KR100561338B1 - Image processing method and plasma display panel - Google Patents

Abstract

The present invention relates to an image processing method for improving low gradation expression. Since the light emission luminance is higher when the G (Green) signal is applied to the video display device than the R (Red) and Blue (B) signals among the input video signals, the half having the same pattern for each of the R and B video signals has the same pattern. Image processing is performed by using a toning technique, and image processing is performed by using a half-toning technique having a different pattern for each G image signal. In this case, an error diffusion method or a dithering method may be used as the half-toning technique. That is, the position of the light emitting pixel of the G cell is framed by varying the shape of the error diffusion kernel for each frame in applying the error diffusion to the G image signal having high emission luminance or by changing the dither matrix for each frame in applying the dithering. The average brightness of the G cells can be reduced by dispersing each other. Accordingly, there is a unique effect of reducing the visibility of light emission of the G cell generated when displaying low gray scale by reducing the average light emission luminance of the G cell, thereby improving the low gray scale expressive power.

PDP, Kernel, Error Diffusion, Red, Green, Blue, Luminance Luminance, Dithering

Description

Image processing method and plasma display panel {METHOD OF PROCESSING IMAGE AND PLASMA DISPLAY PANEL}

1 is a partial perspective view of an AC plasma display panel.

2 is a diagram illustrating an electrode array of a plasma display panel.

3 is a diagram illustrating a gray scale display method of a plasma display panel.

FIG. 4 is a diagram illustrating an error diffusion method generally used in a plasma display panel. FIG. 4A is a block for an error diffusion processing algorithm (Floyd-Steinberg Algorithm), and FIG. 4B is used at this time. It is a figure which shows the kernel (KERNEL).

5 is a schematic plan view of a plasma display panel according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a kernel (KERNEL) used for each frame for R and B video signals in an error diffusion method according to an exemplary embodiment of the present invention.

7 is a diagram illustrating a kernel KERNEL used for each frame for a G (Green) video signal in the error diffusion method according to an embodiment of the present invention.

8A and 8B are diagrams showing examples of a 2 × 2 dither matrix used in applying a dithering method according to an embodiment of the present invention.

The present invention relates to an image processing method, and more particularly, to an image processing method for improving low gray level expressive power and a plasma display panel using the same.

Recently, flat display devices such as a liquid crystal display (LCD), a field emission display (FED), and a plasma display panel have been actively developed. Among these flat panel display devices, the plasma display panel has advantages of higher luminance and luminous efficiency and wider viewing angle than other flat panel display devices. Therefore, the plasma display panel is in the spotlight as a display device to replace a conventional cathode ray tube (CRT) in a large display device of 40 inches or more.

A plasma display panel is a flat panel display device that displays characters or images using plasma generated by gas discharge, and tens to millions or more of pixels are arranged in a matrix form according to their size. The plasma display panel is classified into a direct current type and an alternating current type according to a shape of a driving voltage waveform applied and a structure of a discharge cell.

In the DC plasma display panel, the electrode is exposed without the discharge space insulated, so that the current flows in the discharge space while the voltage is applied, and there is a disadvantage in that a resistance for current limitation must be made. On the other hand, in the AC type plasma display panel, the electrode covers the dielectric layer, so that the current is limited by the formation of a natural capacitance component and the life is longer than that of the DC type because the electrode is protected from the impact of ions during discharge.

1 is a partial perspective view of an AC plasma display panel.

As shown in FIG. 1, the scan electrode 4 and the sustain electrode 5 covered with the dielectric layer 2 and the protective film 3 on the glass substrate 1 are formed in pairs in parallel. On the glass substrate 6, a plurality of address electrodes 8 covered with the insulator layer 7 are formed. The partition 9 is formed on the insulator layer 7 between the address electrodes 8 in parallel with the address electrode 8, and the phosphor 10 is formed on the surface of the insulator layer 7 and on both sides of the partition 9. Is formed. The glass substrates 1 and 6 are disposed to face each other with the discharge space 11 therebetween so that the scan electrode 4, the address electrode 8, the sustain electrode 5, and the address electrode 8 are orthogonal to each other. The discharge space at the intersection of the scan electrode 4 and the sustain electrode 5 paired with the address electrode 8 forms a discharge cell 12.

2 shows an electrode arrangement diagram of the plasma display panel.

As shown in FIG. 2, the electrodes of the plasma display panel are arranged in a matrix of m × n. Specifically, the address electrodes A1 -Am are arranged in the column direction and n rows of scan electrodes in the row direction ( Y1-Yn and sustain electrodes X1-Xn are arranged in a zigzag. The discharge cell 12 of FIG. 2 corresponds to the discharge cell 12 of FIG.

