JP2012226206A - Image tracking device and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image tracking device able to track a subject portion suitable for focus adjustment, and an imaging apparatus.SOLUTION: The image tracking device comprises: input means to which an image signal obtained by picking up a subject image is input; tracking area setting means for setting within a photographic screen a tracking area including a subject portion to be tracked; focus detection means for detecting a focus for the subject image within a photographic screen; storage means for storing the result of focus detection carried out by the focus detection means within the tracking area; estimation mans for estimating, as candidate areas, areas after the movement of the subject portion to be tracked, which has moved within the photographic screen; and selection means for selecting a new tracking area from the plurality of candidate areas by comparing the result of each focus detection carried out by the focus detection means at each of the estimated candidate areas with the result of the focus detection stored in the storage means.

Description

  The present invention relates to an image tracking device and an imaging device.

  An area (tracking area) including the subject portion to be tracked is set in the captured image, the image in the tracking area is stored as a template image, and the similarity between the image repeatedly captured and the template image is high. There is known an image tracking device that searches an area and moves the tracking area to the area to track the subject portion (for example, Patent Document 1).

JP 2008-187331 A

  The image tracking device described in Patent Document 1 has a problem that focus adjustment cannot be performed correctly when the subject portion to be tracked has a low contrast.

The invention according to claim 1 is an input means for inputting an image signal obtained by capturing a subject image, a tracking area setting means for setting a tracking area including a subject portion to be tracked in a shooting screen, Based on the focus detection unit that performs focus detection on the subject image, the storage unit that stores the result of the focus detection performed by the focus detection unit in the tracking area, and the image signal input to the input unit, An estimation means for estimating a plurality of regions after the movement of the subject portion of the tracking target that has been moved as a candidate region, a result of each focus detection performed by the focus detection means in each of the estimated plurality of candidate regions, and storage An image tracking apparatus comprising: a selection unit that compares a result of focus detection stored in the unit and selects a new tracking region from a plurality of candidate regions. That.
According to a third aspect of the present invention, there is provided an input unit for inputting an image signal obtained by capturing a subject image, a first tracking region setting unit for setting a tracking region including a subject portion to be tracked in a photographing screen, and photographing. Based on the focus detection means for performing focus detection on the subject image in the screen, the storage means for storing the result of focus detection performed by the focus detection means in the tracking area, and the image signal input to the input means, Estimating means for estimating the moved area of the tracking target object portion moved within the shooting screen as a candidate area, search area setting means for setting a search area that includes the candidate area and is smaller than the shooting screen, and a plurality of search areas within the search area Compare the result of each focus detection performed by the focus detection means at each location with the result of focus detection stored in the storage means and A second tracking area setting means for setting a tracking area, an image tracking apparatus comprising: a.
An invention according to claim 4 includes the image tracking device according to any one of claims 1 to 3, and an imaging unit that captures a subject image and outputs an image signal to an input unit. It is an imaging device.

  According to the present invention, a subject portion suitable for focus adjustment can be tracked.

It is a block diagram which shows the whole structure of the camera to which this invention is applied. It is a figure which shows the focus area a set in the imaging | photography screen 17 of an imaging optical system. It is a figure which shows the example of a tracking area | region. It is a flowchart which shows the automatic focus adjustment process of 1st Embodiment. It is a flowchart which shows the initial tracking control of the tracking control part 36 in FIG.4 S302. It is a flowchart which shows the tracking calculation process of step S304 of FIG. It is a figure which shows an example of a candidate area | region. It is a flowchart which shows the automatic focus adjustment process of 2nd Embodiment.

(First embodiment)
FIG. 1 is a block diagram showing the overall configuration of a camera to which the present invention is applied. The camera 1 is a so-called digital single-lens reflex camera including a camera body 10 and an interchangeable lens 20 that can be attached to and detached from the camera body 10. The interchangeable lens 20 includes a plurality of lens groups L1, L2, and L3 that form an imaging optical system, and a lens driving motor 22 inside the lens barrel 21. The lens group L <b> 2 is a focus adjustment lens that can move in the direction of the optical axis OA and adjust the imaging position, and is driven by a lens driving motor 22. The lens driving motor 22 is controlled by a control device 30 provided in the camera body 10 described later.

