KR100738585B1 - Plasma Display Apparatus and Image Processing Method there of - Google Patents

Abstract

The present invention relates to a plasma display device, and more particularly, to a plasma display device and an image processing method thereof capable of increasing the accuracy of skin tone region determination.

In the plasma display device according to the present invention, a skin tone detector for determining a skin tone among color information according to an image signal input from the outside, and an extension or erosion with a mask having a size corresponding to a skin tone area determined by the skin tone detector is determined. An extension / erosion processing unit for processing and a reference value calculating unit for calculating a predetermined reference value to determine a mask size according to the skin tone region.

Description

Plasma Display Apparatus and Image Processing Method Thereof

1 is a view showing a typical plasma display panel structure.

2 is a diagram showing a method of implementing an image of a conventional plasma display panel.

3 is a diagram showing skin tone data selected by a conventional skin tone area determination method.

4A and 4B are block diagrams illustrating an image processing apparatus of a plasma display panel according to an embodiment of the present invention.

5 is a view showing the expansion / erosion treatment method according to an embodiment of the present invention.

6 is a view showing that the mask size is adjusted in the expansion / erosion treatment method of FIG.

***** Explanation of symbols for main parts of drawing *****

400: reverse gamma correction unit 410: halftone circuit unit

420: coding circuit portion 430: subfield control circuit portion

440: plasma display panel 450: skin tone area control unit

451: skin tone detection unit 452: expansion / erosion processing unit

453: reference value calculation unit

The present invention relates to a plasma display device, and more particularly, to a plasma display device and an image processing method thereof capable of increasing the accuracy of skin tone region determination.

In general, a plasma display panel is a partition wall formed between a front panel and a rear panel to form a unit discharge cell, and each cell includes neon (Ne), helium (He), or a mixture of neon and helium (Ne + He). An inert gas containing a main discharge gas such as and a small amount of xenon is filled. A plurality of unit discharge cells described above are gathered to form one pixel. For example, a red (R) cell, a green (G) cell, and a blue (B) cell may form one pixel. When a high frequency voltage is applied to such a unit discharge cell to discharge, an inert gas generates vacuum ultra violet 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 is a diagram illustrating a general plasma display panel structure.

As illustrated in FIG. 1, a conventional plasma display panel includes a plurality of scan electrodes 102 and Y formed in pairs on a front substrate 101, which is a display surface on which an image is displayed. The front panel 100 in which the storage electrode pairs are arranged, and the rear panel 110 in which the plurality of data electrodes 113 and X are arranged so as to intersect the plurality of storage electrode pairs described above are formed on the rear substrate 111 forming the rear surface. Combined in parallel with a distance between them.

The front panel 100 is, for example, a scan electrode 102 and Y and a sustain electrode 103 and Z for mutual discharge in one discharge cell and maintaining light emission of the cell, that is, a transparent electrode formed of a transparent ITO material. And a pair of scan electrodes 102 and Y and sustain electrodes 103 and Z provided as a bus electrode b made of a metal material. Scan electrodes 102 and Y and sustain electrodes 103 and Z are covered by one or more upper dielectric layers 104 that limit the discharge current and insulate the electrode pairs, and discharge on top of upper dielectric layer 104. In order to facilitate the condition, a protective layer 105 on which magnesium oxide (MgO) is deposited is formed.

For example, the rear panel 110 may be arranged such that a plurality of discharge spaces, that is, partitions 112 of a stripe type (or well type) for forming the discharge cells are parallel to each other. In addition, a plurality of data electrodes 113 and X for performing address discharge to generate vacuum ultraviolet rays are disposed in parallel with the partition wall 112. On the upper side of the rear panel 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 data electrodes 113 and X and the phosphor 114 to protect the data electrodes 113 and X.

The front panel 100 and the rear panel 110 formed as described above are bonded to each other through a sealing process to form a plasma display panel. In addition, a plasma display panel is provided with a driving unit for driving electrodes such as scan electrodes 102 and Y, sustain electrodes 103 and Z, and data electrodes 113 and X. Make up the device.

