KR20040045603A - Image processing device of plasma display panel - Google Patents

Abstract

PURPOSE: An apparatus and a method for processing the image of a plasma display panel are provided to prevent color distortion at the portion at which the gray level is rapidly changed. CONSTITUTION: An apparatus for processing the image of a plasma display panel includes an inverse gamma correction device(310), a first converter(320), a first error diffusion block(330), a second error diffusion block, a third error diffusion block and a second converter(380). The inverse gamma correction device(310) performs the inverse gamma correction by receiving the digital R, G and B signals. The first converter(320) converts the R, G and B signals inverse gamma corrected by the inverse gamma correction device(310) into the luminance signal(Y) and the first color signal(Pb) and the second color signal. The first error diffusion block(330) performs the error diffusion for the luminance signal. The second error diffusion block performs the error diffusion for the first color signal and the third error diffusion block performs the error diffusion for the second color signal. And, the second converter(380) outputs the error diffused illumination signal and the gray level converted R, G and B signals.

Description

Image processing device of plasma display panel and method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display panel (PDP), and more particularly, to an image processing apparatus and method for a PDP for realizing high efficiency and high performance.

As is well known, the PDP has a widely used address display period separated subfield method (ADS). This method is a method of displaying an image by dividing one field into a plurality of subfields each consisting of an address section and a discharge holding section for each line of the PDP screen. Here, the address section is a section for writing data such as lighting or boiling point, and the discharge holding section is a section for emitting predetermined pixels at one time.

In order to express the input TV signal in the plasma display, the signal must be corrected through inverse gamma correction to the input signal.

In general, inverse gamma correction on the image signal X input from the PDP is performed as in Equation 1 below.

n: digit of X

: 1.8 to 2.5

In Equation 1, the maximum value of the gradation that can be expressed by an image processing system having an image signal that processes 8 bits of data is 255. Assuming that 2.2 gamma processing is performed, when the value actually input is 20 or less, it is 1 or less. Is represented by the value of the decimal point. Therefore, since the value becomes less than or equal to the minimum gradation level 1 for representation in a digital display device, it is impossible to express it even though there is a difference in gradation.

As described above, in the case of PDP, gray scales are represented by the number of pulses differently from CRT, so gray scales below the minimum pulse are virtually impossible. Therefore, gray scales below the minimum pulse are usually expressed by halftone expression using error diffusion. Is the way.

1A is a block diagram conceptually illustrating an image processing apparatus of a PDP according to the prior art.

Referring to FIG. 1A, inverse gamma correction is performed on the digital R, G, and B video signals through the inverse gamma correction unit 110. Subsequently, the inverse gamma corrected R, G, and B image signals are input to the display controller 130 after the error diffusion is performed through the error diffusion unit 120, respectively, and used for image processing of the panel 140.

1B is a block diagram conceptually illustrating an error diffusion algorithm according to the prior art, and FIG. 1C is a block diagram conceptually illustrating an algorithm for an error filtering unit.

Referring to the error diffusion algorithm according to the prior art with reference to Figure 1b, the value of the input original signal (R, G, B) is the gray level corrected signal (R) after removing the value below the decimal point in the threshold generation unit 210 ', G', B '). Subsequently, the output value and the original signal value of the threshold generator 210 are calculated by the first operator 220 to obtain an error value. Subsequently, after the error provided from the first operator 220 is filtered by the error filtering unit 230, the filtered error value is added to or subtracted from the original signal by the second operator 240 and provided to the threshold generator 210. do.

As shown in FIG. 1C, the error filtering unit 230 outputs a filtered error value by adding or subtracting errors of the N-1 frame and the error of the N frame.

As described above, the conventional error diffusion method independently spreads the digitally sampled R, G, and B signals, and thus provides a human visual system (HVS) characteristic. Since the gray scales are not considered, the minimum gray scale variation of R, G, and B becomes 1, respectively.

Therefore, the width of the minimum error is actually larger than the amount of change in luminance, so that the pattern of specific error diffusion is recognized as noise and the image is deteriorated. In addition, it had a fatal problem in smoothly changing gray levels.

