KR100578918B1 - A driving apparatus of plasma display panel and a method for processing pictures on plasma display panel - Google Patents

Abstract

The present invention relates to a driving apparatus for a plasma display panel capable of reducing pseudo contours and high speed operation, and an image processing method for a plasma display panel. First, each frame of the input video signal is separated into at least two independent subframes. Thereafter, the gradation values and subfield emission patterns of the at least two independent subframes separated from the previously inputted independent subframes are compared to determine pseudo contours for each subframe, and accordingly, predetermined gradations The gray level conversion is changed in correspondence with the group. At this time, the test image is displayed in advance for each gray level, and the thermal average gray level is calculated through simulation to classify each gray level into a plurality of gray level groups according to the degree of pseudo contour generation. In addition, an error spread is applied to each of at least two independent subframes using the grayscale transformed result, and each of them applies an error spread by partially mixing the propagated errors. As a result, pseudo contours can be reduced more precisely, and a high-speed error diffusion process and a high frequency component are improved on a large number of pixels in a high resolution image display device, thereby providing an image having improved image quality.

PDP, Error Diffusion, Pseudo Contour, Thermal Average Gradation, even, odd

Description

A driving apparatus of a plasma display panel and an image processing method of a plasma display panel {A DRIVING APPARATUS OF PLASMA DISPLAY PANEL AND A METHOD FOR PROCESSING PICTURES ON PLASMA DISPLAY PANEL}

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

2 is a diagram illustrating an example in which a pseudo contour occurs.

3 is a diagram illustrating an example in which a conventional error diffusion method for inverse gamma correction is applied to driving a plasma display panel.

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

5 is a schematic block diagram of a controller of a plasma display panel according to an exemplary embodiment of the present invention.

FIG. 6 is a diagram showing the configuration of two frame data shown in FIG. 5, wherein (a) is a frame data configuration input to an A / D converter, and (b) and (c) are output from an A / D converter. It consists of two frame data.

FIG. 7 is a diagram illustrating an example of a pattern in which a moving image pseudo contour may occur. FIG. 7A illustrates a pseudo contour amount when a light emission pattern having a weight of 64 is different, and FIG. Pseudocontour amounts are shown when the light emission patterns are different.

8 is a diagram illustrating a screen floating on the plasma display panel in order to evaluate the possibility of pseudo contour.

FIG. 9 is a diagram illustrating an average gray level calculated for each column when a test image as shown in FIG. 8 is displayed.

FIG. 10A is a diagram illustrating a column average gray scale when no pseudo contour is generated, and FIG. 10B is a diagram illustrating a column average gray scale when a pseudo outline is generated.

FIG. 11 is a diagram illustrating light emission patterns of 63 and 64 gray levels in an example of the subfield arrangement.

FIG. 12 is a diagram illustrating a thermal average gray scale calculated in the gray scale and the light emission pattern of FIG. 11.

13 shows an example of a lookup table included in the gradation group unit.

14 is a view showing the shape of the Floyd-Steinberg coefficient, which is a general error diffusion coefficient.

15 is a diagram illustrating an error propagation process of each subframe by applying Floyd-Steinberg coefficient, (a) for even pixel frame, (b) for odd pixel frame, and (c) overall error It is about the radio wave processing process.

16 shows an 8-bit test image.

FIG. 17 illustrates a resultant image after the independent error propagation process illustrated in FIG. 15 is applied.

18 is a diagram in which a mixed error propagation process according to an embodiment of the present invention is applied by Floyd-Steinberg coefficient.

FIG. 19 illustrates a resultant image after the mixed error propagation process illustrated in FIG. 18 is applied.

20 is a view showing the shape of the FAN coefficient which is a general error diffusion coefficient.

21 is a diagram in which an independent error propagation process is applied by FAN coefficients, (a) is for even pixel frames, (b) is for odd pixel frames, and (c) is for overall error propagation processing. .

22 is a diagram illustrating a mixed error propagation process applied by a FAN coefficient according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus for a plasma display panel (PDP) and an image processing method for a plasma display panel, and more particularly, to an apparatus for driving a plasma display panel capable of reducing pseudo contours and high speed operation, and an image processing for a plasma display panel. It is about a method.

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 plasma display panel, since the electrode covers the dielectric layer, the current is limited by the formation of a natural capacitance component, and the electrode is protected from the impact of ions during discharge.

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. 1, the plasma display panel divides one frame (1TV field) into a plurality of subfields and controls the time division to implement grayscale. Each subfield consists of the reset period, the addressing period and the sustain period described above. 1 illustrates a case where 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.

