Imaging element and imaging apparatus

Abstract

To improve focus detection accuracy.SOLUTION: An imaging element includes a pair of first AF pixels and a pair of second AF pixels which have a photoelectric conversion part for photoelectrically converting light after passing through an optical system, to generate an electric charge, have different areas for receiving the light because the photoelectric conversion parts have different widths for receiving the light, and output signals used for focus detection based on the electric charge generated by the photoelectric conversion part respectively, and an output part which outputs the signals from the pair of first AF pixels or the pair of second AF pixels according to the selection of the focus detection by the pair of first AF pixels or the focus detection by the pair of second AF pixels based on first information relating to a position in an image surface and the exit pupil distance of the optical system.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an imaging element and an imaging apparatus. [Background technology]

[0002] There is known an imaging apparatus that performs focus detection by selecting an AF pixel pair according to the exit pupil position of a lens from a plurality of types of AF pixel pairs (Patent Document 1). There has been a demand for improving the accuracy of focus detection. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2009-204987 Summary of the Invention

[0004] According to a first aspect of the invention, an image sensor has a photoelectric conversion unit that performs photoelectric conversion on light that has passed through an optical system to generate electric charges, and the photoelectric conversion units have different widths at which they receive light, resulting in different areas for receiving light, and the image sensor is equipped with a first pixel and a second pixel that each output a signal used for focus detection based on the charges generated by the photoelectric conversion unit, and an output unit that outputs a signal from the first pixel or the second pixel depending on a selection of focus detection by the first pixel or focus detection by the second pixel based on first information related to a position on the image plane and an exit pupil distance of the optical system. According to a second aspect of the invention, an imaging device includes the imaging element of the first aspect, and a generating section that generates image data based on a signal output from the imaging element. [Brief description of the drawings]

[0005] [Figure 1] 1 is a diagram illustrating an example of a configuration of an imaging device according to a first embodiment. [Diagram 2] 1 is a diagram showing a focus detection area on an imaging surface of an imaging device according to a first embodiment. [Diagram 3]2 is a diagram showing an example of pixel arrangement in a focus detection area of ​​the image pickup device according to the first embodiment. FIG. [Figure 4] 1 is a diagram illustrating an example of a pixel configuration in an imaging device according to a first embodiment. [Diagram 5] 2 is a cross-sectional view showing three types of AF pixel pairs arranged in a central region in the image pickup device according to the first embodiment. FIG. [Figure 6] 2 is a cross-sectional view showing three types of AF pixel pairs arranged in an area at a predetermined image height position in the imaging device according to the first embodiment. FIG. [Figure 7] 2 is a cross-sectional view showing three types of AF pixel pairs arranged in an area at a predetermined image height position in the imaging device according to the first embodiment. FIG. [Figure 8] 4 is a diagram showing the relationship between a reference exit pupil and an image height in the imaging device according to the first embodiment. FIG. [Figure 9] 1 shows various optical characteristics of an interchangeable lens in an imaging device according to a first embodiment, in which the exit pupil distance changes depending on the image height. [Figure 10] 3 is a diagram showing the relationship between the image height and the exit pupil in the imaging device according to the first embodiment. FIG. [Figure 11] 4 is a table showing focus position intervals in the imaging device according to the first embodiment and constant terms and coefficients of functions that approximate representative optical characteristic curves in the focus position intervals. [Figure 12] 4 is a table showing sections in the imaging device according to the first embodiment and constant terms and coefficients of functions that approximate representative optical characteristic curves in the sections. [Figure 13] FIG. 2 is a diagram showing a threshold value related to the exit pupil distance, first to third exit pupil distance ranges, and an optical characteristic curve in the image pickup device according to the first embodiment. [Figure 14] 4 is a flowchart illustrating an operation of the imaging device according to the first embodiment. [Figure 15] 4 is a flowchart illustrating an operation of the imaging device according to the first embodiment. [Figure 16]4 is a flowchart illustrating an operation of the imaging device according to the first embodiment. [Figure 17] 2 is a diagram illustrating an example of the configuration of a focus detection pixel in the imaging device according to the first embodiment. [Figure 18] 13 shows how an exit pupil image changes depending on the image height in an imaging device according to a second embodiment. [Figure 19] 13 is a diagram showing the relationship between a pair of photoelectric conversion units and an exit pupil image in an imaging device according to a second embodiment. FIG. [Figure 20] 13 is a block diagram showing a plurality of functions executed by a focus detection unit in an imaging device according to a second embodiment, with each function being divided into blocks. FIG. [Figure 21] 10 is a flowchart illustrating an operation of an imaging device according to a second embodiment. [Figure 22] 13 is a diagram showing an example of the configuration of a focus detection pixel in an imaging device according to a modified example. [Figure 23] 13 is a diagram showing an example of the configuration of a focus detection pixel in an imaging device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] (First embodiment) 1 is a diagram showing an example of the configuration of an electronic camera 1 (hereinafter referred to as camera 1), which is an example of an imaging device according to a first embodiment. Camera 1 is made up of a camera body 2 and an interchangeable lens 3. As camera 1 is made up of the camera body 2 and the interchangeable lens 3, it is also sometimes called a camera system.

[0007] The camera body 2 is provided with a body side mount section 201 to which the interchangeable lens 3 is attached. The interchangeable lens 3 is provided with a lens side mount section 301 to which it is attached to the camera body 2. The lens side mount section 301 and the body side mount section 201 are provided with a lens side connection section 302 and a body side connection section 202, respectively. The lens side connection section 302 and the body side connection section 202 are each provided with a plurality of 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 section 301 and the body side mount section 201.

[0008] When the interchangeable lens 3 is attached to the camera body 2, a terminal provided on the body side connection part 202 is electrically connected to a terminal provided on the lens side connection part 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.

[0009] The interchangeable lens 3 includes a photographing optical system (imaging optical system) 31, a lens control unit 32, and a lens memory 33. The photographing 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 illustrated in FIG. 1, a normal photographing optical system is generally composed of a large number of optical elements.

