JP2020003553A - Control device, imaging apparatus, control method, program, and, storage medium - Google Patents

Abstract

To provide a control device capable of swiftly and precise focusing.SOLUTION: The control device includes: calculation means (204) configured to calculate the defocus amount on the basis of a first signal and a second signal corresponding to the light flux passing through the different pupil areas of a lens unit; and focusing means (2122) that performs focusing on the basis of the defocus amount. The focusing means (2122) performs focus determination on the basis of control characteristic information of lens unit.SELECTED DRAWING: Figure 1

Description

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

  In an interchangeable lens type imaging apparatus, it is important to realize autofocus control (AF control) that achieves both speed and accuracy in accordance with the optical characteristics and mechanical characteristics of an interchangeable lens mounted on the imaging apparatus body. For example, Patent Literature 1 discloses a camera body that determines a focusing range of a phase difference AF based on information on a permissible circle of confusion that the interchangeable lens can support.

Japanese Patent No. 5797902

  However, the camera body disclosed in Patent Literature 1 determines an in-focus range based on the strictest shooting conditions (focal length). For this reason, the accuracy of focus adjustment may decrease depending on the shooting conditions.

  Therefore, an object of the present invention is to provide a control device, an imaging device, a control method, a program, and a storage medium that can perform high-speed and high-precision focus adjustment.

  A control device according to one aspect of the present invention includes: a calculating unit configured to calculate 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 lens unit; And a focus adjustment unit that performs focus adjustment based on the control unit, and the focus adjustment unit performs focus determination based on control characteristic information of the lens unit.

  A control device according to another aspect of the present invention includes: a calculating unit configured to calculate a defocus amount based on a first signal and a second signal corresponding to a light beam that has passed through mutually different pupil regions of a lens unit; Focus adjustment means for performing focus adjustment based on the following.If the defocus amount is within the first focus range, the focus adjustment means determines that the object is in focus, and the defocus amount is If not in the first focus range and in a second focus range wider than the first focus range, it is determined that the camera is in focus after driving the focus lens of the lens unit based on the defocus amount. I do.

  An imaging device according to another aspect of the present invention includes an imaging device that outputs a first signal and a second signal that respectively correspond to light beams that pass through different pupil regions of a lens unit, and the control device.

  A control method according to another aspect of the present invention includes a step of calculating a defocus amount based on a first signal and a second signal corresponding to a light beam that has passed through different pupil regions of a lens unit; Adjusting the focus based on the control characteristic information of the lens unit.

  A control method according to another aspect of the present invention includes a step of calculating a defocus amount based on a first signal and a second signal corresponding to a light beam that has passed through different pupil regions of a lens unit; Performing a focus adjustment based on the information.In the step of performing the focus adjustment, when the defocus amount is within the first focus range, it is determined that the object is in focus, and the defocus amount is determined by the When not in one focus range and in a second focus range wider than the first focus range, it is determined that a focus state is established after driving a focus lens of the lens unit based on the defocus amount. .

  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 present invention will be 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 that can perform high-speed and high-precision focus adjustment.

It is a block diagram of an imaging device in each embodiment. It is an explanatory view of a problem in the conventional technology. FIG. 3A is a diagram illustrating an example of a pixel configuration of a non-imaging plane phase difference method and FIG. 5 is a flowchart of a focus adjustment operation according to the first embodiment. 9 is a flowchart illustrating focus detection processing in each embodiment. FIG. 3 is an explanatory diagram of a focus detection area in each embodiment. FIG. 4 is an explanatory diagram of an AF signal (a pair of image signals) in each embodiment. FIG. 4 is an explanatory diagram of a relationship between a shift amount of an AF signal and a correlation amount in each embodiment. FIG. 4 is an explanatory diagram of a relationship between a shift amount of an AF signal and a correlation change amount in each embodiment. FIG. 7 is an explanatory diagram of an effect in the first embodiment. It is a flowchart of the focus adjustment operation in the second embodiment. 13 is a flowchart of a focus adjustment operation according to the third embodiment.

