JP2018113624A - Imaging apparatus and control method for imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus which implements high-speed consecutive imaging while tracking a subject while suppressing the time required for determining a focus position through auto-focusing.SOLUTION: An imaging apparatus comprises: read-out means which reads a signal out of an imaging element upon receiving an imaging starting instruction; detection means for detecting a subject from the signal that is read out by the read-out means; determination means for determining a region in which a signal is read out, on the basis of a detection result of the detection means; acquisition means which acquires an auto-focus evaluation value on the basis of the region that is determined by the determination means; and control means which calculates a driving amount for driving a lens from the auto-focus evaluation value acquired by the acquisition means and outputs a control signal for driving drive means. The detection means starts detecting the subject from a completely read-out signal before the read-out means completely reads out signals.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an imaging apparatus and a method for controlling the imaging apparatus, and more particularly to control of continuous focus imaging.

  Conventionally, when reading an image necessary for an autofocus evaluation value from an image sensor such as a CMOS image sensor, there is a technique for performing high-speed focus detection by reading at a speed faster than a normal reading speed of a still image or the like.

  For example, Patent Document 1 discloses a technique for performing high-speed focus detection by reading out only a pixel signal of a specific area from an effective pixel area from an image sensor and acquiring an autofocus evaluation value. Patent Document 2 discloses a technique for performing high-speed focus detection by reading a specific segmented region out of the segmented still image readout region before other segmented regions and acquiring an autofocus evaluation value. It is disclosed.

JP 2012-58464 A JP 2011-166515 A

  However, in the prior art disclosed in Patent Document 1, the entire effective pixel area is read to detect the subject, and the reading area for acquiring the autofocus evaluation value is determined. However, when reading the whole, a part without a subject is also read, and therefore, it is considered that useless reading time is consumed, and it takes time to obtain the result autofocus evaluation value.

  In the prior art disclosed in Patent Document 2, reading for obtaining an autofocus evaluation value is performed in parallel with reading of a still image. A read-out portion for acquiring the autofocus evaluation value is a specific partial area in a still-image read-out area divided in advance. However, when a part of the pre-divided area is read, if the subject moves, there is a high possibility that the subject will not enter the set area, and the subject detection / tracking performance may be reduced.

  In view of the above problems, an object of the present invention is to provide an imaging apparatus that realizes high-speed continuous shooting while tracking a subject while suppressing the time taken to determine a focus position by autofocus.

  In order to solve the above-described problem, an imaging apparatus according to the present invention includes a reading unit that receives a shooting start command and reads a signal from an imaging element, a detection unit that detects a subject from the signal read by the reading unit, A determination unit that determines an area from which the signal is read based on a detection result of the detection unit; an acquisition unit that acquires an autofocus evaluation value based on the region determined by the determination unit; and the autofocus acquired by the acquisition unit Control means for calculating a driving amount for driving the lens from the evaluation value and outputting a control signal for driving the driving means, and the detecting means before the reading means completes reading the signal. In addition, the detection of the subject is started from the signal for which the reading has been completed.

  According to the present invention, it is possible to provide an imaging apparatus that realizes high-speed continuous shooting while tracking a subject while suppressing the time taken to determine the focus position by autofocus. In addition, subject detection processing is performed while still images are being read out, and an evaluation value calculation is executed by determining a reading area for acquiring an autofocus evaluation value based on the detection result. As a result, it is possible to perform high-speed continuous shooting while tracking the subject while suppressing the time taken to determine the focus position of the next shooting.

