JP2018028654A - Control device, image capturing device, control method, program, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device capable of stably providing fast and accurate focus adjustment.SOLUTION: A control device (204, 212) comprises computation means (204) configured to compute a defocus amount based on first and second signals corresponding to rays passing through different pupil regions of an image capturing optical system (101, 102, 103), and focus adjustment means (212) for performing focus adjustment based on the defocus amount, the focus adjustment means being configured to change detection properties of the first and second signal for the computation means in accordance with a type of focus adjustment operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus that performs focus detection.

  In recent years, as phase difference AF (imaging surface phase difference AF) using an image sensor, a method of acquiring a photographed image and performing focus detection using pixels of the image sensor has been proposed. According to the imaging plane phase difference AF, subject detection and focus adjustment can be performed based on signals obtained from the same imaging device, so that high-speed and high-precision focus adjustment is possible.

  Patent Document 1 discloses a configuration in which a plurality of photodiodes corresponding to one microlens are provided, and each photodiode receives light from different pupil planes of the photographing lens. With such a configuration, the imaging surface phase difference AF can be performed by comparing the outputs of the two photodiodes.

  Patent Document 2 discloses a configuration in which a pupil division function is provided by decentering the sensitivity region of the light receiving unit with respect to the optical axis of the on-chip microlens in some pixels of the image sensor. The imaging plane phase difference AF can be performed by using these pixels as focus detection pixels and disposing the focus detection pixels at a predetermined interval between the imaging pixel groups. Here, since the location where the focus detection pixels are arranged corresponds to a missing portion of the shooting pixels, image information is generated by interpolation from information on surrounding shooting pixels. With such a configuration, phase difference detection can be performed on the imaging surface, so that high-speed and high-precision focus adjustment can be performed even during electronic viewfinder observation and moving image shooting.

JP 2001-083407 A JP 2009-003122 A

  However, in practice, the detection characteristics vary greatly depending on the evaluation band of the signal waveform used for the correlation calculation. In particular, in the case of the imaging plane phase difference AF, since it is necessary to perform correlation calculation in synchronization with the imaging signal, the correlation calculation time allowed for one image is limited. For this reason, the detection range is widened using a signal to which a low-pass filter is applied in the direction detection operation at the time of large blur, while the signal to which the high-pass filter is applied in the focusing operation near the focus It is necessary to increase the detection accuracy using. In other words, detection characteristics suitable for stably performing high-speed and high-precision focus adjustment differ depending on the state of the focus adjustment operation.

  Therefore, the present invention provides a control device, an imaging device, a control method, a program, and a storage medium capable of stably performing high-speed and high-precision focus adjustment.

  The control device according to one aspect of the present invention includes a calculation unit that calculates a defocus amount based on a first signal and a second signal corresponding to light beams that have passed through different pupil regions of the imaging optical system, and the defocus amount And a focus adjustment unit that performs a focus adjustment operation based on the focus adjustment unit, wherein the focus adjustment unit changes detection characteristics of the first signal and the second signal by the calculation unit according to a type of the focus adjustment operation. To do.

  An imaging apparatus according to another aspect of the present invention includes an imaging device having a first photoelectric conversion unit and a second photoelectric conversion unit that receive light beams passing through different pupil regions of an imaging optical system, and the first photoelectric conversion unit. And calculation means for calculating a defocus amount based on the first signal and the second signal corresponding to each of the output signals from the second photoelectric conversion unit, and focus adjustment for performing a focus adjustment operation based on the defocus amount And the focus adjustment means changes the detection characteristics of the first signal and the second signal by the calculation means according to the type of the focus adjustment operation.

  According to another aspect of the present invention, there is provided a control method comprising: calculating a defocus amount based on a first signal and a second signal corresponding to light beams that have passed through different pupil regions of an imaging optical system; and the defocus amount And a step of performing a focus adjustment operation based on the step, and in the step of performing the focus adjustment operation, the detection characteristics of the first signal and the second signal are changed according to the type of the focus adjustment operation.

  A program according to another aspect of the present invention causes a computer to execute the control method.

  A storage medium according to another aspect of the present invention stores the program.

  Other objects and features of the invention are described in the following embodiments.

  According to the present invention, it is possible to provide a control device, an imaging device, a control method, a program, and a storage medium capable of stably performing high-speed and high-precision focus adjustment.

It is a block diagram of the imaging device in each embodiment. FIG. 6 is a relationship diagram between detection accuracy and detection defocus amount for each band of an AF signal. It is a figure which shows the pixel structural example of (a) non-imaging surface phase difference system and (b) imaging surface phase difference system. It is a flowchart which shows the focus adjustment operation | movement in each of 1st and 2nd embodiment. It is explanatory drawing regarding the detection characteristic setting in each embodiment. It is a flowchart which shows the focus detection process in each embodiment. It is explanatory drawing of the focus detection area | region in each embodiment. It is explanatory drawing of the signal for AF (a pair of image signal) in each embodiment. It is explanatory drawing of the relationship between the shift amount of AF signal and correlation amount in each embodiment. It is explanatory drawing of the relationship between the shift amount of AF signal and correlation change amount in each embodiment. It is a flowchart which shows the setting of the detection characteristic in 2nd Embodiment. It is a flowchart which shows the focus adjustment operation | movement in 3rd Embodiment. It is explanatory drawing of the relationship between the reliability and detected defocus amount in 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, the configuration of the imaging apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of an imaging device 100 (lens-interchangeable camera system) in the present embodiment. The imaging apparatus 100 includes a camera body 20 (imaging apparatus body) and a lens unit 10 (interchangeable lens) that can be attached to and detached from the camera body 20. A lens control unit 106 that controls the overall operation of the lens unit 10 and a camera control unit 212 that controls the overall operation of the imaging apparatus 100 (camera system) including the lens unit 10 are terminals provided on the lens mount. It is possible to communicate with each other via (not shown). Note that this embodiment can also be applied to an imaging apparatus in which a lens unit and a camera body are integrally configured.

