JP5550448B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus having a moving object detection unit that detects a moving object from a captured image.

  For automatic focus adjustment of an imaging apparatus such as a conventional single-lens reflex camera, phase difference detection is performed based on a signal from an autofocus sensor (hereinafter referred to as AF sensor), and the defocus amount at that time is calculated. A technique has been proposed in which correct focus adjustment is performed by repeatedly performing a 'focus detection, lens drive' cycle in which the lens is driven in a direction to eliminate the defocus amount. The lens driving amount in each cycle is based on the defocus amount at the time when focus detection is performed in that cycle. In the case of a subject with a large movement, the defocus amount may change during focus detection and lens driving, and the defocus amount to be eliminated may be different from the detected defocus amount. As a solution to this problem, the detected defocus amount and its time interval are stored, and a moving object prediction automatic focus adjustment (hereinafter referred to as “moving object prediction AF”) that corrects a lens driving amount by predicting a defocus change caused by the movement of the subject from the result. ) Has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 10-068865

  However, the conventional moving object prediction AF has the following problems. That is, during the release, the image pickup device is exposed to the mirror-up state, and the AF sensor is shielded from light so that defocus detection by the AF sensor cannot be performed. Therefore, if the release time (mirror up time or shooting time) is long, the defocus detection interval becomes long, the accuracy of moving object prediction is lowered, and the subject may be lost as a result.

(Object of invention)
An object of the present invention is to provide an imaging apparatus capable of reducing the loss of sight of a moving subject even when the release time is long.

In order to achieve the above object, an imaging apparatus according to the present invention includes a first imaging element, a second imaging element, and a first state that guides light from a subject that has passed through a lens to the second imaging element. A mirror member having a second state for guiding light from the subject that has passed through the lens to the first image sensor by retracting, and a plurality of output signals from the second image sensor . focus detection means for detecting a focus state of the focus area, as well as predicting the lenses driving amount from the result of the focus state of the multiple times that are repeatedly detected by the focus detection means, to perform the lens driving by the prediction calculation result and control means for, while detecting movement from the first of two or more images obtained from the output signal from the imaging device, a focus area that corresponds to the position of the middle et the body of the plurality of focus areas And a moving object detection means for selecting, said moving object detecting means, during the continuous shooting, in repeating the return from the retracted state and the retracted state of the mirror member, the control means, the moving object detection The lens driving is performed using the focus state of the focus area selected by the means.

  According to the present invention, it is possible to provide an imaging apparatus that can reduce the loss of sight of a moving subject even when the release time is long.

It is a block diagram which shows the outline of the single-lens reflex camera which concerns on each Example of this invention. It is a block diagram which shows the electrical constitution of the single-lens reflex camera of FIG. 3 is a flowchart illustrating an operation of the single-lens reflex camera according to the first embodiment. 3 is a flowchart illustrating a moving object detection operation according to the first embodiment. 3 is a flowchart illustrating a moving object detection calculation operation according to the first embodiment. 10 is a flowchart illustrating a moving object detection operation according to the second embodiment. 12 is a flowchart illustrating a moving object detection calculation operation according to the second embodiment.

  The mode for carrying out the present invention is as shown in Examples 1 and 2 below.

  FIG. 1 is a configuration diagram illustrating an outline of a single-lens reflex camera that is an imaging apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, reference numeral 1 denotes a photographic lens, which is shown as two lenses for convenience, but actually includes a large number of lenses. Reference numeral 2 denotes a main mirror, which is inclined or moved away from the photographing optical path according to the observation state and the photographing state. Reference numeral 3 denotes a sub-mirror that reflects a light beam transmitted through the main mirror 2 obliquely arranged with respect to the photographing optical path toward the lower side of the camera body. Reference numeral 4 denotes a shutter. Reference numeral 5 denotes a solid-state imaging device (hereinafter, imaging device) such as a CCD type or a CMOS type. Reference numeral 6 denotes a focus detection unit, which includes a field lens 6a, reflection mirrors 6b and 6c, a secondary imaging lens 6d, a diaphragm 6e, and an AF sensor 6f such as a plurality of CCDs disposed in the vicinity of the imaging surface. Focus detection is performed by a known phase difference method. Reference numeral 7 denotes a finder optical path changing pentaprism.

