JP2017219791A - Control device, imaging device, control method, program, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device that can perform accurate focus detection even when asymmetric optical vignetting occurs.SOLUTION: A control device comprises: acquisition means (169a) that acquires a first signal and a second signal corresponding to luminous fluxes passing through pupil areas different from each other in an imaging optical system; correction means (166) that corrects base length information on the basis of exit pupil information according to a focus detection position; and calculation means (169b) that calculates the amount of defocus on the basis of the amount of image shift obtained from the value of correlation between the first signal and second signal and the corrected base length information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus that performs focus detection using a phase difference detection method.

  2. Description of the Related Art Conventionally, so-called live view shooting is known in which shooting is performed while observing a subject image formed on an imaging pixel in real time when shooting a still image or a moving image.

  Patent Document 1 discloses an imaging apparatus that performs focus detection by a phase difference detection method in order to perform fast and accurate focus detection during live view shooting. The imaging apparatus of Patent Document 1 relates to a conversion coefficient for performing conversion to a defocus amount using the correlation value obtained by the phase difference detection method and the baseline length information, and introduces an error caused by light vignetting of the imaging optical system. The conversion factor is calibrated by feedback.

JP 2010-25997 A

  However, when the ray vignetting is asymmetric, it is difficult to obtain accurate baseline length information, and the focus detection accuracy may be lowered.

  Therefore, the present invention provides a control device, an imaging device, a control method, a program, and a storage medium that can perform focus detection with high accuracy even when asymmetric optical vignetting occurs.

  A control device according to one aspect of the present invention includes a signal acquisition unit that acquires a first signal and a second signal corresponding to light beams that pass through different pupil regions of an imaging optical system, and exit pupil information according to a focus detection position. A defocus amount based on the correction means for correcting the baseline length information based on the image, the image shift amount obtained from the correlation value between the first signal and the second signal, and the corrected baseline length information Calculating means for calculating.

  An imaging apparatus according to another aspect of the present invention includes an imaging device having a first photoelectric conversion unit and a second photoelectric conversion unit that receive light beams passing through different pupil regions of an imaging optical system, and the first photoelectric conversion unit. And signal acquisition means for acquiring the first signal and the second signal corresponding to each of the output signals from the second photoelectric conversion unit, and correction for correcting the baseline length information based on the exit pupil information corresponding to the focus detection position And a calculating means for calculating a defocus amount based on the image shift amount obtained from the correlation value between the first signal and the second signal and the corrected baseline length information.

  According to another aspect of the present invention, there is provided a control method comprising: obtaining a first signal and a second signal corresponding to light beams passing through mutually different pupil regions of an imaging optical system; and exit pupil information corresponding to a focus detection position. A defocus amount is calculated based on the step of correcting the baseline length information based on the image, the image shift amount obtained from the correlation value between the first signal and the second signal, and the corrected baseline length information. A step of performing.

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

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

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

  According to the present invention, it is possible to provide a control device, an imaging device, a control method, a program, and a storage medium capable of highly accurate focus detection even when asymmetric optical vignetting occurs.

It is a block diagram of the imaging device in this embodiment. It is a pixel array diagram of the image sensor in the present embodiment. It is a pixel array diagram of the image sensor in the present embodiment. It is a pixel array diagram of the image sensor in the present embodiment. In this embodiment, it is a relationship figure between the signal state from a focus detection pixel, the gravity center position of the light reception angle range of a focus detection pixel, and a base line length. It is a relationship figure of the vignetting state and exit pupil distance of the image pick-up optical system in this embodiment. In this embodiment, it is a related figure of the pupil shape and base line length of an off-axis ray in the stop position of an imaging optical system. In this embodiment, it is explanatory drawing of the method of estimating asymmetric vignetting from the change of an exit pupil distance, and calculating a pseudo F value. FIG. 6 is a relationship diagram between an exit pupil distance and a peripheral light amount ratio and an image height in the present embodiment. 5 is a flowchart of focus detection and focus control in the present embodiment.

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

  First, with reference to FIG. 1, a schematic configuration of the imaging apparatus according to the present embodiment will be described. FIG. 1 is a block diagram of an imaging apparatus 10 (camera) in the present embodiment. The imaging device 10 includes a digital camera system (an electronic camera capable of recording moving images and still images) including a camera body 150 (imaging device body) and a lens device 100 (interchangeable lens, imaging optical system) that can be attached to and detached from the camera body 150. System). However, the present embodiment is not limited to this, and can also be applied to an imaging apparatus in which a camera body and a lens are integrally configured. In FIG. 1, portions unnecessary for the description of the present embodiment are omitted.

  In FIG. 1, reference numeral 101 denotes a lens group of the imaging optical system. Reference numeral 102 denotes a diaphragm (a glow diaphragm) whose opening diameter is adjusted (controlled) by the diaphragm diameter driving means 106, and the light quantity can be adjusted during photographing. In the lens apparatus 100, the lens group 101 is moved in the direction (optical axis direction) along the optical axis AX by the focus driving unit 105, and performs focus position adjustment (focus control). The focus driving unit 105 and the aperture diameter driving unit 106 receive a control command from the lens side CPU 104 and perform drive control. More specifically, the focus driving unit 105 and the aperture diameter driving unit 106 are based on a focus detection evaluation value and a photometric value from the camera body 150 communicated between the camera side transmission unit 171 and the lens side transmission unit 103. Controlled.

  The lens apparatus 100 includes the exit pupil distance information 107 according to the change characteristic of the exit pupil distance of the imaging optical system when the zoom position or the focus position of the imaging optical system changes, and the peripheral light amount ratio information according to the change characteristic of the peripheral light amount ratio. 108 is stored. The lens device 100 also includes F value range information that can be set in the control of the diameter of the aperture 102, optical characteristic information such as the focal length of the imaging optical system (focal length range in the case of a zoom lens), and the imaging optical system. Various optical system information 109 including identification information is stored. The exit pupil distance information 107, the peripheral light amount ratio information 108, and the optical system information 109 are transmitted to the camera body 150 via the lens side transmission unit 103 and the camera side transmission unit 171. In the present embodiment, exit pupil distance information 107, peripheral light amount ratio information 108, and various optical system information 109 are stored in the storage unit of the lens apparatus 100.