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

(1st Embodiment)
First, the configuration of the imaging device 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 apparatus 100 (interchangeable lens camera system) according to the present embodiment. The imaging apparatus 100 includes a camera body 20 (imaging apparatus body) and a lens unit 10 (interchangeable lens) that is detachable from the camera body 20. The lens control unit 106 that controls the entire operation of the lens unit 10 and the camera control unit 212 that controls the entire operation of the imaging apparatus 100 (camera system) including the lens unit 10 include terminals provided on a lens mount. (Not shown). Note that the present embodiment is also applicable to an imaging device 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 aperture 102, and the focus lens 103 form an imaging optical system. The diaphragm 102 is driven by a diaphragm driving unit 104 and controls the amount of light incident on an image sensor 201 described later. The focus lens 103 is driven by the focus lens drive 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 by which the user performs settings related to the operation of the lens unit 10 such as switching between AF (autofocus) / MF (manual focus) mode, position adjustment of the focus lens 103 by MF, and setting of a camera shake correction mode. Device group. 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. Further, the lens control unit 106 transmits the 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 to output 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 signal charges corresponding to the amount of incident light by pixels (photodiodes) arranged in the image pickup device 201. The signal charges stored in each photodiode are sequentially read out from the image sensor 201 as a voltage signal corresponding to the signal charges based on a 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 for the pair of photodiodes A and B (the photodiodes A and B are shared). It is configured to include one micro lens. That is, the imaging element 201 has a pair of photodiodes (first photoelectric conversion unit and second photoelectric conversion unit) for one microlens, and a plurality of microlenses are two-dimensionally arranged. Each pixel divides incident light with a microlens to form a pair of optical images on a pair of photodiodes A and B. The pair of photodiodes A and B form a pair of optical images used for AF signals described later. It outputs pixel signals (A image signal and B image signal). Further, by adding the outputs of the pair of photodiodes A and B, an imaging signal (A + B image signal) can be obtained.

  By synthesizing a plurality of A image signals and a plurality of B image signals output from a plurality of pixels, respectively, an AF signal (focus detection) used for AF (imaging plane phase difference AF) by an imaging plane phase difference detection method is used. A pair of image signals 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) which is a shift amount of the pair of image signals, and further calculates a data of the imaging optical system from the image shift amount. The focus amount (and the defocus direction) is calculated.

  As described above, the imaging element 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 electric signal, and outputs image data (image signal). The image sensor 201 according to the present embodiment is provided with two photodiodes for one microlens, and can generate an image signal used for focus detection by the imaging surface phase difference AF method. Note that the number of photodiodes (division PDs) sharing one microlens may be changed, such as providing four photodiodes for one microlens.

  FIG. 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. In each of the pixel configurations of FIGS. 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. Is shown. 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 supporting the imaging plane phase difference AF method shown in FIG. , Two photodiodes A and B divided in the horizontal direction in FIG. 3B are provided. The photodiodes A and B (the first photoelectric conversion unit and the second photoelectric conversion unit) receive light beams that have passed through mutually different pupil regions of the imaging optical system. Since the photodiodes A and B receive light beams that have passed through different areas of the exit pupil of the imaging optical system, the B image signal has parallax with the A image signal. Note that the pixel dividing method illustrated in FIG. 3B is an example, and the pixel is divided in the vertical direction in FIG. 3B, or the pixel is divided into two in the horizontal and vertical directions (a total of four). Other configurations may be adopted. In addition, a plurality of types of pixels divided by different division methods may be included in the same image sensor.

  In the present embodiment, a configuration is shown 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. However, the present invention is not limited to this. Not something. For example, the focus detection pixel may have a configuration in which one PD is provided below the microlens and pupil division is performed by shielding the light from left and right or up and down by a light shielding layer. Alternatively, a configuration may be adopted 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 on the AF signal and the imaging signal read from the imaging element 201 to remove reset noise. The CDS / AGC / AD converter 202 outputs the imaging signal and the AF signal that have been subjected to these processes to the image input controller 203 and the AF signal processing unit 204.

  The image input controller 203 stores the imaging signal output from the CDS / AGC / AD converter 202 in the SDRAM 209 via the bus 21 as an image signal. 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 for recording an image signal, the image signal stored in the SDRAM 209 is recorded by the recording medium control unit 207 on a recording medium 208 such as a semiconductor memory. The ROM 210 (storage means) stores control programs and processing programs executed by the camera control unit 212, and various data necessary for executing these programs. The flash ROM 211 stores various setting information related to 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. Further, the subject detection unit 2121 continuously inputs an imaging signal from the image input controller 203, and determines the position of the destination subject when the detected specific subject has moved. Thus, 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 by the user via the camera operation unit 213 in the imaging screen. As will be described later, the detected information on the position and size of the specific subject is mainly used to set an area where AF is performed (focus detection area).

