KR100625478B1 - Plasma display apparatus and image processing method thereof - 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 suppressing noise displayed on a screen when the plasma display device is driven.

In accordance with another aspect of the present invention, a plasma display device includes an inverse gamma correction unit configured to inversely gamma correct an image signal input from an external device; A half-toning unit half-toning the fractional part of the inverse gamma corrected image signal by selectively using any one of dithering or error diffusion every frame; And a subfield mapping unit for mapping the halftoned video signal to a subfield mapping table.

Description

Plasma Display Apparatus and Image Processing Method {Plasma Display Apparatus and Image Processing Method}

1 illustrates a structure of a general plasma display panel.

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

3 is a view for explaining a dithering method of a conventional plasma display device.

4 is a view for explaining an error diffusion method of a conventional plasma display device.

5 is a diagram illustrating a half-toning pattern generated in a conventional plasma display device.

6 is a block diagram illustrating a plasma display device according to an embodiment of the present invention.

7 is a block diagram illustrating an operation characteristic of a half toning unit according to an embodiment of the present invention.

8 illustrates an image implemented according to an embodiment of the present invention.

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

610; Inverse gamma correction unit 620; Gain control

630, 700; Half toning unit 640; Subfield Mapping Section

710; Half-toning bit number determination unit 720; Dithering unit

730; Error diffusion unit 740; Halftone selector

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 suppressing noise displayed on a screen when the plasma display device is driven.

In general, a plasma display device includes a plasma display panel in which a partition wall formed between a front substrate and a rear substrate forms one unit cell. Each cell is filled with a main discharge gas such as neon (Ne), helium (He) or a mixture of neon and helium (Ne + He) and an inert gas containing a small amount of xenon. 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 device has been spotlighted 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. A rear substrate 110 having a plurality of address electrodes 113 arranged so as 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. It is covered by one or more dielectric layers 104 which limit the discharge current of the scan electrode and the sustain electrode 103 provided with the bus electrode b made of a metal material and insulate the electrode pairs. A protective layer 105 in which magnesium oxide (MgO) is deposited is formed on the entire surface of the dielectric layer 104 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 dielectric layer 115 is formed between the address electrode 113 and the phosphor 114 to protect the address electrode 113.

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

As shown in FIG. 2, the plasma display apparatus divides one frame period into a plurality of subfields having different discharge times, and emits a 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.

The conventional plasma display apparatus uses a halftone method such as a dithering method and an error diffusion method as a multi-gradation expression method for improving gray scale expression power and gray linearity. First, the dithering method will be described with reference to FIG. 3.

3 is a view for explaining a dithering method of a conventional plasma display device.

As illustrated in FIG. 3, the dithering method is a method of determining whether or not a carry occurs by comparing a gray value of each pixel with a specific threshold value of the dither mask. At this time, it is intended to increase the expressive power of the insufficient gradation by turning on the off-pixel and turning off the off-pixel.

In addition, the dithering method is a method for adding false noise so that a false contour is not visible. For example, as shown in FIG. 3, a plurality of dither mask patterns corresponding to a plurality of frames, a plurality of lines, and a plurality of columns of the plasma display apparatus are alternately used.

However, the dithering method has a problem in that dithering noise, which reduces image quality, occurs at a specific gray level. In addition, there is a problem that an error indicating how large or small than a threshold value is not considered at all when generating a lift.

An error diffusion method, which is another method, is described with reference to FIG. 4.

4 is a view for explaining an error diffusion method of a conventional plasma display device.

As shown in FIG. 4, the error diffusion method is a method for spatially correcting a discarded error by causing an error generated when the corresponding pixel is quantized to affect adjacent pixels.

Here, the error diffusion method multiplies each error value generated in the image signals a, b, c, and d of adjacent pixels by a specific coefficient. Thereafter, error values obtained by multiplying the coefficients are added to the i value, and then quantized. Thereafter, the error value generated by the quantization is stored in the line memory and repeated for every pixel.

However, the error diffusion method has a problem in that an error diffusion pattern is recognized by a human eye due to a constant error diffusion coefficient that is repeatedly set for each line and every frame because the error diffusion coefficient is set to be constant for adjacent pixels.

On the other hand, conventionally, a method of dithering the upper bits after error diffusion of the lower bits of the image signal data, that is, a method of using the above two methods in combination. This method can make the gradation representation finer, but can generate noise as shown in FIG. 5.

5 is a diagram illustrating a half-toning pattern generated in a conventional plasma display device.

