CN1512256A - Automatic exposure sampling and control method for image shooting device - Google Patents

Abstract

The present invention discloses automatic exposure sampling and controlling method for image shooting device. The pre-viewing range is separated into several automatic exposing and sampling windows and the brightness data of several evaluated points is taken; and through weight calculation of the brightness data to obtain maximum average brightness, minimum average brightness and averaged average brightness, calculation the differences between the target brightness and the maximum average brightness, the minimum average brightness and the averaged average brightness, substituting the differences in gain integration controlling operation, the regulation direction may be obtained; and based on the regulation direction, the gain values of aperture, electronic shutter and digital unit are obtained for the effective exposure regulation of great pixel number photosensitive coupling module or CMOS sensor.

Description

Image intake device automatic exposure sampling and control method

Technical field

The present invention relates to a kind of Image intake device automatic exposure control method, be applicable to dynamically and static Image intake device automatic exposure sampling and control, be particularly conducive to the automatic exposure control of the optical sensor of high picture element.

Background technology

Handle and paid attention to by the people along with the progress of multimedia technology and digital image, Image intake device (for example digital camera) also replaces traditional camera gradually, and provides the user can the fast browsing shooting results and add the function of borne computer fast.

Figure 1 shows that known Image intake device 100 frameworks, image is from lens 102 and aperture 104 and deliver to photosensitive device 106, as charge-coupled device (CCD) (CCD) or cmos sensor, and through behind automatic gain control 108 (AGC), promptly simulate and deliver to a system controller 110 to digital converter 112 and handle via one, and deliver to simultaneously a video converter 116 with output NTSC or PAL signal to the TV terminal, or output LCD signal to LCD screen is watched for the user.This system controller 110 is to do an evaluation of estimate computing according to the signal that is received, and the evaluation of estimate that calculates is delivered to an integral control action unit (PI control) 118.These integral control action unit 118 output control signal Δ gain to automatic exposure controllers 114 with to aperture 104, photosensitive device 106 and automatic gain control 108, are controlled evaluation of estimate is done feedback.

As everyone knows, the pacing items of taking photograph attractive in appearance is for focusing on and control suitable exposure, especially when taking continuous photograph or photography, because focus and light quantity continue to change, therefore need real-time and effective automatic exposure and focus control, to shoot desirable picture.Image intake device can be controlled three kinds of parameters for the adjustment of exposure value and carry out: (1) adjusts the size of aperture; (2) adjust electronic shutter; And the control of (3) adjustment automatic gain, wherein adjusting electronic shutter is to apply different bias voltages at charge-coupled device (CCD), how much to determine stored charge, picks up between the light time with control, reaches the effect of similar camera shutter.

Yet in above-mentioned three kinds of exposure adjustment mechanism, aperture size, electronic shutter control and automatic gain control are all the curve of nonlinear Control, therefore technique known usually is to set wherein two kinds of three kinds of parameters earlier according to the pattern (phototaking mode) of taking, and then remaining parameter is adjusted.Yet,, not necessarily have best exposure adjustment therefore only for a kind of parameter adjustment because the environment of photography may can't be preset in advance.

Another kind of known mode is the numerical value of time domain (time domain) mode and allowable error, does the optimization adjustment at f-number, electronic shutter value and digital gain, and its step is as follows:

(1). do photometry earlier to obtain the ambient light illumination respective value, calculate allowable error;

(2). poor according to desired value and allowable error determines suitable adjustment direction;

(3). converse the value of f-number, electronic shutter value and digital gain.

Yet in above-mentioned adjustment mode, owing to must do the calculating of exposure value to the picture element of whole charge-coupled device (CCD), therefore in mode, if the picture element of Image intake device increases, the calculating of the picture element of whole charge-coupled device (CCD) being done exposure value is loaded down with trivial details work.Moreover aforesaid way is to adopt the time domain mode to calculate, and therefore needs more parameter.

Goal of the invention

So purpose of the present invention, being provides-Image intake device automatic exposure sampling and control method, can do exposure adjustment to big picture element photosensitive coupling component rapidly.

Above-mentioned purpose of the present invention is achieved in that and the invention provides a kind of Image intake device automatic exposure sampling and control method, comprises the following step;

(a) a previewing scope is divided into specific most automatic exposure sampling windows;

(b) on each window, obtain most and estimate some brightness;

(c), obtain most mean flow rates through the weight computing;

(d) count maximum mean flow rate, minimum average B configuration brightness, mean flow rate mean value;

(e) judge an object brightness and maximum mean flow rate, minimum average B configuration brightness, the difference of mean flow rate mean value;

(f) difference substitution gain integral control action according to this can be adjusted direction;

(g) release the value of aperture, electronic shutter and digital gain according to adjusting direction; And

(h) get back to step (a).

Image intake device automatic exposure sampling of the present invention and control method, wherein, it is relevant with the arithmetic capability of Image intake device that described step (b) obtains the number of estimating point.

Image intake device automatic exposure sampling of the present invention and control method wherein, if object brightness is between maximum mean flow rate and minimum average B configuration brightness, then stop computing.

