JP5762038B2 - Imaging apparatus and control method - Google Patents

Description

  The present invention relates to an imaging apparatus capable of tracking a subject.

  2. Description of the Related Art Conventionally, there is known an imaging apparatus having a so-called subject tracking function that recognizes where a main subject is in an imaging screen and automatically tracks its position. By using this subject tracking function, automatic focus adjustment control (AF control) and exposure control can be continuously performed on a moving main subject.

  As an example of an imaging apparatus having such a subject tracking function, in an imaging apparatus such as a single-lens reflex camera having a photometry unit used for photometry separately from an image sensor, subject tracking is performed based on photometric data output from the photometry unit. Japanese Patent Application Laid-Open No. H10-228707 describes that.

JP-A-5-22670

  However, when subject tracking is performed based on photometric data output from the photometric unit as in the imaging device described in Patent Document 1, the following problems occur.

  A general single-lens reflex camera such as the image pickup apparatus described in Patent Document 1 moves the position of a quick return mirror provided in the camera to guide the incident light flux from the subject to the image sensor and the eyepiece. It is the structure which switches the state led to a lens (optical viewfinder).

  Further, when the incident light beam from the subject is guided to the eyepiece, the incident light beam from the subject is also guided to the photometry unit, and the subject can be measured. That is, in the state where the incident light beam from the subject is guided to the image sensor, the photometry unit cannot perform photometry.

  That is, if the state in which the incident light flux from the subject is guided to the image sensor and the state to be guided to the photometry unit are continuously switched in a short cycle as in continuous shooting (during continuous shooting), photometry is performed by the photometry unit Storage time is limited. In particular, if the photometry data output from the photometry unit is to be used for subject tracking, the subject tracking calculation process must be terminated before AF control or exposure control is performed, and the incident light flux from the subject is guided to the photometry unit. Accumulation time is further limited than the period of time.

  Therefore, the accumulation time of the photometry unit is shorter than the flicker cycle, and the influence of flicker becomes large, and an accurate photometric value may not be obtained. Here, flicker will be described. When photometry is performed under a fluorescent lamp or the like, a so-called flicker phenomenon occurs in which the brightness of illumination light periodically changes due to the influence of the AC power supply frequency. The flicker cycle is about 10 ms in the region where the power supply frequency is 50 Hz, and about 8.3 ms in the region where 60 Hz. When photometry is performed in such an environment, if the accumulation time of the photometry unit is not an integral multiple of the flicker period, the photometric value varies depending on which part of the phase of the flicker period overlaps the accumulation period. Therefore, it becomes difficult to perform stable exposure control.

  Therefore, if the accumulation time of the photometry unit is increased in order to reduce the influence of flicker, the time until the subject tracking calculation process is completed also increases, and the continuous shooting speed during continuous shooting decreases.

  Therefore, an object of the present invention is to perform subject tracking without reducing the continuous shooting speed during continuous shooting, and to perform exposure control that reduces the effect of flicker.

In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging unit, a charge accumulation unit that accumulates charges according to the amount of incident light, a tracking unit that tracks a subject, and an exposure that performs exposure control. Control means, wherein the charge accumulation means performs second accumulation after performing the first accumulation, and the tracking means does not use the image signal obtained by performing the second accumulation. The tracking is performed based on the image signal obtained by performing the first accumulation, and the exposure control means performs the image signal obtained by performing the first accumulation and the second accumulation. based on the obtained image signal, and performs exposure will control.

In order to achieve the above object, an image pickup apparatus control method according to the present invention is an image pickup apparatus control method including an image pickup means and charge accumulation means for accumulating charges according to the amount of incident light. A first charge accumulation step for performing first accumulation by the charge accumulation means; a second charge accumulation step for performing second accumulation after the first accumulation; and performing the second accumulation. A tracking step for tracking the subject based on the image signal obtained by performing the first accumulation without using the image signal obtained in the above; an image signal obtained by performing the first accumulation; and An exposure control step of performing exposure control based on an image signal obtained by performing the second accumulation.

  According to the present invention, it is possible to perform subject control without reducing the continuous shooting speed during continuous shooting, and to perform exposure control that reduces the influence of flicker.

