CN101489050B - Automatic exposure control method - Google Patents

Automatic exposure control method Download PDF

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Publication number
CN101489050B
CN101489050B CN 200810002368 CN200810002368A CN101489050B CN 101489050 B CN101489050 B CN 101489050B CN 200810002368 CN200810002368 CN 200810002368 CN 200810002368 A CN200810002368 A CN 200810002368A CN 101489050 B CN101489050 B CN 101489050B
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brightness value
value
main body
background area
body object
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CN 200810002368
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CN101489050A (en
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黄思华
钟镇远
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Altek Corp
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Altek Corp
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Abstract

The present invention discloses an automatic exposure control method for controlling a shooting exposure parameter of a shooting image at a shooting end. The method comprises: acquiring at least one middle luminance value between the luminance value of a background zone and an integral luminance value, orderly judging a relation of a flash lamp operation distance individually corresponding to the luminance value of the background zone, the middle luminance value and the integral luminance value and a main body actual distance from the luminance value of the background zone to the integral luminance value, obtaining the shooting exposure parameter and selectively starting the flash lamp to adjust the integral luminance of the shooting image, thereby obtaining the image with a proper integral luminance.

Description

Automatic exposure control method
Technical field
The present invention relates to a kind of camera technique, relate in particular to a kind of automatic exposure control method.
Background technology
At present, the overall brightness of the image of gained is determined by exposure parameters such as film speed progression, f-number and time for exposure during photographic images.And an exposure parameter is corresponding to a brightness value.When taking an object under backlight, the image of gained has brighter part and darker part.When the brightness of background area is brighter, can make that the brightness of main body object area is darker relatively, that is the luminance contrast of background area and main body object area can be bigger.And because the high brightness contrast of main body object area and background area, therefore when adjusting brightness value the main body object area is brightened, but it is brighter to make simultaneously that also original brighter background area brightness becomes, after causing the background area overexposure to determine that the main body object area has phenomenon backlight, measure the main body object area to the actual range (step 40) of taking end.At this, actual range is the distance between the main body thing entity of taking end and main body object area, can obtain by the focusing frame.
Just do not influence background area brightness because adjust brightness value, also influence the brightness of main body object area, therefore when the adjustment brightness value brightens the background area, the main body object area also will brighten, and adjust when making the background area deepening, and the main body object area is also with deepening.
U.S. Pat 6859618 is under the situation of not adjusting brightness value, only by the control of photoflash lamp with the compensated corpus object area, yet may be because of the restriction of photoflash lamp working range, cause photoflash lamp can't reach the main body object area, cause luminance shortage, if can be via adjusting brightness value and photoflash lamp control exposure parameter, with the Expected Results that more can reach by the brightness of photoflash lamp compensated corpus.
Summary of the invention
The object of the present invention is to provide a kind of automatic exposure control method, to solve the existing problem that can't obtain the image of suitable overall brightness of known technology.
To achieve these goals, the invention provides a kind of automatic exposure control method, it can access more suitable overall brightness by the adjustment of the brightness value reinforcement with the control photoflash lamp, allows the brightness of background and object obtain preferable adjustment.
According to the embodiment of the invention, a kind of automatic exposure control method is taken the shooting exposure parameter that end is taken an image in order to control, wherein image is made of a main body object area and a background area, comprise the information that the main body of image object area and background area are provided, obtain the main body object area brightness value, background area brightness value and by the brightness value of main body object area and the overall brightness value that brightness value synthesized of background area.Judge that according to the brightness value of main body object area and the brightness value of background area the main body object area has phenomenon backlight then, measure the main body object area again to the actual range of taking end, then the brightness value with the background area is an initial value, obtain at least one median luminance value in regular turn toward the overall brightness value, obtain a corresponding exposure parameter by median luminance value then, calculate the operating distance of photoflash lamp again according to exposure parameter.The operating distance of and then judging photoflash lamp is greater than actual range, and the median luminance value that will meet determining step at last is as adjusting brightness value, and obtains the corresponding exposure parameter as taking exposure parameter and starting photoflash lamp according to adjusting brightness value.