  The camera body 150 is an interchangeable lens single-lens reflex camera, and the subject light beam from the lens apparatus 100 is switched between deflection and non-deflection by driving a flip-up reflection member 155. In the reference state in which the reflecting member 155 is not raised, the subject light beam is deflected and a subject image is formed on the focus plate 154. The subject image on the focusing screen 154 can be visually observed through the pentagonal reflecting prism 151 by the eyepiece lens 152. At the same time, the subject image is taken into the photometric optical unit 153. The photometry unit 159 detects the illuminance of the subject imaged on the focus plate 154 based on the conversion signal obtained by the photometry optical unit 153, and determines the exposure amount. At that time, the illuminance of the subject on the focus plate 154 becomes dark due to a dimming phenomenon or optical vignetting caused by an inconsistent relationship between the angle of light incident on the focus plate 154 from the imaging optical system and the diffusion intensity characteristic. For this reason, the detected exposure amount includes an error with respect to an appropriate value. Therefore, the exposure amount is corrected by acquiring the light beam angle information from the exit pupil distance information 107 of the imaging optical system and acquiring the optical vignetting amount from the peripheral light amount ratio information 108 to predict the dimming state. The exposure amount determination unit 160 corrects the exposure amount to determine an appropriate exposure amount, and generates a signal for adjusting the gain amount by the image sensor driving unit 161 and a signal for controlling the aperture diameter of the lens device 100.

  A part of the reflecting member 155 has a semi-transmissive property. The light beam transmitted through the reflecting member 155 is deflected by the double reflecting member 156 and is incident on the focus detection unit 157. The birefringent member 156 is folded in conjunction with the reflecting member 155 in a state where the reflecting member 155 jumps up (shown by a broken line), and prevents the subject light beam incident on the image sensor 158 from being obstructed (subject light beam). Is incident on the image sensor 158). The light beam incident on the focus detection unit 157 is photoelectrically converted and output to the AF signal output unit 167. The AF signal output unit 167 extracts an AF image signal (focus detection signal) that is phase difference information between the pair of pixel signals, and transmits the AF image signal to the AF selection unit 168.

  The image sensor 158 is an image sensor composed of a CMOS sensor and its peripheral circuits. The image sensor 158 is a two-dimensional single-plate color sensor in which M pixels in the horizontal direction and N pixels in the vertical direction are squarely arranged, and a Bayer array primary color mosaic filter is formed on-chip. The image sensor 158 is configured by arranging AF pixels (focus detection pixels) among a plurality of image pickup pixels, as will be described later. In the present embodiment, the image sensor 158 includes AF pixels (first photoelectric conversion unit and second photoelectric conversion unit) that receive light beams that pass through different pupil regions of the imaging optical system.

  Next, the focus adjustment operation (AF operation) in the live view state in a state where the reflection member 155 is flipped up (state indicated by a broken line) will be described. As a premise, it is assumed that a subject position (focus detection position) to be a focus detection target has already been determined.

  When the image sensor 158 receives the subject image, the pixel signal output unit 162 outputs a photoelectrically converted signal. The AF signal extraction unit 163 extracts an AF signal (focus detection signal) at the focus detection position for performing a phase difference correlation calculation (phase difference AF). The AF selection means 168 is either a phase difference detection type focus detection using the focus detection unit 157 or a phase difference detection type focus detection using the image sensor 158 (so-called AF in a live view state). It is determined whether to perform detection processing.

  In order to obtain an appropriate exposure state during focus detection (during AF control), the exposure amount determination unit 160 adjusts the signal intensity output from the pixel signal output unit 162. The camera-side CPU 169 determines the set F value based on the F value that can be taken by the imaging optical system, transmitted from the optical system information 109. The set F value is transmitted to the aperture diameter driving unit 106 of the lens apparatus 100 via the camera side transmission unit 171 and the lens side transmission unit 103. The diaphragm diameter driving means 106 sets the F value by changing the diaphragm 102 (diaphragm diameter).

  The vignetting state acquisition unit 164 (vignetting information acquisition unit) is based on the F value (F value information), the position information of the focus detection pixel of the image sensor 158, and the exit pupil distance information 107, and the exit pupil distance of the imaging optical system. Get the change state of. Then, the vignetting state acquisition unit 164 estimates a light vignetting state (light vignetting information) as described later.

  Baseline length information acquisition unit 165 (baseline length acquisition unit) stores in advance baseline length information corresponding to the F value of the imaging optical system. The baseline length information acquisition unit 165 converts the F value of the imaging optical system into a pseudo F value (pseudo F value) based on the ray vignetting information acquired by the vignetting state acquisition unit 164, and according to the pseudo F value. Get baseline length information. The baseline length correction unit 166 determines whether or not the optical vignetting state is an asymmetric optical vignetting state, acquires a new pseudo F value, and acquires new baseline length information from the baseline length information acquisition unit 165 again. . The baseline length correction unit 166 generates highly accurate baseline length information (corrects the baseline length information) based on the acquired plurality of baseline length information. Then, the baseline length correction unit 166 transmits the corrected baseline length information to the camera side CPU 169.

  The camera-side CPU 169 drives various circuits of the camera body 150 based on a predetermined program stored therein, and performs a series of focus detection processing (defocus amount calculation processing), shooting processing, image formation processing, recording processing, and the like. Perform the action. In the present embodiment, the camera side CPU 169 includes a signal acquisition unit 169a and a calculation unit 169b. These functions will be described later. When the AF method using the focus detection unit 157 is selected, baseline length information unique to the focus detection unit 157 is used. On the other hand, in focus detection during live view, the focus drive amount determination unit 170 obtains the defocus amount using the baseline length information transmitted from the baseline length correction unit 166, and calculates the focus lens drive amount. The focus lens driving amount is transmitted to the lens side CPU 104 via the camera side transmission unit 171 and the lens side transmission unit 103. The lens side CPU 104 outputs a drive control command to the focus drive means 105 based on the transmitted focus lens drive amount, and performs focus lens drive (focus control) for focus control.

  In the present embodiment, the exit pupil distance information 107, the peripheral light amount ratio information 108, and the optical system information 109 are stored in a storage unit provided in the lens apparatus 100, but the present invention is not limited to this. is not. If the type of the mounted imaging optical system can be determined and necessary information can be acquired, at least the exit pupil distance information 107, the peripheral light amount ratio information 108, and the optical system information 109 are at least One may be stored in storage means provided inside the camera body 150. Further, according to this configuration, the baseline length correction unit 166 shares the peripheral light amount ratio information 108 of the imaging optical system and the exit pupil distance information of the imaging optical system, which are stored for correcting the exposure amount of the peripheral portion of the screen. This has the advantage of preventing an increase in the amount of data.