It is the schematic which shows the whole structure of an imaging device. It is a timing chart which shows the timing of operation | movement of imaging | photography process. It is a flowchart which shows operation | movement of an imaging | photography process. It is an operation | movement timing chart of the imaging | photography process which concerns on 2nd Embodiment. It is a flowchart which shows the operation | movement of the imaging | photography process which concerns on 2nd Embodiment. It is a flowchart which shows the operation | movement of the imaging | photography process which concerns on 3rd Embodiment. It is a flowchart which shows the operation | movement of the imaging | photography process which concerns on 3rd Embodiment. It is a timing chart of the operation | movement of the imaging | photography process which concerns on 3rd Embodiment, and explanatory drawing of readout mode. It is a flowchart which shows the operation | movement of the imaging | photography process which concerns on 4th Embodiment. It is a flowchart which shows the operation | movement of the imaging | photography process which concerns on 4th Embodiment. It is a flowchart which shows the operation | movement of the imaging | photography process which concerns on 5th Embodiment. It is a flowchart which shows the operation | movement of the imaging | photography process which concerns on 5th Embodiment.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(First embodiment)
First, the overall configuration of the imaging apparatus according to the present embodiment will be described with reference to FIG. The imaging device 100 according to the present embodiment is an imaging device such as a digital camera. As shown in FIG. 1, a first lens group 101 is disposed at the tip of the imaging optical system, and the first lens group 101 is held so as to be able to advance and retract in the optical axis direction. The aperture / shutter 102 adjusts the aperture diameter to adjust the amount of light during shooting, and also functions as an exposure time adjustment shutter when shooting a still image. The diaphragm / shutter 102 and the second lens group 103 integrally move forward and backward in the optical axis direction, and exhibit a zooming function (zoom function) in conjunction with the forward / backward movement of the first lens group 101. The third lens group 105 performs focus adjustment by moving back and forth in the optical axis direction. The optical low-pass filter 106 is an optical element for reducing false colors and moire in the captured image. The image sensor 107 includes a two-dimensional CMOS photosensor and a peripheral circuit, and is disposed on the imaging surface of the imaging optical system.

  The zoom actuator 111 rotates a cam cylinder (not shown) to drive the first lens group 101 to the third lens group 105 back and forth in the optical axis direction and perform a zooming operation. The aperture shutter actuator 112 controls the aperture diameter of the aperture / shutter 102 to adjust the amount of photographing light, and controls the exposure time during still image photographing. The focus actuator 114 adjusts the focus by driving the third lens group 105 back and forth in the optical axis direction.

  The illumination means (electronic flash for subject illumination) 115 used at the time of photographing is preferably a flash illumination device using a xenon tube, but an illumination device including LEDs that emit light continuously may be used. Autofocus (hereinafter referred to as AF) auxiliary light means 116 projects an image of a mask having a predetermined aperture pattern onto a subject via a light projection lens, and improves focus detection capability for a dark subject or a low-contrast subject. Let The control unit 121 controls various controls in the imaging apparatus 100, and includes a CPU (arithmetic unit) (not shown), an A / D converter, a D / A converter, a communication interface circuit, and the like.

  The electronic flash control circuit 122 controls lighting of the illumination unit 115 in synchronization with the photographing operation. The auxiliary light driving circuit 123 controls the lighting of the AF auxiliary light unit 116 in synchronization with the focus detection operation. The image sensor drive circuit 124 controls the image capturing operation of the image sensor 107, A / D converts the acquired image signal, and transmits it to the control unit 121. The image processing circuit 125 performs processing such as subject detection, γ conversion, color interpolation, and JPEG compression of the image acquired by the image sensor 107. The focus drive circuit 126 controls the focus actuator 114 based on the focus detection result, and adjusts the focus by driving the third lens group 105 back and forth in the optical axis direction. The aperture shutter drive circuit 128 controls the aperture of the aperture / shutter 102 by drivingly controlling the aperture shutter actuator 112. The zoom drive circuit 129 drives the zoom actuator 111 according to the zoom operation by the photographer.

  The display device 131 includes, for example, an LCD, and displays information related to the shooting mode of the imaging device 100, a preview image before shooting, a confirmation image after shooting, a display image of a focused state at the time of focus detection, and the like. To do. The operation switch group 132 includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. The recording medium 133 is a detachable flash memory or the like, and records an image file acquired by photographing. The memory 134 is a RAM, a ROM, or the like, and stores a predetermined program, holds image data during image processing, parameter data necessary for image processing, and the like. The control unit 121 drives various circuits of the imaging apparatus 100 based on a predetermined program stored in the ROM of the memory 134, and executes a series of operations such as AF, shooting, image processing, and recording.

  Next, the subject tracking AF continuous shooting performed by the imaging apparatus according to the present embodiment will be described with reference to FIGS. FIG. 2 is a timing chart showing operation timings in the subject tracking AF continuous shooting in the imaging apparatus according to the present embodiment. In addition, FIG. 3 is a flowchart illustrating an operation at the time of subject tracking AF continuous shooting in the imaging apparatus according to the present embodiment.

