CN1588513A - Driving control method for increasing low grey degree value picture details - Google Patents

Abstract

The invention is a driving control method for strengthening the low grey image detail, which belongs to plasma television display technology field, and which includes basic circuit of plasma display screen, reverse gamma correcting method. Its features: the method is dynamic reverse gamma correcting method. The method increases peak extract circuit, judgment circuit and delay circuit on the basic circuit and form the special correcting circuit, carries on dynamic reverse gamma correction, the quantification bit width changes self adaptively with the peak brightness of the image in order to reduces the grey loss of the image. The method improves the display image in plasma television display screen.

Description

A kind of drive controlling method that strengthens low grey degree value picture details

Technical field

The invention belongs to plasma television display technique field, particularly strengthen the Drive Control Technique that plasma display panel PDP (Plasma Display Panel) reproduces low grey degree value picture details.

Background technology

Plasma television is the plate wall-hanging new television models of using plasma display board PDP as display screen, the plasma display panel formula is utilized inert gas to produce gas discharge under certain voltage and is formed the direct visible emitting of plasma, perhaps emissioning line and then excite RGB (being RGB) three primary colours photoluminescent phosphor and a kind of active illuminating type flat-panel display device of visible emitting.The major parameter of color PDP has resolution, the capacity of display, brightness, contrast, gray scale etc., and wherein what of colored number how much gray shade scale has determined.When the transport property of television system is linear, when the scene brightness Lo that display system is reproduced is proportional to the brightness Li of original scene, could undistorted transmission signals and reproduced image.Because mutual conversion and transmission between the photosignal make whole television transmission system have nonlinear feature, nonlinear source has 3 kinds: pick-up tube, transmission system and display device but in fact.Cathode ray tube (CRT) display device with present main flow is an example, the brightness Lo of its reconstruction of scenes and control and have nonlinear relationship between the luminous electric signal S:

$\mathrm{Lo}\∝S^{{\mathrm{\γ}}_2}$

γ ₂Be the precorrection coefficient, general value is between 2.2～2.8, for the transport property that makes whole TV system remains linearity, must carry out precorrection to the television transmission system before the CRT, and the whole TV system transport property is after the precorrection:

$\mathrm{Lo}=k{L}_i^{{\mathrm{\γ}}_1{\mathrm{\γ}}_2}$

Wherein, k is a ratio system, γ ₁Be the precorrection coefficient, get 0.45, make γ ₁γ ₂≈ 1, and the signal of process precorrection imports the CRT monitor part into, the transport property of whole TV system, and promptly Lo and Li are linear relationship, like this could undistorted ground reproduced image.

Different with CRT, PDP is a numeric display device, and its electro-optic transfer characteristic is linear, i.e. γ ₂=1, directly replace CRT with PDP, in order to take into account CRT, done gray scale precorrection in the transmission channel, if do not do gray correction at the PDP light transfer characteristic, γ then ₁γ ₂=0.45, the transport property of whole display system shows as non-linear, and reproduced image will produce serious gradation loss and tonal distortion.

Therefore, must carry out gray correction at the precorrection of television transmission system in PDP, claim anti-γ to proofread and correct, it is a digital processing process that anti-γ proofreaies and correct, and there are following relationship in the data image signal Vo of output and the data image signal Vi of input:

$\mathrm{Vo}={\mathrm{Vi}}^{{\mathrm{\γ}}_2}$

γ ₂General value is between 2.2～2.8, establishes the digital signal that Vi is 8bit.With γ ₂=2.2 is example, when having provided 8,9 and 10 in Fig. 1 table and having quantized, corresponding to the digital signal Vo that exports in the low gray-scale value scope in Vi=0～67, as can be seen, Vi is 68 gray levels, for 8,9,10 quantifications, the number of greyscale levels of Vo reduces to 11,21,39 respectively, as seen, gradation loss occurred in low gray-scale value zone, calculating shows, 8 quantize 84%, 9 of gradation loss and quantize 69%, 10 quantification of gradation loss gradation loss 43%, 11 quantize 25%, 12 of gradation loss and quantize gradation loss 15%.The gradation loss in low gray-scale value district causes the distinguishable luminance level of this gray area to reduce image quality decrease.In order to improve picture quality, should set about reducing gradation loss, also will strengthen the quantification bit wide, be mutual contradiction yet reduce gradation loss with improving PDP brightness.

It can also be seen that from Fig. 1 table the minimal gray difference of 8 quantifications is 1, promptly quantified precision is that the precision of 1,9 quantification is that the precision of 0.5,10 quantification is 0.25, promptly quantizes bit wide and adds 1, and precision was divided by 2 before quantified precision equaled to widen.