[0010] As 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 on the imaging plane 22a. The optical axis OA1 of the photographing optical system 31 intersects with the imaging plane 22a at the center position 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 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, is arranged, or a surface on which a microlens is arranged. Furthermore, the photographic optical system 31 differs depending on the type of interchangeable lens 3 attached to the body side mount portion 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.

[0011] The lens control unit 32 is configured with a processor such as a CPU, FPGA, or ASIC, and a memory such as a ROM or RAM, and controls each part 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 aperture 31c based on a signal output from the body control unit 210 of the camera body 2. When a signal indicating the movement direction and movement amount of the focus lens 31b is input from the body control unit 210, the lens control unit 32 moves the focus lens 31b forward and backward in the direction of the optical axis OA1 based on the signal to adjust the focal position of the photographing optical system 31. The lens control unit 32 also controls the position of the zoom lens 31a and the opening diameter of the aperture 31c based on a signal output from the body control unit 210 of the camera body 2.

[0012] 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 value) of the photographing optical system 31, data on the infinity position and the closest position of the focus lens 31b, and data on the shortest focal length and the longest focal length of the interchangeable lens 3. The optical characteristics of the photographing optical system 31 include the exit pupil distance and F value (aperture value of the aperture 31c). The lens information differs depending on the type of the interchangeable lens 3. The lens information may be stored in a memory inside the lens control unit 32. The lens information may be stored in a body memory 23 included in the camera body 2 described later. In this case, the body memory 23 stores lens information on a plurality of interchangeable lenses 3.

[0013] In this embodiment, the lens information includes information on the exit pupil distance of the photographing optical system 31. The information on the exit pupil distance, which will be described later, includes information indicating the exit pupil distance (Co) at the position where the imaging surface 22a and the optical axis OA1 intersect (the position where the image height is zero), and information on coefficients (h4, h2) included in an arithmetic expression that represents the relationship between the exit pupil distance and the image height. Writing of data to the lens memory 33 and reading of 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 the lens information to the body control unit 210 via the terminals of the lens side connection unit 302 and the body side connection unit 202. In addition, the lens control unit 32 transmits position information (focal length information) of the controlled zoom lens 31a, position information of the controlled focus lens 31b, information on the F value of the controlled aperture 31c, and the like to the body control unit 210. In this embodiment, the lens control unit 32 functions as an output unit that transmits information regarding the exit pupil distance of the photographing optical system 31 to the camera body 2. The body control unit 210 functions as an input unit to which information regarding the exit pupil distance of the photographing optical system 31 is input from the interchangeable lens 3.

[0014] Furthermore, 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 transmission of information (h4, h2, Co) relating to the exit pupil distance is input from the camera body 2, the lens control unit 32 transmits the information relating to the exit pupil distance to the camera body 2. Note that the information relating to the exit pupil distance differs depending on the type of the interchangeable lens 3. Furthermore, the lens control unit 32 may transmit the information relating to the exit pupil distance to the camera body 2 every time the image sensor 22 captures an image. The lens control unit 32 may transmit the information relating to the exit pupil distance to the camera body 2 when the zoom lens 31a moves and the focal length of the photographing optical system 31 changes. The lens control unit 32 may transmit the information relating to the focal length of the photographing optical system 31 and the information relating to the exit pupil distance to the camera body 2 in one bidirectional communication.

[0015] Next, the configuration of the camera body 2 will be described. The camera body 2 includes an image sensor 22, a body memory 23, a display unit 24, an operation unit 25, and a body control unit 210. The image sensor 22 is a CMOS image sensor or a CCD image sensor. The image sensor 22 captures a subject image formed by a photographing optical system 31. The image sensor 22 has a plurality of pixels, each having a photoelectric conversion unit, arranged two-dimensionally (in row and column directions). The photoelectric conversion unit is composed of a photodiode (PD). The image sensor 22 photoelectrically converts received light in the photoelectric conversion unit to generate a signal, and outputs the generated signal to the body control unit 210.

[0016] As described later, the image sensor 22 has imaging pixels that output signals used for image generation, and focus detection pixels that output signals used for focus detection. The imaging pixels include pixels (hereinafter referred to as R pixels) having filters with spectral characteristics that separate light in a first wavelength range (red (R) light) from the incident light, pixels (hereinafter referred to as G pixels) having filters with spectral characteristics that separate light in a second wavelength range (green (G) light) from the incident light, and pixels (hereinafter referred to as B pixels) having filters with spectral characteristics that separate light in a third wavelength range (blue (B) light) from the incident light. The R pixels, G pixels, and B pixels are arranged according to a Bayer array. The focus detection pixels are arranged by replacing some of the imaging pixels, and are distributed over almost the entire image sensor surface 22a of the image sensor 22.

[0017] The body memory 23 is composed of, for example, a non-volatile storage medium. Image data, control programs, and the like 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 210. The display unit 24 displays an image based on the image data, an image showing a focus detection area (AF area) such as an AF frame, information related to shooting such as a shutter speed and an F value, and a menu screen. The operation unit 25 includes various setting switches such as a release button, a power switch, and a switch for switching between various modes, and outputs an operation signal according to each operation to the body control unit 210. In addition, the operation unit 25 is a setting unit that can set an arbitrary focus detection area from a plurality of focus detection areas, and a user can select an arbitrary focus detection area by operating the operation unit 25.

[0018] The body control unit 210 is configured with a processor such as a CPU, FPGA, or ASIC, and a memory such as a ROM or RAM, and controls each unit of the camera 1 based on a control program. The body control unit 210 has an image data generation unit 211, an area setting unit 212, a distance calculation unit 213, a selection unit 214, and a focus detection unit 215. The image data generation unit 211 generates image data by performing various image processes 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.

[0019] The area setting unit 212 sets (selects) at least one of the multiple focus detection areas 100 provided on the imaging surface 22a of the image sensor 22 shown in FIG. 2(a). The multiple AF frames displayed on the display unit 24 correspond to the multiple focus detection areas 100 provided on the image sensor 22. The area setting unit 212 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, or the focus detection area 100 automatically selected by the camera 1, among the multiple AF frames displayed on the display unit 24. As will be described later, the focus detection unit 215 detects the amount of deviation (defocus amount) between the image by the photographing optical system 31 and the imaging surface 22a, using a signal output from a focus detection pixel in the focus detection area 100 set by the area setting unit 212.

