Focus adjustment device, imaging apparatus, focus adjustment method, and program

Abstract

To provide a control device capable of quickly performing focus tracking on a subject moving along an optical axis direction and suppressing unnecessary focus tracking on a crossing subject.SOLUTION: A focus adjustment device includes: focus detection means that detects a defocus amount using signals obtained from an imaging element that captures a subject image formed by an imaging optical system including a focus lens; focus adjustment means that drives the focus lens on the basis of the defocus amount detected by the focus detection means to perform focus adjustment; setting means that sets a drive waiting time from the time when the focus detection means detects a defocus amount exceeding a prescribed amount to the time when the focus lens is driven; and subject detection means that detects an orientation of the face of a subject using signals obtained from the imaging element. The setting means varies the drive waiting time according to the orientation of the face of the subject detected by the subject detection means.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an imaging apparatus that performs focus control. [Background technology]

[0002] Some imaging devices, such as digital cameras, perform autofocus (AF) using an image plane phase difference detection method that uses an output signal from an imaging element for capturing an image of a subject. If the focus lens is driven frequently during video capture, the quality of the captured video will be impaired. Therefore, in general, the drive of the focus lens is stopped after focusing once, and the drive of the focus lens is restarted after a defocus amount greater than a predetermined value is detected for a certain period of time or more.

[0003] Patent Document 1 discloses a method for restarting the drive of the focus lens in accordance with the moving speed of the subject by changing the time or number of times until restart based on the change over time of the detected defocus amount. This makes it possible to perform quick focus control according to the moving speed of a subject approaching in the direction of the optical axis or a subject receding toward infinity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-156931 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the method disclosed in Patent Document 1, when another subject crosses in front of a subject (main subject), it may be erroneously determined that the main subject has moved, and the drive of the focus lens may be restarted. It is difficult to determine, based on the detected defocus amount, that the main subject has approached along the optical axis direction, or that another subject (crossing subject) has crossed in front of the main subject.

[0006] Therefore, an object of the present invention is to provide a control device, an imaging device, a control method, and a program that are capable of rapid focus tracking of a subject moving along the optical axis direction and suppressing unnecessary focus tracking of a crossing subject. [Means for solving the problem]

[0007] A focus adjustment device as one aspect of the present invention comprises focus detection means for detecting a defocus amount using a signal obtained from an image sensor that captures a subject image formed by an imaging optical system including a focus lens, focus adjustment means for driving the focus lens to perform focus adjustment based on the defocus amount detected by the focus detection means, setting means for setting a drive wait time from when the focus detection means detects a defocus amount equal to or greater than a predetermined amount until when the focus lens is driven, and subject detection means for detecting the direction of the subject's face using the signal obtained from the image sensor, and the setting means varies the drive wait time depending on the direction of the subject's face detected by the subject detection means.

[0008] Other objects and features of the present invention will be described in the following embodiments. Effect of the Invention

[0009] According to the present invention, it is possible to provide a control device, an imaging device, a control method, and a program that are capable of rapid focus tracking of a subject moving along the optical axis direction and suppressing unnecessary focus tracking of a crossing subject. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram of a camera system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a pixel configuration diagram of an image sensor according to the present embodiment. [Diagram 3] 5 is a flowchart showing a focus adjustment process in the present embodiment. [Figure 4] 5 is a flowchart showing focus detection processing in the present embodiment. [Diagram 5] FIG. 4 is an explanatory diagram of a correlation change amount in the present embodiment. [Figure 6] 6 is a flowchart showing a process for setting a lens drive waiting time in the present embodiment. [Figure 7] 5 is a flowchart showing a lens driving process in the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0012] First, a camera system (imaging system) 1 in this embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram of the camera system 1. The camera system 1 is a lens-interchangeable camera system that is configured with a camera body (imaging device) 20 and an interchangeable lens (lens device) 10 that is detachable from the camera body 20. The interchangeable lens 10 is detachably attached to the camera body 20 via its mount. However, the camera system of this embodiment is not limited to this, and can also be applied to a camera in which the camera body and the lens device are integrally configured.

[0013] The interchangeable lens 10 has an imaging optical system including a fixed lens 101, an aperture 102, and a focus lens (focus element) 103. The aperture 102 is driven by an aperture actuator included in an aperture drive unit 104, and adjusts the amount of light passing through the imaging optical system by increasing or decreasing its opening diameter. The focus lens 103 is driven in the optical axis direction by a focus actuator included in a focus drive unit 105 to perform focus adjustment.

