JP2015087704A - Automatic focus adjustment unit, control method of automatic focus adjustment unit, control program of automatic focus adjustment unit, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high-quality focusing control by enabling appropriate determination for restart depending on the condition of an object, when performing AF (Auto Focus) control using an image-plane phase difference detection method.SOLUTION: An automatic focus adjustment unit includes: image capturing means which receives a light flux entering via an image-capturing optical system including a focus lens and performs photo-electric conversion of the light flux; first detection means which detects phase difference between paired image signals generated from light fluxes passing through different regions of an exit pupil region of the image-capturing optical system; second detection means which detects contrast information from signals outputted from the image capturing means; and control means which controls driving of the focusing lens based on at least either of a detection result obtained by the first detection means and a detection result obtained by the second detection means. When the focusing lens is at halt, the control means determines whether the detection result obtained by the first detection means satisfies a predetermined condition for restarting the focusing lens or not, and then modifies the predetermined condition in accordance with the contrast information.

Description

  The present invention relates to an automatic focus adjustment device equipped with a phase difference detection method and a contrast detection method.

  In recent years, an imaging apparatus typified by a single-lens reflex camera has greatly increased the weight for a method (LV shooting) of shooting while viewing an LV (live view) screen. In particular, the demand for moving image shooting is increasing, and in moving image shooting, it is important that shooting can be performed comfortably while looking at the LV screen.

  Various methods have been proposed as an AF (autofocus) method for an imaging apparatus in LV, and a contrast detection method is a main method. In the contrast detection method, a focused state is obtained by searching for a focus lens position where a contrast evaluation value generated from an image pickup signal obtained using an image pickup element is maximized while moving the focus lens.

  However, the contrast detection method cannot easily determine the position and focus direction of the focus lens for focusing on the subject. For this reason, the contrast detection method may behave poorly when it takes time to focus, or when the direction to be focused is wrong or the focus position is passed. In particular, in moving image shooting, since all the focusing operations are recorded, it is not desirable that the behavior be poor.

  Therefore, an AF method has been proposed that can perform focusing with high quality even during LV shooting. One of the methods is an imaging surface phase difference detection method (imaging surface phase difference AF) in which the phase difference detection method is performed on the imaging element surface. In the phase difference detection method, the defocus amount is calculated from the phase difference between a pair of image signals obtained by receiving light beams that have passed through different exit pupil regions in the photographing optical system. Then, the in-focus state is obtained by moving the focus lens by a movement amount corresponding to the defocus amount.

  As one of imaging plane phase difference detection methods, a system using a configuration in which a plurality of photoelectric conversion elements are provided under the same microlens in an imaging pixel of an imaging element has been proposed as in Patent Document 1. In this configuration, light that has passed through different areas of the exit pupil area is received by each of the plurality of photoelectric conversion elements, so that focus detection can be performed simultaneously with imaging. Specifically, phase difference detection AF can be performed by comparing the outputs of a plurality of photoelectric conversion elements. By using the imaging surface phase difference detection method, AF can be performed using the phase difference detection method even in LV shooting, and focusing can be performed at high speed with high quality.

  As one of characteristic controls when shooting moving images, there is control that stops the focus lens after focusing, and drives the lens again (restart) when the scene changes, for example, the subject moves. When focus adjustment is not necessary, unnecessary focusing can be prevented by controlling the focus lens not to be driven. The same applies to the case where AF control is performed by the phase difference detection method.

  FIG. 8 shows a shooting scene in which people, trees, and mountains are included as subjects. The subject indicated by a solid line is in focus, and the subject indicated by a broken line is in focus. . If the subject is out of focus on the entire screen as shown in the left diagram of FIG. 8A, it is desirable to immediately focus on the subject (person, tree) as shown in the right diagram. On the other hand, as shown in the left figure of FIG. 8B, if the subject (people, trees) is already in focus, restart is not performed unless the scene changes as shown in the right figure. Control in which the focus lens is stopped is desirable.

  Japanese Patent Laid-Open No. 2004-228561 performs a restart determination from when the focus lens is stopped based on distance measurement information of a phase difference detection method by an external sensor, focus detection information of a contrast detection method, and waveform information of a phase difference detection method. A method has been proposed.

JP 2001-083407 A JP 2012-128316 A

  In Patent Document 2, if the AF evaluation value fluctuates at a timing when the AF evaluation value fluctuates, such as when another subject enters the AF evaluation value detection range, immediately after the distance measurement result by the phase difference detection method exceeds the determination threshold value, Will cause the focus lens to restart. Therefore, there is a possibility that the focus lens is unnecessarily restarted and the focus is blurred even though the main subject is in focus at the current focus position. Also, when the AF evaluation value hardly fluctuates, such as in the case of low illuminance, there is a possibility that the restart will not be performed even if the scene changes according to the determination method of Patent Document 2.

  In view of the above problems, the present invention enables high-quality focusing control by enabling appropriate restart determination according to the state of a subject when performing AF control using an imaging surface phase difference detection method. It aims at realizing.

  In order to achieve the above object, the first aspect of the present invention differs from an imaging means for receiving and photoelectrically converting a light beam incident through a photographing optical system including a focus lens, and an exit pupil region of the photographing optical system. A first detection unit that detects a phase difference between a pair of image signals generated from a light beam that has passed through a region; a second detection unit that detects contrast information from a signal output from the imaging unit; And a control means for controlling the drive of the focus lens based on the detection result of at least one of the detection means and the second detection means, wherein the focus lens is stopped The control means determines whether the detection result by the first detection means satisfies a predetermined condition for restarting the focus lens, and the contrast And changes the predetermined condition according to the information.

  A second aspect of the present invention is a control method for an automatic focus adjustment apparatus having an imaging means for receiving and photoelectrically converting a light beam incident through a photographing optical system including a focus lens, the exit pupil of the photographing optical system. A first detection step for detecting a phase difference between a pair of image signals generated from light beams that have passed through different regions; a second detection step for detecting contrast information from a signal output from the imaging means; A control step for controlling driving of the focus lens based on a detection result of at least one of the first detection step and the second detection step, and in a state where the focus lens is stopped, In the control step, it is determined whether the detection result by the first detection means satisfies a predetermined condition for restarting the focus lens, And changes the predetermined condition in response to the serial contrast information.

  According to the present invention, when performing AF control using the imaging surface phase difference detection method, it is possible to make an appropriate restart determination according to the state of the subject, and it is possible to realize focusing control with high quality.