However, pseudo contours occur due to human visual characteristics when displaying moving images by the subfield method as described above. 2 is a diagram illustrating an example in which a pseudo contour occurs in detail. When the image having the gradation 127 and the gradation 128 side by side moves at a speed of 1 to the right may be represented as shown in FIG. 2 by the subfield arrangement as shown in FIG. 1. At this time, the human vision causes the gray level to be recognized in the direction of the arrow as shown in FIG. Therefore, there is a problem that pseudo contour such as gradation 255 occurs between gradation 127 and gradation 128.

In addition, an error diffusion method is used to compensate for the small number of gradations that can be displayed compared to the number of gradations to be displayed in various image display devices such as a plasma display panel (PDP), a liquid crystal display (LCD), and an organic electroluminescence (EL). This is mainly used. In particular, in the PDP, an error diffusion method is widely used for inverse gamma correction or pseudo contour reduction. Such an error diffusion method is a method of displaying an gray scale to be expressed on an average within a predetermined area by propagating an error generated between a gray scale that can be expressed in an image display and a gray scale to be expressed to surrounding pixels.

Conventional error diffusion methods include Korean Patent Laid-Open Publication No. 2002-18900, "Gamma Correction Apparatus and Method in Plasma Display Panel."

3 is a diagram illustrating an example in which a conventional error diffusion method for inverse gamma correction is applied to driving a plasma display panel.

As shown in FIG. 3, in the conventional plasma display, when an analog video signal is input 10, an n-bit signal (A / D (Analog / Digital) conversion 20) converts the analog signal into a digital signal. 30) and output. At this time, since the A / D-converted output is output by one pixel, the pixel output frequency is 60 × n × m (Hz) in the NTSC (National Television Standard Committee) method of 60 Hz. The size of the output frame is horizontal x vertical = n x m.

As described above, the A / D converted signal is subjected to the inverse gamma correction 40 to compensate for the gamma correction performed for display in the cathode ray tube (CRT). Thereafter, the inverse gamma corrected signal is output 60 to the PDP, and displayed as a corresponding image by applying a conventional error diffusion 50 to correct the gradation lost when converted to the gradable representation in the PDP.

On the other hand, in recent years, the resolution of an image display device has increased in order to display a high quality image, and the number of frames to be displayed per second has increased. As described above, while the number of pixels to be processed in a limited time increases due to the development of the image display device, the conventional error diffusion method has a problem in that real-time error diffusion processing is difficult because the error diffusion is processed by one pixel.

Therefore, in the case of a high quality image display device, as the number of pixels to be processed in a limited time increases, an error diffusion method for high speed operation is required.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the above problems of the related art, and to provide a driving apparatus for a plasma display panel and an image processing method for a plasma display panel capable of reducing pseudo contours and operating at high speed.

A driving apparatus of a plasma display panel according to a feature of the present invention for achieving the above object is

An analog / digital converter for dividing each frame of the input analog video signal into at least two independent first and second subframes and converting the frame into a digital video signal;

Pseudo contouring is generated by comparing the gray level values of the first and second subframes currently output from the analog / digital converter and the light emission patterns of the subfields and the gray level values of the first and second subframes previously output. A pseudo contour detector for determining a degree;

The gray level of the first and second sub-frame image signals is determined for each of a plurality of gray level groups in advance according to the degree of pseudo contour generation of the video signal for each of the first and second sub-frames determined by the pseudo contour detecting unit, respectively. A gradation group unit for converting differently;

And an error diffusion unit for differently diffusing the difference between the gray level of the image signal output from the gray level group unit and the input video signal gray level of the first and second sub-frames for each gray level group.

The image processing method of the plasma display panel according to another aspect of the present invention

An image of the plasma display panel which displays an image corresponding to the image signal by dividing an image of each field displayed on the plasma display panel in response to an input image signal into a plurality of subfields, and displaying a gray scale according to the combination of the subfields. In the processing method,

(a) dividing each frame of the input video signal into at least two independent first and second subframes;

(b) The gray level values and subs of the first and second subframes separated in the step (a) with respect to the currently input video signal and the first and second subframes separated from the previously input video signal. Comparing the light emission patterns of the fields for each of the partial frames to determine a pseudo contour occurrence degree;

(c) According to the degree of pseudo contour generation of the video signal for each of the first and second sub-frames determined in step (b), the first and second sub-frame video signals may be Converting the gray levels differently; And

(d) error diffusing the difference between the gray levels of the image signals converted in the step (c) and the gray levels of the first and second sub-frame image signals separated in the step (a) differently for each of the gray level groups; Include.

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.

A driving apparatus of a plasma display panel and an image processing method of the plasma display panel according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

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

As shown in FIG. 4, the plasma display panel according to the exemplary embodiment of the present invention includes a plasma panel 100, an address driver 200, a scan / sustain 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 / hold 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. .

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, the controller 400 according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 5 to 22.

