CN100403369C - Method for reducing low gray scale grade false contour of plasma display panel - Google Patents

Abstract

The present invention discloses a method for reducing a low gray scale grade false contour of a plasma display, which calculates the actual output brightness value of plasma according to the calculation formula of the actual output brightness of a plasma display panel. After the gray scale value of the current processing pixel has inverse gamma exchange, the present invention is added by the diffusion errors of other pixels so as to obtain a calculation gray scale value. Then, the present invention finds out a most approaching value to the calculation gray scale value from the actual output brightness value of the plasma display panel. The most approaching value is used as the actual display gray scale value. The difference value of the actual display gray scale value and the calculation gray scale value is used as a pixel error. Finally, the pixel errors are diffused to nearby pixels according to the classical Floyd Steinberg error diffusion coefficient. The present invention can reflect the error diffusion of actual output brightness characteristics of PDP and can effectively restrain the low gray scale grade false contour in the plasma display panel.

Description

Reduce the method for low gray scale grade false contour of plasma display panel

Technical field

The present invention relates to the image processing method of big screen plasma body display device, particularly reduce the method for low gray scale grade false contour of plasma display panel.

Background technology

AC-PDP comprises a plurality of addressing electrodes and a plurality of perpendicular to keeping and scan electrode that addressing electrode is arranged.Addressing, keep, scan electrode all is coated with insulation course so that it separates with discharge space.At addressing electrode and keep, the place that intersects of scan electrode, form the discharge cell corresponding with pixel.

The output brightness of Plasmia indicating panel is linear change according to input, and CRT has the characteristic of non-linear output, in order to remedy the non-linear output characteristics of CRT, the television video frequency signal of input all passes through the gamma conversion, therefore, in order in Plasmia indicating panel, to show television image, need do corresponding adjustment, promptly anti-Gamma correction for the digital value of input.

Picture signal is through behind the anti-Gamma correction, and several gray shade scales can be merged into a brightness value output, especially for the low grey scale signal of importing.This merging causes sudden change visually, the false contouring when just having caused low gray shade scale.

There are various employing error diffusion or dither algorithm to suppress the trial of low gray shade scale false contouring among the PDP, also have the method for a kind of many brightness degree field to be used to address this problem recently.Yet the output brightness degree increase of PDP is not balanced.Therefore they often can not effectively reduce low gray shade scale false contouring phenomenon.

Summary of the invention

The objective of the invention is to overcome above-mentioned technical deficiency, a kind of method that reduces low gray scale grade false contour of plasma display panel is provided, the error diffusion that can reflect the actual output of Plasmia indicating panel light characteristic can effectively suppress low gray shade scale false contouring in the Plasmia indicating panel.

Technical scheme of the present invention is achieved in that

1) according to the actual output brightness calculation formula of Plasmia indicating panel:

$L=L_D+L_R$

$\≡\underset{i}{\mathrm{\Σ}}{\mathrm{\ω}}_i{l}_i+L_R$

Obtain isoionic actual output brightness value,

Wherein, when i son field lighted, ω _iJust be 1, if i son do not lighted ω then _iBe 0; The Plasmia indicating panel actual output brightness value of L for measuring, L _DBe the brightness of the phase of keeping, L _RBe initial period and address period brightness and, l _iIt is i sub the brightness value of measuring;

2) propagated error that adds other pixel after the gray-scale value when the pixel of pre-treatment is carried out anti-gamma conversion obtains one and calculates gray-scale value;

3) find out and calculate the immediate value of gray-scale value from the actual output brightness value of Plasmia indicating panel then, be worth as the actual displayed gray-scale value with this, with this actual displayed gray-scale value and the difference of calculating gray-scale value as pixel error;

4) at last the Floyd Steinberg error diffusion coefficient of pixel error by classics spread toward neighborhood pixels.

The present invention adopts said method, can reflect the error diffusion of the actual output of PDP light characteristic, can effectively suppress low gray shade scale false contouring in the Plasmia indicating panel.

Description of drawings

Fig. 1 is the output brightness of CRT to input signal.

Fig. 2 is the output brightness of PDP to input signal.

Fig. 3 is 42 inches plasma data processing block diagrams.

Embodiment

With reference to Fig. 1, shown in Figure 2, the output brightness of Plasmia indicating panel is linear change according to input, and CRT has the characteristic of non-linear output.

With reference to shown in Figure 3, for 42 inches Plasmia indicating panel among the embodiment, its data processing section is at first, the data-signal that receives is through after the anti-gamma conversion, handle through error diffusion, varitron field number, the driving according to the ADS driving method requires data are separated by the son field then, and the data storage of after separating is sent to the addressing driving circuit in frame memory.

The luminosity of CRT is to adjust by the intensity of the electron beam of simulation control impact fluorescence powder, and the gray shade scale of Plasmia indicating panel is then kept umber of pulse adjustment by adjustment.For example, in order to show 256 grade gray scales, a TV Field is divided into 8 son fields, and output brightness degree of each son field is 2, wherein, and 0=＜n＜8, brightness degree the adding up of human eye impression for each sub-field brightness.The output brightness of PDP is linear change according to the input digit value, and CRT has the characteristic of non-linear output, in order to remedy the non-linear output characteristics of CRT, the television video frequency signal of input all passes through the gamma conversion, therefore, in order in Plasmia indicating panel, to show television image, need do corresponding adjustment, promptly anti-Gamma correction for the digital value of input.

