4 (8) -SF5 (16) for each subfield. ) -SF6 (32) -SF7 (32) -SF8 (32) -SF9 (32) -SF10 (32) -SF11 (32) -SF12 (32), the data value of adjacent pixels is' 223- Pseudocontour noise is generated at the position of 225 ',' 223-224 ', and' 223-229 '. If the original data '223-220-221-223-225-226-230' inputted by the pseudo contour area detection unit 33 detects '223-225' as the pseudo contour noise or the appearing area, it is optional. The dither processor 34 dithers left and right n (where n is a positive integer) based on the position, for example, by 3 pixels. Then, in the frame period A (Frame), the data value is converted into '223-223-224-227-228-229-231' by selective dithering. In the frame period B (Frame B) following the frame period A, the data value is converted into '223-217-218-219-221-223-229' by selective dithering. Therefore, the positions where the pseudo contour noise appears in the original data are distributed to different positions in the frame period A and the frame B. FIG.

Referring to FIG. 8, original data '120-121-122-123-124-125-126-127-128-129-130-131-132-133-134-135' is framed by selective dithering. In period A it is converted to '121-122-124-125- (127-128) -130-131-132-133-133-134-134-135-135-136'. When the data string of the frame period A is subjected to selective dithering, the data string of the frame period A becomes '119-120-120-121-121-122-122-123-124-125- (127-128)-' in the frame period B. 130-131-133-134 '. Therefore, the positions where pseudo contour noise '127-128' appear in the frame period A and the frame period B are different, so that the pseudo contour noise is reduced. In addition, the original data '--- 218-219-220-221-222-223-224-225-226-227-228 ---' is' --- 220-221- in the frame period A by selective dithering. (223-224) -226-227-228-229-229-230-230 --- ', and converts to' --- 216-217-217-218-219-220-221- ( 223-224) -226 --- 'so that pseudo contour noise' 223-224 'is dispersed in frame periods A and B.

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 the pseudo contour of the plasma display panel using the selective dithering according to the present invention detects the position where the pseudo contour noise occurs and selectively dithers only the n pixel data adjacent to the pseudo contour noise occurrence position. By doing so, it is possible to prevent image degradation in an area where pseudo contour noise is not generated and to disperse the position where pseudo contour noise is generated by the selective dithering. As a result, the pseudo contour noise removing method and apparatus of the plasma display panel using the selective dithering according to the present invention reduces the pseudo contour noise.

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.

Fig. 3 is a diagram showing the trajectories of the eye and the object when moving image pseudo contour noise appears.

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

FIG. 5 is a light emitting pattern of a subfield pattern for explaining pseudo contour noise detected by the pseudo contour area detector shown in FIG. 4.

FIG. 6 is a diagram illustrating an example of a pseudo contour noise portion detected by the pseudo contour area detector shown in FIG. 4.

7 and 8 are diagrams for describing dithering by the selective dither processing unit shown in FIG. 4.

<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

31: Gamma & Gain Adjuster 32: Error Diffusion & Dither Processing

33: pseudo contour area detection unit 34: selective dither processing unit

35: display data processing unit 36: subfield mapping unit

37: data driver 38: scan driver

39: sustain driver 40: plasma display panel

Claims (8)

Performing dithering on all data; Detecting the position of the pixel data whose upper bit changes as a generation portion of pseudo contour noise; And performing dithering on the occurrence of the pseudo contour noise and n pieces of pixel data adjacent to the pseudo contour noise, where n is a positive integer. Way. delete delete delete A primary dither processor for dithering all data; A detector for detecting the position of the pixel data whose upper bit changes as a generation part of the pseudo contour noise; And a second dither processing unit for dithering the generated portion of the pseudo contour noise and n (where n is a positive integer) pixel data adjacent thereto. Pseudo contour remover. delete delete delete