In general, the driving method of the AC plasma display panel includes a reset period, an addressing period, and a sustain period.

The reset period is a period of initializing the state of each cell in order to perform an addressing operation smoothly on the cell. The addressing period is an address voltage for a cell (addressed cell) turned on to select a cell that is turned on and a cell that is not turned on in a panel. It is a period of time to perform the operation of accumulating wall charge by applying a. The sustain period is a period in which a discharge is applied to actually display an image in the addressed cells by applying a sustain pulse.

As shown in FIG. 3, the plasma display panel divides one frame (1TV field) into a plurality of subfields, and time-division control them to implement gray scale. Each subfield consists of the reset period, the addressing period and the sustain period described above. 3 illustrates a case in which one frame is divided into eight subfields to implement 256 gray levels. Each subfield SF1-SF8 consists of a reset period (not shown), an address period A1-A8, and a sustain period S1-S8, and the sustain periods S1-S8 are light emission periods 1T, 2T. , 4T, ..., 128T) becomes 1: 2: 4: 8: 16: 32: 64: 128.

At this time, for example, in order to implement a gray scale of 3, the discharge cell is discharged in the subfield SF1 having the 1T light emission period and the subfield SF2 having the 2T light emission period so that the sum of the discharge periods is 3T. In this manner, 256 grayscale images are displayed by combining subfields having different light emission periods.

On the other hand, there may be a problem in expressing a low gray level in the plasma display panel. As a method for solving the low gray level, a pixel having a low gray level may be expressed as a gray level capable of displaying the gray level, and the error is propagated to surrounding pixels. The error diffusion method is generally applied.

FIG. 4 is a diagram illustrating an error diffusion method generally used in a plasma display panel. FIG. 4A is a block for an error diffusion processing algorithm (Floyd-Steinberg Algorithm), and FIG. 4B is used at this time. It is a figure which shows the kernel (KERNEL).

As shown in (a) of FIG. 4, the error diffusion method calculates an error between a gradation originally intended to be displayed and a gradation that can be actually displayed with respect to an inputted R (Red), G (Green), or B (Blue) video signal. The low gray scale is represented by multiplying and distributing the error by multiplying a constant coefficient to surrounding pixels as shown in (b) of FIG. 4. At this time, in Figure 4 (a) 1D, 1H + 1D, 1H, 1H-1D block is a block indicating the position of the surrounding pixels of the position of the pixel to display the low gray, 7/16, 1/16, 5 / 16 and 3/16 represent coefficients to be multiplied by surrounding pixels. The output of the gray scale propagated around the error is indicated by RGB _q in FIG. As shown in FIG. 4B, the error E ^* is propagated by multiplying a constant coefficient to the surrounding pixels as shown in FIG. 4B.

However, as shown in FIG. 4, the conventional error diffusion method applies the error diffusion processing algorithm to the R, G, and B image signals in the same manner. The emission luminance of the plasma display panel is that of the G (Green) phosphor. Is very high compared to R and B, so it is well recognized visually and causes low gradation to be worse. That is, since the emission luminance of the plasma display panel with respect to the R and B signals is lower than that of the G signal, there is no problem in gray scale expression and visibility, but the G signal has a higher luminance than the R and B signals. As a result, a problem arises that the visual recognition is poor and the low gradation expression is bad.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the above-described problems of the related art, and to provide an image processing method for solving a problem of low gray scale expression caused by high emission luminance of a G phosphor in an image display apparatus.

According to a feature of the present invention for achieving the above object, there is provided an image processing method in a video display device. The image processing method includes: (a) processing an image by using a half-toning technique having a pattern having the same pattern for each frame of a first color image signal among input image signals; And b) processing the second color image signal among the input image signals by using a half-toning technique having a pattern having a different shape for at least one frame. In this case, the second color image signal may be an image signal having the highest light emission luminance to be displayed on the image display device. In addition, the half-toning technique in step (a) is an error diffusion method of error diffusion processing using an error diffusion kernel having the same shape for each frame, and the half-toning technique in step (b) is different for at least one frame. Characterized in that it is an error diffusion method of error diffusion processing using a shape error diffusion kernel. The half-toning technique in step (a) is a dithering method for dithering using a dithering matrix of the same type for each frame, and the half-toning technique in step (b) is for dithering a different type for at least one frame. A dithering method is used for dithering using a matrix.

