JP2017097142A - Control device, imaging apparatus, control method, program, and storage medium - Google Patents

Abstract

A control device capable of detecting a focus with high accuracy is provided.
A control device (121) includes a first photoelectric conversion unit group (301, 302, 303) among a plurality of photoelectric conversion units (301, 302, 303) that receive light beams that pass through mutually different pupil partial regions of an imaging optical system. 301, 303) a first focus detection unit (121a) that performs focus detection based on the first evaluation value of the signal acquired from the first and second photoelectric conversion units different from the first photoelectric conversion unit group. A second focus detection unit (121b) that performs focus detection based on a second evaluation value calculated using a signal acquired from the photoelectric conversion unit group (301, 302, 303).
[Selection] Figure 2

Description

  The present invention relates to an imaging apparatus that performs autofocus control based on a signal obtained from an imaging element.

  Conventionally, as a focus detection method, a method of performing focus detection by a phase difference method based on a correlation value of a signal obtained from an image sensor (focus detection method by a phase difference method) is known. Further, a method of performing focus detection based on a contrast evaluation value obtained from a signal obtained from an image sensor (focus detection method using a contrast method) is known.

  Patent Document 1 discloses an imaging device capable of high-speed focus control with high focusing accuracy by determining a focus evaluation value of a subject based on a focus position obtained by a correlation calculation unit and a contrast evaluation unit. Yes. Patent Document 2 discloses an imaging device in which a plurality of pixels in which the relative position between a microlens and a photoelectric conversion unit is offset are two-dimensionally arranged.

JP 2013-025246 A Patent No. 3592147

  However, Patent Document 1 does not describe an appropriate selection method of pixels (focus detection pixels) used in each of phase difference type focus detection and contrast type focus detection. For this reason, for example, when focus detection is performed by the contrast evaluation unit of Patent Document 1 using the focus detection signal from the imaging device disclosed in Patent Document 2, the focus detection range is narrow, so that the focus detection accuracy is reduced. End up.

  Therefore, the present invention provides a control device, an imaging device, a control method, a program, and a storage medium capable of highly accurate focus detection.

  A control device according to an aspect of the present invention provides a first signal obtained from a first photoelectric conversion unit group among a plurality of photoelectric conversion units that receive light beams that pass through different pupil partial regions of an imaging optical system. Calculated using a first focus detection unit that performs focus detection based on an evaluation value, and a signal acquired from a second photoelectric conversion unit group different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. And second focus detection means for performing focus detection based on the second evaluation value.

  An imaging device according to another aspect of the present invention includes: an imaging device having a plurality of photoelectric conversion units that receive light beams that pass through different pupil partial regions of the imaging optical system; and a first of the plurality of photoelectric conversion units. A first focus detection unit that performs focus detection based on a first evaluation value of a signal acquired from one photoelectric conversion unit group, and a second of the plurality of photoelectric conversion units that is different from the first photoelectric conversion unit group. Second focus detection means for performing focus detection based on a second evaluation value calculated using a signal acquired from the photoelectric conversion unit group.

  According to another aspect of the present invention, there is provided a control method, wherein a signal acquired from a first photoelectric conversion unit group among a plurality of photoelectric conversion units that receive light beams that pass through different pupil partial regions of an imaging optical system. A first focus detection step based on one evaluation value, and a signal obtained from a second photoelectric conversion unit group different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. And performing a second focus detection based on the second evaluation value.

  A program according to another aspect of the present invention provides a first signal obtained from a first photoelectric conversion unit group among a plurality of photoelectric conversion units that receive light beams that pass through different pupil partial regions of an imaging optical system. Calculated using a step of performing first focus detection based on the evaluation value and a signal obtained from a second photoelectric conversion unit group different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. And causing the computer to execute a second focus detection based on the second evaluation value.

  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.

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 structure figure of an image sensor in this embodiment. It is explanatory drawing of the image pick-up element and pupil division function in this embodiment. It is explanatory drawing of the image pick-up element and pupil division function in this embodiment. FIG. 6 is a relationship diagram between a defocus amount and an image shift amount in the present embodiment. It is a flowchart which shows the 1st focus detection process in this embodiment. It is explanatory drawing of the shading by the pupil shift | offset | difference of the focus detection signal in this embodiment. It is explanatory drawing of the refocus process in this embodiment. It is a flowchart which shows the 2nd focus detection process in this embodiment. It is explanatory drawing of the refocus possible range in this embodiment. It is a flowchart which shows the focus control in this embodiment.

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

[overall structure]
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 100 (camera) in the present embodiment. The imaging apparatus 100 is a digital camera system that includes a camera body and an interchangeable lens (imaging optical system) that can be attached to and detached from the camera body. 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.

  The first lens group 101 is disposed in the forefront (subject side) of the plurality of lens groups constituting the photographing lens (imaging optical system), and can advance and retreat in the direction of the optical axis OA (optical axis direction). The lens barrel is held in a state. The aperture / shutter 102 (aperture) adjusts the aperture to adjust the amount of light during shooting, and also functions as an exposure time adjustment shutter during still image shooting. The second lens group 103 has a zoom function of moving forward and backward in the optical axis direction integrally with the diaphragm / shutter 102 and performing a zooming operation in conjunction with the forward / backward movement of the first lens group 101. The third lens group 105 is a focus lens group that performs focus adjustment (focus operation) by moving back and forth in the optical axis direction. The optical low-pass filter 106 is an optical element for reducing false colors and moire in the captured image.

  The image sensor 107 photoelectrically converts a subject image (optical image) formed through an imaging optical system and outputs an image signal. The imaging element 107 is constituted by, for example, a CMOS sensor or a CCD sensor and its peripheral circuit, and is disposed on the imaging surface of the imaging optical system. As the image sensor 107, for example, a two-dimensional single-plate color sensor in which a Bayer array primary color mosaic filter is formed on-chip on a light receiving pixel having m pixels in the horizontal direction and n pixels in the vertical direction is used. It is done.

  The zoom actuator 111 performs a zooming operation by moving the first lens group 101 and the second lens group 103 along the optical axis direction by rotating (driving) a cam cylinder (not shown). The aperture shutter actuator 112 controls the aperture diameter of the aperture / shutter 102 to adjust the amount of light (photographing light amount), and also controls the exposure time during still image shooting. The focus actuator 114 adjusts the focus by moving the third lens group 105 in the optical axis direction.

  The electronic flash 115 is an illumination device used to illuminate a subject. As the electronic flash 115, a flash illumination device including a xenon tube or an illumination device including an LED (light emitting diode) that continuously emits light is used. The AF auxiliary light unit 116 projects an image of a mask having a predetermined opening pattern onto a subject via a light projection lens. As a result, the focus detection capability for a dark subject or a low-contrast subject can be improved.