  The camera body 10 includes an image sensor 11, a quick return mirror 12A, a sub mirror 12B, a finder optical system 13, a photometry unit 14, a phase difference AF detection unit 15, an operation member 16, and a control device 30. I have.

  The imaging element 11 is a photoelectric conversion element such as a CCD or CMOS that converts subject light into an electrical signal, and each pixel of red (R), green (G), and blue (B) is arranged in a predetermined arrangement pattern. ing. The imaging element 11 captures a subject image formed on the imaging surface by the imaging optical system of the interchangeable lens 20 and outputs an image signal corresponding to color information and luminance information corresponding to each pixel to the control device 30. .

  The quick return mirror 12A is provided so as to be movable between a working position interposed in the optical path from the imaging optical system of the interchangeable lens 20 to the image pickup device 11 and a retracted position not interposed in the optical path. The quick return mirror 12A reflects the incident light beam to the finder optical system 13 (finder screen 13A) at the operating position. In addition, a semi-transmission region that transmits part of the incident light beam is formed in part of the quick return mirror 12A.

  The sub mirror 12B is provided on the back side of the quick return mirror 12A. The sub mirror 12 </ b> B reflects the incident light beam transmitted through the semi-transmissive region of the quick return mirror 12 </ b> A toward the phase difference AF detection unit 15.

  The viewfinder optical system 13 includes a viewfinder screen 13A, a pentaprism 13B, and an eyepiece lens 13C. The finder screen 13A is provided at a position optically equivalent to the image sensor 11, and an incident light beam guided by the quick return mirror 12A forms an image. The pentaprism 13B and the eyepiece 13C are configured so that the photographer can visually recognize the subject image formed on the finder screen 13A as an erect image.

  The photometric unit 14 includes a photometric lens 14A and a photometric sensor 14B. The photometric lens 14A guides the subject image formed on the finder screen 13A to the photometric sensor 14B via the pentaprism 13B. Similar to the image sensor 11, the photometric sensor 14B has red (R), green (G), and blue (B) pixels arranged in a predetermined arrangement pattern, and forms an image on an image plane by a lens optical system. The subject image is captured and an image signal is output. The control device 30 detects the brightness of the imaging surface based on the image signal from the photometric sensor 14B, and determines the exposure. Moreover, the control apparatus 30 performs tracking control by the tracking control part 36 mentioned later based on the image signal input from the photometry sensor 14B.

  The operation member 16 is configured by various switches (not shown) for operating the camera 1. For example, a mode selection switch for selecting the operation mode of the camera 1, an area selection switch for selecting a focus area, a release button for instructing the start of automatic focus adjustment and photographing, and the like are included.

  FIG. 2 is a diagram showing the focus area a set in the photographing screen 17 of the photographing optical system. The phase difference AF detection unit 15 has a plurality of focus areas a at predetermined positions on the shooting screen 17. In the present embodiment, as shown in FIG. 2, 49 focus areas (also referred to as focus detection areas, distance measuring points, and AF areas) are provided on the entire photographing screen.

  Further, the phase difference AF detection unit 15 has a line sensor arranged corresponding to each focus area. The line sensor is a pair of charge storage type photoelectric conversion element arrays (CCD line sensor or the like). A pair of luminous fluxes divided into two passing through different regions of the interchangeable lens 20 are condensed by the condenser lens, and the pair of subject images are re-formed on the line sensor. Then, the line sensor accumulates electric charges for a set time for the pair of subject images, and outputs an AF image detection signal corresponding to the luminance distribution of the pair of subject images. The charge accumulation time of the line sensor is controlled by an AF-CCD control unit 31 in the control device 30 described later.

  The control device 30 is configured by a CPU, a memory, and the like, and controls the operation of the camera 1. Further, information necessary for these processes and controls is temporarily stored. As described above, the control device 30 detects the brightness of the imaging surface based on the photometric signal from the photometric sensor 14B and determines the exposure.

  Further, as shown in FIG. 1, the control device 30 includes an AF-CCD control unit 31, a defocus calculation unit 32, a focus area position determination unit 33, and a lens drive amount calculation as functional units related to automatic focus adjustment. Unit 34, lens drive control unit 35, tracking control unit 36, and storage unit 37.