  The imaging apparatus 100 is based on the premise that the shooting mode is set to the subject tracking AF continuous shooting mode by the user operation of the shooting mode selection switch included in the operation switch group 132. In the shooting mode, shooting is started when a release switch included in the operation switch group 132 is turned on, and the process proceeds to step S301. First, in step S301, in response to a shooting start command, exposure to the image sensor 107 is started for still image shooting, and charges are accumulated. The exposure time is controlled by the aperture shutter actuator 112. At this time, the image sensor drive circuit 124 controls the image sensor 107 in a drive mode in which an area including the entire effective pixel area of the image sensor 107 is read. Note that the processing timing is executed after the start of photographing, as indicated by the still image accumulation 201 in FIG. Next, in step S <b> 302, the image sensor driving circuit 124 starts A / D conversion and transmitting the image signal obtained from the electric charge accumulated in the image sensor 107 to the control unit 121. In accordance with the drive mode set in step S301, an image signal of an area including the entire effective pixel area is read out. Note that the processing timing is executed after the still image storage processing is completed, as shown by still image reading 202 in FIG.

  In step S303, an image signal obtained from the electric charge accumulated in the image sensor 107 is A / D converted and transmitted to the control unit 121 one pixel at a time or in units of a plurality of pixels. Then, the start time of the subject detection process is determined as follows. First, the start of the subject detection process is determined to be the timing when reading up to an AF-enabled area is completed. This is because even if an object is detected in an area where AF cannot be performed and AF evaluation value calculation is performed in the vicinity thereof. After all, AF is not possible. In other words, when the subject is detected based on the read image signal when the readout to the AF-enabled area is completed, the necessary AF evaluation value calculation can be performed. The start time of the detection process may be used. In addition, since the AF-enabled area changes depending on the shooting mode and the type of lens, the detection start time may be changed according to the conditions, or may be determined based on the speed setting for continuous shooting. When the continuous shooting speed is fast, it is necessary to shorten the processing time between shootings, so that the processing time between shootings can be shortened by increasing the start time of the subject detection process. I can do it. In this case, since the number of image signals that have been read out decreases, the accuracy of subject detection decreases, but the continuous shooting speed can be increased.

  Next, in step S304, subject detection processing is started in the image processing circuit 125 based on the image signal transmitted to the control unit 121. As will be described later, the detection result information necessary for the AF process is the position information of the subject, the AF start time is limited, and the detection process needs to be completed before the AF start. If the detection process is not in time when there are many subjects, the position information of the detection process result from the previous shooting may be used instead. The method used may be used for processing. Further, as described above, the processing timing is from the middle of the still image reading, and is the time when reading is completed up to the AF-enabled area, or when the continuous shooting speed being set can be guaranteed.

  Next, in step S305, as shown in FIG. 2, subject detection 203 is started from the middle of the still image reading 202 process, and the still image reading process and the subject detection process are executed in parallel. Here, the AF start time is determined as follows. AF evaluation value calculation read area calculation processing, AF evaluation value calculation read storage, AF evaluation value calculation read, AF evaluation value calculation, and lens drive amount for the next shooting start time determined by the continuous shooting speed Calculation, lens driving, and so on.

  In step S306, an AF evaluation value calculation readout area is calculated from the subject detection result. As a premise, the AF evaluation value calculation readout is controlled by driving different from the still image readout in the image sensor driving circuit 124, and the effective pixel area of the image sensor 107 is partially read out. At this time, using the subject position information of the subject detection result, a position to be partially read out with respect to the effective pixel region with the subject position as the center is determined. The processing timing is included in the AF accumulation 204 of FIG. 2, but is executed at the timing of the AF start time determined as described above.

  Next, in step S307, exposure to the image sensor 107 is started for AF evaluation value calculation, and charges are accumulated. The exposure time is controlled by the aperture shutter actuator 112. Unlike the still image, in the present embodiment, the image sensor drive circuit 124 controls the image sensor 107 in a drive mode in which a part of the effective pixel area of the image sensor 107 is read. The processing timing is executed after the AF evaluation value calculation read area calculation process, as indicated by the AF accumulation 204 in FIG.

  Next, in step S <b> 308, the image sensor driving circuit 124 starts A / D conversion and transmitting the image signal obtained from the charge accumulated in the image sensor 107 to the control unit 121. That is, the image signal of a part of the effective pixel area is read according to the driving mode set in step S307. The processing timing is executed after the completion of the accumulation processing for AF evaluation value calculation readout, as shown by AF readout 205 in FIG.