1 is a schematic configuration diagram of an imaging apparatus according to an embodiment of the present invention. The figure which shows the operation | movement sequence at the time of imaging | photography in embodiment of this invention. The figure which shows the outline of the photometry operation | movement in embodiment of this invention. The figure explaining the difference by the pixel addition number of the read-out image of the photometry sensor in embodiment of this invention. Explanatory drawing of the photometry calculation in embodiment of this invention. The figure which showed AF control according to the movement of the tracking object in embodiment of this invention. The figure which showed AF control according to the movement of the tracking object at the time of using the face detection result in embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment of the present invention, in which 100 is a camera body, and 200 is a lens unit that can be attached to and detached from the camera body 100.

  Reference numeral 101 denotes a microcomputer CPU (hereinafter referred to as CPU) that controls each part of the camera body 100. Reference numeral 102 denotes an image sensor such as a CCD or CMOS including an infrared cut filter, a low-pass filter, and the like, which photoelectrically converts a light beam incident through the photographing lens of the lens unit 200 and outputs an image signal.

  Reference numeral 103 denotes a mechanical shutter that travels in a light shielding state in which the image sensor 102 is shielded from a light beam incident through the photographing lens and a retracted state in which the light beam incident through the photographing lens is guided to the image sensor 102.

  Reference numeral 104 denotes a half mirror, which is movable between a position for guiding a light beam incident through the photographing lens to the image sensor 102 (mirror up state) and a position for guiding it to the photometric sensor 106 (mirror down state). In other words, the half mirror 104 changes the optical path of the light beam incident through the photographing lens between the state leading to the image sensor 102 and the state leading to the photometric sensor 106. Further, when it is at a position to be guided to the photometric sensor 106, the light beam incident through the photographing lens is imaged on the focus plate 105.

  Reference numeral 106 denotes a photometric sensor using an image sensor such as a CCD, which photoelectrically converts a subject image to accumulate charges and output an image signal. In the present embodiment, an example in which a CCD having M × N pixels arranged in a matrix of M vertical and N horizontal pixels is used for the photometric sensor 106 will be described.

Reference numeral 107 denotes a pentaprism, which guides the light beam incident through the photographing lens reflected by the half mirror 104 to the photometric sensor 106 and an optical viewfinder (not shown).
Reference numeral 108 denotes a memory such as a RAM or a ROM connected to the CPU 101.
Reference numeral 109 denotes a focus detection circuit, and 110 denotes an AF mirror. The AF mirror 110 reflects a part of the light beam incident through the taking lens and passed through the half mirror 104 and guides it to the AF sensor in the focus detection circuit. The AF sensor has a plurality of AF areas in the imaging screen, and can determine the defocus amount of each AF area.

  The CPU 101 transmits AF control information based on the output from the focus detection circuit 109 to a lens CPU 201 (hereinafter referred to as LCPU) that controls each part of the lens unit 200. The LCPU 201 performs automatic focus adjustment control (hereinafter referred to as AF control) by driving the photographing lens in the lens unit 200 based on the received AF control information.

  Reference numeral 111 denotes a CPU (hereinafter referred to as ICPU) for performing image processing and calculation processing of an image signal output from the photometric sensor 106 after charge accumulation, and based on the image signal output from the photometric sensor 106. Calculations such as subject tracking, photometry, and face detection described later are performed. The result of the photometric calculation of the ICPU 111 is transmitted to the CPU 101, and the CPU 101 sets the shutter speed and aperture value based on the result of the photometric calculation and performs exposure control.

  In this embodiment, the CPU for performing image processing and calculation processing of the image signal output from the photometric sensor 106 is provided separately from the CPU that controls each part of the camera main body 100. It may be configured to perform the process.

Further, a configuration in which the lens unit 200 is built in the camera body 100 or a configuration in which the CPU 101 drives the photographing lens to perform AF control may be used.
Reference numeral 112 denotes a memory such as a RAM or a ROM connected to the ICPU 111.

  Next, an operation sequence at the time of shooting in the present embodiment will be described with reference to FIG. FIG. 2 shows an operation sequence from the mirror-down state before shooting the Nth frame (N ≧ 2) during continuous shooting to the mirror-down state before shooting the (N + 2) th frame. .