[0020] As shown in FIG. 2(b) as a schematic diagram, the focus detection area 100 includes, in addition to imaging pixels, a plurality of types of pairs of focus detection pixels (AF pixel pairs), and in this embodiment, a first AF pixel pair, a second AF pixel pair, and a third AF pixel pair. The first AF pixel pair, the second AF pixel pair, and the third AF pixel pair are arranged in order to accurately detect the defocus amount even at exit pupil distances that differ depending on the image height or the type of interchangeable lens. One focus detection pixel constituting the AF pixel pair outputs a first signal Sig1, and the other focus detection pixel constituting the AF pixel pair outputs a second signal Sig2. The first AF pixel pair, the second AF pixel pair, and the third AF pixel pair will be described later.

[0021] As shown in FIG. 2A, the focus detection areas 100 are arranged in two dimensions (row and column directions) and are provided at positions with different image heights. A small area 110a (see FIG. 2B) in 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 the 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 (end in the -X direction) and right end (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.

[0022] Since the focus detection area 100 has a predetermined area, the image height of each focus detection pixel differs depending on the position within the focus detection area 100. Within the same focus detection area 100, the image height differs between the small area 110a at the center (see FIG. 2(b)) and the small areas 110b and 110c (see FIG. 2(b)) located at the left end (end in the -X direction) and the right end (end in the +X direction). However, in this embodiment, the value of the image height H at the center position of one focus detection area 100 is set to 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.

[0023] The distance calculation unit 213 calculates the exit pupil distance of the photographing optical system 31 at the image height H. The distance calculation unit 213 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 212 by the following formula (1). Po(H) = h4 × H 4 +h2×H 2 +Co …(1) Equation (1) is an arithmetic expression with the image height H as a variable, where the parameter (h4) is the coefficient of the fourth-order term of the variable H, the parameter (h2) is the coefficient of the second-order term of the variable H, and the 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 surface 22a). The parameters (h4), (h2), and the constant term Co are information on the exit pupil distance corresponding to different image heights, and are values ​​determined by the optical characteristics of the photographing optical system 31. Information indicating the parameters (h4), (h2), and the constant term Co is transmitted from the interchangeable lens 3 to the camera body 2 as lens information. Note that this arithmetic expression (1) is stored in the internal memory of the body control unit 210. The distance calculation unit 213 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 212, based on the lens information (h4, h2, Co), and arithmetic expression (1). The arithmetic formula (1) may be stored in a memory inside 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.

[0024] The selection unit 214 selects which of the multiple types of AF pixel pairs provided in the image sensor 22 should use to perform focus detection, the first and second signals Sig1, Sig2 output from the AF pixel pair. In this embodiment, the selection unit 214 selects one of the multiple types of AF pixel pairs arranged in the focus detection area 100 set by the area setting unit 212. As will be described later, the selection unit 214 selects an AF pixel pair suitable for the exit pupil distance Po(H) calculated by the distance calculation unit 213 from among the multiple types of AF pixel pairs. In addition, when multiple focus detection areas 100 are set by the area setting unit 212, the selection unit 214 selects AF pixel pairs of the same type in each selected focus detection area 100.

[0025] The focus detection unit 215 performs focus detection processing required for automatic focus adjustment (AF) of the photographing optical system 31. The focus detection unit 215 detects the in-focus position (the amount of movement of the focus lens 31b to the in-focus position) of the focus lens 31b for focusing (forming) an image by the photographing optical system 31 on the imaging surface 22a of the image sensor 22. The focus detection unit 215 calculates the defocus amount by a pupil division type phase difference detection method using the first and second signals Sig1 and Sig2 output from the AF pixel pair selected by the selection unit 214. The focus detection unit 215 calculates the amount of image shift by performing a correlation calculation between a first signal Sig1 generated by capturing an image by a first light beam passing 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 by a second light beam passing through a second pupil region. The focus detection unit 215 converts this amount of image shift into a defocus amount based on a predetermined conversion formula. The focus detection unit 215 calculates the amount of movement of the focus lens 31b to the in-focus position based on the calculated defocus amount.

[0026] The focus detection unit 215 judges whether the defocus amount is within a tolerance. If the defocus amount is within the tolerance, the focus detection unit 215 judges that the focus is achieved. On the other hand, if the defocus amount exceeds the tolerance, the focus detection unit 215 judges that the focus is not achieved, and transmits to the lens control unit 32 of the interchangeable lens 3 the movement amount of the focus lens 31b and a signal instructing lens movement. The lens control unit 32 moves the focus lens 31b according to the movement amount, thereby automatically adjusting the focus.

[0027] The focus detection unit 215 can also perform focus detection processing using a contrast detection method in addition to focus detection processing using a phase difference detection method. The body control unit 210 sequentially calculates the contrast evaluation value of the subject image based on the signal output from the imaging pixel while moving the focus lens 31b of the imaging optical system 31 in the direction of the optical axis OA1. The body control unit 210 associates the position of the focus lens 31b with the contrast evaluation value using position information of the focus lens 31b transmitted from the interchangeable lens 3. The body control unit 210 then detects the position of the focus lens 31b where the contrast evaluation value is at its peak, i.e., the maximum value, as the in-focus position. The body control unit 210 transmits information on the position of the focus lens 31b corresponding to the detected in-focus position to the lens control unit 32. The lens control unit 32 moves the focus lens 31b to the in-focus position to adjust the focus.

[0028] Fig. 3 is a diagram showing an example of pixel arrangement in 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 row direction, are arranged alternately in the ±Y directions, i.e., in the column direction. The imaging pixels 13 are arranged according to a Bayer array.

[0029] Some of the second pixel groups 402 include the first or second focus detection pixels 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 by second pixel groups 402a, 402c, and 402e, and the second pixel groups 402 including the second focus detection pixel 12 are indicated by 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.

