CN202721740U - Automatic exposure compensation device of backlight type scenes in video imaging system - Google Patents

Abstract

The utility model relates to an exposure compensation device, especially discloses an automatic exposure compensation device of backlight type scenes in a video imaging system, and pertains to the technical field of image processing. According to the technical scheme provided in the utility model, the automatic exposure compensation device of backlight type scenes in a video imaging system comprises an image acquisition device for acquiring optical system images. The image acquisition device is connected with an image processor through an A/D convertor. The image processor is connected with the image acquisition device through an exposure logic control module. An image statistical device and a backlight mode detection compensation module are comprised in the image processor. According to the utility model, the advantage of simple and convenient operation is realized, the effectiveness and stability of exposure compensation can be improved, and the advantage of wide application range is realized.

Description

The automatic exposure compensation arrangement of backlight type scene in the video imaging system

Technical field

The utility model relates to a kind of exposure compensating device, and the automatic exposure compensation arrangement of backlight type scene in especially a kind of video imaging system belongs to the technical field that image is processed.

Background technology

In video imaging system, traditional automation exposure control (AEC) utilizes the mean flow rate of image and static exposure reference value compares.This but " gray scale world hypothesis " may cause the improper exposure under certain type of lighting condition, such as the improper exposure of the foreground object in situation backlight.The shooting of this scene can cause background too to become clear and the partially dark exposure abnormal conditions of main body usually.

Whether for fear of this problem, some camera has been equipped with the BLC pattern, allow the user selection scene backlight, whether manually activates the BLC function.But this manual operation brings inconvenience for some users, and is also unactual on Video Applications.

Summary of the invention

The purpose of this utility model is to overcome the deficiencies in the prior art, and the automatic exposure compensation arrangement of backlight type scene in a kind of video imaging system is provided, and it is simple to operation, improves validity and the stability of exposure compensating, wide accommodation.

The technical scheme that provides according to the utility model, the automatic exposure compensation arrangement of backlight type scene in the described video imaging system, comprise for the image acquisition device that gathers the optical system image, described image acquisition device links to each other with image processor by A/D converter, and image processor links to each other with image acquisition device by the exposure Logic control module; Comprise in the image processor that image statistics device and backlight mode detect compensating module.

Described image acquisition device comprises ccd image sensor or cmos image sensor.

Advantage of the present utility model: by output brightness mean value, Y after the image statistics device statistics _Ave, luminance deviation Y _StdAnd under-exposed pixel percentage P _UnderAverage brightness Y according to above-mentioned image _Ave, luminance deviation Y _StdCalculate and judge reference value Y _Ref, and by judging reference value Y _RefCompare with default upper threshold value, lower threshold value, gather the scene state of image to judge better image acquisition device, the scene state of described image is scene backlight or normal scene; When image acquisition device collection image is scene backlight, according to above-mentioned under-exposed pixel percentage P _UnderThe exposure target value of computed image carries out exposure compensating according to exposure target value to image, and gathers image so that image acquisition device carries out normal scene exposure under described exposure target value; Otherwise image acquisition device 504 carries out normal scene and gathers image.The utility model is simple to operation, can improve validity and the stability of exposure compensating, wide accommodation.

Description of drawings

Fig. 1 is the exposure compensating flow chart of existing backlight type scene.

Fig. 2 is the schematic diagram of the utility model image statistics device.

Fig. 3 is flow chart of the present utility model.

Fig. 4 is supplementary flow chart backlight in the utility model scene backlight.

Fig. 5 is structured flowchart of the present utility model.

Embodiment

The utility model is described in further detail below in conjunction with concrete drawings and Examples.

As shown in Figure 1, be the flow chart of existing automatic exposure compensation flow process 100, wherein, existing automation exposure control technology is based on the image brightness mean value of measurement, the static object value brightness that obtains to preset by comparing these mean values.Be specially: from step 102, image brightness mean value Y _AveMeasure by image statistics device 200, then in step 104, with image brightness mean value Y _AveCompare with default static object value; This detection is a kind of threshold trigger.That is to say, image statistics device 200 1 frames connect a frame geo-statistic and detect data, in case when statistics departed from the respective degrees of static object value, exposure control began to start; Described departure degree is measured control by default large threshold value, little threshold value.