  Part of the light A from the subject that has passed through the photographing lens 1 is reflected by the main mirror 2, enters the pentaprism 7 and is guided to the eyepiece, and the remaining light passes through the main mirror 2 and passes through the sub-mirror 3. To the focus detection unit 6. At the time of observation, the main mirror 2 and the sub mirror 3 are in the state of entering the imaging optical path as shown in FIG. 1, but at the time of imaging, the main mirror 2 and the sub mirror 3 are withdrawn from the imaging optical path and the light A from the subject is guided to the imaging device 5. . That is, during the release for exposure of the image sensor 5, light is not guided to the focus detection unit 6 and the focus state cannot be detected.

  FIG. 2 is a block diagram showing an electrical configuration of the single-lens reflex camera.

  In FIG. 2, reference numeral 501 denotes a camera control unit, for example, a microcomputer having a CPU, a ROM, a RAM, and an A / D conversion function. The camera control unit 501 performs a series of camera operations using an automatic exposure control function, an automatic focus adjustment function, and the like according to a camera sequence program stored in the ROM. For this purpose, the camera control unit 501 communicates with the camera peripheral circuit and the lens using the synchronous communication signal and the communication selection signal, and controls the operation of each circuit, lens, and the like.

  Reference numeral 502 denotes an AF sensor (corresponding to the AF sensor 6f in FIG. 1) composed of a plurality of area sensors (hereinafter referred to as sensor units). A phase difference detection unit 503 detects a phase difference of the signal output from the AF sensor 502 using a known method, and a defocus amount 504 calculates a defocus amount from the phase difference detected by the phase difference detection unit 503. It is a calculation part. Reference numeral 505 denotes a lens driving amount calculation unit that calculates the lens driving amount using the input defocus amount, and the past defocus amount, its time interval, and a moving object input from the moving object detection unit 506 described later. Based on the detection result, the lens driving amount based on the moving object prediction is calculated.

  Reference numeral 506 denotes a moving object detection unit having a shooting screen storage RAM for storing an image therein. Reference numeral 507 denotes an image sensor that outputs a signal generated by photoelectric conversion as an image signal by A / D conversion (corresponding to the image sensor 5 in FIG. 1). ). Reference numeral 508 denotes a correction processing unit that corrects the image signal output from the image sensor 507, and 509 denotes an image processing unit that performs image processing from the signal corrected by the correction processing unit 508. Image data is generated from the image sensor 507 via the image processing unit 509 and the like, and stored in the RAM 510. The image data is also output to the moving object detection unit 506, where moving object detection is performed by calculating a difference value of the moving object, and the detection result is output to the lens driving amount calculation unit 505. Reference numeral 511 denotes a zoom lens (included in the photographing lens 1 in FIG. 1), 512 denotes an aperture, 513 denotes a lens (a focus lens included in the photographing lens 1 in FIG. 1), and 515 denotes a mirror (the main mirror 2 and the sub mirror 3 in FIG. 1). Equivalent). Reference numeral 514 denotes a shutter 515 (corresponding to the shutter 4 in FIG. 1).

  Next, a series of operations of the single-lens reflex camera having the above configuration will be described with reference to the flowchart of FIG.

  When a power switch (not shown) is turned on, power supply to the camera control unit 501 is started, and the camera control unit 501 starts operation from step S002 through step S001. First, in step S002, the state of the switch SW1 that is turned on by pressing the release button in the first stage is determined. If the switch W1 is off, the process proceeds to step S003, where all the control flags and variables set in the RAM 510 are cleared and initialized. Then, the process returns to step S002.

  Thereafter, when the switch SW1 is turned on, the process proceeds from step S002 to step S004, and a photometric operation for exposure control is executed. Specifically, the camera control unit 501 inputs the output of the photometric sensor to the analog input terminal, calculates the optimum shutter control value and aperture control value from the photometric value, and stores them at a predetermined address in the RAM 510. During the release operation, the shutter 515 and the aperture 512 are controlled based on these values.