5 is a schematic block diagram of a controller 400 of a plasma display panel according to an exemplary embodiment of the present invention.

As shown in FIG. 5, the control unit of the plasma display panel according to the embodiment of the present invention includes an A / D converter 410, first and second pseudo contour detection units 420 and 422, and first and second frame memory units. 430, 432, first and second gray level group units 440 and 442, first and second error diffusion units 450 and 452, and first and second subfield generators 460 and 462. do.

The A / D converter 410 converts an input analog video signal into a digital video signal and outputs the same, but simultaneously converts two consecutive pixels simultaneously when converting the digital video signal. Therefore, when the video signal corresponding to one frame is converted and output by the A / D converter 410, two independent frame data (frame 1 and frame 2) having half the size of one frame are formed. At this time, the size of each frame 1 and frame 2 is horizontal x vertical = n / 2 x m.

As described above, since two consecutive pixels are simultaneously output from the A / D converter 410, the pixel frequency is 60 × (1/2) × n × m in the NTSC system of 60 Hz, which is 1/2 of the conventional processing frequency. This decreases to facilitate the real-time calculation.

FIG. 6 is a diagram showing the configuration of two frame data (frame 1 and frame 2) shown in FIG. 5, (a) is a frame data configuration input to the A / D converter 410, (b) and (c) shows two frame data configurations output from the A / D converter 410.

As shown in FIG. 6, when two consecutive pixels in the entire frame data input to the A / D converter 410 are represented as E (Even) pixels and O (Odd) pixels, the A / D converter 410 is shown. The two frame data formed by simultaneously outputting two consecutive pixels through the even pixel frame (frame 1), which is a set of E pixels in even columns, and odd (odd), which is a set of O pixels in odd columns, are formed. It is formed independently of the pixel frame (frame 2).

The input image signal of one frame formed as described above is divided into an even (even) pixel frame (frame 1) and an odd (odd) pixel frame (frame 2) to independently perform pseudo contour detection process, gray level conversion, and error diffusion method calculation. This will be described in detail below.

The first and second pseudo contour detectors 420 and 422 are two frames independently formed by the A / D converter 410 (that is, frame 1 and frame 2) and previously inputted to the A / D converter 410. Video pseudo contour information is detected by using two frames independently formed by. At this time, the image data of the previous frame should be stored in order to compare the image of the current frame and the previous frame by using the image data of two frames which are continuously input. The first and second frame memory units 430, 432 stores the previous two frame data (meaning frame 1 and frame 2) each independently formed by A / D converter 410. That is, the first frame memory unit 430 stores previous even pixel frame data, and the second frame memory unit 432 stores previous odd pixel frame data.

 At this time, the first and second pseudo contour detection units 420 and 422 detect the video pseudo contour information using the two frames (that is, frame 1 and frame 2) independently formed, respectively. The detection method is the same and will be described below.

Pseudo contours are more likely to occur when the gray level values of two consecutive frames are similar and the light emission patterns of the subfields, that is, the shape of coding distribution are different. In addition, as the subfield weights having different light emission from each other increase, the likelihood of generating a pseudo pseudo contour increases. FIG. 7 is a diagram illustrating an example of a pattern in which a moving image pseudo contour may occur. FIG. 7A illustrates a pseudo contour amount when a light emission pattern having a weight of 64 is different, and FIG. In the case where the light emission pattern is different, the pseudo outline amount is shown. That is, in FIG. 7A, a pseudo contour amount generated when the gray level of the previous frame is 63 and the gray level of the current frame is 64, and FIG. 7B shows the gray level of the previous frame to 127 and the current frame gray to In the case of 128, the pseudo contour generated. In FIGS. 7A and 7B, the peak amounts of the graphs indicate pseudo contours, and as shown in (B) of FIG. 7, larger pseudo contours occur when the light emission pattern having a weight of 128 is different. do.

By using the same principle as described above, the first and second pseudo contour detection units 420 and 422 detect the degree of generating the pseudo pseudo contour, respectively. That is, the first and second pseudo contour detection units 420 and 422 compare light emission patterns with respect to gray levels of pixels of the current frame at the same position as the pixels of the previous frame, respectively. It is determined that a lot occurs.

In the same principle as above, the first and second pseudo contour detection units 420 and 422 determine a pseudo contour, and a more detailed method will be described below. Equation 1 shows a method of calculating the pseudo contour degree in an arbitrary pixel.

In Equation 1, i _n (x, y) is a gray scale value at the position (x, y) of the current frame image data, and i _n-1 (x, y) is a gray scale at the previous frame (x, y) position. Indicates a value. B _in (p) and B _in-1 represent light emission pattern information of the p-th subfield for i _n (x, y) and i _n-1 (x, y) as 0 and 1, respectively. SP (p) represents the weight of the p-th subfield, and m represents the number of subfields. At this time, even the system of the previous frame and the current frame (that is, the value corresponding to the absolute value of i _n (x, y) -i _n-1 (x, y)) was subtracted as in Equation 1, which is pseudo contour Since this amount increases as the system of the previous frame and the current frame is smaller, the system is subtracted as described above.