  Next, the configuration and light receiving characteristics of the focus detection pixels used in the image sensor 158 of this embodiment will be described with reference to FIGS. FIG. 2 is a pixel array diagram of the image sensor 158 in the present embodiment. In FIG. 2, the vertical direction is the Y direction, and the horizontal direction is the X direction. The same applies to FIGS. 3 and 4.

  In FIG. 2, reference numeral 200 denotes a pixel (imaging pixel) for forming a captured image, and 201 to 204 are focus detection pixels having a light shielding structure described in, for example, Japanese Patent Application Laid-Open No. 2009-244862. In FIG. 2, for a subject having a horizontal stripe pattern shape, pixels 201 and 202 arranged in a line in the Y direction are used to output signal waveforms (a pair of pixel signals) of the pixels 201 and 202 (two photoelectric conversion units). Based on this, a correlation calculation using a phase difference detection method is performed to detect the focal position of the subject. Similarly, a subject having a vertical stripe pattern shape is correlated based on output signal waveforms of the pixels 203 and 204 (two photoelectric conversion units) using the pixels 203 and 204 arranged in a line in the X direction in FIG. Calculation is performed to detect the focal position of the subject.

  FIG. 3 is a pixel array diagram of an image sensor 158 as a modification of the present embodiment. The image pickup device in FIG. 3 has two photoelectric conversion units (two subpixels) for one microlens, and a plurality of pixels 300 and 301 are alternately arranged two-dimensionally. In FIG. 3, a pixel 301 is used to perform focus calculation of a subject having a stripe pattern in the Y direction using a signal from subpixels 302 and 303 arranged in the X direction as phase difference information of a pair of pixel signals. . Further, the pixel 300 is used for performing a correlation calculation using the signals from the sub-pixels 304 and 305 arranged in the Y direction for the focus detection of the subject having the stripe pattern in the X direction as a pair of pixel signals. When outputting a photographic image signal, the signals of the sub-pixel 302 and the sub-pixel 303 are added, and the signals of the sub-pixel 304 and the sub-pixel 305 may be added.

  FIG. 4 is a pixel array diagram of an image sensor 158 as a modification of the present embodiment. 4 has four photoelectric conversion units (four subpixels) for one microlens, and a plurality of pixels 400 having the same structure are arranged in a two-dimensional manner. The image sensor of FIG. 4 can obtain the same pixel characteristics as the structure of FIG. 3 by changing the method of adding the output signals from the four photoelectric conversion units. In FIG. 4, when detecting the focus of a subject having a stripe pattern in the Y direction, the signals of the subpixels 401 and 402 arranged in the X direction are added, the signals of the subpixel 403 and the subpixel 404 are added, The obtained two columns of added signal waveforms are used for correlation calculation as phase difference information of a pair of pixel signals. Further, when focus detection of a subject having a stripe pattern in the X direction is performed, signals of the subpixel 401 and the subpixel 403 arranged in the Y direction are added, and signals of the subpixel 402 and the subpixel 404 are added. The added signal waveforms of the two columns thus obtained are used for correlation calculation as phase difference information of a pair of pixel signals.

  The above-described two addition methods for focus detection may be divided into blocks on the image sensor and changed. By changing the addition alternately in a staggered arrangement, a pixel arrangement structure equivalent to the structure shown in FIG. 3 can be achieved. In this case, since the vertical stripe pattern subject and the horizontal stripe pattern subject can be simultaneously evaluated, it is possible to remove or reduce the subject pattern direction dependency in focus detection. The addition method may be switched according to the shooting state, or may be switched in time series for all pixels. At this time, since the focus detection pixels for detecting the focus of the subject in the same pattern direction are in a dense state, a subject having a thin line segment generated when the focus detection pixel is sparse cannot be detected near the focus. It can be avoided. When used as an imaging signal, the signals of the subpixels 401 to 404 may be added.

  By using the imaging device structure shown in any of FIGS. 2 to 4, it is necessary to separate a part of the subject image via the imaging optical system into an optical system dedicated to focus detection as in the conventional phase difference detection method. Does not occur. For this reason, live view shooting can be performed while monitoring a subject image on which an image pickup device receives light and records an image in real time. In conventional moving image shooting, it cannot be performed without a subject beam splitting mechanism. It is possible to detect the focus by the phase difference detection method.

  In the focus detection of the phase difference detection method, the relative relationship between the A image signal waveform and the B image signal waveform, which are light reception signals (hereinafter referred to as A image and B image) of the pair of focus detection pixel groups having the pixel structure as described above. Overlay each other's waveforms while shifting the position. For example, a state where the area amount of the difference portion of the waveform is the smallest is the state where the correlation is the highest (the correlation value is the highest). In general, the defocus amount is detected (calculated) based on the relative shift amount (image shift amount) between the A image and the B image in such a state.

  When calculating the defocus amount, the pupil separation width of the pair of focus detection pixels as described with reference to FIGS. 2 to 4 is stored in the imaging apparatus 10 as baseline length information from the image shift amount at the pupil position. It is necessary to keep. At this time, in the in-focus state, the image shift amount at the pupil position substantially matches the baseline length. On the other hand, in the out-of-focus state, the image shift amount changes substantially in proportion to the defocus amount. For this reason, the defocus amount is obtained by dividing the baseline length from the image shift amount.

  Here, the above-described content will be described with reference to FIG. FIG. 5 is a relationship diagram between the signal state from the focus detection pixel, the barycentric position of the light reception angle range of the focus detection pixel, and the baseline length. FIG. 5 shows a state where asymmetrical light vignetting has not occurred. In FIG. 5, P is a position corresponding to the exit pupil distance of the imaging optical system. A, B, and C indicate focal positions, and B corresponds to the position (focus position) of the image sensor. A is a so-called front pin state, and the defocus amount at that time is DEF1 (minus value). C is a so-called rear pin state, and the defocus amount at that time is DEF2 (plus value).