  In the next step S005, an image signal is input from the AF sensor 502 including a plurality of sensor units having different focus areas (hereinafter referred to as AF areas). In the next step S006, focus detection calculation is performed to calculate the defocus amount by a known method based on the input image signal. In a succeeding step S007, it is determined whether or not a sensor unit change flag is set by a moving object detection operation described later. If not, the process immediately proceeds to step S009. However, if it is set, the process proceeds to step S008, and the sensor part (used sensor part) of the AF sensor 502 used for detecting the defocus amount is changed to the sensor part of the focus area where the moving object is detected by the moving object detection unit 506. Then, the process proceeds to step S009.

  In the next step S009, it is determined whether or not the lens drive suppression flag is set by the moving object detection operation as in the previous step S007, and if it is set, the process immediately proceeds to step S012. However, if it is not set, the process proceeds to step S010, and a prediction calculation operation is executed. This prediction calculation operation corrects the driving amount of the lens 513 using the defocus amount and lens driving amount of the past two times or more and the current defocus amount obtained from the sensor unit of the AF sensor 502 used this time. It is. Thereafter, the process proceeds to step S011, where the lens 513 is driven based on the lens driving amount corrected in the previous step S009, and the process proceeds to step S012.

  In the next step S012, the lens drive suppression flag is cleared. In the next step S013, the state of the switch SW2 that is turned on by pressing the release button in the second stage is determined. As a result, if the switch SW2 is OFF, the process proceeds to step S025, the image data flag indicating the state of the RAM storing the image data in the moving object detection unit 506 is cleared, and the process returns to step S002.

  As described above, until the switch SW1 is turned off or the switch SW2 is turned on, the above-described series of operations is repeatedly executed to perform preferable focus adjustment on the subject.

  When the switch SW2 is turned on in step S013, the process proceeds to step S014 and subsequent steps to start the release operation. First, in step S014, it is determined whether lens driving is being executed. If lens driving is in progress, the process proceeds to step S015, a lens drive stop command is sent to stop the lens 513, and the process proceeds to step S016. If the lens is not being driven, the process immediately proceeds to step S016.

  In the next step S016, the mirror 514 is raised. In the next step S017, the aperture 512 is controlled using the aperture control value obtained during the photometric operation in step S004. In a succeeding step S018, it is determined whether or not the control of the mirror up and the aperture 512 in the steps S016 and S017 is completed. If either of them is incomplete, the process waits in this step, and subsequently determines the state. If it is determined that the control of both is completed, the process proceeds to step S019.

  In step S019, the shutter 515 is controlled at the set shutter speed, and the image sensor 507 is exposed. When the control of the shutter 515 is completed, the process proceeds to step S020, the signal from the image sensor 507 is read, and correction processing, image processing, and the like are performed. In the subsequent step S021, the moving object detection unit 506 performs a moving object detection operation for detecting the movement of the subject using the read image. Details of the moving object detection operation will be described later with reference to the flowchart of FIG.

  In step S022, a command is sent to the lens 513 to open the aperture 512, and in the next step S023, the mirror 514 is lowered. In the subsequent step S024, as in step S018, the process waits for the mirror down and the opening of the aperture 512 to be completed. When both the mirror down and the opening control of the aperture 512 are completed, the process returns to step S002 to repeat a series of sequences.

  When continuous shooting is performed, that is, when the ON state of the switch SW2 continues, the process proceeds to step S004 in step S002 and to step S014 in step S013. By repeating this series of processes, the moving object detection unit 506 detects a moving object in step S021, and the result is reflected in the processes in steps S007 to S012.

  In addition, the switch SW2 is turned off after continuous shooting. Then, since the image data flag is cleared in step S025, when continuous shooting is started again, the moving object detection unit 506 performs a moving object detection in step S021 after a new image is read, and a moving object for an erroneous subject is detected. Prediction is avoided.

  FIG. 4 is a flowchart showing details of the moving object detection operation executed in step S021 of FIG.

  This moving object detection operation starts from step S102 via step S101. First, in step S102, the sensor unit change flag is cleared, and in the next step S103, an image data flag indicating the presence or absence of an image read by the moving object detection unit 506 is confirmed. If the image data flag is not set here, the process proceeds to step S104, and if it is set, the process proceeds to step S106.

  If the process proceeds to step S104 assuming that the image data flag is not set, the image data read in step S020 is read into the captured image storage RAM in the moving object detection unit 506. In the next step S105, the image data flag is set, and this moving object detection subroutine is terminated.

