The automatic exposure device of a kind of digital brightness gain and time for exposure collaborative work
Technical field
The present invention relates in the digital camera automatic exposure control field, relate in particular to the automatic exposure device of digital brightness gain and time for exposure collaborative work picture quality.
Background technology
Digital still images such as digital camera of the prior art, digital shadow stream are controlled the sensitometric curve that all is based on optical pickocff to the automatic exposure of image quality in using, and the time for exposure is long more, and the amplitude of image brightness gain is low more.Referring to Fig. 1, Fig. 1 is under the normal illumination condition, the image brightness statistical value (Y mean) that digital camera obtains from optical pickocff, with the graph of relation of the current time for exposure (Exposure Time) that optical pickocff is provided with, the gain range of image brightness reduces along with the increase of time for exposure.In addition, usually under fluorescent light,, must allow time for exposure of optical pickocff be 1/100 second integral multiple during Phase Alternation Line system, must allow time for exposure of optical pickocff be 1/120 second integral multiple during TSC-system in order to eliminate the flicker striped that sensor photosensitive produces.Therefore, the adjustment of time for exposure must be directly proportional with flicker cycle, and the time for exposure is the some gears that disperse.But automatic exposure control device of the prior art exists following problem: 1, the AE adjusting is unsmooth, and the sensitometric curve slope of optical pickocff is bigger; 2, under low light conditions, need constantly to increase the time for exposure obtaining small luminance gain, to the improvement of visual visibility not during skill; 3, cause the data frame per second to reduce significantly, destroyed digital shadow stream continuity.
Summary of the invention
In order to overcome the problems of the prior art and deficiency, the object of the present invention is to provide the automatic exposure device of a kind of digital brightness gain and time for exposure collaborative work.It makes and time for exposure and digital brightness gain collaborative work makes that the automatic exposure adjusting is more level and smooth.
In order to realize the foregoing invention purpose, technical scheme of the present invention realizes as follows:
The automatic exposure device of a kind of digital brightness gain and time for exposure collaborative work comprises automatic exposure control procedure unit, time for exposure control unit, other image signal processing units and interruption controls unit.Described other image signal processing units comprise a brightness statistic, the luminance component of each pixel of the view data that described brightness statistic scanning receives, and calculate the brightness statistics value of every frame image, feed back to automatic exposure control procedure unit by the interruption controls unit again.The time for exposure that described automatic exposure control procedure unit calculates renewal according to the brightness statistics value of gained and current time for exposure, described automatic exposure control procedure unit sends to be upgraded the time for exposure and instructs to described time for exposure control unit.Described time for exposure control unit acts on optical pickocff with new time for exposure parameter configuration, and described optical pickocff is gathered original image data under new time for exposure condition, and is translated into the pictorial data A of digital CFA form.Its design feature is, also comprise the digital brightness gain regulon, described optical pickocff is conveyed into the digital brightness gain regulon with view data A, the new gain parameter that the digital brightness gain regulon sends according to automatic exposure control procedure unit is carried out gain-adjusted to each pixel data of view data A and is changed pictorial data B in the adjustable extent of luminance gain.Described digital brightness gain regulon is transferred to other picture intelligence processing unit with view data B and further optimizes and combines, and finally is converted into the pictorial data of yuv format.
The adjustable extent of the digital brightness gain of above-mentioned digital brightness gain regulon is being successively decreased along with the increase of time for exposure.The adjustable extent of digital brightness gain can dispose by the characteristic parameter of time for exposure and optical pickocff.
The gain parameter of above-mentioned digital brightness gain regulon is N/M.N among the gain parameter N/M and M can regulate respectively.
Above-mentioned digital brightness gain regulon also comprises one when automatic exposure is in stable state, masks the screened circuit module of luminance gain function.