  The waveform of the focus detection signal described below is obtained from an image sensor having a pixel structure as described with reference to FIGS. In FIG. 5, a position P is a position (a stop position) corresponding to the exit pupil distance PO from the in-focus position B. ZA is an image shift amount necessary for obtaining a correlation from phase difference information of a pair of pixel signals that are photoelectric conversion signals of the focus detection pixel group in the front pin state (focal position A). ZB is an in-focus state (in-focus position B), and since focusing is performed, the waveforms of the two focus detection signals overlap each other, and no image displacement occurs. ZC is an image shift amount in the rear pin state (focus position C), and shows a state in which the positions of the two focus detection signals are switched with respect to the image shift amount ZA.

  R1 and R2 in FIG. 5 are signal intensity distributions obtained by back projecting the signal intensity characteristics with respect to the light receiving angle of the pair of focus detection pixels on the plane of the position P corresponding to the exit pupil distance PO of the imaging optical system from the focus detection pixels. is there. The barycentric positions of the signal intensity distributions R1 and R2 are obtained, and the distance between the barycentric positions is set as the base line length L. The exit pupil diameter changes according to the F value information of the imaging optical system and the exit pupil distance PO. For this reason, the base line length L is determined according to the F value information of the imaging optical system and the exit pupil distance PO.

  In summary, the base line length L, the exit pupil distance PO, and the image shift amounts ZA and ZC have a relationship expressed as the following equations (1-1) and (1-2).

L: PO = ZA: DEF1 (1-1)
L: PO = ZC: DEF2 (1-2)
For this reason, the defocus amounts DEF1 and DEF2 are obtained as represented by the following equations (2-1) and (2-2).

DEF1 = ZA · PO / L (2-1)
DEF2 = ZC · PO / L (2-2)
Here, the base line length L (base line length information) is calculated by using a signal output characteristic based on a light receiving angle of a focus detection pixel used in the imaging apparatus. Baseline length information calculates the center of gravity of each separation region paired at the pupil position using a virtual imaging optical system in which arbitrary F-number information and exit pupil distance PO are set, similar to the calculation of the image shift amount. do it. Then, the distance (baseline length L) between the two barycentric positions is set as the reference baseline length. As described above, when the output signal intensity with respect to the light receiving angle of the focus detection pixel used in the imaging apparatus is known, the base line length L is previously related to the F length information of the imaging optical system and the base line length L to the exit pupil distance PO Can be held in the form of an approximate expression coefficient or a two-dimensional array. Then, such baseline length information is stored in the imaging apparatus, a defocus amount is calculated based on the image shift amount and the baseline length information, and focusing control is performed.

  However, when performing the focus detection processing of the peripheral image height, the light bundle formed on the imaging surface is greatly vignetted due to the finite lens outer diameter of the imaging optical system as the image height increases. Therefore, if the stored baseline length information is used as it is, there is a possibility that accurate focusing cannot be performed.

  The light vignetting can be in various states depending on the effective diameters and arrangement states of the lenses and light shielding members that constitute the imaging optical system. Ideally, it is desirable to have a pupil shape that is symmetrical in the radial direction perpendicular to the image height change direction from the optical axis at the stop position (exit pupil distance) of the imaging optical system. With such a pupil shape, the base line length in the peripheral image height can be considered to be substantially equivalent to the one in which the F value apparently changes due to the light vignetting even when the light beam vignetting occurs. Correction processing is facilitated. However, as will be described below, when the light vignetting has an asymmetric shape, it becomes difficult to correct the baseline length.

  It is necessary to shield the ring zone of the light beam that causes the downsizing of the imaging optical system and large coma aberration as the cause of the deviation of the light vignetting state, but it is necessary to secure a certain amount of peripheral light, and therefore it is necessary to shield it This is because a certain light beam range is biased. In a variable magnification imaging optical system in which the lens group is movable, it may be difficult to set an ideal light vignetting state in all variable magnification regions. The exit pupil distance of the imaging optical system is a so-called chief ray and optical axis, which is an intermediate ray of a light beam width to an arbitrary image height in the optical path state on the meridional section of the optical system in the correlation direction for focus detection. It is a crossing position. When the optical vignetting is symmetric in the cross-sectional direction, the stop position of the imaging optical system is substantially the exit pupil distance.

  However, when asymmetrical vignetting occurs in the cross-sectional direction, the exit pupil distance changes so as to deviate from the aperture position. Such a change in the exit pupil distance can be obtained by performing a ray tracing calculation by the method as described above with respect to a change in the image height as an ideal aperture position of the imaging optical system at the center position of the image height. . Then, if necessary, the magnification position, the F value, and the focus position are changed and stored as exit pupil distance information 107 in FIG. 1 in the imaging optical system or imaging apparatus.

  Next, a method for predicting an asymmetric optical vignetting state using the exit pupil distance information 107 and the peripheral light amount ratio information 108 to acquire highly accurate baseline length information will be described. In addition, although the figure regarding the light vignetting uses an optical sectional view in the vertical direction for the sake of simplicity, it is actually considered as an optical sectional view in the correlation direction. For example, if the X direction in FIGS. 2 and 3 is the horizontal direction of the image sensor, paired focus detection pixels such as the pixels 201 and 202 in FIG. 2 and the sub-pixels 302 and 303 in FIG. 3 are used. When performing correlation, the optical section is considered as the horizontal direction on the left and right. On the other hand, when the correlation is performed using the focus detection pixels that are a pair of the pixels 203 and 204 in FIG. 2 and the sub-pixels 304 and 305 in FIG. In order to simplify the following description, the pupil separation state of the pair of focus detection pixels located at the off-axis image height of the imaging element is configured to be an ideal state at the exit pupil distance of the imaging optical system. It is assumed that

  Next, an example of a state in which the light vignetting state of the light beam emitted to the peripheral image height is asymmetrically biased will be described with reference to FIG. FIG. 6 is a relationship diagram between the vignetting state of the imaging optical system and the exit pupil distance. PO in FIG. 6 is a distance (exit pupil distance) from the imaging plane IP to the exit pupil plane. UR is the upper ray (upper line) of the ray bundle in FIG. 6, BR is the lower ray (underline) of the ray bundle, PR is the principal ray, and is formed by an angle that bisects the angle formed by the upper line UR and the underline BR. This is a light beam emitted to the image plane IP.