  First, in order to capture the Nth frame, the photometric sensor 106 performs accumulation a1 (first accumulation) in the mirror-down state. This accumulation a1 is an accumulation for obtaining an image signal used for subject tracking, and the accumulation time can reflect the result of subject tracking calculation processing in AF control so as not to reduce the continuous photographing speed during continuous photographing. Is set by the ICPU 111. Therefore, when the continuous shooting speed of continuous shooting is higher than a predetermined value, the time is set shorter than the flicker cycle. However, if the accumulation time is too short, sufficient accumulation is not performed and subject tracking calculation processing cannot be performed. Therefore, an accumulation time necessary for obtaining an image signal that can be subject tracking calculation processing is set.

  Although not shown in FIG. 2, accumulation by the AF sensor in the focus detection circuit 109 for performing AF control is also performed in parallel with the accumulation a1, and each AF area is based on the accumulation result by the AF sensor. The defocus amount calculation processing is performed. After that, AF control is performed based on the calculation result of the defocus amount, the result of the tracking calculation described later, and the like.

  In this way, by performing subject tracking based on the image signal obtained in the accumulation a1, it is possible to perform AF control that reflects the tracking result without reducing the continuous shooting speed during continuous shooting.

  When the accumulation a1 is completed, the reading Ra1 for reading the accumulated image signal is started. Further, accumulation b1 (second accumulation) is performed in parallel with the reading Ra1. This accumulation b1 is an accumulation for performing photometric calculation with reduced influence of flicker, and is set so that the photometric calculation process can be completed before the start of exposure control.

  As described above, the exposure control that reduces the flicker effect by performing the storage b1 following the storage a1 and performing the photometric calculation based on the image signal obtained by the storage a1 and the image signal obtained by the storage b1. It can be performed.

  As shown in FIGS. 3A and 3B, when the accumulation a1 is shorter than the flicker period, the luminance value based on the accumulated image signal depends on which part of the phase of the flicker period the accumulation a1 overlaps. It will vary. Therefore, as shown in FIGS. 3C and 3D, the accumulation b1 is performed after the accumulation a1, and the photometric calculation is performed based on the image signals accumulated in each. By doing so, the total accumulation time of the image signal used for the photometric calculation becomes longer than when the photometric calculation is performed based only on the image signal accumulated in the accumulation a1. Therefore, the influence of flicker is reduced compared to the case where the photometric calculation is performed based only on the image signal stored in the storage a1, and more accurate exposure control can be performed. Further, by varying the phase of the flicker cycle that overlaps between the accumulation a1 and the accumulation b1, the fluctuation of the average value of the light amount of the flicker light source during the accumulation period including the accumulation a1 and the accumulation b1 is reduced, and the result of the photometric calculation However, stable and more accurate exposure control can be performed.

  If the sum of the accumulation time of accumulation a1 and the accumulation time of accumulation b1 is set to be substantially equal to an integral multiple of the flicker cycle, the effect of flicker can be further reduced.

  Next, when the reading Ra1 is completed, the subject tracking calculation process is started. The subject tracking calculation process must be completed before the start of AF control, and the ICPU 111 sets the accumulation time of accumulation a1 so that the tracking calculation process is completed before the start of AF control.

When the accumulation b1 is completed, the read Rb1 for reading the accumulated image signal is started. Further, accumulation c1 (third accumulation) is performed in parallel with the reading Rb1. This accumulation c1 is an accumulation for obtaining an image signal used for detecting the face of the subject. However, since the face detection calculation requires a longer time than the tracking calculation or photometry calculation, the face detection calculation cannot be completed in time for AF control for photographing performed immediately after the accumulation c1 is completed. Therefore, the result of the face detection calculation using the image signal obtained in the storage c1 is used for AF control for the next shooting, not the shooting performed immediately after the storage c1 ends. The read Rc1 for reading the image signal stored in the storage c1 can be executed even while the mirror is up, so that the series of processes from the start of the storage a1 to the end of the storage c1 is completed during the mirror down. The accumulation time of c1 is set by the ICPU 111. Then, the mirror-up operation is started before the reading Rc1 for reading the image signal accumulated in the accumulation c1 is completed. Therefore, the face detection calculation is performed after the mirror up operation is started.
Similarly, accumulation a2, b2, and c2, and accumulation a3, b3, and c3 are performed during mirror down before photographing of the (N + 1) and N + 2 frames.