  The AF-CCD control unit 31 reads out an AF image detection signal from a line sensor provided in the phase difference AF detection unit 15 and outputs it to the defocus calculation unit 32. Based on the AF image detection signal of the line sensor read by the AF-CCD control unit 31, the defocus calculation unit 32 performs focus detection on the subject image in the shooting screen, and adjusts the focus adjustment state of the interchangeable lens 20 ( A defocus amount representing a focus shift amount is calculated for each focus area a.

  The focus area position determination unit 33 is a focus area (hereinafter referred to as target focus) for finally focusing the interchangeable lens 20 based on the defocus amount calculated by the defocus calculation unit 32, the result of tracking control described later, and the like. Area). The focus area position determination unit 33 that has determined the target focus area stores the defocus amount of the target focus area in the storage unit 37.

  The lens drive amount calculation unit 34 calculates the drive amount of the focus adjustment lens (lens group L2) for focusing on the subject portion of the target focus area. In the present embodiment, the lens target position that is the target of the driving position of the focus adjustment lens (lens group L2) is calculated based on the defocus amount of the target focus area calculated by the defocus calculation unit 32, so that the lens The drive amount is calculated. The lens target position corresponds to the position of the focus adjustment lens (lens group L2) at which the defocus amount in the target focus area is almost zero.

  The lens drive controller 35 controls the driving of the lens driving motor 22 of the interchangeable lens 20 based on the lens driving amount calculated by the lens driving amount calculator 34, that is, the lens target position with respect to the focus adjustment lens (lens group L2). Output a signal. In response to this drive control signal, the lens drive motor 22 drives the focus adjustment lens (lens group L2) and moves it to the lens target position, thereby performing automatic focus adjustment.

(Description of tracking control)
The tracking control executed by the tracking control unit 36 will be described. The tracking control unit 36 performs tracking control for tracking a specific subject portion by well-known template matching or the like. In the present embodiment, prior to the execution of the tracking control, the user inputs a focus area used for the tracking process by the operation member 16. At the start of tracking control, the tracking control unit 36 sets a tracking area including the subject portion to be tracked in the shooting screen with reference to the position of the focus area on the shooting screen. With this setting, the coordinates of the tracking area and the template image are stored in the storage unit 37.

  FIG. 3 is a diagram illustrating an example of the tracking area. As shown in FIG. 3A, when the user selects the focus area a1 in the shooting screen 17 by the operation member 16, the tracking control unit 36 includes a tracking area having a predetermined size including the focus area a1 and larger than the focus area a1. Set b1. The tracking area b1 is set by detecting an area having color information similar to the color information of the subject portion in the focus area a1 around the focus area a1. The tracking control unit 36 stores the coordinates of the tracking region b1 and a rectangular image corresponding to the tracking region b1 in the storage unit 37. Note that the size of the tracking area b1 may be fixed or variable. When the size of the tracking area b1 is fixed, the storage unit 37 only needs to store the coordinates of any of the four corners as information for specifying the position of the tracking area b1.

  The tracking control unit 36 then stores the image signal output from the photometric sensor 14B at predetermined intervals (for example, 1/60 seconds) by matching with the template image stored in the storage unit 37. The coordinates of the tracking area and the template image stored in the unit 37 are repeatedly updated. FIG. 3B is a diagram showing the tracking area after update. The tracking area b1 located near the center of the shooting screen 17 in FIG. 3A has moved to a position near the upper right of the shooting screen 17 in FIG.

  When the tracking control unit 36 of the present embodiment updates the tracking area, based on the image signal input from the photometric sensor 14B, the area after the movement of the tracking target subject portion that has moved in the shooting screen is used as a candidate area. Estimate multiple. In this embodiment, this estimation is a comparison with the template image at a plurality of locations of the image signal, and the similarity to the template image at each of the plurality of locations (a numerical value indicating the degree of matching with the template image). In the form, the larger the value, the better the image matches the template image). The tracking control unit 36 stores all regions in which the calculated similarity is equal to or greater than a predetermined threshold as candidate regions and stores them in the storage unit 37.

  The tracking control unit 36 temporarily stores the candidate region having the highest similarity among the plurality of candidate regions as a new tracking region in the storage unit 37 (the tracking region coordinates and the template stored in the storage unit 37) Update the image). If the focus area corresponding to the provisional tracking area is suitable for focus adjustment, the focus area position determination unit 33 determines the focus area as the target focus area.