  The AF signal processing unit 204 (calculation unit) performs a correlation operation on a pair of image signals, which are AF signals output from the CDS / AGC / AD converter 202, and calculates an image shift amount and reliability of the pair of image signals. Is calculated. The reliability is calculated using the coincidence between two images (a pair of image signals) and the steepness of the correlation change amount described later. Further, the AF signal processing unit 204 sets the position and size of a focus detection area, which is an area where focus detection and AF are performed in the imaging screen. The AF signal processing unit 204 outputs to the camera control unit 212 information on the image shift amount (detection amount) and reliability calculated in the focus detection area. The 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 performs an operation based on information indicating the image shift amount and reliability calculated by the AF signal processing unit 204 and information indicating the state of the lens unit 10 and the camera body 20 as necessary. Then, the setting of the AF signal processing unit 204 is changed. For example, when the image shift amount is equal to or more than the predetermined amount, the AF control unit 2122 sets the area where the correlation calculation is performed to be wider than the area set by the AF signal processing unit 204, or adjusts the contrast of a pair of image signals. Change the type of bandpass filter accordingly. In addition, the AF control unit 2122 is used to set a focus detection area by the AF signal processing unit 204, to specify a specific subject detected by the subject detection unit 2121, or to specify a specific subject in the imaging screen via the camera operation unit 213. The position is transferred to the AF signal processing unit 204. Accordingly, the AF control unit 2122 and the AF signal processing unit 204 can set the position and range of the focus detection area based on the information.

  In the present embodiment, the camera control unit 212 outputs a total of three signals from the image sensor 201, i.e., a pair of image signals (A image signal and B image signal), which are an imaging signal (A + B image signal) and an AF signal. get. However, in consideration of the load of the image sensor 201, the camera control unit 212 extracts two signals from the image sensor 201, for example, an image signal (A + B image signal) and one AF signal (A image signal). May be configured. In this case, the camera control unit 212 determines the difference ((A + B image signal) − (A image signal)) between the taken-out imaging signal and AF image signal by using another AF image signal (B image signal). Can be calculated and used. Note that the imaging signal (A + B image signal) and one of the image signals (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 responds to an input from the camera operation unit 213 based on a user's operation to perform a user operation such as power ON / OFF, change of various settings, imaging processing, AF processing, and playback processing of a recorded image. Execute various corresponding processes. Further, the camera control unit 212 transmits a control command to the lens unit 10 (the 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. Further, 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 via the lens control unit 106 based on the calculated defocus amount. The driving of the focus lens 103 is controlled.

  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 S401, the camera control unit 212 determines whether or not to execute a focus adjustment operation according to the settings of the camera body 20 and an 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 communicates with the lens control unit 106 through a terminal provided on the lens mount, and acquires (receives) the minimum drivable amount of the focus lens 103 in the current state of the lens unit 10. . In the present embodiment, the camera control unit 212 acquires the minimum drivable amount as a mechanical drive amount of the focus lens 103 as a pulse count value. However, the present invention is not limited to this, and obtains the minimum drivable amount as a physical movement amount obtained by multiplying a pulse count value by an extension amount, or an image plane change amount obtained by multiplying them by focus sensitivity. May be.

  Subsequently, in step S403, the AF signal processing unit 204 performs a focus detection process based on a command from the camera control unit 212 (AF control unit 2122). The focus detection process is a process of acquiring information regarding the defocus amount and reliability (correlation reliability) for performing the imaging surface phase difference AF. Further, detection characteristics set for an area (focus detection area) in the imaging screen from which information is acquired in the focus detection processing are set according to the state of the camera body 20 and the like. The details of the focus detection processing will be described later.

  Subsequently, in step S404, the camera control unit 212 (AF control unit 2122) determines whether the reliability (correlation reliability) calculated in step S403 is equal to or greater than a second reliability threshold. The reliability is obtained from the coincidence between the two images and the steepness of the image shift amount. In the present embodiment, it is preferable to set, as the large threshold, the highest value in the reliability range in which the calculated defocus amount cannot be relied on. The reliability can be obtained by using both or one (that is, at least one) of the 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 S404 that the reliability is equal to or higher than the second reliability threshold, the process proceeds to step S405, where the AF control unit 2122 determines that the reliability is 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 detection variation of the defocus amount, and is preferably set to the highest value of a reliability range in which focusing accuracy cannot be guaranteed.

  If it is determined in step S405 that the reliability is equal to or greater than the first reliability threshold, the process proceeds to step S406. In step S406, the AF control unit 2122 determines whether the defocus amount (detected defocus amount) calculated in step S403 is within the second defocus amount threshold. The second defocus amount threshold is determined based on the calculated defocus amount, and the defocus range in which the defocus amount can be detected even when the above-described evaluation band is switched to a high range where the detection range of the defocus amount is narrow. Is preferably set.