  As described above, in the present embodiment, the accumulations a1, b1, and c1 are performed while the mirror is down. However, in order to reduce the influence of flicker in various processes, intermittent accumulation may be performed in each accumulation.

  As shown in FIGS. 3A and 3B, when the accumulation a1 is shorter than the flicker period, the luminance value based on the accumulated image signal depends on which part of the phase of the flicker period the accumulation period overlaps. It will vary.

  Therefore, as shown in FIG. 3E, accumulation is performed intermittently for a plurality of times, and accumulation is performed for each time divided by the number of times of accumulation when accumulation is performed collectively. That is, the accumulation time shown in FIG. 3A is equal to the total accumulation time of a plurality of accumulations shown in FIG. The image signal obtained by intermittent accumulation is used as the image signal obtained by accumulation a1.

  When intermittent accumulation is performed in this way, the flicker cycle phase overlapping with the accumulation period is dispersed, so that the influence of flicker can be reduced compared to normal accumulation.

  In the intermittent accumulation described above, it is desirable not to read out the image signal every time each accumulation is completed, but to integrate the image signals accumulated in each accumulation and read out the image signal after all the accumulations are completed. . In this way, reading of the image signal after each accumulation can be omitted, and the processing load can be reduced.

  Such intermittent accumulation may be executed in at least one of accumulations a1, b1, and c1, and whether to perform intermittent accumulation may be switched according to each accumulation time. For example, intermittent accumulation may be performed when the accumulation time is shorter than the flicker cycle and the influence of flicker is considered large.

  Further, as shown in FIG. 3 (f), when intermittent accumulation is performed in both accumulation a1 and accumulation b1, the flicker cycle overlapping with the accumulation period is further increased than in the cases shown in FIGS. 3 (c) and 3 (d). Since the phase is dispersed, the influence of flicker can be further reduced.

  Next, a method for reading an image signal in this embodiment will be described with reference to FIG. In this embodiment, a striped CCD in which R, G, and B pixels are arranged in a stripe shape as shown in FIG. 4 is used for the photometric sensor 106. In such a striped CCD, an analog type is used in the vertical direction. It is possible to add a pixel to.

  Therefore, for example, when the number of added pixels is set to 4 pixels, the size of the image based on the read image signal is reduced by ¼ in the vertical direction. At this time, the output level of the image signal by adding pixels is about four times that when no pixels are added (reading all pixels). Therefore, an image based on an image signal read without adding pixels in an accumulation time of about 1/4. Can be obtained. In addition, since the amount of image signal read out is smaller than when no pixels are added, the time required to read out the image signal can be shortened.

  Further, by performing pixel addition reading as described above in the readings Ra1 and Rb1, it is possible to obtain an image signal that can be subjected to subject tracking calculation processing in a short accumulation time even for a dark subject. Although it is considered that the accumulation time is shortened and the influence of flicker is increased by performing pixel addition reading, the influence of flicker can be suppressed by combining with the intermittent accumulation described above.

  Note that when pixel addition is performed, the resolution of the image is reduced. Therefore, when face detection of a subject is performed by a method for determining whether a human face is present in an image by matching with a face pattern prepared in advance. Will reduce the detection accuracy. Therefore, when subject face detection is performed by such a method, pixel addition is performed in the read Rc1 for reading out the image signal accumulated in the accumulation c1, which is accumulation for obtaining an image signal used for subject face detection. It is desirable to read out all pixels without using any other method.

  Next, photometric calculation in this embodiment will be described with reference to FIG. As shown in FIG. 5, the image based on the image signal obtained by accumulation by the photometric sensor 106 is divided into I photometers and J photometers. Here, each photometric area has m pixels vertically and n pixels horizontally, I × m = M, J × n = N, and the photometric sensor 106 as a whole becomes M × N pixels.