[0030] In the second pixel group 402a, the B pixel 13 is replaced with the first focus detection pixel 11a. In the second pixel group 402a, the first focus detection pixel 11a and the G pixel 13 are alternately arranged. The photoelectric conversion unit of the first focus detection pixel 11a receives a light beam that has passed through one of the first and second pupil regions of the exit pupil of the photographing optical system 31. The light shielding unit of the first focus detection pixel 11a shields a light beam that has 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, the photoelectric conversion unit of the first focus detection pixel 11a receives a light beam that has passed through the first pupil region of the exit pupil of the photographing optical system 31. The light shielding unit of the first focus detection pixel 11a shields a light beam that has passed through the second pupil region of the exit pupil of the photographing optical system 31.

[0031] In the second pixel group 402b, which is a predetermined row away from the second pixel group 402a, the B pixel 13 is replaced with the second focus detection pixel 12a. In the second pixel group 402b, the second focus detection pixel 12a and the G pixel 13 are alternately arranged. The photoelectric conversion unit of the second focus detection pixel 12a receives a light beam that has passed through a pupil region of an exit pupil different from that of the first focus detection pixel 11a. The light shielding unit of the second focus detection pixel 11a shields the light beam that has 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 unit of the second focus detection pixel 12a receives a light beam that has passed through a second pupil region of the exit pupil of the photographing optical system 31. The light shielding unit of the second focus detection pixel 12a shields the light beam that has passed through a first pupil region of the exit pupil of the photographing optical system 31.

[0032] The position of the first focus detection pixel 11a in the second pixel group 402a is the same as the position of the second focus detection pixel 12a in the second pixel group 402b. That is, the first focus detection pixel 11a and the second focus detection pixel 12a are arranged in the same column. 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 configure a first AF pixel pair. Note that the second pixel group 402a and the second pixel group 402b may be arranged in multiple rows to provide multiple first AF pixel pairs.

[0033] In the second pixel group 402c, which is a predetermined row away from the second pixel group 402b, the B pixel 13 is replaced with the first focus detection pixel 11b. In the second pixel group 402c, the first focus detection pixel 11b and the G pixel 13 are arranged alternately. 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, similar to the first focus detection pixel 11a. The light shielding unit of the first focus detection pixel 11b shields the light beam that has passed through a second pupil region of the exit pupil of the photographing optical system 31, similar to the first focus detection pixel 11a.

[0034] In the second pixel group 402d, which is a predetermined row away from the second pixel group 402c, the B pixels 13 are replaced with the second focus detection pixels 12b. In the second pixel group 402d, the second focus detection pixels 12b and the G pixels 13 are arranged alternately. The photoelectric conversion unit of the second focus detection pixel 12b receives the light beam that has passed through a second pupil region of the exit pupil of the photographing optical system 31, similar to the second focus detection pixel 12a. The light shielding unit of the second focus detection pixel 12b shields the light beam that has passed through a first pupil region of the exit pupil of the photographing optical system 31, similar to the second focus detection pixel 12a.

[0035] The position of the first focus detection pixel 11b in the second pixel group 402c and the position of the second focus detection pixel 12b in the second pixel group 402d are the same as each other, that is, the first focus detection pixel 11b and the second focus detection pixel 12b are arranged in the same column. 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 configure a second AF pixel pair. Note that the second pixel group 402c and the second pixel group 402d may be arranged in multiple rows to provide multiple second AF pixel pairs.

[0036] In the second pixel group 402e, which is a predetermined row away from the second pixel group 402d, the B pixel 13 is replaced with the first focus detection pixel 11c. In the second pixel group 402e, the first focus detection pixel 11c and the G pixel 13 are arranged alternately. The photoelectric conversion unit of the first focus detection pixel 11c receives the light beam that has passed through a first pupil region of the exit pupil of the photographing optical system 31, similar to the first focus detection pixels 11a and 11b. The light shielding unit of the first focus detection pixel 11c shields the light beam that has passed through a second pupil region of the exit pupil of the photographing optical system 31, similar to the first focus detection pixels 11a and 11b.

[0037] In the 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 the 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 unit of the second focus detection pixel 12c receives a light beam that has passed through a second pupil region of the exit pupil of the photographing optical system 31. The light shielding unit of the second focus detection pixel 12c shields the light beam that has passed through a first pupil region of the exit pupil of the photographing optical system 31, similar to the second focus detection pixels 12a and 12b.

[0038] 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 as each other, that is, the first focus detection pixel 11c and the second focus detection pixel 12c are arranged in the same column. 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 configure a third AF pixel pair. Note that the second pixel group 402e and the second pixel group 402f may be arranged in multiple rows to provide multiple third AF pixel pairs.

[0039] The areas of the light shielding portions 43 of the first AF pixel pair, the second AF pixel pair, and the third AF pixel pair are different, except for the pixel pairs around the optical axis OA1 (the center of the imaging surface 22a) of the photographing optical system 31. When the exit pupil distance is different, the incident angle of the light incident on the focus detection pixels is different, except for the focus detection pixels around the optical axis OA1 of the photographing optical system 31. When the exit pupil distance is short, the incident angle is large, and when the exit pupil distance is long, the incident angle is small. In order to block a part of the light incident at an incident angle that differs depending on the exit pupil distance, the area of ​​the light shielding portions 43 differs depending on the AF pixel pair. This allows the focus detection unit 215 to detect the defocus amount with high accuracy even at different exit pupil distances. However, the incident angle of the pixel pairs around the optical axis OA1 (the center of the imaging surface 22a) of the photographing optical system 31 is 0° regardless of the exit pupil distance. Therefore, the first AF pixel pair, the second AF pixel pair, and the third AF pixel pair have the same area of ​​the light-shielding portion 43. As will be described later, the area of ​​the light-shielding portion 43 also differs depending on the position (image height) of the focus detection pixel.

[0040] In this embodiment, the first focus detection pixels 11a, 11b, and 11c and the second focus detection pixels 12a, 12b, and 12c each have a filter having a spectral characteristic of separating light in a second wavelength range (green (G) light) from the incident light. The filter of each of the first focus detection pixels 11a to 11c and the second focus detection pixels 12a to 12c may be a filter having a spectral characteristic of separating light in a first wavelength range (red (R) light) or light in a third wavelength range (blue (B) light). The first focus detection pixels 11a to 11c and the second focus detection pixels 12a to 12c may also have a filter having a spectral characteristic of separating light in a first, second, and third wavelength ranges from the incident light.

