CN1801293A - Fitting polynomial gray scale processing method for color plasma display panel - Google Patents

Abstract

The invention discloses a polynomial gray grade processing method for colorful plasma display which comprises steps of: dividing brightness intervals on display screen to make each brightness interval's minimum contrast sensitive threshold value as constant; calculating each brightness interval's input gray grade according to the maximum and minimum brightness when PDP works; applying gray grade correction and getting the output gray grade of each brightness interval; calculating coefficients of the polynomial by input and output gray grade; finally getting gray grade correction transform relationship.

Description

A kind of fitting polynomial gray scale processing method for color plasma display panel

Technical field

The present invention relates to a kind of gray scale processing method of display, the gradation of image disposal route of particularly a kind of color plasma display AC-PDP.

Background technology

Colour plasma display AC-PDP is a most promising High Resolution Display spare of 21 century, and wherein the ability of true reappearance gray scale (color depth) is to estimate the important indicator of PDP display quality.Tradition gray correction method requires signal to have linear relationship in whole transmission system theoretically, and transfer coefficient is as far as possible near 1.Simultaneously, consider the reasons such as nonlinear relationship of human eye, correction coefficient has been done suitable correction, in the cathode-ray tube CRT TV, obtained widespread use the brightness stimuli responsive.The characteristic of PDP is different from CRT, and traditional gray correction method is not suitable for the PDP as numeric display device.

When color PDP is done gray correction, reply R, G, B digital signal are done different processing respectively, make the transport property of tristimulus signals identical, the ratio of the colour system number that original color and reproduction are colored is constant, assurance does not have chromatic distortion and luminance distortion, mainly contains following several method at present: γ correction method, uniform colour space gray correction and piecewise linearity are proofreaied and correct.

1) γ correction method

This method is that the gray correction method with reference to CRT obtains, and the fundamental formular of correction is

Do＝mG(Di/n) ^(γ)

In the formula: Do is an output gray level; Di is an input gray grade; M is the maximum gray scale number after proofreading and correct, and n is that the maximum gray scale before proofreading and correct is counted general n and is not more than m; G is the white point correction factor; γ is the gray correction coefficient, and value is between 2.2～2.8 usually, meets the electro-optic transfer characteristic of CRT substantially.In the CRT television system, the picture signal before and after proofreading and correct all is an analog quantity, is continuous signal, if processing is good, does not have gradation loss substantially.Concerning PDP, Di is the digital gray scale signal after the precorrection, even γ satisfies the requirement of system linear transport property, Do also can't eliminate the luminance distortion that the Di digitizing brings, and the digitizing gray correction meeting of Do itself further brings distortion in the rounding off of gray scale.Practical application shows that there is serious gradation loss in this bearing calibration improperly, or makes the loss in detail of dark picture areas, perhaps makes the continuous gray level of some script that the sensation of obvious sudden change is arranged.

2) uniform colour space gray correction

This method thinks to have only visual lightness grade but not physically brightness degree is only effective gray level, therefore in the LED full-color screen is used, utilizes the inversionization of uniform colour space lightness and brightness relationship to carry out gray correction, promptly

Do＝m((Di/n+0117)×4) ³/100

This method has had improvement than the γ correction method between the low gray area of image, but the gradation loss in full luminance interval is still bigger.This method is just the same to the correction coefficient of three primary colours, this is inappropriate to the PDP as high-end display, because the colour system of each primary colours is counted difference, change the ratio difference that each luminance primary changes under the uniform situation in lightness, the different environment of watching also can influence the lightness grade classification.

3) piecewise linearity is proofreaied and correct

This method is divided into 0,1 to input gray level by the interval, and 2,3,127,128,129,255, correspondence is output as 0,0.5,1,1.5,63.5,64,66,255, perhaps input gray level is divided into 0-64-129-255, and correspondence is output as 0-48-288-1023, and the brightness in each input and output sub-range is linear change.Its main target is that the 8bit data are converted to 9bit or 10bit, has eliminated the round-off error of preceding two kinds of methods on gray level substantially, shows that distinguishable maximum gray shade scale still is 256 grades, just the numerical value spacing that characterizes gray level is widened.Compare with preceding two kinds of methods, this method has stronger specific aim, can increase fixing hardware cost and design difficulty in the enforcement, and the sub-number of fields and the sacrificing luminance that drive with raising PDP are cost.If input gray grade is 9bit or 10bit, this method and preceding two kinds of methods do not have the difference of essence.