  The CPU 121 is a control device (control means) that performs various controls of the imaging device 100. The CPU 121 includes a calculation unit, a ROM, a RAM, an A / D converter, a D / A converter, a communication interface circuit, and the like. The CPU 121 reads and executes a predetermined program stored in the ROM, thereby driving various circuits of the imaging apparatus 100 and controlling a series of operations such as focus detection (AF), shooting, image processing, or recording. To do.

  The CPU 121 includes first focus detection means 121a, second focus detection means 121b, and focus control means 121c. The first focus detection unit 121a includes a first photoelectric conversion unit group (photoelectric conversion unit 301, among the plurality of photoelectric conversion units 301, 302, and 303 that receive light beams that pass through different pupil partial regions of the imaging optical system. 303) focus detection is performed based on the first evaluation value of the signal acquired from step 303). The second focus detection unit 121b is calculated using a signal acquired from a second photoelectric conversion unit group (photoelectric conversion units 301, 302, and 303) different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. Focus detection is performed based on the second evaluation value. The focus control unit 121c drives the third lens group 105 (focus lens) included in the imaging optical system.

  The electronic flash control circuit 122 controls lighting of the electronic flash 115 in synchronization with the photographing operation. The auxiliary light driving circuit 123 performs lighting control of the AF auxiliary light unit 116 in synchronization with the focus detection operation. The image sensor driving circuit 124 controls the image capturing operation of the image sensor 107, A / D converts the acquired image signal, and transmits it to the CPU 121. The image processing circuit 125 performs processing such as γ (gamma) conversion, color interpolation, or JPEG (Joint Photographic Experts Group) compression of the image data output from the image sensor 107.

  The focus drive circuit 126 performs focus adjustment by driving the focus actuator 114 based on the focus detection result and moving the third lens group 105 along the optical axis direction. The aperture shutter drive circuit 128 drives the aperture shutter actuator 112 to control the aperture diameter of the aperture / shutter 102. The zoom drive circuit 129 drives the zoom actuator 111 according to the zoom operation of the photographer.

  The display 131 includes, for example, an LCD (Liquid Crystal Display). The display 131 displays information related to the shooting mode of the imaging apparatus 100, a preview image before shooting, a confirmation image after shooting, a focus state display image at the time of focus detection, and the like. The operation unit 132 (operation switch group) includes a power switch, a release (shooting trigger) switch, a zoom operation switch, a shooting mode selection switch, and the like. The release switch has a two-stage switch in a half-pressed state (a state where SW1 is ON) and a full-pressed state (a state where SW2 is ON). The recording medium 133 is, for example, a flash memory that can be attached to and detached from the imaging apparatus 100, and records captured images (image data).

[Image sensor]
Next, with reference to FIG. 2 and FIG. 3, the pixel arrangement and the pixel structure of the image sensor 107 in this embodiment will be described. FIG. 2 is a pixel array diagram of the image sensor 107 and shows an array of pixels (imaging pixels) in a range of 6 columns × 4 rows including the imaging pixels and focus detection pixels. In FIG. 2, the right side of the paper is the + X direction, the upper side of the paper is the + Y direction, and the front side of the paper is the + Z direction. In the present embodiment, an imaging device including an imaging pixel and a focus detection pixel as shown in FIG. 2 will be described, but the present invention is not limited to this. For example, the present embodiment can also be applied to an image pickup element that is divided into a plurality of pixels and is used as one image pickup pixel and a focus detection pixel as disclosed in JP-A-2002-250860.

  As shown in FIG. 2, the image sensor 107 has a pixel group 200 of 2 columns × 2 rows and a pixel group 201 of 2 columns × 2 rows, respectively. The pixel group 200 of 2 columns × 2 rows includes a pixel 200R having an R (red) spectral sensitivity at the upper left, a pixel 200G having a G (green) spectral sensitivity at the upper right and lower left, and a B (blue) spectral at the lower right. The pixel 200B having sensitivity is included. In the present embodiment, the pixels 200R, 200G, and 200G are referred to as imaging pixels, respectively.

  A pixel group 201 of 2 columns × 2 rows includes focus detection pixels 201Gs (Gs1, Gs2, Gs3) having G (green) spectral sensitivity at the upper left, and pixels having G (green) spectral sensitivity at the upper right and lower left, respectively. Each pixel 201B has a spectral sensitivity of 201G and B (blue) in the lower right. An opening is formed in the focus detection pixel 201Gs (Gs1, Gs2, Gs3), and the position of the opening changes according to the position in the X direction. In other words, the focus detection pixels Gs1, Gs2, and Gs3 have openings formed at different positions in the X direction. In the present embodiment, the focus detection pixel 201Gs is described as being divided into three focus detection pixels Gs1, Gs2, and Gs3 (the number of divided pixels is 3), but is not limited thereto. Even if the number of divisions of the focus detection pixel 201Gs is larger than 3, the present embodiment can be applied. In the present embodiment, the focus detection pixel 201Gs in the upper left is described as having a spectral sensitivity of G (green), but is not limited thereto. For example, the focus detection pixel 201Gs may be a transparent film instead of having a spectral sensitivity of G (green).

  As shown in FIG. 2, the image sensor 107 is configured so that a large number of pixel groups 201 and pixel groups 200 of 2 columns × 2 rows are arranged on the imaging surface, and an imaging signal and a focus detection signal can be acquired.

  FIG. 3 is a pixel structure diagram of the image sensor 107. FIG. 3A shows a plan view (viewed from the + z direction) of the imaging pixels RGB (for example, the pixels 200R, 200G, and 200B) and the focus detection pixels Gs1, Gs2, and Gs3 of the imaging element 107. FIG. 3B shows cross-sectional views (viewed from the −y direction) along lines AA, aa, bb, and cc in FIG.

  As shown in FIG. 3B, the imaging pixel RGB and the focus detection pixels Gs1, Gs2, and Gs3 respectively have a microlens 305 for condensing incident light from the + Z side to the light receiving side of each pixel, and incident light. A color filter 306 for splitting is formed. In addition, photoelectric conversion units 300, 301, 302, and 303 are formed below the microlens 305 and the color filter 306 in the imaging pixel RGB and the focus detection pixels Gs1, Gs2, and Gs3, respectively. As necessary, the color filters of the focus detection pixels Gs1, Gs2, and Gs3 may have different spectral transmittances or may be omitted.

