CN101282416A - Method for displaying projection - Google Patents

Abstract

The invention provides a projection display method, which can perform dynamic adjustment to projection display contrast according to brightness of the image signal, comprising steps: receiving a image signal; analyzing brightness of the image signal; computing optimal modified value of brightness and modifying the image signal according to the optimal modified value; computing light source brightness correction value and adjusting brightness of the projection light source according to the light source brightness correction value. The projection display method of the invention adjusts brightness of the projection light source according to color greyscales of the projection displayed image, which also corrects the image in order to ensure that greyscale of the image will not be reduced following the brightness reduction of the light source, thereby lowering power consumption and improving dynamic contrast.

Description

Method for displaying projection

Technical field

The present invention relates to a kind of method of handling image, relate to a kind of method that is used for improving picture contrast more specifically in Projection Display.

Background technology

Along with the raising day by day of living standard and the continuous development of video technique, the projection video product also more and more causes the concern in market.At present, no matter be that portable small-business demonstration, multimedia conferencing chamber, classroom, stadiums, church, commercial location, large-scale auditorium all may use the projection video product, some virtual demonstration even need use especially to the jumbotron optical projection system of cinema greatly.They otherwise adopt before the throwing mode, or adopt the rear-projection mode.Throwing before so-called, briefly, is exactly the installation site and the homonymy of spectators at screen of projector equipment, and the ray cast that projector equipment sends arrives screen, forms image on screen, and light reflexes to eye more then.The preceding screen of throwing can be made arbitrary dimension, and the advantage of preceding throwing is only to throw screen before one, can do very greatly, just as the screen of cinema.

The projector equipment of new type light source has appearred adopting in recent years, adopt the red, green, blue three primary light source as projection light source, can select all solid state laser, semiconductor laser or light-emitting diode, not only solve life-span, power problems, can also export abundanter full color.Yet the effect of projector equipment is subjected to the influence of surround lighting bigger, and for example, when surround lighting was brighter, the image of projector equipment seems can be darker, and therefore, the image effect that improves projector equipment is that this field needs the problem that solves always always.And contrast is an important indicator of display device, and it just has influence on the image quality of device displayed image.(as UHP: there is the lower defective of contrast in projector equipment ultrahigh pressure mercury lamp etc.) (as LCD, DLP, LCoS projector) based on traditional projection light source at present.Therefore, a kind of method that improves the projector equipment contrast is badly in need of in this area.

Summary of the invention

In order to address the above problem, the invention provides a kind of method for displaying projection, comprise step: receive picture signal; Brightness to picture signal is analyzed; Calculate the best correction value of brightness, picture signal is revised according to the best correction value of brightness; Calculate the light-source brightness corrected value, the brightness of projection light source is adjusted according to the light-source brightness corrected value.

Above-mentioned method for displaying projection calculates the best correction value of described brightness according to the high-high brightness of described picture signal.According to the high-high brightness computed image gray scale correction factor of described picture signal, the brightness of picture signal is revised according to described gradation of image correction factor.If the light source high-high brightness is the value of described picture carrier 255 correspondences, and described picture signal high-high brightness is L _MAX, then the light source high-high brightness is adjusted into L _MAXThe brightness value of brightness correspondence.If described picture signal maximum brightness value is L _MAX, minimum luminance value is L _MIN, described gradation of image correction factor is:

$\mathrm{\β}=\frac{(255-L_{\mathrm{MAX}})-255L_{\mathrm{MIN}}+{L_{\mathrm{MAX}}}^2}{L_{\mathrm{MAX}}(L_{\mathrm{MAX}}-L_{\mathrm{MIN}})}$

The brightness histogram statistics of above-mentioned picture signal and weighted-average method are calculated the best correction value of described brightness.According to the brightness histogram statistics and the weighted-average method computed image gray scale correction factor of described picture signal, picture signal is revised according to described gradation of image correction factor.Described best correction value is calculated by following formula and is obtained:

$L_M=\frac{N_0}{N_{\mathrm{ALL}}}{L}_0+\frac{N_1}{N_{\mathrm{ALL}}}{L}_1+\frac{N_2}{N_{\mathrm{ALL}}}{L}_2+\·\·\·\·\·\·+\frac{N_{255}}{N_{\mathrm{ALL}}}{L}_{255}$

Wherein Nx is that image gray levels is the number of picture elements of X, and Lx is the light-source brightness of corresponding gray scale correspondence.Described gradation of image correction factor is:

$\mathrm{\β}=\frac{255}{L_M}$

Method for displaying projection of the present invention is adjusted the brightness of projection light source according to the versicolor gray scale of the image of Projection Display, for the reduction with light-source brightness of the gray scale that guarantees displayed image reduces, also image is revised, thereby reached the reduction power consumption, improve the purpose of dynamic contrast.