In addition, weight [i _n (x, y)] represents weight for each gray level determined according to the current gray level value. In general, human vision is more sensitive to differences in luminance in dark areas. That is, even in the same pseudo contour generation amount, the pseudo contour in the dark area is more troublesome than the pseudo contour in the bright area. Therefore, in order to take this into account, the predetermined weight-weight weight [i _n (x, y)] for each gray level is multiplied as in Equation (1). At this time, the weight for each gray level is set to a larger value in the darker gray level in advance.

Since Equation 1 represents the degree of pseudo contour for each pixel, the final degree of pseudo contour is expressed by Equation 2 below.

In Equation 2, N represents the number of scan lines of the plasma display panel and M represents the number of address lines. Therefore, the pseudo contour degree of the entire screen of the plasma display panel can be calculated by Equation 2.

The first and second gray level group units 440 and 442 evaluate the possibility of pseudo contour generation through pseudo contour simulation for each gray level before configuring the system as shown in FIG. The gray level of the input image signal is differently converted for each gray level group according to information on whether or not the pseudo contour is generated by the first and second pseudo contour detection units 420 and 422, respectively.

First, a method of classifying gradation groups by a simulation method for evaluating the likelihood of generating pseudo contours will be described.

8 is a screen floating on the plasma display panel to evaluate the possibility of pseudo contour. In FIG. 8, the left and right quadrangles have the same gray level. FIG. 9 is a diagram illustrating an average gray level calculated for each column when a test image as shown in FIG. 8 is displayed. As shown in FIG. 9, it can be seen that the heat average gradations of the left quadrangle portion and the right quadrangle portion are separated from each other.

Here, the simulation result image is calculated through the simulation of moving to the right as described in FIG. In this case, a pseudo contour may or may not occur according to the grayscale and subfield arrangement of the test image as shown in FIG. 8. FIG. 10A is a diagram illustrating a column average gray scale when no pseudo contour is generated, and FIG. 10B is a diagram illustrating a column average gray scale when a pseudo outline is generated. If the pseudo contour does not occur, the thermal mean gray scale of the simulation result has the heat average gray scale value as shown in FIG. 10A, and if the pseudo contour occurs, the gray scale outside the range of the gray scale values of the original image will occur as shown in FIG. 10B.

Using the simulation result of the test image shown in FIGS. 8 to 10, the degree of pseudo contour of the test image is represented by FC (P, Q), and the degree of pseudo contour is evaluated through the process of Equation 3 below.

In Equation 3, P and Q represent left and right gray scales of the test image as shown in FIG. 8, and Max_FC and Min_FC represent maximum and minimum values in the column average gray scale of the simulated image. Also, max (P, Q) means the higher value among P and Q, and min (P, Q) means the lower value among P and Q. That is, by applying the simulation result shown through the process shown in Figs. 8 to 10 to the above equation (3) to evaluate the degree of deviation outside the range of the original tone P, Q to determine the pseudo contour amount.

For example, suppose that the emission pattern is the same as that of FIG. 11 when the subfield arrangement is [1 2 4 8 16 32 42 44 52 54] and P = 63 and Q = 64. In this case, the heat average gray value obtained through the simulation is calculated as shown in FIG. 12. At this time, max (P, Q) = 64, min (P, Q) = 63, and as shown in FIG. 12, Max_FC = 71 and Min_FC = 63. Therefore, in Equation 3, FC (P, Q) = Max_FC−max (P, Q) = 71-64 = 7. In another example, when P = 100 and Q = 101, the simulation result shows that Max_FC = 101 and Min_FC = 100, so that max (P, Q) = 101 and min (P, Q) = 100, As shown, FC (P, Q) = 0, which indicates that pseudo contour does not occur.

In the same manner as described above, the evaluation of the pseudo contour degree through the simulation (FIGs. 8 to 10) and Equation 3 takes into consideration both the 256 gray level for P and the 256 gray level for Q. Calculate P, Q). With the FC (P, Q) calculated for all 256x256 cases, the pseudo contour probability for each gray level is calculated by the following equation (4).

 In Equation 4, x represents an arbitrary gray scale, and the pseudo contour contour possibility for the gray scale x is evaluated for all cases in which FC (P, Q) is added to a case having gray scale x of P or Q. When the probability of generating pseudo contours for each gray level is calculated for 256 gray levels according to Equation 4, the gray level is classified into several gray groups according to the value. For example, when dividing into three groups, it can be classified by the conditions satisfied in the following equation (5).