For example, when the digitally sampled R, G, and B signals are independently error-diffused, in the case of a G signal having a large luminance component, the actual change step is the same as that of the R and B signals, but the luminance component is large, so that the pattern There is a problem that appears more clearly.

The present invention uses an algorithm of error diffusion to express intermediate gradation according to low gradation and gradation transition, while eliminating image degradation due to error diffusion pattern which is a byproduct of error diffusion recognized as noise, It is an object of the present invention to provide an image processing apparatus and method of a PDP, which makes it possible to express smoothly and to realize more vivid image quality.

1A is a block diagram conceptually illustrating an image processing apparatus of a PDP according to the prior art;

Figure 1b is a block diagram conceptually showing an error diffusion algorithm according to the prior art.

Figure 1c is a block diagram conceptually showing an algorithm for the error filtering unit of the error diffusion block.

2 is a graph showing the rate of change of the luminance signal Y as the R, G, and B signals independently change in one step;

Fig. 3 is a block diagram showing a PDP image processing apparatus according to the first embodiment of the present invention.

4 is a block diagram showing a PDP image processing apparatus according to a second embodiment of the present invention;

5 is an embodiment configuration diagram for the Y error diffusion unit.

6 is an implementation configuration diagram of a chroma error diffusion unit.

7 is a configuration diagram of a color difference signal filter unit.

8A to 8C are graphs showing signal conversion by the color difference signal filter unit.

9A is a graph of luminance signals according to average values of input video signals.

9B is a chromaticity signal graph according to an average value of an input video signal.

10A is a graph illustrating a method of controlling a luminance error diffusion according to a luminance signal.

10b is a graph illustrating a chromaticity error diffusion control method according to a chromaticity signal;

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

310: reverse gamma correction unit 320: RGB2YPbPr conversion unit

330: Y error diffusion unit 340: Chromaticity error diffusion unit

340: chroma signal filter 360: control unit

370: correction circuit unit 380: YPbPr2 RGB conversion unit

A PDP image processing method of the present invention for achieving the above object comprises a first step of performing inverse gamma correction on digital R, G, and B input signals; A second process of converting the R, G, and B signals subjected to the inverse gamma correction into a luminance signal (Y), a first chroma signal (Pb), and a second chroma signal (Pr); A third step of performing incorrect diffusion on the luminance signal, the first chroma signal, and the second chroma signal; And a fourth process of converting the luminance signal, the first chroma signal, and the second chroma signal into which the error diffusion is performed, into R, G, and B signals.

In addition, the image processing apparatus of the PDP of the present invention for achieving the above object includes an inverse gamma correction means for performing inverse gamma correction by receiving digital R, G, B signals; First conversion means for converting the R, G, and B signals subjected to the inverse gamma correction into a luminance signal (Y), a first chroma signal (Pb), and a second chroma signal (Pr); A first error diffusion unit that performs wrong diffusion on the luminance signal; A second error diffusion unit that performs a wrong diffusion on the first chroma signal; A third error diffusion unit that performs a wrong diffusion on the second chroma signal; Chromaticity signal filter means for removing and outputting unnecessary high frequency components with respect to the first and second chromaticity signals provided from the second and third error spreaders; Control means for receiving the digital R, G, and B signals and outputting a control signal corresponding to an average image input value; Correction means for correcting the luminance signal provided from the first error diffusion unit and the first and second chromaticity signals provided from the filter means in response to the control signal in comparison with the average image signal; And second conversion means for converting the luminance signal and the first and second chromaticity signals provided from the correction means into R, G, and B signals and outputting the gray-corrected R, G, and B signals. do.

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

(First embodiment)

3 is a block diagram showing a PDP image processing apparatus according to a first embodiment of the present invention.

