Focusing device, imaging device, focusing 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 device that performs focus control.

Background Art

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

[0003] Patent Document 1 discloses a method of restarting the driving of a focus lens by changing the time or number of times until restart of the driving of the focus lens based on the temporal change of the detected defocus amount, thereby enabling prompt focus control according to the moving speed for a subject approaching in the optical axis direction or a subject moving away in the infinite direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method disclosed in Patent Document 1, when another subject crosses in front of the subject (main subject), there is a possibility that the main subject is erroneously determined to have moved and the driving of the focus lens is 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, the present invention aims to provide a control device, an imaging device, a control method, and a program that enable rapid focus tracking of a subject moving along the optical axis and suppression of unnecessary focus tracking of a subject crossing the optical axis. [Means for solving the problem]

[0007] One aspect of the present invention is a focus adjustment device which includes a focus detection means that detects the amount of defocus using a signal obtained from an image sensor that captures an image of a subject formed by an imaging optical system including a focus lens, and the focus lens which detects the amount of defocus based on the amount of defocus detected by the focus detection means of Drive Control A focus adjustment means for adjusting the focus, and the focus detection means by Defocus amount exceeding a predetermined amount but detection At the time it was done From the focus lens of Drive Start A setting means for setting the drive waiting time until the action is performed, and a subject detection means for detecting the orientation of the subject's face using the signal obtained from the image sensor, A determination means for determining the movement of the subject in the forward and backward direction, The setting means is The forward and backward movement of the subject determined by the determination means, The drive waiting time is varied according to the orientation of the subject's face detected by the subject detection means.

[0008] Other objects and features of the present invention are described in the following embodiments. [Effects 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 enable rapid focus tracking of a subject moving along the optical axis and suppression of unnecessary focus tracking of a subject crossing the optical axis. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram of the camera system in this embodiment. [Figure 2] This is a pixel configuration diagram of the image sensor in this embodiment. [Figure 3] This is a flowchart showing the focus adjustment process in this embodiment. [Figure 4] This is a flowchart showing the focus detection process in this embodiment. [Figure 5] This is an explanatory diagram of the correlation change amount in this embodiment. [Figure 6] This is a flowchart showing the process for setting the lens drive waiting time in this embodiment. [Figure 7] This is a flowchart showing the lens driving process in this embodiment. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0012] First, with reference to Figure 1, the camera system (imaging system) 1 in this embodiment will be described. Figure 1 is a block diagram of the camera system 1. The camera system 1 is a lens-exchangeable camera system consisting of a camera body (imaging device) 20 and an interchangeable lens (lens device) 10 that can be attached to and detached 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 cameras in which the camera body and lens device are integrally configured.

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

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

[0015] The camera body 20 includes an imaging device 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 includes 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 imaging device 201 is composed of a CCD sensor or a CMOS sensor, and images (photoelectric conversion) a subject image (optical image) formed by the imaging optical system to output an analog electrical signal. The imaging device 201 is driven according to an imaging drive signal given from a timing generator 215 in accordance with a command from the camera control unit 212.

[0017] Next, referring to FIG. 2, the pixel configuration (pixel array) of the imaging device 201 will be described. FIG. 2 is a pixel configuration diagram of the imaging device 201 for performing focus detection by the imaging surface phase difference detection method. The imaging device 201 is configured such that each pixel includes one microlens and two photoelectric conversion units (photodiodes) in order to perform AF (imaging surface phase difference AF) by the imaging surface phase difference detection method. FIG. 2 shows the pixel array of the imaging device 201 and indicates a range of 6 pixel rows in the vertical (Y direction) and 8 pixel columns in the horizontal (X direction) of the CMOS image sensor as viewed from the imaging optical system side. A color filter in a Bayer array is provided in the imaging device 201, and color filters of green (G) and red (R) are alternately arranged in order from the left for the pixels in odd rows, and color filters of blue (B) and green (G) are alternately arranged in order from the left for the pixels in even rows. In pixel 211, the circle marked with reference numeral 211i indicates an on-chip microlens (microlens), and the two rectangles marked with reference numerals 211a and 211b arranged inside the microlens 211i respectively indicate photoelectric conversion units.

