CN101324722B - Method for adjusting liquid crystal display device backlight lightness and contrast - Google Patents
Method for adjusting liquid crystal display device backlight lightness and contrast Download PDFInfo
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- CN101324722B CN101324722B CN2007100749481A CN200710074948A CN101324722B CN 101324722 B CN101324722 B CN 101324722B CN 2007100749481 A CN2007100749481 A CN 2007100749481A CN 200710074948 A CN200710074948 A CN 200710074948A CN 101324722 B CN101324722 B CN 101324722B
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Abstract
The invention provides a method for adjusting the brightness of the backlight and the contrast of an LCD. The method comprises the steps as follows: 1. calculating the brightness distribution ratio of the pixels of an image; 2. calculating the parameters of the contrast coefficient and the brightness distribution uniformity according to the brightness distribution ratio, and calculating the backlight coefficient according to the contrast coefficient and the brightness distribution uniformity; and 3. controlling the backlight of the LCD display according to the backlight control ratio and calculating the contrast of images according to the contrast ratio. By adopting the technical proposal provided by the invention, a backlight strip lamp does not keep the constant brightness; instead, thebrightness of the strip lamp varies dynamically with the brightness of the image displayed. The power consumption of the strip lamp is reduced more efficiently, and the service life of the strip lampis improved. In addition, the image contrast is not a constant which is adjusted artificially; instead, the image contrast can be adjusted dynamically with the brightness of the images so as to show the details of the images better, and improve the hierarchy of the images.
Description
Technical field
The invention belongs to the display technique field, relate in particular to lcd technology.
Background technology
Existing backlight liquid crystal display substantially all is to work under certain fixing voltage and current, no matter image is bright dark, the luminous intensity of pipe backlight can not change to some extent, so power invariability of its consumption, and when dark picture, the higher luminous intensity of pipe backlight has increased waste of electric energy undoubtedly and has shortened the serviceable life of fluorescent tube, and picture contrast is determined by the physical characteristics of liquid crystal display also simultaneously, can't carry out dynamic adjustments.
For addressing the above problem, the method of some dynamic adjustments liquid crystal display device backlight illuminations is provided in the prior art, as the optical inductor bearing calibration of disclosed a kind of LCD auto brightness control in No. the 01121977.7th, the Chinese patent application, this method of adjustment comprises the following step at least: at first set up the corresponding scope table with the coupling of panel of LCD brilliance control of ambient brightness; Produce the input voltage signal by optical inductor; The input voltage signal is inputed to operational amplifier, produce and amplify signal; Then will amplify signal and input to voltage-controlled oscillator, produce output frequency; The corresponding scope of selection is provided, sets maximum, centre and minimum value; Contrast this at last and mate corresponding scope table, with this output frequency input microprocessor, and the brightness of output controlling signal to control and to proofread and correct this LCD backlight plate.This scheme is dynamically adjusted backlight illumination according to ambient brightness then by the residing ambient brightness of optical inductor perception LCD, can not reach the purpose according to display frame dynamic adjustments backlight illumination, and the effect that can realize is limited.Other method also exists computing comparatively complicated, the concrete problem such as have difficulties of using.
Summary of the invention
The method that the object of the present invention is to provide a kind of liquid crystal display device backlight lightness and contrast to adjust, the backlight and contrast that is intended to solve the LCD TV that exists in the prior art can not be according to the dynamic problem of adjusting of picture.
For achieving the above object, the technical solution used in the present invention is as follows:
The method that a kind of liquid crystal display device backlight lightness and contrast are adjusted, described method comprises the steps:
A, 0～255 gray level of a two field picture brightness is divided into impartial gray level interval, calculates described gray level interval proportion in described image, determine the Luminance Distribution ratio of described each pixel of image;
The root-mean-square value of b, the described Luminance Distribution ratio of calculating, with described root-mean-square value as the illuminance distribution parameter, calculate contrast rating according to described Luminance Distribution proportional meter, and according to described contrast rating and illuminance distribution calculation of parameter coefficient backlight;
C, according to the described backlight liquid crystal display brightness of described coefficient adjustment backlight, and determine that according to described Luminance Distribution ratio value Luminance Distribution in the described image is main zone, with described Luminance Distribution is that the contrast in main zone is heightened, and is that the contrast in the zone beyond the main zone is turned down with described Luminance Distribution.
Wherein step c also comprises:
Determine contrast rating according to described Luminance Distribution ratio value, guaranteeing to place the integral image contrast the highest under the undistorted prerequisite of image.
Describedly determine that according to described Luminance Distribution ratio value Luminance Distribution in the described image is main zone, with described Luminance Distribution is that the contrast in main zone is heightened, and is that the contrast in the zone beyond the main zone is turned down and is specially with described Luminance Distribution:
Determine the gamma curve of described Flame Image Process according to described Luminance Distribution ratio value, described LCD is adjusted the contrast of described image according to the gamma curve of described Flame Image Process.