The block diagram which shows the structure of the camera and lens unit in this embodiment. The figure which shows the pixel structure of the imaging surface phase difference system in this embodiment. Flow chart showing imaging processing in the present embodiment Flowchart showing moving image shooting processing in the present embodiment Flowchart showing focus detection processing in this embodiment Flowchart showing AF restart determination processing in the first embodiment Flowchart showing AF processing in the present embodiment The figure for demonstrating the subject of the restart determination in this embodiment The figure which shows the restart conditions in 1st embodiment Flowchart showing AF restart determination processing in the second embodiment Flowchart showing AF restart threshold setting processing in the first embodiment Flowchart showing AF restart threshold value adjustment processing in the present embodiment The figure which shows the ranging area in this embodiment The figure which shows the image signal obtained from the ranging area in this embodiment The figure which shows the correlation amount waveform and correlation variation | change_quantity waveform in this embodiment Flowchart showing AF restart threshold setting processing in the second embodiment The figure which shows the restart condition in 2nd embodiment Flowchart showing AF restart determination processing in the third embodiment

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiment described below is an example as means for realizing the present invention, and the present invention is not limited to the following embodiment.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a lens interchangeable camera including a lens unit and a camera body in the present embodiment. As shown in FIG. 1, the camera system according to this embodiment includes a lens unit 10 and a camera body 20. The lens control unit 106 that controls the overall operation of the lens unit and the camera control unit 212 that controls the overall operation of the camera communicate data.

  First, the configuration of the lens unit 10 will be described. The lens unit 10 includes a photographing optical system that includes a fixed lens 101, a diaphragm 102, and a focus lens 103. 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 performs focus adjustment.

  The aperture driving unit 104 and the focus lens driving unit 105 are controlled by the lens control unit 106, and the aperture amount of the aperture 102 and the position of the focus lens 103 are determined. When an operation such as focusing is performed by the user via the lens operation unit 107, the lens control unit 106 performs control according to the user operation. The lens control unit 106 controls the aperture driving unit 104 and the focus lens driving unit 105 in accordance with a control command / control information received from the camera control unit 212 described later, and transmits lens information to the camera control unit 212. .

  Next, the configuration of the camera body 20 including the automatic focus adjustment device according to the present embodiment will be described. The camera body 20 is configured to be able to acquire an imaging signal from a light beam that has passed through the imaging optical system of the lens unit 10. The image sensor 201 is configured by a CCD or CMOS sensor. The light beam that has passed through the photographing optical system forms an image on the light receiving surface of the image sensor 201, and the formed subject image is converted (photoelectric conversion) into charges corresponding to the amount of incident light by the photodiode. The electric charge accumulated in each photodiode is sequentially read out from the image sensor 201 as a voltage signal corresponding to the electric charge based on a driving pulse given from the timing generator 215 in accordance with an instruction from the camera control unit 212.

  In the case of an imaging device that does not support imaging surface phase difference type focus adjustment (hereinafter referred to as imaging surface phase difference AF), for example, the pixel configuration has a Bayer array as shown in FIG. On the other hand, in order to perform imaging surface phase difference AF, the image sensor 201 of the present embodiment has a plurality of (two in this embodiment) photodiodes (photoelectric conversion elements) in one pixel as shown in FIG. ). That is, a plurality of photodiodes are provided under one microlens. Two signals for imaging and AF can be acquired by separating the luminous flux with a microlens and forming an image of light passing through different areas of the exit pupil area with two photodiodes. A signal (A + B) obtained by adding the signals of two photodiodes is an image pickup signal, and signals (A, B) of individual photodiodes are two image signals for AF. Here, the configuration is not limited to reading each of the two image signals. For example, in consideration of a processing load, the added signal (A + B) and one image signal (for example, A) are read, and the other image signal is calculated from the difference. (For example, B) may be acquired. An AF signal processing unit 204 (to be described later) performs a correlation operation on the two image signals to calculate an image shift amount and various types of reliability information.

  In the present embodiment, the configuration of the imaging device having two photodiodes in one pixel is used, but the number of photodiodes is not limited to two and may be more. In addition, the configuration of the imaging device corresponding to the imaging surface phase difference AF is not limited to the configuration in which a plurality of photodiodes are provided in one pixel as in the present embodiment, but is a configuration in which pixels for focus detection are provided in the imaging device. May be.

  The imaging signal and AF signal read from the imaging element 201 are input to the CDS / AGC / AD converter 202, and correlated double sampling for removing reset noise, gain adjustment, and signal digitization are performed. The CDS / AGC / AD converter 202 outputs an imaging signal to the image input controller 203 and the AF evaluation value generation unit 216, and outputs an imaging surface phase difference AF signal to 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. The imaging signal stored in the SDRAM 209 is displayed on the display unit 206 by the display control unit 205 via the bus 21. In the mode for recording the imaging signal, the recording medium control unit 207 records the image on the recording medium 208.

  The ROM 210 connected via the bus 21 stores a control program executed by the camera control unit 212 and various data necessary for control. The flash ROM 211 stores various setting information relating to the operation of the camera body 20 such as user setting information.

  The AF signal processing unit 204 performs a correlation operation based on the two image signals for AF output from the CDS / AGC / AD converter 202, and calculates image shift amount and reliability information (two-image coincidence degree, two-image steepness degree). , Contrast information, saturation information, scratch information, etc.). Then, the calculated image shift amount and reliability information are output to the camera control unit 212. In addition, the camera control unit 212 notifies the AF signal processing unit 204 of changes in settings for calculating these based on the acquired image shift amount and reliability information. For example, when the image shift amount is large, a region for performing the correlation calculation is set wide, or the type of the band pass filter is changed according to the contrast information. Details of the correlation calculation will be described later with reference to FIGS.

  Further, the AF evaluation value generation unit 216 extracts a high frequency component from the imaging signal output from the CDS / AGC / AD converter 202 to generate an AF evaluation value signal, and outputs the AF evaluation value signal to the camera control unit 212. The AF evaluation value signal represents the sharpness (contrast state) of an image generated based on the output signal from the image sensor 201, and the sharpness changes depending on the focus state (degree of focusing) of the photographing optical system. As a result, the signal represents the focus state of the photographing optical system. Note that the area on the image sensor 201 used for generating the AF evaluation value includes an area corresponding to an area used for generating an image signal for phase difference detection.

  The camera control unit 212 performs control by exchanging information with each configuration in the camera body 20. In response to input from the camera operation unit 214, the user has performed operations such as power ON / OFF, setting change, start of recording, start of AF control, confirmation of recorded image, etc. Perform camera functions. In addition, as described above, information is exchanged with the lens control unit 106 in the lens unit 10, and a control command / control information for the photographing optical system is transmitted, or information in the lens unit is acquired. Further, as a characteristic part of the present embodiment, the camera control unit 212 sets a threshold value for restart determination used in a lens restart determination unit 213 described later. Details will be described later.

  A lens restart determination unit 213 in the camera control unit 212 determines whether to drive (restart) the focus lens 103 again from a stopped state. When the camera control unit 212 determines that the subject is in focus, the driving of the focus lens 103 is stopped via the lens control unit 106 and the focus lens driving unit 105 in the lens unit 10. Thereafter, based on information from the AF signal processing unit 204, the lens restart determination unit 213 determines whether to drive the focus lens 103 again. When the lens restart determination unit 213 determines to restart the focus lens 103, the driving of the focus lens 103 is resumed via the lens control unit 106 and the focus lens driving unit 105 in the lens unit 10.