[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 A signals and B signals, which are two electrical signals, can be extracted. By synthesizing the A signals and B signals respectively taken out from each of the plurality of pixels, A image signals and B image signals (hereinafter, also collectively referred to as a pair of AF image signals), which are two (a pair) of image signals for focus detection in AF, can be obtained. Also, an imaging signal for generating an imaging image can be obtained by synthesizing the (A + B) signals obtained by adding the A signals and B signals respectively taken out from each of the plurality of pixels. Note that in each pixel, one of the A signal and the B signal may be subtracted from the (A + B) signal to obtain the other signal.

[0019] The pair of AF image signals and imaging signals read from the image sensor 201 are input to the CDS / AGC / AD converter 202, where correlated double sampling, gain adjustment, and digitization are performed to remove reset noise. The CDS / AGC / AD converter 202 outputs the pair of digital AF image signals to the AF signal processing unit 204 and the digital imaging signals to the 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 the image corresponding to the digital imaging signal on the display unit 206. If the 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] ROM 210 stores computer programs executed by the camera control unit 212, which acts as a computer, as well as data necessary for various controls. Flash ROM 220 stores various information related to the operation of the camera body 20, such as information set by the user.

[0022] The subject detection unit (subject detection means) 216 performs face detection processing on the digital imaging signal read from the image sensor 201 and detects information regarding the subject's face region.

[0023] The AF signal processing unit 204 performs a correlation calculation on the A image signal and B image signal, which are a pair of digital AF image signals, and calculates the phase difference (image shift amount) and reliability information (degree of two-image agreement, contrast information, saturation information, scratch information, etc.) between the A image signal and B image signal. 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 based on the acquired image shift amount and reliability information. For example, if the image shift amount is large, the camera control unit 212 sets a wider area for performing the correlation calculation, and also changes the type of bandpass filter according to the contrast information.

[0024] The camera control unit 212 controls each block within the camera body 20. The camera operation unit 214 controls the operation of the interchangeable lens 10 while communicating with the lens control unit 106. An AF control unit 213 is provided within the camera control unit 212. The AF control unit 213 performs AF control (focus control) using image shift amount and reliability information. The AF signal processing unit 204 and the AF control unit 213 constitute a focus detection means. The AF control unit 213 is also a focus adjustment means that drives the focus lens 103 to adjust the focus 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 Figure 3. Figure 3 is a flowchart showing the focus adjustment process in this embodiment. The flowchart in Figure 3 shows the control method executed by the camera control unit 212 (AF control unit 213), which acts as a control means and prediction means, according to a computer program.

[0026] First, in step S301 (face region detection step), the subject detection unit 216 detects information regarding the face region of the subject based on the imaging signal output from the image sensor 201. The information regarding the face region includes information indicating the position of the face in the field of view and information indicating the orientation of the face (facing forward, facing sideways, facing backward, etc.). Note that the term "face" is not necessarily limited to human faces and may include animal faces, etc.

[0027] Subsequently, in step S302 (defocus amount detection step), the camera control unit 212 performs focus detection processing. The details of the focus detection processing will be described later with reference to FIG. 4. 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. When 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 nearer side in the optical axis direction, for example, when z1>z2>z3>z4, it can be determined that the object is a moving object approaching in the approaching direction. Also, when z1<z2<z3<z4, it can be determined that the object is a moving object moving away in the infinite direction. Considering the detection error of focus detection, the time interval of the image plane positions to be compared may be spaced, for example, when z1>z3 and z2>z4, it may be determined that the subject is approaching in the approaching direction. 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 driving in progress flag indicating that the driving control of the focus lens 103 is being executed is on. If the lens driving in progress flag is on, the process proceeds to step S313. On the other hand, if the lens driving in progress flag is not on, the process proceeds to step S305.