Specifically, step 104 has determined that whether the average brightness measured and the absolute difference between the desired value brightness are greater than default large threshold values.If not greater than this threshold values, so to current finding a view adjustments of not carrying out exposing, existing automatic exposure compensation flow process 100 can continuation be carried out the next one by step 110 and is found a view.On the contrary, if by step 104, determined the average brightness Y that is recording _AveAnd having very large difference between the desired value brightness, so existing automatic exposure compensation flow process 100 can proceed to the auto-exposure control of step 106, the size and Orientation (increase and decrease) that comes calculation exposure to adjust.Step 108 can be with the average brightness Y that records after each adjustment in the step 106 _AveCompare with default little threshold values.In step 108, if new average brightness Y _AveWith the absolute difference of desired value brightness greater than default little threshold values, implementation method 100 can proceed to step 106 automatic exposure and further adjust exposure so.If new average brightness Y _AveWhen being less than or equal to default little threshold values with the absolute difference of desired value brightness, existing automatic exposure compensation flow process 100 can proceed to step 110 and carry out the next one and find a view.That is to say current average brightness Y _AveIf between a stable region thresholding, fluctuate, so to current the finding a view adjustment that there is no need to expose.The exposure compensating of this kind scene can cause background too to become clear and the partially dark exposure abnormal conditions of main body usually, therefore requires further improvement the automatic exposure compensation method.

Fig. 5 is system and device schematic diagram of the present utility model.The utility model comprises for the image acquisition device 504 that gathers optical system 502 images, described image acquisition device 504 links to each other with image processor 508 by A/D converter 506, and image processor 508 links to each other with image acquisition device 504 by exposure Logic control module 510; Comprise in the image processor 508 that image statistics device 200 and backlight mode detect compensating module; Optical system 502 is conventional optical imaging system, and the effect of optical system 502 and structure are known by the art personnel, no longer describes in detail herein.

Object is by optical system 502 imaging on imageing sensor 504 in the scene.Imageing sensor 504 can be ccd image sensor, also can be cmos image sensor.Imageing sensor 504 is processed into voltage analog signal to optical signalling, and analog-digital converter A/D converter 506 subsequently converts the output signal of imageing sensor 504 to digital signal, so that image processor subsequently 508 is further processed.Image processor 508 comprises that some necessary picture signals process, and such as, white balance, color interpolation, sharpening is processed, colour correction, and the processing such as denoising.In the utility model embodiment, the more important thing is that image processor 508 comprises two important modules: image statistics device 200 and backlight mode detect and compensating module.

For different scenes, described scene comprises scene backlight and normal scene, and output image collector 504 gathers the average brightness Y of image after image statistics device 200 statistics _Ave, luminance deviation Y _StdAnd under-exposed pixel percentage P _UnderBacklight mode detects compensating module according to the average brightness Y of above-mentioned image _Ave, luminance deviation Y _StdCalculate and judge reference value Y _Ref=Y _Std/ Y _Ave, and with described judgement reference value Y _RefCompare with default upper threshold value, lower threshold value, no as scene backlight to judge optical system 502; When optical system 502 is scene backlight, backlight mode detects compensating module according to above-mentioned under-exposed pixel percentage P _UnderThe calculation exposure desired value is to carry out exposure compensating according to exposure target value to the image that image acquisition device 504 gathers, by the required image of image/video output module 512 outputs; And with described exposure target value input exposure Logic control module 510, adjust the exposure setting of image acquisition device 504 by exposure Logic control module 510, described exposure setting comprises aperture size, aperture time etc., to pass through aperture size, aperture time etc. come control chart image-position sensor 504 to reach optimized scene exposure.

The automatic exposure compensation method of the utility model backlight type scene comprises the steps:

A, gather required image by image acquisition device 504, and with in the described image input picture counter 200, by the average brightness Y of output image after image statistics device 200 statistics _Ave, luminance deviation Y _StdAnd under-exposed pixel percentage P _Under

B, according to the average brightness Y of above-mentioned image _Ave, luminance deviation Y _StdCalculate and judge reference value Y _Ref=Y _Std/ Y _Ave, and with described judgement reference value Y _RefCompare with default upper threshold value, lower threshold value, gather the scene state of image to judge image acquisition device 504, the scene state of described image is scene backlight or normal scene;

C, when image acquisition device 504 gathers images and is scene backlight, according to above-mentioned under-exposed pixel percentage P _UnderThe exposure target value of computed image carries out exposure compensating according to exposure target value to image, and gathers image so that image acquisition device 504 carries out normal scene exposure under described exposure target value; Otherwise image acquisition device 504 carries out normal scene and gathers image.