[0014] The lens operation unit 107 includes various operation members operated by the user. The lens control unit 106 performs control and processing in response to user operations on the lens operation unit 107. The lens control unit 106 also controls the aperture driving unit 104 and the focus driving unit 105 in response to commands and information received from a camera control unit 212 (described later) via electrical contacts (not shown) provided on the mount unit. The lens control unit 106 also transmits information about the interchangeable lens 10 (lens information) to the camera control unit 212 via the electrical contacts.

[0015] The camera body 20 has an image sensor 201, a CDS / AGC / AD converter 202, an image input controller 203, an AF signal processing unit 204, a display control unit 205, and a display unit 206. The camera body 20 also has a recording medium control unit 207, a recording medium 208, an SDRAM 209, a ROM 210, a flash ROM 220, a camera control unit 212, and a camera operation unit 214.

[0016] The image sensor 201 is configured with a CCD sensor or a CMOS sensor, captures (photoelectrically converts) a subject image (optical image) formed by an imaging optical system, and outputs an analog electrical signal. The image sensor 201 is driven in response to an imaging drive signal provided from a timing generator 215 in accordance with a command from a camera control unit 212.

[0017] Next, the pixel configuration (pixel array) of the image sensor 201 will be described with reference to Fig. 2. Fig. 2 is a pixel configuration diagram of the image sensor 201 for performing focus detection by an image sensor phase difference detection method. The image sensor 201 is configured with one microlens and two photoelectric conversion units (photodiodes) for performing AF by the image sensor phase difference detection method (image sensor phase difference AF). Fig. 2 shows the pixel array of the image sensor 201, and shows a range of six pixel rows vertically (Y direction) and eight pixel columns horizontally (X direction) of the CMOS image sensor as seen from the imaging optical system side. The image sensor 201 is provided with color filters in a Bayer array, and green (G) and red (R) color filters are alternately arranged from the left in the odd-numbered rows of pixels, and blue (B) and green (G) color filters are alternately arranged from the left in the even-numbered rows of pixels. In the pixel 211, a circle labeled with reference numeral 211i indicates an on-chip microlens (microlens), and two rectangles labeled with reference numerals 211a and 211b arranged inside the microlens 211i each indicate a photoelectric conversion unit.

[0018] The light beam incident on each pixel is split into two by the microlens 211i, and these two light beams are photoelectrically converted by the two photoelectric conversion units 211a and 211b, so that two electrical signals, signal A and signal B, can be extracted. By combining the signal A and signal B extracted from each of the multiple pixels, two (pair) image signals, A image signal and B image signal (hereinafter, also referred to as a pair of AF image signals), are obtained as image signals for focus detection in AF. Also, by combining the signal (A+B) obtained by adding the signal A and the signal B extracted from each of the multiple pixels, an image signal for generating a captured image is obtained. Note that, in each pixel, one of the signal A and the signal B may be subtracted from the signal (A+B) to obtain the other signal.

[0019] The pair of AF image signals and imaging signals read out from the image sensor 201 are input to a CDS / AGC / AD converter 202, which performs correlated double sampling to remove reset noise, gain adjustment, and digital signal conversion. The CDS / AGC / AD converter 202 outputs the pair of digital AF image signals to an AF signal processor 204, and outputs a digital imaging signal to an image input controller 203.

[0020] The image input controller 203 stores the digital imaging signal in the SDRAM 209. The digital imaging signal stored in the SDRAM 209 is sent to the display control unit 205 via the bus 21. The display control unit 205 displays an image corresponding to the digital imaging signal on the display unit 206. When a mode for recording captured images is set, the digital imaging signal is recorded on the recording medium 208 by the recording medium control unit 207.

[0021] The ROM 210 stores computer programs executed by the camera control unit 212 as a computer, data necessary for various controls, etc. The flash ROM 220 stores various information related to the operation of the camera body 20, such as information set by the user.

[0022] A subject detection section (subject detection means) 216 performs face detection processing and the like on the digital imaging signal read out from the image sensor 201, and detects information relating to the face area of ​​the subject.

