Imaging device

Abstract

In order to accurately continue focusing on a subject, this imaging device comprises: an imaging unit having a first pixel that photoelectrically converts light transmitted through an optical system and outputs a signal to be used for focus detection of the optical system, and a second pixel that photoelectrically converts light transmitted through the optical system and outputs a signal to be used for image generation; a detection unit that detects a deviation amount between an image plane of the optical system and an imaging surface of the imaging unit on the basis of the signal output from the first pixel; and a control unit that, when the subject is not performing a predetermined movement, controls the position of the optical system on the basis of the deviation amount if the deviation amount is within a first range, and when the subject is performing the predetermined movement, controls the position of the optical system on the basis of the deviation amount if the deviation amount is in a second range narrower than the first range.

Description

Imaging device

[0001] This relates to an imaging device.

[0002] An imaging apparatus is known that continues to focus on a subject even when the focus detection area moves away from the subject (see Japanese Patent Laid-Open No. 2003-122294). There has been a demand for improved focus detection accuracy.

[0003] JP 2012-237809 A

[0004] According to one aspect of the disclosure, the imaging device includes an imaging unit having a first pixel that photoelectrically converts light that has passed through an optical system and outputs a signal used for focus detection of the optical system, and a second pixel that photoelectrically converts light that has passed through the optical system and outputs a signal used for generating an image; a detection unit that detects the amount of deviation between an image plane of the optical system and an imaging plane of the imaging unit based on the signal output from the first pixel; and a control unit that, when a subject is not making a predetermined movement, controls the position of the optical system based on the amount of deviation if the amount of deviation is within a first range, and, when the subject is making the predetermined movement, controls the position of the optical system based on the amount of deviation if the amount of deviation is within a second range narrower than the first range.

[0005] The configurations of the embodiments described below may be modified as appropriate, and at least a portion of the configuration may be replaced with other components. Furthermore, components that are not particularly limited in terms of their placement may be placed in any position that can achieve their function, not limited to the placement disclosed in the embodiments.

[0006] FIG. 1 is a diagram illustrating an example of the configuration of an imaging device according to an embodiment. FIG. 2(a) is a diagram illustrating a focus detection area on the imaging surface of an image sensor, and FIG. 2(b) is a diagram illustrating a small area within the focus detection area. FIG. 3 is a diagram illustrating an example of the arrangement of pixels within the focus detection area. FIG. 4 is a diagram illustrating the relationship between a first pixel group, a second pixel group, a third pixel group, and the focus detection area. FIGS. 5(a) to 5(c) are diagrams illustrating an example of the configuration of focus detection pixels and imaging pixels provided in a pixel unit. FIGS. 6(a) and 6(b) are diagrams illustrating focus detection based on first and second signals output from an AF pixel pair selected by a selection unit. FIGS. 7(a) and 7(b) are diagrams illustrating a case where second AF lock-on is performed. FIG. 8 is a flowchart illustrating an example of the operation of a camera according to an embodiment. FIGS. 9(a) to 9(c) are diagrams illustrating specific examples of an area where a subject is detected (broken line frame), an area where focus detection is performed (solid line frame), and the defocus amount (numerical value) for each focus detection area. 10(a) and 10(b) are diagrams for explaining Modification 1. FIGS. 11(a) and 11(b) are diagrams for explaining Modification 2. FIGS. 12(a) to 12(d) are diagrams for explaining Modification 3. FIGS. 13(a) to 13(c) are diagrams for explaining Modification 4. FIG. 14 is a diagram for explaining Modification 6.

[0007] An electronic camera 1 (hereinafter referred to as camera 1) as an example of an imaging device according to an embodiment will be described below with reference to FIGS.

[0008] 1 is a diagram showing an example of the configuration of a camera 1 according to an embodiment. The camera 1 includes a camera body 2 and an interchangeable lens 3. Because the camera 1 includes the camera body 2 and the interchangeable lens 3, it is sometimes referred to as a camera system.

[0009] (Interchangeable Lens 3) The interchangeable lens 3 includes a lens-side mount unit 301, a photographing optical system (imaging optical system) 31, a lens control unit 32, and a lens memory 33. The lens-side mount unit 301 includes a lens-side connection unit 302. The lens-side connection unit 302 has multiple terminals, such as a terminal for a clock signal, a terminal for a data signal, and a terminal for power supply. The interchangeable lens 3 is detachably attached to the camera body 2 by the lens-side mount unit 301 and a body-side mount unit 201, which will be described later.

[0010] The photographic optical system 31 includes a plurality of lenses, including a zoom lens (variable magnification lens) 31a that changes the focal length and a focus lens (focus adjustment lens) 31b, and an aperture 31c, and forms a subject image on the imaging surface 22a of the image sensor 22. Note that although the zoom lens 31a and the focus lens 31b are shown in Fig. 1 as a schematic illustration, a typical photographic optical system is generally made up of a large number of optical elements.

[0011] As will be described later, the photographing optical system 31 of the interchangeable lens 3 has an optical characteristic in which the position of its exit pupil, i.e., the exit pupil distance, changes depending on the image height. In other words, the exit pupil distance of the photographing optical system 31 changes depending on the position on the imaging plane 22a, i.e., the distance from the optical axis OA1 of the photographing optical system 31 to the imaging plane 22a. The optical axis OA1 of the photographing optical system 31 intersects with the imaging plane 22a at the center of the imaging plane 22a. It can also be said that the exit pupil distance of the photographing optical system 31 changes depending on the distance from the center of the imaging plane 22a. Here, the exit pupil distance is the distance between the exit pupil of the photographing optical system 31 and the image plane of the image formed by the photographing optical system 31. The imaging plane 22a of the image sensor 22 is, for example, a surface on which a photoelectric conversion unit (described later) or a surface on which microlenses are arranged.

[0012] The photographic optical system 31 differs depending on the type of interchangeable lens 3 attached to the body side mount unit 201. Therefore, the exit pupil distance of the photographic optical system 31 differs depending on the type of interchangeable lens 3. Furthermore, the optical characteristics of the exit pupil distance, which changes depending on the image height, also differ depending on the type of interchangeable lens 3.

[0013] The lens control unit 32 is configured with a processor such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), or ASIC (Application Specific Integrated Circuit), and memories such as ROM (Read Only Memory) and RAM (Random Access Memory), and controls each component of the interchangeable lens 3 based on a control program. The lens control unit 32 controls the position of the zoom lens 31a, the position of the focus lens 31b, and the drive of the diaphragm 31c based on signals output from the body control unit 21 of the camera body 2. When signals indicating the direction and amount of movement of the focus lens 31b are input from the body control unit 21, the lens control unit 32 moves the focus lens 31b back and forth along the optical axis OA1 based on the signals to adjust the focal position of the photographic optical system 31. The lens control unit 32 also controls the position of the zoom lens 31a and the aperture diameter of the diaphragm 31c based on signals output from the body control unit 21.

[0014] The lens memory 33 is composed of, for example, a non-volatile storage medium. Information related to the interchangeable lens 3 is stored (recorded) in the lens memory 33 as lens information. The lens information includes data on the optical characteristics (exit pupil distance and F-number) of the photographic optical system 31, data on the infinity position and close position of the focus lens 31b, and data on the shortest focal length and longest focal length of the interchangeable lens 3. The optical characteristics of the photographic optical system 31 include the exit pupil distance and F-number (aperture value of the diaphragm 31c). The lens information differs depending on the type of interchangeable lens 3. The lens information may also be stored in an internal memory of the lens control unit 32. The lens information may also be stored in a body memory 23 included in the camera body 2, which will be described later. In this case, the body memory 23 stores lens information for multiple interchangeable lenses 3.

[0015] In this embodiment, the lens information includes information about the exit pupil distance of the imaging optical system 31. The information about the exit pupil distance includes information indicating the exit pupil distance (Co) at the position where the imaging plane 22a and the optical axis OA1 intersect (the position where the image height is zero), and information about a coefficient included in an arithmetic expression that expresses the relationship between the exit pupil distance and the image height.

[0016] Writing data to the lens memory 33 and reading data from the lens memory 33 are controlled by the lens control unit 32. When the interchangeable lens 3 is attached to the camera body 2, the lens control unit 32 transmits lens information to the body control unit 21 via the terminals of the lens side connection unit 302 and the body side connection unit 202. The lens control unit 32 also transmits to the body control unit 21 position information (focal length information) of the controlled zoom lens 31a, position information of the controlled focus lens 31b, information on the F-number of the controlled aperture 31c, and the like.