Referring to FIG. 3, the PDP image processing apparatus according to the first embodiment of the present invention receives an inverse gamma correction unit 310 that receives digital R, G, and B signals and performs inverse gamma correction, and R in which inverse gamma correction is performed. Y, which incorrectly spreads the luminance signal Y and the RGB2YPbPr converter 320 for converting the G, B signals into the luminance signal Y, the first chroma signal Pb, and the second chroma signal Pr. An error diffusion unit 330, a chroma error diffusion unit 340 that performs incorrect diffusion on the first and second chroma signals Pb and Pr, and first and second chroma signal provided from the chroma error diffusion unit. A chromaticity signal filter 350 for outputting after removing unnecessary high frequency components, a controller 360 for receiving digital R, G, and B input signals and outputting a control signal corresponding to an average image input value; The luminance signal provided from the Y error diffusion unit 330 and the first signal provided from the filter unit 350 in response to the control signal of 360. And a correction circuit unit 370 for correcting the second chroma signal in comparison with the average video signal, and converting the luminance signal and the first and second chroma signal from the correction circuit unit 370 into R, G, and B signals. And an YPbPr2RGB converter 380 for outputting the gray-corrected R, G, and B signals R ', G', and B '.

The technical concept and operation of the PDP image processing apparatus according to the present invention will be described in detail with reference to the first embodiment of the present invention shown in FIG. 3.

According to the present invention, in consideration of the human visual system (HVS) characteristics of a low pass filter (LPF), a value greater than a resolution that can be expressed by a digital display with a luminance component is defined as an error, and the error is defined. By spreading to neighboring pixels, a smoother gray level can be expressed.

In addition, by multiplying the error-spreaded value by the experimentally appropriate gain value and converting it by applying a digital signal processing technique, it is possible to remove the by-products generated in the process of halftone expression invisibly.

2 shows the rate of change of the luminance signal Y as the R, G, and B signals independently change in one step.

As shown in Fig. 2, the rate of change of the luminance signal Y changes in a minimum value of 0.11 as the R, G, and B signals change by one step. That is, in the case of the B signal with the smallest change amount, the amount of change in the luminance signal is changed to 0.11 as the actual B signal phase changes by one, so that the gray level can be expressed more delicately. Since the change amount of the luminance with the change of the step is 0.59, the change width can be represented more delicately, so that the smoother gray level can be expressed.

In contrast, when the R, G, and B signals are processed by independent error diffusion, the error variation of the independent R, G, and B components is displayed on the actual display device. Therefore, not only image degradation due to discontinuous points of luminance components occurs in image data in which smooth grayscale transitions occur, but also the minimum resolution is changed by 1 independently of R, G, and B, thereby degrading the luminance resolution of the image. In the case of the G signal, which occupies 60% of the luminance component compared to the components of R and B, the minute value change due to error diffusion also greatly influences the variation of the luminance component. Not only does the discontinuity point of the luminance due to the pattern become larger, but the deterioration of the image is more noticeable.

Referring back to FIG. 3, the R, G, and B signals having the inverse gamma correction are converted into the luminance signal Y, the first chroma signal Pb, and the second chroma signal Pr through the RGB2YPbPr converter 320. do. The RGB2YPbPr converter 320 is a converter for performing the determinant shown in Equation 2 below.

The conversion of the luminance signal Y, the color difference signal Pb, and the Pr using the R, G, and B video signals can be obtained by a determinant such as Equation 2 below, and the R, G, B signals using the Y, Pb, and Pr signals The value can be obtained using the inverse of equation (2).

The luminance signal Y output from the RGB2YPbPr converter 320 is subjected to error diffusion through the Y error spreader 330. A detailed configuration and operation of the Y error diffusion unit 330 will be described later in detail with reference to FIG. 5.

The first and second chromaticity signals Pb and Pr output from the RGB2YPbPr converter 320 are spread by the chroma error diffusion unit 340. Although only one chroma error diffusion unit is shown in the drawing, error diffusion is performed on the first and second chroma signal Pb and Pr through respective chroma error diffusion units. The detailed configuration and operation of the chroma error diffusion unit 340 will be described later in detail with reference to FIG. 6.

The chroma signal filter unit 350 is a circuit for correcting the degree of color breakage after the error diffusion is performed in the chroma error diffusion unit 340, and its configuration and function will be described in detail with reference to FIG. 7.