For adopting a son display mode to realize for the PDP of gray-scale Control, the increase of bit wide is to be cost to improve the sub-number of fields that drives and sacrificing luminance, and reducing gradation loss is conflicting with improving PDP brightness.

Traditional anti-γ proofreaies and correct and adopts fixing quantification bit wide, considers the brightness of PDP, and bit wide is unsuitable excessive, and this will make the low gray-scale value zone of reproduced image produce serious gradation loss, and image level is poor.This contradiction products for further solves.

Summary of the invention

The technical issues that need to address of the present invention are, at the calibration to gray scale in the known technology is to adopt fixing quantification bit wide, owing to take into account the brightness of PDP, bit wide is unsuitable excessive, this will cause low gray areas to produce serious gradation loss, in order to solve this contradiction technically, overcome the deficiency in the prior art, will adopt again and a kind ofly keep luminance level not reduce the gray scale calibration steps that brightness number is carried out again for reducing gradation loss, the object of the present invention is to provide a kind of drive controlling method that strengthens low grey degree value picture details, the objective of the invention is to rely on following technical scheme to realize, a kind of for reducing the drive controlling method that gradation loss keeps luminance level, the basic circuit that comprises plasma display panel (PDP), anti-gamma correction method, it is characterized in that, described bearing calibration, be meant dynamic anti-gamma correction method, this method increases the peak extraction circuit again on the basis of plasma display panel (PDP) basic circuit, decision circuitry and delay circuit and the special correcting circuit that constitutes, carrying out dynamic anti-γ proofreaies and correct, under the constant situation of the sub-number of fields order of plasma display panel (PDP), make quantification bit wide value reproduce the gradation loss that hangs down gray-value image to reduce with the adaptive change of the peak brightness of reproduced image.Peak extraction circuit in the described special correcting circuit is a comparator circuit, and adjacent plain mutually signal is compared, and described decision circuitry is the size according to maximum gradation value M, selects weight scheme to remove controlled encoder and umber of pulse treatment circuit.Described delay circuit, be with signal delay one field time, make that to enter anti-checking gamma circuit signal corresponding according to the control signal that this calculates with decision circuitry, color PDP is to adopt a son display mode to realize gray-scale Control, promptly a TV Field (abbreviating the field as) is divided into successively luminous a plurality of sons field, realize that 256 grades of gray scales demonstrations need weight to be respectively 8 son fields of 1-2-4-8-16-32-64-128 (binary coding) at least, various combination by these 8 son fields is realized its gray level, then need the son field more than 8 could realize that 256 grades of gray scales show for non-binary code, to duplicate sign indicating number this moment, and duplication code makes cataloged procedure optimized.The weight of emission light pulse number of each son and son is directly proportional, and therefore, son display mode is actually by adjusting led pulse number and realizes gray-scale Control.

PDP generally adopts 11 or 12 son fields to realize gray-scale Control, is example with 12 son fields, supposes to choose following weight scheme:

1-2-4-7-11-16-22-29-37-46-56-67 weight sum is 298, therefore this scheme can show 299 gray levels (0～298) at most, preceding 11 sons weight sum is 231, when the maximum gradation value of reproduced image is not more than 231, utilize preceding 11 son fields to be enough to coded image data, need not consider weight 67 when promptly encoding, change weight 67 into weight 0.5 for this reason, it is as follows to adjust weight scheme:

0.5-1-2-4-7-11-16-22-29-37-46-56 still be 12 sons, weight and be 231.5, minimal weight is 0.5, preceding 11 sons weight sum are 175.5.When the maximum gradation value of reproduced image is not more than 175, utilize preceding 11 son fields to be enough to coded image data, need not consider weight 56 when promptly encoding, change weight 56 into weight 0.25 for this reason, it is as follows to adjust weight scheme once more:

0.25-0.5-1-2-4-7-11-16-22-29-37-46 still be 12 sons, weight and be 175.75, minimal weight is 0.25.The rest may be inferred, and its result is as shown in Fig. 2 table.

Proofread and correct in conjunction with anti-γ, owing to gradation loss occurs in low gray-scale value district, along with the increase that quantizes bit wide, gradation loss reduces.When the maximum gradation value M of reproduced image greater than 231 the time, in general, image is brighter, the low gray-scale value zone in the image is less, adopts 8 quantifications even anti-γ proofreaies and correct, gradation loss is also little, this moment is corresponding, and to adopt minimal weight be 1 weight scheme; When the maximum gradation value M of reproduced image was between 175～231, the low gray-scale value zone in the image was moderate, and anti-γ proofreaies and correct and adopts 9 quantifications, and gradation loss alleviates, and this moment is corresponding, and to adopt minimal weight be 0.5 weight scheme; When the maximum gradation value M of reproduced image was between 129～175, the low gray-scale value zone in the image was bigger, and anti-γ proofreaies and correct and adopts 10 quantifications, and gradation loss further alleviates, and this moment is corresponding, and to adopt minimal weight be 0.25 weight scheme; The rest may be inferred, and the result is as shown in table 3.As seen, the present invention varies in size according to the low gray-scale value zone of reproduced image, and the quantification bit wide of selecting anti-γ to proofread and correct is adaptively improved low gray areas picture quality.The invention has the beneficial effects as follows, this dynamic anti-γ proofreaies and correct and provides, and quantizing bit wide can change, and has reduced the gradation loss that reproduces low gray-value image, the stereovision that has improved image does not reduce brightness value again, has improved the display frame of plasma television display screen.