  On the other hand, when the focus area corresponding to the provisional tracking area is not suitable for focus adjustment, the focus area position determination unit 33 performs focus adjustment from the focus area corresponding to each of the candidate areas stored in the storage unit 37. Select a suitable focus area and determine the target focus area. In this case, the tracking control unit 36 selects a candidate area corresponding to the target focus area as a new tracking area.

  That is, if the focus area corresponding to the provisional tracking area is not suitable for focus adjustment and there is a candidate area corresponding to the focus area suitable for focus adjustment in the candidate area stored in the storage unit 37, tracking control is performed. The unit 36 selects the candidate region as a new tracking region (stores it in the storage unit 37). On the other hand, if the focus area corresponding to the provisional tracking area is suitable for focus adjustment, the provisional tracking area is directly used as a new tracking area.

  In the present embodiment, the “focus area corresponding to the tracking area (candidate area)” is all the focus areas in which more than half of the entire focus area is included in the tracking area (candidate area). This may be, for example, all focus areas in which the entire focus area is included in the tracking area, or all focus areas in which at least a part is included in the tracking area.

  In the present embodiment, the “focus area suitable for focus adjustment” is determined by defocus amount calculated this time in the focus area and defocus amount stored in the storage unit 37 (defocus of the previous target focus area). The focus area is such that the difference from the (quantity) is less than a predetermined threshold value. Since it is unlikely that the distance between the subject portion to be tracked and the camera 1 changes rapidly in a short time, the focus position during subject tracking is determined by determining whether or not the distance is suitable for focus adjustment as described above. Rapid changes can be suppressed. Note that, for example, whether or not the focus area is suitable for focus adjustment may be determined based on the absolute value of the defocus amount, the strength of contrast, or the like.

(Description of automatic focus adjustment process)
FIG. 4 is a flowchart showing the automatic focus adjustment process of the present embodiment. When a predetermined AF operation (for example, a half-press operation of a release button included in the operation member 16) is performed, the control device 30 repeatedly executes the automatic focus adjustment process shown in FIG. Thereby, during the AF operation, the focus position also changes according to the movement of the subject, so that the subject can be kept in focus.

  The following describes the processing when the focus area corresponding to the tracking area continues to be in a state suitable for focus adjustment, and then the focus area corresponding to the tracking area becomes unsuitable for focus adjustment at a certain point in time. Processing will be described.

  In step S302, the control device 30 determines whether or not the AF operation is a first AF operation. That is, the stage where no AF calculation result is output immediately after the AF operation is started is determined as the first AF operation. In the case of the first AF operation, the process proceeds to step S303. In step S303, the control device 30 performs the initial tracking control shown in FIG.

  FIG. 5 is a flowchart showing the initial tracking control of the tracking control unit 36 in step S302 of FIG. In step S101, the tracking control unit 36 obtains the color information of the subject of the image in the area corresponding to the focus area (focus area a1 shown in FIG. 3) designated by the user in the image signal input by the photometric sensor 14B. Remember. In step S102, the tracking control unit 36 detects an area indicating color information similar to the color information of the focus area a1 in the periphery of the focus area a1 in the image signal.

  In step S <b> 103, the tracking control unit 36 sets the detected region as the tracking region b <b> 1 and stores the coordinates in the storage unit 37. In step S104, the tracking control unit 36 stores the color information of the tracking region b1 in the storage unit 37 as a template image used for the subsequent tracking processing. In step S105, the tracking control unit 36 sets an area obtained by enlarging the tracking area b1 by a predetermined pixel as a search range.

  Returning to FIG. 4, the automatic focus adjustment process will be described. When the initial tracking control in step S302 described in FIG. 5 ends, the process proceeds to step S306. In step S306, the control device 30 sets a focus area corresponding to the tracking area b1 stored in step S103 as an AF calculation area (a focus area where the defocus calculation unit 32 calculates the defocus amount). In the first AF operation, the “focus area corresponding to the tracking area b1” is one focus area located in the center of the tracking area b1. In step S307, the control device 30 gives an instruction from the AF-CCD control unit 31, and causes the phase difference AF detection unit 15 (line sensor) to perform accumulation control.