[0041] Fig. 4 is a diagram for explaining an example of the configuration of focus detection pixels and imaging pixels provided in the image sensor 22 according to the first embodiment. Fig. 4(a) shows an example of a cross section of the first focus detection pixel 11 of the first and second focus detection pixels 11, 12 constituting an AF pixel pair, and Fig. 4(b) shows an example of a cross section of the second focus detection pixel 12 of the first and second focus detection pixels 11, 12. Fig. 4(c) shows an example of a cross section of an imaging pixel 13 (R pixel, G pixel, B pixel).

[0042] 4, 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 (PD42) that photoelectrically converts light transmitted (passed) through the microlens 44 and the color filter 51. The first light beam 61 is a light beam that has passed through a first pupil region that approximately halves the exit pupil of the photographing optical system 31. The second light beam 62 is a light beam that has passed through a second pupil region that approximately halves the exit pupil of the photographing optical system 31.

[0043] In FIG. 4A, the first focus detection pixel 11 is provided with a light shielding portion 43L that shields the second light beam 62 of the first and second light beams 61 and 62. The light shielding portion 43L 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. 4A, the light shielding portion 43L is disposed so as to shield the left half (-X direction side) of the photoelectric conversion portion 42. The right end (end in the +X direction) of the light shielding portion 43L approximately coincides with the center line that divides the photoelectric conversion portion 42 into two equal parts to the left and right. 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.

[0044] The area of ​​the light shielding portion 43L differs depending on the position (image height) of the first focus detection pixel 11, except for the first focus detection pixel 11 located around the optical axis OA1 (center of the imaging surface 22a) of the photographing optical system 31. When the position of the first focus detection pixel 11 differs, that is, when the image height differs, the angle of incidence of light incident on the first focus detection pixel 11 differs. When the image height is high, the angle of incidence becomes large, and when the image height is low, the angle of incidence becomes small, and when the image height is 0, the angle of incidence is 0°. The area of ​​the light shielding portion 43L differs depending on the image height in order to shield the second light flux 62 from the light incident at an angle of incidence that differs depending on the image height.

[0045] In FIG. 4B, the second focus detection pixel 12 is provided with a light shielding portion 43R that shields the first light beam 61 of the first and second light beams 61 and 62. The light shielding portion 43R 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. 4B, the light shielding portion 43R is disposed so as to shield 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 43R approximately coincides with the center line that divides the photoelectric conversion portion 42 into two equal parts to the left and right. 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.

[0046] Like the first focus detection pixel 11, the area of ​​the light-shielding portion 43R differs depending on the position (image height) of the second focus detection pixel 12, except for the second focus detection pixel 12 located around the optical axis OA1 (the center of the imaging surface 22a) of the photographing optical system 31. The area of ​​the light-shielding portion 43R differs depending on the image height in order to block the first light flux 61 of the light incident at an incident angle that differs depending on the image height.

[0047] 4(c), the photoelectric conversion unit 42 of the imaging pixel 13 receives first and second light beams 61, 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 performs photoelectric conversion on the first and second light beams 61, 62 to generate electric charges, and the imaging pixel 13 outputs a signal based on the electric charges generated by the photoelectric conversion unit 42.

[0048] FIG. 5 is a cross-sectional view of three types of AF pixel pairs arranged in a small region 110a (see FIG. 2(b)) in the focus detection region 100a. FIG. 5(a) shows the first and second focus detection pixels 11a and 12a constituting a first AF pixel pair arranged in the second pixel groups 402a and 402b of FIG. 3, respectively. FIG. 5(b) shows the first and second focus detection pixels 11b and 12b constituting a second AF pixel pair arranged in the second pixel groups 402c and 402d of FIG. 3, respectively. FIG. 5(c) shows the first and second focus detection pixels 11c and 12c constituting a third AF pixel pair arranged in the second pixel groups 402e and 402f of FIG. 3, respectively. 5, in each of the first focus detection pixels 11a to 11c and the second focus detection pixels 12a to 12c, a line passing through the center of the photoelectric conversion unit 42 and the optical axis OA2 of the microlens 44 approximately coincide with each other. Light incident at an incident angle of 0° with respect to the optical axis OA2 of the microlens 44 is focused on the optical axis OA2 of the microlens 44. Since the line passing through the center of the photoelectric conversion unit 42 coincides with the optical axis OA2 of the microlens 44, light incident on the microlens 44 is focused on a line passing through the center of the photoelectric conversion unit 42. In other words, light transmitted through the photographing optical system 31 is focused on a line passing through the center of the photoelectric conversion unit 42.

[0049] In FIG. 5A, in the first focus detection pixel 11a, the right end (end in the +X direction) of the light-shielding portion 43L substantially coincides with the optical axis OA2 of the microlens 44. The light-shielding portion 43L of the first focus detection pixel 11a shields the left half (-X direction side) of the photoelectric conversion unit 42. The second light flux 62 transmitted through the microlens 44 is shielded by the light-shielding portion 43L before entering the photoelectric conversion unit 42. As a result, the photoelectric conversion unit 42 of the first focus detection pixel 11a receives the first light flux 61. In the second focus detection pixel 12a, the left end (end in the -X direction) of the light-shielding portion 43R substantially coincides with the optical axis OA2 of the microlens 44. The first light flux 61 transmitted through the microlens 44 is shielded by the light-shielding portion 43R before entering the photoelectric conversion unit 42. As a result, the photoelectric conversion unit 42 of the second focus detection pixel 12 a receives the second light flux 62 .

