JP2010072283A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make a focus and exposure accurately follow a movement and a brightness change of a subject, even in rapid continuous shooting. <P>SOLUTION: Mirror-down is executed after picking up an image in the first frame, and a face is recognized in an obtained image data. An face area is predetermined, and a brightness of the area is obtained from the image data. A division photometric area corresponding to the face area is extracted based on coordinate data of the face area, and a brightness of the area is obtained from the image data. Then, an accumulation time of a photometric sensor is found based on the image brightness of the extracted division photometric area, for photometry in the second frame executed after the mirror-down. Exposure calculation is carried out based on an obtained photometric brightness after the photometry in the second frame, and exposure values (diaphragm value, exposure time) are determined to pick up an image in the second frame. The same manner is repeated hereafter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus capable of continuous shooting.

  When continuous shooting is performed with a camera, it is necessary to perform photometry, exposure calculation, focus detection, and focus adjustment (lens driving) for each frame, taking into account luminance changes and subject movement during continuous shooting. In particular, in a single-lens reflex camera, mirror down and mirror up operations are required in addition to the above operations.

  In recent years, there are cameras capable of high-speed continuous shooting of 10 frames per second. 10 frames / second means that the time per frame is only 0.1 seconds. If the time required for mirror up / down, lens drive, and imaging is subtracted, focus detection, photometry, and calculation based on the results are performed. There is very little time available for processing. For this reason, when importance is attached to the high speed of continuous shooting, exposure and focus cannot follow changes in brightness and subject movement, and there is a risk that photos with poor exposure and out of focus may be mass-produced. On the other hand, if importance is attached to the followability of exposure and focus, high-speed continuous shooting cannot be realized.

  There is a camera described in Patent Document 1 as a camera for preventing exposure failure during continuous shooting. This is because the first frame in continuous shooting is imaged with exposure based on the output of the finder photometric sensor, and the second and subsequent frames are obtained from the photometric value obtained from the image data of the first frame and the latest image data. The exposure is determined using the photometric value or the like, and imaging is performed with the exposure. In this case, since the output of the finder photometric sensor is not used for the second and subsequent frames, it is not necessary to raise and lower the mirror between imaging, and exposure failure can be suppressed to some extent even when high-speed continuous shooting is performed.

JP 2006-180239 A

  As described above, in the camera of Patent Document 1, exposure control of the next frame is performed using the photometric value obtained from the most recent image data during continuous shooting. Even if the photometric value obtained from the most recent image data is used, It can be said that it is old photometric data from the time of imaging of the next frame. With the method of Patent Document 1 in which photometry by the photometric sensor is not performed after the second frame, it is not possible to effectively prevent poor exposure during continuous shooting. Further, Patent Document 1 does not mention measures against blurring during high-speed continuous shooting.

An image pickup apparatus according to the present invention includes a light metering / exposure calculation unit that performs photometry when the mirror is down and performs an exposure calculation based on a photometry result, and an image pickup unit that performs image pickup based on the result of the exposure calculation and generates image data. An image pickup device that performs continuous shooting in order of repeating photometry, exposure calculation, mirror up, imaging, and mirror down when the continuous shooting mode is set, and recognizes an area where a specific subject exists in the image data Recognizing means, and the photometry / exposure calculating means performs photometry and / or exposure calculation for the second and subsequent frames in continuous shooting based on the recognition result of the image recognizing means for the image data generated immediately before. To do.
An imaging apparatus according to another invention includes a focus detection unit capable of detecting a focus when the mirror is down, a focus adjustment unit that performs focus adjustment based on a result of the focus detection, an imaging unit that performs imaging and generates image data, Is an imaging device that performs continuous shooting in order of repeating focus detection, focus adjustment, mirror up, imaging, and mirror down when the continuous shooting mode is set, and recognizes a region where a specific subject exists in image data An image recognizing unit is provided, and the focus adjusting unit performs the focus adjustment for the second and subsequent frames of continuous shooting based on the recognition result of the image recognizing unit with respect to the image data generated immediately before.

  According to the present invention, even in high-speed continuous shooting, focus and exposure can be made to accurately follow the movement of a subject and changes in luminance.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a configuration diagram of a single-lens reflex digital camera according to the present embodiment. The camera includes a camera body 100 and an interchangeable lens 200 that can be attached to and detached from the camera body 100 via a lens mount 100a. During imaging standby, a part of the subject light flux that has passed through the photographing optical system 201 of the interchangeable lens 200 is reflected by the main mirror 101 and observed through the pentaprism 102 and the eyepiece 103. Further, a part of the incident light beam to the pentaprism 102 is guided to the photometric unit 104. The photometry unit 104 includes a charge accumulation type photometry sensor 104a (FIG. 2), and as shown in FIG. 3, the entire screen is divided into 20 rectangular areas and photometry is performed, and a luminance signal of each area is output.