  In step S308, the control device 30 performs A / D conversion of the charge accumulated in the phase difference AF detection unit 15 (line sensor) by the AF-CCD control unit 31, and calculates an image shift amount from the read charge signal by a known correlation calculation. Then, the defocus calculation unit 32 calculates the defocus amount. In subsequent step S309, control device 30 determines whether or not the calculation of the defocus amount for the predetermined number of areas has been completed. The predetermined number here is the number of focus areas corresponding to the tracking area b1 (one at the time of the first AF operation). When the calculation of the defocus amount ends, the process proceeds to step S310.

  If all the areas included in the phase difference AF detection unit 15 can be calculated at high speed, the defocus amounts of all the focus areas may be calculated in steps S306 to S309.

  In step S <b> 310, the control device 30 makes the focus area position determination unit 33 determine whether to select a focus area to be focused. In this selection determination, the focus area corresponding to the tracking area b1 and the defocus amount satisfying the predetermined condition is selected as the focus area (target focus area) to be focused. At the time of the first AF operation, the predetermined condition is determined as “the defocus amount is equal to or less than a predetermined threshold value”, for example. If the focus area corresponding to the tracking area b1 does not satisfy this predetermined condition, the target focus area is not selected in step S310.

  In step S311, the control device 30 determines whether or not a target focus area has been selected in step S310. If the target focus area is selected, the process proceeds to step S312. In step S <b> 312, the control device 30 performs lens drive amount calculation by the lens drive amount calculation unit 34 based on the defocus amount of the target focus area. In step S313, the control device 30 drives the lens driving motor 22 by the lens driving control unit 35 according to the result of the lens driving amount calculation in step S312, and moves the focus adjustment lens (lens group L2) to the lens target position. To adjust the focus.

  Next, when the process shown in FIG. 4 is executed, the control device 30 determines that the first AF operation is not performed in step S302, and the process proceeds to step S304. In step S304, the control device 30 performs the tracking calculation control shown in FIG.

  FIG. 6 is a flowchart showing the tracking calculation control in step S304 of FIG. In step S201, the tracking control unit 36 sequentially cuts out a region having the same size as the template image (the same size as the tracking region b1) from the search range set in step S105 (FIG. 5), and extracts the cut out image and the template image. In contrast, the difference in color information is calculated for each pixel. A numerical value obtained by inverting the magnitude of the difference in the color information is the similarity in this embodiment. In step S202, the tracking control unit 36 searches for regions where the degree of similarity is greater than a predetermined threshold (that is, a region where the difference in color information is equal to or smaller than a predetermined value), and sets these regions as candidate regions.

  In the present embodiment, a plurality of areas are defined in advance around the tracking area, color information differences are calculated for each of these areas in the same manner as in step S201, and areas whose difference is equal to or smaller than a predetermined threshold value are candidates. Estimate as a region. Note that the candidate area may be estimated by scanning while shifting the search range by one pixel.

  In step S203, the tracking control unit 36 tentatively selects a candidate area having the highest similarity (the smallest difference in color information) from the plurality of candidate areas estimated in step S202 as a tracking area. Here, the image information of the template image stored in the storage unit 37 may be updated using the image information of the provisional tracking area.

  FIG. 7 is a diagram illustrating an example of a candidate area. 7A and 7B, nine candidate areas 602a to 602i are estimated, and the candidate area 602i is set as a provisional tracking area. There are other methods for estimating the candidate area. For example, an area having the same size as the tracking area b1 is sequentially cut out in the area 601 obtained by enlarging the tracking area by a predetermined amount around the area, as in step S201. The difference may be calculated, and an area having a predetermined threshold value or less (an area having a similarity greater than or equal to a predetermined threshold value) may be set as a candidate area. Alternatively, a plurality of areas may be defined around the tracking area in advance, and the plurality of areas may be unconditionally estimated as candidate areas without calculating the color information difference. In step S204, the tracking control unit 36 sets an area obtained by enlarging the provisional tracking area by a predetermined number of pixels around as a new search range.