[0017] The lens control unit 32 communicates by sending and receiving information bidirectionally between the camera body 2 and the interchangeable lens 3 via the terminals of the lens-side connection unit 302 and the body-side connection unit 202. When a signal requesting the transmission of information regarding the exit pupil distance is input from the camera body 2, the lens control unit 32 transmits information regarding the exit pupil distance to the camera body 2. Note that the information regarding the exit pupil distance differs depending on the type of interchangeable lens 3. The lens control unit 32 may also transmit information regarding the exit pupil distance to the camera body 2 each time the image sensor 22 captures an image. The lens control unit 32 may also transmit information regarding the exit pupil distance to the camera body 2 when the zoom lens 31a moves and the focal length of the photographic optical system 31 changes. The lens control unit 32 may transmit information regarding the focal length of the photographic optical system 31 and information regarding the exit pupil distance to the camera body 2 in a single bidirectional communication.

[0018] (Camera Body 2) The camera body 2 includes a body-side mount unit 201, an image sensor 22, a body memory 23, a display unit 24, an operation unit 25, and a body control unit 21. In this embodiment, the image sensor 22 and the body control unit 21 constitute a focus detection device 4.

[0019] The body side mount section 201 includes a body side connection section 202. The body side connection section 202 has a plurality of terminals, such as a terminal for a clock signal, a terminal for a data signal, and a terminal for power supply.

[0020] When the interchangeable lens 3 is attached to the camera body 2, a terminal provided on the body-side connector 202 is electrically connected to a terminal provided on the lens-side connector 302. This enables power to be supplied from the camera body 2 to the interchangeable lens 3 and communication between the camera body 2 and the interchangeable lens 3.

[0021] The imaging element 22 is a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor. The imaging element 22 captures an image of a subject formed by the imaging optical system 31. The imaging element 22 includes a pixel unit 221 in which a plurality of pixels each having a photoelectric conversion unit are arranged two-dimensionally (in the row and column directions), and a control unit 222 that controls the pixel unit 221. The photoelectric conversion unit is configured by a photodiode (PD).

[0022] As will be described later, the pixel unit 221 includes imaging pixels (second pixels) that photoelectrically convert light transmitted through the imaging optical system 31 and output signals used for image generation, and focus detection pixels (first pixels) that photoelectrically convert received light and output signals used for focus detection. The imaging pixels include pixels (hereinafter referred to as R pixels) that have filters with spectral characteristics that separate incident light in a first wavelength range (red (R) light), pixels (hereinafter referred to as G pixels) that have filters with spectral characteristics that separate incident light in a second wavelength range (green (G) light), and pixels (hereinafter referred to as B pixels) that have filters with spectral characteristics that separate incident light in a third wavelength range (blue (B) light). The R, G, and B pixels are arranged in a Bayer array. The focus detection pixels are arranged to replace some of the imaging pixels and are distributed across substantially the entire imaging surface 22a of the image sensor 22.

[0023] The control unit 222 causes the focus detection pixel signals to be output based on an instruction signal from the body control unit 21. The control unit 222 also causes the imaging pixel signals to be output based on an instruction signal from the body control unit 21.

[0024] The body memory 23 is configured, for example, by a non-volatile storage medium, etc. Image data, control programs, etc. are recorded in the body memory 23. Writing data to the body memory 23 and reading data from the body memory 23 are controlled by the body control unit 21.

[0025] The display unit 24 displays an image based on image data, an image showing a focus detection area (AF area) such as an AF frame, information related to photography such as shutter speed and F-number, a menu screen, and the like.

[0026] The operation unit 25 includes various setting switches such as a release button, a power switch, and switches for switching between various modes, and outputs operation signals corresponding to the respective operations to the body control unit 21. The operation unit 25 is also a setting unit that can set an arbitrary focus detection area from a plurality of focus detection areas, and the user can select an arbitrary focus detection area by operating the operation unit 25.

[0027] The body control unit 21 is configured with a processor such as a CPU, FPGA, or ASIC, and memories such as ROM and RAM, and controls each unit of the camera 1 based on a control program. The body control unit 21 has an image data generation unit 211, a subject detection unit 212, an area setting unit 213, a distance calculation unit 214, a selection unit 215, a focus detection unit 216, and a position control unit 217. The image data generation unit 211, the subject detection unit 212, the area setting unit 213, the distance calculation unit 214, the selection unit 215, the focus detection unit 216, and the position control unit 217 are realized, for example, by the processor executing a program.

[0028] The image data generation unit 211 generates image data by performing various image processing on signals output from the imaging pixels of the image sensor 22. Note that the image data generation unit 211 may also generate image data using signals output from the focus detection pixels.

[0029] The subject detection unit 212 detects a predetermined subject from an image based on the image data generated by the image data generation unit 211. For example, when a "bird mode" suitable for photographing wild birds, etc. is set as the shooting mode, the subject detection unit 212 detects a bird as the subject. Furthermore, when the subject is a bird, the subject detection unit 212 detects whether the subject (bird) is flying, and if so, whether it is moving away from or approaching the camera 1. Furthermore, when an "airplane mode" suitable for photographing airplanes is set as the shooting mode, the subject detection unit 212 detects an airplane as the subject. Furthermore, when a "portrait mode" suitable for photographing people is set as the shooting mode, the subject detection unit 212 detects a person as the subject.

[0030] The area setting unit 213 sets (selects) at least one focus detection area 100 from among the multiple focus detection areas 100 provided on the imaging surface 22a of the image sensor 22 shown in FIG. 2A. The multiple AF frames displayed on the display unit 24 correspond to the multiple focus detection areas 100 provided on the image sensor 22. For example, the area setting unit 213 sets, as an area for focus detection, the focus detection area 100 corresponding to the AF frame selected by the user by operating the operation unit 25 from among the multiple AF frames displayed on the display unit 24, or the focus detection area 100 corresponding to the AF frame including the subject detected by the subject detection unit 212.

[0031] In each focus detection area 100, in addition to imaging pixels, a plurality of types of pairs of focus detection pixels (AF pixel pairs) are arranged.

[0032] 3 is a diagram showing an example of pixel arrangement within the focus detection area 100. In Fig. 3, a first pixel group 401 in which R pixels 13 and G pixels 13 are arranged alternately in the ±X directions, i.e., in the row direction, and a second pixel group 402 in which G pixels 13 and B pixels 13 are arranged alternately in the ±Y directions, i.e., in the column direction, are arranged alternately. The imaging pixels 13 are arranged according to a Bayer array.

[0033] Some of the multiple second pixel groups 402 include the first or second focus detection pixel 11, 12. The first and second focus detection pixels 11, 12 each have a light-shielding portion 43. In FIG. 3 , the second pixel groups 402 including the first focus detection pixel 11 are indicated as second pixel groups 402a, 402c, and 402e, and the second pixel groups 402 including the second focus detection pixel 12 are indicated as second pixel groups 402b, 402d, and 402f. The second pixel groups 402a, 402c, and 402e including the first focus detection pixel 11 and the second pixel groups 402b, 402d, and 402f including the second focus detection pixel 12 will be described below.

[0034] In the second pixel group 402a, the B pixels 13 are replaced with the first focus detection pixels 11a. In the second pixel group 402a, the first focus detection pixels 11a and the G pixels 13 are arranged alternately. The photoelectric conversion units of the first focus detection pixels 11a receive light beams that have passed through one of the first and second pupil regions of the exit pupil of the photographing optical system 31. The light-shielding units 43 of the first focus detection pixels 11a block light beams that have passed through the other of the first and second pupil regions of the exit pupil of the photographing optical system 31. In the following description, it is assumed that the photoelectric conversion units of the first focus detection pixels 11a receive light beams that have passed through the first pupil region of the exit pupil of the photographing optical system 31. It is assumed that the light-shielding units 43 of the first focus detection pixels 11a block light beams that have passed through the second pupil region of the exit pupil of the photographing optical system 31.