  As shown in FIGS. 3A and 3B, the photoelectric conversion units 301, 302, and 303 of the focus detection pixels Gs1, Gs2, and Gs3 are smaller than the photoelectric conversion unit 300 of the image sensor RGB. In the present embodiment, since the image sensor RGB corresponds to the division into three focus detection pixels Gs1, Gs2, and Gs3, the sizes of the photoelectric conversion units 301, 302, and 303 are 3 of the photoelectric conversion unit 300, respectively. It becomes 1 / minute. In addition, the photoelectric conversion units 301, 302, and 303 of the focus detection pixels Gs1, Gs2, and Gs3 are formed to be biased in the −x direction, the center, and the + x direction, respectively.

  In the photoelectric conversion units 300, 301, 302, and 303, pairs of electrons and holes are generated according to the amount of received light, and after they are separated by the depletion layer, negatively charged electrons are accumulated in the n-type layer. . On the other hand, the holes are discharged to the outside of the image sensor 107 through a p-type layer connected to a constant voltage source (not shown). Electrons accumulated in the n-type layers of the photoelectric conversion units 300, 301, 302, and 303 are transferred to a capacitance unit (FD) through a transfer gate and converted into a voltage signal.

  Next, the pupil division function of the image sensor 107 will be described with reference to FIG. FIG. 4 is an explanatory diagram of the pupil division function of the image sensor 107, and shows a state of pupil division in one pixel (image pickup pixel and focus detection pixel). 4 is a cross-sectional view of the pixel structure shown in FIG. 3A taken along the lines AA, aa, bb, and cc from the + y side, and an imaging optical system. The top view which looked at the exit pupil plane of this from the -Z side is shown, respectively. The plan view in FIG. 4 shows the sectional view in FIG. 4 rotated 90 degrees around the X axis. In FIG. 4, in order to correspond to the coordinate axis of the exit pupil plane, the x-axis and y-axis in the cross-sectional view are inverted with respect to the x-axis and y-axis in FIG.

  The imaging pixel RGB is shown on the left side of FIG. The pupil region 500 has a substantially conjugate relationship with the light receiving surface of the photoelectric conversion unit 300 and the microlens 305, and indicates a pupil region that can be received by the imaging pixels RGB. Further, the pupil partial areas 501, 502, and 503 of the focus detection pixels Gs1, Gs2, and Gs3 respectively have light receiving surfaces of the photoelectric conversion units 301, 302, and 303 whose centroids are biased in the −x direction, the center, and the + x direction. The microlenses have a substantially conjugate relationship. Pupil partial areas 501, 502, and 503 indicate pupil partial areas that can be received by the focus detection pixels Gs1, Gs2, and Gs3. For this reason, the center of gravity of the pupil partial regions 501, 502, and 503 of the focus detection pixels Gs1, Gs2, and Gs3 is deviated in the + X direction, the center, and the −X direction on the pupil plane, respectively. As described above, the imaging element 107 includes the microlens 305 corresponding to each of the plurality of photoelectric conversion units. The photoelectric conversion unit 301 (first photoelectric conversion unit) is biased in the −x direction (first direction) with respect to the center of the microlens 305. The photoelectric conversion unit 303 (third photoelectric conversion unit) is biased in the + x direction (second direction opposite to the first direction) with respect to the center of the microlens 305.

  FIG. 5 is an explanatory diagram of the image sensor 107 and the pupil division function. Light beams that have passed through different pupil partial regions 501, 502, and 503 among the pupil regions of the imaging optical system are incident on the imaging surface 800 of the imaging device 107 at different angles to the pixels of the imaging device 107. That is, the light fluxes that have passed through the pupil partial areas 501, 502, and 503 are received by the focus detection pixels Gs1, Gs2, and Gs3 divided into three, respectively.

  As described above, in the present embodiment, the imaging element 107 includes a plurality of imaging pixels RGB and focus detection pixels Gs1, Gs2, and Gs3. The imaging pixels RGB receive the total luminous flux that passes through the pupil region of the imaging optical system. The focus detection pixels Gs1, Gs2, and Gs3 receive a light beam that passes through the pupil partial region of the imaging optical system (a part of the total light beam that passes through the pupil region). The imaging apparatus 100 collects the light reception signals of the focus detection pixels Gs1, Gs2, and Gs3, generates a focus detection signal, and performs focus detection. Further, the imaging apparatus 100 uses an imaging signal of the imaging pixels RGB and an interpolation signal calculated by interpolating signals corresponding to the positions of the focus detection pixels Gs1, Gs2, and Gs3, and has an image with a resolution of N effective pixels. A signal (captured image) is generated.

[Relationship between defocus amount and image shift amount]
Next, referring to FIG. 6, the relationship between the defocus amount and the image shift amount of the focus detection signal SGs1 acquired from the focus detection pixel Gs1 of the image sensor 107 and the focus detection signal SGs3 acquired from the focus detection pixel Gs3. Will be described. FIG. 6 is a relationship diagram between the defocus amount d and the image shift amount p. In FIG. 6, the image sensor 107 is disposed on the imaging surface 800, and the exit pupil of the imaging optical system is divided into three pupil partial areas 501, 502, and 503 as in FIGS. 4 and 5. It is shown. FIG. 6 shows a pixel row including focus detection pixels Gs1 and Gs3 of the image sensor 107.

  The defocus amount d is the distance from the imaging position of the subject to the imaging surface 800 | d |, the negative pin state where the imaging position is closer to the subject than the imaging surface 800 (d <0), and imaging. A rear pin state in which the position is on the opposite side of the subject from the imaging surface 800 is defined as a positive sign (d> 0). A defocus amount d = 0 is established in a focused state where the imaging position of the subject is on the imaging surface 800 (focus position). In FIG. 6, a subject 801 in a focused state (d = 0) and a subject 802 in a front pin state (d <0) are shown. The front pin state (d <0) and the rear pin state (d> 0) are collectively referred to as a defocus state (| d |> 0).

  In the front pin state (d <0), the luminous flux that has passed through the pupil partial area 501 (or the pupil partial area 503) out of the luminous flux from the subject 802 is condensed once. Thereafter, the light beam spreads over a width Γ1 (Γ3) centered on the gravity center position G1 (G3) of the light beam, and becomes a blurred image on the imaging surface 800. The blurred image is received by the focus detection pixel Gs1 (focus detection pixel Gs3) arranged in the image sensor 107, and a focus detection signal SGs1 (focus detection signal SGs3) is generated. Therefore, the focus detection signal SGs1 (focus detection signal SGs3) is recorded as a subject image in which the subject 802 is blurred by the width Γ1 (Γ3) at the gravity center position G1 (G3) on the imaging surface 800. The blur width Γ1 (Γ3) of the subject image increases approximately proportionally as the magnitude | d | of the defocus amount d increases. Similarly, the magnitude | p | of the subject image displacement amount p (= difference G1-G3 in the center of gravity of the light beam) between the focus detection signal SGs1 and the focus detection signal SGs3 is also the magnitude of the defocus amount d. As | d | increases, it generally increases in proportion. The same applies to the rear pin state (d> 0), but the image shift direction of the subject image between the focus detection signal SGs1 and the focus detection signal SGs3 is opposite to the front pin state.