With the sampling mode and the integral control action (PI control) of coupling Image intake device processor ability, can effectively do exposure adjustment to big picture element photosensitive coupling component.

Description of drawings

Fig. 1 is an Image intake device Organization Chart;

Fig. 2 is a process flow diagram of the present invention; And

Fig. 3 illustrates the sampling of the present invention for window.

Embodiment

In Fig. 1 to Fig. 3 of the present invention, relate to following element: Image intake device 100, lens 102, aperture 104, charge-coupled device (CCD) 106, automatic gain control 108, system controller 110, simulate to digital converter 112, automatic exposure controller 114, video converter 116, integral control action unit 118.

See also Fig. 2, method of the present invention comprises the following step:

S100: the previewing scope is divided into specific automatic exposure sampling window;

S102: on each window, obtain several and estimate some brightness;

S104:, obtain this several mean flow rates through the weight computing;

S106: count the most peaceful equal brightness, minimum average B configuration brightness, mean flow rate mean value;

S108: judge object brightness and maximum mean flow rate, minimum average B configuration brightness, the difference of mean flow rate mean value;

S110: difference substitution gain integral control action according to this, can adjust direction;

S112: release the value of aperture, electronic shutter and digital gain according to adjusting direction;

S114: get back to step S100.

Referring to Fig. 3, way of the present invention is the automatic exposure sampling window (S100) that the previewing scope is divided into given number n, get the sampling spot of given number then for each window, calculate the evaluation point brightness (S102) of this sampling spot again, the sampling spot number is relevant with the ability of the inner microprocessor of Image intake device.Then, obtain this several mean flow rates (S104) through the weight computing,

${\mathrm{Avg}}_k=f\left(k\right)=\frac{\underset{i=0}{\overset{X}{\mathrm{\Σ}}}\underset{j=0}{\overset{Y}{\mathrm{\Σ}}}{W}_{\mathrm{ij}}}{X*Y}$

Then calculate maximum mean flow rate Max (Avg _k), minimum average B configuration brightness Min (Avg _k), mean flow rate mean value AverageY and allowable error Tolerance (S106), wherein

$\mathrm{AverageY}=\frac{\underset{k=0}{\overset{n}{\mathrm{\Σ}}}{\mathrm{Avg}}_k}{n}$

Tolerance＝Max(Avg _k)-Min(Avg _k)

Calculated maximum mean flow rate Max (Avg _k), minimum average B configuration brightness Min (Avg _k), behind mean flow rate mean value AverageY and the allowable error Tolerance, judge object brightness Targety and maximum mean flow rate, minimum average B configuration brightness, the difference of mean flow rate mean value (S108), difference substitution gain integral control action according to this, can adjust direction (S110), wherein integral control action is to use parameter K c and τ 1, and S=TargetY-AverageY, and its expression is as follows

$G_{C\left(S\right)}=\mathrm{Kc}(1+\frac{1}{{\mathrm{\τ}}_{l}S})$

If object brightness TargetY is at maximum mean flow rate Max (Avg _k) and minimum average B configuration brightness Min (Avg _k) between, then represent the plain mutually maximum mean flow rate Max (Avg that is produced in this previewing scope _k) and minimum average B configuration brightness Min (Avg _k) scope that defined can include object brightness TargetY, then stop the integral control action that gains, and calculate aperture.The value (S112) of electronic shutter and digital gain

Gc(s)＝g(iris，tv，gain)

In sum, Image intake device automatic exposure sampling of the present invention and control method can be done at mutually plain greatly photosensitive coupling component and effectively expect automatic exposure sampling and control, can save operation time, and can be with two the parameter K c and the τ of gain integration control _lAnd mark brilliance control automatic exposure behavior.

The above only is specific embodiments of the invention, but scope of the present invention is not limited thereto, and therefore any personnel that are familiar with this technology are in the field of the invention, and variation of being implemented or modification all covered in the claim of the present invention.

Claims (3)

1, a kind of Image intake device automatic exposure sampling and control method is characterized in that, comprise the following step:

(a) a previewing scope is divided into specific most automatic exposure sampling windows;

(b) on each window, obtain most and estimate some brightness;

(c), obtain most mean flow rates through the weight computing;

(d) count maximum mean flow rate, minimum average B configuration brightness, mean flow rate mean value;

(e) judge an object brightness and maximum mean flow rate, minimum average B configuration brightness, the difference of mean flow rate mean value;

(f) difference substitution gain integral control action according to this obtains to adjust direction;

(g) release the value of aperture, electronic shutter and digital gain according to adjusting direction; And

(h) get back to step (a).

2, Image intake device automatic exposure sampling as claimed in claim 1 and control method is characterized in that, it is relevant with the arithmetic capability of Image intake device that described step (b) obtains the number of estimating point.

3, Image intake device automatic exposure sampling as claimed in claim 1 and control method is characterized in that, if object brightness is between maximum mean flow rate and minimum average B configuration brightness, then stop computing.

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