  If it is determined that the detected defocus amount is within the second defocus amount threshold, the process proceeds to step S407, where the AF control unit 2122 determines that the detected defocus amount is smaller than the second defocus amount threshold. It is determined whether it is within the threshold. The first defocus amount threshold value is determined based on the depth of focus, and it is preferable to set a maximum value of a defocus range in which a focus state can be determined.

  If it is determined in step S407 that the detected defocus amount is not within the first defocus amount threshold, the process proceeds to step S408. In step S408, the AF control unit 2122 determines whether the detected defocus amount is equal to or less than the minimum drivable amount acquired in step S402 (that is, equal to or less than the image plane movement amount corresponding to the minimum drivable amount). . Here, originally, if the detected defocus amount is not within the first defocus amount threshold value in step S407, the focusing accuracy required for focusing has not been obtained, so that the target driving in step S410 described later further increases the focus accuracy. Focusing is required. However, if the control characteristics of the focus lens 103 of the lens unit 10 mounted on the camera body 20 are not sufficient and the accuracy cannot be expected to be improved even after the subsequent target driving, it is necessary to perform further focusing. Therefore, the determination in step S408 is performed.

  If it is determined in step S407 that the detected defocus amount is within the first defocus amount threshold, or if it is determined in step S408 that the detected defocus amount is equal to or less than the minimum drivable amount, step S409 is performed. Proceed to. In step S409, the AF control unit 2122 determines that the subject has been focused (is in a focused state), and stops the focus lens 103 (stops focusing).

  Here, the effects of the present embodiment will be described with reference to FIGS. 2A and 2B are explanatory diagrams of the problem of the prior art. FIG. 2A shows a case where the minimum drivable amount is within the focusing range, and FIG. Each is shown. FIG. 10 is an explanatory diagram of the effect in the present embodiment. 2A, 2B, and 10, the horizontal axis indicates the zoom position (the position of the zoom lens, the focal length), and the vertical axis indicates the focus position (the position of the focus lens 103). .

  For example, when it is determined that the focus state is established when the focus position (defocus amount) is within the range of ４ Fδ, the minimum driveable amount x of the focus lens is determined as shown in FIG. There is no problem if it is sufficiently smaller than １ ／ Fδ which is the focus determination criterion. On the other hand, as shown in FIG. 2B, when the minimum drivable amount y of the focus lens exceeds １ ／ Fδ depending on the focal length (on the telephoto side of the zoom position Z1) depending on the type of the lens unit. There is. In such a case, in the related art disclosed in Patent Document 1, the allowable circle of confusion is increased, that is, the focus determination criterion is reduced (increased) from ４Fδ to δFδ. As a result, the accuracy of focus control on the wide-angle side decreases.

  On the other hand, in the present embodiment, as shown in FIG. 10, a condition (focusing determination criterion) for performing the focusing determination is changed based on the information regarding the minimum drivable amount. That is, focus determination is performed based on the defocus amount and information on the minimum drivable amount. For example, when the defocus amount is smaller than the minimum drivable amount y (on the telephoto side than the zoom position Z1), even when the defocus amount is larger than 1 / 4Fδ, which is the focus determination criterion, the minimum drivable amount y In the following cases, it is determined that the object is in focus. In this way, even when there is a problem as shown in FIG. 2B, it is possible to achieve both accuracy and speed by setting necessary and sufficient focus determination conditions as shown in FIG. It becomes. This effect is similarly obtained in each embodiment described later.

  On the other hand, it is determined that the detected defocus amount is not within the first defocus amount threshold value and the detected defocus amount is not smaller than the minimum drivable amount (or smaller than the image plane movement amount corresponding to the minimum drivable amount). In this case, the process proceeds to step S410. In step S410, the AF control unit 2122 calculates a drive amount of the focus lens 103 based on the detected defocus amount, and performs a target drive for intermittently driving 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 increase detection accuracy and control accuracy in focus adjustment. That is, in the target drive, focus detection is performed using the image signal acquired while the focus lens is stopped.

  If it is determined in step S405 that the reliability is not equal to or greater than the first reliability threshold, or if it is determined in step S406 that the detected defocus amount is not within the second threshold value, the process proceeds to step S411. In step S411, the AF control unit 2122 calculates the driving amount of the focus lens 103 based on the detected defocus amount, and performs defocus driving for continuously driving the focus lens 103 via the focus lens driving unit 105. . The defocus drive is a drive that performs focus detection processing and focus lens control (focus lens drive) in parallel with priority given to speed over accuracy. That is, in the defocus drive, focus detection is performed using an image signal acquired during driving of the focus lens.