[Focus detection]
Next, focus detection in this embodiment will be described. The imaging apparatus 100 (first focus detection unit 121a) of the present embodiment performs phase difference type focus detection (first focus detection). The imaging apparatus 100 (second focus detection unit 121b) performs focus detection (second focus detection) based on the refocus principle (refocus method) based on the relationship between the defocus amount and the image shift amount. . In the present embodiment, the imaging apparatus 100 performs first focus detection to perform focus adjustment from the large defocus state to the small defocus state, and performs focus adjustment from the small defocus state to the vicinity of the best focus position. Second focus detection is performed.

  In the present embodiment, the first focus detection unit 121a selects a focus detection pixel (photoelectric conversion unit) included in the first focus detection pixel group (first photoelectric conversion unit group). The second focus detection unit 121b selects focus detection pixels (photoelectric conversion units) included in the second focus detection pixel group (second photoelectric conversion unit group). That is, the pixels (focus detection pixels) used for focus detection differ depending on the focus detection method (phase difference method or refocus method). Here, the selection method of the first focus detection pixel group and the second focus detection pixel group will be described using the imaging element 107 of the present embodiment in which the pupil is divided into three as an example.

  First, as shown in FIG. 2, the first focus detection pixel group (first photoelectric conversion unit group) selected by the first focus detection unit 121a that performs phase difference type focus detection is the focus detection pixel Gs1 (i ), Gs3 (k). In the first focus detection, as described above, the separation of the focus detection signals to be compared becomes better as the interval (image shift amount p) between the gravity center positions G1 (G3) on the imaging surface 800 in FIG. Thus, the first focus detection means can perform focus detection with high accuracy. Therefore, in the present embodiment, the first focus detection unit selects the focus detection pixels Gs1 (i) and Gs3 (k) as the first focus detection pixel group. In the present embodiment, a system in which the pupil is divided into three parts is described, but the number of pupil divisions may be larger than three.

  For example, consider a system in which the pupil is divided into five. At this time, there are focus detection pixels Gs1 (i), Gs2 (j), Gs3 (k), Gs4 (l), and Gs5 (m) whose opening positions are different in order. At this time, the focus detection pixels selected as the first focus detection pixel group are preferably the focus detection pixels Gs1 (i) and Gs5 (m) at the end so that the interval (image shift amount p) is wide. . Further, focus detection pixels Gs1 (i), Gs2 (j), Gs4 (l), and Gs5 (m) may be selected as the first focus detection pixel group. In this case, focus detection signals obtained by synthesizing a plurality of selected focus detection pixels, such as the focus detection pixels Gs1 (i) + Gs2 (j) and the focus detection pixels Gs4 (l) + Gs5 (m), may be used.

  Subsequently, as shown in FIG. 2, the second focus detection pixel group (second photoelectric conversion unit group) selected by the second focus detection unit 121b that performs refocus focus detection is the focus detection pixel Gs1 ( i), Gs2 (j), Gs3 (k). The second focus detection unit 121b relatively shifts the focus detection signals SGs1 (i), SGs2 (j), and SGs3 (k) from the pupil partial areas 501, 502, and 503, and then adds signals (summation signals). Is generated. For this reason, the addition signal is a signal obtained by adding (summing up) the luminous fluxes from the entire pupil region, and corresponds to a signal equivalent to the imaging signal RGB. Therefore, the detection focus position (position where the defocus amount is 0) calculated by the second focus detection of the refocus method and the best focus position of the imaging signal (MTF peak position of the imaging signal) are approximately the same. Highly accurate focus detection is possible. In this embodiment, the effective depth of field is increased by dividing the pupil into a plurality of three or more.

  In the present embodiment, the image pickup element 107 including the image pickup pixel and the focus detection pixel as shown in FIG. 2 is described. However, the present invention is not limited to this. For example, the present embodiment can also be applied to an image sensor in which one pixel is divided into a plurality of parts as disclosed in JP-A-2002-250860. In this case, since one pixel serves as both an imaging pixel and a focus detection pixel, the pixels included in the first focus detection pixel group and the second focus detection pixel group are the same. However, since the light beam from the exit pupil is divided into a plurality of light beams and received, the light receiving regions selected in the pixels are different between the first focus detection pixel group and the second focus detection pixel group.

[First focus detection of phase difference method]
Next, phase difference type first focus detection will be described. The first focus detection means performs phase difference type focus detection (first focus detection) using focus detection signals SGs1 and SGs3 acquired from the focus detection pixels Gs1 and Gs3 included in the first focus detection pixel group. . The first focus detection means relatively shifts the focus detection signals SGs1 and SGs3 to calculate a correlation amount (first evaluation value) indicating the degree of coincidence of signals, and a shift amount that improves the correlation (signal coincidence). To detect (calculate) an image shift amount. As the defocus amount d of the imaging signal increases, the image shift amount is determined based on the relationship that the image shift amount increases between the focus detection signal SGs1 and the focus detection signal SGs3. The focus is detected by converting it to 1 defocus amount (Def1).

  With reference to FIG. 7, the first focus detection process of the phase difference method will be described. FIG. 7 is a flowchart showing the first focus detection process, and corresponds to step S100 in FIG. Each step in FIG. 7 is mainly executed by the CPU 121 (first focus detection unit 121a) and the image processing circuit 125.

  First, in step S110, the CPU 121 sets a focus detection area including the focus detection pixels of the first focus detection pixel group from the effective pixel areas of the image sensor 107. The CPU 121 generates (acquires) a focus detection signal SGs1 (A image signal) and a focus detection signal SGs3 (B image signal) based on the light reception signal (output signal) of the focus detection pixels included in the set focus detection region. )

  Subsequently, in step S120, the CPU 121 and the image processing circuit 125 perform shading correction processing (optical correction processing) on each of the focus detection signals SGs1 and SGs3. Here, with reference to FIG. 8, the shading by the pupil shift of the focus detection signals SGs1 and SGs3 will be described. FIG. 8 is an explanatory diagram of shading due to pupil shift of the focus detection signals SGs1 and SGs3. Specifically, FIG. 8 illustrates the pupil partial areas 501, 502, and 503 of the focus detection pixels Gs1, Gs2, and Gs3 (first to third focus detection pixels) at the peripheral image height of the image sensor 107 and the imaging optical system. The relationship with the exit pupil 400 is shown.