Description of drawings

Figure 1 shows that the schematic diagram of a projector.

Figure 2 shows that the schematic diagram of the embodiment of a projector of the present invention.

Figure 3 shows that the schematic diagram of the embodiment of a controller.

Embodiment

In order to make those skilled in the art person understand the present invention program better, and above-mentioned purpose of the present invention, feature and advantage can being become apparent more, is example with the projector below, and the present invention is further detailed explanation with embodiment in conjunction with the accompanying drawings.

Figure 1 shows that the schematic diagram of a projector.As shown in the figure, projector 100 comprises lighting device 110, optic modulating device 120, imaging device 130 and screen 140.During projector 100 operate as normal, lighting device 110 produces illuminating bundles, and illuminating bundle enters optic modulating device 120 after treatment.Optic modulating device 120 mainly is made up of light valve device and drive circuit thereof, can adopt LCoS (liquid crystal on silicon), light valve devices such as LCD, DLP.Optic modulating device 110 is through the light modulation device, with the light modulation of red, green, blue three primary colors is polarization state or bright, the dark state (as to DLP) that displaying contents conforms to, then by the color-combination prism composograph, by imaging device 130 (for example projection lens is first-class) synthetic image is outputed to screen at last.

Figure 2 shows that the schematic diagram of the embodiment of a projector of the present invention.Different with projector 100, projector 200 also comprises controller 250 except comprising lighting device 210, optic modulating device 220, imaging device 230 and screen 240.Controller 250 can be an asic chip, also can be a programmable device FPGA or CPU, a DSP or CPLD or the like.As shown in the figure, controller 250 connects lighting device 210 and optic modulating device 220.Controller 250 can be analyzed the image that needs show, according to the image high-high brightness that analyzes or other statistical informations, after computing, obtain light source drive signal (if any the pwm signal or the current level signal of corresponding duty ratio), deliver to lighting device 210, make the high-high brightness of three primary light source also become analog value.For the display frame brightness that guarantees projector's 200 outputs does not reduce, image RGB data are also adjusted accordingly simultaneously, adjusted signal and deliver to optic modulating device 220.By such adjustment, make the brightness of light source just to brighten or deepening with the gray scale numerical value of display image, it is many so just to make that the more static light source of brightness of details in a play not acted out on stage, but told through dialogues has reduced, thereby has improved the optical projection system contrast; In addition, reduce the average power consumption of optical projection system, reached purpose of energy saving.

Figure 3 shows that the schematic diagram of an embodiment of controller 250.As shown in the figure, controller 250 comprises signaling interface 310, front-end processing module 320 and image processing module 330.

During controller 250 operate as normal, signaling interface 310 receives picture signal and the image signal transmission that receives is arrived front-end processing module 320.Front-end processing module 320 is converted to a unified format with picture signal, and the data with consolidation form are input to image processing module then, and image processing module 330 is started working.The consolidation form here can be rgb format, also can be yuv format or the like.

Image processing module 330 comprises memory 340 and brightness normalization coefficient module 350.The view data of the consolidation form that front-end processing module 320 is sent is deposited in memory 340, view data also is admitted to brightness normalization coefficient module 350 simultaneously, 350 pairs of figure signals of brightness normalization coefficient module carry out analytical calculation, determine the brightness normalization coefficient of a present image signal, the brightness normalization coefficient also can be referred to as the best correction value of brightness.The computational methods of the best correction value of brightness can comprise multiple mode, for example can adopt and get the brightness maximum value process, and be that gradation of image is the brightness value of 255 correspondences as original light source brightness, and the maximum gray scale of image is L _MAX, then the light source high-high brightness is adjusted into gray scale L _MAXCorresponding brightness value perhaps adopts image brightness statistics with histogram and weighting to ask average method to obtain the brightness optimum value.Brightness normalization coefficient module 350 is sent the best correction value of brightness into memory 340 at last.