In each photometric area, average outputs Ra, Ga, and Ba of R, G, and B pixels are calculated, and a luminance value Yij of each photometric area is calculated from the calculated Ra, Ga, and Ba.
Yij is obtained by the following equation (1), for example.
Yij = A × Ra + B × Ga + C × Ba (1)
Luminance Yij is obtained by entering an appropriate value for the mixing ratios A, B, and C of R, G, and B.

Next, a weighted average calculation is performed by weighting Yij of each photometric area in accordance with a photometric mode such as evaluation photometry or spot photometry, and a luminance value of the entire photometric area is obtained.
The above photometric calculation is performed on the image signal obtained by performing accumulation a1 and the image signal obtained by performing accumulation b1, and respective luminance values Y1 and Y2 are obtained.

Here, when the accumulation time of accumulation a1 is T1, and the accumulation time of accumulation b1 is T2, the final luminance value Y used for exposure control is expressed by the following equation (2).
Y = (Y1 / T1 + Y2 / T2) × T1 / 2 (2)
The above equation (2) is an equation for obtaining the average value of the respective luminance values obtained when the accumulations a1 and b1 are both accumulated at the accumulation time T1, but the calculation equation for obtaining the final luminance value is as follows. It is not restricted to Formula (2). For example, an equation for obtaining the average value of the respective luminance values obtained when the accumulations a1 and b1 are both accumulated at the accumulation time T2 may be used, or the accumulations a1 and b1 are both accumulated at the predetermined accumulation time Ts. It is also possible to use an equation for obtaining an average value of the respective luminance values obtained in the case of

In addition, the storage time of the storage a1 and the storage time of the storage b1 are set to be the same, and the expression (3) or the like in which each storage time is half the flicker cycle and is simply added and averaged is also considered.
Y = (Y1 + Y2) / 2 (3)
If each accumulation time is set so that the total accumulation time of the accumulation time of accumulation a1 and the accumulation time of accumulation b1 becomes the same time as the flicker cycle as shown in Expression (3), the influence of flicker is further increased. Can be reduced.

  Note that the accumulation times of accumulations a1, b1, and c1 may be set to a predetermined time, or may be set by the ICPU 111 based on the result of the previous photometric calculation. When setting by the ICPU 111 based on the result of the previous photometric calculation, for example, the accumulation time is higher when the final luminance value Y is higher than when the final luminance value Y obtained from the result of the previous photometric calculation is low. Set to be shorter.

  Next, subject tracking calculation processing will be described. The tracking calculation in the present embodiment is performed by, for example, comparing an image obtained by performing accumulation a1 with an image obtained by performing accumulation a2, and based on the distribution of luminance patterns and color patterns to be tracked satisfying predetermined conditions. Calculate (pattern matching) where the tracking target has moved. That is, tracking of a target that satisfies a predetermined condition in the imaging screen is performed. Then, AF control is performed by changing the AF area to be focused in accordance with the movement of the tracking target. Alternatively, exposure control is performed by changing the weighting for each photometric area in accordance with the movement of the tracking target.

FIG. 6 is a diagram illustrating AF control in accordance with the movement of the tracking target.
In the initial state at the time of continuous shooting, when the main subject exists at the position of FIG. 6A in the imaging screen, the AF frame 7 at the position where the main subject exists is used as a frame indicating the AF area to be focused. It is set and AF control is performed. In FIGS. 6A to 6D, the AF frame set as a frame indicating the AF area to be focused is represented by a thicker frame than the other AF frames.

  After performing AF control and focusing on an area corresponding to the AF frame 7, accumulation for obtaining an image signal used for subject tracking is performed. Then, the ICPU 111 sets a predetermined area based on the AF frame 7 in the obtained image as a tracking area that is an area for matching the luminance pattern and the color pattern in the tracking calculation. Note that an image signal used for subject tracking calculation processing can be read out by performing pixel addition, but FIG. 6 shows an image when all pixels are read out.

  Thereafter, it is assumed that accumulation for obtaining an image signal used for tracking the next subject is performed in a state where the position where the main subject exists is changed to the position shown in FIG. 6B. In order to determine where the tracking target has moved in the current image thus obtained, the ICPU 111 searches the tracking target for a predetermined area based on the tracking area set based on the AF frame 7. It is set as a search area that is an area. The search area includes the tracking area and is set to be an area wider than the tracking area.