The correction circuit unit 370 sets the luminance signal Y and the final values of the first and second color difference signals Pb and Pr corrected by the Y error diffusion unit 330 and the chroma error diffusion unit 340. to be. That is, a control signal corresponding to the average video input value is generated by the control unit 360 by receiving the digital R, G, and B input signals, and the luminance signal and the filter unit provided from the Y error diffusion unit 330 by the control signal. The first and second chromaticity signals provided from 350 are corrected relative to the average video signal. As a result, the image appears more clearly.

Since the average brightness level of the input image is small, most of them represent a dark screen. In this case, the luminance signal Y is processed through the Y error diffusion unit 330 as shown in FIG. 9A. If the amplification is increased to increase the contrast ratio between the dark images and the contrast ratio is increased, the displayed image is more clearly corrected. The correction circuit unit 370 performs this function.

In this case, since most images are dark, the recognition of the color difference signal is higher in human HVS than in the luminance signal. Therefore, in this case, the transition of the value of the color difference signal is remarkably visible and can lead to deterioration of the image due to excessive color components, as shown in FIG. 9B, through the chroma signal error diffusion unit 350. Attenuates the absolute values of the output first and second color difference signals and removes excessive color components to express a natural image.

The YPbPr2 RGB converter 380 converts the luminance signal and the first and second chromaticity signals provided from the correction circuit unit 370 into R, G, and B signals, and then corrects the gray scale R, G, and B signals R 'and G'. , B ').

As described above, the present invention converts the R, G, and B signals into luminance signals and color difference signals without error diffusion of the R, G, and B signals, and then error spreads the luminance signals and the color difference signals, respectively. By using the method, it not only enables fine gray scale expression but also eliminates the pattern of error diffusion due to the regularity of the pattern due to the use of the half gray scale representation method, thereby degrading the image. Implementation is possible. In addition, since the color cracking and the appearance of the boundary appearing in the change portion of the gradation are corrected, higher purity image quality can be realized.

Second Embodiment

4 is a block diagram showing a PDP image processing apparatus according to a second embodiment of the present invention.

Referring to FIG. 4, a delay unit 410 including a PDP image processing apparatus according to a first embodiment of the present invention and delaying and outputting the output of the inverse gamma correction unit 310 and the YPbPr2 RGB conversion unit ( And a calculation unit 420 for correcting a gain value for each output signal of the output signal 380 and adding the output signal to the corresponding output signal of the delay unit 410.

The second embodiment of the present invention is a further improvement of the first embodiment of the present invention. In the first embodiment of the present invention, the error with respect to the luminance signal has already been diffused to the neighboring pixels by the Y error diffusion unit, and the error occurring during the process of converting R, G, and B into Y and Pb Pr, and Again, a slight change occurs in the color components due to the error that occurs during the inverse transformation. In addition, deterioration may occur in the purity of color components of an image input by such components.

Therefore, in the second embodiment of the present invention, the original signal inputted through the delay unit 410 and the calculation unit 420 is corrected by an appropriate gain by correcting the value processed through the luminance error diffusion unit and the chromaticity error diffusion unit with an appropriate gain. It is possible to express gradation, thereby improving chromaticity, and it is possible to freely adjust the variation range of correction as compared with the first embodiment.

5 is a configuration diagram of the Y error diffusion unit applied to the first and second embodiments of the present invention.

Referring to FIG. 5, the Y error spreading unit delays the luminance signal Y output from the RGB2YPbPr converter 320 and outputs the delay unit 510 and a value below the decimal point from the output value of the delay unit 510. A threshold value generator 520 for outputting a gray level corrected luminance signal after removal, a first calculator 530 for calculating an error by calculating an output value of the delay unit 510 and an output value of the threshold value generator 520, and The error filtering unit 540 for filtering the error provided from the first operation unit 530 and the error filtering unit in proportion to a range of an absolute value for the luminance signal Y output from the RGB2YPbPr converter 320. A lookup table 550 for correcting the error provided from 540 and outputting the result; and a second calculation unit 560 for adding the output value of the lookup table to an output value of the delay unit and providing it to a threshold generation unit. .

The operation of the Y error spreading unit shown in FIG. 5 will be described.