  If it is determined in step S404 that the reliability is not greater than or equal to the second reliability threshold, the process proceeds to step S412. In step S412, the AF control unit 2122 calculates the drive amount of the focus lens 103 so as to obtain a highly reliable defocus amount, and performs a search drive for driving the focus lens 103 via the focus lens drive unit 105. I do. The search drive is a drive that determines the drive speed according to the depth of focus without using the calculated defocus amount, and performs focus detection processing and focus lens control in parallel.

  After setting the control state of the focus adjustment operation in steps S409 to S412, the process proceeds to step S413. In step S413, 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 that the focus adjustment operation is not to be ended, the process returns to step S402. On the other hand, when it is determined that the focus adjustment operation is to be ended, the present flow ends. As described above, the camera control unit 212 sets the focus determination condition of the focus adjustment operation in accordance with the characteristics of the focus lens 103 (performs the focus determination based on the control characteristic information of the imaging optical system), thereby improving the accuracy and the accuracy. It is possible to perform an appropriate focus adjustment operation that balances the speed.

  Next, the focus detection process (step S403 in FIG. 4) executed by the AF signal processing unit 204 will be described in detail with reference to FIG. FIG. 5 is a flowchart showing the focus detection processing. Each step in FIG. 5 is mainly executed by the AF signal processing unit 204 based on a command from the camera control unit 212.

  First, in step S501, 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. 6 is an explanatory diagram of the focus detection area 602 on the pixel array 601 of the image sensor 201. The shift areas 603 on both sides of the focus detection area 602 are areas necessary for the correlation calculation. Therefore, an area 604 obtained by combining the focus detection area 602 and the shift area 603 is a pixel area necessary for the correlation calculation. In FIG. 6, p, q, s, and t are the coordinates in the horizontal direction (x-axis direction), respectively, p and q are the x coordinates of the start point and end point of the area 604 (pixel area), and s and t are the coordinates. The x-coordinates of the start point and the end point of the focus detection area 602 are respectively shown.

  FIG. 7 is an explanatory diagram of AF signals (a pair of image signals) acquired from a plurality of pixels included in the focus detection area 602 in FIG. In FIG. 7, a solid line 701 is one of the pair of image signals (A image signal), and a broken line 702 is the other of the pair of image signals (B image signal). FIG. 7A shows the A image signal and the B image signal before the shift, and FIGS. 7B and 7C show the A image signal and the B image signal, respectively, from the state of FIG. This shows a state shifted in the minus direction.

  Subsequently, in step S502 in FIG. 5, the AF signal processing unit 204 relatively shifts the pair of image signals (A image signal, B image signal) acquired in step S501 by one pixel (1 bit). , The amount of correlation (correlation data) between the pair of image signals is calculated. The AF signal processing unit 204 performs an A image signal 701 and a B image signal 702 on each of a plurality of pixel lines (scan lines) provided in the focus detection area as illustrated in FIGS. Are shifted one bit at a time in the direction of the arrow. Further, the AF signal processing unit 204 calculates a correlation amount of a pair of image signals (A image signal 701 and B image signal 702) for each of the plurality of scanning lines, and performs an averaging of the correlation amounts of the plurality of scanning lines. Calculate one correlation amount.

  In the present embodiment, when calculating the correlation amount, the pair of image signals are configured to be relatively shifted by one pixel, but the present invention is not limited to this. For example, a configuration may be adopted in which a pair of image signals are shifted by a larger number of pixels, such as by shifting the image signals relatively by two pixels. In the present embodiment, one correlation amount is calculated by averaging the correlation amounts for each of the plurality of scan lines, but the present invention is not limited to this. For example, an arrangement may be made in which the averaging is performed on a pair of image signals for each of a plurality of scanning lines, and then the correlation amount is calculated for the pair of image signals that are averaged.

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

  In equation (1), i is the shift amount, ps is the maximum shift amount in the minus direction, qt is the maximum shift amount in the plus direction, x is the start coordinate of the focus detection area 702, and y is the coordinate of the focus detection area 702. End coordinates.

  Here, the relationship between the shift amount and the correlation amount COR will be described with reference to FIG. FIGS. 8A and 8B are diagrams illustrating the relationship between the shift amount and the correlation amount COR. FIG. 8B is an enlarged view of a region 802 in FIG. In FIG. 8A, the horizontal axis represents the shift amount, and the vertical axis represents the correlation amount COR. Of the regions 802 and 803 near the extreme value in the correlation amount 801 that changes with the shift amount, the degree of coincidence between the pair of image signals (A image signal and B image signal) is the highest in the shift amount corresponding to the smaller correlation amount. .

