KR20070025185A - Block based image processing device and method for plasma display panel - Google Patents

Abstract

A block-based image processing device of a plasma display panel and an image processing method thereof are provided to reduce false contour noise and halftone noise by displaying gray scales by a block unit. A block forming unit(10) divides the entire screen into a plurality of block units. A first gray scale generation unit(20) generates the whole gray scale of a corresponding block along a center axis of brightness of light when a gray scale ratio corresponding to the center axis of the brightness of the light is over a reference value. A second gray scale generation unit(30) generates the whole gray scale of the corresponding block along the center axis of the brightness of the light when the gray scale ratio corresponding to the center axis of the brightness of the light is less than the reference value. A multiplex unit(40) mixes the gray scales of the first and second gray scale generation units and displays the mixed gray scales during one frame.

Description

Block based image processing device and method for plasma display panel

1 is a perspective view showing the structure of a conventional three-electrode AC surface discharge type PDP.

2 is a diagram illustrating a method of implementing image gradation of a conventional PDP.

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

4 is a diagram illustrating the pseudo contour noise of FIG. 3.

5 is a graph showing a light emission center of each gray level input per frame.

6 is a diagram illustrating the number of gray levels extracted for removing conventional pseudo contour noise.

7 is a schematic diagram of a configuration of an image processing apparatus according to an embodiment of the present invention;

8 is a flowchart of an image processing method according to an embodiment of the present invention.

9 is a diagram illustrating an example of determining a CLTC of a block according to an embodiment of the present invention.

10 is a diagram illustrating an example in which inter-block boundary noise is generated in the present invention.

11 is a diagram illustrating an example of a method for removing inter-block boundary noise according to the present invention.

12 is another embodiment showing a method for removing inter-block boundary noise in the present invention.

<Explanation of symbols for the main parts of the drawings>

10: block forming unit 20: first gradation generating unit

30: gray level generator 40: multiplex unit

50: discrimination unit

The present invention relates to a plasma display panel image processing apparatus and an image processing method, and more particularly, to block a plasma display panel that can improve image quality by removing pseudo contour noise and halftone noise generated when a moving image is implemented in a display apparatus. An image processing apparatus and a method thereof are provided.

In general, a plasma display panel (Plasma Display Panel) is a partition wall formed between the front substrate and the rear substrate to form a unit cell, each of the neon (Ne), helium (He) or a mixture of neon and helium ( The main discharge gas such as Ne + He) and an inert gas containing a small amount of xenon are filled. When discharged by a high frequency voltage, the inert gas generates vacuum ultraviolet rays and emits phosphors formed between the partition walls to realize an image. Such a plasma display panel has a spotlight as a next generation display device because of its thin and light configuration.

1 illustrates a structure of a general plasma display panel. As shown in FIG. 1, a plasma display panel includes a front substrate in which a plurality of sustain electrode pairs formed by pairing a scan electrode 102 and a sustain electrode 103 are formed on a front glass 101, which is a display surface on which an image is displayed. The rear substrate 110 having the plurality of address electrodes 113 arranged to intersect the plurality of sustain electrode pairs on the back glass 111 forming the back surface 100 and the rear surface is coupled in parallel with a predetermined distance therebetween. .

The front substrate 100 may include a scan electrode 102 and a sustain electrode 103, that is, a transparent electrode a made of a transparent indium thin oxide (ITO) material for mutual discharge in one discharge cell and maintaining light emission of the cell. The scan electrode and the sustain electrode 103 provided with the bus electrode b made of a metal material are covered by one or more dielectric layers 104 which limit the discharge current and insulate the electrode pairs, and the upper dielectric layer 104 On the upper surface, a protective layer 105 in which magnesium oxide (MgO) is deposited is formed to facilitate discharge conditions.

The rear substrate 110 is arranged in such a manner that a plurality of discharge spaces, that is, barrier ribs 112 of a stripe type (or well type) for forming discharge cells are maintained in parallel. In addition, a plurality of address electrodes 113 which perform address discharge to generate vacuum ultraviolet rays are arranged in parallel with the partition wall 112. On the upper side of the rear substrate 110, R, G, and B phosphors 114 which emit visible light for image display during address discharge are coated. A lower dielectric layer 115 is formed between the address electrode 113 and the phosphor 114 to protect the address electrode 113.

2 illustrates a method of implementing image gradation of a conventional PDP. Referring to FIG. 2, a method of implementing image gradation of a PDP is performed by dividing a frame into several subfields having different number of emission times.