The above-described driving unit generates a discharge by supplying a predetermined driving voltage to the plurality of electrodes to display an image. A method of implementing such an image of the plasma display apparatus is shown in FIG. 2.

2 is a diagram illustrating a method of implementing an image of a conventional plasma display panel.

As shown in FIG. 2, the plasma display panel divides one frame period into a plurality of subfields having different discharge times, and emits the plasma display panel in a subfield period corresponding to a gray value of an input image signal. An image is implemented.

Each subfield is divided into a reset period for uniformly generating a 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 a reset period, an address period, and a sustain period. Here, the sustain period is increased at the ratio of 2 ⁿ (n = 0,1,2,3,4,5,6,7) in each subfield. As described above, since the sustain period is changed in each subfield, gray levels of an image can be realized.

Such an image realization method using subfields has a problem in that a dynamic false contour is generated in a moving video. Various methods have been attempted to remove such pseudo contours. As a typical method, there is a method of selecting and applying only subfield mapping data that generates less pseudo contours, and displaying a gray level insufficient by the selection of mapping data by using a halftone method. However, the method causes halftone noise due to halftoning.

Accordingly, various methods for reducing halftone noise have been proposed. Among them, the dynamic pseudo contour mainly occurs in the human skin color, i.e., the skin tone area, so that the skin tone area is determined, and the image signal is processed differently accordingly. That is, by distinguishing the skin tone region from the non-skin tone region, different halftone methods and subfield mapping data are set to be used, and appropriate combinations within each region can reduce dynamic pseudo contours and halftone noise. The method has been proposed.

3 is a diagram illustrating skin tone data selected by a conventional skin tone region determination method.

Figure 3 (a) is a photograph showing the image to be displayed, (b) shows the skin tone data selected according to the conventional skin tone region determination method. Here, the skin tone area is shown in white.

At this time, accuracy is a problem in the conventional skin tone region determination method. For example, when determining the skin tone area, there is a problem in that all data corresponding to the skin tone are simply judged as the skin tone area or the place where the non-pigmented color is overestimated as the flesh color or the place where the flesh color is not the flesh color is not. That is, as shown in (b) of FIG. 3, the skin tone region determination is applied to the small regions of the screen background part not related to the motion of the image, and the boundary portion is not determined in detail, thereby increasing the halftone noise. Will occur.

SUMMARY OF THE INVENTION In order to solve such a problem, an object of the present invention is to provide a plasma display device and an image processing method thereof having improved accuracy of skin tone region determination.

In addition, another object of the present invention is to provide a plasma display device and an image processing method thereof that can provide a further improved image quality by increasing the precision of the image processing.

The technical problem of the present invention is not limited to the above-mentioned thing, and another technical problem to be achieved by the present invention will be clearly understood by those skilled in the art by the effect of the configuration of the present invention.

In accordance with one aspect of the present invention, a plasma display device includes a skin tone detector for determining a skin tone among color information according to an externally input image signal, and a skin tone region determined by the skin tone detector. An expansion / erosion processing unit for expanding or eroding with a mask having a size and a reference value calculating unit for calculating a predetermined reference value to determine a mask size according to the skin tone region.

In addition, the skin tone detection unit generates skin tone data for generating skin tone data by determining whether or not the skin tone is in accordance with the coordinate conversion unit for converting an image signal input from the outside into coordinates advantageous for gradation expression and the coordinates of the coordinate change unit. It is characterized by including a wealth.

The skin tone detection unit may further include a subsampling unit for subsampling skin tone data generated by the skin tone data generation unit.

The reference value may be determined as an edge value.

The reference value calculator may include an edge detector for detecting the edge value.

In addition, the expansion / erosion processing unit may reduce the size of the mask closer to the edge according to the edge value.

In addition, the expansion / erosion processing unit is characterized in that for adjusting the pattern of the mask in accordance with the edge value.