  Subsequently, in step S503 of FIG. 5, the AF signal processing unit 204 calculates a correlation change amount based on the correlation amount calculated in step S502. In the present embodiment, the difference between the correlation amounts at every other shift in the waveform of the correlation amount 801 shown in FIG. 8A is calculated as the correlation change amount. The correlation change amount ΔCOR [i] can be calculated using the following equation (2).

  Subsequently, in step S504, the AF signal processing unit 204 calculates an image shift amount using the correlation change amount calculated in step S503. Here, the relationship between the shift amount and the correlation change amount ΔCOR will be described with reference to FIG. FIGS. 9A and 9B are diagrams illustrating the relationship between the shift amount and the correlation change amount ΔCOR. FIG. 9B is an enlarged view of a region 902 in FIG. 9A. In FIG. 9A, the horizontal axis represents the shift amount, and the vertical axis represents the correlation change amount ΔCOR. The correlation change amount 901 that changes with the shift amount changes from plus to minus in the regions 902 and 903. The state where the correlation change amount is 0 is called zero cross, and the degree of coincidence between a pair of image signals (A image signal and B image signal) is the highest. Therefore, the shift amount giving the zero cross is the image shift amount.

  In FIG. 9B, reference numeral 904 denotes a part of the correlation change amount 901. The shift amount (k−1 + α) that gives a zero cross is divided into an integer part β (= k−1) and a decimal part α. The fractional part α can be calculated from the similarity between the triangle ABC and the triangle ADE in FIG. 9B by using the following equation (3).

  The integer part β can be calculated from FIG. 9B using the following equation (4).

  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. 9A, when there are a plurality of zero crosses of the correlation change amount ΔCOR, the one where the steepness of the change of the correlation change amount ΔCOR in the vicinity is larger is defined as the first zero cross. This steepness is an index indicating the ease of performing AF, and indicates that the larger the value, the easier it is to perform high-precision 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 that gives the first zero cross is defined as the image shift amount.

  Subsequently, in step S505 of FIG. 5, the AF signal processing unit 204 calculates reliability (correlation reliability) indicating the high degree of reliability of the image shift amount calculated in step S504. The reliability of the image shift amount can be defined by the degree of coincidence (degree of coincidence between two images) fnclvl of the pair of image signals (A image signal and B image signal) and the steepness of the above-described correlation change amount ΔCOR. . The degree of coincidence between two images is an index indicating the accuracy of the image shift amount. Here, a smaller value means higher accuracy. In FIG. 8B, reference numeral 804 denotes a part of the correlation amount 801. The coincidence fnclvl of the two images can be calculated using the following equation (6).

  Finally, in step S506 in FIG. 5, the AF signal processing unit 204 calculates a defocus amount related to the target focus detection area using the image shift amount calculated in step S604, and executes this flow (focus detection). Processing) ends.

  According to the present embodiment, the minimum drivable amount of the focus lens according to the characteristics (control characteristic information) of each lens is obtained through communication, and the focus determination of the focus detection operation is performed based on the obtained minimum drivable amount. Set conditions. Thereby, it is possible to perform an appropriate focus adjustment operation (focus control) while achieving both accuracy and speed.

(Second embodiment)
Next, a focus adjustment operation (focus control) according to the second embodiment will be described with reference to FIG. FIG. 11 is a flowchart illustrating the procedure of the focus adjustment operation in the present embodiment. Each step in FIG. 11 is executed by the camera control unit 212 (mainly the AF control unit 2122) according to a computer program (imaging processing program).

  Steps S1101 to S1106 in FIG. 11 are the same as steps S401 and S403 to S407 in FIG. 4, respectively. If it is determined in step S1106 that the detected defocus amount is not within the first defocus amount threshold (not in the first focus range), the process advances to step S1107.

  In step S1107, the AF control unit 2122 determines whether the detected defocus amount is within the third defocus amount threshold (whether the detected defocus amount is within the second focusing range). The third defocus amount threshold is larger than the first defocus amount threshold and smaller than the second defocus amount threshold (that is, the second focus range is wider than the first focus range). Here, originally, if the detected defocus amount is not within the first defocus amount threshold value in step S1107, the focusing accuracy required for focusing is not obtained. Focusing is required. However, if the control characteristics of the focus lens 103 of the lens unit 10 mounted on the camera body 20 are not sufficient and the accuracy cannot be expected to be improved even after the subsequent target driving, it is necessary to perform further focusing. Therefore, the determination in step S1107 is performed.

  If it is determined in step S1107 that the detected defocus amount is within the third defocus amount threshold, the process advances to step S1108. In step S1108, the AF control unit 2122 calculates the drive amount of the focus lens 103 based on the detected defocus amount, and performs the target drive for intermittently driving the focus lens 103 via the focus lens drive unit 105 only once. Do.