[0050] 5(b) and (c), in each of the first focus detection pixels 11b and 11c, the right end (end in the +X direction) of the light-shielding portion 43L substantially coincides with the optical axis OA2 of the microlens 44. Therefore, similar to the first focus detection pixel 11a, the photoelectric conversion unit 42 in each of the first focus detection pixels 11b and 11c receives the first light flux 61. Moreover, in each of the second focus detection pixels 12b and 12c, the left end (end in the -X direction) of the light-shielding portion 43R substantially coincides with the optical axis OA2 of the microlens 44. Therefore, similar to the first focus detection pixel 12a, the photoelectric conversion unit 42 in each of the second focus detection pixels 12b and 12c receives the second light flux 62.

[0051] Figure 6 is a cross-sectional view of three types of AF pixel pairs arranged in a small region 110c (see Figure 2(b)) located in the +X direction away from a small region 110a in the focus detection area 100a. Figure 6(a) shows first and second focus detection pixels 11a, 12a constituting a first AF pixel pair. Figure 6(b) shows first and second focus detection pixels 11b, 12b constituting a second AF pixel pair. Figure 6(c) shows first and second focus detection pixels 11c, 12c constituting a third AF pixel pair.

[0052] 6, in each of the first focus detection pixels 11a to 11c and the second focus detection pixels 12a to 12c, a line passing through the center of the photoelectric conversion unit 42 is offset in the +X direction with respect to the optical axis OA2 of the microlens 44. In this embodiment, in the first and second focus detection pixels arranged away from the small region 110a in the +X direction, a line passing through the center of the photoelectric conversion unit 42 is offset in the +X direction with respect to the optical axis OA2 of the microlens 44. Also, in the first and second focus detection pixels arranged away from the small region 110a in the -X direction, a line passing through the center of the photoelectric conversion unit 42 is offset in the -X direction with respect to the optical axis OA2 of the microlens 44.

[0053] 6, the areas of the light-shielding portions 43L of the first focus detection pixels 11a to 11c are different. The area of ​​the light-shielding portion 43L of the first focus detection pixel 11a is smaller than the area of ​​the light-shielding portion 43L of the first focus detection pixel 11b. The area of ​​the light-shielding portion 43L of the first focus detection pixel 11b is smaller than the area of ​​the light-shielding portion 43L of the first focus detection pixel 11c. The areas of the light-shielding portions 43R of the second focus detection pixels 12a to 12c are different. The area of ​​the light-shielding portion 43R of the second focus detection pixel 12a is larger than the area of ​​the light-shielding portion 43R of the second focus detection pixel 12b. The area of ​​the light-shielding portion 43R of the second focus detection pixel 12b is larger than the area of ​​the light-shielding portion 43R of the second focus detection pixel 12c.

[0054] 6, a line passing through the center of the photoelectric conversion unit 42 is misaligned with the optical axis OA2 of the microlens 44, and the areas of the light-shielding units 43 of the first and second focus detection pixels are different, so that the ends of the light-shielding units of the first and second focus detection pixels are misaligned with the optical axis OA2 of the microlens 44. In FIG. 6(a), for example, the right end (end in the +X direction) of the light-shielding unit 43L of the first focus detection pixel 11a is located on the +X direction side of the optical axis OA2 of the microlens 44 by a shift amount d1. Also, the left end (end in the -X direction) of the light-shielding unit 43R of the second focus detection pixel 12a is located on the +X direction side of the optical axis OA2 of the microlens 44 by a shift amount d1.

[0055] As shown in Fig. 6, the second and third AF pixel pairs and the first AF pixel pair have different amounts of deviation. The amount of deviation d2 between the first and second focus detection pixels 11b, 12b that make up the second AF pixel pair is larger than the amount of deviation d1 between the first and second focus detection pixels 11a, 12a that make up the first AF image pair. The amount of deviation d3 between the first and second focus detection pixels 11c, 12c that make up the third AF pixel pair is larger than the amount of deviation d2 between the first and second focus detection pixels 11b, 12b that make up the second AF image pair. In other words, d1 <d2<d3である。

[0056] Fig. 7 is a cross-sectional view of some three types of AF pixel pairs in a focus detection area 100c that is away from the focus detection area 100a in the +X direction in Fig. 2. Fig. 7(a) shows the first and second focus detection pixels 11a, 12a that make up a first AF pixel pair. Fig. 7(b) shows the first and second focus detection pixels 11b, 12b that make up a second AF pixel pair. Fig. 7(c) shows the first and second focus detection pixels 11c, 12c that make up a third AF pixel pair.

[0057] Like the three types of AF pixel pairs shown in Fig. 6, in each of the first focus detection pixels 11a to 11c and second focus detection pixels 12a to 12c shown in Fig. 7, a line passing through the center of the photoelectric conversion unit 42 is shifted in the +X direction with respect to the optical axis OA2 of the microlens 44. Also, like the three types of AF pixel pairs shown in Fig. 6, the first focus detection pixels 11a to 11c have light-shielding portions 43L with different areas, and the second focus detection pixels 12a to 12c have light-shielding portions 43R with different areas.

[0058] The three types of AF pixel pairs shown in FIG. 6 and FIG. 7 have different amounts of deviation of the line passing through the center of the photoelectric conversion unit 42 with respect to the optical axis OA2 of the microlens 44. Also, except for the first focus detection pixel 11b and the second focus detection pixel 12b, the areas of the light-shielding portion 43L and the light-shielding portion 43R are different. The three types of AF pixel pairs shown in FIG. 7 have a larger amount of deviation with respect to the optical axis OA2 of the microlens 44 compared to FIG. 6. Also, the first focus detection pixel 11a and the second focus detection pixel 12a shown in FIG. 7 have a smaller area of ​​the light-shielding portion 43L and a larger area of ​​the light-shielding portion 43R compared to FIG. 6. The first focus detection pixel 11c and the second focus detection pixel 12c shown in FIG. 7 have a larger area of ​​the light-shielding portion 43L and a smaller area of ​​the light-shielding portion 43R compared to FIG. 6. The first focus detection pixel 11b and the second focus detection pixel 12b shown in FIG. 7 have the same area as the light shielding portion 43L and the same area as the light shielding portion 43R in FIG.