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According to another feature of the present invention, a plasma display panel is provided. The plasma display panel includes a plasma panel including first and second electrodes and a third electrode formed to intersect the first and second electrodes; A driving unit driving the plasma panel; And a control unit which applies a control signal to the driver to divide one frame into a plurality of subfields and to control the number of the subfields forming the one frame and the number of the sustain pulses allocated to each subfield. The controller processes an image by using a half-toning technique having a pattern having the same pattern for each frame for the first color image signal and the second color image signal among the input image signals, and at least for the third color image signal among the input image signals. An image may be processed by using a half-toning technique having a different pattern for each frame. In this case, the third color image signal may be an image signal having the highest light emission luminance emitted in the display on the plasma display panel.

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DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

An image processing method and a plasma display panel using the same according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

5 is a schematic plan view of a plasma display panel according to an embodiment of the present invention.

As shown in FIG. 5, the plasma display panel according to the exemplary embodiment of the present invention includes a plasma panel 100, an address driver 200, a scan / hold driver 300, and a controller 400.

The plasma panel 100 includes a plurality of address electrodes A1-Am arranged in the column direction, and a plurality of scan electrodes Y1-Yn and sustain electrodes X1-Xn arranged in a zigzag pattern in the row direction. . The address driver 200 receives an address drive control signal from the controller 400 and applies a display data signal for selecting a discharge cell to be displayed to each address electrode A1-Am. The scan and sustain driver 300 receives a control signal from the controller 400 and alternately inputs a sustain voltage to the scan electrodes Y1-Yn and the sustain electrodes X1-Xn to perform sustain discharge for the selected discharge cell. do.

The controller 400 receives R, G, and B image signals and a synchronization signal from the outside, divides one frame into several subfields, and divides each subfield into a reset period, an address period, and a sustain discharge period to drive the plasma display panel. do. At this time, the controller 400 adjusts the number of sustain pulses in each sustain period of the subfield in one frame and supplies the necessary control signals to the address driver 200 and the scan sustain driver 300.

Hereinafter, an error diffusion unit (not shown in FIG. 5) which propagates an error to surrounding pixels in order to improve the low gray scale expression power of an input image signal in the controller 400 according to an exemplary embodiment of the present invention with reference to FIGS. 6 and 7. Let's take a closer look at the error diffusion method that Um) performs.

 FIG. 6 is a diagram illustrating a kernel (KERNEL) used for each frame for R and B video signals in an error diffusion method according to an exemplary embodiment of the present invention.

As shown in Fig. 6, the kernels used for the error diffusion processing for each frame among the input video signals R (Red) and B (Blue) are not changed, and the error diffusion processing is performed using the same kernel. That is, the error diffusion process is performed by using the same kernel by fixing the coefficients used for propagating to the surrounding pixels with respect to the error E ^* for the R and B video signals. Since the luminance of the plasma display panel for the R and B image signals is very low compared to the luminance of the luminance for the G (Green) image signal, there is no problem in gradation expression and visibility even if the error diffusion processing is performed using the same kernel. Because.

In this case, the types of kernels used by fixing the R and B video signals by frame are different from those shown above and the kernels used in the error diffusion by the Fan coefficient in addition to the kernel used in the error diffusion by the Floyd-Steinberg coefficient. It will be apparent to those skilled in the art that the variations can be made.

7 is a diagram illustrating a kernel KERNEL used for each frame for a G (Green) video signal in the error diffusion method according to an embodiment of the present invention.

As shown in FIG. 7, the shape of the kernel used for each frame is continuously changed with respect to the G (Green) video signal, and error diffusion processing is performed using a kernel having a different form for each frame. That is, the G (Green) video signal is subjected to error diffusion processing using a different type of kernel by varying the coefficient used to propagate the error E ^* to the surrounding pixels for each frame. In FIG. 7, the kernel internal values are changed with a periodicity in units of 4 frames in the kernel used for each frame, but a randomly varying method may be used.

As the error propagates to surrounding pixels, the error is multiplied by a constant coefficient, and the coefficient value varies according to the position of the surrounding pixel. The positions of these coefficients are periodically changed or randomly (as shown in FIG. 7). RANDOM) to fluctuate. For example, as shown in FIG. 7, the Floyd-Steinberg coefficient is 3/16, 5/16, 1 / in frame 2 in the form of 7/16, 3/16, 5/16, 1/16 in frame 1 16, 7/16, 5/16, 1/16, 7/16, 3/16 in frame 3, 1/16, 7/16, 3/16, 5/16 in frame 4, frame 5 From the beginning, the process is repeated periodically as in the case of Frame 1. In this case, a method of randomly changing the internal value of the kernel for each frame (RANDOM) without periodically repeating may be used.