The present invention can also comprise synchronous control unit, described synchronous control unit starts the exposure frames counting number according to the synchronous mark that the time for exposure control unit sends, count results and automatic exposure control procedure unit are preset luminance gain to synchronous control unit to come into force and postpones frame number and compare, if reach the delay frame number, the control command that described synchronous control unit transmission brightness comes into force is to described digital brightness gain regulon.The luminance gain that described synchronous control unit sets in advance comes into force and postpones frame number and can regulate.
The new time for exposure gear that digital brightness gain regulon of the present invention sends according to automatic exposure control procedure unit carries out gain-adjusted to each pixel data of view data A and changes pictorial data B in the adjustable extent of luminance gain.Like this, when automatic exposure was regulated, between two time for exposure shelves, the digital brightness gain regulon had been regulated luminance gain, makes the adjusting of automatic exposure seem smoother.In addition, under low light conditions, automatic exposure control procedure unit of the present invention is according to current time for exposure gear and current image brightness statistical value, can in time judge the low-light (level) operating state, with the time for exposure locked at higher gear and guarantee the frame per second (Frame rate) of proper digital shadow stream (Digital video), regulate digital brightness gain parameter N and M simultaneously,, can fast and effeciently improve visual visibility such as increasing the N value or reducing the M value.Digital brightness gain parameter N and M can regulate respectively, have guaranteed the precision of computing like this, make that the adjusting of luminance gain is flexible more, the realization cost minimum of hardware.
Description of drawings
The sensitometric curve figure of optical pickocff in Fig. 1 prior art;
Fig. 2 is a structure principle chart of the present invention;
Fig. 3 is the structure principle chart of the preferred embodiment for the present invention;
Fig. 4 is the collaborative work curve chart of time for exposure of the present invention and digital brightness gain;
Fig. 5 is a workflow diagram of the present invention.
Below in conjunction with the drawings and specific embodiments the present invention is further specified.
Embodiment
Referring to Fig. 2, the automatic exposure device of a kind of digital brightness gain and time for exposure collaborative work comprises automatic exposure control procedure unit 1, time for exposure control unit 2, other image signal processing units 5 and interruption controls unit 6.Described other image signal processing units 5 comprise a brightness statistic 7, the luminance component of each pixel of the view data that described brightness statistic 7 scannings receive, and calculate the brightness statistics value of every frame image, feed back to automatic exposure control procedure unit 1 by interruption controls unit 6 again.The time for exposure that described automatic exposure control procedure unit 1 calculates renewal according to the brightness statistics value of gained and current time for exposure, described automatic exposure control procedure unit 1 sends to be upgraded the time for exposure and instructs to described time for exposure control unit 2.Described time for exposure control unit 2 acts on optical pickocff 3 with new time for exposure parameter configuration, and described optical pickocff 3 is gathered original image data under new time for exposure condition, and is translated into the pictorial data A of digital CFA form.The present invention also comprises digital brightness gain regulon 4, described optical pickocff 1 is conveyed into digital brightness gain regulon 4 with view data A, the new gain parameter that digital brightness gain regulon 4 sends according to automatic exposure control procedure unit 1, each pixel data of view data A is carried out gain-adjusted change pictorial data B in the adjustable extent of luminance gain, described digital brightness gain regulon 4 is transferred to other picture intelligence processing unit 5 with view data B and further optimizes and combines, and finally is converted into the pictorial data of yuv format.The adjustable extent of the digital brightness gain of described digital brightness gain regulon 4 is being successively decreased along with the increase of time for exposure.The adjustable extent of digital brightness gain can dispose by the characteristic parameter of time for exposure and optical pickocff.
Referring to Fig. 3, preferred implementation of the present invention is also to comprise synchronous control unit 9 on basis of the present invention, described synchronous control unit 9 starts the exposure frames counting number according to the synchronous mark that time for exposure control unit 2 sends, count results and automatic exposure control procedure unit 1 are preset luminance gain to synchronous control unit 9 to come into force and postpones frame number and compare, if reach the delay frame number, the control command that described synchronous control unit 9 transmission brightness come into force is to described digital brightness gain regulon 4.The luminance gain that above-mentioned synchronous control unit 9 sets in advance comes into force and postpones frame number and can regulate.Above-mentioned digital brightness gain regulon 4 also comprises one when automatic exposure is in stable state, masks the screened circuit module 8 of luminance gain function.