  Although AF control is required to focus quickly when shooting a still image, the quality of the focusing operation is important because when the moving image is shot, the appearance itself of the image by the focusing operation is recorded. As one of the controls for improving the quality, the focus lens is not always driven, but the focus lens is stopped when the subject is in focus, and then the focus lens is driven until it is determined that the subject has changed or is out of focus. Is controlled not to resume. When the focus lens is continuously driven without being stopped, there are the following problems. For example, if you inadvertently measure a subject with poor ranging accuracy, such as a low-contrast part, or if a crossing of a subject other than the intended subject occurs, carelessly focusing and blurring may occur. Deteriorating the quality. Therefore, during movie shooting, when it is determined that the subject is in focus, the focus lens is stopped once, and it is determined whether the subject has changed, and control is performed so that focusing is resumed. Can improve the quality.

  As described above, when restarting the drive from the stop state of the focus lens, control is performed so that the subject situation (in-focus state) can be definitely determined to be restarted to prevent inadvertent focusing. It is desirable to do. For example, if the defocus amount is within the depth, restarting is not performed, and if the defocus amount outside the depth is detected for a certain time, restarting is performed, it can be determined that the in-focus state has changed.

  However, there are shooting scenes in which focusing is not desired because the focus state has changed. For example, when the subject temporarily comes out of the distance measurement area and returns again, it is desirable not to restart the subject because it is desired to maintain the focus on the subject that was in focus. On the other hand, when the scene changes due to panning or the like from the state in which the focus lens is stopped, it is desirable to restart as soon as possible in order to follow the focus while reducing the blurring period as much as possible.

  In this embodiment, when restarting from the stopped state of the focus lens, the camera control unit 212 (lens restart determination unit 213) captures the main subject based on the detected AF evaluation value signal and the defocus amount. Determine if the main subject or scene has changed. In the former case, control is performed so as to limit the restart in order to keep the focus lens stopped as much as possible, and in the latter case, control is performed so that the restart is performed quickly in order to follow the focus. Even in the former case, since the situation of the main subject may change, control is performed so that the restart is performed. Details of processing related to the restart determination will be described later with reference to FIGS. 10 to 12.

  Next, the operation of the camera body 20 in the present embodiment will be described with reference to the drawings. FIG. 3 is a flowchart showing the procedure of the photographing process of the camera body 20.

  First, in steps S301 to S303, the camera control unit 212 performs an initialization process. In step S301, the camera control unit 212 sets various initial values of the camera. Here, when the shooting process is started or when the shooting mode is changed, the initial value is set based on information such as the user setting and the shooting mode at that time. In step S302, the focus stop flag is turned off. In step S303, the search drive flag is turned off and the process ends.

  The focus stop flag that is initialized in step S302 is turned on when the focus lens 103 is stopped because it is determined that the camera is in focus during moving image shooting, and the focus lens 103 is driven without focus. Turn off if it is in a state. By switching on / off of the focus stop flag, it is determined whether the focus lens 103 is currently driven or stopped.

  The search drive flag to be initialized in step S303 is turned off when the defocus amount detected by the imaging surface phase difference detection method is reliable when driving the focus lens 103, and turned on when the focus lens 103 is not reliable. The case where the defocus amount is reliable is a case where the accuracy of the defocus amount and the defocus direction are certain, that is, a state where the reliability is higher than a certain level. When the search drive flag is turned on, search drive for searching for the in-focus position by driving the focus lens 103 in a certain direction without using the defocus amount is performed.

  In step S304, it is determined whether the shooting setting of the camera is the moving image shooting mode or the still image shooting mode. If it is in the moving image shooting mode, the process proceeds to step S305. If it is in the still image shooting mode, the process proceeds to step S306. In step S305, a moving image shooting process is performed, and the process proceeds to step S307. Details of the moving image shooting processing in step S305 will be described later with reference to FIG. On the other hand, in step S306, a still image shooting process is performed and the process proceeds to step S307. Details of the still image shooting process in step S306 are omitted.

  In step S307, it is determined whether the shooting process has been stopped. If the shooting process has not been stopped, the process proceeds to step S308. If the shooting process has not been stopped, the shooting process is terminated. The shooting process is stopped when the camera is turned off, or when an operation other than shooting is performed, such as user setting processing for the camera, playback processing for checking captured images / movies, etc. .

  In step S308, it is determined whether or not the shooting mode has been changed. If changed, the process returns to step S301, and if not changed, the process returns to step S304. If the shooting mode has not been changed, the processing of the current shooting mode is continued. If the shooting mode has been changed, initialization processing is performed in steps S301 to S303 and then the changed shooting mode is processed. .

  Next, the moving image shooting process in step S305 in FIG. 3 will be described with reference to FIG. In steps S401 to S404, control relating to moving image recording is performed.

  In step S401, the camera control unit 212 determines whether the moving image recording switch is turned on. If it is turned on, the process proceeds to step S402. If it is not turned on, the process proceeds to step S405.

  In step S402, the camera control unit 212 determines whether a moving image is currently being recorded. If the moving image is not being recorded, the process proceeds to step S403, where the moving image recording is started and the process proceeds to step S405. On the other hand, if the moving image is being recorded, the process proceeds to step S404, where the moving image recording is stopped and the process proceeds to step S405. In this embodiment, the moving image recording is started / stopped by pressing the moving image recording switch. However, the recording start / stop may be performed by another method such as a changeover switch.

  In step S405, focus detection processing is performed. Here, it is a process of acquiring defocus information and reliability information for performing imaging plane phase difference AF performed by the camera control unit 212 and the AF signal processing unit 204 of FIG. Details will be described later with reference to FIG.

  In step S406, sharpness information is acquired. Here, the AF evaluation value generation unit 216 is processing for acquiring sharpness information (AF evaluation value) from the imaging signal of the set distance measurement area. Since this process is a conventional technique, details are omitted.

  In step S407, the camera control unit 212 determines whether the focus is currently stopped. When the in-focus state is not stopped, the process proceeds to step S408, and when the in-focus state is stopped, the process proceeds to step S409. Whether or not the focus is stopped is determined by turning on / off the focus stop flag described above. In step S408, AF processing is performed, and the moving image shooting processing ends. Step S408 performs AF control based on the information detected in steps S405 and S406, and details will be described later with reference to FIG.

  In step S409, AF restart determination is performed, and the moving image shooting process ends. Step S409 is processing for determining whether or not AF control is to be started again if the subject has changed since the in-focus state was stopped. Details will be described later with reference to FIG.

  Next, the focus detection process in step S405 in FIG. 4 will be described with reference to FIG. First, in step S501, the camera control unit 212 acquires a pair of image signals from an arbitrarily set ranging range. Next, in step S502, the camera control unit 212 calculates a correlation amount from the pair of image signals acquired in step S501.

  Subsequently, in step S503, the camera control unit 212 calculates a correlation change amount from the correlation amount calculated in step S502. In step S504, the camera control unit 212 calculates a focus deviation amount from the correlation change amount calculated in step S503.

  In step S505, the camera control unit 212 calculates reliability indicating how reliable the amount of focus deviation calculated in step S504 is. These processes are performed for the number of distance measurement areas existing in the distance measurement range. In step S506, the camera control unit 212 converts the focus shift amount into the defocus amount for each distance measurement area. Finally, in step S507, the distance measurement area used for AF is determined, and the focus detection process is terminated.