[0035] In the second pixel group 402b, which is a predetermined number of rows away from the second pixel group 402a, the B pixels 13 are replaced with second focus detection pixels 12a. In the second pixel group 402b, the second focus detection pixels 12a and G pixels 13 are arranged alternately. The photoelectric conversion units of the second focus detection pixels 12a receive light beams that have passed through a pupil region of an exit pupil different from that of the first focus detection pixel 11a. The light-shielding units 43 of the second focus detection pixels 12a block light beams that have passed through a pupil region of an exit pupil different from that of the first focus detection pixel 11a. In the following description, the photoelectric conversion units of the second focus detection pixels 12a receive light beams that have passed through a second pupil region of the exit pupil of the photographing optical system 31. The light-shielding units 43 of the second focus detection pixels 12a block light beams that have passed through a first pupil region of the exit pupil of the photographing optical system 31.

[0036] The arrangement position of the first focus detection pixel 11a in the second pixel group 402a and the arrangement position of the second focus detection pixel 12a in the second pixel group 402b are the same, i.e., the first focus detection pixel 11a and the second focus detection pixel 12a are arranged in the same column.

[0037] The first focus detection pixel 11a of the second pixel group 402a and the second focus detection pixel 12a of the second pixel group 402b constitute a first AF pixel pair PR1. Note that the second pixel groups 402a and 402b may be arranged in multiple rows, resulting in multiple first AF pixel pairs PR1. A pixel set including the first AF pixel pair PR1 and the imaging pixel 13 is referred to as a first pixel set 400-1.

[0038] In the second pixel group 402c, which is a predetermined number of rows away from the second pixel group 402b, the B pixels 13 are replaced with the first focus detection pixels 11b. In the second pixel group 402c, the first focus detection pixels 11b and G pixels 13 are arranged alternately. Like the first focus detection pixel 11a, the photoelectric conversion unit of the first focus detection pixel 11b receives the light beam that has passed through a first pupil region of the exit pupil of the photographing optical system 31. Like the light-shielding unit 43 of the first focus detection pixel 11a, the light-shielding unit 43 of the first focus detection pixel 11b blocks the light beam that has passed through a second pupil region of the exit pupil of the photographing optical system 31.

[0039] In a second pixel group 402d, which is a predetermined number of rows away from the second pixel group 402c, the B pixels 13 are replaced with second focus detection pixels 12b. In the second pixel group 402d, the second focus detection pixels 12b and G pixels 13 are arranged alternately. Like the second focus detection pixel 12a, the photoelectric conversion units of the second focus detection pixels 12b receive light beams that have passed through a second pupil region of the exit pupil of the photographing optical system 31. Like the light-shielding unit 43 of the second focus detection pixel 12a, the light-shielding unit 43 of the second focus detection pixel 12b blocks light beams that have passed through a first pupil region of the exit pupil of the photographing optical system 31.

[0040] The arrangement position of the first focus detection pixel 11b in the second pixel group 402c and the arrangement position of the second focus detection pixel 12b in the second pixel group 402d are the same, i.e., the first focus detection pixel 11b and the second focus detection pixel 12b are arranged in the same column.

[0041] The first focus detection pixel 11b of the second pixel group 402c and the second focus detection pixel 12b of the second pixel group 402d constitute a second AF pixel pair PR2. Note that the second pixel groups 402c and 402d may be arranged in multiple rows, resulting in multiple second AF pixel pairs PR2. A pixel set including the second AF pixel pair PR2 and the imaging pixel 13 is referred to as a second pixel set 400-2.

[0042] In a second pixel group 402e, which is a predetermined number of rows away from the second pixel group 402d, the B pixels 13 are replaced with first focus detection pixels 11c. In the second pixel group 402e, the first focus detection pixels 11c and G pixels 13 are arranged alternately. The photoelectric conversion unit of the first focus detection pixel 11c, like the first focus detection pixels 11a and 11b, receives light beams that have passed through a first pupil region of the exit pupil of the photographing optical system 31. The light-shielding unit 43 of the first focus detection pixel 11c, like the light-shielding units 43 of the first focus detection pixels 11a and 11b, blocks light beams that have passed through a second pupil region of the exit pupil of the photographing optical system 31.

[0043] In a second pixel group 402f, which is a predetermined number of rows away from the second pixel group 402e, the B pixels 13 are replaced with second focus detection pixels 12c. In the second pixel group 402f, the second focus detection pixels 12c and the G pixels 13 are arranged alternately. The photoelectric conversion units of the second focus detection pixels 12c receive light beams that have passed through a second pupil region of the exit pupil of the photographing optical system 31. The light-shielding units 43 of the second focus detection pixels 12c, like the light-shielding units 43 of the second focus detection pixels 12a and 12b, block light beams that have passed through a first pupil region of the exit pupil of the photographing optical system 31.

[0044] The position of the first focus detection pixel 11c in the second pixel group 402e and the position of the second focus detection pixel 12c in the second pixel group 402f are the same, i.e., the first focus detection pixel 11c and the second focus detection pixel 12c are arranged in the same column.

[0045] The first focus detection pixel 11c of the second pixel group 402e and the second focus detection pixel 12c of the second pixel group 402f constitute a third AF pixel pair PR3. Note that the second pixel groups 402e and 402f may be arranged in multiple rows, resulting in multiple third AF pixel pairs PR3. A pixel set including the third AF pixel pair PR3 and the imaging pixel 13 is referred to as a third pixel set 400-3.

[0046] 4 is a diagram showing the relationship between a first pixel set 400-1, a second pixel set 400-2, a third pixel set 400-3, and a focus detection area 100. As shown in FIG. 4, each focus detection area 100 includes a first pixel set 400-1, a second pixel set 400-2, and a third pixel set 400-3. The first pixel sets 400-1 of the focus detection areas 100 that are adjacent in the X direction (row direction) are adjacent to each other in the X direction. The second pixel sets 400-2 of the focus detection areas 100 that are adjacent to each other in the X direction are adjacent to each other in the X direction. The third pixel sets 400-3 of the focus detection areas 100 that are adjacent to each other in the X direction are adjacent to each other in the X direction. 4, the first pixel set 400-1, the second pixel set 400-2, and the third pixel set 400-3 are arranged consecutively in the X direction (row direction), while the first pixel set 400-1, the second pixel set 400-2, and the third pixel set 400-3 are arranged repeatedly in this order in the Y direction (column direction).

[0047] The areas of the light-shielding portions 43 of the first AF pixel pair PR1, the second AF pixel pair PR2, and the third AF pixel pair PR3 are different, except for pixel pairs located around the optical axis OA1 of the photographing optical system 31 (the center of the image pickup surface 22a). When the exit pupil distance is different, the angle of incidence of light incident on the focus detection pixels is different, except for focus detection pixels located around the optical axis OA1 of the photographing optical system 31. The shorter the exit pupil distance, the larger the angle of incidence, and the longer the exit pupil distance, the smaller the angle of incidence. The areas of the light-shielding portions 43 differ for each AF pixel pair in order to block a portion of the light incident at different angles depending on the exit pupil distance. This allows the focus detection unit 216 to accurately detect the defocus amount even at different exit pupil distances. However, the angle of incidence of pixel pairs located around the optical axis OA1 of the photographing optical system 31 (the center of the image pickup surface 22a) is 0° regardless of the exit pupil distance. Therefore, the areas of the light-shielding portions 43 of the first AF pixel pair PR1, the second AF pixel pair PR2, and the third AF pixel pair PR3 located around the optical axis OA1 (center of the imaging surface 22a) of the photographing optical system 31 are the same. The areas of the light-shielding portions 43 also differ depending on the position (image height) of the focus detection pixel.

[0048] In this embodiment, the first focus detection pixels 11a to 11c and the second focus detection pixels 12a to 12c each have a filter with spectral characteristics that separates light in a second wavelength range (green (G) light) from the incident light. Note that the filters of the first focus detection pixels 11a to 11c and the second focus detection pixels 12a to 12c may also be filters with spectral characteristics that separate light in a first wavelength range (red (R) light) or light in a third wavelength range (blue (B) light). Furthermore, the first focus detection pixels 11a to 11c and the second focus detection pixels 12a to 12c may also have filters with spectral characteristics that separate light in the first, second, and third wavelength ranges from the incident light.

[0049] 5(a) to 5(c) are diagrams illustrating exemplary configurations of focus detection pixels and imaging pixels provided in the pixel section 221. Fig. 5(a) shows an exemplary cross section of the first focus detection pixel 11 of the first and second focus detection pixels 11, 12 that make up an AF pixel pair, and Fig. 5(b) shows an exemplary cross section of the second focus detection pixel 12 of the first and second focus detection pixels 11, 12. Fig. 5(c) shows an exemplary cross section of an imaging pixel 13 (R pixel, G pixel, B pixel).