Referring to FIG. 5, in the conventional image processing method of the plasma display apparatus, the lower bits of the fractional portion of the image signal data are error-spread, reflected in the upper bits, and the upper bits are dithered according to the dither mask. Here, the points in FIG. 5 indicate that the lifting has occurred.

In this case, when the raising caused by the error diffusion does not harmonize with the dither mask, the raising may not be uniformly displayed on the entire screen and a pattern may be concentrated in one region. This pattern has a problem of generating noise or flicker when displayed on the screen.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a plasma display apparatus which can suppress noise and flicker displayed on a screen during operation by improving the plasma display apparatus and its image processing method. .

In addition, another object of the present invention is to provide a plasma display device capable of improving gray scale expression by improving the plasma display device and the image processing method thereof.

In order to achieve the above object, the plasma display device of the present invention includes an inverse gamma correction unit for inverse gamma correction of an image signal input from the outside; A half-toning unit half-toning the fractional part of the inverse gamma corrected image signal by selectively using any one of dithering or error diffusion every frame; And a subfield mapping unit for mapping the halftoned video signal to a subfield mapping table.

The half-toning part of the present invention is characterized by alternately selecting the dithering and error diffusion every frame.

The half-toning unit of the present invention may include a half-toning bit number determiner that determines the number of bits of the half-toned fractional part according to the gray value of the video signal.

The number of bits of the present invention is characterized for each pixel during one frame.

The present invention is characterized in that as the gray value increases, the number of half toning bits increases, and as the gray value decreases, the number of half toning bits decreases.

The number of bits of the present invention is characterized by three to seven bits.

The image processing method of the plasma display apparatus of the present invention includes an inverse gamma correction step of performing inverse gamma correction on an image signal input from the outside; Half-toning a half-toning portion of the inverse gamma corrected image signal by selectively using either dithering or error spreading every frame; And a subfield mapping step of mapping the halftoned video signal to a subfield mapping table.

The present invention is characterized in that the dithering and the error diffusion are alternately selected every frame.

The half-toning step of the present invention may include a half-toning bit number determining step of determining the number of bits of the half-toned fractional part according to the gray value of the video signal.

Hereinafter, with reference to the accompanying drawings, a specific embodiment according to the present invention will be described.

6 is a block diagram illustrating a plasma display device according to an embodiment of the present invention.

As shown in FIG. 6, the plasma display device according to the exemplary embodiment includes an inverse gamma correction unit 610, a gain control unit 620, a half toning unit 630, and a subfield mapping unit 640. do.

The inverse gamma correction unit 610 linearly converts the displayed luminance value according to the grayscale value of the input image signal by performing inverse gamma correction on the input image signal through the prestored gamma data.

The gain controller 620 may be adjusted by a user or a set maker with respect to the red, green, and blue image signals corrected by the inverse gamma correction unit 610. Adjust the gain by red, green and blue by multiplying the gain values. In this case, the gain controller 620 may set a color temperature desired by the user or the set maker. In one embodiment of the present invention further includes a gain control unit 620 for performing such a function.

The half toning unit 630 halftones the fractional part of the inverse gamma corrected image signal input from the gain control unit 620 to finely adjust the luminance value displayed according to the gray level value, thereby improving the gray scale expression power. The half-toning unit 630 according to an embodiment of the present invention halftones the fractional portion of the image signal by selectively using either dithering or error diffusion every frame. The description thereof will be described later in more detail.

The subfield mapping unit 640 maps the image signal input from the half toning unit 630 to a preset subfield mapping table.

The data sorter 650 sorts the spatially sorted subfield mapping data input from the subfield mapper 640 into temporal data.

The data driver 660 receives the data aligned in time by the data aligning unit 650 and supplies an address driving pulse to an address electrode (not shown) of the plasma display panel, thereby realizing an image of the plasma display apparatus. Here, the half toning unit according to an embodiment of the present invention will be described in detail with reference to FIG. 7.

7 is a block diagram illustrating an operation characteristic of a half toning unit according to an embodiment of the present invention.

As shown in FIG. 7, the half-toning unit 700 according to an embodiment of the present invention includes a half-toning bit number determining unit 710, a dithering unit 720, an error diffusion unit 730, and a halftone selecting unit. 740.

The half-toning bit number determiner 710 determines the number of bits of the fractional part half-toned according to the gray value of the input video signal.

That is, the gray level of the input video signal is compared with at least one preset threshold, and the video signal is leveled according to the threshold. The number of bits to be halftoned of the video signal is adjusted according to the leveled value. The number of bits to be halftoned is preferably adjusted in the range of 3 to 7 bits.