  Returning to FIG. 4, the automatic focus adjustment process will be described. When the tracking calculation control in step S304 described in FIG. 6 ends, the process proceeds to step S306. In step S306, as in the first AF operation, the focus area corresponding to the tracking area b1 is set as the AF calculation area. From the second time on, the “focus area corresponding to the tracking area b1” is a focus area where the area overlapping the tracking area b1 is a predetermined amount or more among the focus areas at least partially overlapping the tracking area b1. Accordingly, the “focus area corresponding to the tracking area b1” is a plurality of focus areas, and in step S306, the plurality of focus areas are set as AF calculation areas.

  The processing executed in steps S307 to S309 is the same as in the first AF operation. In step S310, as in the first AF operation, the control device 30 selects, from the focus area corresponding to the tracking area b1, a defocus amount that satisfies a predetermined condition as a focus adjustment target focus area (target focus area). . This predetermined condition is determined such that “the difference from the defocus amount of the previous target focus area is less than a predetermined value and the absolute value of the defocus amount is minimum”. By setting the conditions as described above, it is possible to prevent focusing from being performed at a position that is significantly different from the previous (immediately previous) focus position in the optical axis direction. When there is no focus area that satisfies the above-mentioned predetermined condition in the focus area corresponding to the tracking area b1, the point that the adopted area is not selected is the same as in the first AF operation.

  The processing executed in steps S311 to S313 is the same as in the first AF operation. As described above, as long as the target focus area is selected in step S310, the control device 30 repeatedly executes the above-described processing, and the tracking area is updated one after another according to the movement of the subject portion to be tracked. In addition, since the focus adjustment is sequentially performed on the updated tracking area, it is possible to maintain a state where the moving subject is always in focus.

  Next, a case where the target focus area is not selected in step S310 will be described. In this case, the process proceeds to step S314. In step S314, the control device 30 determines whether or not the AF operation is the initial AF operation, similarly to step S302. That is, the initial AF operation is performed immediately after the AF operation is performed and no AF calculation result is output. If it is the first AF operation, the process proceeds to step S321. In step S321, the control device 30 performs a so-called low contrast scan operation. That is, the lens drive motor 22 is driven by the lens drive control unit 35, and the focus adjustment lens (lens group L2) is moved by a predetermined amount (or to a predetermined position) in a predetermined direction (for example, infinity direction). At this time, the next AF operation is treated as the first AF operation.

  On the other hand, if it is not the first AF operation, the process proceeds from step S314 to step S315. In step S315, the control device 30 sets an AF calculation area as in step S306. However, instead of the focus area corresponding to the tracking area b1, the focus area corresponding to each candidate area estimated in step S304 is set as the AF calculation area. Note that the focus area already set as the AF calculation area in step S306 need not be set as the AF calculation area in step S315. This is because the defocus amount of the focus area has already been calculated in step S308.

  In step S316, similarly to step S308, the defocus amount of the AF calculation area set in step S315 is calculated. In step S317, the control device 30 determines whether or not the defocus amount calculation has been completed for all AF calculation areas. If all the calculations of the defocus amount have been completed, the process proceeds to step S318. In step S318, as in step S310, the control device 30 selects, as the target focus area, a defocus amount satisfying a predetermined condition from all the focus areas set in the AF calculation area in step S315. In step S318, the focus area position determination unit 33 changes the focus area of the candidate area close to the provisional tracking area and the focus area of the candidate area that overlaps with the focus area corresponding to the provisional tracking area. Select with priority over the focus area.

  In step S319, the control device 30 determines whether any focus area is selected as the target focus area in step S318. If the target focus area is not selected, the process proceeds to step S321, and the scan operation is performed as described above. On the other hand, if the target focus area has been selected, the process proceeds to step S320. In step S320, the control device 30 controls the tracking control unit 36 for the next tracking control based on the target focus area selected in step S318, such as the position information of the target focus area and information on candidate areas corresponding to the target focus area. Outputs information to ensure that is performed. The tracking control unit 36 receives the information output here, and stores a new tracking region (a candidate region corresponding to the target focus area) in the storage unit 37. Thereafter, the process proceeds to step S312, and the lens drive amount calculation unit 34 calculates the lens drive amount based on the determined defocus amount of the target focus area. In step S313, the control device 30 drives the lens driving motor 22 by the lens driving control unit 35 according to the result of the lens driving amount calculation in step S312, and moves the focus adjustment lens (lens group L2) to the lens target position. To adjust the focus.