[0050] 5A to 5C, the first and second focus detection pixels 11, 12 and the imaging pixel 13 each have a microlens 44, a color filter 51, and a photoelectric conversion unit 42 (PD 42). The photoelectric conversion unit 42 photoelectrically converts light that has transmitted (passed) through the microlens 44 and the color filter 51. A first light beam 61 is a light beam that has passed through a first pupil region that divides the exit pupil of the photographing optical system 31 into approximately two equal parts. A second light beam 62 is a light beam that has passed through a second pupil region that divides the exit pupil of the photographing optical system 31 into approximately two equal parts.

[0051] In FIG. 5A , the first focus detection pixel 11 is provided with a light-shielding portion 43 that blocks the second light beam 62 of the first and second light beams 61, 62. The light-shielding portion 43 is located between the color filter 51 and the photoelectric conversion portion 42 and is provided on the photoelectric conversion portion 42. In the example shown in FIG. 5A , the light-shielding portion 43 is disposed so as to block the left half (the −X direction side) of the photoelectric conversion portion 42. The right end (the end in the +X direction) of the light-shielding portion 43 approximately coincides with the center line that divides the photoelectric conversion portion 42 into left and right halves. The photoelectric conversion portion 42 of the first focus detection pixel 11 receives the first light beam 61. The photoelectric conversion portion 42 of the first focus detection pixel 11 photoelectrically converts the first light beam 61 to generate an electric charge, and the first focus detection pixel 11 outputs a first signal Sig1 based on the electric charge generated by the photoelectric conversion portion 42.

[0052] The area of ​​the light-shielding portion 43 varies depending on the position (image height) of the first focus detection pixel 11, except for the first focus detection pixels 11 located around the optical axis OA1 (center of the image pickup surface 22a) of the photographing optical system 31. When the position of the first focus detection pixel 11 varies, i.e., when the image height varies, the angle of incidence of light incident on the first focus detection pixel 11 varies. The angle of incidence increases as the image height increases, and decreases as the image height decreases, and when the image height is zero, the angle of incidence is 0°. The area of ​​the light-shielding portion 43 varies depending on the image height in order to block the second light beam 62, which is part of the light incident at angles of incidence that vary depending on the image height.

[0053] In FIG. 5B , the second focus detection pixel 12 is provided with a light-shielding portion 43 that blocks the first light beam 61 of the first and second light beams 61, 62. The light-shielding portion 43 is located between the color filter 51 and the photoelectric conversion portion 42 and is provided on the photoelectric conversion portion 42. In the example shown in FIG. 5B , the light-shielding portion 43 is disposed so as to block the right half (the +X direction side) of the photoelectric conversion portion 42. The left end (the end in the −X direction) of the light-shielding portion 43 approximately coincides with the center line that divides the photoelectric conversion portion 42 into left and right halves. The photoelectric conversion portion 42 of the second focus detection pixel 12 receives the second light beam 62. The photoelectric conversion portion 42 of the second focus detection pixel 12 photoelectrically converts the second light beam 62 to generate an electric charge, and the second focus detection pixel 12 outputs a second signal Sig2 based on the electric charge generated by the photoelectric conversion portion 42.

[0054] As with the first focus detection pixels 11, the area of ​​the light-shielding portion 43 varies depending on the position (image height) of the second focus detection pixels 12, except for the second focus detection pixels 12 located around the optical axis OA1 (center of the imaging surface 22a) of the imaging optical system 31. The area of ​​the light-shielding portion 43 varies depending on the image height in order to block the first light beam 61 of light incident at different angles of incidence depending on the image height. The area of ​​the light-shielding portion 43 can be set according to the position (image height) of the focus detection pixel, for example, as disclosed in WO2020 / 017640.

[0055] 5C, the photoelectric conversion unit 42 of the imaging pixel 13 receives first and second light beams 61 and 62 that have passed through first and second pupil regions, respectively, of the exit pupil of the imaging optical system 31. The photoelectric conversion unit 42 of the imaging pixel 13 photoelectrically converts the first and second light beams 61 and 62 to generate electric charges, and the imaging pixel 13 outputs a signal (image signal) based on the electric charges generated by the photoelectric conversion unit 42.

[0056] As shown in FIG. 2A, the focus detection areas 100 are arranged two-dimensionally (in the row and column directions) and are provided at different image heights. A small area 110a (see FIG. 2B) within the focus detection area 100a at the center of the imaging surface 22a is located on the optical axis OA1 of the photographing optical system 31, and its image height H is approximately zero. The image height H of the focus detection area 100 increases as it moves away from the center of the imaging surface 22a (the optical axis OA1 of the photographing optical system 31). In other words, the image height H of the focus detection area 100 increases as its distance from the center of the imaging surface 22a increases. Therefore, in the row in which the focus detection area 100a is located, the focus detection areas 100 farthest from the optical axis OA1 of the photographing optical system 31 (having the highest image height H) are the focus detection areas 100b and 100c located at the left end (the end in the −X direction) and right end (the end in the +X direction) of the row. The focus detection areas 100 with the highest image height H in the image sensor 22 are the four focus detection areas 100 located at the corners of the image pickup surface 22a.

[0057] Note that, because the focus detection area 100 has a predetermined area, the image height varies for each focus detection pixel depending on its position within the focus detection area 100. Within the same focus detection area 100, the image height differs between the central small area 110a (see FIG. 2B) and the small areas 110b and 110c (see FIG. 2B) located at the left end (the end in the -X direction) and the right end (the end in the +X direction). However, in this embodiment, the value of the image height H at the center of one focus detection area 100 is used as the value of the image height of the entire focus detection area 100. The image height of the focus detection area 100a at the center of the imaging surface 22a is zero, and the image heights of the focus detection areas 100b and 100c are the predetermined image height H.

[0058] 1, the distance calculation unit 214 calculates the exit pupil distance of the photographing optical system 31 at the image height H. The distance calculation unit 214 calculates the exit pupil distance Po(H) of the photographing optical system 31 at the image height H of the focus detection area 100 set by the area setting unit 213 using a predetermined calculation formula. The predetermined calculation formula can be, for example, the following calculation formula (1), but may also be another calculation formula. Po(H)=h4×H ４ + h2 × H ２ +Co... (1)

[0059] Equation (1) is an equation with the image height H as a variable, where parameter (h4) is the coefficient of the fourth-order term of variable H, parameter (h2) is the coefficient of the second-order term of variable H, and constant term Co is the exit pupil distance at the position where the image height is zero (the position of the optical axis OA1 on the imaging plane 22a). The parameters (h4), (h2), and constant term Co are information regarding the exit pupil distance corresponding to different image heights, and are values ​​determined by the optical characteristics of the photographic optical system 31. Information indicating parameters (h4), (h2), and constant term Co is transmitted from the interchangeable lens 3 to the camera body 2 as lens information. Equation (1) is stored in an internal memory of the body control unit 21. The distance calculation unit 214 calculates the exit pupil distance Po(H) related to the image height H of the focus detection area 100 set by the area setting unit 213, based on the lens information (h4, h2, Co), and equation (1). The arithmetic formula (1) may be stored in an internal memory of the lens control unit 32. The lens control unit 32 may transmit the arithmetic formula (1) together with the parameters (h4), (h2) and the constant term Co from the interchangeable lens 3 to the camera body 2 as lens information.

[0060] The selection unit 215 selects which of the first to third AF pixel pairs PR1 to PR3 included in the pixel unit 221 to use for focus detection, output signals Sig1 and Sig2 from the AF pixel pair. In this embodiment, the selection unit 215 selects one type of AF pixel pair from the first to third AF pixel pairs PR1 to PR3 arranged in the focus detection area 100 set by the area setting unit 213. The selection unit 215 selects an AF pixel pair from the first to third AF pixel pairs PR1 to PR3 that is appropriate for the exit pupil distance Po(H) calculated by the distance calculation unit 214. Furthermore, when multiple focus detection areas 100 are set by the area setting unit 213, the selection unit 215 selects AF pixel pairs of the same type in each selected focus detection area 100.

[0061] The focus detection unit 216 performs focus detection processing required for automatic focus adjustment (AF) of the photographic optical system 31. The focus detection unit 216 calculates the defocus amount by a split-pupil phase difference detection method using signals Sig1 and Sig2 output from the AF pixel pair selected by the selection unit 215.