  FIG. 8A shows a case where the exit pupil distance Dl (distance between the exit pupil 400 and the imaging surface of the image sensor 107) of the imaging optical system is equal to the set pupil distance Ds of the image sensor 107. In this case, the exit pupil 400 of the imaging optical system is substantially equally divided by the pupil partial regions 501, 502, and 503.

  On the other hand, when the exit pupil distance Dl of the imaging optical system is shorter than the set pupil distance Ds of the image sensor 107 as shown in FIG. A pupil shift occurs between the exit pupil 400 and the entrance pupil of the image sensor 107. For this reason, the exit pupil 400 of the imaging optical system is non-uniformly divided into pupils. Similarly, as illustrated in FIG. 8C, when the exit pupil distance Dl of the imaging optical system is longer than the set pupil distance Ds of the imaging element 107, the imaging optical system has a peripheral image height of the imaging element 107. A pupil shift occurs between the exit pupil 400 of the image sensor and the entrance pupil of the image sensor 107. For this reason, the exit pupil 400 of the imaging optical system is non-uniformly divided into pupils. As the pupil division becomes nonuniform at the peripheral image height, the intensities of the focus detection signals SGs1 and SGs3 become nonuniform. For this reason, the intensity | strength of any one of focus detection signal SGs1 and SGs3 becomes large, and the shading which the other intensity | strength becomes small arises.

  In step S120, the CPU 121 determines the shading correction coefficient SHD1 of the focus detection signal SGs1 and the focus detection signal SGs3 according to the image height of the focus detection area, the F value of the imaging lens (imaging optical system), and the exit pupil distance. A shading correction coefficient SHD3 is generated. The CPU 121 (image processing circuit 125) multiplies the focus detection signals SGs1 and SGs3 by the shading correction coefficients SHD1 and SHD3, respectively, and performs shading correction processing (optical correction processing) on the focus detection signals SGs1 and SGs3.

  When performing the first focus detection using the phase difference method, the CPU 121 detects the defocus amount (first defocus amount) based on the correlation (the degree of signal coincidence) between the focus detection signal SGs1 and the focus detection signal SGs3 ( calculate. When shading due to pupil shift occurs, the correlation (the degree of signal coincidence) between the focus detection signal SGs1 and the focus detection signal SGs3 may decrease. Therefore, in the present embodiment, in the first focus detection of the phase difference method, in order to improve the focus detection performance by improving the correlation (signal coincidence) between the focus detection signal SGs1 and the focus detection signal SGs3, It is preferable to perform shading correction processing (optical correction processing).

  Subsequently, in step S130, the CPU 121 and the image processing circuit 125 perform a first filter process on the focus detection signals SGs1 and SGs3. In the present embodiment, focus detection in a large defocus state is performed by phase difference type first focus detection. For this reason, the pass band in the first filter processing is configured to include a low frequency band. If necessary, when performing focus adjustment from the large defocus state to the small defocus state, the pass band of the first filter processing is adjusted (for example, moved to the higher frequency band side) according to the defocus state. Also good.

  Subsequently, in step S140, the CPU 121 (first focus detection unit 121a) performs a first shift process of relatively shifting the focus detection signal SGs1 and the focus detection signal SGs3 after the first filter process in the pupil division direction. Then, the CPU 121 calculates a correlation amount (first evaluation value) representing the degree of coincidence of signals.

Here, the filtered k-th focus detection signal SGs1 is Gs1 (k), the focus detection signal SGs3 is Gs3 (k), and the range of the number k corresponding to the focus detection region is W. Further, the shift amount by the first shift process is s ₁ , and the shift range of the shift amount s ₁ is Γ1. At this time, the correlation amount COR (first evaluation value) is calculated by the following equation (1).

When calculating the correlation amount COR, the shift processing of the shift amount _{s 1,} in correspondence k-th focus detection signal Gs1 and (k) a _{(k-s 1)} th focus detection signal Gs3 _{(k-s 1)} Subtract to generate a shift subtraction signal. Then, the absolute value of the generated shift subtraction signal is calculated, the sum of the numbers k is calculated within the range W corresponding to the focus detection area, and the correlation amount COR (s ₁ ) is calculated. If necessary, the correlation amount (first evaluation value) calculated for each row may be added over a plurality of rows for each shift amount.

  Subsequently, in step S150, the CPU 121 (first focus detection unit 121a) performs a sub-pixel calculation on the correlation amount (first evaluation value), and calculates a real-valued shift amount that minimizes the correlation amount. An image shift amount p1 is obtained. Then, the CPU 121 multiplies the image shift amount p1 by the first conversion coefficient K1 corresponding to the image height of the focus detection area, the F value of the imaging lens (imaging optical system), and the exit pupil distance. The defocus amount Def1 is detected (calculated).

  As described above, in the present embodiment, the CPU 121 (first focus detection unit) performs the filter process and the shift process on each of the focus detection signal SGs1 and the focus detection signal SGs3 during the phase difference type focus detection. A correlation amount is calculated. The CPU 121 detects (calculates) the first defocus amount based on the calculated correlation amount.

[Refocus second focus detection]
Next, the refocus second focus detection will be described. The second focus detection means performs focus detection (second focus detection) using focus detection signals SGs1, SGs2, and SGs3 acquired from the focus detection pixels Gs1, Gs2, and Gs3 included in the second focus detection pixel group. . The second focus detection means relatively shifts and adds (sums) the focus detection signals SGs1, SGs2, and SGs3 to generate a shift addition signal (refocus signal). Then, the second focus detection unit calculates a contrast evaluation value of the generated shift addition signal (refocus signal), estimates the MTF peak position of the imaging signal based on the contrast evaluation value, and outputs a second defocus amount (Def2). ) Is detected (calculated).

  With reference to FIG. 9, the refocus processing in the one-dimensional direction (column direction, horizontal direction) using the focus detection signals SGs1, SGs2, and SGs3 acquired from the image sensor 107 will be described. FIG. 9 is an explanatory diagram of the refocus processing. The imaging surface 800 in FIG. 9 corresponds to the imaging surface 800 shown in FIGS. 5 and 6. In FIG. 9, using the integer i, the focus detection signal SGs1 of the i-th focus detection pixel in the column direction of the image sensor 107 arranged on the imaging surface 800 is schematically shown as Gs1 (i). Similarly, using the integers j and k, the column direction j and the focus detection signals SGs2 and SGs3 of the kth focus detection pixel of the image sensor 107 arranged on the imaging surface 800 are respectively expressed as Gs2 (j) and Gs3 (k ) Schematically (j = i + 1, k = j + 1). In the second focus detection of the present embodiment, the pixel rows of the image sensor in which the focus detection pixels Gs1 (i), Gs2 (j), Gs3 (k) and the image pickup pixels are alternately arranged as in the image pickup surface 800. Is used.