Description of drawings

Fig. 1 is 8,9,10 the anti-γ correction charts that quantize bit wide in low gray-scale value district

Fig. 2 chooses the scheme chart for weight

Fig. 3 is maximum gradation value M and minimal weight, the chart that concerns that quantizes bit wide

Fig. 4 shows the circuit composition diagram of PDP for realizing plasma television of the present invention

Embodiment

With reference to Fig. 1-3 for institute's reference in the algorithm of the present invention for carrying out the chart that gray correction is used, as seen, divide class with the maximum gradation value M of reproduced image among the figure, different class are selected different weight scheme for use, the maximum gradation value of reproduced image is more little, and the minimal weight of selecting for use is more little.With reference to Fig. 4, the hardware circuit of realization algorithm of the present invention as shown in Figure 1.Circuit is made up of peak extraction circuit 1, decision circuitry 2, delay circuit 3, anti-checking gamma circuit 4, scrambler 5, data processing circuit 6 and umber of pulse treatment circuit 7, except peak extraction circuit 1, decision circuitry 2 and delay circuit 3 be the present invention peculiar, remaining circuit is the basic circuit of PDP.

Circuit is R, G, three kinds of Signal Processing similar process of B to red, green, blue, below only analyze red, i.e. R Signal Processing process.The peak extraction circuit is a comparer, R signal to neighbor compares, export bigger R signal, in a TV Field, continuous transmission along with the R signal, comparison procedure has experienced full-screen pixels, at last, what the peak extraction circuit was exported is exactly the maximum R signal of present image, be the maximum gradation value M of R signal, decision circuitry 2 selects weight scheme to remove controlled encoder 5 and umber of pulse treatment circuit 7 by table 2, simultaneously according to the size of M, select to quantize bit wide by table 3 and remove to control anti-checking gamma circuit 4, the peak extraction circuit needs could to extract maximum gradation value M in the field picture through a field time, and delay circuit 3 postpones a field time with rgb signal, makes the rgb signal that enters anti-checking gamma circuit corresponding according to the control signal that this calculates with decision circuitry, scrambler output is through the image encoded data, send into data processing circuit 6 and handle, the principle of work of circuit such as data processing circuit 6 and umber of pulse treatment circuit 7 and drive circuit 8 belongs to prior art, does not repeat them here.

In order to improve the reliability of circuit working, the peak extraction circuit is most important to the detection of maximum gradation value M.Unless be interfered, highlighted luminous single isolated pixel seldom appears in television image, highlighted light-emitting zone generally is one or more pixel clusters, based on such fact, M rounds the arithmetic mean of the top n maximum gradation value of a picture, between the N desirable 50～100, adopt the method that compares and sort on the circuit, one field picture signal is compared and sorts, extract the top n maximal value, its arithmetic mean is M.

Claims (4)

1. drive controlling method that strengthens low grey degree value picture details, the basic circuit that comprises plasma display panel (PDP), anti-gamma correction method, it is characterized in that, described bearing calibration, be meant dynamic anti-gamma correction method, this method increases the peak extraction circuit again on the basis of plasma display panel (PDP) basic circuit, decision circuitry and delay circuit and the special correcting circuit that constitutes, carrying out dynamic anti-γ proofreaies and correct, under the constant situation of the sub-number of fields order of plasma display panel (PDP), make quantification bit wide value reproduce the gradation loss that hangs down gray-value image to reduce with the adaptive change of the peak brightness of reproduced image.

2. drive controlling method according to claim 1 is characterized in that, the peak extraction circuit in the described special correcting circuit is a comparator circuit, and adjacent plain mutually signal is compared.

3. drive controlling method according to claim 1 is characterized in that, described decision circuitry is the size according to maximum gradation value M, selects weight scheme to remove controlled encoder and umber of pulse treatment circuit.

4. drive controlling method according to claim 1 is characterized in that, described delay circuit is with signal delay one field time, makes that to enter anti-checking gamma circuit signal corresponding according to the control signal that this calculates with decision circuitry.

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