In sum, by technological means of the present invention, can judge whether phenomenon backlight according to the brightness value of adjusting, and then in the photoflash lamp operating distance, force under the prerequisite of complement sudden strain of a muscle, obtain more suitable overall brightness, allow the brightness of background area and main body object area obtain preferable adjustment.
Describe the present invention below in conjunction with the drawings and specific embodiments, but not as a limitation of the invention.
Description of drawings
Fig. 1 is the method flow diagram of the automatic exposure control method of one embodiment of the invention;
Fig. 2 A and Fig. 2 B are the monochrome information schematic diagram of one embodiment of the invention; And
Fig. 3 is that the brightness value of one embodiment of the invention concerns schematic diagram.
Wherein, Reference numeral:
The BV brightness value
BV 1The brightness value of background area
BV 2The overall brightness value
BV 3Median luminance value
BV 3-1First median luminance value
BV 3-2Second median luminance value
Embodiment
Please refer to Fig. 1, be the method flow diagram of automatic exposure control method according to an embodiment of the invention.As shown in Figure 1, this automatic exposure control method is taken the shooting exposure parameter that end is taken an image in order to control.Wherein image is made of a main body object area and a background area.At this, main body object area and background area are meant and present the zone of main body thing and the zone of background in plane pictures.
At first provide the main body object area of image and the information of background area (step 10), then obtain the main body object area brightness value, background area brightness value and by the brightness value of main body object area and the overall brightness value (step 20) that brightness value synthesized of background area.
Then judge that according to the brightness value of main body object area and the brightness value of background area the main body object area has phenomenon backlight (step 30) again.
After determining that the main body object area has phenomenon backlight, measure the main body object area to the actual range (step 40) of taking end.At this, actual range is the distance between the main body thing entity of taking end and main body object area, can obtain by the focusing frame.
Brightness value with the background area is an initial value then, obtains at least one median luminance value (step 50) in regular turn toward the overall brightness value.Obtain the brightness value of background area and the median luminance value between the overall brightness value in order between the brightness value of background area and overall brightness value, to find the appropriate brightness value, to obtain the image that suitable exposure parameter is taken the photograph.
Obtain corresponding exposure parameter (step 60) by median luminance value afterwards.Calculate the operating distance (step 70) of photoflash lamp again according to exposure parameter,
And the operating distance of judging photoflash lamp is greater than actual range (step 80).
To meet at last the operating distance of judging photoflash lamp greater than the median luminance value of actual range (step 80) as adjusting brightness value, obtain the corresponding exposure parameter as taking exposure parameter and starting photoflash lamp (step 90) according to adjusting brightness value.
The operating distance of photoflash lamp can be calculated by following formula.
FWD = GN / FN × ( ISOspeed / 100 )
Wherein, FWD represents the photoflash lamp operating distance, and GN (G number) represents the photoflash lamp coefficient, and FN represents f-number, and ISOspeed represents film speed progression.Weight distribution with Fig. 2 B is made weighted average to overall diagram 2A, can get an overall weight average gray value WG, an overall brightness value BV 2Then can be by formula: Log 2(WG) try to achieve.
Thus formula as can be known, different exposure parameters has different photoflash lamp operating distances.
Please refer to Fig. 2 A and Fig. 2 B, illustrate that the present invention obtains the specific embodiment of monochrome information.Shown in Fig. 2 A, at first image obtains an overall gray value distribution map by a known background area and a main body object area information, the gray value of background area partly represented in the ㄇ font of gray value 100 among the figure, and the part of other parts gray value 10 is the gray value of main body object area.Gray value is calculated and is got by the formula that comprises three primary colors information, and this zone of the more little representative of gray value is dark more.
Please arrange in pairs or groups with reference to figure 2B, it represents main body object area and the background area weight distribution figure that is done under the effect backlight, among the figure main body object area weight is made as 20, and the background area is made as 10, yet in fact can does different weight arrangements with regard to different situations.
Weight distribution with Fig. 2 B is made weighted average to the background area of Fig. 2 A, can get a background weighted average gray value BG, and the brightness value BV of a background area 1Can be by Log 2(BG) try to achieve.
Weight distribution with Fig. 2 B is made weighted average to overall diagram 2A, can get an overall weight average gray value WG, an overall brightness value BV 2Then can be by formula: Log 2(WG) try to achieve.
Similarly, the weighted average gray value of main body object area and brightness value also can be tried to achieve by preceding method.
And it is whether backlight promptly by the brightness value BV of background area 1Whether the brightness value that deducts the main body object area is greater than a threshold value judge.