  On the other hand, a part of the subject luminous flux passes through the main mirror 101, is reflected by the sub mirror 105, and is guided to the distance measuring unit 106 (focus detection unit). The distance measuring unit 106 includes a charge accumulation type AF sensor 106a (FIG. 2), and performs focus detection by a known phase difference detection method. In the present embodiment, as shown in FIG. 4, thirteen focus detection areas (focus areas) are set in the screen, and focus detection signals for each area can be acquired.

  When imaging is instructed, the mirrors 101 and 105 are raised, and the subject luminous flux enters the imaging element 108 via the optical filter 107. The image sensor 108 photoelectrically converts incident light and outputs it as an image signal. Reference numeral 109 denotes an external liquid crystal (liquid crystal monitor) provided on the back surface of the camera body 100, and 110 denotes a finder liquid crystal for performing in-finder display.

  The interchangeable lens 200 is provided with a focus motor 202 and an aperture unit 203 that drive the focus optical system.

FIG. 2 is a block diagram showing a control system of the camera.
The imaging signal output from the imaging element 108 is corrected by the DFE 1, processed by the image processing unit 2, and then recorded in the image storage unit 3 as image data. The image processing unit 2 also reads out the image data in the storage unit 3 and displays it on the external liquid crystal 109 in the reproduction mode.

  The system control unit 5 controls the image processing unit 2, the shutter control unit 7, the mirror control unit 8, the photometry control calculation unit 9, the distance measurement control calculation unit 10, and the like. The photometric control calculation unit 9 performs an exposure calculation based on the output of the photometric sensor 104a, and obtains an aperture value, an exposure time (accumulation time of the image sensor 108) and the like for imaging the subject with appropriate exposure. The distance measurement control calculation unit 10 performs a focus adjustment calculation based on the output of the AF sensor 106a, and obtains a lens driving amount for focusing the photographing optical system 201 on the subject.

  SW1 is a half-push switch that is turned on by half-pressing the release button, SW2 is a full-push switch that is turned on by full-pressing the release button, 12 is an information setting unit for setting shooting information, and 13 is a driver 14. An image pickup control unit that controls the image pickup device 108 via the image pickup unit 15, a buffer 15 for temporarily storing image data, and a power supply unit 16 for supplying power to each unit.

  The system control unit 5 can communicate with the lens control unit 22 of the interchangeable lens 200 via the communication interfaces 11 and 21. The lens control unit 22 drives the aperture unit 203 via the aperture control unit 23 based on an instruction from the system control unit 5 and focuses via the focus drive control unit 24 based on the calculated lens drive amount. The motor 202 is driven and controlled. By driving the focus motor 202, the focus optical system 201a of the photographing optical system 201 is driven to perform focus adjustment. Reference numeral 25 denotes a lens data storage unit for storing data relating to the lens.

Next, control in the continuous shooting mode will be described.
The camera of this embodiment can perform high-speed continuous shooting (for example, 10 frames / second). In consideration of luminance change during continuous shooting and movement of the subject, imaging preparation processing including photometry, exposure calculation, focus adjustment calculation, and lens driving is performed for each frame in continuous shooting.

  First, the imaging preparation process is performed for imaging the first frame, and the mirror is raised to perform imaging. Image data obtained by imaging is once stored in the buffer 15. Thereafter, an imaging preparation process is performed in preparation for imaging of the next frame. In order to perform the imaging preparation process, it is necessary to guide light to the photometric sensor 104a and the AF sensor 106a. For this purpose, the mirror must be returned to the down position once. . However, it takes a certain amount of time for the mirror to reach the down position from the mirror down instruction, and in the conventional control, no arithmetic processing can be performed during that time. In the present embodiment, processing for the next imaging preparation operation is performed using the time until the mirror reaches the down position.

  This process is based on the premise of taking a picture of a person. After imaging the first frame, the mirror is lowered and face recognition is performed on the image data stored in the buffer. Face recognition is a technique for recognizing a region occupied by a face when a human face is present in image data as is well known. FIG. 5 shows an example of a face recognition result. Face areas for three people are specified, and coordinate data of each face area is obtained. When the face area is recognized, it may be determined that the main subject is a person, the exposure is determined based on the brightness of the face area so that the person's face is properly exposed, and the face area is set to one of the face areas. Focus adjustment control may be performed so that focus is achieved.