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 scale 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.

On the other hand, if the moving image is displayed in the above-described sub-field method, unobtrusive contours appear around the moving object according to the gradation, and thus there is a problem in that the display quality is deteriorated. Such pseudo contour noise is also called 'false contour noise'.

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 moved to the right, and the pixel is discharged to the gray level of '127' before the '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, in FIG. 4, the observer moves an object moving to the gray level of 127 and the track of (C) when following the object moving in the (A) trajectory. When following, the brightness is recognized by 128 gradations, but when following an object moving by the trajectory of (B) of the boundary part, the brightness is recognized by 255 gradations.

In order to solve this problem, conventionally, an attempt has been made to reduce pseudo contour noise in the following manner.

First, as shown in FIG. 5, the light emission center of the input grayscale is calculated per frame, and the average trajectory of the light emitting centers is calculated based on the light emission center. Thereafter, the actual grayscales including the light emitting centers are extracted from the calculated light emission centers within the threshold of the average trajectory, and the remaining error diffusion or dithering is performed based on the extracted grayscale values. Image data is processed and compensated.

On the other hand, in the conventional pseudo contour noise removing method, as shown in FIG. 6, the entire grayscale should be represented by only a small number of actual grayscales so that the emission centers of adjacent grayscale levels do not suddenly change, and the remaining grayscales are spread as described above. Or image processing such as dithering. For this reason, the pseudo contour noise is reduced, but the noise caused by image processing used to express insufficient gray scales increases, and also causes a problem in that the implemented image is blurred.

On the other hand, expressing the entire grayscale with the maximum number of actual grayscales that the PDP can represent can reduce halftone noise due to image processing and improve sharpness, but it can reduce the fundamental pseudo contour noise. There is a problem that can not be removed.

The present invention has been proposed to improve the image processing problem in the conventional plasma display device, and to appropriately grasp the importance of pseudo contour noise or half-to-noise noise to provide an image quality improvement plan suitable for a situation in realizing the PDP image. The purpose is to.

According to an aspect of the present invention, there is provided a method, comprising: a block step of dividing an entire screen into a plurality of block units, each block having a plurality of gray levels; A first gradation generating step of generating all gradations of the corresponding blocks as gradations along the luminosity central axis of the light when the ratio of the reconstruction located in the luminance central axis of the light displayed among the gradations of each of the blocks is greater than or equal to the reference value; A second tone generation step of generating an entire gray level of the corresponding block when the ratio of the reconstruction located in the luminance central axis of the light displayed among the entire gray levels constituting each block is equal to or less than a reference value; And a multiplex step of mixing the blocks generated in the step and displaying the same for one frame.

In addition, the reference value of the ratio for determining the first gradation or the second gradation generation of the block is determined in consideration of the information of the previous screen, characterized in that determined within the range of 0-1.

In addition, the boundary noise between adjacent pixels is removed at the boundary between the generated first grayscale and the second grayscale through noise removing means.

The noise removing unit may alternately display the gray level generated in the first gray level generating step and the gray level generated in the second gray level generating step alternately in the horizontal direction on the pixel positioned at the boundary between blocks.

The noise removing unit may alternately display the gray level generated in the first gray level generating step and the gray level generated in the second gray level generating step alternately in the vertical or horizontal direction on the pixels positioned at the boundary portions between blocks.

According to an aspect of the present invention, there is provided an apparatus, including: a block forming unit configured to generate an entire screen by dividing the entire screen into respective block units forming a combination of horizontal and vertical pixels; If the ratio of the reconstruction located in the luminance center axis of the light displayed among the entire gray levels of each block generated by the block forming unit is greater than or equal to the reference value, the first gray level generation generates the entire gray level of the corresponding block as the gray level along the luminance center axis of the light. part; A second gray level generator for generating a real gray level of the entire gray level of the corresponding block when a ratio of the reconstruction located in the luminance center axis of the light displayed among the grays forming each block formed by the block forming unit is equal to or less than a reference value; And a multiplex unit configured to display gray scales generated by the first gray scale generator and the second gray scale generator for one frame.