  FIG. 6A shows a state in which optical vignetting symmetrical in the vertical direction is generated, FIG. 6B shows a state in which the upper line UR is larger, and FIG. 6C shows a larger vignetting in the lower line BR. Each state is shown. In FIG. 6A, the optical axis and the principal ray PR intersect at the stop position of the imaging optical system, and the exit pupil distance PO corresponds to the distance from the imaging plane IP to the stop position. At this time, the exit pupil distance PO is substantially the same as the exit pupil distance Po0 when no optical vignetting occurs.

  On the other hand, in FIG. 6B, when the upper line UR is largely vignetted, the emission angle of the principal ray PR to the imaging plane IP changes to the minus side (lower side) with respect to FIG. . For this reason, the position where the principal ray PR and the optical axis intersect changes in the imaging plane IP direction, the exit pupil distance becomes shorter, and the exit pupil distance Po1 is different from the exit pupil distance Po0.

  Further, in FIG. 6C, the underline BR is greatly vignetted, so that the emission angle of the principal ray PR to the imaging plane IP changes to the plus side (upper side) with respect to FIG. For this reason, the position where the principal ray PR and the optical axis intersect changes in the object side direction, the exit pupil distance becomes longer, and the exit pupil distance Po1 is different from the exit pupil distance Po0. Therefore, by using the exit pupil distance information 107 to compare the ideal exit pupil distance at the center image height and the exit pupil distance at the arbitrary image height, the asymmetric vignetting state is either the overline UR or the underline BR. It can be estimated whether it is greatly occurring.

  Next, with reference to FIG. 7, the change state of the baseline length in the asymmetric optical vignetting state will be described. FIG. 7 is a relationship diagram between the pupil shape of the off-axis ray and the base line length at the stop position of the imaging optical system in the optical vignetting state of FIG. 7A, 7B, and 7C, the imaging optical system corresponds to the states of FIGS. 6A, 6B, and 6C, respectively. FIG. 7 shows the pupil range of the light bundle incident on the image height Y at the pupil position (the stop position in FIG. 6), and the light range incident on the pair of focus detection pixels from the pupil range (pupil range of the focus detection pixel). FIG. 6 is an explanatory diagram of a change state of the baseline length L due to asymmetric optical vignetting. 7A, 7B, and 7C show the pupil shape, and the right figure shows the received light intensity of each focus detection pixel and the base line length between the barycentric positions.

  The PU in the left diagram in FIG. 7 represents the pupil shape of the light bundle that is imaged at the image height HGT at the pupil position (aperture position) of the imaging optical system in FIG. Similarly, S1 and S2 are ranges of light bundles (focal points) that can be received by the pair of focus detection pixels for performing the phase difference detection described with reference to FIGS. 2 to 4 at the pupil position of the imaging optical system. The pupil range of the detection pixel). R1 and R2 in the right diagram in FIG. 7 indicate signals (light reception intensity signals) of the focus detection pixels, and the horizontal direction X corresponds to the vertical direction in FIG. L indicates the base line length and indicates the distance between the centers of gravity of the signals R1 and R2.

  FIG. 7A shows the pupil shape of the light bundle and the associated base line length L when the optical vignetting in the X direction is symmetric. Here, the signals R1 and R2 (signal intensity) in the pair of focus detection pixels have substantially symmetrical shapes, and the center positions of the respective centers are the same distance from the pupil center position. Therefore, the baseline length L is assumed to be a baseline length equivalent to a pupil diameter defined by a pseudo F value as indicated by a broken line F in FIG. The baseline length information stored in can be used. Such determination of the presence or absence of optical vignetting symmetry can be detected based on the change information of the exit pupil distance with respect to the image height change, as shown in FIG. Then, if the corresponding F value is considered as a ratio of the area ratio of the pupil to the short side change of the pseudo ellipse based on the peripheral light amount ratio information, the F value of the pupil diameter having the short side on the pupil as the diameter is used. Good.

  FIG. 7B shows the signal intensity of the focus detection signal and the change in the center of gravity position in a state where the upper line of the light bundle is larger and vignetting occurs as shown in FIG. 6B. Since the vignetting is larger in the range S2 than in the range S1 in FIG. 7A, the X direction width of the signal R2 is shorter in the pupil center position direction. For this reason, the gravity center position from the pupil center of the signal R2 is shorter than the gravity center position of the signal R1. Therefore, the baseline length L in FIG. 7B is shorter than the baseline length L in FIG. In a state where asymmetrical light vignetting is generated, the shape of the pupil of the light beam is a shape surrounded by arcs of two different radii. For this reason, if matching with the elliptical shape is performed, matching with the aperture area obtained from the peripheral light amount ratio information causes an error, and at the same time, the position of the center of gravity of the signal of each focus detection pixel is symmetric from the pupil center. If the baseline length information is acquired from the F value, the problem of an increase in baseline length error occurs.

  FIG. 7C shows the signal intensity of the focus detection signal and the change in the position of the center of gravity when the vignetting is greatly generated in the underline of the light bundle as shown in FIG. 6C. Therefore, contrary to FIG. 7B, the signal R1 of the focus detection pixel becomes smaller than the signal R2 due to the effect of optical vignetting. As a result, in contrast to FIG. 7B, the barycentric position of the signal R1 from the center of the pupil with respect to the signal R2 is shortened, and the baseline length is shorter than the baseline length L of FIG.

  Next, a method for estimating the amount of occurrence of asymmetric optical vignetting from the state in which asymmetric optical vignetting as described with reference to FIGS. 6 and 7 has occurred will be described with reference to FIG. FIG. 8 is an explanatory diagram of a method of calculating a pseudo F value by estimating asymmetric vignetting from a change in exit pupil distance.

  In the present embodiment, the camera-side CPU 169 acquires exit pupil distance information corresponding to the F value (F value state) of the imaging optical system at the time of focus detection from the exit pupil distance information 107 in FIG. The camera-side CPU 169 obtains exit pupil distance change state information based on the relationship between the obtained exit pupil distance information and the change in focus detection position (change in image height), and estimates the amount of occurrence of asymmetric optical vignetting. To do.

FIG. 8A shows an asymmetrical light vignetting state caused by light vignetting due to the effective diameter of the rear lens of the imaging optical system in FIG. 6B. On the other hand, FIG. 8B shows an asymmetrical light vignetting state caused by light vignetting due to the effective diameter of the front lens of the imaging optical system in FIG. 6C. In FIG. 8, H represents the exit pupil diameter when there is no asymmetrical light vignetting, AX represents the optical axis of the imaging optical system, and IP represents the image plane. HGT indicates the image height position where the light beam forms an image, and UR, BR, and PR respectively indicate the upper line, the lower line, and the chief ray when there is no asymmetrical light vignetting.
Further, the position where the principal ray PR and the optical axis AX intersect is defined as the exit pupil position (stop position), and the distance from the imaging plane IP to the exit pupil position is defined as the exit pupil distance Po0.