  Next, the focus detection process described in FIG. 5 will be described in detail with reference to FIGS. FIG. 13 is a diagram illustrating an example of a region for acquiring an image signal indicating a range of measurement handled in the focus detection process. FIG. 13A is a diagram showing a distance measurement range 1302 on the pixel array 1301. An area 1304 necessary for performing the correlation calculation is an area obtained by combining the distance measurement range 1302 and the shift area 1303 required for the correlation calculation. In FIG. 13A, p, q, s, and t represent coordinates in the x-axis direction, respectively. Here, p to q represent the region 1304, and s to t represent the distance measurement range 1302.

  FIG. 13B is a diagram illustrating distance measurement areas 1305 to 1309 obtained by dividing the distance measurement range 1302 into five. As an example, in this embodiment, a focus shift amount is calculated for each distance measurement area unit, and focus detection is performed. Further, the distance measurement result of the most reliable area is selected from the plurality of divided distance measurement areas, and the focus shift amount calculated in the area is used for AF. Note that the number of divisions of the distance measurement range is not limited to the above.

  FIG. 13C is a diagram showing a temporary ranging area 1310 obtained by connecting the ranging areas 1305 to 1309 in FIG. 13B. As an example of the embodiment, a focus shift amount calculated from an area obtained by connecting the distance measurement areas as described above may be used for AF. The arrangement method, size, and the like of the distance measurement areas are not limited to those described in the present embodiment, and may be in a form that does not depart from the gist of the invention.

  FIG. 14 is a diagram showing an image signal acquired from the ranging area set in FIG. From s to t represents a distance measurement range, and from p to q represents a range necessary for distance measurement calculation based on the shift amount. Further, x to y represent one divided distance measuring area.

  FIG. 14A is a diagram showing a waveform of the image signal before the shift. A solid line 1401 indicates the image signal A, and a broken line 1402 indicates the image signal B. Areas 1305 to 1309 represent the distance measurement areas divided in FIG.

  FIG. 14B is a diagram in which the image waveform before the shift in FIG. 14A is shifted in the positive direction, and FIG. 14C is a minus with respect to the image waveform before the shift in FIG. It is the figure shifted to the direction. When calculating the correlation amount, the image signal A1401 and the image signal B1402 are shifted bit by bit in the directions of the arrows, respectively.

  Next, a method for calculating the correlation amount COR will be described. First, as described in FIGS. 14B and 14C, the image signal A and the image signal B are shifted bit by bit, and the sum of the absolute values of the differences between the image signal A and the image signal B at that time is calculated. calculate. Here, the shift amount is represented by i, the minimum shift number is ps in FIG. 14, and the maximum shift number is qt in FIG. Further, x is the start coordinate of the distance measurement area, and y is the end coordinate of the distance measurement area. Using these, the correlation amount COR can be calculated by the following equation (1).

  FIG. 15A is a diagram showing the correlation amount as a waveform. The horizontal axis of the graph indicates the shift amount, and the vertical axis indicates the correlation amount. In the correlation amount waveform 1501, 1502 and 1503 indicate the vicinity of the extreme value. Among these, the smaller the correlation amount, the higher the coincidence between the A image and the B image.

  Next, a method for calculating the correlation change amount ΔCOR will be described. First, the correlation change amount is calculated from the correlation amount difference of one shift skip from the correlation amount waveform of FIG. At this time, the shift amount is represented by i, the minimum shift number is ps in FIG. 14, and the maximum shift number is qt in FIG. Using these, the correlation change amount ΔCOR can be calculated by the following equation (2).

  FIG. 15B is a diagram showing the correlation change amount ΔCOR as a waveform. The horizontal axis of the graph indicates the shift amount, and the vertical axis indicates the correlation change amount. In the correlation change amount waveform 1504, reference numerals 1505 and 1506 indicate the vicinity where the correlation change amount becomes positive to negative. When the correlation change amount becomes 0 from 1505, this is called zero crossing, and the degree of coincidence between the A image and the B image is the highest, and the shift amount at that time is the focus shift amount.

  FIG. 15C is an enlarged view of the portion 1505 in FIG. 15B, and 1507 is a portion of the correlation variation waveform 1504. A method of calculating the focus shift amount PRD will be described with reference to FIG. First, the focus shift amount is divided into an integer part β and a decimal part α. The decimal part α can be calculated by the following equation (3) from the similar relationship between the triangle ABC and the triangle ADE in FIG.

  Subsequently, the decimal part β can be calculated by the following equation (4) from FIG.

  As described above, the focus shift amount PRD can be calculated from the sum of α and β.

  When there are a plurality of zero crosses as shown in FIG. 15B, the first zero cross is defined as a point where the steepness maxder (hereinafter referred to as steepness) of the correlation amount change at the zero cross is large. This steepness is an index indicating the ease of AF. The larger the value, the easier it is to perform AF. The steepness can be calculated by the following equation (5).

  As described above, when there are a plurality of zero crosses, the first zero cross is determined based on steepness.

  Next, a method for calculating the reliability of the focus deviation amount will be described. Reliability can be defined by the steepness and the degree of coincidence fnclvl (hereinafter referred to as the degree of coincidence of two images) of the two images of the image signals A and B. The degree of coincidence between the two images is an index representing the accuracy of the amount of focus deviation.

  FIG. 15D is an enlarged view of the portion 1502 in FIG. 15A, and 1508 is a portion of the correlation amount waveform 1501. The degree of coincidence between two images can be calculated by the following equation (6).

  Next, the AF process in step S408 of FIG. 4 will be described using the flowchart of FIG. The AF processing is processing for driving the focus lens in a state where focusing is not stopped and for determining whether focusing is stopped.

  In step S701, the camera control unit 212 determines whether the defocus amount is within the depth and the reliability calculated in step S505 in FIG. 5 shows a value better than a predetermined level. If this condition is met, the process proceeds to step S702; otherwise, the process proceeds to step S703. In the present embodiment, the threshold used in step S701 is set to be 1 time the depth, but may be set larger or smaller as necessary.

  In step S702, the focus stop flag is turned on and the process ends. As described above, when it is determined that the subject is in focus, the process proceeds from the state in which the focus lens is driven to the stop state, and then whether or not the focus lens is to be driven again is determined in step S409 in FIG. Perform a restart judgment with. On the other hand, in step S703, the camera control unit 212 determines the lens driving speed and driving method, performs lens driving processing, and ends the processing.

  Next, the AF restart determination process in step S409 of FIG. 4 will be described using the flowchart of FIG. The AF restart determination process is a process for determining whether to drive the focus lens again from a state where the focus lens is stopped after focusing. The processing of this flow is executed by the camera control unit 212 (lens restart determination unit 213) unless otherwise specified.

  First, in step S601, the camera control unit 212 determines whether or not the reliability calculated in step S505 in FIG. 5 is better than a predetermined threshold (predetermined level). If the value is good, the process proceeds to step S602. If the value is bad, the process proceeds to step S604.