Please refer to Fig. 3, for the brightness value of one embodiment of the invention concerns schematic diagram.As shown in Figure 3, wherein include several brightness values BV, several median luminance value BV 3Brightness value BV between the background area 1With overall brightness value BV 2Between.Wherein, median luminance value BV 3Obtain and be brightness value BV in the background area 1With overall brightness value BV 2Between obtain the median luminance value BV of specific quantity with equidistant or specific range variation 3Or at the brightness value BV of background area 1With overall brightness value BV 2Between obtain the median luminance value BV of fixed qty 3, be about to the brightness value BV of background area 1With overall brightness value BV 2Between the M equal portions, M is the positive integer more than or equal to 2.For convenience of description, only draw brightness value BV among Fig. 3 with the background area 1With overall brightness value BV 2Between the state of 10 equal portions.Then obtain an exposure parameter, calculate pairing photoflash lamp operating distance according to the pairing exposure parameter of comparison brightness value then by the comparison brightness value.
And then photoflash lamp operating distance and the actual range that relatively calculates, when photoflash lamp operating distance during more than or equal to actual range, with the comparison brightness value of correspondence as adjusting brightness value.
Will be according to aforementioned formula by the brightness value BV of background area 1Toward overall brightness value BV 2Obtain the photoflash lamp operating distance of the pairing exposure parameter of a comparison brightness value in regular turn, and with the judgement of making comparisons of itself and actual range.For example: the brightness value BV that obtains the background area earlier 1The photoflash lamp operating distance of pairing exposure parameter and with the judgement of making comparisons of itself and actual range is if it when not meeting pairing photoflash lamp operating distance more than or equal to the condition of actual range, then continues down to obtain the first median luminance value BV 3-1, if it when not meeting pairing photoflash lamp operating distance more than or equal to the condition of actual range, then continues down to obtain one second median luminance value BV 3-2, and continue to judge the relation of its pairing photoflash lamp operating distance and actual range, up to find meet the photoflash lamp operating distance more than or equal to the brightness value of actual range till or determine overall brightness value BV 2In other words, when meeting pairing photoflash lamp operating distance more than or equal to the condition of actual range, then with the comparison brightness value of correspondence as adjusting brightness value and stopping the judgement of follow-up brightness value; And as the brightness value BV of background area 1With all median luminance value BV 3During neither meeting, that is can't obtain the exposure parameter of adjusting brightness value the time, the exposure parameter that then adopts the overall brightness value is for taking exposure parameter and with overall brightness value BV 2As adjusting brightness value.
When adjusting brightness value that brightness value is the background area or median luminance value, then start photoflash lamp.When the adjustment brightness value is the overall brightness value, that is the exposure parameter of employing overall brightness value is when taking exposure parameter, then not start photoflash lamp.
Obtain the shooting exposure parameter that comprises a film speed progression, a f-number and a time for exposure according to adjusting brightness value at last.
That is to say, when the comparison brightness value is that the photoflash lamp operating distance of the brightness value of background area or median luminance value and its pairing exposure parameter is during more than or equal to actual range, represent the main body thing entity of main body object area can be subjected to the reinforcement of photoflash lamp, therefore will be with this comparison brightness value as adjusting brightness value, and with its pairing exposure parameter as taking exposure parameter and starting photoflash lamp, and then can be according to resulting shooting exposure parameter, the photoflash lamp that glimmers simultaneously captures image.In addition, when the comparison brightness value is that the photoflash lamp operating distance of overall brightness value and its pairing exposure parameter is during more than or equal to actual range, serve as to adjust brightness value then with this comparison brightness value, and with its pairing exposure parameter as taking exposure parameter, though but the main body thing entity of its main body object area can be subjected to the reinforcement of photoflash lamp, so do not start photoflash lamp owing to body region has had enough brightness.
Just, under the situation that photoflash lamp effectively operates, select low exposure parameter collocation photoflash lamp to operate and carry out capturing images, so that the background area and the main body object area of the image of obtaining can both have suitable brightness.
In sum, can effectively utilize the adjustment of brightness value and find suitable overall brightness and by technological means of the present invention via of the reinforcement of the photoflash lamp operating distance of judging the pairing exposure parameter of each brightness value with the control photoflash lamp, therefore allow the brightness of background and object can both obtain preferable adjustment and compensation, improve the quality of photographic images, thoroughly solve the problem of known technology.
Certainly; the present invention also can have other various embodiments; under the situation that does not deviate from spirit of the present invention and essence thereof; those of ordinary skill in the art work as can make various corresponding changes and distortion according to the present invention, but these corresponding changes and distortion all should belong to the protection range of the appended claim of the present invention.