  In FIG. 8, UR ′, BR ′, and PR ′ respectively indicate the upper line, the lower line, and the principal ray of the light bundle when the light vignetting occurs due to the effective lens diameter. A position where the principal ray PR ′ and the optical axis AX intersect is defined as an exit pupil position when asymmetrical light vignetting occurs, and a distance from the imaging plane IP to the exit pupil position is defined as an exit pupil distance Po1. Here, an angle formed by the optical axis AX and the upper line UR is U_ANG, and an angle formed by the optical axis AX and the lower line BR is B_ANG. Similarly, when optical vignetting occurs, the angle formed by the optical axis AX and the upper line UR ′ is U′_ANG, and the angle formed by the optical axis AX and the lower line BR ′ is B′_ANG. The angle is P′_ANG (not shown).

  Next, a method for obtaining the above-described various variable values and obtaining highly accurate baseline length information will be described. First, assuming that the F value of the imaging optical system at the time of focus detection is Fno, the pupil radius H at the stop position (ideal exit pupil distance) of the imaging optical system is expressed as the following equation (3). Is done.

H = Po0 · TAN (ω) (3)
(Ω = SIN-1 (1/2 · Fno))
The angles U_ANG and B_ANG are represented by the following equations (4-1) and (4-2), respectively.

U_ANG = TAN-1 ((HGT-H) / Po0) (4-1)
B_ANG = TAN-1 ((HGT + H) / Po0) (4-2)
When ray vignetting occurs on the upper line as shown in FIG. 8A, the relationship of the following equation (5) can be obtained from the exit pupil distance Po1 obtained in advance.

Y = Po1 · TAN (P′_ANG) (5)
By transforming equation (5), as represented by the following equation (6), an angle P′_ANG of the principal ray at which optical vignetting is generated can be obtained.

P′_ANG = TAN−1 (HGT / Po1) (6)
Here, assuming that the chief ray angle of the light bundle causing vignetting is an angle that divides the upper line and the underline into two, the chief ray angle P′_ANG is expressed as the following Expression (7).

P′_ANG = (U′_ANG + B_ANG) / 2 (7)
By transforming equation (7), as represented by the following equation (8), an angle U′_ANG formed by the upper line where the light vignetting occurs and the optical axis can be obtained.

U′_ANG = 2 · P′_ANG−B_ANG (8)
Then, the pupil height HU in the direction in which vignetting occurs at the stop position as an ideal exit pupil can be obtained as expressed by the following equation (9).

HU = HGT-Po0 · TAN (U'_ANG) (9)
Here, the pseudo F value Fno ′ in which the pupil height HU is the pupil radius can be expressed as the following formula (10) by modifying the formula (3).

Fno ′ = 1 / (2 · SIN (ω)) (10)
Since the ray angle ω is ω = ATAN (HU / Po0), by substituting into the equation (10), the pseudo F value Fno ′ of the ray bundle on which the ray vignetting is generated can be expressed by the following equation (10): 11).

Fno ′ = 1 / (2 · SIN (TAN-1 (HU / Po0))) (11)
Also, as shown in FIG. 3B, when the underline generates ray vignetting, the pupil radius HB can be obtained by using B′_ANG instead of U′_ANG. The pseudo F value Fno ′ can be expressed by the following equation (12) using the pupil radius HB.

Fno ′ = 1 / (2 · SIN (TAN-1 (HB / Po0))) (12)
As described above, the F value of the imaging optical system when there is no vignetting and the pseudo F value (pseudo F value information) represented by the equation (11) or the equation (12) when vignetting occurs. Can be acquired. The baseline length correction unit 166 acquires two pieces of baseline length information corresponding to each pseudo F value from the baseline length information acquisition unit 165 of FIG. 1 using these two types of pseudo F value information. Then, the baseline length correction unit 166 averages the obtained two baseline lengths to generate a highly accurate corrected baseline length. The camera side CPU 169 converts the image shift amount obtained by the correlation calculation represented by the equations (2-1) and (2-2) into the defocus amount using the corrected baseline length, thereby increasing the An accurate defocus amount can be acquired.

  In this embodiment, the description has been made on the assumption that one side of the light bundle has no light vignetting. However, when the light vignetting is symmetric, the pseudo-F value defined by the symmetric light vignetting is used for the pupil diameter of the imaging optical system. Calculate with In order to obtain the pseudo F value, first, the exit pupil distance change amount is a specified value with respect to the exit pupil distance in the ideal state (the state without optical vignetting) based on the exit pupil distance change information of the imaging optical system with respect to the image height change. An image height position range that does not exceed is detected. Further, the image height position close to the image height position where focus detection is performed is determined from the image height range, and the peripheral light amount ratio at the image height determined from the peripheral light amount ratio information stored in advance is calculated. Then, a pseudo F value is obtained from the calculated peripheral light amount ratio, a pupil radius H corresponding to the pseudo F value is obtained, and can be used as a reference amount for determining the asymmetric optical vignetting amount.

  An example of the processing will be described with reference to FIG. FIG. 9 is a graph showing the relationship between the exit pupil distance, the peripheral light amount ratio, and the image height. In FIG. 9, using the exit pupil distance information 107 and the peripheral light amount ratio information 108, the exit pupil distance change state information indicating the change in the exit pupil distance with respect to the change in the image height and the peripheral light amount change with respect to the change in the image height are shown. The peripheral light ratio change information is graphed.

  This information is defined using data stored in the storage unit of the lens apparatus 100 as the exit pupil distance information 107 and the peripheral light amount ratio information 108, and corresponds to the F value for which the current imaging optical system is set. Then, the exit pupil distance in the vicinity of the image height center is set to an ideal exit pupil distance Po0 in FIG. 8, and the threshold value of the exit pupil distance change rate with respect to the exit pupil distance Po0 is assumed to be 10%. Assume that an asymmetric vignetting occurs that causes the accuracy of the baseline length to fall in the range. Hereinafter, description will be made assuming that focus detection processing is performed at an image height of 20 mm.