  First, the configuration of the lens unit 10 will be described. The fixed lens 101, the diaphragm 102, and the focus lens 103 constitute an imaging optical system. The diaphragm 102 is driven by the diaphragm driving unit 104 and controls the amount of light incident on the image sensor 201 described later. The focus lens 103 is driven by the focus lens driving unit 105, and the focusing distance of the imaging optical system changes according to the position of the focus lens 103. The aperture driving unit 104 and the focus lens driving unit 105 are controlled by the lens control unit 106 and determine the aperture amount of the aperture 102 and the position of the focus lens 103, respectively.

  The lens operation unit 107 is an input for the user to make settings related to the operation of the lens unit 10, such as switching between AF (autofocus) / MF (manual focus) modes, adjusting the position of the focus lens 103 using MF, and setting the camera shake correction mode. It is a group of devices. When the lens operation unit 107 is operated by the user, the lens control unit 106 performs control according to the operation. The lens control unit 106 controls the aperture driving unit 104 and the focus lens driving unit 105 according to a control command and control information received from a camera control unit 212 described later. The lens control unit 106 transmits lens control information to the camera control unit 212.

  Next, the configuration of the camera body 20 will be described. The camera body 20 is configured to acquire an imaging signal from a light beam that has passed through the imaging optical system of the lens unit 10. The imaging element 201 includes a CCD sensor, a CMOS sensor, and the like, and photoelectrically converts a subject image (optical image) formed via the imaging optical system of the lens unit 10 and outputs a pixel signal (image data). That is, the light beam incident from the image pickup optical system forms an image on the light receiving surface of the image pickup device 201 and is converted into a signal charge corresponding to the amount of incident light by the pixels (photodiodes) arranged in the image pickup device 201. The signal charge accumulated in each photodiode is sequentially read out from the image sensor 201 as a voltage signal corresponding to the signal charge based on the drive pulse output from the timing generator 214 in accordance with a command from the camera control unit 212.

  Each pixel of the image sensor 201 used in the present embodiment is provided for two (a pair) of photodiodes A and B and the pair of photodiodes A and B (sharing the photodiodes A and B). And a single microlens. That is, the image sensor 201 has a pair of photodiodes (first photoelectric conversion unit and second photoelectric conversion unit) for one microlens, and a plurality of microlenses are arranged in a two-dimensional manner. Each pixel divides incident light by a microlens to form a pair of optical images on the pair of photodiodes A and B, and the pair of photodiodes A and B uses a pair of AF signals that will be described later. Pixel signals (A image signal and B image signal) are output. Further, by adding the outputs of the pair of photodiodes A and B, an imaging signal (A + B image signal) can be obtained.

  An AF signal (focus detection) used for AF (imaging surface phase difference AF) by an imaging surface phase difference detection method by combining a plurality of A image signals and a plurality of B image signals output from a plurality of pixels, respectively. A pair of image signals as a signal for use) is obtained. An AF signal processing unit 204, which will be described later, performs a correlation operation on the pair of image signals to calculate a phase difference (image shift amount) that is a shift amount of the pair of image signals. The focus amount (and defocus direction) is calculated.

  Thus, the image sensor 201 photoelectrically converts an optical image formed by receiving the light beam that has passed through the imaging optical system of the lens unit 10 into an electrical signal, and outputs image data (image signal). The imaging element 201 of the present embodiment is provided with two photodiodes for one microlens, and can generate an image signal used for focus detection by the imaging plane phase difference AF method. Note that the number of photodiodes (divided PDs) sharing one microlens may be changed, such as providing four photodiodes for one microlens.

  3A schematically illustrates a configuration of a pixel that does not support the imaging surface phase difference AF method, and FIG. 3B schematically illustrates a configuration example of a pixel that supports the imaging surface phase difference AF method. 3A and 3B, a Bayer array is used, where R is a red color filter, B is a blue color filter, and Gr and Gb are green color filters. Show. In the pixel configuration of FIG. 3B corresponding to the imaging plane phase difference AF, one pixel (pixel indicated by a solid line) in the pixel configuration not corresponding to the imaging plane phase difference AF method shown in FIG. 2B, two photodiodes A and B divided into two in the horizontal direction are provided. Photodiodes A and B (first photoelectric conversion unit and second photoelectric conversion unit) receive light beams that have passed through different pupil regions of the imaging optical system. Since the photodiode A and the photodiode B receive light beams that have passed through different areas of the exit pupil of the photographing optical system, the B image signal has a parallax with respect to the A image signal. Note that the pixel dividing method shown in FIG. 3B is an example, and a configuration in which the pixel is divided in the vertical direction in FIG. 3B, a configuration in which the pixel is divided into two in the horizontal direction and the vertical direction (total of 4 divisions), and the like. Other configurations may be adopted. In addition, a plurality of types of pixels that are divided by different division methods in the same image sensor may be included.

  In the present embodiment, a configuration in which a plurality of photoelectric conversion units are arranged for one microlens and a pupil-divided light beam is incident on each photoelectric conversion unit is shown, but the present invention is limited to this. It is not a thing. For example, the configuration of the focus detection pixel may be a configuration in which one PD is provided under the microlens and the pupil division is performed by shielding the left and right or upper and lower sides with a light shielding layer. Further, a configuration may be employed in which a pair of focus detection pixels are discretely arranged in an array of a plurality of imaging pixels, and a pair of image signals are acquired from the pair of focus detection pixels.

  The CDS / AGC / AD converter 202 performs correlated double sampling, gain adjustment, and AD conversion for removing reset noise on the AF signal and the imaging signal read from the imaging element 201. The CDS / AGC / AD converter 202 outputs the imaging signal and the AF signal, which have been subjected to these processes, to the image input controller 203 and the AF signal processing unit 204, respectively.