First, exposure will be described.
When the face area is specified, the brightness of the area is obtained from the image data. In the present embodiment, as shown in FIG. 6, the luminance of each area can be obtained by dividing the image data into 12 areas.
Hereinafter, in order to clearly distinguish the luminance obtained from the image data from the luminance obtained from the output of the photometric sensor 104a, the former is called image luminance and the latter is called photometric luminance.

  Based on the coordinate data, the image brightness of the region corresponding to the face region is obtained from the 12 regions. FIG. 7 shows an example using the face recognition result of FIG. 5, and the image brightness of three areas surrounded by a bold line is obtained. Further, the extracted area is applied to the divided photometric area of the photometric sensor 104a, and a divided photometric area corresponding to the face area is extracted. FIG. 8 shows an example using the face recognition result of FIG. 5. Three regions surrounded by a thick line are extracted from the 20 divided photometric regions, and the image brightness of these regions is determined. In the next photometry, the photometric brightness of the extracted divided photometry area may be obtained.

  Next, in preparation for photometry of the second frame performed after mirror down, the accumulation time of the photometry sensor 104a as a photometry control parameter is obtained based on the extracted image brightness of the divided photometry area. Here, the accumulation time is short for high luminance and needs to be longer for low luminance.However, since the luminance of the subject is not known beforehand in normal metering, the accumulation time is set to an appropriate value for accumulation. If it is inappropriate, the operation of changing the accumulation time and accumulating again is repeated. In the present embodiment, the divided photometry area to be metered and the image brightness corresponding to the area are known from the immediately preceding image data. Therefore, the second frame has few photometry by setting the accumulation time accordingly. The number of accumulations, that is, the possibility of completion in a short time is high.

  After the second photometry, an exposure calculation is performed based on the obtained photometric brightness, and an exposure value (aperture value, exposure time) is determined. Normally, the exposure value is determined in consideration of the photometric luminance of the 20 divided photometric areas, but here only the photometric luminance of the extracted divided photometric areas (3 areas in the example of FIG. 8) needs to be considered. Therefore, the exposure calculation is completed in a shorter time than usual. Thereafter, the second frame is imaged based on the calculated exposure value.

In this way, the divided photometry area to be used is determined based on the information obtained from the face recognition result of the immediately preceding imaging data, and the accumulation time in the next photometry is obtained based on the luminance of the divided photometry area. The process of obtaining the photometric brightness by performing photometry and obtaining the exposure value based on the photometric brightness is similarly performed from the third frame onward. According to this, since the second frame and later, both photometry and exposure calculation are completed in a shorter time than usual, it is possible to realize high-speed continuous shooting that is rich in follow-up to changes in subject brightness. In addition, since photometry is performed by the photometry sensor 104a every time an image is taken, the follow-up capability with respect to a change in luminance is higher than that in the case of performing photometry only at the beginning as in Patent Document 1.
Here, since the arithmetic processing from the face recognition to the accumulation time setting can be performed in synchronization with the mirror down, these processes do not affect the frame speed.

Next, focus adjustment during continuous shooting will be described.
In the second and subsequent frames of continuous shooting, a focus detection area corresponding to the face area recognized in the immediately preceding image data is extracted. FIG. 9 shows an example using the face recognition result of FIG. 5, in which three focus detection areas indicated by bold lines are extracted. After the mirror is down, the focus detection result of the extracted focus detection area is acquired, and the focus adjustment calculation is performed based on them to obtain the lens drive amount, and the lens is driven. Normally, the focus adjustment calculation is performed in consideration of the focus detection results of all 13 regions. However, since only the focus detection results of the extracted regions need to be considered here, the focus adjustment is completed in a short time. Accordingly, high-speed continuous shooting is possible while keeping the focus following the movement of the subject person. Further, since the face recognition and the focus adjustment calculation can be performed in synchronization with the mirror down, these processes do not affect the frame speed.

FIG. 10 is a flowchart showing an example of a procedure for realizing the above control in software.
When the half-push switch SW1 is turned on in the continuous shooting mode, the system control unit 5 performs the above-described imaging preparation process, and then, when the full-push switch SW2 is turned on, activates the program of FIG. In steps S1 and S2, photometry and exposure calculation are performed again. In step S3, a mirror up instruction is issued. In step S4, the process waits for the mirror up to be completed. In step S5, imaging is performed based on the result of the exposure calculation, and the obtained image data is temporarily stored in the buffer 15.