The Y error spreading unit according to the present embodiment is output as a newly corrected value through a LUT having an appropriate gain according to the luminance level of a signal to which a value processed through error filtering through a conventional error diffusion algorithm is input. The delay unit 510 is used to synchronize the input signal. That is, an appropriate gain is set for the LUT by the original signal, and the value of the generated LUT is added to or subtracted from the original signal for setting the value.

For example, if a luminance signal of 150.45 is input, the threshold value generator 520 outputs a value of 150 to the first operator 530, from which a value below the decimal point is removed. Subsequently, the first operation unit 530 calculates an error value of 0.45 by calculating 150.45 and 150, and the error is filtered by the error filtering unit 540, and the filtered value propagates the error value to surrounding pixels. The error filtering unit 540 has a hardware configuration as described above with reference to FIG. 1C in the prior art.

The lookup table 550 sets the sign of the error through the error filtering unit 540 to simultaneously spread the sum of the error and the difference of the luminance signal, and expresses the slope of the absolute value of the error received from the surroundings. In other words, as the absolute value of K increases, the gain of the error received from the adjacent cell is amplified and expressed. Since the overall error range can be changed by the above block setting, smoother brightness change can be set where the luminance signal is small, and smoothness of the gray scale can be appropriately adjusted in the region where the luminance signal change rate is large. The gain of the K value is corrected according to the absolute value so as to be proportional to the range of the absolute value of the luminance signal of the current pixel before the error propagates.

6 is a configuration diagram of a chromatic error diffusion unit applied to the first and second embodiments of the present invention.

Referring to FIG. 6, the chroma error diffusion unit delays the color difference signal Pb or Pb provided from the RGB2YPbPr converter 320 and outputs the delayed unit 610 and the output value of the delay unit 610. A threshold value generator 620 for removing and outputting a value, a first calculator 630 for calculating an error by calculating an output value of the delay unit 610, and a value of the threshold value generator 620, and an RGB2YPbPr converter ( A luminance component comparator 640 for generating a control signal by comparing the luminance signal value provided from 320 to a reference value, and the luminance signal value is less than or equal to the reference value in response to a control signal output from the luminance component comparator 640. A selection unit 650 for outputting a zero error value and outputting an error value of the first operation unit 630 when the luminance signal value is larger than the reference value, and an error provided from the selection unit 650. Error filtering unit 660 for filtering, and A lookup table 670 for correcting and outputting an error provided from the error filtering unit in proportion to an absolute value range of the color difference signal output from the RGB2YPbPr converter 320, and output values of the lookup table 670. The second operation unit 680, which is added to the output value of the delay unit 610 and provided to the threshold value generation unit 620, compares the output value of the threshold value generation unit 620 with the color difference signal threshold, And a color difference threshold comparison unit 690 for outputting the corrected color difference signals Pb 'and Pr'.

The operation of the chroma error diffusion unit shown in FIG. 6 will be described.

Although the luminance is expressed as a medium as shown in FIG. 5, there may be a limit to completely softening the change portion of the gray scale. Therefore, in order to overcome this problem, the gradation expression using the HVS characteristic of the human being is used to diffuse the error of the chrominance expression portion to the surrounding pixels, thereby enabling a more smooth gray scale expression.

Actually, the boundary of the correct color in the luminance transition part is perceived as the color boundary and image deterioration in the human eye and appears as the deterioration of the image. In order to use this, gradation that cannot be expressed as the minimum gradation of color is mainly composed of the expression of intermediate gradation, and the phenomenon that the color seems to be broken in such part due to the rapid change of gradation in gradation expression as the gradation increases, and the boundary surface What appears to appear can be overcome through chromatic error diffusion of this embodiment. Or by compensating for the color change that is the best for humans to see around, humans will recognize a higher quality image.

The error diffusion of the chroma signal is controlled according to the value of the luminance component unlike the case of spreading the error of the general luminance signal to the surrounding pixels.

The signal range of the color difference signals Pb and Pr is in the range from -127 to 127. As the absolute value thereof decreases, the color saturation component becomes weak, and thus the color range signal Pb and Pr changes to achromatic color. Therefore, there should be a change in the correction component according to the absolute values of the color difference signals Pb and Pr. Since the absolute values of the color difference signals Pb and Pr are close to the achromatic colors, the expression due to the diffusion of the small error may appear to represent the wrong color of the image. In other words, when the error is diffused through the error diffusion of the chromaticity component in the region where the luminance component is small, the error component due to the change in the color crime table occupies more than the large luminance signal, causing deterioration of the image. Can work.