[0062] The focus detection unit 216 performs a correlation calculation between a first signal Sig1 generated by capturing an image formed by a first light beam that has passed through a first pupil region of the exit pupil of the photographing optical system 31 and a second signal Sig2 generated by capturing an image formed by a second light beam that has passed through a second pupil region, and calculates the amount of deviation between the image plane of the image formed by the photographing optical system 31 and the image plane 22a of the image sensor 22. The focus detection unit 216 converts this amount of deviation into a defocus amount based on a predetermined conversion formula.

[0063] Based on the defocus amount calculated by the focus detection unit 216, the position control unit 217 calculates the focus position of the focus lens 31b (the amount of movement of the focus lens 31b to the focus position) for the image from the shooting optical system 31 to be focused (formed) on the imaging surface 22a of the image sensor 22.

[0064] More specifically, the position control unit 217 determines whether the defocus amount is within a tolerance. If the defocus amount is within the tolerance, the position control unit 217 determines that the lens is in focus. On the other hand, if the defocus amount exceeds the tolerance, the position control unit 217 determines that the lens is not in focus, and sends a signal to the lens control unit 32 of the interchangeable lens 3 indicating the amount of movement of the focus lens 31b and an instruction to move the lens. The lens control unit 32 moves the focus lens 31b according to the amount of movement, thereby automatically adjusting the focus.

[0065] Here, if the "bird mode," suitable for photographing wild birds, etc., is not set as the shooting mode, the position control unit 217 determines whether the change in the defocus amount repeatedly calculated by the focus detection unit 216, i.e., the difference between the previously calculated defocus amount and the currently calculated defocus amount, falls within a first range. In this embodiment, focus adjustment is performed so that the previously calculated defocus amount becomes zero, so the change in the defocus amount can be considered to be the currently calculated defocus amount itself. If the change in the defocus amount does not fall within the first range, the position control unit 217 limits or prohibits focus adjustment of the shooting optical system 31 based on the calculated defocus amount for a first period of time. Hereinafter, the function of limiting or prohibiting focus adjustment of the shooting optical system 31 (AF lock-on) will be referred to as the AF lock-on function. While AF lock-on is being performed, focus adjustment of the shooting optical system 31 by the lens control unit 32 is limited or prohibited. Hereinafter, AF lock-on performed when the "bird mode" is not set will be referred to as the first AF lock-on.

[0066] The first AF lock-on is activated, for example, when a foreign object passes in front of the subject being photographed. That is, when the difference between the defocus amount previously calculated for the subject being photographed and the defocus amount currently calculated for the foreign object that has passed by it is greater than a predetermined threshold, focus adjustment is limited or prohibited for a first period of time. This prevents focus adjustment from being performed on the foreign object, allowing the subject being photographed to remain in focus. The first AF lock-on operates to maintain focus on a specific subject while tracking the specific subject. In addition to the above-mentioned case where a foreign object passes in front of the subject, the first AF lock-on is also activated, for example, when a moving subject temporarily deviates from the focus detection area while the camera 1 is being moved in accordance with the movement of the moving subject so that the moving subject always remains within the focus detection area.

[0067] Furthermore, when the "bird mode" is set as the shooting mode and the subject detection unit 212 detects a bird moving in a predetermined direction (e.g., flying) as the subject, the position control unit 217 determines whether the change in the defocus amount repeatedly calculated by the focus detection unit 216 falls within a second range. The second range is narrower than the first range. When the change in the defocus amount does not fall within the second range, the position control unit 217 limits or prohibits the focus adjustment operation of the shooting optical system 31 based on the calculated defocus amount for a second period of time (AF lock-on). The second period of time is longer than the first period of time. Hereinafter, AF lock-on performed when the "bird mode" is set will be referred to as second AF lock-on.

[0068] Here, the second range is assumed to be different when the subject is approaching the camera 1 and when the subject is moving away from the camera 1 .

[0069] For example, the first range is −M1 μm≦change in defocus amount≦+P1 μm (2) When the change in defocus amount is a negative value, it means that the object is defocused toward the close side (i.e., the object is in focus closer to the camera 1), and when the change in defocus amount is a positive value, it means that the object is defocused toward infinity (i.e., the object is in focus further back from the camera 1).

[0070] In contrast, the second range when the subject is approaching the camera 1 is −M2 μm≦change in defocus amount≦+P2 μm (3) The values ​​of M2 and P2 must satisfy the relationships M2≦M1 and P2<P1.

[0071] Furthermore, the second range when the subject is moving away from the camera 1 is -M2 μm≦change in defocus amount≦+(n×P2) μm (4). Note that n is a value equal to or greater than 1, and can be set to, for example, n=1.5. However, it is assumed that (n×P2)<P1. Note that the value of n may be a value according to the direction of movement of the subject (angular direction with respect to the optical axis of the photographing optical system 31). Note that the lower limit value (-M2) of the second range when the subject is approaching and when the subject is moving away may be different values.

[0072] 6A and 6B are diagrams for explaining focus detection based on the signals Sig1 and Sig2 output from the AF pixel pair selected by the selection unit 215. FIG.

[0073] As described above, the focus detection unit 216 uses the signals Sig1 and Sig2 output from the AF pixel pair selected by the selection unit 215 to calculate the defocus amount by a split-pupil phase difference detection method.

[0074] 6(a) and 6(b), it is assumed that the AF pixel pair selected by the selection unit 215 is the second AF pixel pair PR2. In FIG. 6(a) and 6(b), the second pixel set 400-2 including the second AF pixel pair PR2 is indicated by hatching.

[0075] 6A, when a portion of the subject image SBJ overlaps with the second pixel set 400-2 including the second AF pixel pair PR2, the focus detection unit 216 can calculate the defocus amount using the signals Sig1 and Sig2 output from the second AF pixel pair PR2, provided that the subject image SBJ is not in a state of large blur. On the other hand, when the subject image SBJ does not overlap with the second pixel set 400-2 including the second AF pixel pair PR2, that is, when the subject image SBJ is in a region where the first pixel set 400-1 including the first AF pixel pair PR1 and the third pixel set 400-3 including the third AF pixel pair PR3, which are not selected by the selection unit 215, are continuous, the focus detection unit 216 cannot calculate the defocus amount using the signals Sig1 and Sig2 output from the second AF pixel pair PR2, even if the subject image SBJ is near the in-focus state. Here, the region where a pixel group including an AF pixel pair not selected by the selection unit 215 is located is an area called a dead zone. In Figures 6(a) and 6(b), the non-hatched region is the dead zone, and is indicated by DZ.

[0076] The second AF lock-on described above is activated, for example, when: (1) when a subject (bird) is flying, as shown by the dashed frame in Fig. 7(a), the range AR in which the subject detection unit 212 detects the subject shifts from the actual position of the subject, and the area setting unit 213 sets an area for focus detection outside the subject (background) (when the defocus amount of the subject cannot be detected, but the defocus amount of the background is detected). The second AF lock-on is also activated when: (2) when a subject (bird) is flying, as shown by the dashed frame in Fig. 7(b), the range AR in which the subject detection unit 212 detects the subject coincides with the actual position of the subject, but the subject image SBJ is in the dead zone DZ, and only the defocus amount of the background can be detected.

[0077] In this embodiment, the time period for which the second AF lock-on is maintained (second time period) is set longer than the time period for which the first lock-on is maintained (first time period). This is because, when a bird is flying, the subject image SBJ may continue to be within the dead zone DZ, and the defocus amount of the bird may not be detected for a long time period.

[0078] (Regarding an example of operation of camera 1) Fig. 8 is a flowchart showing an example of operation of camera 1 according to this embodiment. The process shown in Fig. 8 is repeatedly executed, for example, while the release button (operation unit 25) is half-pressed. However, this is not limiting, and the process in Fig. 8 may also be executed while shooting video.

[0079] 8 starts, first, in step S10, the body control unit 21 (subject detection unit 212) of the camera body 2 determines whether the set shooting mode is "bird mode." If the determination in step S10 is affirmative (if bird mode), the process proceeds to step S30, but if the determination is negative (if other than bird mode), the process proceeds to step S12.