  Then, the ICPU 111 determines whether there is an area that matches the luminance pattern and the color pattern of the tracking area of the previously obtained image in the search area of the image obtained this time. As the search area is set wider, tracking is possible even if the position of the tracking target changes greatly. However, the wider the search area, the longer the time required for determination, so in consideration of tracking accuracy, time available for tracking calculation, etc. To set the search area.

  When it is determined that there is an area that matches the tracking area in the search area, the AF frame existing in the area is set as an AF frame indicating an AF area to be focused next. In FIG. 6B, the AF frame 8 corresponds to that. Then, after AF control is performed so that the area corresponding to the AF frame 8 is focused, imaging is performed.

  When determining that there is a region that matches the tracking region in the search region, it may be determined that there is a matching region if there is a region whose degree of coincidence with the tracking region is a predetermined value or more.

  Further, the ICPU 111 newly sets an area that matches the tracking area of the previously obtained image in the image obtained this time as a tracking area.

  After that, it is assumed that accumulation for obtaining an image signal used for the next subject tracking is performed in a state where the position where the main subject exists is changed to the position shown in FIG. In order to determine where the tracking target has moved in the current image thus obtained, the ICPU 111 sets a search area based on the position of the tracking area. That is, since the tracking area newly set last time is an area having the AF frame 8 near the center, the search area is changed from the previous time accordingly.

Similarly in FIG. 6D in which the position of the main subject has moved from FIG. 6C, the search area is changed and the tracking target is searched.
Thereafter, by performing the tracking calculation before each imaging in the continuous shooting, it is possible to always perform the imaging in focus on the main subject to be tracked in the initial state.

  In addition, in each tracking calculation at the time of continuous shooting, when the tracking calculation fails, for example, when the tracking calculation fails in the state of FIG. 6C of FIGS. 6A to 6D, FIG. In the tracking calculation in this state, the tracking calculation may be performed based on the tracking area in FIG. That is, an area that matches the tracking area of the image shown in FIG. 6B in the image shown in FIG. In this case, since it is assumed that the position of the subject changes more than in the case where the tracking calculation is performed between consecutive images, the search may be performed with the search area set wider than usual.

Alternatively, if the tracking calculation fails in each tracking calculation during continuous shooting, the tracking target may be set again.
Further, it is conceivable that the brightness of each image used for subject tracking calculation varies due to the effect of flicker if the accumulation time is shorter than the flicker cycle. In such a case, the images may be compared after performing a process for making the brightness of each image substantially the same level.

  Further, the result of face detection calculation can be used in the above-described subject tracking calculation process, and subject tracking can be performed more accurately by using the face detection result. Hereinafter, the subject tracking calculation process using the face detection result will be described with reference to FIG. FIG. 7 is a diagram illustrating AF control in accordance with the movement of the tracking target when the face detection result is used. As a technique for detecting a person's face, any one of well-known methods may be used. For example, the face is obtained by converting photometric data into hue and saturation, and creating and analyzing this two-dimensional histogram. A method for determining an area may be used. Alternatively, a method may be used in which a face candidate area corresponding to the shape of the person's face is extracted and the face area is determined from the feature amount in the area.

  When the main subject is present at the position shown in FIG. 7A in the initial state during continuous shooting, AF control is performed so that the AF area corresponding to the AF frame 7 at the position where the main subject exists is focused. Done. In FIGS. 7A to 7D, the AF frame set as a frame indicating the AF area to be focused is represented by a thicker frame than the other AF frames. In this state, an area other than the face of the main subject may be set as an AF area to be focused.

  Then, in a state where the area corresponding to the AF frame 7 is in focus, accumulation for obtaining an image signal used for subject tracking and accumulation for obtaining an image signal used for detecting the face of the subject are performed. Then, face detection calculation is performed based on the obtained image signal, and the detected face area of the subject is set as a tracking area in an image used for subject tracking.