[0059] In the first focus detection pixel 11a, the right end (end in the +X direction) of the light shielding portion 43L is shifted in the +X direction by a shift amount d4 with respect to the optical axis OA2 of the microlens 44. In the second focus detection pixel 12a, the left end (end in the -X direction) of the light shielding portion 43R is shifted in the +X direction by a shift amount d4 with respect to the optical axis OA2 of the microlens 44.

[0060] The second and third AF pixel pairs and the first AF pixel pair have different amounts of deviation. The amount of deviation d5 of the first and second focus detection pixels 11b, 12b that make up the second AF pixel pair is larger than the amount of deviation d4 of the first and second focus detection pixels 11a, 12a that make up the first AF image pair. The amount of deviation d6 of the first and second focus detection pixels 11c, 12c that make up the third AF pixel pair is larger than the amount of deviation d5 of the first and second focus detection pixels 11b, 12b that make up the second AF image pair. In other words, d4 <d5<d6である。

[0061] As shown in FIG. 5, FIG. 6, and FIG. 7, the amount of deviation between the line passing through the center of the photoelectric conversion unit 42 and the optical axis OA2 of the microlens 44 varies depending on the image height. The higher the image height, the greater the amount of deviation, and the lower the image height, the smaller the amount of deviation. At a position where the image height is high, the light transmitted through the photographing optical system 31 is obliquely incident on the microlens 44. That is, the light is incident on the optical axis OA2 of the microlens 44 at an incident angle greater than 0°. Therefore, it can be said that the greater the incident angle of the light on the microlens 44, the greater the amount of deviation. The light incident on the optical axis OA2 of the microlens 44 at an incident angle greater than 0° is focused while being shifted from the optical axis OA2 of the microlens in the +X direction or the -X direction. As the line passing through the center of the photoelectric conversion unit 42 is shifted from the optical axis OA2 of the microlens 44, the light incident on the microlens 44 is focused on the line passing through the center of the photoelectric conversion unit 42. That is, the light transmitted through the photographing optical system 31 is focused on the line passing through the center of the photoelectric conversion unit 42. This allows the amount of light passing through the photographing optical system 31 and entering the photoelectric conversion section 42 to be increased.

[0062] As shown in FIG. 5, FIG. 6, and FIG. 7, the area of ​​the light-shielding portion 43 differs depending on the AF pixel pair. As described above, the exit pupil distance of the photographing optical system 31 differs depending on the type of the interchangeable lens 3. Therefore, the first AF pixel pair, the second AF pixel pair, and the third AF pixel pair each have a light-shielding portion 43 with a different area in order to accurately detect the defocus amount at a different exit pupil distance. In addition, the area of ​​the light-shielding portion 43L and the area of ​​the light-shielding portion 43R of the first AF pixel pair differ depending on the position (image height) at which the first AF pixel pair is arranged. As described above, the exit pupil distance of the photographing optical system 31 differs depending on the image height. Therefore, the first AF pixel pair has the light-shielding portion 43L and the light-shielding portion 43R with areas that change depending on the image height in order to accurately detect the defocus amount at a different exit pupil distance. The third AF pixel pair is similar to the first AF pixel pair. This allows the focus detection unit 215 to detect the defocus amount with high accuracy even when the exit pupil distance is different. That is, the focus detection unit 215 can detect the defocus amount with high accuracy even when the image height or the type of interchangeable lens changes.

[0063] Therefore, the amount of deviation between the light-shielding portion 43 of the first to third AF pixel pairs and the optical axis of the microlens 44 increases as the image height increases in the +X direction from the small region 110a in FIG. 2(b) to the region with a higher image height. Comparing the deviation amounts of the first to third AF pixel pairs in three regions with image heights of Ha, Hb, and Hc (Ha < Hb < Hc), the following results are obtained. The deviation amount of the first AF pixel pair in the region with image height Hb is larger than the deviation amount of the first AF pixel pair in the region with image height Ha and smaller than the deviation amount of the first AF pixel pair in the region with image height Hc. Similarly, the deviation amounts of the second and third AF pixel pairs in the region with image height Hb are larger than the deviation amounts of the second and third AF pixel pairs in the region with image height Ha and smaller than the deviation amounts of the second and third AF pixel pairs in the region with image height Hc, respectively. The deviation amount d4 of the first AF pixel pair arranged in the focus detection region 100c shown in FIG. 7 is larger than the deviation amount d1 of the first AF pixel pair arranged in the small region 110c shown in FIG. 6. The deviation amounts d5 and d6 of the second and third AF pixel pairs arranged in the focus detection region 100c shown in FIG. 7 are larger than the deviation amounts d2 and d3 of the second and third AF pixel pairs arranged in the small region 110c shown in FIG. 6, respectively.

[0064] For the first to third AF pixel pairs arranged in the small region 110b that is separated from the small region 110a in FIG. 2(b) in the -X direction, deviation amounts similar to the deviation amounts d1 to d3 are applied in the direction opposite to the deviation direction shown in FIG. 6. For the first to third AF pixel pairs arranged in the focus detection region 100b in FIG. 2(a), deviation amounts similar to the deviation amounts d4 to d6 are applied in the direction opposite to the deviation direction shown in FIG. 7. The deviation amounts of the first to third AF pixel pairs arranged at a distance in the -X direction from the small region 110a also increase as the image height increases.

[0065] As described above, the first to third AF pixel pairs have different amounts of deviation. Therefore, in a plane intersecting the direction in which light is incident, the areas in which the photoelectric conversion units 42 of the first focus detection pixels 11a to 11c receive light are different from each other, and the areas in which the photoelectric conversion units 42 of the second focus detection pixels 12a to 12c receive light are different from each other. In this manner, in this embodiment, the first to third AF pixel pairs have different light receiving areas of the photoelectric conversion units 42, and therefore can perform pupil division in response to different angles of incidence. This allows the focus detection unit 215 to detect the defocus amount with high accuracy.