After the best correction value of the brightness that obtains present image, the gray scale of 330 pairs of picture signals of image processing module is adjusted.Suppose that the original image gray scale is L, after the light-source brightness correction, be adjusted into gradation of image L ' is corresponding:

L′＝βL

Wherein β is a corresponding gradation of image correction factor after the different brightness correction methods of employing, and the computational methods of gradation of image correction factor will describe in detail below.After adjustment was finished, image processing module 330 was delivered to 220 pairs of incident lights of optic modulating device with revised view data and is modulated.

At last, image processing module 330 is according to the best correction value of brightness, and optical attenuation ratio and gamma correction coefficient in the lighting device 210, imaging device 230 proofread and correct light-source brightness, obtains a light-source brightness corrected value, and the light-source brightness corrected value that obtains is sent into lighting device 210.Lighting device 210 carries out pulsewidth (PWM) or current-modulation by the light-source brightness corrected value of input to light source, to reach the purpose that light source is dynamically controlled.

Below to adopt the brightness maximum value process that the course of work of controller 250 is described:

Data-signal is transferred to front-end processing module 320 through signaling interface 310, and front-end processing module 320 converts view data to unified DVI form, then the data input picture processing module 330 of DVI form is started working.

Image processing module 330 control storages 340 storing image datas are sent into view data brightness normalization coefficient module 350 simultaneously, extract the brightness maximum as the brightness optimum value through the brightness extraction algorithm then.As the primary source high-high brightness is the value of gradation of image 255 correspondences, and the maximum gray scale of image is L _MAX, then the light source high-high brightness is adjusted into L _MAXThe brightness value of gray scale correspondence, image processing module 330 is sent the best correction value of brightness into memory 340.

Image processing module 330 is reads image data simultaneously, the DVI data is converted to the RGB data, and with the image correction algorithm gradation of image is adjusted.As original image gray scale L maximum is L _MAX, minimum value is L _MIN, then with the corresponding adjustment of gradation of image L ', it is constant to adjust the back minimum brightness, and high-high brightness is expanded as the brightness value before light-source brightness is adjusted, and amplifies through corresponding proportion, and correction factor is:

$\mathrm{\β}=\frac{(255-L_{\mathrm{MAX}})-255L_{\mathrm{MIN}}+{L_{\mathrm{MAX}}}^2}{L_{\mathrm{MAX}}(L_{\mathrm{MAX}}-L_{\mathrm{MIN}})}$

And revised image RGB data are converted to the DVI data and deliver to 220 pairs of incident lights of optic modulating device and modulate.

At last, image processing module 330 is according to the best correction value of brightness, and optical attenuation ratio and gamma correction coefficient in the lighting device 210, imaging device 230 are proofreaied and correct light-source brightness, obtain a control signal (for example pwm signal), at last this control signal is sent into lighting device 210, light source is modulated.

Below to adopt image brightness statistics with histogram and weighting to ask average method that the course of work of controller 250 is described:

Data-signal is transferred to front-end processing module 320 through signaling interface 310, and front-end processing module 320 converts view data to unified DVI form, then the data input picture processing module 330 of DVI form is started working.

Image processing module 330 control storages 340 storing image datas, simultaneously view data is sent into brightness normalization coefficient module 350,350 pairs of image brightness of brightness normalization coefficient module are carried out statistical disposition, count the image pixel gray scale in 0～255 distribution, ask average method to try to achieve corresponding gray scale optimum value through weighting

$L_M=\frac{N_0}{N_{\mathrm{ALL}}}{L}_0+\frac{N_1}{N_{\mathrm{ALL}}}{L}_1+\frac{N_2}{N_{\mathrm{ALL}}}{L}_2+\·\·\·\·\·\·+\frac{N_{255}}{N_{\mathrm{ALL}}}{L}_{255}$

Wherein Nx is that image gray levels is the number of picture elements of X, and Lx is the light-source brightness of corresponding gray scale correspondence.Image processing module 330 is with the L that obtains _MCorresponding light-source brightness optimum value is sent into memory 340.