  In step S602, the camera control unit 212 determines whether the calculated defocus amount is smaller than a predetermined multiple of the depth. If it is smaller than the predetermined multiple of the depth, the process proceeds to step S603, and if not, the process proceeds to step S608. In step S603, the AF restart counters a and b are reset, and the process ends.

  On the other hand, when the process proceeds to step S604, the camera control unit 212 resets the AF restart counter a. In step S605, the camera control unit 212 determines whether the focusing direction based on the phase difference detection result is the same as the previous direction. If the directions are the same, the process proceeds to step S606, the AF restart counter b is added, and the process proceeds to step S610. If they are not in the same direction, the process proceeds to step S607, where the AF restart counter b is reset, and the process ends. Here, the AF restart counter b indicates the number of times the same in-focus direction is detected when the reliability is poor (only the detected direction can be used).

  On the other hand, in step S608, it is determined whether the focusing direction based on the phase difference detection result is the same as the previous direction. If the directions are the same, the process proceeds to step S609. If the directions are not the same, the process proceeds to step S613.

  In step S613, the camera control unit 212 resets the AF restart counter b. In step S609, the AF restart counter a is added, and the process proceeds to step S610. Here, the AF restart counter a indicates the number of times that a defocus amount equal to or larger than a predetermined value (a predetermined multiple of the depth) is detected.

  As described above, when the defocus amount is larger than the predetermined value or when the same in-focus direction is continuously detected, there is a possibility that the situation of the main subject has changed. Therefore, in step S606 or step S609, an AF restart counter is added to prepare for restarting AF. If the detected defocus amount is smaller than the predetermined value and the reliability of the phase difference detection result is maintained high, the AF restart counter is reset in step S603 to keep the focus lens stopped. .

  Here, as the reliability threshold value set in step S601, for example, a value with which the distance calculated from the phase difference detection result can be trusted is set. If the reliability is worse than the predetermined threshold value in step S601, the distance calculated from the defocus amount is not reliable, and only the in-focus direction can be used. Further, the defocus amount threshold value set in step S602 is tuned in consideration of the fact that it is easy to restart when the main subject changes, and that the restart is not easily inadvertent when the main subject has not changed. . As an example, 1 time is set to a depth at which the blur of the main subject becomes visible.

  Next, in step S610, the camera control unit 212 sets an AF restart threshold. The AF restart threshold setting process in step S610 is a characteristic part of the present embodiment, and a threshold for performing AF restart determination using an AF restart counter in step S611 described later is set. Details of the AF restart threshold setting process will be described later with reference to the flowchart of FIG.

  In step S611, the camera control unit 212 determines whether the AF restart counter a or b is greater than or equal to the AF restart threshold. If it is greater than or equal to the AF restart threshold, the process proceeds to step S612. If it is less than the AF restart threshold, the process ends. In step S612, the focus stop flag is turned off, AF restart is performed, and the processing is ended so as to resume focus lens driving.

  In step S611 described above, it is determined whether the AF restart counter added in step S606 or S609 is larger than the threshold set in step S610 when restarting AF. In this way, control is performed so as to confirm whether or not the focus surface of the main subject has changed for a certain period of time. In this embodiment, the AF restart threshold set in step S610 is changed according to the degree of focus, thereby changing the conditions for determining restart. As a result, when it can be determined that the focus surface of the main subject has changed, control is performed so as to quickly restart and follow the focus. On the other hand, when the focus surface has not changed (maintained in focus), control is performed so as to limit the restart, thereby preventing inadvertent focusing and poor-quality behavior. .

  Next, the AF restart threshold value setting process in step S610 in FIG. 6 will be described with reference to FIG. In step S1101, it is determined whether the degree of focus based on the result acquired in step S406 in FIG. 4 is higher than the threshold value TH1. If it is higher than TH1, the process proceeds to step S1103. Otherwise, the process proceeds to step S1102.

  Next, in step S1102, it is determined whether or not the above-described degree of focus is higher than a threshold value TH2 (<TH1). If it is higher than TH2, the process proceeds to step S1104; otherwise, the process proceeds to step S1105.

  As an example of the degree of focus, in the present embodiment, the AF evaluation value (TEP) generated by extracting a specific frequency component from the imaging signal is simply calculated by normalizing with the contrast value (MMP). Use the degree of focus. The lower the simple focus degree, the higher the possibility that the position of the focus lens is away from the focus position. The higher the simple focus degree, the higher the possibility that the focus lens is closer to the focus position. Note that the determination of the degree of focus is not limited to the above-described simple focus degree, and may be determined using an evaluation value calculated by another method.

In steps S1103 to S1105, as shown in FIG. 11, AF restart thresholds X1, Y1, Z1, X2, Y2, and Z2 are set. Here, the AF restart thresholds X1, Y1, and Z1 are used for the determination of the AF restart counter a described above, and the AF restart thresholds X2, Y2, and Z2 are used for the determination of the AF restart counter b described above. . The AF restart threshold has the following relationship.
X1>Y1> Z1
X2>Y2> Z2
X1 <X2, Y1 <Y2, Z1 <Z2

  If a defocus amount larger than a predetermined multiple of the depth is detected in the focused state, the output defocus amount is monitored for a predetermined period without driving the focus lens immediately. Thus, AF malfunction can be reduced. On the other hand, when a defocus amount larger than a predetermined multiple of the depth is detected in the blurred state, the focus lens can be quickly driven to focus.

  In step S1106, a process for adjusting the set AF restart threshold value is performed, and the process of this flow ends. Details of the AF restart threshold value adjustment process in step S1106 will be described later with reference to FIG.

  As described above, in AF control during movie shooting, after focusing on the subject and stopping the focus lens, if it is determined that there is a subject change (scene change), the focus lens can be restarted quickly. , Focusing with less discomfort can be performed. On the other hand, when it is determined that there is no subject change (scene change), it is possible to shoot a scene with less discomfort by stopping the focus lens.

  An example of a specific operation will be described with reference to FIG. When the reliability of the detected defocus amount is better than the predetermined value, that is, the distance measurement result can be used as a result of the determination in step S601 in FIG. 6, the camera control unit 212 determines that the defocus amount is “depth” shown in FIG. Determine whether it is “inside” or “outside of depth”. If it is in the “in-depth” region, control is performed so that the focus lens continues to be stopped without being driven. This corresponds to the case of Yes in step S602 in FIG.

  If the detected defocus amount is “out of depth”, the restart condition is set according to the degree of focus described above. In FIG. 9B, the restart threshold value corresponding to the degree of focus is shown in a table. If it is determined in the table of FIG. 9B that “in-focus”, the camera control unit 212 determines that the defocus amount of “out of depth” is X1 = 10 times or more by the focus detection processing in step S404 of FIG. When it is output, the focus lens is restarted using the output defocus amount. In a state where the subject is in focus, an unnecessary restart is prevented by setting a large threshold value (10 times). Therefore, stable focus control can be performed even when the defocus amount becomes “out of depth” due to variations in the defocus result and the subject temporarily entering and exiting the distance measurement area.