Therefore, it is necessary to control the enable or disable of the error diffusion unit according to the value of the luminance component. To this end, the chroma error diffusion unit of the present embodiment includes a luminance component comparison unit 640 and a selection unit 650.

The luminance component comparator 640 generates a control signal by comparing the luminance signal value provided from the RGB2YPbPr converter 320 with a reference value. The selector 650 outputs a zero error value when the luminance signal value is less than or equal to the reference value in response to a control signal output from the luminance component comparator 640, and when the luminance signal value is greater than the reference value. The error value of the first calculator 630 is output.

Thus, as shown in FIG. 10A In a small range, even if the actual chromaticity signal contains an error component, the error component is ignored, so that image degradation due to error diffusion at a small luminance component can be prevented. 10A is a graph illustrating a method of controlling a luminance error diffusion according to a luminance signal.

In addition, as the absolute value components of the chrominance signals Pb and Pr are small, the actual signal does not appear color. In this case, the error components appearing at the change of the color coordinate are relatively larger than the error of the chrominance signal. As a result, image degradation due to diffusion of error components may be caused. In order to prevent image deterioration due to an error occurring in a block that actually performs RGB2YPbPr conversion and error diffusion, as shown in FIG. By adjusting the value of the chromaticity to zero, the color change due to the small luminance change is removed from the mainstream image of the achromatic component, thereby eliminating the phenomenon of color breakdown. After all, it is possible to express high purity colors.

The chroma error diffusion unit of the present embodiment realizes smooth gradation expression and color expression through error diffusion of chrominance components at the same time as the high purity color expression.

When the chroma error diffusion unit is configured according to the present exemplary embodiment, the sum and the difference of the error may be simultaneously expressed, and the lookup table 670 sets the sign of the error through the error filtering unit 660 to set the error sum and the difference of the color difference signal. And the slope for the absolute value of the error received from the surroundings. As the absolute value of K increases, the gain of the error received from the adjacent cell is amplified and expressed. Since the overall error range can be varied by setting the error diffusion unit, it is possible to set a softer color change where the color difference signal is small, and to prevent color cracking in an area where the change rate of the color difference signal is large. Smoothness and chromaticity changes can be adjusted accordingly. The gain of the K value is used to control the absolute value so that the gain is proportional to the range of the absolute values of the color difference signals Pb and Pr of the current pixel before the error propagates.

7 is a configuration diagram of the chromaticity signal filter unit applied in the first and second embodiments of the present invention.

In practice, chromaticity signal is a part that color breakage is easily recognized by change of color component even with small change, and it is a by-product of error diffusion pattern used to express intermediate chromaticity signal that cannot be represented by digital technique. -May cause a change in the original color. In fact, the luminance error diffusion pattern generated through the luminance error diffusion is perceived as noise in the human eye, but the error diffusion pattern generated through the chromatic error diffusion causes the color purity to drop, and the error caused by the use of the chroma error diffusion circuit The diffusion pattern is more easily recognized by the human eye than the error diffusion pattern resulting from the error diffusion circuit of the luminance signal. Therefore, unnecessary high frequency components generated by the image processing processor should be removed.

Referring to FIG. 7, the chroma signal filter unit performs a low pass filter unit 710 and a low pass filter process to remove unnecessary high frequency components from an input signal. Contour enhancement unit 720 for the correction of the signal, and the gain setting unit 730 for adjusting the appropriate gain of the low-band filter 710 and the contour enhancement unit 720, such a digital image processor (Digital Through the processing of the Image Processor, it functions to express an image with high color purity.