In the present embodiment, the focus detection signals Gs1 (i), Gs2 (j), and Gs3 (k) are all discrete signals every other pixel. The focus detection signal Gs1 (i) is a light reception signal of a light beam incident on the i-th pixel at the principal ray angle θ _Gs1 corresponding to the pupil partial region 501 in FIG. Gs2 (j) is a light reception signal of a light beam incident on the jth pixel at the principal ray angle θ _Gs2 = 0 degree corresponding to the pupil partial region 502 in FIG. Gs3 (k) is a light reception signal of a light beam incident on the kth pixel at the principal ray angle θ _Gs3 corresponding to the pupil partial region 503 in FIG. As described above, the focus detection signals Gs1 (i), Gs2 (j), and Gs3 (k) include not only the light intensity distribution information but also the incident angle information. In the present embodiment, the focus detection signal Gs1 (i) is translated from the imaging plane 800 to the virtual imaging plane 810 along the angle θ _Gs1 . Similarly, the focus detection signal Gs2 (j), Gs3 (k ) the angles theta _Gs2, translating from the imaging plane 800 along the theta _Gs3 to the virtual image plane 810. Then, by adding (summing) the focus detection signals Gs1 (i), Gs2 (j), and Gs3 (k) after translation, a refocus signal on the virtual imaging plane 810 can be generated.

Shifting the focus detection signal Gs1 (i) along the angle θ _Gs1 from the imaging surface 800 to the virtual imaging surface 810 corresponds to shifting by +2.0 pixels in the column direction. Translating the focus detection signal Gs3 (k) along the angle θ _Gs3 from the imaging surface 800 to the virtual imaging surface 810 corresponds to shifting by −2.0 pixels in the column direction. Since the focus detection signal Gs2 (j) is an angle θ _Gs1 = 0 degrees in the present embodiment, the parallel movement from the imaging surface 800 to the virtual imaging surface 810 corresponds to not shifting. Accordingly, the focus detection signals Gs1 (i) and Gs3 (k) are relatively shifted by two pixels, and the focus detection signals Gs1 (i), Gs2 (j), and Gs3 (k) are added (added) in association with each other. Thus, a refocus signal at the virtual imaging plane 810 can be generated. Then, the second focus detection unit calculates the contrast evaluation value of the generated shift addition signal (refocus signal), and estimates the MTF peak position of the imaging signal based on the calculated contrast evaluation value. The second focus detection of the method is performed.

  With reference to FIG. 10, the refocus second focus detection process will be described. FIG. 10 is a flowchart showing the second focus detection process, and corresponds to step S200 in FIG. Each step of FIG. 10 is mainly executed by the CPU 121 (second focus detection unit 121b) and the image processing circuit 125.

  First, in step S210, the CPU 121 sets a focus detection area including the focus detection pixels of the second focus detection pixel group from the effective pixel areas of the image sensor 107. The CPU 121 generates (acquires) focus detection signals SGs1, SGs2, and SGs3 based on the light reception signals (output signals) of the focus detection pixels included in the set focus detection area.

  Subsequently, in step S220, the CPU 121 and the image processing circuit 125 perform second filter processing on the focus detection signals SGs1, SGs2, and SGs3. In the present embodiment, focus detection is performed from the small defocus state to the vicinity of the best in-focus position by the refocus second focus detection. For this reason, the pass band in the second filter processing is configured to include a high frequency band. If necessary, a Laplacian type (second-order differential type) [1, -2, 1] filter that performs edge extraction of the subject signal is used in the second filtering process to further increase the pass band of the second filtering process. You may move to a high frequency band. By extracting the high-frequency component of the subject and performing the second focus detection, the accuracy of focus detection can be further improved.

  Subsequently, in step S230, the CPU 121 (second focus detection unit) performs a shift process of relatively shifting the focus detection signals SGs1, SGs2, and SGs3 after the second filter process in the pupil division direction. The CPU 121 adds (adds) these focus detection signals to generate a shift addition signal (refocus signal). Further, the CPU 121 calculates a contrast evaluation value (second evaluation value) based on the generated refocus signal.

Here, the kth focus detection signals SGs1 and SGs3 after the second filter processing are Gs1 (k) and Gs3 (k), respectively, and the range of the number k corresponding to the focus detection region is W. Further, the shift amount by the shift process is s ₂ , and the shift range of the shift amount s ₂ is Γ2. At this time, the contrast evaluation value RFCON (second evaluation value) is calculated by the following equation (2).

By the shift process of the shift amount s ₂ , the kth Gs ₂ (k), the (k−s ₂ ) th Gs 1 (k−s ₂ ), and the (k + s ₂ ) th Gs 3 (k + s ₂ ) are added in association with each other. Then, a shift addition signal is generated. Then, the CPU 121 calculates the absolute value of the shift addition signal, takes the maximum value in the range W of the focus detection region, and calculates the contrast evaluation value (second evaluation value) RFCON (s ₂ ). If necessary, the contrast evaluation value (second evaluation value) calculated for each row may be added over a plurality of rows for each shift amount.

  Subsequently, in step S240, the CPU 121 (second focus detection unit) calculates a real value shift amount p2 at which the contrast evaluation value is the maximum value by sub-pixel calculation based on the contrast evaluation value (second evaluation value). To do. The second focus detection means calculates using focus detection pixels Gs1 (i), Gs2 (j) (j = i + 2), and Gs3 (k) (k = j + 2) on the virtual imaging plane 810 in FIG. Do. The shift amount p2 calculated in this way is a real value with which the contrast evaluation value on the virtual imaging plane 810 is the maximum value. Then, the CPU 121 multiplies the shift amount p2 by the second conversion coefficient K2 corresponding to the image height of the focus detection region, the F value of the imaging lens (imaging optical system), and the exit pupil distance, thereby obtaining the second defocus value. A focus amount Def2 is detected (calculated).

  As described above, in the present embodiment, the CPU 121 (second focus detection unit) performs filter processing and shift processing on the focus detection signals SGs1, SGs2, and SGs3 during focus detection by the refocus method. Then, the CPU 121 adds (sums) the focus detection signals after each process to generate a shift addition signal (shift summation signal). The CPU 121 calculates a contrast evaluation value using the generated shift addition signal, and detects (calculates) the second defocus amount Def2 based on the contrast evaluation value.

  Unlike the first focus detection of the phase difference method using the focus detection pixels that are spatially separated, the focus detection signals SGs1, SGs2, SGs3 and the imaging signal RGB used in the second focus detection of the refocus method are adjacent to each other. doing. For this reason, the light beam corresponding to the shift addition signal and the light beam corresponding to the imaging signal substantially coincide with each other, and to the shift addition signal of various aberrations (spherical aberration, astigmatism, coma aberration, etc.) of the imaging optical system. The influence on the imaging signal is also substantially the same. Therefore, the detection focus position (position where the second defocus amount Def2 is 0) calculated by the second focus detection of the refocus method and the best focus position of the imaging signal (MTF peak position of the imaging signal) are Since they are almost the same, highly accurate focus detection is possible.