  Next, in step S309, AF evaluation value calculation is performed based on the image signal transmitted to the control unit 121, and the control unit 121 calculates a lens driving amount for focusing on the subject in the next shooting. . The processing timing is executed after the AF evaluation value calculation readout is completed, as indicated by the drive amount calculation 206 in FIG.

  Next, in step S310, the lens is driven from the driving amount of the lens based on the control signal calculated and output by the control unit 121 to the position where the subject is focused. That is, the focus driving circuit 126 or the aperture shutter driving circuit 127 or a combination thereof is controlled to drive the actuators 114 and 112 to drive the lens to a position where the subject is focused. Note that the processing timing is executed after the driving amount is calculated, as indicated by the lens driving 207 in FIG.

  Next, in step S311, it is determined whether the release switch (SW2) included in the operation switch group 132 is on or off. If SW2 is on (NO), the process returns to step S301 to proceed, and continuous shooting is continued at the lens position focused in step S310. On the other hand, when SW2 is OFF (YES), continuous shooting is stopped and the shooting is ended. The timing of processing is determined by the release switch after the lens driving 207 of FIG. 2, and if SW2 is turned on, shooting is started and still image storage processing of the still image storage 208, still image reading and shooting of the still image reading 209 are started. Continue processing.

  As described above, in the present embodiment, the subject detection process is started in the middle of reading out a still image. Accordingly, the processing time between photographings can be further shortened by making detection processing and still image reading in parallel. In addition, for AF evaluation value calculation readout, the readout area is part of the effective pixel area of the image sensor based on the subject position. As a result, it is possible to shorten the time required for reading while maintaining the detection and tracking accuracy of the subject. Accordingly, by shortening the processing time between photographing and the AF evaluation value calculation readout time while maintaining the subject detection and tracking accuracy, the continuous shooting speed can be further increased in continuous shooting while following the subject.

(Second Embodiment)
Subject tracking AF continuous shooting performed by the imaging apparatus according to the second embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a timing chart showing operation timings in the subject tracking AF continuous shooting in the imaging apparatus according to the present embodiment. FIG. 5 is a flowchart showing an operation at the time of subject tracking AF continuous shooting in the imaging apparatus according to the present embodiment.

  In the present embodiment, the subject detection process differs from the subject tracking AF continuous shooting process performed by the imaging apparatus according to the first embodiment. For other processing, the same processing as the processing content according to the first embodiment is performed. That is, in steps S501 to S503 in FIG. 5, the same processes as in steps S301 to S303 in FIG. 3 are performed, and in steps S509 to S513 in FIG. 5, the same processes as in steps S307 to S311 in FIG. In addition, regarding the processing on the timing chart, the still image storage 401 and the still image reading 402 in FIG. 4, the still image storage 409 and the still image reading 410, the still image storage 201 and the still image reading 202 in FIG. The same processing as the storage 208 and the still image reading 209 is performed. Also, the AF accumulation 405 to the lens driving 408 in FIG. 4 perform the same processing as the AF accumulation 204 to the lens driving 207 in FIG. In the present embodiment, a subject detection process and timing different from the subject tracking AF continuous shooting process performed by the imaging apparatus according to the first embodiment will be described.

  First, in step S504, subject detection is started as in step S304 of FIG. However, in this embodiment, the subject is detected by two means. One detection means is a low-precision detection means that does not discriminate the contents or number of subjects. That is, it is a detection speed priority detection unit that guarantees that information on the position and size of the main subject is output as a detection result by adjusting the detection accuracy parameter by an AF start time described later. In the present embodiment, the detection is performed from color information based on the input image signal. This process corresponds to the mono detection process of the mono detection 403 in FIG.

  Another detection unit is a high-precision detection unit that determines whether or not a subject is a face as a detection result, and outputs the number of the subject, each position and size, and the order of importance. In other words, this detection means prioritizes detection accuracy so that the detection process becomes heavy when photographing a place where the number of faces and other objects is large, and it takes time to output the detection result. This corresponds to the face detection processing of face detection 404a and 404b in FIG. As for the timing for starting each detection, as shown in the mono detection 403, the face detection 404a, and the face detection 404b in FIG. 4, two detection processes are started simultaneously while the still image is being read out. To do.