Summary of the invention

The purpose of this invention is to provide a kind of fitting polynomial gray scale processing method for color plasma display panel, solved existing problem in the above-mentioned color PDP gray correction method, gradation loss and distortion are reduced greatly.

The technical solution adopted in the present invention is, a kind of fitting polynomial gray scale processing method for color plasma display panel carries out according to the following steps:

At first, divide the brightness section of display screen, making the minimum contrast sensitivity threshold dSmin of each brightness section is constant;

Secondly, high-high brightness Lmax and minimum brightness Lmin substitution following formula: the Lmin=(1+dSmin) when recording PDP work under a certain environment ^(n-1)* Lmin,

Try to achieve maximum distinguishable gray level n=1+ln (Lmax/Lmin)/ln (1+dSmin), promptly obtain the input gray grade n of each brightness section;

Then, according to following formula: m Δ L=(1+dSmin) ^(n-1)* Lmin carries out gray correction, obtains the output gray level m of each brightness section after the gray correction, wherein Δ L be minimum brightness at interval;

The input gray grade n of each brightness section that above-mentioned steps is obtained, output gray level m substitution following formula again:

$\left(\begin{array}{c}{m}_1\\ m_2\\ \\ m_n\end{array}\right)=\left(\begin{array}{cccc}{n}_1^3& n_n^2& n_1& 1\\ n_2^3& n_n^2& n_2& 1\\ & & & \\ n_n^3& n_n^2& n_n& 1\end{array}\right)\left(\begin{array}{c}{k}_3\\ k_2\\ k_1\\ k_0\end{array}\right),$

Try to achieve multinomial coefficient k3, k2, k1, k0 value;

At last, with each multinomial coefficient k value substitution m=k3n+k2n+k1n+k0, promptly obtain the gray correction transformation relation.

It is 0.5Cd～0.8Cd that minimum brightness is spaced apart Δ L value.

Because gray scale processing method of the present invention is compared with existing disposal route, do not causing under the situation that other index worsens, gradation loss and distortion are reduced greatly, the display quality of image is significantly improved.

Embodiment

The present invention is described in detail below in conjunction with embodiment.

The brightness range of display device reconstruction of scenes is more much smaller than the brightness range of original scene, but still can give the people real on-the-spot impression, main cause is that the achromatic sensation of human eye is relative, that is to say, certain watching under the environment, be consistent with original scene as long as guarantee the gray scale and the contrast of image, just can view and admire impression to we are comfortable.

According to this principle, gradation loss when reducing the PDP gray correction and distortion, and do not cause the deterioration of other indexs, just must consider the characteristic of screen, in conjunction with principal elements such as human eye vision sensory characteristics, the present invention proposes and fit the polynomial expression gray scale processing method.

In certain environment and brightness range, the ratio that the appreciable minimum brightness of human eye changes dL and scene brightness L is approximately constant, by the sensorial variation dSmin that dL produces, is the least unit of sensation.The sensation and the logarithm of brightness have linear relationship in brightness section necessarily, and during brightness L＞100cd/m, dSmin is approximately constant.

If the minimum brightness that shows is Lmin, high-high brightness is Lmax, and the minimum contrast sensitivity threshold is dSmin, then has

Lmin＝(1+dSmin) ^(n-1)*Lmin

That is petty, is n=1+ln (Lmax/Lmin)/ln (1+dSmin) necessarily watching the maximum distinguishable gray level under the condition.

Input gray grade n is not only relevant with self brightness of image, is decided by that also certain watches the contrast under the environment and the sensitivity of human eye.

Plasma scope PDP gray correction should in conjunction with the brightness range and the different sensitivity threshold value of human eye in different brightness section that it shows, be repartitioned brightness degree according to the digitizing gray-scale value of input, realizes that best gray scale shows.With addressing display separation driving method commonly used is example, the principle of PDP demonstration multi-grayscale is kept umber of pulse by adjusting and is realized, therefore generally need be divided into many groups by 8421 yards keeping umber of pulse, the minimum brightness of Xian Shiing is spaced apart Δ L like this, its value is controlled at 0.5Cd～0.8Cd, supposes that display screen can the gray-scale displayed level be m, and the distinguishable gray level of human eye is n, be input gray grade, the m value that following formula is set up is exactly the output valve of gray correction

mΔL＝(1+dSmin) ^(n-1)*Lmin

According to the situation of dSmin in different brightness section variations, the brightness of PDP is divided into some intervals, make each brightness section dSmin be approximately constant, according to each interval brightness minimum value dSmin and the distinguishable gray level n of this interval human eye, calculate corresponding brightness value L, just can obtain the gray level that obtains from branch brightness such as physical parameter consideration m levels, promptly proofread and correct the gray scale of output.In actual applications, can adopt the method for quadravalence fitting of a polynomial to obtain the gray correction transformation relation

m＝k3n+k2n+k1n+k0.....(1)

In the formula: m, n are output and input gray grade; K3, k2, k1, k0 are multinomial coefficients.