  The image input controller 203 stores the imaging signal output from the CDS / AGC / AD converter 202 as an image signal in the SDRAM 209 via the bus 21. The image signal stored in the SDRAM 209 is read by the display control unit 205 via the bus 21 and displayed on the display unit 206. In the recording mode in which the image signal is recorded, the image signal stored in the SDRAM 209 is recorded on the recording medium 208 such as a semiconductor memory by the recording medium control unit 207. The ROM 210 stores a control program and a processing program executed by the camera control unit 212 (focus adjustment unit), various data necessary for executing these programs, and the like. The flash ROM 211 stores various setting information regarding the operation of the camera body 20 set by the user.

  The subject detection unit 2121 of the camera control unit 212 detects a specific subject based on the imaging signal input from the image input controller 203 and determines the position of the specific subject in the imaging signal. The subject detection unit 2121 continuously inputs imaging signals from the image input controller 203, and determines the position of the destination subject when the detected specific subject moves. In this way, the subject detection unit 2121 follows the position of a specific subject. The specific subject is, for example, a face subject or a subject existing at a position designated in the imaging screen by the user via the camera operation unit 213. As will be described later, the information on the position and size of the detected specific subject is mainly used to set an area for performing AF (focus detection area).

  The AF signal processing unit 204 (calculation means) performs a correlation operation on the pair of image signals that are AF signals output from the CDS / AGC / AD converter 202, and the image shift amount and reliability of the pair of image signals. Is calculated. The reliability is calculated using the degree of coincidence of two images (a pair of image signals) described later and the steepness of the correlation change amount. The AF signal processing unit 204 sets the position and size of a focus detection area that is an area for performing focus detection and AF within the imaging screen. The AF signal processing unit 204 outputs information on the image shift amount (detection amount) and reliability calculated in the focus detection area to the camera control unit 212. Details of the processing performed by the AF signal processing unit 204 will be described later.

  The AF control unit 2122 in the camera control unit 212 is based on the image shift amount calculated by the AF signal processing unit 204, the reliability, and information indicating the state of the lens unit 10 and the camera body 20, as necessary. The setting of the AF signal processing unit 204 is changed. For example, when the image shift amount is equal to or larger than a predetermined amount, the AF control unit 2122 sets a region for performing the correlation calculation wider than the region set by the AF signal processing unit 204 or sets the contrast of the pair of image signals. Change the type of bandpass filter accordingly. The AF control unit 2122 is designated in the imaging screen by the user via a specific subject detected by the subject detection unit 2121 or the camera operation unit 213 in order to set a focus detection area by the AF signal processing unit 204. The obtained position is transferred to the AF signal processing unit 204. Thereby, the AF control unit 2122 and the AF signal processing unit 204 can set the position and range of the focus detection region based on these pieces of information.

  In the present embodiment, the camera control unit 212 receives a total of three signals from the image sensor 201: an image signal (A + B image signal) and a pair of image signals (A image signal, B image signal) that are AF signals. get. However, in consideration of the load on the image sensor 201, the camera control unit 212 takes out a total of two signals, for example, an image signal (A + B image signal) and one AF signal (A image signal) from the image sensor 201. You may comprise. In this case, the camera control unit 212 calculates the difference ((A + B image signal) − (A image signal)) between the taken imaging signal and the AF image signal as another AF image signal (B image signal). Can be calculated and used. The imaging signal (A + B image signal) and one image signal (A image signal or B image signal) also have parallax.

  The camera control unit 212 controls each unit while exchanging information with each unit in the camera body 20. In addition, the camera control unit 212 performs user operations such as power ON / OFF, change of various settings, imaging processing, AF processing, and recorded image reproduction processing in response to an input from the camera operation unit 213 based on a user operation. Various corresponding processes are executed. Further, the camera control unit 212 transmits a control command for the lens unit 10 (lens control unit 106) and information on the camera body 20 to the lens control unit 106, and acquires information on the lens unit 10 from the lens control unit 106. The camera control unit 212 includes a microcomputer, and controls the entire camera system including the lens unit 10 by executing a computer program stored in the ROM 210. In addition, the camera control unit 212 calculates a defocus amount using the image shift amount in the focus detection area calculated by the AF signal processing unit 204, and passes the lens control unit 106 based on the calculated defocus amount. Controls driving of the focus lens 103.

  Next, a focus adjustment operation (focus control) in the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the procedure of the focus adjustment operation. Each step in FIG. 4 is executed by the camera control unit 212 (mainly the AF control unit 2122) according to a computer program (imaging processing program).

  First, in step S <b> 401, the camera control unit 212 determines whether to perform a focus adjustment operation according to the settings of the camera body 20 and the input signal from the camera operation unit 213. Step S401 is repeated until the focus adjustment operation is started. If the camera control unit 212 determines to execute the focus adjustment operation, the process proceeds to step S402. In step S402, the camera control unit 212 performs exposure on the image sensor 201 to perform live view shooting in order to acquire an AF signal used for imaging plane phase difference AF and an imaging signal used for live view display. Run.

  Subsequently, in step S403, the camera control unit 212 sets appropriate detection characteristics (the frequency band of the image signal used for focus detection) according to the current setting of the camera body 20 and the control state (drive mode) of the focus adjustment operation. Set. For example, as shown in FIG. 5, the camera control unit 212 performs focus detection simultaneously based on the AF operation, the control state (drive mode), and the combination of AF modes (type of focus adjustment operation). And the evaluation band to be used (frequency band of the image signal) are determined. For example, the AF operation and the AF mode are set in response to an input from the user. As the control state, a result selected based on the focus detection result in the previous frame is used.

  FIG. 5 is an explanatory diagram relating to detection characteristic setting (setting of focus detection characteristics). In FIG. 5, the AF operation includes one-shot AF, servo AF, and continuous AF. The control state (drive mode) includes focus stop, target drive, defocus drive, and search drive. The AF mode includes one-point AF, face AF, zone AF, and automatic selection AF. In FIG. 5, the numbers such as 1 point and 9 points indicate the number of focus detection areas in which focus detection is performed simultaneously. The evaluation band of the focus adjustment operation can be changed according to the type of filter applied to the image signal. In this embodiment, three bands of a high band, a middle band, and a low band are used as the evaluation band. Have.