All gray levels x satisfying Equation 5 may be classified into three gray level groups. The gray level group to be classified here is not necessarily three groups, and can be classified into three or more groups for more precise pseudo contour reduction. In the above Equation 5, the gray level group 1 is smaller than the maximum value of the pseudo contour, so all grays are satisfied, resulting in 256 grays. In the case of gradation group 2, the gradation means the gradation other than the gradation having a large pseudo outline. In the case of gradation group 3, the pseudo gradation is the remaining gradation excluding a small amount of gradation. That is, the gradation group 3 is less likely to generate pseudo contours than the gradation group 2. In the number of gray levels, gray level group 3 generally has a smaller number than gray level group 2.

Here, as shown above, each grayscale is classified into a plurality of grayscale groups, and the first and second grayscale group units 440 and 442 respectively modify the grayscale to reduce pseudo contours for each grayscale group. Each has a lookup table. That is, the first gradation group unit 440 includes gradation group units 1, 2, and 3, and deforms the input gradation for each gradation group unit 1, 2, 3 through the gradation group determined based on the simulation result as described above. Have a lookup table differently. In addition, the second grayscale group unit 442 also has grayscale group units 1 ', 2' and 3 'and has a lookup table for modifying the input grayscale through the grayscale group determined based on the simulation result as described above. In this case, the gradation group units 1 ′, 2 ′, and 3 ′ have the same lookup tables as the gradation group units 1 ′, 2 ′, and 3 of the first gradation group unit 400, respectively. That is, the first and second gray level group units 440 and 442 respectively adjust the gray level of the even (even) pixel (pixel) frame data (frame 1) and the odd (odd) pixel (pixel) frame data (frame 2). The functions and methods are identical to each other except that the video pseudo contours (that is, the pseudo contours detected by the first and second pseudo contour detectors 420 and 422, respectively) are modified.

13 shows an example of a lookup table included in the gradation group unit 3 or the gradation group unit 3 '. As shown in Fig. 13, the lookup table is configured such that an input has 150 and an output of 149 for 151. Since 150 and 151 do not belong to the gradation group 3, the output corresponds to the gradation group 3 and is output as 149 close to the input 150 and 151. Thus, the gray level group 1, 2, 3 and the gray level group 1 ', 2', and 3 'each have different lookup tables with output grayscale values for reducing pseudo contours for each gray level group, thereby converting the input gray levels. .

That is, when there is almost no pseudo contour based on the result of detecting the pseudo contour occurrence degree of the even (even) pixel (pixel) frame data (frame 1) image signal by the first pseudo contour detector 420, the gray level group The gradation is converted using gradation 1, and when gradation occurs a lot, the gradation group 3 is used to convert gradation. In the medium level, the gray level group unit 2 is used to convert the gray levels. In this case, the gradation group units 1, 2, and 3 have a look-up table having deformation values for each gradation according to the pseudo contour possibility according to the values calculated through the simulation results described above, and through this, the gradation is converted to a pseudo contour. Reduce.

In addition, when the pseudo contour is generated by the second pseudo contour detection unit 422, the pseudo contour generation degree of the odd (odd) pixel (pixel) frame data (frame 2) image signal is almost absent. The gray scale is converted using the subsection 1 ', and when a large number of pseudo contours occur, the gray scale group unit 3' is used to convert the gray scale. In the medium level, the gray level group portion 2 'is used to convert the gray levels. In this case, the gradation group units 1 ', 2', and 3 'have a look-up table having a deformation value for each gradation according to the pseudo contour possibility according to the value calculated through the simulation result described above, thereby converting the gradation. Reduce pseudo contours.

At this time, the output gray level values of the first and second gray level group units 440 and 442 generate an input gray level and an error value, respectively. In addition, the error value depends on the gray level group parts 1, 2 and 3 and the gray level group parts 1 ', 2', and 3 'included in the first and second gray level group parts 440 and 442, respectively. In order to compensate for the error value, as illustrated in FIG. 5, the first and second error diffusion units 440 exist. In addition, as shown in FIG. 5, the first error diffusion unit 450 includes error diffusion units 1, 2, and 3 to compensate for errors in the gray level values output from the gray level group units 1, 2, and 3, respectively. The second error diffusion unit 452 also includes error diffusion units 1 ', 2', and 3 'to compensate for errors in the gray scale values output from the gray level groups 1', 2 ', and 3', respectively. In this case, when the gradation group is classified into three or more, the number of the error diffusion units also changes accordingly.