At this time, the half-toning bit number determiner 710 increases the number of bits half-toned as the gray value of the image signal increases, and decreases the number of bits as the gray value decreases. Accordingly, as the gray scale value is smaller in the low gray scale region, the position of the gray scale value may be changed even in a minute difference, thereby increasing the gray scale expression power.

The half-toning bit number determiner 710 according to an embodiment of the present invention determines the number of bits for each pixel during one frame. In this way, as the number of bits is adaptively determined, the degree of spatial halfning for all pixels during one frame can be adjusted.

The dithering unit 720 dithers a fractional portion of the input image signal using a dither mask. The dithering unit 720 according to an embodiment of the present invention stores a plurality of dither masks having different patterns and sizes in advance, and corresponds to each pixel according to the number of bits determined by the half-toning bit number determining unit 710. Optionally use a dither mask.

The error diffusion unit 720 diffuses an error component obtained by multiplying a fractional part of an input image signal by an error coefficient to adjacent pixels. The error diffusion unit 720 may also select an error diffusion coefficient and an error diffusion direction corresponding to each pixel according to the number of bits determined by the half-toning bit number determination unit 710.

The half toning selector 730 selectively outputs any one of the image signal processed by the dithering unit 720 or the image signal processed by the error diffusion unit 730 every frame.

Preferably, the half-toning selector 730 is composed of a frame counter and a multiplex (not shown) so that one frame alternately according to the frame counter expresses a gray level with a dithered video signal, and the next frame is an error-diffused image. Express the gradation as a signal.

8 illustrates an image implemented according to an embodiment of the present invention.

Referring to FIG. 8, an image signal obtained by dithering 3 bits of a fractional portion of an image signal and an image signal in which 7 bits of error fractions of a fractional portion of an image signal are diffused are displayed. At this time, as the two image signals are alternated for each frame, dithered image signals and error-diffused image signals are accumulated and recognized in time.

In an embodiment of the present invention, since dithering and error diffusion are used for each frame, a problem in which conventional dithering and error diffusion are not harmonized can be prevented.

In addition, in one embodiment of the present invention, halftones can be more reliably performed by selecting the number of bits according to the gray value of the video signal, and by applying different dithering and error diffusion methods.

An image processing method of a plasma display apparatus according to an embodiment of the present invention includes an inverse gamma correction step of inverse gamma correction of an image signal input from an external device; Half-toning a half-toning fractional part of the inverse gamma corrected image signal by selectively using either dithering or error spreading every frame; And a subfield mapping step of mapping the half-toned video signal to the subfield mapping table. In this case, dithering and error diffusion are alternately selected every frame.

The image processing method of the plasma display device according to an embodiment of the present invention has been described in detail through the operation characteristics of the half-toning unit of FIGS.

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 present invention improves the plasma display device and the image processing method thereof, and therefore, there is an effect of suppressing noise and flicker displayed on the screen during driving.

In addition, the present invention has an effect of improving the gray scale expression power by improving the plasma display device and the image processing method thereof.

Claims (12)

An inverse gamma correction unit configured to inverse gamma correct an image signal input from the outside; A half-toning unit half-toning the fractional part of the inverse gamma corrected image signal by selectively using any one of dithering or error diffusion every frame; And A subfield mapping unit for mapping the halftoned video signal to a subfield mapping table Plasma display device comprising a. The method of claim 1, The half toning unit And dithering and error diffusion are alternately selected every frame. The method according to claim 1 or 2, The half toning unit And a half-toning bit number determiner for determining the number of bits of the half-toned fractional part according to the gray value of the image signal. The method of claim 3, And the number of bits is determined for each pixel during one frame. The method of claim 3, And as the gray value increases, the number of half toning bits increases, and as the gray value decreases, the number of half toning bits decreases. The method of claim 3, And the number of bits is not less than 3 bits and not more than 7 bits. An inverse gamma correction step of inversely gamma correcting an image signal input from the outside; Half-toning a half-toning portion of the inverse gamma corrected image signal by selectively using either dithering or error spreading every frame; And A subfield mapping step of mapping the halftoned video signal to a subfield mapping table Image processing method of a plasma display device comprising a. The method of claim 7, wherein And the dithering and error diffusion are alternately selected every frame. The method according to any one of claims 7 to 8, The half toning step And a half-toning bit number determining step of determining the number of bits of the half-toned fractional part according to the gray value of the video signal. The method of claim 9, And the number of bits is determined for each pixel during one frame. The method of claim 9, And the half toning bit number increases as the gray level value increases, and the half toning bit number decreases as the gray level value decreases. The method of claim 9, And the number of bits is 3 bits or more and 7 bits or less.

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