[0031] In step S305, the camera control unit (setting means) 212 performs a process to set the lens drive waiting time, which is the waiting time from when a defocus amount (defocus amount greater than or equal to a predetermined amount) that should be driven by the lens is detected until the lens drive is actually executed. The lens drive waiting time is the waiting time until the lens drive for focus adjustment is started, and details of the process for setting the lens drive waiting time will be described later with reference to Figure 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 or not. 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 amount of defocus detected in step S302 is within a predetermined range. If the amount of defocus is within the predetermined range, the process proceeds to step S308. On the other hand, if the amount of defocus is not within the predetermined range, the process proceeds to step S309. It is preferable that the predetermined range be set to a range suitable for determining whether or not the camera is in focus, in order to avoid unnecessary lens movement in the focused state.

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

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

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

[0037] In this embodiment, after a predetermined amount of defocus (a predetermined amount of defocus) that requires lens drive is detected, the 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 it by time using a timer. For example, a counter that increases 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.

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

[0039] First, in step S401, the camera control unit 212 instructs the AF signal processing unit 204 to perform a correlation calculation on the pair of AF image signals acquired from the image sensor 201. The camera control unit 212 then calculates the 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 the minimum value. The camera control unit 212 also instructs the AF signal processing unit 204 to calculate the correlation amount of the pair of 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 correlation change amount of the paired AF image signals. Here, the correlation change amount of the paired AF image signals will be explained with reference to Figure 5. Figure 5 is an explanatory diagram of the correlation change amount when driving the focus lens 103 from a state where the degree of blur of the subject image is large to near the in-focus state in image plane phase-detection AF. In Figure 5, the horizontal axis shows the degree of blur, and the vertical axis shows the correlation change amount MAXDER. The correlation change amount MAXDER can be calculated using the following equation (1).

[0041] MAXDER(k)=(COR[k-3]-COR[k-1])-(COR[k-2]-COR[k]) … (1) In equation (1), k is an integer variable used to specify the position, and COR[k] is the correlation amount of the paired AF image signals at position k. In image plane phase-detection AF, the value of the correlation change amount increases as the degree of blur approaches the in-focus state.

[0042] Next, in step S403, the camera control unit 212 uses the correlation change amount MAXDER to calculate the standard deviation of the defocus amount Defocus3σ using the following equation (2).

[0043] Defocus 3σ = 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, referring to FIG. 6, the setting process (step S305) of the lens drive waiting time (waiting time until the lens drive is started) 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 the subject is moving or not based on the result of the motion detection in step S303 in Figure 3. If the subject is determined to be moving, the process proceeds to step S602. On the other hand, if the subject is not determined to be moving, the process proceeds to step S607.

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

[0049] In step S603, the camera control unit 212 determines whether the subject is a moving object approaching in the near direction, as determined in step S303, and whether the orientation of the subject's face, as detected in step S301 in Figure 3, is facing forward (towards the camera body 20). If the subject is a moving object approaching in the near direction and its face is facing forward, the process proceeds to step S605. On the other hand, if the subject is not a moving object approaching in the near direction, or its face is not facing forward, the process proceeds to step S604.

[0050] In step S604, the camera control unit 212 determines whether the subject is a moving object moving away in the infinite direction, as determined in step S303, and whether the subject's face, as detected in step S301, is facing backward (away from the camera body 20). If the subject is a moving object moving away in the infinite direction and its face is facing backward, the process proceeds to step S605. On the other hand, if the subject is not a moving object moving towards in the infinite direction, or its face is not facing backward, 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 in Figure 6, the lens drive waiting time is set to be the same for a moving object whose face is facing forward and approaching in the near direction, and for a moving object whose face is facing backward and moving away in the infinite direction. However, different waiting times may be set for each. Also, when the subject is moving, the waiting time may be changed according to the distance to the subject. For example, the waiting time may be shortened when the moving subject is close to the camera body 20, and lengthened when it is farther away from the camera body 20. This is because, even if the speed of movement 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 pronounced the blur becomes, requiring a quicker start of lens drive.