  The high range, the mid range, and the low range are evaluation bands (frequency bands) of AF signals (signal waveforms) used for correlation calculation. Here, with reference to FIG. 2, the characteristics of the high frequency band, the mid frequency band, and the low frequency band (high frequency signal, mid frequency signal, low frequency signal) will be described. FIG. 2 is a relationship diagram between the detection accuracy and the detection defocus amount for each evaluation band of the AF signal. The vertical axis indicates the detection accuracy and the horizontal axis indicates the detection defocus amount. As shown in FIG. 2, the high frequency signal has high detection accuracy, but the range of the detected defocus amount (the defocus amount detectable range) is narrow. For this reason, the high frequency signal is suitably used for focusing in the vicinity of the focused state. On the other hand, the low-frequency signal has a wide detection defocus amount range but low detection accuracy. For this reason, the low frequency signal is suitably used for the direction detection operation at the time of large blur. Further, the mid-frequency signal has characteristics intermediate between both the high-frequency signal and the low-frequency signal.

  In FIG. 5, for example, attention is paid to a case where the AF operation is one-shot AF and the AF mode is set to one-point AF or face AF for performing the focus adjustment operation on one predetermined focus detection region. At this time, since the calculation target area is limited, the camera control unit 212 sets all the evaluation bands of the high, middle, and low bands within a predetermined processing time regardless of the control state of the focus adjustment operation. It is possible to calculate On the other hand, in the case of zone AF or automatic selection AF where it is necessary to perform the main region selection operation in parallel with the focus adjustment operation while simultaneously calculating a plurality of focus detection regions, all evaluation bands are calculated within a predetermined processing time. It is difficult to do. For this reason, it is necessary to effectively switch (select) the evaluation band to be calculated according to the control state.

  In FIG. 5, attention is paid to a case where the AF mode is set to the face AF mode, for example. At this time, in the case of one-shot AF assuming that the subject is stationary during the focus adjustment operation, the calculation target region can be limited. For this reason, regardless of the control state of the focus adjustment operation, it is possible to calculate all the evaluation bands of the high range, the mid range, and the low range within a predetermined processing time. On the other hand, in the case of servo AF or continuous AF assuming that the subject is moving during the focus adjustment operation, it is necessary to perform a main region selection operation in parallel with the focus adjustment operation while simultaneously calculating a plurality of focus detection regions. There is. For this reason, it is difficult to calculate all the evaluation bands within a predetermined processing time, and it is necessary to effectively switch (select) the evaluation bands to be calculated according to the control state.

  In the present embodiment, the types of AF operation, control state, and AF mode are not limited to these, and configurations that do not include some of these, other AF operations, control states, or AF modes The structure containing these may be sufficient. In the present embodiment, the evaluation band is not limited to the three bands of the high band, the middle band, and the low band, and may have two bands or four or more bands.

  Subsequently, in step S404, the AF signal processing unit 204 performs focus detection processing based on a command from the camera control unit 212 (AF control unit 2122). The focus detection process is a process of acquiring information related to the defocus amount and reliability (correlation reliability) for performing imaging plane phase difference AF. Further, the detection characteristics set for the area (focus detection area) in the imaging screen from which information is acquired in the focus detection process are set according to the control state of the camera body 20 and the like. Details of the focus detection process will be described later.

  Subsequently, in step S405, the camera control unit 212 (AF control unit 2122) determines whether or not the processing in steps S403 and S404 has been performed for all the set focus detection areas. If there is a focus detection area where the processes of steps S403 and S404 are not performed, the process returns to step S403, and the AF control unit 2122 performs the processes of steps S403 and S404 on the focus detection area which has not been performed yet. On the other hand, if the processes in steps S403 and S404 have been performed on all focus detection areas, the process proceeds to step S406.

  In step S406, the camera control unit 212 (AF control unit 2122) determines the focus adjustment operation target based on the reliability (correlation reliability) and the detected defocus amount regarding each focus detection area calculated in step S404. The main region (main focus detection region) to be selected is selected. Step S406 is mainly required when the AF mode is zone AF or automatic selection AF. There are various main area selection methods such as face position priority, closest priority, and center priority. In this embodiment, selection can be made using any method according to the application. When the AF mode is single point AF or face AF and only one focus detection area exists, the one focus detection area may be set as the main area.

  Subsequently, in steps S407 to S410, drive control to be performed is selected according to the reliability of focus detection and the defocus amount obtained by focus detection. The selection result here is used for detection characteristic setting (S403) for an image acquired in the next frame. In step S407, the camera control unit 212 (AF control unit 2122) determines whether or not the reliability related to the main area selected in step S406 is greater than or equal to the second reliability threshold value. The reliability is obtained from the above-described degree of coincidence between two images and the steepness of the image shift amount. In the present embodiment, it is preferable to set the maximum value of the reliability range in which the calculated defocus amount cannot be trusted as the second reliability threshold. The reliability can be obtained by using both or one (that is, at least one) of the degree of coincidence between the two images and the steepness of the image shift amount. Further, the reliability may be obtained by using another index such as a signal level of two images.

  If it is determined in step S407 that the reliability is equal to or higher than the second reliability threshold, the process proceeds to step S408, and the AF control unit 2122 has a reliability equal to or higher than the first reliability threshold higher than the second reliability threshold. It is determined whether or not there is. The first reliability threshold value is determined based on the calculated variation in the defocus amount, and it is preferable to set the maximum value of the reliability range in which focusing accuracy cannot be guaranteed.

  If it is determined in step S408 that the reliability is greater than or equal to the first reliability threshold, the process proceeds to step S409. In step S409, the AF control unit 2122 determines whether the defocus amount (detected defocus amount) calculated for the main region selected in step S406 is within the second defocus threshold. The second defocus threshold is determined based on the calculated defocus amount, and the defocus range in which the defocus amount can be detected even when the evaluation band described above is switched to a high region where the defocus amount detection range is narrow. It is preferable to set the maximum value.