In the image processing method of the plasma display apparatus according to the present invention for achieving the above object, in the image processing method of the plasma display apparatus for detecting the skin tone of the image signal input from the outside, the color according to the image signal input from the outside Detecting a skin tone among the information, a reference value calculating step of calculating a reference value according to the detected skin tone, and an expansion / erosion processing step of expanding or eroding the mask with a size determined according to the reference value.

The skin tone detection step may include a coordinate conversion step of converting an image signal input from the outside into coordinates favorable for gradation expression and generating skin tone data by determining whether the skin tone is skin tone according to the converted coordinates. Characterized in that it comprises a step.

The skin tone detection step may further include a subsampling step of subsampling the skin tone data.

The reference value may be determined as an edge value.

The reference value calculating step may include an edge detection step of detecting the edge value.

In addition, the expansion / erosion process may reduce the size of the mask closer to the edge according to the edge value.

In addition, the expansion / erosion process may be characterized by adjusting the pattern of the mask in accordance with the edge value.

Hereinafter, with reference to the accompanying drawings will be described in more detail the configuration of the plasma display panel according to the present invention.

4A and 4B are block diagrams illustrating an image processing apparatus of a plasma display panel according to an embodiment of the present invention.

As shown in FIG. 4, the plasma display apparatus according to the exemplary embodiment of the present invention includes a plasma display panel 440, an inverse gamma correction unit 400, a halftone circuit unit 410, a coding circuit unit 420, and a subfield. The control circuit unit 430 and the skin tone region control unit 450 are included.

The inverse gamma correction unit 400 inversely gamma corrects an input video signal and linearly converts luminance of a gray value of the video signal.

The halftone circuit unit 410 masks with an error diffusion method or a dither mask pattern for diffusing a quantization error of an image signal input from the inverse gamma correction unit 400 to adjacent cells using data of a lookup table in which halftone information is stored in advance. By performing a dithering method to finely adjust the luminance value, the number of gradations that can be expressed is increased.

The skin tone region controller 450 detects the skin tone region of the external image signal and transfers the data to the halftone circuit 410 and the coding circuit 420.

The skin tone region controller 450 of the present invention can clearly distinguish the skin tone region and the non-skin tone region to enable differentiated image processing according to their characteristics, thereby improving image quality.

Particularly, the plasma display apparatus of the present invention allows the skin tone region controller 450 to post-process the detected skin tone region differently from the related art to obtain more accurate skin tone region information. The action will be described later in FIG. 4B.

The coding circuit unit 420 performs coding for proper image processing through the data coming from the skin tone region controller 450.

The subfield control circuit unit 430 maps an image signal input from the coding circuit unit 420 to a subfield mapping table according to a prestored subfield scanning method and outputs the image signal.

Thereafter, a data alignment unit (not shown) for supplying the mapping data to the driving device of the plasma display panel 440 is included. Thus, an image of the plasma display panel can be realized.

Here, the configuration of the skin tone region controller 450 having the features of the present invention is shown in more detail in FIG. 4B.

The skin tone region controller 450 of the present invention includes a skin tone detector 451, an extension / erosion processor 452, and a reference value calculator 453.

The skin tone detector 451 determines a skin tone region of an image signal input from the outside.

That is, the skin tone detector 451 may include, for example, a coordinate converter 451a, a skin tone data generator 451b, and a subsampling unit 451c to determine the skin tone region.

Here, the coordinate conversion unit 451a converts the image signals of R (red), G (green), and B (blue) input from the outside into color coordinates capable of obtaining luminance representations such as YCbCr, YUV, and HSV. Perform. Such a conversion may be expressed by multiplying a matrix-type filter composed of specific coefficients with the image signal data of R (red), G (green), and B (blue).

The reason for converting the color coordinates in favor of the luminance expression is that the skin tone detection separates the image data of R (red), G (green), and B (blue) into information about the color and the magnitude of the gray scale, thereby displaying the plasma display. It can be expressed more effectively in accordance with the concept of luminance used in the panel.