[Refocusable range]
On the other hand, since the refocusable range is limited, the range in which the CPU 121 (second focus detection unit) can perform the refocus second focus detection with high accuracy is limited.

FIG. 11 is an explanatory diagram of a refocusable range in the present embodiment. When the allowable circle of confusion is δ and the aperture value of the imaging optical system is F, the depth of field at the aperture value F is ± Fδ. In contrast, in the present embodiment, the light receiving portion is 1 / N _H (1/3) in the horizontal direction and N _V (1) in the vertical direction, and the pupil partial region 501 (502) in which the area of the light receiving portion is reduced. , 503) in the horizontal direction, the effective aperture value F ₀₁ (F ₀₂ , F ₀₃ ) becomes darker as F ₀₁ = N _H F. The effective depth of field for each focus detection signal SGs1 (SGs2, SGs3) becomes _NH Fδ and N _H times deeper, and the focusing range widens N _H times. Within the range of effective depth of field ± N _H Fδ, a focused subject image is acquired for each focus detection signal SGs1 (SGs2, SGs3).

Therefore, by refocusing process by which to translate the focus detection signal SGs1 (SGs2, SGs3) along the chief ray angle _{θ Gs1 (θ Gs2, θ Gs3} ) shown in FIG. 9, after shooting, re-adjust the focus position (Refocus). Therefore, the adjustment defocus amount d ′ from the imaging surface where the focus position can be readjusted (refocusable) after shooting is limited, and the refocusable range of the adjustment defocus amount d ′ is approximately the following equation: It becomes the range of (3).

  As described above, the range of the defocus amount that can be focus-detected with high accuracy by the refocus method is generally limited to the range of the expression (3). For this reason, the defocus range in which focus detection can be performed with high accuracy by the second focus detection is a range below the defocus range in which focus detection can be performed with high accuracy by the first focus detection using the phase difference method. Therefore, the present embodiment is configured such that the shift range of the shift process of the refocus second focus detection is equal to or smaller than the shift range of the phase difference first focus detection shift process.

  In the focus detection of this embodiment, the first focus detection is performed to adjust the focus from the large defocus state to the small defocus state of the imaging optical system, and the vicinity of the best focus position from the small defocus state of the imaging optical system. The second focus detection is performed in order to adjust the focus up to. Therefore, it is preferable that the pass band of the second filter process in the second focus detection includes a higher frequency band than the pass band of the first filter process in the first focus detection.

  In the image sensor 107 of the present embodiment, the light beam received by the focus detection pixel and the light beam received by the imaging pixel are different from each other, and the focal points of various aberrations (spherical aberration, astigmatism, coma aberration, etc.) of the imaging optical system. The influence on the detection pixel and the influence on the imaging signal are different. When the aperture value of the imaging optical system is small (bright), the influence (difference) becomes larger. Therefore, when the aperture value of the imaging optical system is small (bright), the detection focus position (position where the first defocus amount Def1 is 0) calculated by the first focus detection of the phase difference method and the imaging signal There may be a difference between the best focus position (the MTF peak position of the imaging signal). In particular, when the aperture value of the imaging optical system is equal to or smaller than a predetermined aperture value, the focus detection accuracy of the first focus detection of the phase difference method may be lowered. Therefore, if necessary, when the aperture value of the imaging optical system is equal to or smaller than the predetermined aperture value, the second defocus amount Def2 is obtained by the refocus second focus detection in addition to the phase difference first focus detection. It is preferable to detect (calculate) and perform focus detection with high accuracy.

[Focus detection processing flow]
Next, focus control in the present embodiment will be described with reference to FIG. FIG. 12 is a flowchart showing focus control. Each step of FIG. 12 is mainly executed by the CPU 121 (first focus detection means 121a, second focus detection means 121b, focus control means 121c). The CPU 121 performs the first focus detection until the absolute value of the defocus amount of the imaging optical system is equal to or less than the first predetermined value, and drives the third lens group 105 (focus lens group) (performs lens driving). Focus adjustment is performed from the large defocus state to the small defocus state of the imaging optical system. Thereafter, the second focus is detected and the lens is driven until the absolute value of the defocus amount of the imaging optical system becomes equal to or less than a second predetermined value (first predetermined value> second predetermined value). The focus is adjusted from the small defocus state to the vicinity of the best focus position.

  First, in step S100, the CPU 121 (first focus detection unit 121a) detects (calculates) the first defocus amount Def1 by phase difference first focus detection. Subsequently, in step S301, the CPU 121 determines whether or not the magnitude | Def1 | of the first defocus amount Def1 calculated in step S100 is equal to or less than a first predetermined value. If the magnitude | Def1 | of the first defocus amount Def1 is larger than the first predetermined value, the CPU 121 (focus control means 121c) drives the lens according to the first defocus amount Def1, and repeats step S100. On the other hand, when the magnitude | Def1 | of the first defocus amount Def1 is equal to or smaller than the first predetermined value, the process proceeds to step S200.

  Subsequently, in step S200, the CPU 121 (second focus detection unit 121b) detects (calculates) the second defocus amount Def2 by refocus second focus detection. When the magnitude | Def2 | of the second defocus amount Def2 is larger than a second predetermined value (first predetermined value> second predetermined value), the CPU 121 (focus control unit 121c) responds to the second defocus amount Def2. The lens is driven and step S200 is repeated. On the other hand, when the magnitude | Def2 | of the second defocus amount Def2 is equal to or smaller than the second predetermined value, the focus adjustment operation (focus control in this flow) is terminated. As described above, the focus control unit 121c drives the focus lens based on the first defocus amount, and when the first defocus amount (absolute value thereof) becomes smaller than the predetermined amount (first predetermined value), The focus lens is driven based on the 2 defocus amount. According to the present embodiment, it is possible to reduce the difference between the detection focus position based on the focus detection signal and the best focus position based on the imaging signal, and to perform focus detection with high accuracy.

  As described above, the control device (CPU 121) of the present embodiment includes the first focus detection unit 121a and the second focus detection unit 121b. The first focus detection unit 121a includes a first photoelectric conversion unit group (for example, the photoelectric conversion unit 301) among the plurality of photoelectric conversion units 301, 302, and 303 that receive light beams that pass through different pupil partial regions of the imaging optical system. , 303), focus detection is performed based on the first evaluation value of the signal acquired. The second focus detection unit 121b uses a signal acquired from a second photoelectric conversion unit group (for example, photoelectric conversion units 301, 302, and 303) different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. Focus detection is performed based on the calculated second evaluation value.