  Next, in step S505, the still image reading process and the two subject detection processes are executed in parallel. As for the AF start time, as in step S305 of FIG. 3, the AF area calculation process, AF accumulation, AF readout, AF evaluation value, and lens drive amount are compared with the next shooting start time determined by the continuous shooting speed. Calculation, lens driving, and so on are determined to be completed.

  Next, in step S506, in the two subject detection processes started in step S504, it is determined whether or not a detection accuracy priority detection result has been output when the AF start time indicated in step S505 has elapsed. The determination timing starts when the AF start time is reached after the detection processing of the mono detection 403, the face detection 404a, and the face detection 404b is started. If a detection result with priority on detection accuracy has been output (YES), that is, if two detection results have been output by the AF start time as indicated by the mono detection 403 and the face detection 404b, step S507 is performed. Start processing. On the other hand, when only the detection speed priority detection result can be output (NO), that is, only the detection speed priority detection result can be output by the AF start time as indicated by the mono detection 403 and the face detection 404b. If there is, the process of step S508 is started. Each process will be described below.

  In step S507, an AF evaluation value calculation readout area is calculated using a detection accuracy priority detection result. If the detection result is one object, the reading area is determined with the position of the object as the center. On the other hand, when a plurality of objects are detected, the reading area is determined with the position of the highest ranked object as the center. In addition, when face information is used to determine the readout area, it is determined whether to determine the area centered on the pupil position or the center of the face itself depending on the size. Reading is started for the reading area determined as described above. As for the drive control of the image sensor 107 at the time of reading, control is performed by a driving method for partially reading the effective pixel region, as in step S306. Although the processing timing is included in 405, it is executed at the timing of the AF start time.

  In step S508, an AF evaluation value calculation readout area is calculated using the detection speed priority detection result. As the detection result, only information on one object is output, so a reading area is determined around the position of the object, and reading is started. As drive control of the image sensor 107 at the time of reading, control is performed by a drive method in which the effective pixel region is partially read out, similarly to steps S306 and S507 in FIG. Although the processing timing is included in the AF accumulation 405, it is executed at the timing of the AF start time.

  As described above, according to this embodiment, the detection method is divided into two in the first embodiment, and the detection and tracking of the subject are performed while guaranteeing the continuous shooting speed by the detection speed priority detection. Can also be guaranteed. In addition, when the detection accuracy priority is in time for the AF start time, the tracking performance can be improved by using a more accurate detection result.

(Third embodiment)
Hereinafter, the imaging apparatus according to the present embodiment will be described with reference to FIGS. The imaging apparatus according to the present embodiment can perform appropriate AF reading according to the condition of the subject. The basic configuration of the imaging apparatus according to this embodiment is the same as that of the imaging apparatus according to the first embodiment described above with reference to FIG.

  FIG. 6 is a flowchart showing subject tracking AF continuous shooting in the imaging apparatus according to the present embodiment. Each step shown in FIG. 6 is performed by the control unit 121 of the imaging apparatus 100 according to the present embodiment. First, Steps S601 to S608 and Steps S613 to S617 in FIG. 6 are the same as Steps S501 to S508 and Steps S509 to S513 in FIG. To do.

  In step S609, the luminance in the area corresponding to the AF read area determined in step S607 or step S608 is calculated in the still images taken in steps 601 and S602. If it is determined that the brightness is lower than the brightness threshold value stored in advance in the memory 134 (YES in step S609), the process proceeds to step S610. On the other hand, when it is determined that the brightness is not low (NO in step S609), the process proceeds to step S611.

  In step S610, the size and movement of the subject are compared with the size threshold value and the motion threshold value stored in advance in the memory 134 from the face / mono detection result detected in step S604. If it is determined that the size of the subject is small and the movement is small (below the threshold) (NO in step S610), the process proceeds to step S612. On the other hand, if it is determined that the size of the subject is large or the movement is large (greater than or equal to the threshold value) (YES in step S610), the process proceeds to step S611.

  Next, in step S611, the imaging device driving circuit 124 sets the imaging operation of the imaging device 107 for AF readout to the thinning mode in a range including the AF readout area determined in step S607 or step S608. On the other hand, in step S612, the imaging device driving circuit 124 sets the imaging operation of the imaging device 107 for AF readout to the crop mode within the range including the AF readout area determined in step S607 or step S608. The readout range set in the crop mode is narrower than the thinning mode.