The skin tone data generator 451b generates skin tone data by determining whether the skin tone is a skin tone based on the color coordinates converted by the coordinate converter 451a. Generates binary data On / Off compared to skin tone. That is, the data value of each color coordinate in a specific range corresponding to the flesh color of the person is designated to detect the portion corresponding to the flesh color on the 2D plane.

In addition, the skin tone detection unit 451 of the present invention may more preferably include a subsampling unit 451c. The subsampling unit 451c may use the skin tone data generated by the skin tone data generation unit 451b. Subsampling not only reduces the amount of calculation of skin tone data detection, but also effectively removes skin tone data of a small area.

The skin tone region determined by the skin tone detector 451 may be determined more precisely through post-processing of the expansion / erosion method.

That is, the expansion / erosion processing unit 452 may increase or reduce the accuracy of skin tone detection by effectively expanding or eroding the skin tone area determined by the skin tone detection unit 451 with a predetermined mask. The description of the method is clarified later in FIG. 5.

In addition, the expansion / erosion processing unit 452 of the present invention may detect the skin tone region more precisely by adjusting the size of the mask described above.

Such a mask may vary in size according to a predetermined reference value. Here, the reference value is determined by the above-described reference value calculator 453.

More specifically, the reference value calculator 453 determines a mask size for the extension / erosion process according to a reference value determined as an edge value as an example of a predetermined reference value. In this example, the reference value calculator 453 may include an edge detector for detecting an edge value, where the edge value may be referred to as a boundary portion on the screen when the gray level difference between neighboring pixels is large. have.

Such a method of detecting skin tones by expanding / eroding according to an edge value, which is an embodiment of the present invention, will be apparent from FIG. 5 and below.

5 is a view showing an extension / erosion treatment method according to an embodiment of the present invention.

5A illustrates an extension / erosion calculation process according to an embodiment of the present invention, and FIG. 5B illustrates an extension operation and an erosion calculation method according to an embodiment of the present invention. At this time, (a) of Figure 5b shows the erosion calculation method, (b) shows the expansion calculation method.

Referring to FIGS. 5A and 5B, after the skin tone detection step and the reference value calculation step for determining the mask size are performed, for example, an extension / erosion operation may be performed in units of 3 * 3 blocks.

First, the erosion operation corresponds to the skin tone data in blocks of the previous line Fp, the current line Fc, and the next line Fn, that is, pixels corresponding to the pixels in the block, as shown in FIG. The AND operation is performed on the skin tone data with a predetermined mask. In other words, the data Ec2 is obtained from the output value obtained by taking the logical AND.

This erosion treatment is to apply a specific mask to areas where skin color is overestimated after skin tone detection.

Next, the expansion operation ORs the skin tone data corresponding to the pixels in the block processed by the erosion operation with a predetermined mask. That is, the final skin tone region determination data Dc2 is obtained from the output value obtained by taking the logical sum.

Such an extension method is to apply a specific mask to areas where skin tone detection number is underestimated as non-pigmented.

In this case, the skin tone data may be calculated using a mask of n * n, but may be calculated by adaptively adjusting the mask size according to a reference value, for example, according to an edge value.

That is, as the result of the expansion / erosion treatment affects the shape of the treatment, especially at the edge, it can be selectively applied depending on the image characteristics in applying the expansion / erosion treatment method. Accordingly, the mask may be adjusted according to the edge value when the extension / erosion process is performed. That is, the closer the edge is to the mask, the smaller the size of the mask can be, thereby increasing the accuracy of skin tone detection at the boundary portion.

In addition to adjusting the mask size, the mask pattern may be adjusted according to the edge value. In other words, by specifying a pattern value so that the pattern of the mask can be formed smoothly along the edge, more detailed skin tone detection is possible.

As shown in FIG. 6, the present invention clearly shows the adaptive adjustment of the size of the mask in the expansion / erosion treatment method.

6 is a view showing that the mask size is adjusted in the expansion / erosion treatment method of FIG.