  If it is determined that the detected defocus amount is within the second defocus threshold, the process proceeds to step S410, and the AF control unit 2122 is within the first defocus threshold that is smaller than the second defocus amount threshold. It is determined whether or not. The first defocus threshold is determined based on the depth of focus, and is preferably set to the maximum value of the defocus range that can be determined to be in focus.

  If it is determined in step S410 that the detected defocus amount is within the first defocus threshold, the process proceeds to step S411. In step S411, the AF control unit 2122 determines that the subject can be focused (is in focus), and stops the focus lens 103 (focus is stopped). On the other hand, if it is determined that the detected defocus amount is not within the first defocus threshold, the process proceeds to step S412. In step S <b> 412, the AF control unit 2122 calculates the drive amount of the focus lens 103 based on the detected defocus amount, and performs target drive that intermittently drives the focus lens 103 via the focus lens drive unit 105. The target drive is a drive that exclusively performs focus detection processing and focus lens control (focus lens drive) in order to improve detection accuracy and control accuracy in focus adjustment. That is, in target driving, focus detection is performed using an image signal acquired while the focus lens is stopped.

  If it is determined in step S408 that the reliability is not greater than or equal to the first reliability threshold, or if it is determined in step S409 that the detected defocus amount is not within the second defocus threshold, the process proceeds to step S413. In step S413, the AF control unit 2122 calculates a drive amount of the focus lens 103 based on the detected defocus amount, and performs defocus drive that continuously drives the focus lens 103 via the focus lens drive unit 105. . The defocus drive is a drive in which focus detection processing and focus lens control (focus lens drive) are performed in parallel by giving priority to speed over accuracy. That is, in defocus driving, focus detection is performed using an image signal acquired during driving of the focus lens.

  If it is determined in step S407 that the reliability is not equal to or greater than the second reliability threshold, the process proceeds to step S414. In step S414, the AF control unit 2122 calculates the drive amount of the focus lens 103 so that a highly reliable defocus amount is obtained, and also performs search drive that drives the focus lens 103 via the focus lens drive unit 105. I do. The search drive is a drive in which the drive speed is determined according to the depth of focus without using the calculated defocus amount, and the focus detection process and the focus lens control are performed in parallel.

  When the control state of the focus adjustment operation is set in steps S411 to S414, the process proceeds to step S415. In step S415, the camera control unit 212 determines whether to end the focus adjustment operation according to the settings of the camera body 20, the input from the camera operation unit 213, and the control state of the focus adjustment operation. If it is determined not to end the focus adjustment operation, the process returns to step S402. On the other hand, when it is determined that the focus adjustment operation is to be terminated, this flow is terminated. As described above, the camera control unit 212 performs the focus adjustment operation by setting appropriate detection characteristics according to the control state of the AF operation, the AF mode, and the focus adjustment operation.

  Next, the focus detection process (step S404 in FIG. 4) executed by the AF signal processing unit 204 will be described in detail with reference to FIG. FIG. 6 is a flowchart showing the focus detection process. Each step in FIG. 6 is mainly executed by the AF signal processing unit 204 based on a command from the camera control unit 212.

  First, in step S <b> 601, the AF signal processing unit 204 acquires a pair of image signals (image data) as AF signals from a plurality of pixels included in the focus detection area of the image sensor 201. FIG. 7 is an explanatory diagram of the focus detection area 702 on the pixel array 701 of the image sensor 201. Shift areas 703 on both sides of the focus detection area 702 are areas necessary for correlation calculation. Therefore, a region 704 obtained by combining the focus detection region 702 and the shift region 703 is a pixel region necessary for correlation calculation. In FIG. 7, p, q, s, and t are coordinates in the horizontal direction (x-axis direction), p and q are the x-coordinates of the start point and end point of the region 704 (pixel region), and s and t are The x-coordinates of the start point and end point of the focus detection area 702 are respectively shown.

  FIG. 8 is an explanatory diagram of AF signals (a pair of image signals) acquired from a plurality of pixels included in the focus detection area 702 of FIG. In FIG. 8, a solid line 801 is one of the pair of image signals (A image signal), and a broken line 802 is the other of the pair of image signals (B image signal). 8A shows the A image signal and the B image signal before the shift, and FIGS. 8B and 8C show the A image signal and the B image signal in the plus direction from the state of FIG. The state shifted in the minus direction is shown.

  Subsequently, in step S602 in FIG. 6, the AF signal processing unit 204 relatively shifts the pair of image signals (A image signal and B image signal) acquired in step S601 by one pixel (1 bit). The correlation amount (correlation data) between the pair of image signals is calculated. The AF signal processing unit 204, for each of a plurality of pixel lines (scanning lines) provided in the focus detection region, as shown in FIGS. 8B and 8C, the A image signal 801 and the B image signal 802. Both are shifted by one bit in the direction of the arrow. The AF signal processing unit 204 calculates a correlation amount of a pair of image signals (A image signal 801 and B image signal 802) for each of the plurality of scanning lines, and adds and averages the correlation amounts of the plurality of scanning lines. One correlation amount is calculated.

  In the present embodiment, when the correlation amount is calculated, the pair of image signals are relatively shifted pixel by pixel, but the present invention is not limited to this. For example, a pair of image signals may be shifted in units of a larger number of pixels, such as relatively shifting two pixels at a time. In this embodiment, one correlation amount is calculated by averaging the correlation amounts for each of a plurality of scanning lines. However, the present invention is not limited to this. For example, it may be configured to perform addition averaging on a pair of image signals for each of a plurality of scanning lines, and then calculate a correlation amount for the pair of image signals obtained by addition averaging.

  The correlation amount COR [i] can be calculated using the following equation (1).

  In Expression (1), i is the shift amount, ps is the maximum shift amount in the negative direction, qt is the maximum shift amount in the positive direction, x is the start coordinate of the focus detection region 702, and y is the focus detection region 702. End coordinate.