[0053] As described above, in the lens drive waiting time setting process shown in Figure 6, the camera control unit 212 sets the lens drive waiting time when a defocus amount requiring lens drive is detected, based on the determination result (motion detection result) by the determination means and information regarding the face region. If the subject is moving, it is set to a second time, which is shorter than the first time when the subject is not moving. This allows the lens drive to start quickly. Furthermore, if a face region is detected and the orientation of the face matches the direction of movement of the moving object, it is set to a third time, which is shorter than the second time. This allows the lens drive to start even more quickly, and in particular, enables rapid focus tracking for moving subjects that include the face region. On the other hand, if the orientation of the face does not match the direction of movement of the moving object, it is assumed that another subject may have crossed in front of the main subject, and the waiting time is kept at the second time, which suppresses the initiation of unnecessary lens drive in response to a crossing subject.

[0054] Next, with reference to Figure 7, the lens drive process (step S313) performed by the camera control unit 212 on the focus lens 103 will be described.

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

[0056] In step S702, the camera control unit 212 determines whether the subject is moving or not based on the motion detection result in step S303. If the subject is determined to be moving, the process proceeds to step S703. On the other hand, if the subject is not determined to be moving, 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, acting as a prediction means, calculates the image plane position where a focused image of the subject is formed from the defocus amount detected (calculated) in the focus detection process of step S302, and performs prediction processing (prediction calculation) using the calculated image plane position. In the prediction processing, a predicted image plane position is calculated, which is predicted to be the image plane position of the subject in the future (at a later time), based on the image plane positions of subjects detected multiple times in the past and the calculation time 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 the lens drive amount (first drive amount: hereinafter referred to as the first lens drive amount) as the drive amount of the focus lens 103.

[0059] Next, in step S705, the camera control unit 212 drives the focus lens 103 to align 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 calculates the drive speed of the focus lens 103 (lens drive speed) by dividing the first lens drive amount calculated in step S704 by the duration of time the focus lens 103 is driven.

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

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

[0062] In steps S708 and S709, the camera control unit 212 performs AF control (second control) for a stationary subject. First, in step S708, the camera control unit 212 calculates the image plane position of the subject from the amount of defocus detected in the focus detection process in step S302, and calculates the lens drive speed to align (bring closer) the lens image plane position to the calculated image plane position. If the camera continues to focus quickly and sensitively on a stationary subject, the rapid focusing will be recorded in the video, degrading the video quality. In particular, near the point of focus, overruns where the focus lens 103 is driven beyond the focus position are noticeable. For this reason, the lens drive speed is set to a slower speed to deliberately focus more slowly as the camera approaches the point of focus, thereby improving the video quality. Also, frequently moving and stopping the focus lens 103 degrades the video quality, so the lens drive speed is set to move the focus lens 103 continuously without stopping during video capture.

[0063] Next, in step S709, the camera control unit 212 drives the focus lens 103 to align the lens image plane position with the image plane position of a non-moving subject. For this purpose, 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 according to the received lens drive speed.

[0064] In step S710, the camera control unit 212 initializes the lens drive wait timer and then stops the lens drive wait timer. Subsequently, in step S711, the camera control unit 212 turns off the lens drive flag, which indicates that drive control of the focus lens 103 is in progress. Subsequently, in step S712, the camera control unit 212 determines that the subject is in focus and stops the drive of the focus lens 103.