[0023] The AF signal processing unit 204 performs correlation calculations on the A and B image signals as a pair of digital AF image signals, and calculates the phase difference (image shift amount) between the A and B image signals and reliability information (degree of coincidence between two images, contrast information, saturation information, scratch information, etc.). The AF signal processing unit 204 outputs the calculated image shift amount and reliability information to the camera control unit 212. The camera control unit 212 notifies the AF signal processing unit 204 of changes to the settings for calculating these, depending on the acquired image shift amount and reliability information. For example, when the image shift amount is large, the camera control unit 212 sets a wide area for performing correlation calculations, and changes the type of band-pass filter depending on the contrast information.

[0024] The camera control unit 212 controls each block in the camera body 20. Furthermore, the camera operation unit 214 controls the operation of the interchangeable lens 10 while communicating with the lens control unit 106. The camera control unit 212 includes an AF control unit 213. The AF control unit 213 performs AF control (focus control) using the amount of image shift and reliability information. The AF signal processing unit 204 and the AF control unit 213 form a focus detection means. Furthermore, the AF control unit 213 is a focus adjustment means that drives the focus lens 103 to perform focus adjustment based on the amount of defocus detected by the focus detection means.

[0025] Next, the focus adjustment process (AF control process) in this embodiment will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the focus adjustment process in this embodiment. The flowchart in Fig. 3 shows a control method executed by the camera control unit 212 (AF control unit 213) as a control means and a prediction means in accordance with a computer program.

[0026] First, in step S301 (face area detection step), subject detection unit 216 detects information about the face area of ​​the subject based on the imaging signal output from imaging element 201. The information about the face area includes information indicating the position of the face on the angle of view and information indicating the orientation of the face (facing forward, facing sideways, facing backwards, etc.). Note that the face does not necessarily have to be limited to a human face, and may include an animal's face, etc.

[0027] Subsequently, in step S302 (defocus amount detection step), the camera control unit 212 performs focus detection processing. For details of the focus detection processing, see FIG. 4 which will be described later. The defocus amount detected by the focus detection processing, the image plane position of the subject obtained from the current position of the focus lens 103, and the detection time of the defocus amount are stored in the SDRAM (storage means) 209 over a plurality of past times.

[0028] Subsequently, in step S303, the camera control unit (determination means) 212 determines whether the subject is a subject (moving object) that moves in the optical axis direction based on the image plane positions of the subject over a plurality of past times. If the subject is a moving object, the camera control unit 212 further determines whether the moving object approaches the camera body 20 in the approaching direction or moves away in the infinite direction.

[0029] Here, an example of a method for determining whether the subject is a moving object will be described. Let the image plane positions of the subject over a plurality of past times be z1, z2, z3, z4 in order from the oldest detection time. Assuming that the smaller the value indicating the image plane position, the closer the focus position is to the nearest side in the optical axis direction, for example, when z1>z2>z3>z4, it can be determined that the subject is a moving object approaching in the approaching direction. Also, when z1<z2<z3<z4, it can be determined that the subject is a moving object moving away in the infinite direction. Considering the detection error of focus detection, the time interval between the image plane positions to be compared may be set, for example, when z1>z3 and z2>z4, it may be determined that the subject is approaching. However, the method of determining a moving object is not limited to these.

[0030] Subsequently, in step S304, the camera control unit 212 determines whether the lens drive in progress flag indicating that the drive control of the focus lens 103 is being executed is on. If the lens drive in progress flag is on, the process proceeds to step S313. On the other hand, if the lens drive in progress flag is not on, the process proceeds to step S305.

[0031] In step S305, the camera control unit (setting means) 212 executes a process of setting a lens drive waiting time, which is a waiting time from when a defocus amount (a defocus amount equal to or greater than a predetermined amount) to which the lens should be driven is detected until when the lens is actually driven. Note that the lens drive waiting time is a waiting time until when the lens drive for focus adjustment starts, and the details of the lens drive waiting time setting process will be described later with reference to FIG. 6.

[0032] Next, in step S306, the camera control unit 212 determines whether the reliability of the focus detection result calculated in the focus detection process in step S302 is good. If the reliability is good, the process proceeds to step S307. On the other hand, if the reliability is not good, the process proceeds to step S309 to perform a search operation.

[0033] In step S307, the camera control unit 212 determines whether the defocus amount detected in step S302 is within a predetermined range. If the defocus amount is within the predetermined range, the process proceeds to step S308. On the other hand, if the defocus amount is not within the predetermined range, the process proceeds to step S309. Note that the predetermined range is preferably set to a range suitable for determining whether or not the camera is in focus, in order to avoid unnecessary lens driving in the in-focus state.