[0080] In step S12, the subject detection unit 212 detects a subject using an image based on image data generated by the image data generation unit 211 from a signal output from the image sensor 22. For example, if the set mode is "portrait mode," a person is detected as the subject. The area setting unit 213 also sets the focus detection area 100 corresponding to the area in which the subject was detected as the area in which focus detection is performed. In step S12, the distance calculation unit 214 and the selection unit 215 select which of the first to third AF pixel pairs PR1 to PR3 to use for focus detection, based on the image height of the focus detection area 100 set by the area setting unit 213.

[0081] Next, in step S14, the focus detection unit 216 uses the signals output from the AF pixel pair selected by the selection unit 215 to calculate (focus detection calculation) the defocus amount of the focus detection area 100 set by the area setting unit 213 as the area where focus detection is performed, using a pupil division type phase difference detection method.

[0082] Next, in step S16, the position control unit 217 calculates the difference between the defocus amount calculated in the previous focus detection calculation and the defocus amount calculated in the current focus detection calculation, i.e., the change in the defocus amount. In this embodiment, focus adjustment is performed so that the previously calculated defocus amount becomes zero, and then the current defocus amount is calculated. Therefore, the change in the defocus amount can be considered to be the value of the currently calculated defocus amount itself. The position control unit 217 then determines whether the change in the defocus amount falls within a predetermined first range (the range of the above formula (2)). If the determination in step S16 is positive (if the above formula (2) is satisfied), the process proceeds to step S18, where the position control unit 217 performs focus adjustment so that the defocus amount calculated in step S14 falls within an allowable value (e.g., zero). Then, the process returns to step S10.

[0083] On the other hand, if the determination in step S16 is negative (if the above formula (2) is not satisfied), the process proceeds to step S20, where the position control unit 217 activates the first AF lock-on function to limit or prohibit focus adjustment operations for a first period of time. This prevents focus adjustment operations from being performed on a foreign object that passes in front of the subject, making it possible to maintain focus on the subject. After that, all the processing in FIG. 8 ends, but when the first period of time has elapsed, the processing in FIG. 8 is restarted.

[0084] 8 is restarted, the previous defocus amount is reset. That is, after the process of FIG. 8 is restarted, the change in the defocus amount is not calculated when the process first proceeds to step S16 after steps S12 and S14, and the determination in step S16 is affirmative. That is, in step S18, the position control unit 217 performs focus adjustment based on the defocus amount calculated in step S14. Thereafter, the same process as described above is executed.

[0085] If the determination in step S10 is affirmative (if the camera is in "bird mode"), the process proceeds to step S30, where the subject detection unit 212 detects the subject (bird) using an image based on image data generated by the image data generation unit 211 from a signal output from the image sensor 22. The area setting unit 213 sets the focus detection area 100 corresponding to the area in which the subject was detected as the area in which focus detection is performed. In step S30, similar to step S12, the distance calculation unit 214 and the selection unit 215 select which of the first to third AF pixel pairs PR1 to PR3 to use for focus detection, based on the image height of the focus detection area 100 set by the area setting unit 213.

[0086] Next, in step S32, the subject detection unit 212 determines whether or not the subject (bird) is flying. If the determination in step S32 is negative, the process proceeds to step S16, and the processes in step S16, S18, or S20 are executed.

[0087] On the other hand, if the determination in step S32 is positive (if the subject (bird) is flying), the process proceeds to step S34, where the subject detection unit 212 determines whether the subject is flying in a direction approaching the camera 1. Note that in step S34, the subject detection unit 212 may determine whether the subject is flying in a direction away from the camera 1.

[0088] If the determination in step S34 is positive, the process proceeds to step S36, where the focus detection unit 216 uses the signals output from the AF pixel pair selected by the selection unit 215 to calculate (focus detection calculation) the defocus amount of the focus detection area 100 set by the area setting unit 213 as the area where focus detection is to be performed, using a pupil-splitting phase difference detection method, as in step S14.

[0089] 9(a) to 9(c) are diagrams showing specific examples of an area AR (dashed line frame) where a subject is detected, a focus detection area 100' (solid line frame) where focus detection is performed, and the defocus amount (numerical value) for each focus detection area. In Figures 9(a) to 9(c), a subject (a bird flying toward the camera 1) is detected in the area AR shown in the dashed line frame, and focus detection is performed in the focus detection area 100' shown in the thick line frame.

[0090] 9A is a diagram showing a state in which the subject is properly detected and focus detection is performed in the proper focus detection area 100'. In FIG. 9A, a defocus amount of 26 μm is detected. In this embodiment, focus adjustment is performed so that the previously calculated defocus amount becomes 0, so the change in the defocus amount can be said to be 26 μm.

[0091] In contrast, Figure 9(b) shows a state in which the subject is not properly detected (a position outside the subject is detected as the subject) and focus detection is performed in an inappropriate focus detection area 100. In Figure 9(b), the defocus amount (amount of change in defocus amount) detected is the defocus amount on the background side (1053 μm).

[0092] 9C shows a state in which the subject is properly detected, but the subject image is in the dead zone DZ, so the defocus amount detected is the background defocus amount (956 μm).

[0093] Next, in step S38, the position control unit 217 determines whether the change in the defocus amount is within the range of the above formula (3). For example, if M2 in the above formula (3) is 600 and P2 is 350, the above formula (3) becomes the following formula (5): -600 μm≦change in the defocus amount≦+350 μm (5)

[0094] In this case, in the example of FIG. 9A, the determination in step S38 is positive, and in the examples of FIG. 9B and FIG. 9C, the determination in step S38 is negative.

[0095] If the determination in step S38 is positive, the process proceeds to step S18, where the position control unit 217 performs focus adjustment so that the defocus amount calculated in step S36 falls within an allowable value (for example, 0). Thereafter, the process returns to step S10.

[0096] On the other hand, if the determination in step S38 is negative, the process proceeds to step S40, where the position control unit 217 activates a second AF lock-on to limit or prohibit focus adjustment for a second period of time. In this embodiment, by executing the second AF lock-on when the determination in step S38 is negative, it is possible to prevent focus adjustment based on the detected defocus amount when a defocus amount on the background is detected, as shown in FIGS. 9B and 9C. This makes it possible to prevent a situation in which the subject is out of focus and the background is in focus. After that, the entire process in FIG. 8 ends, but the process in FIG. 8 is restarted when the second period of time has elapsed.

[0097] 8 (when the subject (bird) is flying away from the camera 1), the process proceeds to step S42. In step S42, the focus detection unit 216, similar to steps S14 and S36, uses the signals output from the AF pixel pair selected by the selection unit 215 to calculate the defocus amount of the focus detection area 100 set by the area setting unit 213 as the area where focus detection is performed, by a split-pupil phase difference detection method (focus detection calculation).

[0098] Next, in step S44, the position control unit 217 determines whether the change in the defocus amount is within the range of the above formula (4). For example, if M2 in the above formula (4) is 600, P2 is 350, and n is 1.5, then the above formula (4) becomes the following formula (6): -600 μm≦change in the defocus amount≦+525 μm (6)

[0099] In this case, if the change in the defocus amount is, for example, 450 μm, the determination in step S44 is positive, and if it is, for example, 1000 μm, the determination in step S44 is negative.

[0100] If the determination in step S44 is positive, the process proceeds to step S18, where the position control unit 217 performs focus adjustment so that the defocus amount calculated in step S42 falls within an allowable value (for example, 0). Thereafter, the process returns to step S10.

[0101] On the other hand, if the determination in step S44 is negative, the process proceeds to step S40, where the position control unit 217 activates the second AF lock-on function to limit or prohibit focus adjustment for a second period of time. In this embodiment, by performing the second AF lock-on when the determination in step S44 is negative, it is possible to prevent a situation in which the subject is out of focus and the background is in focus. After that, all the processing in FIG. 8 ends, but when the second period of time has elapsed, the processing in FIG. 8 is restarted.

[0102] 8 is restarted after step S40, the previous defocus amount is reset. That is, after the process of FIG. 8 is restarted, when the process first proceeds to step S38 or S44 after step S36 or S42, the amount of change in the defocus amount is not calculated, and the determination in step S38 or S44 is affirmative. That is, in step S18, the position control unit 217 performs focus adjustment based on the defocus amount calculated in step S36 or S42. Thereafter, the same process as described above is executed.