FIG. 8A is a graph showing an input signal. After the input signal passes through the low band filter unit 710, the high frequency component is removed from the input signal as shown in FIG. After passing 720, the attenuated original signal as shown in Fig. 8C is corrected and converted into an ideal signal.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, the present invention converts the R, G, and B signals into luminance signals and color difference signals without error diffusion of the R, G, and B signals, and then error spreads the luminance signals and the color difference signals, respectively. Using the method, it is possible to express delicate and gray scales. As a result, there is an effect of overcoming the phenomenon of color breakup and the boundary surface appearing at the point where the gray level is rapidly changed.

In the present invention, in the error diffusion of the luminance signal and the chrominance signal, respectively, by varying the overall error range using a look-up table, it is possible to set a more smooth luminance and color change where the luminance and chrominance signal is small. In the area where the rate of change of the luminance and the color difference signal is large, the softness of the gray scale and the change in chromaticity can be appropriately adjusted, such as preventing color breakage.

In addition, according to the present invention, by correcting according to the average image input to the luminance signal and the color difference signal that is error-diffused through the correction circuit unit, there is an effect that the displayed image can be more clear and natural image representation.

Claims (15)

Reverse gamma correction means for receiving digital R, G, and B signals and performing inverse gamma correction; First conversion means for converting the R, G, and B signals subjected to the inverse gamma correction into a luminance signal (Y), a first chroma signal (Pb), and a second chroma signal (Pr); A first error diffusion unit that performs wrong diffusion on the luminance signal; A second error diffusion unit that performs a wrong diffusion on the first chroma signal; A third error diffusion unit that performs a wrong diffusion on the second chroma signal; Second conversion means for converting the error-diffused luminance signal and the first and second chromaticity signals into R, G, and B signals and outputting a gray-corrected R, G, and B signal PDP image signal processing apparatus comprising a. The method of claim 1, Delay means for delaying and outputting the output of the inverse gamma correction means; And an operation means for correcting a gain value for each output signal of the second conversion means and adding the output signal to a corresponding output signal of the delay means. The method of claim 1, Chromaticity signal filter means for removing and outputting unnecessary high frequency components with respect to the first and second chromaticity signals provided from the second and third error spreaders; Control means for receiving the digital R, G, and B signals and outputting a control signal corresponding to an average image input value; And Correction means for correcting the luminance signal provided from the first error diffusion unit and the first and second chromaticity signals provided from the filter means in response to the control signal in comparison with the average video signal and providing the second conversion means to the second conversion means. An image signal processing apparatus of a PDP, further comprising a. The method according to any one of claims 1 to 3, The first error diffusion unit, A delay unit for delaying and outputting the luminance signal provided from the first conversion means; A threshold generator for outputting a gray scale corrected luminance signal after removing a value below a decimal point from an output value of the delay unit; A first calculation unit calculating an error by calculating an output value of the delay unit and an output value of the threshold generation unit; An error filtering unit filtering an error provided from the first operation unit; A lookup table for correcting an error provided from the error filtering unit in proportion to a range of an absolute value of the luminance signal output from the second converting means and outputting the corrected error; A second operation unit which adds an output value of the lookup table to an output value of the delay unit and provides it to a threshold generation unit; PDP image signal processing apparatus comprising a. The method according to any one of claims 1 to 3, The second error diffusion unit, A delay unit for delaying and outputting a first color difference signal provided from the first conversion means; A threshold value generation unit for outputting after removing a value below a decimal point from the output value of the delay unit; A first calculation unit calculating an error by calculating an output value of the delay unit and a value of the threshold generation unit; A luminance component comparison unit for generating a control signal by comparing the luminance signal value provided to the first conversion means with a reference value; Outputting a zero error value when the luminance signal value is less than or equal to the reference value in response to a control signal output from the luminance component comparator, and outputting an error value of the first calculation unit when the luminance signal value is greater than the reference value; A selection unit; An error filtering unit filtering an error provided from the first operation unit; A lookup table for correcting an error provided from the error filtering unit in proportion to a range of an absolute value of the first color difference signal output from the second conversion means; A second operation unit which adds an output value of the lookup table to an output value of the delay unit and provides it to a threshold generation unit; Color difference threshold comparison unit