Hereinafter, an error diffusion method performed by the first and second error diffusion units 450 and 452 will be described in detail. The error diffusion method described below includes error diffusion parts 1, 2 and 3 included in the first error diffusion part 450 and error diffusion parts 1 ', 2' and 3 'included in the second error diffusion part 452. The error diffusion methods performed by the respective methods are as follows. However, according to the degree of pseudo contour detected by the first and second pseudo contour detectors 420 and 422, each gray level group part (i.e., one of the gray level group parts 1, 2, 3, gray level group parts 1 ', 2'). And an error diffusion unit (that is, one of the error diffusion units 1, 2, 3, and one of the error diffusion units 1 ', 2', and 3 ') that are operated according to the gradation group unit operated among one of the 3' and 3 '.

Meanwhile, the first and second error diffusion units 450 and 452 may each include two frame data independently formed by the first and second gray level group units 440 and 442 (that is, the first and second gray level group units, respectively). Error diffusion methods are applied to the data output from 440 and 442, and the image quality is affected by the error diffusion coefficients. In the error diffusion method, an error between gray levels is propagated to surrounding pixels. In this case, the error is divided and propagated by a predetermined weight at a predetermined position when propagating to surrounding pixels. This weight is called the error diffusion coefficient, and the well-known error diffusion coefficient is a Floyd-Steinberg coefficient. The shape of this Floyd-Steinberg coefficient is shown in FIG.

Referring to FIG. 14, a process of separating one frame into even pixel frames and odd pixel frames, which are partial frames, and independently processing the frames (for example, an error propagation process of each partial frame by applying a Floyd-Steinberg coefficient 15 (a) and 15 (b), and FIG. 15 (c) shows a shape displayed on one frame in which error propagation processes applied to two frames are later summed.

As illustrated in FIGS. 15A and 15B, an error propagated to one pixel in each of two frames may be represented by Equations 6 and 7 below.

,

는 각각 even 화소 프레임과 odd 화소 프레임에서 (x,y) 화소의 처리시 전파되는 오차의 합을 나타낸다.here

,

Denotes the sum of errors propagated during processing of (x, y) pixels in the even pixel frame and the odd pixel frame, respectively.

On the other hand, referring to Figure 15 (c), by processing the error for each of the separated frames, the result of the pixel from which the error is propagated for each pixel when viewed in one frame image is generated. FIG. 17 is a diagram illustrating a case where an independent error diffusion method is applied by configuring two independent frames as shown in FIG. 5 when the 8-bit image illustrated in FIG. 16 is input. As shown in FIG. 17, when an independent error diffusion method is applied to two consecutive pixels, a pixel having an error propagating distance from each pixel becomes farther away, resulting in a decrease in spatial frequency, resulting in a high frequency component of the image. There is a disadvantage in that a lot of lost images are displayed.

In order to overcome the above disadvantages, the embodiment of the present invention applies a mixed error propagation method as shown in FIG. 18 so that the propagation of the error is partially mixed between the even pixel frame and the odd pixel frame. That is, in FIG. 15C, error propagation in the even pixel frame is performed only between even pixels, and error propagation in the odd pixel frame is performed only between odd pixels. It is not only made between even pixels during propagation but also mixed with partial errors from adjacent odd pixels, and similarly, it is not only made between odd pixels when propagating errors in odd pixel frames but also partially errors from adjacent even pixels. Use it. At this time, the pixel propagating the mixed error is located in a line higher than the pixel to which the propagated error is applied and is an adjacent pixel.

The mixed error propagation method illustrated in FIG. 18 may be represented by the following Equations 8 to 15.

는 even 화소 프레임의 (x,y)번째 입력 화소이고,

는 odd 화소 프레임의 (x,y)번째 입력 화소이며,

는 오차 전파된 even 화소 프레임의 (x,y)번째 입력 화소이고,

는 오차 전파된 odd 화소 프레임의 (x,y)번째 입력 화소이며,

는 even 화소 프레임의 (x,y)번째 화소에 전파된 오차이고,

는 odd 화소 프레임의 (x,y)번째 화소에 전파된 오차이며,

는 even 화소 프레임의 (x,y) 화소에서 발생한 오차이고,

는 odd 화소 프레임의 (x,y) 화소에서 발생한 오차이며,

는 even 화소 프레임의 (x,y) 화소 출력 계조이고,

는 odd 화소 프레임의 (x,y) 화소 출력 계조이며,

는 비트수 감소된 출력 계조 결정 함수이다.here,

Is the (x, y) th input pixel of the even pixel frame,

Is the (x, y) th input pixel of the odd pixel frame,

Is the (x, y) th input pixel of the evenly propagated even pixel frame,

Is the (x, y) th input pixel of the error propagated odd pixel frame,

Is an error propagated to the (x, y) th pixel of the even pixel frame,

Is an error propagated to the (x, y) th pixel of the odd pixel frame,

Is an error in (x, y) pixels of the even pixel frame,

Is an error in (x, y) pixels of odd pixel frame,

Is the (x, y) pixel output gradation of an even pixel frame,

Is the (x, y) pixel output gradation of the odd pixel frame,

Is a bit reduced output gray scale determination function.