As described above, when the error diffusion kernel is changed for each frame of the G (Green) image signal, an effect of preventing and dispersing the image signal processed by the error diffusion from being continuously displayed at the same position on the pixel of the plasma display panel is generated. do. Therefore, the G cells are prevented from being emitted continuously in the same pixel and are dispersed in adjacent G cells, thereby reducing the emission luminance of the G cells by distributing the positions of the light emitting pixels of the G cells frame by frame. That effect occurs. As a result, an effect of improving the low gradation power problem caused by the high luminance of the G phosphor is generated.

In this case, the type of kernel used in the G video signal and fluctuating according to the frame is different from the kernel used in the error diffusion by the Fan coefficient in addition to the kernel used in the error diffusion through the Floyd-Steinberg coefficient. It will be apparent to one skilled in the art.

In addition, since the G (Green) light emission luminance of the plasma display panel is much higher than that of R (Red) and B (Blue), the shape of the error diffusion kernel is varied for each G (Green) video signal by changing the shape of the G cell. Although the emission luminance is reduced, if the emission luminance of R (Red) and B (Blue) is high, the error diffusion kernel can be changed frame by frame in the same manner as the above method for the G image signal.

In addition, there are various halftoning techniques as a method of dispersing the emission luminance of the G image signal through the error diffusion method as described above, and the error diffusion method is a kind of such halftoning technique. Another halftoning technique is a dithering method, and it is apparent to those skilled in the art that the dithering method can be applied to the dithering method in the same manner as described above. 8A and 8B are diagrams showing examples of a 2 × 2 dither matrix used in applying a dithering method. The dithering matrix is varied from frame to frame for a G video signal according to the embodiment of the present invention. The error diffusion method can be effective. In other words, the R and B video signals are represented using the same dithering matrix for each frame, and the low gray scales are represented by varying the dithering matrix for each G video signal. Here, a method of applying a dithering method using a dither matrix is easily applicable by those skilled in the art, and thus, a detailed description thereof will be omitted. At this time, the variation of the dithering matrix for each frame of the G video signal may be repeatedly changed with a certain period. Here, the dither matrix shown in FIG. 8 is an example, and it is apparent to those skilled in the art that the value of the dither matrix may vary.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, according to the present invention, by varying the shape of the error diffusion kernel for each frame in applying the error diffusion to the G video signal having high emission luminance or changing the dither matrix for each frame in applying the dithering, The position of the light emitting pixels of the cells may be dispersed for each frame to reduce the average luminance of the G cells. Accordingly, there is a unique effect of reducing the visibility of light emission of the G cell generated when displaying low gray scale by reducing the average light emission luminance of the G cell, thereby improving the low gray scale expressive power.

Claims (11)

In the image processing method in a video display device, (a) processing an image using a half-toning technique having a pattern having the same pattern for each frame with respect to the first color image signal among the input image signals; And and (b) processing an image by using a half-toning technique having a pattern having a different pattern for at least one frame for the second color image signal among the input image signals. The method of claim 1, And the second color image signal is an image signal having the highest light emission luminance emitted when the second color image signal is displayed on the image display device. The method according to claim 1 or 2, And performing image processing on the third color image signal among the input image signals using a half-toning technique having the same pattern for each frame. And the second color image signal is a green image signal. The method according to claim 1 or 2, The half-toning technique in step (a) is an error diffusion method of error diffusion processing using an error diffusion kernel of the same type for each frame, and the half-toning technique in step (b) has a different form for each of at least one frame. An error diffusion method of error diffusion processing using an error diffusion kernel. The method according to claim 1 or 2, The half-toning technique in step (a) is a dithering method for dithering using the same dithering matrix for each frame, and the half-toning technique in step (b) uses a dithering matrix of different types for at least one frame. And a dithering method for dithering using the image processing method. The method of claim 4, wherein The error diffusion kernel applied to the second color image signal in the step (b) is changed to a different form every frame. The method of claim 4, wherein The error diffusion kernel applied to the second color image signal in the step (b) is changed to a different form in a predetermined frame unit. The method of claim 7, wherein And a value of an error diffusion kernel applied to the second color image signal having a periodicity in a predetermined frame unit. The method of claim 6, And a value of an error diffusion kernel applied to the second color image signal has a random characteristic every frame unit and is changed. A plasma panel including first and second electrodes and a third electrode formed to intersect the first and second electrodes; A driving unit driving the plasma panel; And And a control unit which applies a control signal to the driver to divide one frame into a plurality of subfields and to control the number of the subfields forming the one frame and the number of the sustain pulses allocated to each subfield, The controller processes an image using a half-toning technique having a pattern having the same pattern for each frame for the first color image signal and the second color image signal among the input image signals, and for the third color image signal among the input image signals. And a half-toning technique having a different pattern for each of the at least one frame. The method of claim 10, And the third color image signal is an image signal having the highest light emission luminance emitted when the third color image signal is displayed on the plasma display panel.

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