[0034] In step S308, the camera control unit 212 initializes the lens drive waiting timer and stops the lens drive waiting timer. In step S309, the camera control unit 212 determines whether the lens drive waiting timer has started. If the lens drive waiting timer has started, the process proceeds to step S311. On the other hand, if the lens drive waiting timer has not started, the process proceeds to step S310.

[0035] In step S310, the camera control unit 212 starts counting the lens drive waiting timer. In step S311, the camera control unit 212 determines whether the lens drive waiting timer has exceeded the lens drive waiting time set in the lens drive waiting time setting process in step S305. If the lens drive waiting timer has exceeded the lens drive waiting time, the process proceeds to step S312. On the other hand, if the lens drive waiting time has not exceeded, the process returns to step S301 and starts again from subject detection.

[0036] In step S312, the camera control unit 212 turns on the lens driving flag. Then, in step S313, the camera control unit 212 executes lens driving processing. Details of the lens driving processing will be described later with reference to FIG. 7. Then, in step S314, the camera control unit 212 determines whether or not to end the focus adjustment processing. If the focus adjustment processing is not to be ended, the process returns to step S301. On the other hand, if the focus adjustment processing is to be ended, this flow ends.

[0037] In this embodiment, after a defocus amount (a defocus amount equal to or greater than a predetermined amount) that should drive the lens is detected, a lens drive timer is started, and the lens drive process is performed when the lens drive timer exceeds a predetermined lens drive waiting time. However, it is not necessary to control the time using a timer. For example, a counter that increments by 1 each time focus detection is performed may be used, and the lens drive process may be performed when the lens drive counter exceeds a predetermined lens drive waiting count number.

[0038] Next, the focus detection process (step S302) executed by the camera control unit 212 will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the focus detection process.

[0039] First, in step S401, the camera control unit 212 causes the AF signal processing unit 204 to perform correlation calculation on paired AF image signals acquired from the image sensor 201. Then, the camera control unit 212 calculates a defocus amount from the shift amount Shift, which is the image shift amount at which the correlation amount received from the AF signal processing unit 204 becomes a minimum value. The camera control unit 212 also causes the AF signal processing unit 204 to calculate the correlation amount of the paired AF image signals for each shift amount Shift. Furthermore, the camera control unit 212 generates a waveform of the correlation amount for each shift amount Shift received from the AF signal processing unit 204.

[0040] Next, in step S402, the camera control unit 212 calculates the amount of correlation change between the paired AF image signals. Here, the amount of correlation change between the paired AF image signals will be described with reference to FIG. 5. FIG. 5 is an explanatory diagram of the amount of correlation change when the focus lens 103 is driven from a state in which the subject image is largely blurred to a state close to the in-focus state in image plane phase difference AF. In FIG. 5, the horizontal axis indicates the degree of blur, and the vertical axis indicates the amount of correlation change MAXDER. The amount of correlation change MAXDER can be calculated using the following formula (1).

[0041] MAXDER(k)=(COR[k-3]-COR[k-1])-(COR[k-2]-COR[k]) … (1) In equation (1), k is an integer variable that specifies the position, and COR[k] is the amount of correlation between the pair of AF image signals at position k. In image-plane phase-difference AF, the value of the amount of correlation change increases as the image moves from a state with a high degree of blur to a focused state.

[0042] Subsequently, in step S403, the camera control unit 212 calculates the standard deviation Defocus3σ of the defocus amount by using the correlation change amount MAXDER according to the following formula (2).

[0043] Defocus3σ=K×(A×MAXDER B ) … (2) In Equation (2), K is a conversion coefficient for converting the amount of image shift into the amount of defocus, and A and B are conversion coefficients for converting the amount of correlation change MAXDER into the standard deviation of the amount of image shift. The camera control unit 212 calculates the standard deviation Defocus3σ of the three types of defocus amounts by substituting the amount of correlation change MAXDER calculated in step S402 into Equation (2).

[0044] Subsequently, in step S404, the camera control unit 212 calculates a reliability evaluation value Rel representing the reliability of the defocus amount. For this purpose, the camera control unit 212 calculates Def3σTH3, Def3σTH2, and Def3σTH1 as thresholds for the standard deviation Defocus3σ of the defocus amount.