[0103] As described above in detail, according to this embodiment, the camera 1 includes an image sensor 22 having focus detection pixels that photoelectrically convert light transmitted through the photographic optical system 31 and output signals used for focus detection of the photographic optical system 31, and imaging pixels that photoelectrically convert light transmitted through the photographic optical system 31 and output signals used for generating an image. The camera 1 also includes a focus detection unit 216 that detects the amount of deviation (defocus amount) between the image plane of the photographic optical system 31 and the imaging plane of the image sensor 22 based on the signals output from the focus detection pixels. The camera 1 also includes a position control unit 217 that controls the position of the photographic optical system 31 based on the defocus amount if the defocus amount (amount of change) is within the range defined by equation (2) above when a subject (bird) is not flying, and controls the position of the photographic optical system 31 based on the defocus amount if the defocus amount (amount of change) is within the range defined by equation (3) or (4) above when a subject (bird) is flying. As a result, if the subject is not a flying bird, when a foreign object passes in front of the subject, focus adjustment to the foreign object is prevented, and the subject can be kept in focus (first AF lock-on). Furthermore, if the subject is a flying bird, even if a defocus amount on the background is detected as shown in Figures 9(b) and 9(c), focus adjustment to focus on the background can be prevented, allowing the subject to be kept in focus with high accuracy (second AF lock-on). Furthermore, by making the second range for determining whether to perform the second AF lock-on narrower than the first range for determining whether to perform the first AF lock-on, it is possible to appropriately determine whether to perform each AF lock-on.

[0104] In this embodiment, the ranges on the infinity side (the range of positive values) of the above formulas (2) and (3) are narrower than the range on the infinity side (the range of positive values) of the above formula (1), which effectively prevents focus adjustments that focus on the background when the subject (bird) is flying.

[0105] Furthermore, in this embodiment, the focus detection unit 216 detects the amount of defocus based on a signal from the focus detection area 100 corresponding to the area in which the subject (bird) was detected by the subject detection unit 212. This increases the possibility of detecting the amount of defocus of the subject image.

[0106] In this embodiment, the time period during which the second AF lock-on is performed (second time period) is longer than the time period during which the first AF lock-on is performed (first time period). As a result, even in cases where the subject (bird) is flying and remains in the dead zone, the process of FIG. 8 can be resumed at an appropriate timing.

[0107] Furthermore, in this embodiment, the second range (the above formula (4)) when the subject (bird) is flying away from the camera 1 is set wider than the second range (the above formula (3)) when the subject (bird) is flying towards the camera 1. This allows for appropriate focus adjustment depending on the flight direction of the subject.

[0108] In the above embodiment, if the shooting mode of the camera 1 is not the "bird mode," step S18 may be performed after steps S12 and S14 without performing step S16. In other words, AF lock-on may not be performed in modes other than the "bird mode."

[0109] (Variation 1) In the above embodiment, when the shooting mode of camera 1 is "bird mode," position control unit 217 may monitor the size of the subject detected by subject detection unit 212 and the confidence level of subject detection by subject detection unit 212, and change the second range when the detection size and the confidence level show a predetermined change. Note that the confidence level of subject detection refers to a statistical measure (likelihood) that indicates how certain it is that the subject is a bird when subject detection unit 212 detects a subject using machine learning or the like.

[0110] For example, suppose that when a subject (bird) is flying, the detection size increases by a certain amount (above the first threshold) and the confidence level decreases by a certain amount (above the second threshold) (see FIG. 10(a)). In this case, while the subject (bird) is in the dead zone DZ, the subject (bird) approaches camera 1, but the subject cannot be focused on (becomes very blurred), which is considered to be the reason for the decrease in confidence level. In such a case, the range on the close side of the second range may be widened (the value of M2 in the above formula (3) may be increased) so that the subject can be focused on once it leaves the dead zone DZ.

[0111] Also, for example, suppose that when a subject (bird) is flying, the detection size becomes smaller by a certain amount (above the first threshold) and the confidence level drops by a certain amount (above the second threshold) (see FIG. 10(b)). In this case, it is considered that while the subject (bird) is in the dead zone DZ, the subject (bird) moves away from camera 1, making it impossible to focus on the subject (becoming very blurred), and thus causing the confidence level to drop. In such a case, the range on the infinity side of the second range may be widened (the upper limit value of the above formula (4) may be increased) so that the subject can be focused on when it leaves the dead zone DZ.

[0112] (Variation 2) For example, in the above embodiment, suppose that while the processing of FIG. 8 is being executed, the second AF lock-on is not performed for some reason, and therefore the subject is not properly detected (see dashed frame AR), as shown in FIG. 11(a) , and focus detection is performed in the focus detection area 100′ indicated by the thick frame, and the position control unit 217 performs focus adjustment based on the defocus amount (950 μm) within the thick frame.

[0113] Even if the subject is properly detected from this state, as shown in Figure 11(b), the defocus amount of the focus detection area 100' indicated by the thick frame is large, so the second AF lock-on is performed and focus adjustment to focus on the bird is not performed. To deal with this situation, simply press the release button halfway again, which restarts the process shown in Figure 8 and allows the subject to be focused. However, photographers photographing birds often use a red dot sight, and the photographer may not realize that the subject is out of focus.

[0114] Therefore, in this second variant, in order to enable the photographer to focus on the bird without half-pressing the release button, the position control unit 217 monitors the confidence level when the subject is detected by the subject detection unit 212, and when the confidence level rises above a certain level (above a third threshold), the second AF lock-on is temporarily prevented from being performed (for example, by expanding the range on the close side of the second range).

[0115] By doing this, it becomes possible to focus on the subject (bird) at the stage where the subject is properly detected as shown in Figure 11(b) from a state where the subject is not properly detected and the background is in focus as shown in Figure 11(a).

[0116] (Variation 3) In Variation 3, the shooting mode of camera 1 is also set to "bird mode." As shown in FIG. 12( a), suppose the photographer half-presses the release button while camera 1 is shooting a subject, a bird, perched on a branch. In this case, subject detection unit 212 detects the bird perched on the branch as the subject. Furthermore, focus detection unit 216 performs focus adjustment based on the amount of defocus near the bird.

[0117] On the other hand, if a bird jumps into the water in the background from the state shown in Figure 12(a), as shown in Figure 12(c), the subject detection area may not be able to keep up with the bird's movement, and the subject detection area may remain near the branch, resulting in the branch being in focus. Also, even if the subject detection area later matches the position of the bird, if the defocus amount of the bird is outside the second AF lock-on range (second range), it may not be possible to focus on the bird.

[0118] It is possible that the bird will be brought into focus if the photographer presses the release button halfway again, but the moment the bird dives into the water is so fleeting that it is difficult to press the button halfway again instantly.

[0119] Therefore, in this third modification, as shown in Fig. 12(a), the histogram of the defocus amount for each focus detection area is monitored for each frame after the release button is half-pressed while the camera 1 is capturing an image of a subject, a bird, perched on a branch. Fig. 12(b) schematically shows a histogram (frequency distribution) of the defocus amount when the image of Fig. 12(a) is being captured. In the case of Fig. 12(a), the defocus amount for the bird and branch is 0 to 150 μm, and the defocus amount for the water surface (background) is 1350 to 1500 μm, resulting in a histogram like that shown in Fig. 12(b).

[0120] On the other hand, Fig. 12(d) shows a histogram (frequency distribution) when the image in Fig. 12(c) was captured. In the case of Fig. 12(c), the defocus amount of the branch is 0 to 150 μm, the defocus amount of the water surface (background) is 1350 to 1500 μm, and the defocus amount of the bird is 600 to 750 μm, so the histogram shown in Fig. 12(d) is obtained.

[0121] In this case, when the subject detection area coincides with the flying bird (when the subject detection unit 212 detects the flying bird as the subject), the position control unit 217 compares a histogram (first frequency distribution) such as that shown in FIG. 12( b ) obtained at a first timing immediately before the bird takes flight with a histogram (second frequency distribution) such as that shown in FIG. 12( d ) obtained after the bird takes flight (second timing). The position control unit 217 confirms the difference between the two histograms through this comparison and identifies the portion of FIG. 12( d ) where the frequency is high (the range of the defocus amount). The position control unit 217 then determines that the identified range of the defocus amount (the range of 600 to 750 μm in FIG. 12( d )) is the defocus amount range of the bird, and temporarily expands the second range (the second range) so that this range is included in the second AF lock-on range. This allows the position control unit 217 to adjust the focus based on the defocus amount of the bird when the subject detection area coincides with the flying bird (when the subject detection unit 212 detects the flying bird as the subject), and to focus on the bird.