  Next, when it is determined that the degree of focus is “small blur”, the camera control unit 212 outputs the defocus amount “out of depth” Y1 = 5 times or more by the focus detection process in step S404 of FIG. Then, the focus lens is restarted using the output defocus amount. If it is determined that the in-focus level is “large blur”, the camera control unit 212 outputs the “out-of-depth” defocus amount Z1 = 3 times or more by the focus detection process in step S404 of FIG. , Restart the focus lens using the output defocus amount.

As described above, when the degree of focusing is low, the focus lens is promptly restarted by setting the threshold value small. Therefore, even if the subject or scene changes due to panning or a new subject comes out of the screen, the focus lens can be restarted immediately, so focus driving with good responsiveness can be performed. it can.
Note that the defocus amount used when restarting in the above example may be a value output when the restart condition is satisfied, or a method using an average of past defocus amounts.

  In the case where the reliability of the detected defocus amount is worse than a predetermined value based on the determination of step S601 in FIG. Set the restart conditions according to the degree. However, when the reliability is lower than a predetermined value, the restart condition is made stricter by using the phase difference AF result, that is, the restart threshold value is set larger than when the reliability is good.

  In the table of FIG. 9B, when only the direction is available and it is determined that “focusing” is set, the camera control unit 212 determines that the same direction is X2 = by the focus detection processing in step S404 of FIG. If it is output more than 12 times, the focus lens is restarted in the output direction. Next, when it is determined that the in-focus state is “small blur”, the camera control unit 212 outputs the same direction when Y2 = 8 times or more is output by the focus detection process in step S404 of FIG. Restart the focus lens in the direction. If it is determined that the in-focus state is “large blur”, the camera control unit 212 outputs the output direction when the same direction is output Z2 = 4 times or more by the focus detection process in step S404 of FIG. Restart the focus lens.

  The restart threshold value is determined empirically, but is not limited to the above value as long as the relationship of X1> Y1> Z1 and X2> Y2> Z2 holds.

  As described above, in the present embodiment, the condition for restarting the focus lens is changed according to the degree of focus. If the degree of focus is high, the restart threshold is set large. This allows unnecessary restart even if a defocus amount exceeding the depth is detected, such as when the subject temporarily leaves the distance measurement area and returns again, or when the subject is blurred or blurred for a moment. Can be prevented. Therefore, stable focus control can be performed even when a subject moves on the screen or another subject temporarily enters the frame, or when another subject passes in front of the subject. In the present embodiment, increasing the restart threshold can be said to increase the period until restart.

  When the degree of focus is low, the restart threshold is decreased. As a result, when it is almost clear that the entire screen is out of focus and the subject is not in focus, it is possible to restart quickly. Therefore, when the subject is out of frame or the scene is changed by panning or the like, focus control can be performed immediately. In the present embodiment, reducing the restart threshold can be said to shorten the period until restart.

  Next, the AF restart threshold adjustment processing in step S1106 in FIG. 11 will be described using the flowchart in FIG. In step S1201, it is determined whether the image height of the distance measurement area set in step S507 in FIG. 5 is higher than a predetermined value. If it is higher than the predetermined value, the process proceeds to step S1202, and if not, the process proceeds to step S1203.

  In step S1202, it is determined from the acquired aperture value whether the aperture is smaller than the predetermined aperture (the aperture is small). If it is on the small aperture side, the process proceeds to step S1203, and if not, the process ends. In step S1203, a gain is applied so that the AF restart threshold set in steps S1103 to S1105 in FIG. 11 is increased, and the process is terminated.

  The imaging plane phase difference detection method generally has a characteristic that the higher the image height, the greater the difference in the amount of light that enters the pupils A and B that acquire the image signals A and B, and the pupil intensity varies depending on the position in the pupil. . For this reason, the level difference between the image signals A and B appears remarkably at a position where the image height is high, and the image coincidence between the image signals A and B is lowered, so that the defocus detection accuracy is lowered.

  Further, the imaging surface phase difference detection method has a characteristic that a conversion coefficient for converting the image shift amount of the image signals A and B into a defocus amount increases in conjunction with the aperture value. This is because the base line length for imaging the image signals A and B becomes shorter as the aperture is reduced. Therefore, since the conversion coefficient becomes enormous in the narrowed state, a slight image shift amount is converted into a large defocus amount, and the defocus accuracy is deteriorated.

  As described above, (1) when the image height of the distance measurement area is high, and (2) when the aperture is on the small aperture side, the defocus detection accuracy decreases, and the variation in the detected defocus amount increases. End up. Under such conditions, there are many opportunities to detect the defocus amount outside the depth, and therefore, for example, the AF restart determination may be unexpectedly performed although the in-focus state is in focus. Therefore, there is a problem that the quality of AF control is deteriorated due to inadequate focusing.

  Thus, under the conditions described above, the gain determination is performed so that the AF restart threshold value is increased, thereby making it difficult for the restart determination to be performed. As a result, unnecessary focusing operation due to unexpected AF restart determination can be suppressed, and the quality of AF control can be improved.

  In this embodiment, the AF restart threshold is changed depending on the aperture value. However, in principle, the conversion coefficient for converting the image shift amount into the defocus amount increases as the aperture is reduced in principle. Is the reason. Therefore, the AF restart threshold value may be changed according to this conversion coefficient instead of the aperture value. If there is a parameter whose conversion coefficient varies other than the aperture value, the AF restart threshold may be changed according to the parameter.

  As described above, in this embodiment, when performing the restart determination from the state where the focus lens is stopped, the restart condition is changed according to the degree of focus based on the imaging signal. If the degree of focus is low, it is presumed that there has been a scene change or subject change. Accordingly, it is possible to quickly follow the focus on the main subject, and it is possible to suppress blur and improve the quality of AF. If the degree of focus is high, it is presumed that the scene has not changed and the subject is still being captured, so the conditions for restarting are set to be strict. As a result, it is possible to prevent the focus from being shifted to a subject other than the main subject, to easily keep the focus on the main subject, and to improve the quality of AF.

  In this embodiment, the restart determination is performed based on the number of times of defocus amount ranging. However, the restart determination may be performed using time instead of the number of times. For example, the time is measured from the time when a defocus amount outside the depth is detected or the time when reliability becomes worse than a predetermined value, and the elapsed time is set as the AF restart threshold.

  According to the present embodiment, when performing AF control using the imaging surface phase difference detection method, it is possible to perform an appropriate focus lens restart determination according to the imaging conditions, and to realize high-quality focusing.

(Second embodiment)
Hereinafter, a second embodiment of the present invention will be described. In this embodiment, the AF restart determination method described as a characteristic part of the first embodiment is changed. In the first embodiment, when performing AF restart determination, AF restart is performed when a defocus amount outside the depth is continuously detected a predetermined number of times. On the other hand, in the present embodiment, the defocus amount threshold for restarting the focus in each in-focus state is changed.