Below by concrete analysis automatic exposure compensation method of the present utility model is described:

As shown in Figure 2: for the utility model when current the finding a view, image statistics device 200 can operating procedures 202 receives the brightness value of each pixel.Following formula is used in the calculating of the brightness value of red, green, blue three looks: brightness value=0.586* green glow+0.301* ruddiness+0.113* blue light.In step 204, for each width of cloth image, characterize to make up brightness histogram with bin value (bin number) and corresponding pixel count.For the ease of carrying out digitized processing, what at first will carry out is exactly the quantification of pixel brightness value.Among the utility model embodiment, after 8 of uses quantized, image brightness can be 0 to 255, altogether 256 brightness degrees.Carrying out after brightness value quantizes, one or continuous several brightness degree are defined as bin (bin), each bin value identifies with symbol n.The brightness degree number that comprises in each bin is uniform.That is to say, all gray scales all are averagely allocated to several bins.For example, if 256 bins have been used in 8 quantification, namely n=0～255 that is to say that each bin value comprises a gray scale, and the bin value namely is corresponding gray scale numbering.

There are 3 data to need to calculate in the simple brightness histogram in the image statistics device 200 in step 204.First statistics is average brightness Y _AveCalculating, namely the summation of pixel brightness value is divided by the sampled pixel number.Average brightness is in step 206, with formula

Calculate.In this formula, n represents bin value (pixel brightness level), p[n] be the number of pixels in this bin numbering.Second statistics is luminance deviation Y _Std, in step 208, can calculate with following formula, be specially: $Y_{\mathrm{std}}=\frac{{\∑}_{n=0}^{255}|n-Y_{\mathrm{ave}}|*p\left[n\right]}{{\∑}_{n=0}^{255}p\left[n\right]}$ Calculate.

In the utility model embodiment,

The main metric of ratio scene backlight as whether, i.e. Y _Ref=Y _Std/ Y _AveFor judging reference value.With Y _Ref=Y _Std/ Y _AveBe used for weighing the luminance contrast situation of image scene, scene contrast refers to the size of brightness tones scope in the scene, and the scene of high-contrast means that the scene brightness tone range is large, and luminance deviation is remarkable, the backlight type scene has then met the feature of high contrast scene well, so Y _Ref=Y _Std/ Y _AveThe ratio height represents that then possibility backlight is very large.

The 3rd statistics is under-exposed pixel percent value P _Under, it is in step 210, according to formula P _Under=N _Under/ N _TotalCalculate, wherein, N _TotalAll sampled pixel numbers of image, N _UnderIt is under-exposed sampled pixel number.Under-exposed pixel refers to its brightness value less than certain gray scale (DarkBin Threshold camera bellows cabinet threshold value), and in the brightness histogram of step 204, our with dashed lines has marked this gray scale.Under-exposed pixel percent value P _UnderThe calculating that is used to detect at backlight mode adaptivity exposure target value in the compensating module 400.Image statistics device 200 is the statistical means of image processing field routine, and personnel are known by the art, no longer describes in detail herein.

As shown in Figure 3: according to implementation method 300, two predefined threshold values are arranged, upper threshold value and lower threshold value are used for detecting scene backlight and enter/withdraw from the BLC pattern.Lower threshold value is always less than upper threshold value, and upper threshold value and lower threshold value arrange as required.

In step 304, the average brightness Y of image _AveWith luminance deviation value Y _StdObtain from image statistics device 200.Then with reference to judgment value Y _Ref=Y _Std/ Y _AveCan compare with upper threshold value in step 304.If with reference to judgment value Y _Ref=Y _Std/ Y _AveValue is greater than upper threshold value, and implementation method 300 can enter into step 310, and in step 310, current backlight mode state of finding a view can be set as very, and can calculate a required new exposure target value.If in step 304, judge judgment value Y _RefBe not more than upper threshold value, implementation method 300 will proceed to step 306.