Described LCD is the display of LCD TV.
The present invention overcomes the deficiencies in the prior art, adopt and at first the Luminance Distribution ratio of a two field picture is calculated, then the Luminance Distribution ratio data that is obtained is transferred to the microprocessor MCU of display device, carry out set computing, then provide coefficient backlight and contrast rating and respectively display device is carried out technical scheme backlight and contrast control, the brightness that makes backlight lamp tube no longer keep constant is constant, but according to the bright dark of shown picture and dynamic change, the more effective power consumption that reduced has also prolonged serviceable life of fluorescent tube; The steady state value that neither artificially regulate of picture contrast simultaneously, but dynamically adjust details (comprising dark details, bright details) better to present image, the stereovision of increase image by the bright dark degree of image.
Description of drawings
Fig. 1 is an embodiment of the invention process flow diagram;
Fig. 2 is the histogram of the described Luminance Distribution table of the embodiment of the invention, related operation and Luminance Distribution ratio correspondence;
Fig. 3 be the embodiment of the invention described low bright be the Luminance Distribution histogram and the corresponding gamma curve of main picture;
Fig. 4 be the embodiment of the invention bright in described be the Luminance Distribution histogram and the corresponding gamma curve of main picture;
Fig. 5 be the embodiment of the invention described highlighted be the Luminance Distribution histogram and the corresponding gamma curve of main picture.
Embodiment
Technical scheme provided by the invention is: at first the Luminance Distribution ratio of a two field picture is calculated, then the Luminance Distribution ratio data that is obtained is transferred to the microprocessor MCU of display device, carry out set computing, then provide coefficient backlight and contrast rating and carry out control backlight and contrast and gamma curve:
1, backlight control: the even situation according to image brightness distribution is calculated coefficient backlight, and when image brightness distribution was inhomogeneous, the coefficient backlight that calculates was corresponding less, according to the coefficient backlight that calculates backlight illumination was turned down; When image brightness distribution was even more, the coefficient backlight that calculates was big more, heightened backlight illumination is corresponding according to the coefficient backlight that calculates;
2, contrast control: the basis of contrast rating is in high brightness and the shared ratio of low-luminosity picture content, will guarantee in principle that whole luminance signals take LCD screen institute as far as possible can a gray-scale displayed level (get 5～250 leave certain space up and down do not overflow guaranteeing) but can not overflow, and is promptly guaranteeing to place the integral image contrast the highest under the undistorted prerequisite of image;
When the contrast of image is controlled, can control by gamma curve: according to the lightness distribution situation improve details than the contrast of many parts and reduce details than the contrast of small part to show detail section especially.
In order to make purpose of the present invention, technical scheme and advantage clearer,, the present invention is further elaborated below in conjunction with drawings and Examples.Should be appreciated that specific embodiment described herein only in order to explanation the present invention, and be not used in qualification the present invention.
The technical scheme flow process that the embodiment of the invention provides specifically comprises following step as shown in Figure 1:
1, calculates the Luminance Distribution ratio and the illuminance distribution parameter of each pixel of a two field picture;
At first, the brightness of one two field picture can be with 0～255 gray level expressing, be 16 equal portions with these 256 grade classification in the embodiment of the invention, be divided into one group to call each in the following text, represent with B1～B16 respectively, every equal portions comprise 16 gray levels, specific as follows: B1 comprises 0～15 gray level, B2 comprises 16～31 gray levels, B332～47 gray levels, and B4 comprises 48～63 gray levels, B5 comprises 64～79 gray levels, B6 comprises 80～95 gray levels, and B7 comprises 96～111 gray levels, and B8 comprises 112～127 gray levels, B9 comprises 128～143 gray levels, B10 comprises 144～159 gray levels, and B11 comprises 160～175 gray levels, and B12 comprises 176～191 gray levels, B13 comprises 192～207 gray levels, B14 comprises 208～223 gray levels, and B15 comprises 224～239 gray levels, and B16 comprises 240～255 gray levels.
Referring to Fig. 2, wherein, B
nCorresponding above-mentioned B1～B16 amounts to 16 groups (brightness section), C
nBe each brightness section corresponding gray, D
nBe each gray level shared ratio in entire image, E
nBe C
nWith D
nProduct, F
nBe D
nSquare.And defined parameters is as follows:
Ratio root mean square:
Be used for reflecting image brightness distribution homogeneity parameter;
2, according to the homogeneity calculation of parameter coefficient backlight and the contrast rating of Luminance Distribution ratio that calculates in the step 1 and Luminance Distribution;
Default constant: J=75, K=0.25, L=5, (experiment records, and can rationally set constant according to the practical adjustments effect) maximum brightness level mh:
(mh 〉=10), mh (reaction maximum brightness place rank) minimum brightness level ml:
(ml≤6), ml (reaction minimum brightness place rank) thereby, calculate
(1) coefficient backlight:
It is backlight that (wherein c is a contrast rating, b gets≤1) utilizes the image brightness distribution homogeneity to regulate, and when image brightness distribution was inhomogeneous, the j value was bigger, and coefficient so backlight is corresponding just less, and backlight illumination can be turned down; When image brightness distribution was even more, the j value was just less, thereby coefficient backlight is bigger, and backlight illumination is corresponding to be heightened.