  Since the configuration of the interchangeable lens camera including the lens unit and the camera body in the present embodiment is the same as that described with reference to FIG. 1 in the first embodiment, the description thereof is omitted. In addition, since the processing described with reference to the flowcharts of FIGS. 3, 4, 5, 7, and 12 in the first embodiment is the same in this embodiment, the description thereof is omitted.

  The AF restart determination process of this embodiment in step S409 of FIG. 4 will be described using the flowchart of FIG. In step S1001, the camera control unit 212 determines whether or not the reliability calculated in step S505 in FIG. 5 is better than a predetermined threshold value. When the reliability shows a good value, the process proceeds to step S1002, and when the reliability shows a bad value, the process ends. Note that the predetermined threshold here is set to a value with which the distance calculated from the defocus amount can be trusted, as in step S601 in FIG.

  In step S1002, the camera control unit 212 determines whether the calculated defocus amount is within the depth. If it is within the depth, the process ends. If it is outside the depth, the process proceeds to step S1003.

  In step S1003, AF restart threshold setting processing is performed, and the process proceeds to step S1004. Details of the AF restart threshold setting processing of this embodiment in step S1003 will be described later.

  In step S1004, it is determined whether or not the detected defocus amount is greater than or equal to the AF restart threshold set in step S1003. If it is less than the AF restart threshold, the process ends. On the other hand, if it is equal to or greater than the AF restart threshold value, the process moves to step S1005, the focus stop flag is turned off, AF restart is performed, and the process is terminated to restart the focus lens drive.

  Next, the AF restart threshold setting process in step S1003 of FIG. 10 will be described in detail with reference to FIG. The processes in steps S1601, S1603, and S1606 in FIG. 16 are the same as the processes in steps S1101, S1102, and S1106 in FIG.

  In step S1602, it is determined that the in-focus degree is “in-focus”, and the camera control unit 212 sets the AF restart threshold (defocus amount) to “out of depth 3”, and the process proceeds to step S1606. .

  In step S1604, it is determined that the degree of focus is “small blur”, and the camera control unit 212 sets the AF restart threshold to “outside depth 2”, and the process proceeds to step S1606.

  In step S1605, it is determined that the degree of focus is “large blur”. The camera control unit 212 sets the AF restart threshold to “out of depth 1”, and the process advances to step S1606.

Here, the AF restart threshold set in FIG. 16 will be described with reference to FIG. FIG. 17A shows the relationship of “outside depth 1”, “outside depth 2”, and “outside depth 3” as AF restart thresholds. The following conditions must be satisfied for the defocus amount threshold value set in the present embodiment.
Outside depth 3> Outside depth 2> Outside depth 1

  That is, at the time of “focusing”, the AF restart threshold is set to “out of depth 3”, so that the focus lens is restarted only when the defocus amount is large. Therefore, it is possible to prevent the focus control from becoming unstable due to variations in the defocus amount output when the subject is in focus. On the other hand, the AF restart threshold is set to “outside depth 1” at “large blur”, so that the focus is restarted if the defocus amount exceeds the depth. For this reason, it is possible to perform control so as to quickly focus at the time of “large blur”. Note that each threshold is tuned in consideration of easy restart when the main subject has changed, and inadvertently making it difficult to restart when the main subject has not changed.

  As described above, also in this embodiment, the condition for restarting the focus lens is changed according to the degree of focus. Thereby, when performing AF control using the imaging surface phase difference detection method, it is possible to perform an appropriate focus lens restart determination according to the imaging condition, and to realize focusing with high quality.

(Third embodiment)
The third embodiment of the present invention will be described below. In this embodiment, the AF restart determination method described as a characteristic part of the first embodiment is changed. In the first embodiment, when performing AF restart determination, AF restart is performed when a defocus amount outside the depth is continuously detected a predetermined number of times. On the other hand, in the present embodiment, control is performed so that AF is restarted when a defocus amount outside the depth (or reliability worse than the predetermined value) is detected a predetermined number of times or more out of the predetermined distance measurement times. That is, it is a control method for restarting AF without continuously detecting the defocus amount outside the depth.

  Since the configuration of the interchangeable lens camera including the lens unit and the camera body in the present embodiment is the same as that described with reference to FIG. 1 in the first embodiment, the description thereof is omitted. The operation of the camera body 20 described with reference to the flowcharts of FIGS. 3, 4, 5, 7, 11, and 12 in the first embodiment performs the same processing in this embodiment, and thus the description thereof is omitted.

  The AF restart determination process of the present embodiment in step S409 of FIG. 4 will be described using the flowchart of FIG. The processes in steps S1802, S1803, S1807, and S1809 in FIG. 18 are the same as the processes in steps S601, S602, S610, and S612 in FIG. The processing of this flow is executed by the camera control unit 212 (lens restart determination unit 213) unless otherwise specified.

  In step S1801, the camera control unit 212 shifts the AF restart determination flags a and b to the left and proceeds to step S1802. The number of distance measurements can be referred to by the processing in step S1801.

  If the reliability is better than a predetermined threshold value in step S1802 and the defocus amount is larger than a predetermined multiple of the depth in step S1803, the process proceeds to step S1804. In step S1804, the camera control unit 212 determines whether the focusing direction based on the phase difference detection result is the same as the previous direction. If the directions are the same, the process proceeds to step S1805. If the directions are not the same, the process proceeds to step S1806. If the process proceeds to step S1805, the camera control unit 212 sets the least significant bit of the AF restart determination flag b, and the process proceeds to step S1806. In step S1806, the camera control unit 212 sets the least significant bit of the AF restart determination flag a and proceeds to step S1807.

  On the other hand, if the reliability is worse than the predetermined threshold value in step S1802, the process proceeds to step S1810. In step S1810, the camera control unit 212 determines whether the focusing direction based on the phase difference detection result is the same as the previous direction. In the case of the same direction, the process proceeds to step S1811, and the camera control unit 212 sets the least significant bit of the AF restart determination flag b, and proceeds to step S1807. If they are not in the same direction, the process ends.

  In step S1808, which is performed after the AF restart threshold is set in step S1807, the camera control unit 212 determines whether the bit of the AF restart determination flag a or b is equal to or more than the number of AF restart thresholds. If the defocus amount is outside the depth with good reliability, the AF restart determination flag a is used. If the reliability is poor, the AF restart determination flag b is used for determination. If the condition in step S1808 is satisfied, the process proceeds to step S1809. If not, the process ends.

  In the first embodiment, the AF restart determination is performed using the AF restart counter. However, in this embodiment, an AF restart determination flag is used instead of the counter. In step S1801, the AF restart determination flag is shifted to the left each time AF restart determination is performed regardless of the detected defocus amount or reliability. When the detected defocus amount is larger than a predetermined value or the same direction as the previous time is obtained, the least significant bit of the AF restart determination flag is set in steps S1805, S1806, and S1811, respectively. In this way, the AF restart determination flag indicates the number of times that the defocus amount detected in the past predetermined number of distance measurements was greater than the predetermined (having poor reliability), depending on how many bits of the total number of bits stand. It can be treated as an indicator for knowing. The number of bits of the AF restart determination flags a and b corresponds to the number of times defocus for detecting AF restart is detected in step S1808. This number of bits needs to be set larger than the AF restart threshold that can be set in the AF restart threshold setting in step S1807. For example, if the AF restart determination flag “a” is set to 4 bits and the AF restart threshold is set to 3 times, the number of times that a defocus amount larger than a predetermined value is detected during the past 4 distance measurements is 3 times or more. Control to perform a restart.