  Here, the relationship between the shift amount and the correlation amount COR will be described with reference to FIG. FIGS. 9A and 9B are explanatory diagrams of the relationship between the shift amount and the correlation amount COR. FIG. 9B is an enlarged view of the region 902 in FIG. In FIG. 9A, the horizontal axis indicates the shift amount, and the vertical axis indicates the correlation amount COR. Among the regions 902 and 903 near the extreme value in the correlation amount 901 that changes with the shift amount, the degree of coincidence of the pair of image signals (A image signal and B image signal) becomes the highest in the shift amount corresponding to the smaller correlation amount. .

  Subsequently, in step S603 of FIG. 6, the AF signal processing unit 204 calculates a correlation change amount based on the correlation amount calculated in step S602. In the present embodiment, the difference in the correlation amount at every other shift in the waveform of the correlation amount 901 shown in FIG. 9A is calculated as the correlation change amount. The correlation change amount ΔCOR [i] can be calculated using the following equation (2).

  Subsequently, in step S604, the AF signal processing unit 204 calculates an image shift amount using the correlation change amount calculated in step S603. Here, the relationship between the shift amount and the correlation change amount ΔCOR will be described with reference to FIG. 10A and 10B are explanatory diagrams of the relationship between the shift amount and the correlation change amount ΔCOR. FIG. 10B is an enlarged view of a region 1002 in FIG. In FIG. 10A, the horizontal axis indicates the shift amount, and the vertical axis indicates the correlation change amount ΔCOR. The correlation change amount 1001 that changes with the shift amount changes from positive to negative in the regions 1002 and 1003. A state in which the amount of correlation change is 0 is called zero crossing, and the degree of coincidence between a pair of image signals (A image signal and B image signal) is the highest. For this reason, the shift amount giving the zero cross is the image shift amount.

  In FIG. 10B, 1004 is a part of the correlation change amount 1001. The shift amount (k−1 + α) giving the zero cross is divided into an integer part β (= k−1) and a decimal part α. The decimal part α can be calculated using the following equation (3) from the similar relationship between the triangle ABC and the triangle ADE in FIG.

  The integer part β can be calculated using the following formula (4) from FIG.

  That is, the image shift amount PRD can be calculated from the sum of the decimal part α and the integer part β. As shown in FIG. 10A, when there are a plurality of zero crossings of the correlation change amount ΔCOR, the one having the larger steepness of the change in the correlation change amount ΔCOR in the vicinity thereof is defined as the first zero cross. This steepness is an index indicating the ease of performing AF, and the greater the value, the easier it is to perform highly accurate AF. The steepness maxder can be calculated using the following equation (5).

  In the present embodiment, when there are a plurality of zero crosses of the correlation change amount, the first zero cross is determined based on the steepness, and the shift amount giving the first zero cross is set as the image shift amount.

  Subsequently, in step S605 of FIG. 6, the AF signal processing unit 204 calculates a reliability (correlation reliability) representing the high reliability of the image shift amount calculated in step S604. The reliability of the image shift amount can be defined by the degree of coincidence (a degree of coincidence between two images) fnclvl of a pair of image signals (A image signal and B image signal) and the steepness of the correlation change amount ΔCOR described above. . The degree of coincidence between the two images is an index representing the accuracy of the image shift amount, and here, the smaller the value, the better the accuracy. In FIG. 9B, 904 is a part of the correlation amount 901. The coincidence degree fnclvl of the two images can be calculated using the following equation (6).

  Finally, in step S606 of FIG. 6, the AF signal processing unit 204 calculates the defocus amount related to the target focus detection region using the image shift amount calculated in step S604, and this flow (focus detection). Process).

  According to the present embodiment, the detection characteristics such as the number of focus detection areas to be calculated simultaneously and the evaluation band of the AF signal are appropriately set according to the control state of the AF operation, the focus adjustment operation, and the combination of the AF modes. can do. For this reason, according to the present embodiment, it is possible to stably realize a high-speed and high-precision focus adjustment operation.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. This embodiment is different from the first embodiment in setting detection characteristics (step S403 in FIG. 4). In other words, the camera control unit 212 sets a plurality of focus detection areas, and according to the type of focus detection area (whether the focus detection area is the main area) as a detection characteristic setting target as the type of focus adjustment operation. Change the detection characteristics. Other configurations and operations are the same as those in the first embodiment, and thus description thereof is omitted.

  FIG. 11 is a flowchart showing detection characteristic setting (step S403) in the present embodiment. Each step of FIG. 11 is mainly executed by the camera control unit 212.

  First, in step S1101, the camera control unit 212 determines whether or not the focus detection area for which the detection characteristic is to be set is the main area (main focus detection area) determined in step S405 in FIG. If it is determined in step S1101 that the focus detection area is the main area, the process proceeds to step S1102. In step S <b> 1102, the camera control unit 212 sets the detection characteristics of the high band, the mid band, and the low band (high band + middle band + low band). The high band, the middle band, and the low band are the evaluation bands of the AF signal (signal waveform) used for the correlation calculation, and are as described with reference to FIG.

  On the other hand, if it is determined in step S1101 that the focus detection area is not the main area, the process proceeds to step S1103. In step S1103, the camera control unit 212 determines the control state of the focus lens 103 (control state of focus adjustment operation, drive mode). If it is determined in step S1103 that the control state (drive mode) is target drive, the process proceeds to step S1104. In step S <b> 1104, the camera control unit 212 sets detection characteristics for a high range and a mid range (high range + mid range). On the other hand, if it is determined in step S1103 that the control state is defocus driving or search driving, the process proceeds to step S1105. In step S <b> 1105, the camera control unit 212 sets detection characteristics for the middle range and the low range (middle range + low range).

  In a case where a plurality of focus detection areas are set, if focus detection is performed using all detection characteristics (that is, high band + middle band + low band AF signals) for all focus detection areas, a predetermined value is obtained. It is difficult to perform the correlation calculation for all evaluation bands within the processing time. On the other hand, if focus detection is performed using the AF signal in the high region + middle region or medium region + low region in order to complete the correlation calculation in a predetermined processing time, the focus detection accuracy decreases or the focus adjustment operation May take some time. However, as in the present embodiment, the detection characteristic (evaluation band for AF signal) set in the main area that is directly linked to the control of the focus adjustment operation is set to high band + middle band + low band, thereby stabilizing Therefore, it is possible to realize a focus adjustment operation with high speed and high accuracy.