Referring to Fig. 4, anatomize digital brightness gain regulon 4 when the time for exposure changes, the process that luminance gain is mediated.All the time do not satisfy automatic exposure limit with the image brightness statistical value below, and to be lower than desired value be example.Automatic exposure limit refers to: current image brightness statistical value is in the stationary zones.Stationary zones depends on current time for exposure gear and optical pickocff characteristic parameter, can calculate flexibly.Analyze 0-1 for the curve chart among Fig. 4: the digital brightness gain minimum under the current time for exposure, on transfer to digital brightness gain peak under the current time for exposure; 1-2: the time for exposure is raised one grade, simultaneously digital brightness gain is reset to the minimum under the current time for exposure; 2-3: be equal to step 0-1; 3-4: be equal to step 1-2; 4-5: be equal to step 0-1; 5-6: be equal to step 1-2.By top analysis as can be seen, described digital brightness gain regulon 4 can be begun luminance gain under the current time for exposure by minimum, on transfer to luminance gain peak under the current time for exposure shelves; If at this moment the time for exposure raises, digital brightness gain regulon 4 is reset to luminance gain minimum under the current time for exposure shelves with digital brightness gain simultaneously, and then on transfer to luminance gain peak under the current time for exposure shelves.
The adjustable extent of digital brightness gain is different at the different exposure time gear, under the normal illumination condition, successively decreases with the increase of time for exposure, can flexible configuration.
The gain parameter of above-mentioned digital brightness gain regulon 4 is N/M.N among the gain parameter N/M and M can regulate respectively.The correction of time for exposure, influence the brightness of pictorial data A of the original CFA form of optical pickocff output, the digital brightness gain regulating action is on each original pixels (Pixel) data, gain parameter N/M increases image brightness greater than 1, less than 1 minimizing image brightness, equal 1 and keep image brightness.Pictorial data B has embodied the synthesis of time for exposure control with the adjusting of digital brightness gain.Therefore under low light conditions, the adjusting of time for exposure gear can not increase image brightness timely and effectively, even the amplitude of the maximum adjustable scope of digital brightness gain (under the normal illumination condition) can not satisfy the needs that recover visual visibility under the low frame per second condition as early as possible.And by the present invention, can in time judge low-light (level) operating state (based on the relation of current time for exposure gear and current image brightness statistical value), with the time for exposure locked at higher gear and guarantee the frame per second (Frame rate) of proper digital shadow stream (Digital video), regulate digital brightness gain parameter N and M simultaneously, such as increasing the N value or reducing the M value, fast and effeciently improve visual visibility.In like manner, under high illumination conditions, also can realize automatic exposure, repeat no more here by of the present invention.Digital brightness gain parameter N and M separate setting in hardware circuit, be to guarantee operational precision, and hardware realizes that cost minimizes, the synergistic keys of factor such as control maximum flexibility.
Referring to Fig. 5, workflow of the present invention is as follows: 1) automatic exposure control procedure unit judges whether that according to brightness statistics value that receives and current time for exposure needs carry out automatic exposure and regulate; 2) if do not need to carry out the automatic exposure adjusting, exposure is regulated and is finished, and carries out automatic exposure if desired and regulates, time for exposure that calculating makes new advances and new gain parameter; 3) if the time for exposure increase, the digital brightness gain regulon is reset to minimum under the new time for exposure with digital brightness gain, if the time for exposure reduces, the digital brightness gain regulon is reset to peak under the new time for exposure with digital brightness gain, if the time for exposure is constant, then new digital brightness gain parameter is acted on the digital brightness gain regulon; 4) brightness statistics value with the view data B after the digital brightness gain adjusting sends to automatic exposure control procedure unit, and returns step 1).