  If the image data flag is set in step S103, the process proceeds to step S106, and the latest image data is read into the captured image storage RAM in the moving object detection unit 506. In the next step S107, a moving object detection calculation operation is performed. The details of this moving object detection calculation operation will be described later with reference to the flowchart of FIG. 5. In this step, the presence or absence of moving objects is calculated from two images stored in the captured image storage RAM in the moving object detection unit 506. Then, a moving object detection flag indicating the presence or absence of a moving object is set or cleared. If there is a moving object, the sensor unit of the AF area where the moving object exists is specified.

  In the next step S108, the state of the moving object detection flag obtained in step S107 is determined. If the moving object detection flag is set, the process proceeds to step S109, and if not set, the moving object detection subroutine is terminated. The end of the moving object detection subroutine here means that the moving object detection information by the moving object detection unit 506 is not used for the prediction calculation in step S010.

  Since the moving body flag is set in step S108, the process proceeds to step S109. Here, it is confirmed whether or not the area in which the moving object is detected based on the position information of the moving object obtained by calculating the difference value of the image in step S107 is a corresponding AF area (hereinafter referred to as a corresponding area) of the AF sensor 502. In the next step S110, if the area where the moving object is detected is a corresponding area of the AF sensor 502 based on the confirmation result in step S109, the process proceeds to step S111. If the area is not a corresponding area of the AF sensor 502, the process proceeds to step S114. move on.

  When it is determined that the area where the moving object is detected is a corresponding area of the AF sensor 502 and the process proceeds to step S111, information indicating the sensor unit of the AF sensor 502 corresponding to the moving object detection area is stored as a variable or the like. In step S008 of FIG. 3, the sensor unit of the AF sensor 502 used for defocus amount calculation is changed using the information stored here. In the next step S112, the sensor unit of the AF sensor 502 corresponding to the moving object detection area stored in step S111 is compared with the sensor unit of the AF sensor 502 used immediately before the defocus amount calculation. If not, the moving object detection subroutine is terminated. If they are different, the process proceeds to step S113, the sensor unit change flag is set, and this moving object detection subroutine is terminated.

  As described above, when it is determined that the area in which the moving object is detected in step S110 is not the corresponding area of the AF sensor, that is, there is no sensor portion of the AF sensor 502 corresponding to the current position of the moving object, the process proceeds to step S114. Set the drive suppression flag. By setting this lens drive suppression flag, the lens drive in step S011 is suppressed when the defocus amount cannot be detected in the area where the moving object exists. For this reason, it is possible to prevent the prediction calculation and the driving of the lens 513 from being performed with an incorrect defocus amount, and it is possible to perform the prediction calculation with high accuracy.

  In this way, the moving object detection unit 506 detects the moving object, and obtains information on the sensor unit of the AF sensor 502 corresponding to the area where the moving object is detected. If the sensor part of the AF sensor 502 is different from the sensor part of the AF sensor used for the defocus amount calculation immediately before, the sensor part change flag is set, and the sensor part of the AF area 502 to be used is displayed. 3 is changed in step S008. Therefore, the lens drive amount calculation unit 505 cannot detect not only the defocus amount obtained from the AF sensor 502 but also the defocus amount, and the subject from the signal from the image sensor 507 can be obtained even when the mirror is being raised. It becomes possible to obtain information. As a result, it is possible to perform moving object prediction with higher accuracy than the prediction calculation conventionally performed only from the defocus amount of the AF sensor 502.

  In addition, when there is no moving object in the corresponding area of the AF sensor 502, the prediction calculation and the lens drive due to an incorrect defocus amount can be suppressed by not performing the prediction calculation and the driving of the lens 513. Focus adjustment can be reduced.

  FIG. 5 is a flowchart showing the moving object detection calculation operation executed in step S107 of FIG.

  This moving object detection calculation operation starts from step S202 via step S201. First, in step S202, a difference value between luminance information of two read images is calculated. In the next step S203, the presence / absence of a large difference that seems to be a moving object is detected from the difference value between the two images obtained in step S202. If a large difference, that is, a moving object can be detected, the process proceeds to step S204. If no moving object is detected, the process proceeds to step S205.