  Thereafter, in a state where the position where the main subject exists is moved and changed to the position shown in FIG. 7B, accumulation for obtaining an image signal used for tracking the next subject and image signal used for detecting the face of the subject are obtained. Is accumulated. Thus, in order to determine where in the image obtained this time the tracking target has moved, a search area is set based on the position of the tracking area in the previously obtained image. That is, in the image shown in FIG. 7A, the area near the AF frame 2 is set as the face area of the subject by face detection calculation, and this face area is set as the tracking area. The predetermined area is set as a reference.

  Then, in the search area of the image obtained this time, it is searched whether there is an area that matches the luminance pattern and color pattern of the tracking area of the image obtained last time.

  If there is an area that matches the tracking area in the search area, the AF frame that exists in that area is set as an AF frame that indicates the AF area to be focused next. In FIG. 7B, the AF frame 3 corresponds to that. Then, after AF control is performed so that an area corresponding to the AF frame 3 is focused, imaging is performed.

  In this AF control, the face detection calculation using the image signal accumulated with the subject at the position shown in FIG. 7B is not in time, so the result of the face detection calculation is the result of the next AF control. Used for tracking operation.

Further, face detection calculation is performed using the image signal accumulated with the subject at the position of FIG. 7B, and the detected face area of the subject is newly set as a tracking area in the image used for subject tracking. To do.
In this manner, by setting the tracking area for each tracking calculation based on the result of the face detection calculation, the tracking target face area can be accurately tracked.

  If the region that matches the previous tracking region in the image used for the tracking operation of the subject obtained this time and the detected face region of the subject are substantially equal, the region that matches the previous tracking region is a new region. It may be set as a tracking area.

  Thereafter, in a state where the position where the main subject exists further moves and changes to the position shown in FIG. 7C, an image signal used for accumulation and image detection used to detect the face of the subject is obtained. Suppose you have accumulated for that.

  In this manner, in order to determine where the tracking target has moved in the image obtained this time, a search area is set based on the position of the tracking area in the image obtained last time. That is, since the tracking area of the previous image is an area around the center of the AF frame 3 where the face area of the subject exists in the state of FIG. 7B, the search area is changed from the previous area accordingly. If there is an area that matches the tracking area in the search area, the AF frame that exists in that area is set as an AF frame that indicates the AF area to be focused next. In FIG. 7C, the AF frame 4 corresponds to that. Then, after AF control is performed so that an area corresponding to the AF frame 4 is focused, imaging is performed.

  Similarly, FIG. 7D in which the position of the main subject has moved further from FIG. 7C is detected by face detection calculation using an image signal accumulated with the subject at the position of FIG. 7C. The search area is set with the face area as the tracking area, and the tracking target is searched.

  After that, by performing tracking calculation using the face detection result before each shooting in continuous shooting, the main subject that is the tracking target in the initial state, especially the focus area of the main subject is always in focus It can be performed.

  In FIG. 7, AF control is performed so that the AF area corresponding to the detected face area of the subject is in focus. However, since the lower area of the subject's face area is also considered to have substantially the same subject distance as the face area, the subject's face area is used when there is no AF area corresponding to the detected face area of the subject. The AF area corresponding to the lower area may be focused.

  As described above, the accumulation operation by the photometric sensor 106 is performed a plurality of times before each photographing at the time of continuous photographing, and subject tracking is performed based on the image signal obtained by the first accumulation operation, thereby continuously Subject tracking can be performed without reducing the shooting speed. In addition, by performing exposure control based on image signals obtained by a plurality of accumulation operations, even if the accumulation time of one accumulation operation is shorter than the flicker cycle, the exposure that reduces the influence of flicker Control can be performed.

  In addition, by using the face detection result based on the image signal obtained by accumulation by the photometric sensor 10 in the previous mirror-down state for the tracking calculation for the current imaging, the subject can be captured without reducing the continuous shooting speed. Subject tracking reflecting the detection result of detection can be performed.

  In the present embodiment, the case where the luminance pattern and the color pattern that are the reference for the tracking calculation are updated every time an image used for subject tracking is obtained is described. However, the luminance pattern and the color pattern that are initially determined as the tracking reference are described. The tracking calculation may be performed while maintaining

  In this embodiment, the accumulation used for the photometric calculation is performed a plurality of times as in the accumulation a1 and the accumulation b1. If a sufficient accumulation time can be secured, the accumulation used for the photometric calculation need not be performed a plurality of times. Or, even when continuous shooting is performed, if the continuous shooting speed is higher than the predetermined value, accumulation used for photometry calculation is performed multiple times, and if the continuous shooting speed is not higher than the predetermined value, the photometry calculation is performed. The accumulation used may not be performed a plurality of times.