  According to the present embodiment, the detection characteristics of the AF signal can be appropriately set according to whether or not the target focus detection area is the main area. For this reason, according to the present embodiment, it is possible to stably realize a high-speed and high-precision focus adjustment operation.

(Third embodiment)
Next, a third embodiment of the present invention will be described. This embodiment is different from the first embodiment in that the second defocus threshold is set (changed) in accordance with at least one of the photographing condition and the state of the AF image signal.

  With reference to FIG. 12, the focus adjustment operation (focus control) in the present embodiment will be described. FIG. 12 is a flowchart showing the procedure of the focus adjustment operation in the present embodiment. FIG. 12 differs from FIG. 4 only in that step S420 is inserted between step S408 and step S409 in FIG. 4, and thus description of steps other than step S420 is omitted.

  If it is determined in step S408 that the reliability is greater than or equal to the first reliability threshold, the process proceeds to step S420. In step S420, the AF control unit 2122 sets a second defocus threshold value. Normally, the second defocus threshold is determined based on the calculated defocus amount, and the defocus amount that can detect the defocus amount even when the evaluation band is switched to a high region where the defocus amount detection range is narrow. It is preferable to set the maximum value of the range. However, in the present embodiment, by setting an appropriate value according to the shooting conditions and the state of the AF image signal, the target drive (step S412) and the defocus drive (step S413) are effectively switched to perform AF. One of the purposes is to achieve both the accuracy and speed of operation. In the present embodiment, as the imaging condition, the amount of image plane movement until reaching the in-focus state, which is determined according to the focal length and the state of the aperture (aperture diameter), is used. Then, the image plane movement amount until reaching the in-focus state is larger than the predetermined value, and the state of the AF image signal such as the degree of coincidence of the two images, the steepness of the image shift amount, and the signal level of the two images is good. In this case, the second defocus threshold is set to be large with respect to normal shooting conditions. Note that the shooting conditions to be used at this time may be appropriately added as necessary, such as brightness and camera shake state.

  As described above, in the present embodiment, an appropriate second defocus threshold value is set according to the photographing condition and the state of the AF image signal. Thereby, it is possible to effectively switch between the target drive (step S412) and the defocus drive (step S413) to achieve both the precision and speed of the AF operation.

  FIG. 13 is an explanatory diagram of the relationship between the reliability and the detected defocus amount in the focus adjustment operation described with reference to FIG. FIG. 13A shows a case where the image plane movement amount (image plane movement amount under a predetermined condition) is normal (first photographing state), and FIG. 13B shows a case where the image plane movement amount is larger than that in FIG. (Second shooting state) is shown. In FIGS. 13A and 13B, the horizontal axis represents the reliability, and the value increases as the reliability approaches the focused state and becomes higher. The vertical axis represents the detected defocus amount, and the value decreases as the detected defocus amount decreases as the focus state is approached.

  As described above, the driving state of the focus lens 103 is determined according to the reliability and the detected defocus amount. In general, the state transition is performed in the order of search drive (step S414), defocus drive (step S413), and target drive (step S412) from the greatly left upper left state, and finally the right lower right in focus. In this state, the focus is stopped (step S411). In the present embodiment, as described in step S420, the second defocus threshold value is increased when the amount of image plane movement up to the in-focus state is large according to the focal length, the state of the stop, and the like. As a result, it is possible to relax the condition for shifting from the defocus drive (step S413) to the target drive (step S412) and to shorten the focusing time.

  Thus, in each embodiment, the control device includes a calculation unit (AF signal processing unit 204) and a focus adjustment unit (camera control unit 212). The calculation means corresponds to the first signal (signal corresponding to the A image signal) and the second signal (corresponding to the B image signal) corresponding to the light beams (output signals from the image sensor 201) that have passed through different pupil regions of the imaging optical system. The defocus amount is calculated based on the signal to be transmitted. The focus adjustment unit performs a focus adjustment operation (focus control) based on the defocus amount. The focus adjustment unit changes the detection characteristics of the first signal and the second signal by the calculation unit according to the type of the focus adjustment operation.

  Preferably, the detection characteristic includes a characteristic relating to a frequency band (evaluation band) of the first signal and the second signal used by the calculation unit to calculate the defocus amount. The change of the evaluation band can be realized by changing the filter (filter band such as high band, middle band, low band, etc.) applied to the first signal and the second signal in the calculation means. More preferably, the focus adjustment unit selectively sets one drive mode as a type of the focus adjustment operation from a plurality of drive modes (a plurality of control states shown in FIG. 5) in which the focus adjustment operation is performed. The plurality of drive modes include a first drive mode (target drive) and a second drive mode (defocus drive or search drive). The first drive mode is a drive mode in which a focus adjustment operation is performed using the first signal and the second signal acquired while the focus lens of the imaging optical system is stopped. The second drive mode is a drive mode in which a focus adjustment operation is performed using the first signal and the second signal acquired during driving of the focus lens. The focus adjusting unit changes the detection characteristic according to the drive mode. More preferably, the calculation unit selects one drive mode from a plurality of drive modes according to the defocus amount (S409 to S414). Preferably, the calculation unit calculates the reliability relating to the first signal and the second signal, and the focus adjustment unit selects one drive mode from a plurality of drive modes according to the reliability (S407, S408, S411). ~ S414).

  Preferably, the focus adjustment unit has a frequency band in which the first frequency band (high range + middle range) in the first drive mode is higher than the second frequency band (middle range + low range) in the second drive mode. Set as follows. Preferably, the detection characteristic includes the number of focus detection areas for detecting the first signal and the second signal (FIG. 5). More preferably, the focus adjustment means sets the number of focus detection areas in the first drive mode to be smaller than the number of focus detection areas in the second drive mode (FIG. 5).