  Here, the relationship between the determination in step S609 and step S610 and the AF readout mode will be described with reference to FIG. When the brightness of the AF readout area in a still image is low as in the image 419 and the size and movement of the subject are small, a crop mode is set in which the AF readout mode is limited to the subject portion as in AF420. On the other hand, when the AF readout area in the still image is not low brightness like the image 417 and the subject size is large or the motion is large, the AF readout mode is not full screen like the AF418 but includes the subject portion. Set the thinning mode to read a part of a wide range.

  In the present embodiment, the luminance threshold value, the magnitude threshold value, and the motion threshold value stored in advance in the memory 134 in steps S609 and S610 may be configured to be set by the user using the operation switch group 132 before shooting. In step S610, the AF read mode is determined by determining the size and movement of the subject. In step S606, the face is set as the subject when face detection is performed, and the object is set as the subject when face detection is not performed. Do.

  As described above, according to this embodiment, when the size and movement of the subject are small according to the determination result of the luminance, size, and movement of the subject, the crop mode reading is performed in a narrow range, and the amount of information in the region is calculated. You can get more. Therefore, it is possible to improve the low brightness performance of AF even when the brightness of the subject is low, without impairing the continuous shooting performance of subject tracking AF continuous shooting.

(Fourth embodiment)
Hereinafter, the imaging apparatus according to the present embodiment will be described with reference to FIGS. 9 and 10. The imaging apparatus according to the present embodiment can perform appropriate AF reading according to the condition of the subject. The basic configuration of the imaging apparatus according to this embodiment is the same as that of the imaging apparatus according to the first embodiment described above with reference to FIG. 9 and 10 are flowcharts illustrating subject tracking AF continuous shooting in the imaging apparatus according to the present embodiment. Each step shown in FIGS. 9 and 10 is performed by the control unit 121 of the imaging apparatus 100 according to the present embodiment.

  Steps S701 to S707 and Steps S712 to S716 are the same as Steps S501 to S507 and Steps S509 to S513 in FIG. 5 described above in the second embodiment, and thus description thereof is omitted.

  In step S708, an AF read area is determined from the mono detection result of the image processing circuit 125, and the process proceeds to step S711. Next, in step S709, the luminance in the area corresponding to the AF readout area determined in step S707 or step S708 is calculated in the still images taken in steps 701 and S702. And it compares with the brightness | luminance threshold value previously memorize | stored in the memory 134. FIG. As a result, when it is determined that the luminance is low (YES in step S709), the process proceeds to step S710. On the other hand, when it is determined that the luminance is not low (NO in step S709), the process proceeds to step S711.

  Next, in step S710, the imaging device driving circuit 124 sets the imaging operation of the imaging device 107 for AF readout to the crop mode within a range including the AF readout area determined in step S707 or step S708. On the other hand, in step S711, the imaging device driving circuit 124 sets the imaging operation of the imaging device 107 for AF readout to the thinning mode in a range including the AF readout area determined in step S707 or step S708. Note that the read range set in the crop mode is narrower than the thinning mode. In addition, when only object detection can be performed by subject detection, subject tracking performance in the image processing circuit 125 is inferior to that when a face is detected, and thus a wide range of information is required to find a target by AF.

  As described above, according to the present embodiment, when only mono detection can be performed, it is difficult to lose sight of the AF target by the thinning mode which is a wider range of reading, and thus it is possible to maintain the AF continuity of the subject tracking AF continuous shooting. .

(Fifth embodiment)
Hereinafter, the imaging apparatus according to the present embodiment will be described with reference to FIGS. 11 and 12. The imaging apparatus according to the present embodiment can perform appropriate AF reading according to the condition of the subject. The basic configuration of the imaging apparatus according to the present embodiment is the same as that of the imaging apparatus according to the first embodiment described above with reference to FIG.
FIG. 9 is a flowchart showing subject tracking AF continuous shooting in the imaging apparatus according to the present embodiment. Each step shown in FIGS. 11 and 12 is performed by the control unit 121 of the imaging apparatus 100 according to the present embodiment.

  Steps S801 to S812 and steps S814 to S818 are the same as steps S601 to S612 and steps S613 to S617 in FIG. 6 and FIG.