[0045] Subsequently, in step S405, the camera control unit 212 calculates the reliability evaluation value Rel using the calculated thresholds and ends the focus detection process. The reliability evaluation value Rel is represented in four levels of reliability evaluation value Rel3, reliability evaluation value Rel2, reliability evaluation value Rel1, and reliability evaluation value Rel0 in descending order of reliability, and is defined by the following Equation (3).

[0046] Rel = Rel3: when Defocus3σ ≤ Def3σTH3 Rel2: when Def3σTH3 < Defocus3σ ≤ Def3σTH2 Rel1: when Def3σTH2 < Defocus3σ ≤ Def3σTH1 Rel0: when Def3σTH1 ≤ Defocus3σ … (3) Next, with reference to FIG. 6, the setting process (step S305) of the lens drive waiting time (waiting time until the lens drive starts) executed by the camera control unit 212 will be described. FIG. 6 is a flowchart showing the setting process of the lens drive waiting time.

[0047] First, in step S601, the camera control unit 212 determines whether or not the subject is a moving object based on the result of the moving object determination in step S303 in Fig. 3. If the subject is determined to be a moving object, the process proceeds to step S602. On the other hand, if the subject is not determined to be a moving object, the process proceeds to step S607.

[0048] In step S602, the camera control unit 212 determines whether or not the subject's face area has been detected in the focus detection area by the subject detection unit 216 in step S301. If the subject's face area has been detected, the process proceeds to step S603. On the other hand, if the subject's face area has not been detected, the process proceeds to step S606.

[0049] In step S603, camera control unit 212 determines whether the subject is determined to be a moving object approaching in the close range in step S303 and the face of the subject detected in step S301 of Fig. 3 faces forward (toward camera body 20). If the subject is a moving object approaching in the close range and the face faces forward, the process proceeds to step S605. On the other hand, if the subject is not a moving object approaching in the close range or the face does not face forward, the process proceeds to step S604.

[0050] In step S604, camera control unit 212 determines whether the subject is determined in step S303 to be a moving object moving away toward infinity and the face of the subject detected in step S301 is facing backwards (away from camera body 20). If the subject is a moving object moving away toward infinity and the face is facing backwards, the process proceeds to step S605. On the other hand, if the subject is not a moving object approaching infinity or the face is not facing backwards, the process proceeds to step S606.

[0051] In step S605, the camera control unit 212 sets the lens drive waiting time to a third time. In step S606, the camera control unit 212 sets the lens drive waiting time to a second time that is longer than the third time. In step S607, the camera control unit 212 sets the lens drive waiting time to a first time that is longer than the second time.

[0052] In the flowchart of Fig. 6, the lens drive waiting time is the same for a moving object approaching in the close range with a face facing forward and a moving object moving away in the infinity direction with a face facing backward, but different waiting times may be set for each. Also, when the subject is a moving object, the waiting time may be changed according to the subject distance. For example, the waiting time may be shortened when the moving subject is close to the camera body 20, and the waiting time may be lengthened when the moving subject is far from the camera body 20. This is because, even if the moving speed of the subject is the same, the closer the subject is to the camera body 20, the greater the change in the image plane position and the more noticeable the blurring becomes, and the more rapid the start of lens drive is required.

[0053] In this way, the camera control unit 212 sets the lens drive waiting time when the defocus amount to drive the lens is detected based on the judgment result (moving object judgment result) by the judgment means and the information about the face area in the lens drive waiting time setting process of FIG. 6. When the subject is a moving object, the second time is set to be shorter than the first time when the subject is not moving. This allows the lens drive to be started promptly. Also, when the face area is detected and the face direction matches the moving direction of the moving object, the third time is set to be shorter than the second time. This allows the lens drive to be started more promptly, and in particular, it is possible to perform focus tracking promptly on a moving subject including a face area. On the other hand, when the face direction does not match the moving direction of the moving object, it is considered that another subject may have crossed in front of the main subject, and the second time is set, thereby making it possible to suppress the start of unnecessary lens drive in response to the crossing subject.

[0054] Next, the lens driving process (step S313) for the focus lens 103 executed by the camera control unit 212 will be described with reference to FIG.

[0055] First, in step S701, the camera control unit 212 determines whether or not the reliability of the focus detection result calculated in the focus detection process in step S302 in Fig. 3 is good. If it is determined that the reliability of the focus detection result is good, the process proceeds to step S702. On the other hand, if it is not determined that the reliability is good, the process proceeds to step S710.