  Preferably, the first evaluation value is a correlation amount of a signal acquired from the first photoelectric conversion unit group, and the second evaluation value is a contrast calculated using a signal acquired from the second photoelectric conversion unit group. It is an evaluation value. More preferably, the first focus detection unit calculates a first defocus amount Def1 based on the correlation amount. The second focus detection unit generates a shift addition signal by performing a shift process and an addition process on the signal acquired from the second photoelectric conversion unit group, and calculates a contrast evaluation calculated using the shift addition signal. The second defocus amount Def2 is calculated based on the value.

  Preferably, the first photoelectric conversion unit group includes at least two photoelectric conversion units (for example, photoelectric conversion units 301 and 303) among the plurality of photoelectric conversion units. The second photoelectric conversion unit group includes at least three photoelectric conversion units (for example, photoelectric conversion units 301, 302, and 303) among the plurality of photoelectric conversion units. Preferably, the plurality of photoelectric conversion units respectively receive first light fluxes that pass through the first pupil partial region, the second pupil partial region, and the third pupil partial region (pupil partial regions 501 to 503). Unit, a second photoelectric conversion unit, and a third photoelectric conversion unit (photoelectric conversion units 301 to 303). The first photoelectric conversion unit group includes a first photoelectric conversion unit (photoelectric conversion unit 301) and a third photoelectric conversion unit (photoelectric conversion unit 303). The second photoelectric conversion unit group includes a first photoelectric conversion unit (photoelectric conversion unit 301), a second photoelectric conversion unit (photoelectric conversion unit 302), and a third photoelectric conversion unit (photoelectric conversion unit 303).

(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 are capable of highly accurate focus detection.

  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.

  In the present embodiment, the image sensor is an imaging pixel (RGB) that photoelectrically converts an optical image formed through an imaging optical system and outputs an image signal, and a focus that outputs a signal used for focus detection. And detection pixels (Gs1, Gs2, Gs3). However, the present embodiment is not limited to this. For example, the imaging element has a plurality of photoelectric conversion units (for example, photoelectric conversion units 301, 302, and 303) for one microlens, and the microlenses are arranged in a two-dimensional shape. This embodiment is applicable.

121 CPU (control device)
121a First focus detection means 121b Second focus detection means

Claims (15)

The first focus detection is performed based on the first evaluation value of the signal acquired from the first photoelectric conversion unit group among the plurality of photoelectric conversion units that receive the light beams passing through different pupil partial regions of the imaging optical system. A focus detection means;
A second focus that performs focus detection based on a second evaluation value calculated using a signal acquired from a second photoelectric conversion unit group different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. And a control means. The first evaluation value is a correlation amount of the signal acquired from the first photoelectric conversion unit group,
The control device according to claim 1, wherein the second evaluation value is a contrast evaluation value calculated using the signal acquired from the second photoelectric conversion unit group. The first focus detection means calculates a first defocus amount based on the correlation amount,
The second focus detection unit generates a shift addition signal by performing a shift process and an addition process on the signal acquired from the second photoelectric conversion unit group, and is calculated using the shift addition signal. The control device according to claim 2, wherein a second defocus amount is calculated based on the contrast evaluation value. A focus control means for driving a focus lens included in the imaging optical system;
The focus control means includes
Driving the focus lens based on the first defocus amount;
4. The control device according to claim 3, wherein when the first defocus amount is smaller than a predetermined amount, the focus lens is driven based on the second defocus amount. The first focus detection means performs phase difference type focus detection,
5. The control device according to claim 1, wherein the second focus detection unit performs refocus-type focus detection. 6. An imaging device having a plurality of photoelectric conversion units that receive light beams passing through different pupil partial regions of the imaging optical system;
Of the plurality of photoelectric conversion units, a first focus detection unit that performs focus detection based on a first evaluation value of a signal acquired from the first photoelectric conversion unit group;
A second focus that performs focus detection based on a second evaluation value calculated using a signal acquired from a second photoelectric conversion unit group different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. And an imaging device. The first photoelectric conversion unit group includes at least two photoelectric conversion units among the plurality of photoelectric conversion units,
The imaging device according to claim 6, wherein the second photoelectric conversion unit group includes at least three photoelectric conversion units among the plurality of photoelectric conversion units. The plurality of photoelectric conversion units are
A first photoelectric converter that receives a light beam passing through the first pupil partial region;
A second photoelectric conversion unit that receives a light beam passing through the second pupil partial region;
A third photoelectric conversion unit that receives a light beam passing through the third pupil partial region,
The first photoelectric conversion unit group includes the first photoelectric conversion unit and the third photoelectric conversion unit,
The imaging device according to claim 6, wherein the second photoelectric conversion unit group includes the first photoelectric conversion unit, the second photoelectric conversion unit, and the third photoelectric conversion unit. The image sensor has a microlens corresponding to each of the plurality of photoelectric conversion units,
The first photoelectric conversion unit is biased in the first direction with respect to the center of the microlens,
The imaging apparatus according to claim 8, wherein the third photoelectric conversion unit is biased in a second direction opposite to the first direction with respect to a center of the microlens. The first photoelectric conversion unit group receives a part of the total light flux that passes through the pupil region of the imaging optical system,
10. The imaging apparatus according to claim 6, wherein the second photoelectric conversion unit group receives all light beams that pass through a pupil region of the imaging optical system. The image sensor is
An imaging pixel that photoelectrically converts an optical image formed through the imaging optical system and outputs an image signal;
The imaging apparatus according to claim 6, further comprising: a focus detection pixel that outputs the signal used for the focus detection.   The said image pick-up element has the said some photoelectric conversion part with respect to one microlens, and this microlens is arranged in two dimensions, The one of Claims 6 thru | or 10 characterized by the above-mentioned. The imaging device described. First focus detection is performed based on a first evaluation value of a signal acquired from the first photoelectric conversion unit group among a plurality of photoelectric conversion units that receive light beams passing through different pupil partial regions of the imaging optical system. Steps,
Step of performing second focus detection based on a second evaluation value calculated using a signal acquired from a second photoelectric conversion unit group different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. And a control method comprising: First focus detection is performed based on a first evaluation value of a signal acquired from the first photoelectric conversion unit group among a plurality of photoelectric conversion units that receive light beams passing through different pupil partial regions of the imaging optical system. Steps,
Step of performing second focus detection based on a second evaluation value calculated using a signal acquired from a second photoelectric conversion unit group different from the first photoelectric conversion unit group among the plurality of photoelectric conversion units. And causing a computer to execute the program.   A storage medium storing the program according to claim 14.