  If it is determined in step S1108 that the detected defocus amount is within the first defocus amount threshold, or if it is determined in step S1108 that the detected defocus amount is within the third defocus amount threshold, target driving is performed. If completed, the process advances to step S1109. Steps S1109 to S1113 are the same as steps S409 to S413 in FIG. 4, respectively. Note that the present embodiment may further use control characteristic information such as the minimum drivable amount of the focus lens 103 as in the first embodiment.

  According to the present embodiment, the target drive is performed only once after the predetermined condition is satisfied. Thereby, it is possible to perform an appropriate focus adjustment operation (focus control) while achieving both accuracy and speed.

(Third embodiment)
Next, a focus adjustment operation (focus control) according to the third embodiment will be described with reference to FIG. FIG. 12 is a flowchart illustrating the procedure of the focus adjustment operation in the present embodiment. Each step in FIG. 12 is executed by the camera control unit 212 (mainly the AF control unit 2122) according to a computer program (imaging processing program).

  Steps S1201 to S1208 in FIG. 12 are the same as steps S1101 to S1108 in FIG. 11, respectively. In step S1208, the AF control unit 2122 calculates the drive amount of the focus lens 103 based on the detected defocus amount, and performs target drive for intermittently driving the focus lens 103 via the focus lens drive unit 105.

  Subsequently, in step S1209, the AF control unit 2122 determines whether the position (focus position) of the focus lens 103 has changed after the target driving in step S1208. Here, the case where the position of the focus lens 103 does not change after driving the target means the case where the control characteristics of the focus lens 103 are not sufficient and improvement in accuracy cannot be expected even if the subsequent target driving is executed. If it is determined that the position of the focus lens 103 has changed, the process advances to step S1211.

  When it is determined in step S1208 that the detected defocus amount is within the first defocus amount threshold (in the first focusing range), or in step S1209, the position of the focus lens 103 has not changed. If it is determined, the process proceeds to step S1210. Steps S1210 to S1214 are the same as steps S1109 to S1113 in FIG. 11, respectively. Note that the present embodiment may further use control characteristic information such as the minimum drivable amount of the focus lens 103 as in the first embodiment.

  According to the present embodiment, when the predetermined condition is satisfied, the focus determination condition of the focus adjustment operation (focus control) is set according to a change in the position of the focus lens 103 after driving the target. Thus, it is possible to perform an appropriate focus adjustment operation that achieves both accuracy and speed.

  As described above, in each embodiment, the control device includes the calculation unit (AF signal processing unit 204) and the focus adjustment unit (AF control unit 2122). The calculating means calculates a defocus amount based on the first signal and the second signal corresponding to the light beams that have passed through different pupil regions of the lens unit 10. The focus adjustment means performs focus adjustment based on the defocus amount. Further, the focus adjusting means makes a focus determination based on control characteristic information (drive characteristic information) of the lens unit.

  Preferably, the focus adjustment unit changes a condition (focusing determination criterion) for performing the focusing determination based on the control characteristic information. Preferably, the control characteristic information is information on a minimum drivable amount of the focus lens of the lens unit. More preferably, the information on the minimum drivable amount is an image plane movement amount corresponding to the minimum drivable amount. Preferably, the focus adjustment unit performs the focus determination based on the defocus amount and information on the minimum drivable amount. Preferably, when the defocus amount is smaller than the information on the minimum drivable amount, the focus adjustment unit determines that the object is in focus. On the other hand, when the defocus amount is larger than the information on the minimum drivable amount, the focus adjustment unit determines that the object is not in focus.

  Preferably, the control device (imaging device) includes a storage unit (the ROM 210 or the internal memory of the camera control unit 212) that stores control characteristic information regarding each of the plurality of types of lens units. The focus adjustment unit selects control characteristic information from the storage unit based on lens information (such as a lens ID) received from a lens unit mounted on the imaging device (camera body 20). Preferably, the focus adjustment unit receives the control characteristic information from a lens unit mounted on the imaging device. Also preferably, when the state of the imaging device or the lens unit changes, the focus adjustment unit receives the control characteristic information from the lens unit. Preferably, the focus adjustment unit periodically receives control characteristic information from the lens unit.

  In each embodiment, when the defocus amount is within the first focus range (when smaller than the first defocus amount threshold), the focus adjustment unit determines that the object is in focus. On the other hand, if the defocus amount is not in the first focus range and is in the second focus range wider than the first focus range (smaller than the third defocus amount threshold value), After the focus lens is driven based on the amount, it is determined that the camera is in focus. Preferably, the focus adjustment unit determines that the position of the focus lens has changed after driving the focus lens based on the defocus amount when the defocus amount is not in the first focus range and in the second focus range. Then, the driving of the focus lens is continued. On the other hand, when the defocus amount is not in the first focus range and in the second focus range, the focus adjustment unit determines that the position of the focus lens has not changed after driving the focus lens based on the defocus amount. When it is determined, it is determined that the subject is in focus.