According to the camera system according to the first embodiment described above, the following operational effects can be obtained.
(1) The tracking control unit 36 sets a tracking area including the subject portion to be tracked in the shooting screen, and moves on the shooting screen based on the image signal input from the photometric sensor 14B. A plurality of regions after partial movement are estimated as candidate regions. Then, each defocus amount calculated by the defocus calculation unit 32 in each of the estimated plurality of candidate regions is compared with the defocus amount stored in the storage unit 37, and a new one is obtained from the plurality of candidate regions. Select a tracking area. Since it did in this way, the to-be-photographed object part suitable for focus adjustment can be tracked. For example, if a tracking area is set for a low-contrast subject portion by tracking control, an appropriate defocus amount may not be calculated in the corresponding focus area. Thus, the tracking area can be automatically reset to a position more suitable for focus adjustment, and tracking control can be continued.

(2) The tracking control unit 36 compares the template image in the tracking region at a plurality of locations of the image signal, calculates the similarity with the template image at each of the plurality of locations, and based on the plurality of similarities A plurality of candidate regions are estimated. For the candidate area (provisional tracking area) with the highest similarity, the defocus amount calculated by the defocus calculation unit 32 and the defocus amount stored in the storage unit 37 in the candidate region are predetermined. If it is closer than that, the candidate area is selected as a new tracking area, and if it is not closer than the predetermined area, a candidate area different from the candidate area is selected as a new tracking area. Since it did in this way, the calculation amount for determining a new tracking area | region can be reduced. That is, if the focus area corresponding to the provisional tracking area is suitable for focus adjustment, it is not necessary to calculate the defocus amount for other focus areas.

(Second Embodiment)
In the first embodiment, a plurality of candidate areas are first estimated, and then the tracking area is finely adjusted based on the defocus amount. In the camera 1 according to the second embodiment, after only one candidate area is determined, a focus area (target focus area) to be adjusted is selected from the focus areas located around the candidate area, and the target area is selected. A new tracking area is set based on the position of the focus area. In the following description, description of the same parts as in the first embodiment will be omitted.

  FIG. 8 is a flowchart illustrating an automatic focus adjustment process according to the second embodiment. The description of the same parts as those in the automatic focus adjustment process of the first embodiment shown in FIG. 4 is omitted. In step S401, the control device 30 sets a search area that includes the tracking area b1 stored in step S305 and is smaller than the shooting screen. Then, all the focus areas included in this search area are set as AF calculation areas.

  In step S402, the control device 30 causes the defocus calculation unit 32 to calculate the defocus amount for all the focus areas set in the AF calculation area in step S401. In step S403, the control device 30 determines the target focus area. Here, the control device 30 selects one focus area based on a predetermined condition for each focus area for which the defocus amount has been calculated in step S402. The predetermined conditions include, for example, that the contrast is higher than a predetermined level, that the difference from the defocus amount stored in the storage unit 37 is less than a predetermined threshold, that the image is close to the tracking area, etc. Various conditions can be set. The predetermined condition may be a combination of these conditions.

  In step S404, the control device 30 determines whether or not the new tracking area stored in the storage unit 37 in step S303 or step S304 needs to be corrected. Specifically, it is determined whether or not the focus adjustment target focus area (target focus area) selected in step S <b> 403 is a focus area in a new tracking area stored in the storage unit 37. If a focus area outside the tracking area has been selected, the tracking area stored in the storage unit 37 is reset (corrected) to a position including the focus area selected in step S403.

According to the camera system according to the second embodiment described above, the following operational effects can be obtained.
(1) Based on the image signal output from the photometric sensor 14B, the tracking control unit 36 estimates a region after movement of the tracking target subject portion that has moved within the shooting screen as a candidate region. After setting a search area that includes the candidate area and is smaller than the shooting screen, each defocus amount calculated by the defocus calculation unit 32 at each of a plurality of locations in the search area is stored in the storage unit 37. The defocus amount is compared, and a new tracking area is set at any of a plurality of locations. Since this is done, instead of increasing the calculation amount of the defocus amount, the tracking area is corrected more frequently according to the defocus amount, and the accuracy of subject tracking is improved.

  The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.