  First, the camera-side CPU 169 determines that the position exceeding the threshold of 10% is the position of the image height of 15 mm from the relationship of the exit pupil distance change to the image height change. Subsequently, the camera side CPU 169 determines the peripheral light amount ratio at the image height of 15 mm based on the peripheral light amount change information with respect to the image height change as shown in the lower graph of FIG. 9, and from the obtained peripheral light amount ratio. A pseudo F value is obtained. Here, the exit pupil position at an image height of 20 mm is defined as an exit pupil distance Po1 deviating from the ideal state. From the change in the exit pupil distance, it can be seen that the exit pupil distance decreases as the image height increases. For this reason, as described with reference to FIG. 6, the asymmetric optical vignetting can be determined to be a state in which the vignetting of the upper line of the light beam becomes large. Therefore, by performing the processing described with reference to FIG. 8A, it is possible to acquire highly accurate baseline length information even when large vignetting occurs.

  In the above, when asymmetric optical vignetting has occurred, it has been explained that focusing is performed by obtaining highly accurate baseline length information. However, even if the obtained baseline length information is used to determine the reliability of focusing. Good. For example, when the base line length obtained in a situation where the peripheral light amount and the exit pupil distance change tendency due to extremely asymmetric optical vignetting can be seen is smaller than a specified value, the equations (2-1) and (2-2) ), The defocus amount calculated with a slight error in the baseline length changes greatly. In such a case, for example, a processing method such as changing the focus detection method to a contrast detection method or changing the focus detection position to a position where there is no problem may be selected. In this case, the camera-side CPU 169 functions as a determination unit that determines the reliability of focus detection based on the corrected baseline length information.

  According to the present embodiment, there is no enormous baseline length information for each imaging optical system with respect to the problem that an accurate defocus amount cannot be obtained because the baseline length changes due to ray vignetting of the imaging optical system. In both cases, the baseline length can be corrected with a small amount of information. As a result, a highly accurate focusing operation is possible.

  Next, a process for performing focus control (focus control) of the image pickup optical system by performing focus detection using the image pickup apparatus of the present embodiment will be described with reference to FIG. FIG. 10 is a flowchart of focus detection and focus control in this embodiment. Here, it is assumed that a state in which a replaceable imaging optical system (interchangeable lens) is attached and a focus detection operation is started is an initial state. Each step in FIG. 10 is mainly executed by each unit based on a command from the camera CPU 169.

  First, in step S101, the camera side CPU 169 (signal acquisition unit 169a) acquires signals (focus detection signals) from a plurality of photoelectric conversion units of the image sensor 158. Subsequently, in step S102, the camera-side CPU 169 acquires F-number information of the imaging optical system at the time of focus detection and position information (coordinate information) of the focus detection pixel on the image sensor 158 that performs focus detection. Subsequently, in step S103, the camera side CPU 169 (calculation unit 169b) performs correlation calculation using the focus detection signal acquired in step S101, and calculates an image shift amount. Subsequently, in step S104, the camera side CPU 169 outputs exit pupil information (exit pupil) corresponding to the F value obtained in step S102 from the exit pupil distance information 107 of the imaging optical system stored in the storage unit of the lens apparatus 100. Get distance information). At that time, the camera-side CPU 169 collectively obtains exit pupil distance information at a focus detection position that is closer to the image sensor center position (center image height) than the focus detection position (peripheral image height).

  Subsequently, in step S105, the camera-side CPU 169 obtains peripheral light amount information (peripheral light amount ratio information) corresponding to the F value (F value of the attached lens device 100) acquired in step S102, as in step S104. Collect from the central image height to the peripheral image height. Subsequently, in step S106, the camera-side CPU 169 creates exit pupil distance change information (exit pupil position change information) based on the exit pupil distance information acquired in step S104. At this time, information considered to be insufficient can be compensated by performing an interpolation operation. Further, a polynomial approximate expression may be used for the change state of the exit pupil distance (exit pupil position).

  Subsequently, in step S107, the vignetting state acquisition unit 164 uses the peripheral light amount ratio information at the focus detection position acquired in step S105 and the exit pupil distance change information acquired in step S106 to detect the vignetting state (optical). Vignetting state) is detected (acquired). The vignetting state acquisition means 164 determines the optical vignetting state from the peripheral light amount ratio at the image height position close to the focus detection position (image height position) in the image height range where the exit pupil distance does not change by a predetermined amount from the image height center. To detect. The vignetting state acquisition unit 164 acquires a pseudo F value based on the vignetting state. Here, when the camera-side CPU 169 determines that the exit pupil distance has changed at the current focus detection position, the vignetting state acquisition unit 164 determines that asymmetric optical vignetting has occurred. At this time, the vignetting state acquisition unit 164 similarly estimates the asymmetric optical vignetting (optical vignetting amount) using the method described with reference to FIG. 8 and acquires two pseudo F values.

  Subsequently, in step S108, the baseline length information acquisition unit 165 acquires first baseline length information and second baseline length information corresponding to each of the two pseudo F values. When the vignetting state acquisition unit 164 determines that there is no asymmetric optical vignetting, the first baseline length information and the second baseline length information that are the same value may be acquired from one pseudo F value in step S108. Subsequently, in step S109, the baseline length correction unit 166 (correction unit) averages the first baseline length information and the second baseline length information acquired in step S108, and corrects the baseline length information. Thereby, even if asymmetric optical vignetting occurs, highly accurate baseline length information can be acquired.

  Subsequently, in step S110, the camera side CPU 169 (calculating unit 169b) calculates a defocus amount based on the baseline length information corrected in step S109 and the image shift amount acquired in step S103. The baseline length information used at this time is corrected in consideration of asymmetrical light vignetting of the imaging optical system. For this reason, it is possible to calculate a defocus amount that is more accurate than the defocus amount calculated using the uncorrected baseline length information.

  Subsequently, in step S111, the camera-side CPU 169 determines whether or not the defocus amount acquired in step S110 is within a prescribed defocus range in which it is determined that the image is in focus. If the camera-side CPU 169 determines that the camera is in focus, the series of focus detection and focus control (this flow) ends.