As described above, when the 2-bit output image is calculated for the 8-bit image of FIG. 16 according to the mixed error propagation method according to Equations 8 to 15, the resultant image as shown in FIG. 19 is obtained. . The resultant image of FIG. 19 may provide an improved image quality while expressing a smoother image than the image of FIG. 17 shown by an independent error propagation method.

On the other hand, [Equation 8] to [Equation 15] is a mixed error propagation method according to an embodiment of the present invention is applied to the case of Floyd-Steinberg coefficient shown in Figure 14, the technical scope of the present invention The mixed error propagation method according to the embodiment of the present invention may be applied to other types of error diffusion coefficients without being limited thereto. For example, when an independent error propagation method using an even pixel frame and an odd pixel frame according to an embodiment of the present invention is used with respect to the Fan coefficient shown in FIG. 20, FIGS. 21A and 21B are attached. The error propagates as shown in On the other hand, as shown in (c) of FIG. 21, when all independent error propagation is displayed for one frame image, the error propagation region is far from each other, resulting in deterioration of image quality. In order to overcome this, the hybrid error propagation method according to an embodiment of the present invention can be applied to the Fan coefficient, and the error can be propagated as shown in FIG. 22. Such a mixed error propagation process can be represented using the following Equations 16 and 17 instead of Equations 6 and 7 below.

Through the above method, the first and second error diffusion units 450 and 452 perform error diffusion, respectively.

The first subfield generator 460 generates a subfield corresponding to the image signal data output from the first error spreader 450. That is, the subfields are generated by discriminating on / off of each subfield (meaning subfields having different luminance weights) in response to the image signal data that is error-diffused and output by the first error diffusion unit 450. do.

In addition, the second subfield generator 462 generates a subfield corresponding to the image signal data output from the second error spreader 452. That is, the subfields are generated by discriminating on / off of each subfield (meaning subfields having different luminance weights) corresponding to the image signal data that is error-spread by the second error diffusion unit 452 and output. do.

The subfield data output from the first and second subfield generators 460 and 462, respectively, is summed into one frame of data again to be displayed on the plasma display panel, and thus the PDP driver 500, that is, the address driver 200. And the scan / hold driver 300 to be displayed on the plasma display panel 100.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited thereto, and various other changes and modifications are possible.

For example, in the above description, only one frame is divided into an even pixel frame and an odd pixel frame, and only the application of the mixed error diffusion in error diffusion for each is described. However, the technical scope of the present invention is not limited thereto. By dividing into three or more frames, a mixed error spread can be applied when the error spreads for each. In this case, similarly to the error mixing diffusion method illustrated in FIG. 18, the present invention may be applied to a case in which three or more frames are separated by mixing independent errors. It will be easily understood by those skilled in the art.

As described above, according to the present invention, the gradation is classified according to the occurrence of the outline of the contour by simulation, and accordingly, the gradation is adjusted according to the degree of detection of the contour of the input image signal with an optimal lookup table that reduces the pseudo contour. By varying the look-up table to be converted, pseudo contours can be reduced more precisely, and one frame is divided into two or more independent frames, thereby processing high-speed error diffusion to a large number of pixels in a high resolution image display device. Is possible.

In addition, by mixing errors of the even pixel frame and the odd pixel frame during error propagation, the high frequency component may be further improved to provide an image having an improved image quality.

Claims (19)