  If it is determined in step S203 that a moving object has been detected and the process proceeds to step S204, a moving object detection flag is set, and the moving object detection calculation subroutine ends. If it is determined that the moving object cannot be detected and the process proceeds to step S205, the moving object detection flag is cleared and the moving object detection calculation subroutine is terminated.

  With the above operation, the moving object detection unit 506 can detect the moving object based on the information obtained from the image sensor 507.

  According to the first embodiment, during continuous shooting, even during a mirror-up state where the conventional defocus detection by phase difference detection cannot be performed, moving object detection is performed based on the image data from the image sensor 507, and the result is obtained as described above. It is used together with the result of defocus detection. Therefore, it is possible to improve the accuracy of moving object prediction and reduce the loss of sight of the subject.

  In addition, the first embodiment also applies to an imaging apparatus that outputs a signal (such as a signal indicating the contrast of an image) other than at least a part of the photoelectric conversion cell group of the imaging element for forming an image signal. It is valid. This image pickup apparatus adjusts the optical system focus for connecting the subject to the image pickup device from the defocus amount by the signal.

  Next, a single-lens reflex camera according to Embodiment 2 of the present invention will be described. The configuration of the single-lens reflex camera is the same as that shown in FIGS. The series of operations is the same as the flowchart shown in FIG.

  In the second embodiment of the present invention, when the moving object detection unit 506 detects that the subject is moving in the front-rear direction with respect to the imaging surface, the moving object is predicted based on the distance information obtained from the AF sensor 502. Furthermore, when the subject is moving not only in the front-rear direction (in the optical axis) with respect to the imaging surface but also in the vertical and horizontal directions with respect to the imaging surface, the result detected from the moving object detection unit 506 in the conventional moving object prediction AF It is what is used.

  First, the moving object detection operation executed in step S021 of FIG. 3 will be described using the flowchart of FIG.

  First, when the moving object detection program is started by the moving object detection unit 506, the operation is started from step S302 through step S301. From step S302 to step S306, processing is performed in the same manner as step S102 to step S106 of FIG.

  In the next step S307, a moving object detection calculation operation is performed. The details of the moving object detection calculation operation will be described later with reference to the flowchart of FIG. 7, but in this step, the following operation is performed. That is, the presence / absence of a moving object is calculated from the two images stored in the captured image storage RAM in the moving object detection unit 506. Then, a moving object detection flag indicating the presence or absence of a moving object is set or cleared, and when the moving object moves in the front-rear direction with respect to the imaging surface, a defocus flag indicating that is set. If there is a moving object, the sensor unit of the AF area where the moving object exists is specified.

  In the next step S308, the state of the moving object detection flag obtained in step S307 is determined. If the moving object detection flag is set, the process proceeds to step S309, and if not set, the moving object detection subroutine is terminated.

  If the process proceeds to step S309 assuming that the moving object detection flag is set, the state of the defocus flag obtained in step S307 is determined. If the defocus flag is set, the process proceeds to step S315. In step S315, the defocus flag is cleared, and the moving object detection subroutine is terminated.

  If it is determined in step S309 that the defocus flag has not been set, the processes in steps S310 to S314 and S316 are performed, which are the same as steps S109 to S114 in FIG. Omitted.

  FIG. 7 is a flowchart showing the moving object detection calculation operation executed in step S307.

  This moving object detection calculation operation starts from step S402 via step S401. First, in step S402, the difference value between the luminance information of the two read images is calculated. Then, in the next step S403, the presence / absence of a large difference that seems to be a moving object is detected from the difference value between the two images obtained in step S402, and if it can be detected, the process proceeds to step S404. If so, the process proceeds to step S407.

  If it is determined in step S403 that a moving object cannot be detected and the process proceeds to step S407, the moving object detection flag is cleared here, and the moving object detection calculation subroutine is terminated.

  If it is determined in step S403 that a moving object has been detected and the process proceeds to step S404, a moving object detection flag is set here. Then, in the next step S405, it is determined whether or not the detected movement of the moving object is due to the front-rear direction with respect to the photographing surface. Terminates this moving object detection calculation subroutine. If it is moving only in the front-rear direction, the process proceeds from step S405 to step S406, the defocus flag is set, and this moving object detection calculation subroutine is terminated.

  By the above operation, if the detected motion of the moving object is only in the front-rear direction with respect to the imaging surface, the motion of the moving object is predicted by using the conventional prediction calculation based on the distance information obtained from the AF sensor 502. be able to.