In step 306, if Y _RefValue is not more than lower threshold value, and implementation method 300 can proceed to step 312.In step 306, if Y _RefValue is greater than lower threshold value, and implementation method 300 can proceed to step 308.

In step 308, the upper one backlight mode state of finding a view can be read from holder, and can be used as current further judgement of finding a view.In step 308, if the upper one backlight mode state of finding a view is shown as very, in other words, upper one scene of finding a view is backlight, and exposure mode is the BLC pattern, and 300 of implementation methods rest on 310.In step 308, if the upper one backlight mode state of finding a view is shown as vacation, in other words, last scene of finding a view is normal scene, and exposure mode is the normal exposure pattern, and implementation method 300 can proceed to step 312; Carry out the next one step of finding a view by step 314, wherein step 312 and 314 is normal exposure.

In step 310, current backlight mode state demonstration of finding a view is made as true, and exposure mode is BLC pattern 400, shown in chart 4.In step 312, current backlight mode state demonstration of finding a view is made as fictitious time, and just expression is not scene backlight at present.

Fig. 4 is the schematic flow sheet of compensation model 400 backlight under the scene backlight in the utility model.According to implementation method 300, after step 308 and/or step 304, if the standard of image statistics data fit detection backlight, implementation method 300 can be set as BLC pattern 400.According to BLC pattern 400, the under-exposed pixel percentage P in the under-exposed pixel percentage step 404 of backlight image 402 _UnderCalculated by image statistics device 200, and this percentage can be applied in the step 406.In step 406, an adaptability exposure target value can be calculated, and this exposure target value depends on the percentage of under-exposed pixel.Larger under-exposed pixel percentage means the larger exposure compensating of correct exposure needs of the backlight image that detects.Can find out adaptability exposure target value TG in the calculated curve of the adaptability exposure target value from step 406 _AdaptiveCalculate by P ∈ (P1, P2); Wherein in the step 406, P1, P2 and TG ₀, TG _MaxOptimize the design variables of calculated curve; P1 is the first under-exposed pixel percentage, and P2 is the second under-exposed pixel percentage, TG ₀Be exposure minimum value, TG _MaxBe the exposure maximum, under-exposed pixel percentage and exposure target value can consist of linear approximate relationship, and described linear relationship meets the rule of existing video imaging system.When obtaining under-exposed pixel percentage P _UnderAfter, can access required exposure target value, by exposure target value current figure is compensated, and image acquisition device 504 is adjusted control.

After calculating the adaptability exposure target value for the backlight image 402 that detects, implementation method 400 proceeds to step 408, exposes normally with required exposure target value in step 408.

The utility model is by the rear output brightness mean value of image statistics device 200 statistics, Y _Ave, luminance deviation Y _StdAnd under-exposed pixel percentage P _UnderAverage brightness Y according to above-mentioned image _Ave, luminance deviation Y _StdCalculate and judge reference value Y _Ref, and by judging reference value Y _RefCompare with default upper threshold value, lower threshold value, gather the scene state of image to judge better image acquisition device 504, the scene state of described image is scene backlight or normal scene; When image acquisition device 504 collection images are scene backlight, according to above-mentioned under-exposed pixel percentage P _UnderThe exposure target value of computed image carries out exposure compensating according to exposure target value to image, and gathers image so that image acquisition device 504 carries out normal scene exposure under described exposure target value; Otherwise image acquisition device 504 carries out normal scene and gathers image.The utility model is simple to operation, can improve validity and the stability of exposure compensating, wide accommodation.

Claims (2)

1. the automatic exposure compensation arrangement of backlight type scene in the video imaging system, it is characterized in that: comprise for the image acquisition device (504) that gathers optical system (502) image, described image acquisition device (504) links to each other with image processor (508) by A/D converter (506), and image processor (508) links to each other with image acquisition device (504) by exposure Logic control module (510); Comprise in the image processor (508) that image statistics device (200) and backlight mode detect compensating module.

2. the automatic exposure compensation arrangement of backlight type scene in the described video imaging system according to claim 1, it is characterized in that: described image acquisition device (504) comprises ccd image sensor or cmos image sensor.

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