  Preferably, the focus adjusting unit sets a plurality of focus detection areas for detecting the first signal and the second signal. The focus adjustment means detects the detection characteristics according to the type of focus detection area (whether the focus detection area is the main area) to be set as a detection characteristic among a plurality of focus detection areas as the type of focus adjustment operation. Is changed (S1101 to S1105). More preferably, the focus adjusting unit determines a main area from a plurality of focus detection areas, and changes detection characteristics between the main area and another area among the plurality of focus detection areas (S1101 to S1105). More preferably, the frequency band as the detection characteristic for the main area is wider than the frequency band for the other areas (S1102, S1104, S1105).

  Preferably, the focus adjustment unit changes a defocus amount threshold (second defocus threshold) for selecting one drive mode (defocus drive) from a plurality of drive modes based on the state of the imaging optical system. To do. More preferably, the imaging optical system has a first shooting state (FIG. 13A) and a second shooting state (FIG. 13B) in which the image plane movement amount under a predetermined condition is larger than the first shooting state. Have. Then, the focus adjustment unit makes the defocus amount threshold value (second defocus threshold value) in the second shooting state larger than the defocus amount threshold value in the first shooting state. More preferably, the second shooting state has a longer focal length than the first shooting state. Preferably, in the second shooting state, the aperture diameter is smaller than that in the first shooting state.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  According to each embodiment, it is possible to provide a control device, an imaging device, a control method, a program, and a storage medium capable of stably performing high-speed and high-precision focus adjustment.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

204 AF signal processor (calculation means)
212 Camera control unit (focus adjustment means)

Claims (21)

Calculating means for calculating a defocus amount based on a first signal and a second signal corresponding to light beams that have passed through different pupil regions of the imaging optical system;
Focus adjusting means for performing a focus adjustment operation based on the defocus amount,
The control device, wherein the focus adjustment unit changes detection characteristics of the first signal and the second signal by the calculation unit according to a type of the focus adjustment operation.   The control device according to claim 1, wherein the detection characteristic includes a characteristic relating to a frequency band of the first signal and the second signal used by the calculation unit to calculate the defocus amount. The focus adjustment means selectively sets one drive mode as a type of the focus adjustment operation from a plurality of drive modes for performing the focus adjustment operation,
The plurality of drive modes are:
A first drive mode in which the focus adjustment operation is performed using the first signal and the second signal acquired while the focus lens of the imaging optical system is stopped;
A second drive mode for performing the focus adjustment operation using the first signal and the second signal acquired during driving of the focus lens,
The control apparatus according to claim 2, wherein the focus adjustment unit changes the detection characteristic according to the drive mode.   The control apparatus according to claim 3, wherein the focus adjustment unit selects the one drive mode from the plurality of drive modes according to the defocus amount. The calculating means calculates reliability related to the first signal and the second signal;
5. The control device according to claim 3, wherein the focus adjustment unit selects the one drive mode from the plurality of drive modes according to the reliability.   The calculating means calculates the reliability based on the degree of coincidence between the first signal and the second signal and the steepness of the correlation change amount between the first signal and the second signal. The control device according to claim 5.   The focus adjusting unit sets the first frequency band in the first driving mode as the frequency band to be higher than the second frequency band in the second driving mode. 7. The control device according to any one of 6.   The control device according to claim 3, wherein the detection characteristic includes a number of focus detection areas for detecting the first signal and the second signal.   The focus adjustment unit sets the number of focus detection areas in the first drive mode to be smaller than the number of focus detection areas in the second drive mode. Control device. The focusing means is
Setting a plurality of focus detection areas for detecting the first signal and the second signal;
4. The detection characteristic according to claim 1, wherein the detection characteristic is changed according to a type of a focus detection area that is a setting target of the detection characteristic among the plurality of focus detection areas as a type of the focus adjustment operation. The control device according to claim 1. The focusing means is
Determining a main region from the plurality of focus detection regions;
The control device according to claim 10, wherein the detection characteristic is changed between the main region and another region among the plurality of focus detection regions.   The control device according to claim 11, wherein a frequency band as the detection characteristic relating to the main area is wider than a frequency band relating to the other area. An imaging device having a first photoelectric conversion unit and a second photoelectric conversion unit that receive light beams passing through different pupil regions of the imaging optical system;
Calculating means for calculating a defocus amount based on a first signal and a second signal respectively corresponding to output signals from the first photoelectric conversion unit and the second photoelectric conversion unit;
Focus adjusting means for performing a focus adjustment operation based on the defocus amount,
The imaging apparatus, wherein the focus adjustment unit changes detection characteristics of the first signal and the second signal by the calculation unit according to a type of the focus adjustment operation.   The image pickup device includes the first photoelectric conversion unit and the second photoelectric conversion unit with respect to one microlens, and the microlens is two-dimensionally arranged. The imaging device described. Calculating a defocus amount based on a first signal and a second signal corresponding to light beams that have passed through different pupil regions of the imaging optical system;
Performing a focus adjustment operation based on the defocus amount,
The control method characterized in that, in the step of performing the focus adjustment operation, detection characteristics of the first signal and the second signal are changed according to the type of the focus adjustment operation. Calculating a defocus amount based on a first signal and a second signal corresponding to light beams that have passed through different pupil regions of the imaging optical system;
Performing a focus adjustment operation based on the defocus amount, and causing the computer to execute a program,
In the step of performing the focus adjustment operation, the detection characteristic of the first signal and the second signal is changed according to the type of the focus adjustment operation.   A storage medium storing the program according to claim 16.   5. The focus adjustment unit changes a threshold value of the defocus amount for selecting the one drive mode from the plurality of drive modes based on a state of the imaging optical system. The control device described. The imaging optical system has a first shooting state and a second shooting state in which an image plane movement amount in a predetermined condition is larger than the first shooting state,
19. The focus adjustment unit according to claim 18, wherein the focus adjustment unit makes the threshold value of the defocus amount in the second shooting state larger than the threshold value of the defocus amount in the first shooting state. Control device.   The control apparatus according to claim 19, wherein the second imaging state has a longer focal length than the first imaging state.   The control device according to claim 19, wherein the second photographing state has a smaller aperture diameter than the first photographing state.