As shown in FIG. 6, in one embodiment of the present invention, expansion / erosion processing is performed using a mask whose size is adjusted according to a reference value in order to improve the accuracy of skin tone detection. Here, the aspect in which the size of the mask is adjusted is as follows.

d (x, y) is an image signal corresponding to an arbitrary pixel. Here, x and y are coordinates of pixels in the screen.

K (2m + 1,2n + 1) is an expansion / erosion mask.

Here, in an embodiment of the present invention, as m and n are independently increased by 1, the size of the filtering mask may be increased by 2 in the horizontal direction or the vertical direction. Here, if the maximum size that the filtering mask K can have is limited to M × N, the size in the horizontal direction satisfies 0 ≦ m <M, and the size in the vertical direction satisfies 0 ≦ n <N.

First, referring to the pixels of d1 (x1, y1), d1 (x1, y1) is an image signal of a center pixel corresponding to an arbitrary filtering mask, and the center pixel may be arbitrarily designated within an object of a skin tone. In an embodiment of the present invention, the initial m and n are set to 0, and the size of the filtering mask is different from each other by gradually increasing m and n independently. That is, in the predetermined center pixel d1 (x1, y1), the size of the filtering mask is increased to K (1,1), K (3,3), ..., and the skin is filtered and the skin becomes K (11, 11). It will exceed the boundary of the tone object. That is, by recognizing the edge value and adjusting the mask size accordingly, it is possible to provide an improved precision of skin tone detection. Further, accordingly, there is an effect that the quality of an image can be improved by performing differentiated image processing.

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 exemplary embodiments described above are to be understood as illustrative and not restrictive in all aspects, and the scope of the present invention is indicated by the following 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 plasma display device and the image processing method thereof of the present invention have the effect of increasing the accuracy of the skin tone area determination.

In addition, the plasma display device and the image processing method thereof of the present invention have the effect of improving the image quality.

Claims (14)

A skin tone detector for determining a skin tone among color information according to an externally input image signal; An expansion / erosion processing unit for expanding or eroding the mask having a size corresponding to a skin tone area determined by the skin tone detection unit; And A reference value calculator configured to calculate a predetermined reference value to determine a mask size according to the skin tone area; Plasma display device comprising a. The method of claim 1, The skin tone detection unit A coordinate converting unit converting an externally input image signal into coordinates advantageous for gradation representation; And A skin tone data generator for determining skin tone data according to the coordinates of the coordinate converter to generate skin tone data; Plasma display device comprising a. The method of claim 2, The skin tone detection unit And a subsampling unit for subsampling the skin tone data generated by the skin tone data generation unit. The method of claim 1, And said reference value is determined by an edge value. The method of claim 4, wherein The reference value calculation unit And an edge detector for detecting the edge value. The method of claim 4, wherein The expansion / erosion treatment unit And the size of the mask decreases closer to the edge according to the edge value. The method of claim 4, wherein The expansion / erosion treatment unit And controlling a pattern of the mask according to the edge value. In the image processing method of the plasma display device for detecting the skin tone of the video signal input from the outside, Detecting a skin tone from color information according to an externally input image signal; A reference value calculating step of calculating a reference value according to the detected skin tone region; And An expansion / erosion treatment step of expanding or eroding the mask having a size determined according to the reference value; Image processing method of the plasma display device comprising a. The method of claim 8, The skin tone detection step A coordinate conversion step of converting an externally input image signal into coordinates advantageous for gradation representation; And A skin tone data generation step of generating skin tone data by determining whether the skin tone is based on the converted coordinates; Image processing method of a plasma display device comprising a. The method of claim 9, The skin tone detection step And a subsampling step of subsampling the skin tone data. The method of claim 8, And the reference value is determined by an edge value. The method of claim 11, The reference value calculating step And an edge detection step of detecting the edge value. The method of claim 11, The expansion / erosion treatment step And the size of the mask decreases closer to the edge according to the edge value. The method of claim 11, The expansion / erosion treatment step And controlling the pattern of the mask in accordance with the edge value.

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