(2) contrast rating:
Contrast rating is subjected to the influence of maximum brightness level and minimum brightness level, promptly is subjected to the influence of Luminance Distribution, and when whole image was the master with dark picture and highlighted picture, the mh-ml value was bigger, and contrast rating is less, guarantees that highlighted signal does not overflow; When picture with the intermediate luminance was the master, the mh-ml value was less, and contrast rating is bigger, increases substantially picture contrast.Before luminance signal multiply by contrast rating, also need to do the processing that present image brightness deducts Cml.
3, according to coefficient adjustment backlight illumination backlight; Adjust contrast according to contrast rating; Adjust gamma curve according to the Luminance Distribution ratio.
See also Fig. 3, below based on low bright, and the uneven picture of Luminance Distribution is analyzed:
From the intensity map we as can be seen, this picture major part is dark picture, bright part only accounts for considerably less ratio.
Processing backlight: brightness of image belongs to inhomogeneous state in this case, and variable j and c are bigger, coefficient backlight
Less, place lower brightness with backlight.
Contrast is handled: obtain respectively high brightness levels and low luminance level brightness En with the intensity level Bmh and the Bml that equal L, the value of getting mh and ml is got contrast rating
As shown in Figure 3, highest brightness is less than 5, mh＜16 then, i.e. mh-ml＜16, c〉1, contrast improves, and image brightness distribution is as shown in Figure 3 after contrast is handled.
Gamma curve: the contrast of brightness accounting example than small part (highlighted part) reduced according to Gn=J * Dn, the accounting example strengthens the slope increasing that promptly low highlights divides than the contrast of many parts, thereby thereby makes the brightness lifting of dark portion picture, contrast strengthen clear that details becomes.Though the contrast of highlighted part at this moment reduces the sacrificial section details,, almost can ignore, so this is to be fit to whole picture viewing effect because this part ratio that accounts for whole image seldom.
Based in bright, highlighted picture, it is similar to play method of adjustment and above-mentioned situation, as Fig. 4, shown in Figure 5.
From previous example we as can be seen, this algorithm is exactly the dynamic Luminance Distribution situation that detects every width of cloth picture, when detecting picture when being dark picture, dark picture is carried bright, backlight illumination reduces; When to detect picture be main with highlighted part, brightness is down expanded, improve the contrast of highlighted part, backlight illumination reduces, and makes the easier reproduction of luminance detail of highlighted picture; When the middle light branch of picture occupied the majority, the contrast that middle light is divided strengthened, and the depth feelings of whole image is strengthened, and backlight illumination reduces.When illuminance distribution is brightness ratios at different levels near 6.25% the time, coefficient b maximum then backlight, its value is 1, backlight lamp tube brightness is the highest.
The above only is preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of being done within the spirit and principles in the present invention, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.
Claims (4)
1. the method adjusted of liquid crystal display device backlight lightness and contrast is characterized in that described method comprises the steps:
A, 0～255 gray level of a two field picture brightness is divided into impartial gray level interval, calculates described gray level interval proportion in described image, determine the Luminance Distribution ratio of described each pixel of image;
The root-mean-square value of b, the described Luminance Distribution ratio of calculating, with described root-mean-square value as the illuminance distribution parameter, calculate contrast rating according to described Luminance Distribution proportional meter, and according to described contrast rating and illuminance distribution calculation of parameter coefficient backlight;
C, according to the described backlight liquid crystal display brightness of described coefficient adjustment backlight, and determine that according to described Luminance Distribution ratio value Luminance Distribution in the described image is main zone, with described Luminance Distribution is that the contrast in main zone is heightened, and is that the contrast in the zone beyond the main zone is turned down with described Luminance Distribution.
2. method according to claim 1 is characterized in that, wherein step c also comprises:
Determine contrast rating according to described Luminance Distribution ratio value, guaranteeing to place the integral image contrast the highest under the undistorted prerequisite of image.
3. method according to claim 1, it is characterized in that, describedly determine that according to described Luminance Distribution ratio value Luminance Distribution in the described image is main zone, with described Luminance Distribution is that the contrast in main zone is heightened, and is that the contrast in the zone beyond the main zone is turned down and is specially with described Luminance Distribution:
Determine the gamma curve of described Flame Image Process according to described Luminance Distribution ratio value, described LCD is adjusted the contrast of described image according to the gamma curve of described Flame Image Process.
4. method according to claim 1 is characterized in that, described LCD is the display of LCD TV.
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| CN103065159B (en) * | 2013-01-14 | 2015-09-09 | 合肥工业大学 | A kind of image classification method based on brightness and contrast |
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