  In step S6, a mirror down instruction is issued, and in step S7, it is determined whether or not the full-press switch SW2 is kept on. If negative, each image data stored in the buffer 15 in step S8 is recorded in the image storage unit 3, and the process is terminated.

  If step S7 is affirmed, face recognition processing is performed on the image data temporarily stored in step S9. In step S10, it is determined whether or not a face area has been recognized. If not, the process proceeds to step S15 to perform normal continuous shooting. When the face is recognized, the process proceeds to step S11, where a divided photometry area corresponding to the face area is extracted and the image brightness of the area is acquired. In step S12, the accumulation time in the next photometry is calculated based on the image brightness. Set. Details of these processes are as described above.

  In step S13, a focus detection area corresponding to the face area is extracted. When it is confirmed in step S14 that mirror down has been completed, focus detection is performed in step S15, and focus adjustment (focus adjustment calculation, lens drive) is performed in step S16. As described above, when the face area is recognized, the extraction result in step S13 is reflected in the focus adjustment calculation. Thereafter, the process returns to step S1.

  Although face recognition is performed every time shooting is performed, face recognition is performed only on the first image data, and the face pattern obtained by the first face recognition is applied to the image data obtained thereafter. The movement of the face may be tracked by template matching as a template, and the result may be reflected in the next photometry, exposure calculation, and focus adjustment calculation. Alternatively, the object that is regarded as the main subject may be tracked only by template matching without using face recognition, and in this case, the present invention can be applied to other than human photographing. In addition, the main subject may be tracked using image recognition techniques such as color distribution analysis, frequency analysis, and edge analysis.

The block diagram of the single-lens reflex type digital camera in one Embodiment of this invention. The control block diagram of the said camera. The figure which shows the division | segmentation photometry area | region in an imaging | photography screen. The figure which shows the focus detection area | region in an imaging | photography screen. The figure which shows an example of a face recognition result. The figure which shows the division | segmentation condition of the luminance detection with respect to image data. The figure which shows the state which extracted the area | region corresponding to a face area from the division area of FIG. 6 based on the face recognition result of FIG. The figure which shows the state which extracted the area | region corresponding to a face area | region from the division | segmentation photometry area | region of FIG. 3 based on the face recognition result of FIG. The figure which shows the state which extracted the area | region corresponding to a face area | region from the focus detection area | region of FIG. 4 based on the face recognition result of FIG. The flowchart which shows an example of the operation | movement at the time of continuous shooting mode.

Explanation of symbols

2 Image processing unit 5 System control unit 101 Main mirror 104a Photometric sensor 106a AF sensor 108 Image sensor

Claims (5)

Photometric / exposure calculation means for performing photometry when the mirror is down and performing exposure calculation based on the photometry result, and imaging means for performing image pickup based on the result of the exposure calculation and generating image data, and continuous shooting mode At the time of setting, in the imaging device that performs continuous shooting that repeats photometry, exposure calculation, mirror up, imaging, mirror down in order,
Image recognition means for recognizing a region where a specific subject exists in image data;
The photometry / exposure calculation means performs photometry and / or exposure calculation for the second and subsequent frames of the continuous shooting based on a recognition result of the image recognition means for the image data generated immediately before. apparatus.   The photometry / exposure calculation means includes a photometry unit including a photometry element, and a calculation unit that obtains the luminance of an area where the specific subject exists from the image data, and obtains a control parameter in the next photometry based on the obtained luminance 2. The imaging apparatus according to claim 1, wherein photometry for the second and subsequent frames of the continuous shooting is performed based on the control parameter obtained for the image data generated immediately before. . A focus detection unit capable of detecting a focus when the mirror is down, a focus adjustment unit that performs focus adjustment based on a result of the focus detection, and an imaging unit that performs imaging and generates image data, and sets a continuous shooting mode. Sometimes, in an imaging device that performs continuous shooting that repeats focus detection, focus adjustment, mirror up, imaging, and mirror down in order,
Image recognition means for recognizing a region where a specific subject exists in image data;
The focus adjustment means includes a control means for performing focus adjustment for the second and subsequent frames of the continuous shooting based on a recognition result of the image recognition means for the image data generated immediately before. apparatus.   The focus adjustment unit has an extraction unit that extracts a focus detection region corresponding to a region recognized by the image recognition unit from a plurality of preset focus detection regions, and the focus after the second frame of the continuous shooting The imaging apparatus according to claim 3, wherein the adjustment is performed on the image data generated immediately before based on a focus detection result of the extracted focus detection region.   5. The image pickup apparatus according to claim 1, wherein the image recognition by the image recognition unit is performed in synchronization with a mirror down operation after image pickup.

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