In the anti-gamma conversion, the gray shade scale of input is through equation 1 conversion

$Y=k\×{\left(\frac{x}{255}\right)}^y---\left(1\right)$

In the formula, x represents that the gray shade scale imported, Y represent the gamma value of being scheduled to, and K represents the gray shade scale number of the maximum of white point representative, and Y is the desirable output display brightness number of degrees for input gray level grade X.

Picture signal is through behind the anti-Gamma correction, and several gray shade scales can be merged into a brightness value output, especially for the low grey scale signal of importing.This merging causes sudden change visually, the false contouring when just having caused low gray shade scale.

There are various employing error diffusion or dither algorithm to suppress the trial of low gray shade scale false contouring in the Plasmia indicating panel, also have the method for a kind of many brightness degree field to be used to address this problem recently.Yet all these methods suppose that all the output brightness increase of Plasmia indicating panel all is balanced, so they often effectively do not reduce low gray shade scale false contouring phenomenon, because the output brightness degree increase of Plasmia indicating panel is not balanced.

The output brightness and the theoretical value of Plasmia indicating panel are inconsistent, and the actual output brightness of PDP is obtained by following formula

$L=L_D+L_R$

$\≡\underset{i}{\mathrm{\Σ}}{\mathrm{\ω}}_i{l}_i+L_R---\left(2\right)$

Wherein, when i son field lighted, ω _iJust be 1, if i son do not lighted ω then _iBe 0.The Plasmia indicating panel actual output brightness value of L for measuring, L _DBe the brightness of the phase of keeping, L _RBe initial period and address period brightness and, l _iIt is i sub the brightness value of measuring.

Therefore, if after a Plasmia indicating panel is carried out anti-gamma conversion, suppose that input signal is 21, the theory of PDP output brightness is 1, i.e. first son of addressing only, however PDP can not export display brightness 1, but export 1.912.

Because the restriction of the resolution of photoreceptor on the retina, the resolution of human eye generally can be limited to roughly on one the radian, therefore, the visual sense feeling of human eye is based on average brightness value around the pixel but not the brightness value of an independent pixel.If watch 42 inches plasm TV in 3 meters places far away of distance, the identification for image will be the pixel scale of a corresponding 2*2 so.Error diffusion is based on this characteristic, and the output error of certain pixel is diffused on the pixel of closing on.

At first, calculate desirable gray shade scale number by formula (1), value after the anti-gamma conversion adds the error amount sum of certain weights, look into look-up table according to the value after the summation, determine the actual output gray level value of PDP, simultaneously, table look-up output calculated value and the error between the output valve of tabling look-up, this error amount is as the error toward external diffusion, be diffused into adjacent pixels, the weight of error is by the definition of Floyd Steinberg error diffusion coefficient, and wherein, the computing method of the actual output gray level value in the look-up table are: with the l that measures _iSubstitution formula 2 calculates all brightness number of PDP output, then, the brightness value that is calculated with the immediate brightness replacement that can express, with this brightness value as the brightness value in the look-up table.Simultaneously, the error amount in the look-up table is the poor of calculated value and table intermediate value.According to the brightness value of revising in the table, can determine which sub need be lighted, those sub does not need to light.Determined after the look-up table, just carried out error diffusion with error diffusion method.

Table 1 is this PDP under the situation of 9 sons, the intrinsic brilliance of measurement and the contrast of desirable gray-scale value.Among this embodiment, according to the brightness value of measuring, obtain the intrinsic brilliance value of all gray shade scales, value is modified to the value that this PDP can express deposits in the look-up table, simultaneously, according to the method in the explanation, the error that calculates also deposits in the look-up table, for the input data, through the value after the anti-gamma conversion, add after the error of all certain weights the output brightness value and the error amount that is diffused into neighbor of the output PDP that tables look-up.

This method has reflected the actual output characteristics of PDP, has reduced desirable gray shade scale and the true but error between the brightness, can effectively reduce for the profile that hangs down gray shade scale.

The brightness value of table 1 actual measurement and the contrast of desirable gray shade scale

Measure brightness (cd/m 2)	2.32	3.30	5.2	9.0	16.5	30.8	59.3	109.8	203.8
										Desirable brightness degree	0.5	1	2	4	8	16	32	64	128

Claims (1)

1. reduce the method for low gray scale grade false contour of plasma display panel, it is characterized in that,

1) according to the actual output brightness calculation formula of Plasmia indicating panel:

$L=L_D+L_R$

$\≡\underset{i}{\mathrm{\Σ}}{\mathrm{\ω}}_i{l}_i+L_R$

Obtain isoionic actual output brightness value,

Wherein, when i son field lighted, ω _iJust be 1, if i son do not lighted ω then _iBe 0; The Plasmia indicating panel actual output brightness value of L for measuring, L _DBe the brightness of the phase of keeping, L _RBe initial period and address period brightness and, l _iIt is i sub the brightness value of measuring;

2) propagated error that adds other pixel after the gray-scale value when the pixel of pre-treatment is carried out anti-gamma conversion obtains one and calculates gray-scale value;

3) find out and calculate the immediate value of gray-scale value from the actual output brightness value of Plasmia indicating panel then, be worth as the actual displayed gray-scale value with this, with this actual displayed gray-scale value and the difference of calculating gray-scale value as pixel error;

4) at last the Floyd Steinberg error diffusion coefficient of pixel error by classics spread toward neighborhood pixels.

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