According to a feature of the present invention, the entire screen is divided into a plurality of block units, each block being divided again into a plurality of gray levels, and a gray level between grays and grays positioned on the luminance center axis of light according to a combination of subfields. The gray scales according to two generation steps are displayed during one frame through a first gray scale generation step of generating a second gray level generation step and a second gray scale generation step of generating an entire gray level according to a combination of subfields. In this case, when the gray scale generated in the first gray scale generation step is displayed, the pseudo contour may be reduced, and when the gray scale generated in the second gray scale generation step is displayed, the half toning noise may be reduced.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

7 is a schematic diagram of an apparatus for image processing according to an embodiment of the present invention, and FIG. 8 is a flowchart for explaining an image processing method.

First, a schematic configuration of an image processing apparatus according to an embodiment of the present invention as shown in FIG. 7 will be described.

 A block forming unit 10 for generating the entire screen by dividing each block unit forming a combination of horizontal and vertical pixels, and the luminance of light displayed in the entire gray levels of each block generated by the block forming unit 10. When the ratio of the reconstruction located in the central axis is greater than or equal to the reference value, the first gray scale generator 20 generates the same gray scale along the luminance luminance axis of the light in the same manner, and each block generated by the block forming unit. If the ratio of the reconstruction located in the luminance central axis of the displayed light out of the total gradations is less than the reference value, the second gradation generator 30 generates the entire gradations of the block in real gradation, and the first gradation generator and the second gradations. Whether to generate the multiplex unit 40 displaying the gray level generated by the generation unit for one frame and the block formed by the block forming unit as the first gray level Otherwise, the determination unit 50 determines whether to generate the second tone.

On the other hand, the image processing method of the present invention based on the configuration as shown in Figure 8 is made of the following steps.

First, in the blocking step (ST 1), the entire screen is divided into a plurality of blocks having a size of 4 * 4, wherein the size of the block is based on 4 * 4 as the number of pixels in the vertical and horizontal directions, but 8 * 8, 16 * 16, 32 * 32 and the like can be used in various sizes, this embodiment will be described based on 4 * 4.

Subsequently, in the first gradation generation step ST 2, the gradation weights are positioned between a predetermined number of gradations and a predetermined number of gradations located on the luminance center axis of the light displayed among all the gradations represented by the combination of subfields having different gradation weights. Generates the entire gradation of gradations.

At this time, the predetermined number of grays positioned on the luminance center axis of the light are grays of the points illustrated in FIGS. 5 and 6.

Such gray levels are to reduce pseudo contours generated when the image signal is processed through an inverse gamma correction step (not shown) during the image processing step of the plasma display panel. In order to reduce pseudo contours, only grayscales along the luminance center axis of light are used so that the variation in the emission centers between grayscales is minimized, and grayscales located in between are generated in an additional manner, thereby generating 256 total grayscales from 0 to 255. Do it. This method is defined as centroid of light tracking code (CLTC).

This method reduces the fall-container noise but reduces the number of real gradations that can be expressed, which requires a large amount of image processing such as dithering and error diffusion, resulting in adverse effects (halftone noise). ) Will occur a lot.

On the contrary, when the plasma display device is displayed using only a real gray level instead of using the CLTC method, the signal noise due to image processing is small, but the fall-container noise is increased due to the characteristics of the display device using the subfield driving. In the present invention, the two methods are properly combined.

That is, if there are many pixels using CLTC in the block, the entire block is applied with the CLTC corresponding to the first gray level, otherwise the real gray level corresponding to the second gray level is applied. Which one to use is determined by the number of pixels to use CLTC in the block.

At this time, the condition in which the CLTC block is generated is shown in Equation 1 below.

In the above equation, r is the ratio of CLTC pixels in the block, r _th is a reference value (0 to 1) which is a block generation condition, A is the number of CLTC pixels in the block, and a and b are the matrix sizes of the block, respectively. Indicates.

That is, FIG. 9 shows an example of discriminating a block with r _th as 0.3. In the case where the number of CLTC pixels is 13 out of 16 pixels, the pixel ratio is calculated as 0.8125. In the case where the number is 4, the pixel ratio is calculated as 0.25 and smaller than the reference value, so that it is determined as a real gray scale block corresponding to the next second gray scale generation step.

On the other hand, in the subsequent second gray scale generation step ST 3, when the ratio of the positions located on the luminance central axis of the displayed light is equal to or less than the reference value, the entire gray scales displayed by the combination of the subfields having different gray weights are combined with the subfields. As a result, it is processed as a real gray block displayed through actual discharge.

Such real gradation is to reduce halftone noise generated when the image signal is processed through halftoning after inverse gamma correction of the plasma display panel.