(Modification 1)
In the first embodiment described above, the candidate area with the highest similarity among the plurality of candidate areas is set as a provisional tracking area, and the defocus amount is calculated for this area first. Alternatively, the defocus amount may be calculated for all candidate areas. In this case, among the focus areas corresponding to each candidate area, the focus area most suitable for focus adjustment is determined as the target focus area, and the candidate area corresponding to the target focus area may be set as the tracking area.

(Modification 2)
The automatic focus adjustment control and tracking control in each of the above-described embodiments can be applied to so-called continuous shooting in which shooting is performed continuously in a short time.

(Modification 3)
In each of the above-described embodiments, the present invention is applied to a lens interchangeable single-lens reflex camera provided with a phase difference detection type focus detection device, but the present invention is not limited to such an embodiment. For example, the present invention can be applied even when focus detection is performed by a so-called hill-climbing method (contrast method). The present invention can also be applied to a lens-integrated camera.

(Modification 4)
The image sensor for subject tracking may be the image sensor 11 instead of the photometric sensor 14B. In this case, it is necessary to move the quick return mirror 12A to the retracted position during subject tracking.

(Modification 5)
The image tracking device of the present invention does not necessarily have to be integrated with an imaging device for subject tracking as in each of the embodiments described above. For example, an independent device to which an imaging device that captures a subject image and outputs an image signal can be connected. In this case, an input unit to which an image signal from the imaging device is input may be provided, and the imaging device may be connected to the input unit.

  As long as the characteristics of the present invention are not impaired, the present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. .

DESCRIPTION OF SYMBOLS 1 ... Camera, 10 ... Camera body, 20 ... Interchangeable lens, 15 ... Phase difference AF detection part, 30 ... Control apparatus, 31 ... AF-CCD control part, 32 ... Defocus calculating part, 33 ... Focus area position determination part, 34 ... Lens drive amount calculation unit, 35 ... Lens drive control unit, 36 ... Tracking control unit, 37 ... Storage unit

Claims (4)

Input means for inputting an image signal obtained by capturing a subject image;
Tracking area setting means for setting a tracking area including a subject portion to be tracked in a shooting screen;
Focus detection means for performing focus detection on the subject image in the shooting screen;
Storage means for storing a result of focus detection performed by the focus detection means in the tracking region;
Based on the image signal input to the input means, an estimation means for estimating a plurality of moved areas of the subject portion of the tracking target moved within the shooting screen as candidate areas;
A result of each focus detection performed by the focus detection unit in each of the estimated plurality of candidate regions is compared with a result of focus detection stored in the storage unit, and the results from the plurality of candidate regions are compared. A selection means for selecting a new tracking area;
An image tracking device comprising: The image tracking device according to claim 1,
The estimation means compares the image of the subject portion of the tracking target in the tracking area set by the tracking area setting means at a plurality of locations of the image signal, and the tracking target for each of the plurality of locations. Calculating the similarity with the image of the subject portion, estimating the plurality of candidate regions based on the plurality of similarities,
For the candidate area with the highest degree of similarity, the selection means has a result of focus detection performed by the focus detection means in the candidate area and a result of focus detection stored in the storage means greater than or equal to a predetermined value. The image is characterized in that if it is close, the candidate area is selected as the new tracking area, and if it is not closer than a predetermined area, the candidate area different from the candidate area is selected as the new tracking area. Tracking device. Input means for inputting an image signal obtained by capturing a subject image;
First tracking area setting means for setting a tracking area including a subject portion to be tracked in the shooting screen;
Focus detection means for performing focus detection on the subject image in the shooting screen;
Storage means for storing a result of focus detection performed by the focus detection means in the tracking region;
Estimating means for estimating, as a candidate area, an area after movement of the subject portion of the tracking target that has moved within the shooting screen, based on the image signal input to the input means;
Search area setting means for setting a search area that includes the candidate area and is smaller than the shooting screen;
The result of each focus detection performed by the focus detection unit at each of a plurality of locations in the search area is compared with the result of focus detection stored in the storage unit, and A second tracking area setting means for setting a new tracking area;
An image tracking device comprising: The image tracking device according to any one of claims 1 to 3,
An imaging unit that captures a subject image and outputs an image signal to the input unit;
An imaging apparatus comprising:

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