With m, the n substitution formula (1) of trying to achieve above, the value that can try to achieve ki as shown in the formula

$\left(\begin{array}{c}{m}_1\\ m_2\\ \\ m_n\end{array}\right)=\left(\begin{array}{cccc}{n}_1^3& n_n^2& n_1& 1\\ n_2^3& n_n^2& n_2& 1\\ & & & \\ n_n^3& n_n^2& n_n& 1\end{array}\right)\left(\begin{array}{c}{k}_3\\ k_2\\ k_1\\ k_0\end{array}\right)---\left(2\right)$

Promptly obtain the gray correction transformation relation.

With certain 42 cun color PDP as embodiment

Under indoor environment, the high-high brightness Lmax=192cd/m when recording PDP work, minimum brightness Lmin=3192cd/m, the brightness section of screen is divided and gray scale calculating sees the following form:

Brightness section	The dsmin value	Input gray level degree n	Output gray level m
				0～10 11～30 31～100 101～192	0.05 0.018 0.014 0.009	0～32 33～93 94～186 187～255	0～8 9～34 35～136 137～255

In the input gray level n value that records of each brightness section, output gray level m value substitution formula (2) in the table,

$\left(\begin{array}{c}{m}_1\\ m_2\\ \\ m_n\end{array}\right)=\left(\begin{array}{cccc}{n}_1^3& n_n^2& n_1& 1\\ n_2^3& n_n^2& n_2& 1\\ & & & \\ n_n^3& n_n^2& n_n& 1\end{array}\right)\left(\begin{array}{c}{k}_3\\ k_2\\ k_1\\ k_0\end{array}\right)---\left(2\right)$

Try to achieve k3=00010, k2=-00322, k1=06584, k0=-1.5888, substitution formula (1)

m＝k3n+k2n+k1n+k0.....(1)

Promptly obtain the gray correction transformation relation.

Disposal route of the present invention is more than the gray level that additive method reproduces, as calculated, its result shows that the average gray loss of γ correction method and uniform colour space gray correction is respectively 1017%, 617%, and polynomial fitting disposal route of the present invention is 4.5%.

Disposal route of the present invention should the every index of overall equilbrium just can reach good display effect, also can as gray correction being carried out simple space error diffusion, further improve gray correction curve etc. in conjunction with some other method.

Claims (2)

1. a fitting polynomial gray scale processing method for color plasma display panel is characterized in that, this method is carried out according to the following steps:

At first, divide the brightness section of display screen, making the minimum contrast sensitivity threshold dSmin of each brightness section is constant;

Secondly, high-high brightness Lmax and minimum brightness Lmin substitution following formula: the Lmin=(1+dSmin) when recording PDP work under a certain environment ^(n-1)* Lmin,

Try to achieve maximum distinguishable gray level n=1+ln (Lmax/Lmin)/ln (1+dSmin), promptly obtain the input gray grade n of each brightness section;

Then, according to following formula: m Δ L=(1+dSmin) ^(n-1)* Lmin carries out gray correction, obtains the output gray level m of each brightness section after the gray correction, wherein Δ L be minimum brightness at interval;

The input gray grade n of each brightness section that above-mentioned steps is obtained, output gray level m substitution following formula again:

$\left(\begin{array}{c}{m}_1\\ m_2\\ \\ m_n\end{array}\right)=\left(\begin{array}{cccc}{n}_1^3& n_n^2& n_1& 1\\ n_2^3& n_n^2& n_2& 1\\ & & & \\ n_n^3& n_n^2& n_n& 1\end{array}\right)\left(\begin{array}{c}{k}_3\\ k_2\\ k_1\\ k_0\end{array}\right),$

Try to achieve multinomial coefficient k3, k2, k1, k0 value;

At last, with each multinomial coefficient k value substitution+k2n+kln+k0, promptly obtain the gray correction transformation relation.

2. in accordance with the method for claim 1, it is characterized in that described minimum brightness interval delta L value is 0.5Cd～0.8Cd.