Thus, CLTC many blocks Falls konteo noise processing forms a primary thread based Joe large block may be referred to as a small way halftone noise (image processing noise), the determination reference value (r _th) of the set blocks each By setting the amount of CLTC pixels (pixels) in each block, two noises can be efficiently reduced.

Thereafter, in the multiplex step ST 4, each CLTC block and a real gray level block generated through the first gray level generation step or the second gray level generation step are mixed and displayed for one frame.

As described above, the present invention reduces the fall-container noise and the half-tone noise to display the image more clearly. This method of the present invention is called block based adaptive gradation.

On the other hand, when using the "block-based adaptive gradation representation method" of the present invention, as shown in Fig. 10, boundary noise occurs at the boundary between the block using CLTC gradation and the block using real gradation. It is removed using a separate noise removing means.

That is, as the noise removing means used in the present invention, as shown in FIG. 11 or FIG. 12, the pixels located at the boundary between blocks can be removed by a blending method so that they can be alternated in a vertical or horizontal direction. By alternating the dithering masks for each frame, the boundary noise can be reduced.

Therefore, when the " block-based adaptive gray scale representation method " of the present invention is used, gray scale expression for displaying an image more clearly by reducing false-converter noise and halftone noise generated in the display device can be performed. It can be seen that the noise generated at the boundary portion can also be reduced.

As such, the technical configuration of the present invention described above can be understood by those skilled in the art that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention.

Therefore, the above-described embodiments are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the appended claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

As described above, the present invention provides a subfield scanning method by displaying in units of blocks by combining a method of minimizing the variation in emission center between gray levels and a method of using a large number of real gray scales in a display apparatus using a subfield scanning method. In this way, the pseudo contour noise and the half-to-noise noise generated in the display device driven by the method are reduced to realize the display image more clearly.

Claims (9)

A block forming step of dividing each pixel forming a whole screen into a plurality of block units; A first gradation generating step of generating all gradations of the corresponding blocks with gradations along the luminosity central axis of the light when the ratio of the reconstruction located on the luminance central axis of the light displayed on the entire screen made by each block is greater than or equal to the reference value; A second gray level generating step of generating a real gray level of all grays of the corresponding block when a ratio of the reconstruction located on the luminance center axis of the light displayed among the entire screens formed by each block is equal to or less than a reference value; And A multiplex step of mixing the blocks generated in the above step and displaying them for one frame; An image processing method through blocking of the plasma display panel comprising a. The method according to claim 1, The reference value of the ratio for determining the first gradation or the second gradation generation of the block is determined in consideration of the information of the previous screen, but is determined within the range of 0 ~ 1, the image processing method by blocking the plasma display panel . The method according to claim 1, And removing boundary noise appearing between adjacent blocks due to the difference between the generated first gray level and the second gray level using noise removing means. The method according to claim 3, The noise removing unit displays the grays generated in the first grayscale generation step and the grayscales generated in the second grayscale generation step alternately in a horizontal direction on the pixels positioned at the portions bordered by the blocks. Image processing method through blocking of the. The method according to claim 3, The noise removing unit displays a gray level generated in the first gray level generation step and a gray level generated in the second gray level generation step alternately in a vertical direction on the pixels positioned at the boundary portions between blocks. Image processing method through blocking of the. The method according to claim 2, And the reference value is adjusted according to the information of the previous frame and the gradation state of the entire block. A block forming unit configured to generate the entire screen by dividing the entire screen into respective block units forming a combination of horizontal and vertical pixels; If the ratio of the reconstruction located in the luminance center axis of the light displayed among the entire gray levels of each block generated by the block forming unit is greater than or equal to the reference value, the first gray level generation generates the entire gray level of the corresponding block as the gray level along the luminance center axis of the light. part; A second gray scale generator for generating a real gray scale of the corresponding gray scale when the ratio of the reconstruction located in the luminance center axis of the light displayed among the gray scales of the blocks formed by the block forming unit is equal to or less than a reference value; And a multiplex unit for mixing the gray scales generated by the first gray scale generator and the second gray scale generator for display for one frame. The method according to claim 7, The block generated by the block forming unit is configured to determine the reference value of the ratio for determining the first gradation or the second gradation in consideration of the information on the previous screen, the reference value is determined within the range of 0 ~ 1 An image processing apparatus by blocking a plasma display panel. The method according to claim 7, And the block forming unit forms the same number of horizontal and vertical pixels as one block.

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