An analog / digital converter for dividing each frame of the input analog video signal into at least two independent first and second subframes and converting the frame into a digital video signal; Pseudo contouring is generated by comparing the gray level values of the first and second subframes currently output from the analog / digital converter and the light emission patterns of the subfields and the gray level values of the first and second subframes previously output. A pseudo contour detector for determining a degree; The gray level of the first and second sub-frame image signals is determined for each of a plurality of gray level groups in advance according to the degree of pseudo contour generation of the video signal for each of the first and second sub-frames determined by the pseudo contour detecting unit, respectively. A gradation group unit for converting differently; And an error diffusion unit for differently diffusing the difference between the gray level of the image signal output from the gray level group unit and the input image signal gray level of the first and second sub-frames for each gray level group. The method of claim 1, And the error diffusion unit partially spreads the mutually propagated errors for each of the independent first and second subframes, and applies an error diffusion. The method according to claim 1 or 2, The pseudo contour detection unit A first pseudo contour detector for determining a pseudo contour generation degree by comparing a gray level value of the first subframe currently output from the analog / digital converter and a light emission pattern of a subfield; And a second pseudo contour detector which determines a degree of pseudo contour by comparing the gray level value and the subfield emission pattern of the second subframe currently output from the analog / digital converter and the previously output second subframe. Driving device of the plasma display panel. The method of claim 3, The gradation group unit A first to differently convert the gray level of the first subframe video signal for each of a plurality of gray level groups according to the information on the degree of pseudo contour generation of the first subframe video signal determined by the first pseudo contour detector; A gradation group unit; A second for differently converting the gray level of the second subframe video signal for each of a plurality of gray level groups according to the information of the degree of pseudo contour generation of the second subframe video signal determined by the second pseudo contour detector; An apparatus for driving a plasma display panel including a gradation group unit. The method of claim 1, The gradation group in advance has been classified into a plurality of groups corresponding to the degree of pseudo contour generation through simulation of each gradation test image. The method of claim 5, The gradation group unit may have a different lookup table for different gradation conversions for each gradation group, and the lookup table has information for performing gradation conversion according to the degree of pseudo contour generation through the simulation. Driving device. The method of claim 1, And a frame memory unit for storing image signal data of the first and second subframes previously outputted from the first and second subframes currently output from the analog / digital converter. . The method of claim 1, In the at least two independent first and second subframes, the first subframe is an odd frame that is a set of pixels located in odd columns within one frame, and the second subframe is within one frame. And an even subframe, which is a set of pixels located in even columns. The method according to claim 1 or 2, The error diffusion unit A first error diffuser configured to differentiate the difference between the gray level of the image signal of the first subframe output from the gray level group unit and the input image signal gray level of the first subframe for each of the gray level groups; And a second error diffusion unit configured to differentiate a difference between the gray level of the image signal of the second subframe output from the gray level group unit and the input image signal gray level of the second subframe for each of the gray level groups. drive. The method of claim 1, And a subfield generator for generating subfields corresponding to data output by error diffusion in the error diffusion unit. An image of the plasma display panel which displays an image corresponding to the image signal by dividing an image of each field displayed on the plasma display panel in response to an input image signal into a plurality of subfields, and displaying a gray scale according to the combination of the subfields. In the processing method, (a) dividing each frame of the input video signal into at least two independent first and second subframes; (b) The gray level values and subs of the first and second subframes separated in the step (a) with respect to the currently input video signal and the first and second subframes separated from the previously input video signal. Comparing the light emission patterns of the fields for each of the partial frames to determine a pseudo contour occurrence degree; (c) According to the degree of pseudo contour generation of the video signal for each of the first and second sub-frames determined in step (b), the first and second sub-frame video signals may be Converting the gray levels differently; And (d) error diffusing the difference between the gray levels of the image signals converted in the step (c) and the gray levels of the first and second sub-frame image signals separated in the step (a) differently for each of the gray level groups; An image processing method of a plasma display panel comprising. The method of claim 11, Step (b) is The gradation value of the first partial frame separated in the step (a) and the gradation value of the first subframe separated from the previously inputted video signal and the light emission pattern of the subfield for the currently input video signal are determined for each subframe. Determining a degree of pseudo contour by comparing with each other; The gray level value of the second subframe separated in the step (a) and the light emission pattern of the subfield and the light emission pattern of the subfield, respectively, are separated for each of the subframes. And comparing a pseudo contour occurrence degree with a comparison. According to claim 11 or 12 In step (c) Converting the gradation of the first sub-frame video signal differently for each of a plurality of gradation groups in advance according to the degree of pseudo contour generation of the first sub-frame video signal determined in the step (b); And converting the gray level of the second partial frame video signal differently for each of a plurality of gray level groups according to the degree of pseudo contour generation of the second partial frame video signal determined in the step (b). Image processing method of panel. The method of claim 11, The error diffusion in the step (d) is an error diffusion applied by partially mixing the mutually propagated errors for each of the independent first and second subframes. The method according to claim 11 or 14, And the gradation group in advance is classified into a plurality of groups corresponding to the degree of pseudo contour generation through simulation of each gradation test image. The method according to claim 11 or 14, And a lookup table for performing gradation conversion for reducing pseudo contours for each gradation group in the step (c). The method of claim 11, In the at least two independent first and second subframes, the first subframe is an odd frame that is a set of pixels located in odd columns within one frame, and the second subframe is within one frame. And an even subframe, which is a set of pixels located in an even column. The method of claim 11, Step (d) is Error diffusion of the difference between the gray level of the video signal of the first subframe converted in the step (c) and the gray level of the input video signal of the first subframe separated in the step (a) for each gray level group; Differently diffusing the difference between the gray level of the video signal of the second subframe converted in the step (c) and the gray level of the input video signal of the second subframe separated in the step (a) An image processing method of a plasma display panel comprising. The method of claim 11, Converting into subfields corresponding to data output by error diffusion in step (d), respectively; And controlling the image corresponding to the data of the subfield to be displayed on the plasma display panel.

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