[0056] In step S702, the camera control unit 212 determines whether or not the subject is a moving object based on the moving object determination result in step S303. If the subject is determined to be a moving object, the process proceeds to step S703. On the other hand, if the subject is not determined to be a moving object, the process proceeds to step S706.

[0057] In steps S703 to S706, the camera control unit 212 performs AF control (first control) for a moving subject. First, in step S703, the camera control unit 212 as a prediction means calculates an image plane position where a focused subject image is formed from the defocus amount detected (calculated) in the focus detection process in step S302, and performs a prediction process (prediction calculation) using the calculated image plane position. In the prediction process, a predicted image plane position is calculated that is predicted as the image plane position of the subject in the future (at a future time) from the image plane positions of the subject detected multiple times in the past and the calculation times of the defocus amount at that time.

[0058] Next, in step S704, the camera control unit 212 calculates the difference between the predicted image plane position calculated in step S703 and the current image plane position of the imaging optical system (hereinafter referred to as the lens image plane position). Then, the camera control unit 212 uses this difference to calculate a lens driving amount (first driving amount: hereinafter referred to as the first lens driving amount) as the driving amount of the focus lens 103.

[0059] Next, in step S705, the camera control unit 212 drives the focus lens 103 to match the lens image plane position with the predicted subject image plane position, in other words, to bring it closer. To this end, the camera control unit 212 divides the first lens driving amount calculated in step S704 by the time length for driving the focus lens 103 to calculate the driving speed (lens driving speed) of the focus lens 103.

[0060] Next, in step S706, the camera control unit 212 transmits the first lens driving amount calculated in step S704 and the lens driving speed calculated in step S705 to the lens control unit 106. The lens control unit 106 drives the focus lens 103 via the focus driving unit 105 in accordance with the received lens driving amount and lens driving speed.

[0061] In step S707, the camera control unit 212 determines whether or not the defocus amount detected in step S302 is within a predetermined range. If the defocus amount is within the predetermined range, it is assumed that the camera is in focus again, and the process proceeds to step S710. On the other hand, if the defocus amount is not within the predetermined range, the process proceeds to step S708. As in step S307, the predetermined range is preferably set to a range suitable for determining whether or not the camera is in focus in order to avoid unnecessary lens driving.

[0062] In steps S708 and S709, the camera control unit 212 performs AF control (second control) for a non-moving subject. First, in step S708, the camera control unit 212 calculates the image plane position of the subject from the defocus amount detected in the focus detection process in step S302, and calculates the lens drive speed for adjusting (approaching) the lens image plane position to the calculated image plane position. If the camera continues to sensitively and quickly adjust the focus on a non-moving subject, the state of small focus adjustments will be recorded in the video, and the quality of the video will be impaired. In particular, near the in-focus state, overrun in which the focus lens 103 is driven beyond the in-focus position is noticeable. For this reason, the closer to the in-focus state, the lower the lens drive speed is set to adjust the focus slowly, improving the quality of the video. In addition, frequently moving and stopping the focus lens 103 also deteriorates the quality of the video, so the lens drive speed is set so that the focus lens 103 is moved continuously without stopping during video capture.

[0063] Next, in step S709, the camera control unit 212 drives the focus lens 103 so as to align the lens image plane position with the subject image plane position of the non-moving subject. To this end, the camera control unit 212 transmits a focus command including the lens drive speed calculated in step S416 to the lens control unit 106. The lens control unit 106 drives the focus lens 103 via the focus drive unit 105 in accordance with the received lens drive speed.

[0064] In step S710, the camera control unit 212 initializes a lens drive waiting timer and stops the lens drive waiting timer. Then, in step S711, the camera control unit 212 turns off a lens drive flag indicating that drive control of the focus lens 103 is being executed. Then, in step S712, the camera control unit 212 determines that the subject is in focus and stops driving the focus lens 103.

[0065] In step S713, the camera control unit 212 transmits to the lens control unit 106 a command to drive the focus lens 103 at a preset search lens driving speed in order to search for a subject.

[0066] In this way, camera control unit 212 switches the focus tracking method between moving and non-moving subjects based on the moving subject determination result in the lens driving process of steps S701 to S713. For moving subjects, quick focus control with emphasis on focus (first control) is performed, and for non-moving subjects, focus control with emphasis on video quality (second control) is performed. This makes it possible to select the optimal focus control according to the subject.