(Other embodiments)
The present invention supplies a program for realizing one or more functions of the above-described embodiments to a system or an apparatus via a network or a storage medium, and one or more processors in a computer of the system or the apparatus read and execute the program. It can also be realized by the following processing. Further, it can be realized by a circuit (for example, an 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 that can perform focus adjustment with high speed and high accuracy.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

204 AF signal processing unit (calculation means)
2122 AF control section (focus adjustment means)

Claims (18)

Calculating means for calculating a defocus amount based on a first signal and a second signal corresponding to a light beam having passed through different pupil regions of the lens unit;
Focus adjustment means for performing focus adjustment based on the defocus amount,
The control device according to claim 1, wherein the focus adjustment unit performs a focus determination based on control characteristic information of the lens unit.   The control device according to claim 1, wherein the focus adjustment unit changes a condition for performing the focus determination based on the control characteristic information.   The control device according to claim 1, wherein the control characteristic information is information on a minimum drivable amount of a focus lens of the lens unit.   4. The control device according to claim 3, wherein the information on the minimum drivable amount is an image plane movement amount corresponding to the minimum drivable amount.   5. The control device according to claim 3, wherein the focus adjustment unit performs the focus determination based on the defocus amount and information on the minimum drivable amount. 6. The focus adjustment means,
If the defocus amount is smaller than the information on the minimum drivable amount, it is determined that the in-focus state,
6. The control device according to claim 5, wherein when the defocus amount is larger than the information regarding the minimum drivable amount, it is determined that the object is not in the in-focus state. A storage unit that stores the control characteristic information for each of a plurality of types of lens units;
7. The apparatus according to claim 1, wherein the focus adjustment unit selects the control characteristic information from the storage unit based on lens information received from the lens unit mounted on an imaging device. The control device according to item 1.   The control device according to claim 1, wherein the focus adjustment unit receives the control characteristic information from the lens unit mounted on an imaging device.   The control device according to claim 8, wherein the focus adjustment unit receives the control characteristic information from the lens unit when a state of the imaging device or the lens unit changes.   The control device according to claim 8, wherein the focus adjustment unit periodically receives the control characteristic information from the lens unit. Calculating means for calculating a defocus amount based on a first signal and a second signal corresponding to a light beam having passed through different pupil regions of the lens unit;
Focus adjustment means for performing focus adjustment based on the defocus amount,
The focus adjustment means,
If the defocus amount is within the first focusing range, it is determined that the subject is in focus,
When the defocus amount is not in the first focus range and is in a second focus range wider than the first focus range, the focus is adjusted after driving the focus lens of the lens unit based on the defocus amount. A control device for determining that the camera is in a focus state. The focus adjustment unit may be arranged such that, when the defocus amount is not in the first focus range and is in the second focus range,
When it is determined that the position of the focus lens has changed after driving the focus lens based on the defocus amount, the drive of the focus lens is continued,
12. The control device according to claim 11, wherein when it is determined that the position of the focus lens has not changed after driving the focus lens based on the defocus amount, the focus state is determined. An image sensor that outputs a first signal and a second signal respectively corresponding to light beams passing through different pupil regions of the lens unit;
An imaging device comprising: the control device according to claim 1.   14. The imaging device according to claim 13, wherein the imaging element has a first photoelectric conversion unit and a second photoelectric conversion unit for one microlens, and the microlenses are two-dimensionally arranged. Imaging device. Calculating a defocus amount based on a first signal and a second signal corresponding to a light beam that has passed through different pupil regions of the lens unit;
Performing a focus adjustment based on the defocus amount,
The control method, wherein in the step of performing the focus adjustment, a focus determination is performed based on control characteristic information of the lens unit. Calculating a defocus amount based on a first signal and a second signal corresponding to a light beam that has passed through different pupil regions of the lens unit;
Performing a focus adjustment based on the defocus amount,
In the step of performing the focus adjustment,
If the defocus amount is within the first focusing range, it is determined that the subject is in focus,
When the defocus amount is not in the first focus range and is in a second focus range wider than the first focus range, the focus is adjusted after driving the focus lens of the lens unit based on the defocus amount. A control method characterized by determining that the camera is in a focus state.   A program for causing a computer to execute the control method according to claim 15 or 16.   A storage medium storing the program according to claim 17.