  In step S813, the AF accumulation time in step S814 and the AF read time in step S815 are calculated. In order to maintain the AF accuracy of the subject tracking AF continuous shooting, the AF accumulation 413 and the AF readout 414 in FIG. 8 need to be completed within a predetermined time until the next shooting starts. The total processing time for AF accumulation and AF reading is constant, but the AF reading time varies depending on the AF reading area and mode set in step S811 or step S812. When the subject area has low brightness, the AF accumulation time is extended within the total processing time when the AF readout time is short, and when the subject area is not low brightness, the AF accumulation time is the same value or suitable for AF. Value.

  As described above, according to the present embodiment, the AF readout time is calculated according to the AF readout area and the readout mode, and the AF image brightness can be increased by extending the AF accumulation time when the subject area has a low brightness. Therefore, AF processing with higher accuracy is possible.

  Moreover, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 100 Imaging device 107 Image sensor 121 Control part

Claims (10)

Read means for receiving a shooting start command and reading a signal from the image sensor;
Detecting means for detecting a subject from the signal read by the reading means;
Determining means for determining a region from which the signal is read based on a detection result of the detecting means;
Acquisition means for acquiring an autofocus evaluation value based on the area determined by the determination means;
A control unit that calculates a driving amount for driving the lens from the autofocus evaluation value acquired by the acquiring unit and outputs a control signal for driving the driving unit;
With
The image pickup apparatus, wherein the detection unit starts detection of the subject from a signal for which the reading has been completed before the reading unit has completed reading the signal. The imaging apparatus according to claim 1, wherein reading of the signal by the reading unit and detection of the subject by the detection unit are performed in parallel. The detection means includes
First detection means for detecting the subject with priority on detection speed;
Second detection means for detecting the subject giving priority to detection accuracy;
Have
The first detection means and the second detection means detect the subject in parallel,
The imaging apparatus according to claim 1, wherein the determination unit determines the region according to a detection result of the second detection unit. The determination means determines the region based on the detection result by the second detection means when the detection result of the subject by the second detection means is output, and the detection result by the second detection means The imaging apparatus according to claim 3, wherein when the image is not output, the region is determined based on a detection result by the first detection unit. First determination means for determining the luminance of the subject;
Second determination means for determining the size and movement of the subject;
Further comprising
The determination unit determines a thinning mode based on a region determined based on a detection result of the second detection unit according to a determination result of the first and second determination units. 5. The imaging device according to 4. The thinning mode includes a first mode and a second mode,
The determination unit determines that the first determination unit determines that the luminance is higher than a predetermined luminance threshold, or the first unit determines that the luminance is lower than the predetermined luminance threshold, and the second If the determination means determines that the size and movement of the subject are equal to or greater than a predetermined threshold, the first mode is determined,
The determining means is when the first determining means determines that the luminance is lower than the predetermined luminance threshold, and the second determining means determines that the size and movement of the subject are equal to or less than the predetermined threshold. The imaging apparatus according to claim 3, wherein the second mode is determined. The first mode is a mode in which thinning is performed in a range including the determined area,
The imaging apparatus according to claim 6, wherein the second mode is a mode that does not perform thinning out in a range that includes the determined region and that is narrower than the range in the first mode. . The determining means determines the area when the determining means determines the area based on the detection result by the first detecting means, or when the determining means determines the area based on the detection result by the second detecting means. And when the first determination means determines that the luminance is higher than a predetermined luminance threshold, the first mode is determined,
The determining means determines the area based on the detection result by the second detecting means, and the first determining means determines that the luminance is lower than a predetermined luminance threshold, The imaging apparatus according to claim 3, wherein the second mode is determined. A calculation unit for calculating a time for the acquisition unit to acquire the autofocus evaluation value;
The imaging apparatus according to claim 5, wherein the calculation unit calculates the time according to the thinning mode. A method for controlling an imaging apparatus,
A reading process of receiving a shooting start command and reading a signal from the image sensor;
A detecting step of detecting a subject from the signal read in the reading step;
A determination step of determining a region from which the signal is read based on a detection result in the detection step;
An acquisition step of acquiring an autofocus evaluation value based on the region determined in the determination step;
A control step of calculating a driving amount for driving the lens from the autofocus evaluation value acquired in the acquisition step, and outputting a control signal for driving the driving unit;
Have
In the detection step, the detection of the subject is started from the signal that has been read before the signal is completely read in the reading step.

Images