[0122] (Variation 4) When a bird is flying and there is little defocus difference between the bird and the background (when the bird is flying close to the background), if the bird enters the dead zone, the second AF lock-on described above may not function, and focus adjustment may be performed based on the amount of defocus of the background. Such focus adjustment based on the amount of defocus of the background will be referred to as background cut-out below.

[0123] In order to prevent such background loss from occurring, the following countermeasures are implemented in the fourth modification.

[0124] In this fourth modification, when the shooting mode of the camera 1 is set to "bird mode" and the subject detection unit 212 detects a flying bird as a subject, the position control unit 217 sets a defocus calculation frame DR (bold frame) wider than the flying bird detection area AR (dashed frame), as shown in FIG. 13( a). Then, as shown in FIG. 13( b), the position control unit 217 sets multiple contrast evaluation frames CR within the defocus calculation frame DR and calculates the contrast value (contrast evaluation value) within each contrast evaluation frame CR. The position control unit 217 then identifies the contrast evaluation frame CR with the maximum contrast value and performs focus adjustment based on the detection result (defocus amount) of the focus detection area corresponding to the identified contrast evaluation frame CR. For example, if the contrast of the contrast evaluation frame CR indicated by the white frame in FIG. 13( b) is maximum, the position control unit 217 performs focus adjustment based on the detection result (defocus amount) of the focus detection area corresponding to the white frame. Since the contrast value of the bird is higher than the contrast value of the background, the focus detection area corresponding to the position of the bird can be identified by using the contrast value.

[0125] By doing this, even if the subject detection area (dashed frame) shifts from the actual position of the bird, as shown in Figure 13(c), focus adjustment can be performed using the defocus amount of the focus detection area with the maximum contrast value (focus detection area within the white frame), making it possible to focus on the bird without causing the background to fall out.

[0126] (Variation 5) In the above embodiment, the second AF lock-on is performed if the change in defocus amount is not within the second range based on equations (3) and (4). However, this is not limiting. The position control unit 217 may convert the change in defocus amount detected by the focus detection unit 216 into an absolute distance, and perform the second AF lock-on if the absolute distance is longer than a predetermined distance corresponding to the subject. The predetermined distance corresponding to the subject may be, for example, the distance a bird can travel in the time corresponding to one frame. For example, the distance a bird can travel in the time corresponding to one frame for a peregrine falcon, the fastest bird, is approximately 390 km / h, or 0.10833 m / ms. Therefore, the movement amount per frame is approximately 1 m at 120 fps, approximately 2 m at 60 fps, and approximately 4 m at 30 fps. This allows the second range to be appropriately set, and the second AF lock-on to be appropriately performed.

[0127] (Variation 6) When the shooting mode of the camera 1 is set to "bird mode," the position control unit 217 may detect the defocus amounts of all focus detection areas, create a histogram, and set the second range based on the histogram, as shown in FIG. 14 , when a flying bird is detected as a subject. In the case of FIG. 14 , the range (D1) of 258 μm to 738 μm is considered to represent the defocus amount of the background, and the range (D2) of values ​​smaller than 258 μm is considered to represent the defocus amount of the bird. Therefore, the maximum value of the range H2 may be set as the upper limit value of the second range (P2 in the above formula (3)). Note that the upper limit value of the second range (P2 in the above formula (3)) may be 1 / m (where m is 2, 3, etc.) of the maximum value of the range H2. In this way, even when the defocus difference between the background and the subject is small, the second range for determining whether or not to perform second AF lock-on can be set to an appropriate range.

[0128] (Other Modifications) In the above embodiment, the processing of steps S34 to S40 in FIG. 8 and the processing of each of the above-described modifications are described when the shooting mode of camera 1 is "bird mode" and the subject is a flying bird. However, this is not limited to this. For example, when the shooting mode of camera 1 is "airplane mode" and the subject is a flying airplane, the processing of steps S34 to S40 in FIG. 8 and the processing of each of the above-described modifications may be performed. Furthermore, when the shooting mode of camera 1 is "sports mode" and the subject is a running person, the processing of steps S34 to S40 in FIG. 8 and the processing of each of the above-described modifications may be performed. Furthermore, when the subject is a specific subject performing a predetermined movement, the processing of steps S34 to S40 in FIG. 8 and the processing of each of the above-described modifications may be performed.

[0129] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this and can be modified in various ways without departing from the spirit of the present invention.

[0130] REFERENCE SIGNS LIST 1 camera 2 camera body 3 interchangeable lens 4 focus detection device 11, 12 focus detection pixel 13 imaging pixel 21 body control unit 22 imaging element 25 operation unit 31 photographing optical system 31b focus lens 211 image data generation unit 212 subject detection unit 213 area setting unit 214 distance calculation unit 215 selection unit 216 focus detection unit 217 position control unit 222 control unit PR1 first AF pixel pair PR2 second AF pixel pair PR3 third AF pixel pair Sig1, Sig2 signals

Claims

1. An imaging device comprising: an imaging unit having a first pixel that photoelectrically converts light transmitted through an optical system and outputs a signal used for focus detection of the optical system, and a second pixel that photoelectrically converts light transmitted through the optical system and outputs a signal used for generating an image; a detection unit that detects an amount of deviation between an image plane of the optical system and an imaging plane of the imaging unit based on the signal output from the first pixel; and a control unit that controls a position of the optical system based on the amount of deviation if the subject is not moving in a predetermined manner and the amount of deviation is within a first range, and controls the position of the optical system based on the amount of deviation if the subject is moving in a predetermined manner and the amount of deviation is within a second range narrower than the first range.

2. The imaging device according to claim 1, wherein the range on the infinity side of the second range is narrower than the range on the infinity side of the first range.

3. An imaging device according to claim 1 or 2, wherein the detection section detects the amount of deviation based on a signal from the first pixel arranged in an area of ​​the imaging surface of the imaging section that includes a subject.

4. The imaging device described in any one of claims 1 to 3, wherein the control unit does not control the position of the optical system until a first time has elapsed if the subject is not performing the specified movement and the amount of deviation is not within the first range, and does not control the position of the optical system until a second time longer than the first time has elapsed if the subject is performing the specified movement and the amount of deviation is not within the first range.

5. An imaging device as described in any one of claims 1 to 4, wherein, when the subject is performing the specified movement, the second range when the subject's movement direction is a direction away from the imaging device is wider than the second range when the subject's movement direction is other than a direction away from the imaging device.

6. An imaging device as claimed in any one of claims 1 to 5, further comprising an analysis unit that analyzes the movement of a subject, said analysis unit calculating a degree of certainty indicating the accuracy of said analysis when it is determined that the subject is making the specified movement.

7. The imaging device of claim 6, wherein the control unit widens the second range when, while the subject is performing the specified movement, the confidence level decreases by more than a first threshold and the size of the image of the subject changes by more than a second threshold.

8. An imaging device as described in claim 6 or 7, wherein the control unit, when the subject is performing the specified movement, widens the range on the close side of the second range when the certainty level increases to or above a third threshold value.

9. The imaging device described in claim 6, wherein the control unit generates a first frequency distribution of the amount of deviation at a first timing, generates a second frequency distribution of the amount of deviation at a second timing after the first timing when the analysis unit analyzes that the subject is performing the specified movement, and determines the second range based on the difference between the first frequency distribution and the second frequency distribution.

10. An imaging device as described in any one of claims 1 to 8, wherein, when the subject is performing the specified movement, the control unit sets a detection area including the subject, calculates an evaluation value for contrast of each of the multiple detection ranges based on the output of the second pixel included in the multiple detection ranges within the detection area, and detects the amount of deviation based on the signal from the first pixel included in the detection range among the multiple detection ranges that has the highest evaluation value.

11. An imaging device as described in any one of claims 1 to 8, wherein, when the subject is performing the specified movement, the control unit converts the difference between the amount of deviation detected by the detection unit at a first timing and the amount of deviation detected by the detection unit at a second timing after the first timing into an absolute distance, and when the converted absolute distance is greater than a specified distance corresponding to the subject, does not control the position of the optical system based on the amount of deviation at the second timing.

12. An imaging device described in any one of claims 1 to 8, wherein the control unit generates a frequency distribution of the amount of deviation when the subject is performing the specified movement, and determines the second range based on the frequency distribution.

13. An imaging device according to any one of claims 1 to 12, wherein the predetermined movement is flying or traversal.

Images