  In the present embodiment, the face area of a subject that is a person is detected by face detection calculation. However, the subject detection may be performed using a subject area that has other predetermined conditions as a detection target. For example, a subject area to be detected by the user may be set in advance, and the subject area set in the subsequent subject detection calculation may be detected.

100 Camera body 101 CPU
102 Image sensor 106 Photometric sensor 109 Focus detection circuit 111 ICPU
200 Lens unit 201 LCPU

Claims (13)

Imaging means;
Charge storage means for storing charges according to the amount of incident light;
Tracking means for tracking the subject;
Exposure control means for performing exposure control,
The charge storage means performs a second accumulation after the first accumulation,
The tracking means performs the tracking based on the image signal obtained by performing the first accumulation without using the image signal obtained by performing the second accumulation,
Said exposure control means, said first accumulating image signals and the obtained by performing on the basis of the second image signal obtained by performing accumulation of the imaging device and performs Exposure control. An optical path changing means for changing an optical path of a light beam incident through the taking lens into a first state leading to the charge storage means and a second state leading to the imaging means;
The imaging apparatus according to claim 1, wherein the charge accumulation unit performs the first accumulation and the second accumulation when the optical path is in the first state. The imaging device is capable of continuous shooting,
The optical path changing means sets the optical path to the first state after imaging by the imaging means with the optical path set to the second state when imaging by the imaging means,
The charge accumulating means may be configured such that the first optical path is changed from the first state to the second state after the optical path is changed from the second state to the first state. The imaging apparatus according to claim 2, wherein accumulation and the second accumulation are performed.   The imaging apparatus according to claim 3, wherein the charge accumulation unit performs the first accumulation and the second accumulation when a continuous photographing speed in continuous photographing is higher than a predetermined value.   The exposure control means is based on an average value of a luminance value based on the image signal obtained by performing the first accumulation and a luminance value based on the image signal obtained by performing the second accumulation. The image pickup apparatus according to claim 1, wherein exposure control is performed.   The imaging apparatus according to claim 5, wherein the average value is a weighted average value. Focus adjusting means for performing focus adjustment based on the tracking result of the tracking means,
The tracking means, the imaging apparatus according to any one of the to the focusing means claims 2, characterized in that to terminate the processing of the tracking before performing the focus adjustment 4.   The imaging apparatus according to claim 7, wherein the focus adjustment unit performs the focus adjustment when the optical path is in the second state.   8. The charge accumulation unit performs the first accumulation in an accumulation time such that the tracking calculation process by the tracking unit can be completed before the focus adjustment unit performs the focus adjustment. Or the imaging device of 8.   The charge accumulating means includes the first accumulation and the second accumulation so that the sum of the accumulation time of the first accumulation and the accumulation time of the second accumulation is substantially equal to an integral multiple of the light amount change period of the light source. The image pickup apparatus according to claim 1, wherein accumulation of 2 is performed. At least one of the first accumulation and the second accumulation is to perform intermittent accumulation multiple times,
2. The charge storage unit according to claim 1, wherein the charge storage unit outputs the image signal after all of the plurality of storages as one of the first storage and the second storage is completed. The imaging apparatus according to any one of 10.   The imaging apparatus according to claim 1, wherein the tracking unit performs tracking of a target that satisfies a predetermined condition. A control method for an imaging apparatus comprising: an imaging unit; and a charge accumulation unit that accumulates charges according to an incident light amount,
A first charge accumulation step of performing first accumulation by the charge accumulation means;
A second charge accumulation step of performing a second accumulation after the first accumulation;
A tracking step of tracking a subject based on the image signal obtained by performing the first accumulation without using the image signal obtained by performing the second accumulation;
An exposure control step of performing exposure control based on the image signal obtained by performing the first accumulation and the image signal obtained by performing the second accumulation. Control method.

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