  On the other hand, if it is determined in step S111 that the subject is not in focus (is not in focus), the process proceeds to step S112. In step S112, the camera side CPU 169 (focus drive amount determination means 170) calculates a focus drive amount for the imaging optical system to be in focus based on the defocus amount acquired in step S110. Subsequently, in step S113, the lens side CPU 104 (focus drive unit 105) performs focus drive using the focus drive amount based on a command from the camera side CPU 169 (focus control unit). That is, the camera side CPU 169 performs focus control based on the corrected baseline length information. Then, returning to step S101, focus detection and focus control (steps S101 to S111) are repeated until the in-focus state is obtained.

  Thus, in the present embodiment, the control device includes the signal acquisition unit 169a, the correction unit (baseline length correction unit 166), and the calculation unit 169b. The signal acquisition unit 169a includes a first signal (first focus detection signal, first subpixel signal) and a second signal (second focus detection signal, second signal) corresponding to light beams that pass through different pupil regions of the imaging optical system. Subpixel signal) is acquired. The correction unit (baseline length correction unit 166) corrects the baseline length information based on the exit pupil information corresponding to the focus detection position (image height). The calculating unit 169b calculates the defocus amount based on the image shift amount obtained from the correlation value between the first signal and the second signal and the corrected baseline length information.

  Preferably, the exit pupil information includes information related to the exit pupil distance. The correcting unit corrects the baseline length information based on a change in the exit pupil distance according to the focus detection position. More preferably, the control device includes baseline length acquisition means (baseline length information acquisition means 165) for acquiring baseline length information. The baseline length acquisition unit acquires baseline length information based on the F value of the imaging optical system at the time of focus detection and the exit pupil distance according to the focus detection position.

  Preferably, the control device includes vignetting information acquisition means (vignetting state acquisition means 164) that acquires vignetting information based on a change in exit pupil information according to the focus detection position. The correcting means corrects the baseline length information based on the vignetting information. More preferably, the vignetting information acquisition means acquires the vignetting information as the exit pupil information based on the relationship between the change in the focus detection position and the change in the exit pupil distance. Preferably, the vignetting information acquisition unit acquires the vignetting information using the exit pupil information (exit pupil distance information 107) and the peripheral light amount information (the peripheral light amount ratio information 108). Preferably, the correction unit corrects the baseline length information using the exit pupil information stored in the lens apparatus 100. Preferably, the vignetting information includes information related to a pupil-shaped asymmetric vignetting component.

  As described above, in this embodiment, by using the exit pupil distance information, it is possible to acquire high-precision baseline length information even when asymmetric optical vignetting occurs, and it is possible to perform high-precision focus detection. .

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

  According to the present 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 detection with high accuracy even when asymmetric optical vignetting occurs.

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

  The present embodiment is applicable to an imaging apparatus such as a video camera in addition to an imaging apparatus such as a single-lens reflex camera or a compact digital camera using an imaging element having focus detection pixels. The present embodiment can also be applied to, for example, an imaging apparatus that performs hybrid AF in which phase difference detection type focus detection (phase difference AF) and contrast detection type focus detection (contrast AF) are combined. In this case, the imaging apparatus includes a focus detection unit that performs focus detection by a contrast detection method using an imaging element. Such an imaging apparatus can selectively use phase difference AF or contrast AF, or a combination thereof, depending on the situation.

166 Baseline length correction means (correction means)
169a Signal acquisition means 169b calculation means

Claims (15)

Signal acquisition means for acquiring a first signal and a second signal corresponding to light beams passing through different pupil regions of the imaging optical system;
Correction means for correcting the baseline length information based on the exit pupil information corresponding to the focus detection position;
And a calculating means for calculating a defocus amount based on the image shift amount obtained from the correlation value between the first signal and the second signal and the corrected baseline length information. Control device. The exit pupil information includes information regarding exit pupil distance,
The control device according to claim 1, wherein the correction unit corrects the baseline length information based on a change in the exit pupil distance according to the focus detection position. It further has a baseline length acquisition means for acquiring the baseline length information,
The baseline length acquisition unit acquires the baseline length information based on an F value of the imaging optical system at the time of focus detection and the exit pupil distance according to the focus detection position. Item 3. The control device according to Item 2. Vignetting information acquisition means for acquiring vignetting information based on a change in the exit pupil information according to the focus detection position;
The control device according to claim 1, wherein the correction unit corrects the baseline length information based on the vignetting information.   5. The control according to claim 4, wherein the vignetting information acquisition unit acquires the vignetting information as the exit pupil information based on a relationship between a change in the focus detection position and a change in the exit pupil distance. apparatus.   The control device according to claim 4 or 5, wherein the vignetting information acquisition unit acquires the vignetting information using the exit pupil information and peripheral light amount ratio information.   7. The control device according to claim 4, wherein the vignetting information includes information related to an asymmetric vignetting component of a pupil shape.   The control device according to claim 1, further comprising a determination unit that determines the reliability of focus detection based on the corrected baseline length information.   9. The control device according to claim 1, further comprising a focus control unit that performs focus control based on the corrected baseline length information. An imaging device having a first photoelectric conversion unit and a second photoelectric conversion unit that receive light beams passing through different pupil regions of the imaging optical system;
Signal acquisition means for acquiring a first signal and a second signal respectively corresponding to output signals from the first photoelectric conversion unit and the second photoelectric conversion unit;
Correction means for correcting the baseline length information based on the exit pupil information corresponding to the focus detection position;
And a calculating means for calculating a defocus amount based on the image shift amount obtained from the correlation value between the first signal and the second signal and the corrected baseline length information. An imaging device.   The image pickup device includes the first photoelectric conversion unit and the second photoelectric conversion unit with respect to one microlens, and the microlens is two-dimensionally arranged. The imaging device described.   The imaging device according to claim 10, wherein the correction unit corrects the baseline length information using the exit pupil information stored in the lens device. Obtaining a first signal and a second signal corresponding to light beams passing through different pupil regions of the imaging optical system;
Correcting baseline length information based on exit pupil information corresponding to the focus detection position;
And a step of calculating a defocus amount based on the image shift amount obtained from the correlation value between the first signal and the second signal and the corrected baseline length information. Control method. Obtaining a first signal and a second signal corresponding to light beams passing through different pupil regions of the imaging optical system;
Correcting baseline length information based on exit pupil information corresponding to the focus detection position;
Causing the computer to execute a step of calculating a defocus amount based on an image shift amount obtained from a correlation value between the first signal and the second signal and the corrected baseline length information. A featured program.   A storage medium storing the program according to claim 14.