Image processing module 330 is reads image data simultaneously, the DVI data is converted to the RGB data, and with the image correction algorithm gradation of image is adjusted.And gradation of image adjusted.As the original image gray value is L, then with the corresponding β L that is adjusted into of gradation of image L ',

$\mathrm{\β}=\frac{255}{L_M}$

And revised image RGB data are converted to the DVI form and deliver to 220 pairs of incident lights of optic modulating device and modulate.

At last, image processing module 330 is according to the best correction value of brightness, and optical attenuation ratio and gamma correction coefficient in the lighting device 210, imaging device 230 are proofreaied and correct light-source brightness, obtain a control signal (for example pwm signal), at last this control signal is sent into lighting device 210, light source is modulated.

Like this, control through controller 250 illumination apparatus 210 and optic modulating device 220, projector 200 adjusts the brightness of projection light source according to the versicolor gray scale of the image of Projection Display, for the gray scale that guarantees displayed image does not reduce with the reduction of light-source brightness, also image is revised, thereby reached the reduction power consumption, improved the purpose of dynamic contrast.

Certainly; above-mentioned explanation is not to be limitation of the present invention; the present invention also is not limited in above-mentioned giving an example, and variation, remodeling, interpolation or replacement that those skilled in the art are made in essential scope of the present invention also should belong to protection scope of the present invention.

Claims (10)

1, a kind of method for displaying projection comprises step:

Receive picture signal;

Brightness to picture signal is analyzed;

Calculate the best correction value of brightness, picture signal is revised according to the best correction value of brightness;

Calculate the light-source brightness corrected value, the brightness of projection light source is adjusted according to the light-source brightness corrected value.

2, method for displaying projection according to claim 1 is characterized in that: described method for displaying projection calculates the best correction value of described brightness according to the high-high brightness of described picture signal.

3, method for displaying projection according to claim 2 is characterized in that: according to the high-high brightness computed image gray scale correction factor of described picture signal, according to described gradation of image correction factor the brightness of picture signal is revised.

4, method for displaying projection according to claim 3 is characterized in that: if the light source high-high brightness is the value of described picture carrier 255 correspondences, and described picture signal high-high brightness is L _MAX, then the light source high-high brightness is adjusted into L _MAXThe brightness value of brightness correspondence.

5, method for displaying projection according to claim 4 is characterized in that: if described picture signal maximum brightness value is L _MAX, minimum luminance value is L _MIN, described gradation of image correction factor is:

$\mathrm{\β}=\frac{(255-L_{\mathrm{MAX}})-255L_{\mathrm{MIN}}+{L_{\mathrm{MAX}}}^2}{L_{\mathrm{MAX}}(L_{\mathrm{MAX}}-L_{\mathrm{MIN}})}.$

6, method for displaying projection according to claim 1 is characterized in that: brightness histogram statistics and weighted-average method according to described picture signal are calculated the best correction value of described brightness.

7, method for displaying projection according to claim 6, it is characterized in that:, the brightness of picture signal is revised according to described gradation of image correction factor according to the brightness histogram statistics and the weighted-average method computed image gray scale correction factor of described picture signal.

8, method for displaying projection according to claim 7 is characterized in that: the best correction value of described brightness is calculated by following formula and is obtained:

$L_M=\frac{N_0}{N_{\mathrm{ALL}}}{L}_0+\frac{N_1}{N_{\mathrm{ALL}}}{L}_1+\frac{N_2}{N_{\mathrm{ALL}}}{L}_2+\·\·\·\·\·\·+\frac{N_{255}}{N_{\mathrm{ALL}}}{L}_{255}$

Wherein Nx is that image gray levels is the number of picture elements of X, and Lx is the light-source brightness of corresponding gray scale correspondence.

9, method for displaying projection according to claim 8 is characterized in that: described gradation of image correction factor is:

$\mathrm{\β}=\frac{255}{L_M}.$

10, according to the arbitrary described method for displaying projection of claim 1-10, it is characterized in that: described method for displaying projection comprises step: described figure signal is carried out format conversion.

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