  According to the second embodiment, the moving object is detected based on the image data from the image sensor 507 even during the mirror-up, which is during the continuous shooting and during the release when the defocus detection by the conventional phase difference detection cannot be performed. If the detected motion of the moving object is only in the front-rear direction with respect to the imaging surface, the moving object is predicted from the previous defocus amount. If the detected moving object moves not only in the front-rear direction with respect to the shooting surface but also in the vertical and horizontal directions with respect to the shooting surface, the moving object detection result is combined with the previous defocus detection result. By using these, the accuracy of moving object prediction can be further increased.

  The single-lens reflex camera which is an imaging device of each of the above embodiments includes the following components. The focus state is detected in a plurality of focus areas, and the focus detection unit (the phase difference detection unit 503 and the defocus amount becomes incapable of detecting the focus state during the release time for exposure of the image pickup unit (image pickup device 5)). A calculation unit 504). Furthermore, it has a prediction calculation means (step S010 in FIG. 3) for predicting the lens driving amount for the current focus adjustment from the past multiple times detected by the focus detection means and the current focus state. Furthermore, it has a control means (step S011 of FIG. 3) which drives a lens by the prediction calculation result of a prediction calculation means. Furthermore, it has a moving body detection means (FIG. 4) which detects a moving body from two or more images image | photographed at the time of continuous imaging | photography, and detects the position of the focus area in which a moving body is located. When the moving object is detected during the continuous shooting, the moving object detecting unit determines whether or not the focus area where the moving object is located is changed (steps S110 to S113 in FIG. 4). Further, when the change of the focus area is determined by the moving object detection unit, the control unit causes the prediction calculation unit to perform the calculation operation using the focus state of the changed focus area (step S008 in FIG. 3).

  The control means prohibits the prediction calculation and the lens driving of the prediction calculation means when the position of the focus area where the moving object is located is not detected even if the moving object is detected by the moving object detection means (step S114 in FIG. 4). 3 step S009 is ON → S012).

  When the moving body detection unit does not detect the moving body (NO in step S108 in FIG. 4), the control unit does not cause the prediction calculation unit to use the moving body detection information by the moving body detection unit (return immediately from step S108 in FIG. 4).

  The moving body detection means also detects the movement of the moving body in the front-rear direction on the optical axis (step S405 in FIG. 7). When the moving object detection means detects only the movement of the moving object in the front-rear direction (step S406 in FIG. 7), the control means does not cause the prediction calculation means to use the moving object detection information from the moving object detection means (step S309 in FIG. 6). YES → S315 → Return).

501 Camera control unit 502 AF sensor 503 Phase difference detection unit 504 Defocus amount calculation unit 505 Lens drive amount calculation unit 506 Moving object detection unit 507 Imaging element 513 Lens

Claims (4)

A first image sensor;
A second imaging device;
A first state in which light from the subject that has passed through the lens is guided to the second image sensor, and a second state in which light from the subject that has passed through the lens by being retracted is guided to the first image sensor. A mirror member having
Said focus detection means for detecting a focus state of a plurality of focus areas by using the output signal from the second image sensor, lenses driven from the result of the focus state of repeatedly detected more than once by the focus detection means as well as predict the amount, and control means for causing the lens driving by the prediction calculation result,
And detects the first body from two or more images obtained from the output signal from the imaging device, a moving object detection means for selecting a focus area that corresponds to the position of the middle et the body of the plurality of focus areas Have
The moving object detection unit, when the continuous shooting, in repeating the return from the retracted state and the retracted state of the mirror member, the control means, the focus state of the focus area selected by said moving object detecting means An imaging apparatus characterized by being used to drive a lens . Wherein when not detected the position of the focus area located moving object even when detecting movement by the moving object detecting means, to claim 1, characterized in that prohibiting the prediction calculation and the lens drive The imaging device described. Wherein, when the moving object detection means does not detect a moving object, the imaging apparatus according to claim 1 or 2 characterized in that it does not use the motion information detected by the moving object detection unit. 4. The imaging apparatus according to claim 1 , wherein the focus detection unit receives an object image reflected by the mirror member from an imaging state to an object observation state . 5.

Images