  Compared with the first embodiment, the AF restart determination method according to the present embodiment can execute AF restart without continuously detecting a defocus amount larger than a predetermined value, so that it is easier to restart. become. As an advantage of the determination method of the present embodiment, for example, when shooting is performed under low illuminance, or when the shooting conditions are such that the defocus detection accuracy decreases, such as when the subject has low contrast, restarting is easier to perform be able to. The method of the first embodiment can suppress erroneous determination, but has the following disadvantages. In other words, the variation in detection results increases under shooting conditions where the defocus detection accuracy decreases, so the defocus amount within the depth is temporarily reduced, for example, in conditions where it is desired to restart quickly, such as in a “large blur” state. It takes a long time to execute the restart if detected. On the other hand, with the method of the present embodiment, AF can be restarted without continuously detecting a defocus amount larger than a predetermined value, so that it is easier to restart in a scene where restart is desired, and AF control is performed. Can improve the quality.

  Note that AF restart determination may be performed by using both the AF restart determination of the first and second embodiments and the AF restart determination of the third embodiment.

(Other embodiments)
The object of the present invention can also be achieved as follows. That is, a storage medium storing a program code of software in which a procedure for realizing the functions of the above-described embodiments is stored is supplied to the system or apparatus. A computer (or CPU, MPU, etc.) of the system or apparatus reads out and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the novel function of the present invention, and the storage medium storing the program code and the control program constitute the present invention.

  Examples of the storage medium for supplying the program code include a flexible disk, a hard disk, an optical disk, and a magneto-optical disk. Further, a CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD-R, magnetic tape, nonvolatile memory card, ROM, or the like can also be used.

  Further, by making the program code read by the computer executable, the functions of the above-described embodiments are realized. Furthermore, when the OS (operating system) running on the computer performs part or all of the actual processing based on the instruction of the program code, the functions of the above-described embodiments are realized by the processing. Is also included.

  Furthermore, the following cases are also included. First, the program code read from the storage medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, based on the instruction of the program code, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing.

  Although the present invention has been described in detail based on the preferred embodiments thereof, the present invention is not limited to these embodiments, and various forms within the scope of the present invention are also included in the present invention. It is.

DESCRIPTION OF SYMBOLS 10 Lens unit 20 Camera main body 103 Focus lens 105 Focus lens drive part 106 Lens control part 201 Image pick-up element 204 AF signal processing part 212 Camera control part 213 Lens restart determination part 216 AF evaluation value production | generation part

Claims (20)

Imaging means for receiving and photoelectrically converting a light beam incident through a photographing optical system including a focus lens;
First detection means for detecting a phase difference between a pair of image signals generated from light beams that have passed through different areas of the exit pupil area of the imaging optical system;
Second detection means for detecting contrast information from a signal output from the imaging means;
Control means for controlling the driving of the focus lens based on a detection result of at least one of the first detection means and the second detection means;
In a state where the focus lens is stopped, the control means determines whether or not a detection result by the first detection means satisfies a predetermined condition for restarting the focus lens, and the contrast information The automatic focus adjustment apparatus characterized in that the predetermined condition is changed according to the condition.   The automatic focus adjustment apparatus according to claim 1, wherein the control unit changes the predetermined condition in accordance with a focus degree determined based on the contrast information.   3. The automatic focus adjustment apparatus according to claim 2, wherein the control unit changes the predetermined condition so as to limit the restart of the focus lens as the degree of focusing increases. 4.   The control means calculates a defocus amount based on a detection result by the first detection means, and when the number of times or the period during which the defocus amount is detected above a predetermined value reaches a first threshold, 4. The automatic focus adjustment apparatus according to claim 1, wherein the focus lens is restarted.   The automatic focus adjustment apparatus according to claim 4, wherein the control unit increases the first threshold value as the degree of focusing determined based on the contrast information is higher.   The control means restarts the focus lens when the number of times or the period during which the same in-focus direction is detected based on the detection result by the first detection means reaches a second threshold value. The automatic focusing apparatus according to claim 4 or 5.   The control unit determines whether to restart the focus lens based on the second threshold when the reliability of the detection result by the first detection unit is worse than a predetermined level. The automatic focusing device described in 1.   The automatic focus adjustment apparatus according to claim 6 or 7, wherein the second threshold value is larger than the first threshold value.   9. The automatic focus adjustment according to claim 6, wherein the control unit increases the second threshold value as a degree of focusing determined based on the contrast information is higher. apparatus.   The control unit calculates a defocus amount based on a detection result by the first detection unit, and restarts the focus lens when the defocus amount equal to or greater than a third threshold is detected. An automatic focusing apparatus according to any one of claims 1 to 9.   The automatic focusing apparatus according to claim 10, wherein the control unit increases the third threshold value as the degree of focusing determined based on the contrast information is higher.   The automatic focus adjustment apparatus according to claim 1, wherein the second detection unit detects a phase difference between a pair of image signals output from the imaging unit.   The imaging means includes a plurality of photoelectric conversion elements under one microlens, and the plurality of photoelectric conversion elements respectively receive light beams that have passed through different areas of the exit pupil area of the photographing optical system. The automatic focusing apparatus according to claim 12.   14. The automatic focus adjustment apparatus according to claim 12, wherein the control unit changes the predetermined condition according to an image height.   15. The automatic focus adjustment apparatus according to claim 14, wherein the control unit changes the predetermined condition so as to limit restart of the focus lens as the image height is higher.   16. The control unit according to claim 12, wherein the control unit is capable of acquiring information on a diaphragm included in the photographing optical system, and changes the predetermined condition according to a size of an aperture of the diaphragm. The automatic focusing apparatus according to claim 1.   17. The automatic focusing apparatus according to claim 16, wherein the control unit changes the predetermined condition so as to limit the restart of the focus lens as the aperture of the diaphragm is smaller. A method for controlling an automatic focus adjustment apparatus having an imaging means for receiving and photoelectrically converting a light beam incident through a photographing optical system including a focus lens,
A first detection step of detecting a phase difference between a pair of image signals generated from light beams that have passed through different areas of the exit pupil area of the photographing optical system;
A second detection step of detecting contrast information from a signal output from the imaging means;
A control step for controlling the driving of the focus lens based on a detection result of at least one of the first detection step and the second detection step;
In the state in which the focus lens is stopped, in the control step, it is determined whether or not a detection result by the first detection unit satisfies a predetermined condition for restarting the focus lens, and the contrast information And changing the predetermined condition according to the control method.   A control program for an automatic focus adjustment apparatus, characterized in that the control method for an automatic focus adjustment apparatus according to claim 18 is executed by a computer.   20. A storage medium storing a control program for the automatic focusing apparatus according to claim 19.