[0067] As described above, in this embodiment, the control device (camera body 20) has focus detection means (AF signal processing unit 204, AF control unit 213), subject detection means (subject detection unit 216), determination means (camera control unit 212), and setting means (camera control unit 212). The focus detection means detects the defocus amount using a signal obtained from the image sensor 201 that captures the subject image formed by the imaging optical system. The subject detection means detects information about the face area of ​​the subject using the signal obtained from the image sensor. The determination means determines whether the subject is a moving object based on the defocus amount. The setting means sets a drive waiting time from when the focus detection means detects a defocus amount of a predetermined amount or more until when the focus element of the imaging optical system is driven, based on the information about the face area of ​​the subject and the determination result by the determination means.

[0068] Preferably, the control device has a prediction means and a calculation means (camera control unit 212). The prediction means calculates information corresponding to a predicted image plane position, which is a future image plane position of the subject, and a drive amount of the focus element. The calculation means calculates a drive speed of the focus element such that the image plane position of the imaging optical system approaches the predicted image plane position based on the drive amount of the focus element calculated by the prediction means. The storage means stores the detection times of the past defocus amounts by the focus detection means. The prediction means calculates information corresponding to the predicted image plane position and the drive amount of the focus element based on the past defocus amounts and detection times stored in the storage means. If the subject is determined to be a moving object, the focus adjustment means performs a first control to drive the focus element based on the drive speed calculated by the calculation means. If the subject is not determined to be a moving object, the focus adjustment means performs a second control to drive the focus element so that the focus element is driven at a slower speed than the first control, using the defocus amount detected by the focus detection means.

[0069] (Other embodiments) The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0070] According to this embodiment, it is possible to provide a control device, an imaging device, a control method, and a program that are capable of rapid focus tracking of a subject moving along the optical axis direction and suppressing unnecessary focus tracking of a crossing subject.

[0071] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0072] 20 Camera body (control device) 204 AF signal processing unit (focus detection means) 212 Camera control unit (determination means, setting means) 213 AF control unit (focus detection means) 216 Subject detection unit (subject detection means)

Claims

1. a focus detection unit that detects a defocus amount using a signal obtained from an image pickup element that captures an object image formed by an image pickup optical system including a focus lens; a focus adjustment unit that performs focus adjustment by driving the focus lens based on the defocus amount detected by the focus detection unit; a setting means for setting a drive waiting time from when the focus detection means detects a defocus amount equal to or greater than a predetermined amount until when the focus lens is driven; a subject detection means for detecting a facial orientation of a subject using a signal obtained from the imaging element, The focus adjustment device according to claim 1, wherein the setting means changes the drive wait time depending on the orientation of the face of the subject detected by the subject detection means.

2. 2. The focus adjustment device according to claim 1, wherein the setting means sets the drive waiting time when the subject's face is facing forward to be shorter than the drive waiting time when the subject's face is not facing forward.

3. 2. The focus adjustment device according to claim 1, wherein the setting means sets the drive waiting time when the subject's face faces forward to be shorter than the drive waiting time when the subject faces backward.

4. The apparatus further includes a determination means for determining the motion of a subject, 2. The focus adjustment device according to claim 1, wherein the setting means sets the drive waiting time when the subject is not determined to be a moving object to be shorter than the drive waiting time when the subject is a moving object approaching in a close direction and facing forward.

5. 5. The focus adjustment device according to claim 4, wherein the setting means sets a drive waiting time when the subject is a moving object approaching in a close range and facing forward, to be shorter than a drive waiting time when the subject is a moving object receding in an infinity range and facing backward.

6. 6. The focus adjustment device according to claim 1, wherein the information regarding the face region of the subject is information regarding the face region of a human or an animal.

7. An imaging element; An imaging device comprising: a focus adjustment device according to claim 1 .

8. a focus detection step of detecting a defocus amount using a signal obtained from an image sensor that captures an object image formed by an image pickup optical system including a focus lens; a focus adjustment step of driving the focus lens to perform focus adjustment based on the defocus amount detected in the focus detection step; a setting step of setting a drive waiting time from when a defocus amount equal to or greater than a predetermined amount is detected in the focus detection step until when the focus lens is driven; a subject detection step of detecting a facial orientation of a subject using a signal obtained from the image sensor, A focus adjustment method, wherein in the setting step, a drive wait time is varied depending on a face orientation of the subject detected in the subject detection step.

9. A program for causing a computer to execute the focus adjustment method according to claim 8.

Images