Claims (8)

1. an automatic exposure control method is taken the shooting exposure parameter that end is taken an image in order to control one, it is characterized in that, comprising:
The main body object area of this image and the information of background area are provided;
Obtain this main body object area brightness value, this background area brightness value and by the brightness value of this main body object area and the overall brightness value that brightness value synthesized of this background area;
Judge that according to the brightness value of this main body object area and the brightness value of this background area this main body object area has phenomenon backlight;
Measure the actual range of this main body object area to this shooting end;
Brightness value with this background area is an initial value, obtains at least one median luminance value in regular turn toward this overall brightness value;
Obtain a corresponding exposure parameter by this median luminance value;
Calculate an operating distance of a photoflash lamp according to this exposure parameter;
This operating distance of judging this photoflash lamp is greater than this actual range; And
This median luminance value that will meet this determining step is adjusted brightness value as one, obtains a corresponding exposure parameter according to this adjustment brightness value and takes exposure parameter as this, and start this photoflash lamp;
Wherein, the adquisitiones of the overall brightness value of this image comprises: the intensity profile that obtains general image; The intensity profile of this general image is made weighted average and obtained a general image weighted average gray value; And with log 2The formula of (general image weighted average gray value) is tried to achieve this overall brightness value;
Wherein, judge that step backlight comprises: the intensity profile that obtains the information of this image subject object area information and this background area respectively; Weighted average is made respectively in main body object area information and this background area and obtain a main body object area weighted average gray value and a background area weighted average gray value respectively; And with log 2(background area weighted average gray value)-log 2The value of (main body object area weighted average gray value) judges that greater than a threshold value phenomenon backlight is arranged.
2. automatic exposure control method according to claim 1 is characterized in that, when obtaining the median luminance value that meets aforementioned determining step when adjusting brightness value as one, then adopts this overall brightness to be worth an exposure parameter to be this shooting exposure parameter.
3. automatic exposure control method according to claim 2 is characterized in that, this exposure parameter that adopts this overall brightness value does not start this photoflash lamp during for this shooting exposure parameter.
4. automatic exposure control method according to claim 1 is characterized in that the weight of the brightness value of this main body object area is greater than the weight of the brightness value of this background area.
5. automatic exposure control method according to claim 1 is characterized in that, this exposure parameter comprises a film speed progression, a f-number and a time for exposure.
6. automatic exposure control method according to claim 5 is characterized in that, this operating distance of this photoflash lamp is tried to achieve according to this f-number of this median luminance value correspondence and a photoflash lamp coefficient of this photoflash lamp correspondence.
7. automatic exposure control method according to claim 1 is characterized in that, the step that obtains this median luminance value comprises: equidistant this median luminance value that obtains between the brightness value of this background area and this overall brightness value.
8. automatic exposure control method according to claim 1 is characterized in that, the step that obtains this median luminance value comprises: this median luminance value that obtains fixed qty between the brightness value of this background area and this overall brightness value.
CN 200810002368 2008-01-15 2008-01-15 Automatic exposure control method Expired - Fee Related CN101489050B (en)

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