for comparing the output value of the threshold generation unit with the color difference signal threshold value, and outputs the first color difference signal of the gray scale correction when the threshold value is more than a predetermined threshold PDP image signal processing apparatus comprising a. The method according to any one of claims 1 to 3, The third error diffusion unit, A delay unit for delaying and outputting a second color difference signal provided from the first conversion means; A threshold value generation unit for outputting after removing a value below a decimal point from the output value of the delay unit; A first calculation unit calculating an error by calculating an output value of the delay unit and a value of the threshold generation unit; A luminance component comparison unit for generating a control signal by comparing the luminance signal value provided to the first conversion means with a reference value; Outputting a zero error value when the luminance signal value is less than or equal to the reference value in response to a control signal output from the luminance component comparator, and outputting an error value of the first calculation unit when the luminance signal value is greater than the reference value; A selection unit; An error filtering unit filtering an error provided from the first operation unit; A lookup table for correcting an error provided from the error filtering unit in proportion to a range of an absolute value of a second color difference signal output from the second conversion means; A second operation unit which adds an output value of the lookup table to an output value of the delay unit and provides it to a threshold generation unit; Color difference threshold comparison unit for comparing the output value of the threshold generation unit with the color difference signal threshold value, and outputs a second color difference signal that is grayscale corrected when the threshold value is greater than a predetermined threshold value. PDP image signal processing apparatus comprising a. The method according to any one of claims 1 to 3, And said first converting means is a converter for performing the following determinant. The method according to any one of claims 1 to 3, The color difference signal filter means, A low pass filter unit for removing unnecessary high frequency components from its input signal; An outline enhancement unit for correcting the attenuated original signal while performing the low band filter processing; And And a gain setting section for adjusting appropriate gains of the low band filter section and the contour enhancement section. In the image processing method of the PDP, A first step of performing inverse gamma correction on the digital R, G, and B input signals; A second process of converting the R, G, and B signals subjected to the inverse gamma correction into a luminance signal (Y), a first chroma signal (Pb), and a second chroma signal (Pr); A third step of performing incorrect diffusion on the luminance signal, the first chroma signal, and the second chroma signal; And A fourth process of converting the luminance signal, the first chroma signal and the second chroma signal into which the error diffusion is performed, into R, G, and B signals PDP image processing method comprising a. The method of claim 9, And a fifth process of correcting the luminance signal, the first chroma signal, and the second chroma signal, wherein the error diffusion is performed, against an average value of the digital R, G, and B input signals. . The method of claim 9, And a sixth step of removing unnecessary high frequency components with respect to the first chroma signal and the second chroma signal which have been subjected to the error diffusion. The method of claim 9, A seventh step of correcting a gain value with respect to the R, G, and B signals converted in the fourth step; And An eighth process of adding the seventh process to a corresponding inverse gamma corrected R, G, and B signal; The image processing method of the PDP further comprises. The method of claim 9, Error diffusion of the luminance signal, Delaying the luminance signal; Generating an error value from the delayed luminance signal value; Filtering the generated error; Correcting the filtered error by a look-up table in proportion to a range of an absolute value of the delayed luminance signal; And Providing an error value corrected by the lookup table to the delayed luminance signal Image signal processing method of a PDP characterized in that it comprises a. The method of claim 9, Error diffusion of the first chroma signal, Delaying the first chroma signal; Obtaining an error value from the delayed first chroma signal value; Providing a zero error value when the luminance signal value is less than or equal to a reference value, and providing the obtained error value when the luminance signal value is greater than the reference value; Filtering the generated error; Correcting the filtered error by a look-up table in proportion to a range of an absolute value of the delayed luminance signal; And Providing an error value corrected by the lookup table by adding the delayed first chroma signal to the delayed first chroma signal; Image signal processing method of a PDP characterized in that it comprises a. The method of claim 9, Error diffusion of the second chroma signal, Delaying the second chroma signal; Obtaining an error value from the delayed second chroma signal value; Providing a zero error value when the luminance signal value is less than or equal to a reference value, and providing the obtained error value when the luminance signal value is greater than the reference value; Filtering the generated error; Correcting the filtered error by a look-up table in proportion to a range of an absolute value of the delayed luminance signal; And Adding the error value corrected by the lookup table to the delayed second chroma signal; Image signal processing method of a PDP characterized in that it comprises a.