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

[0066] In this way, the camera control unit 212 switches the focus tracking method between moving subjects and stationary subjects based on the motion detection result during the lens drive processing in steps S701 to S713. For moving subjects, it performs a quick focus control that prioritizes focus (first control), and for stationary subjects, it performs a focus control that prioritizes the quality of the video (second control). 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) includes 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 amount of defocus using a signal obtained from the image sensor 201 that captures a subject image formed by the imaging optical system. The subject detection means detects information about the face region of the subject using a signal obtained from the image sensor. The determination means determines whether or not the subject is moving based on the amount of defocus. The setting means sets the drive waiting time from when the focus detection means detects a defocus amount of a predetermined amount or more until the focus element of the imaging optical system is driven, based on the information about the face region of the subject and the determination result by the determination means.

[0068] Preferably, the control device includes a prediction means and a calculation means (camera control unit 212). The prediction means calculates information corresponding to the predicted image plane position, which is the future image plane position of the subject, and the amount of drive of the focusing element. Based on the amount of drive of the focusing element calculated by the prediction means, the calculation means calculates the drive speed of the focusing element such that the image plane position of the imaging optical system approaches the predicted image plane position. The storage means stores the detection times of multiple past defocus amounts by the focus detection means. Based on the multiple past defocus amounts and detection times stored in the storage means, the prediction means calculates information corresponding to the predicted image plane position and the amount of drive of the focusing element. If the subject is determined to be a moving object, the focus adjustment means performs a first control to drive the focusing 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 focusing element at a lower 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 supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

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

[0071] Although 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 its gist. [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 means for detecting the amount of defocus using a signal obtained from an image sensor that captures an image of a subject formed by an imaging optical system including a focus lens, A focus adjustment means that controls the drive of the focus lens to adjust the focus based on the amount of defocus detected by the focus detection means, A setting means for setting the drive waiting time from the point at which the focus detection means detects a defocus amount of a predetermined amount or more until the drive of the focus lens is started, A subject detection means that detects the orientation of the subject's face using the signal obtained from the image sensor, It has a determination means for determining the movement of the subject in the front-to-back direction, The setting means is a focus adjustment device characterized by varying the drive waiting time according to the forward and backward movement of the subject determined by the determination means and the orientation of the subject's face detected by the subject detection means.

2. The focus adjustment device according to claim 1, characterized in that the setting means sets the drive waiting time when the subject is a moving object approaching in the near direction and 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. The focus adjustment device according to claim 1, characterized in that the setting means sets the drive waiting time when the subject is a moving object approaching in the near direction, and the direction of the subject's face is facing forward, to be shorter than the drive waiting time when the subject is facing backward.

4. The focus adjustment device according to Claim 1, characterized in that the setting means sets the drive waiting time when the subject is not determined to be a moving object to be longer than the drive waiting time when the subject is a moving object approaching in the near direction and the subject is facing forward.

5. The focus adjustment device according to claim 1, characterized in that the setting means sets the drive waiting time when the subject is a moving object approaching in the near direction and the subject is facing forward to the same as the drive waiting time when the subject is a moving object moving away in the infinite direction and the subject is facing backward.

6. The focusing device according to any one of claims 1 to 5, characterized in that the information relating to the facial region of the subject is information relating to the facial region of a human or animal.

7. Image sensor and An imaging apparatus characterized by having a focus adjustment device according to any one of claims 1 to 6.

8. A focus detection step in which the amount of defocus is detected using a signal obtained from an image sensor that captures an image of a subject formed by an imaging optical system including a focus lens, A focus adjustment step that controls the drive of the focus lens to adjust the focus based on the amount of defocus detected in the focus detection step, A setting step to set the drive waiting time from the point in time when a defocus amount of a predetermined amount or more is detected by the focus detection step until the drive of the focus lens is started, A subject detection step in which the orientation of the subject's face is detected using the signal obtained from the image sensor, It includes a determination step for determining the movement of the subject in the forward and backward direction, The setting step is characterized by varying the drive waiting time according to the forward and backward movement of the subject determined in the determination step and the orientation of the subject's face detected in the subject detection step.

9. A program characterized by causing a computer to execute the focus adjustment method described in claim 8 and generating a signal for driving the focus lens.

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