[0066] Next, an example of a method for determining the amount of deviation of the first to third AF pixel pairs in the focus detection area 100 will be described. In FIG. 8, the position of the small area 110 located at the image height Hd from the position 0 (the center position of the imaging surface 22a) where the optical axis OA1 of the photographing optical system 31 intersects with the imaging surface 22a of the image sensor 22 is represented by 110α. A first reference exit pupil EP1, a second reference exit pupil EP2, and a third reference exit pupil EP3 are set on the OA1 of the photographing optical system 31. The second reference exit pupil EP2 is located closer to the imaging surface 22a than the first reference exit pupil EP1, and is located on the +Z direction side of the first reference exit pupil EP1. The third reference exit pupil EP3 is located closer to the imaging surface 22a than the second reference exit pupil EP2, and is located on the +Z direction side of the second reference exit pupil EP2. The distance between the first reference exit pupil EP1 and the imaging surface 22a is the first reference exit pupil distance Po1, the distance between the second reference exit pupil EP2 and the imaging surface 22a is the second reference exit pupil distance Po2, and the distance between the third reference exit pupil EP3 and the imaging surface 22a is the third reference exit pupil distance Po3, where Po1>Po2>Po3.

[0067] 8, L1 indicates the chief ray of the light beam that passes through the first reference exit pupil EP1 and is incident on a focus detection pixel in the small region 110 at position 110α. L2 indicates the chief ray of the light beam that passes through the second reference exit pupil EP2 and is incident on a focus detection pixel in the small region 110 at position 110α. L3 indicates the chief ray of the light beam that passes through the third reference exit pupil EP3 and is incident on a focus detection pixel in the small region 110 at position 110α.

[0068] In FIG. 8, assuming that θ1 is the incident angle of the principal ray L1 to the focus detection pixel, the deviation amount of the first AF pixel pair within the small region 110 of the image height Hd is determined based on the incident angle θ1. Similarly, assuming that θ2 and θ3 are the incident angles of the principal rays L2 and L3 to the focus detection pixels, respectively, the deviation amounts of the second and third AF pixel pairs within the small region 110 of the image height Hd are determined based on the incident angles θ2 and θ3, respectively. As described above, the deviation amount increases as the incident angle increases. Also, except for the position where the image height is 0 (position 0), the incident angle becomes smaller as the exit pupil distance is longer, so θ1 < θ2 < θ3. Therefore, the deviation amounts d1, d2, and d3 of the first, second, and third AF pixel pairs shown in FIGS. 6(a) to 6(c) satisfy d1 < d2 < d3. Also, the deviation amounts d4, d5, and d6 of the first, second, and third AF pixel pairs shown in FIGS. 7(a) to 7(c) satisfy d4 < d5 < d6.

[0069] In this way, the deviation amount of the first AF pixel pair with respect to the first reference exit pupil EP1 (first reference exit pupil distance Po1) is determined. Similarly, the deviation amount of the second AF pixel pair with respect to the second reference exit pupil EP2 (second reference exit pupil distance Po2) is determined, and the deviation amount of the third AF pixel pair with respect to the third reference exit pupil EP3 (third reference exit pupil distance Po3) is determined.

[0070] Next, the relationship between the exit pupil distance of the imaging optical system 31 and the first to third AF pixel pairs will be described. In FIG. 8, a first threshold Th1 related to the exit pupil distance is set at an intermediate position between the first reference exit pupil EP1 and the second reference exit pupil EP2, and a second threshold Th2 related to the exit pupil distance is provided at an intermediate position between the second reference exit pupil EP2 and the third reference exit pupil EP3. The region where the exit pupil distance is equal to or greater than the first threshold Th1 is defined as the first exit pupil distance range R1, the region where the exit pupil distance is between the first threshold Th1 and the second threshold Th2 is defined as the second exit pupil distance range R2, and the region where the exit pupil distance is equal to or less than the second threshold Th2 is defined as the third exit pupil distance range R3.

[0071] The selection unit 214 selects the first AF pixel pair when the exit pupil distance of the photographing optical system 31 is equal to or greater than the first threshold value Th1, i.e., when it belongs to the first exit pupil distance range R1. The selection unit 214 selects the second AF pixel pair when the exit pupil distance of the photographing optical system 31 is between the first threshold value Th1 and the second threshold value Th2, i.e., when it belongs to the second exit pupil distance range R2. The selection unit 214 selects the third AF pixel pair when the exit pupil distance of the photographing optical system 31 is equal to or less than the second threshold value Th2, i.e., when it belongs to the third exit pupil distance range R3. As described above, the selection unit 214 selects an appropriate AF pixel pair from the first to third AF pixel pairs depending on which of the first to third exit pupil distance ranges R1 to R3 the exit pupil distance of the photographing optical system belongs to.

[0072] Next, the optical characteristics of the photographing optical system 31 of the interchangeable lens 3, that is, the optical characteristics in which the exit pupil distance changes depending on the image height, will be described. FIG. 9 shows the optical characteristics of the interchangeable lens 3 mounted on the camera body 2 of FIG. 1 in which the exit pupil distance changes depending on the image height. In FIG. 9, the horizontal axis represents the exit pupil distance Po, and the vertical axis represents the image height H. FIGS. 9(a), (b), (c), and (d) show the optical characteristics of different types of interchangeable lenses. The optical characteristics of the photographing optical system 31 of the interchangeable lens 3 shown in FIG. 9(a) are represented by an optical characteristic curve 200a, and the exit pupil distance Po decreases as the image height H increases. The optical characteristic curve 200a in FIG. 9(a) shows that the exit pupil distance is Poa at an image height of zero, and the exit pupil distance gradually decreases as the image height H increases, and the exit pupil distance becomes (Poa-Δp1) at the maximum image height Hmax.

[0073] The optical characteristic of the photographing optical system 31 of the interchangeable lens 3 shown in Fig. 9(b) is represented by an optical characteristic curve 200b, and the exit pupil distance Po increases as the image height H increases. The optical characteristic curve 200b in Fig. 9(b) indicates that the exit pupil distance is Pob at an image height of zero, and as the image height H increases, the exit pupil distance gradually increases, until the exit pupil distance becomes (Pob+Δp2) at the maximum image height Hmax. In the following description, an optical characteristic curve in which the exit pupil distance Po decreases as the image height H increases, such as the optical characteristic curve 200a, is referred to as a negative optical characteristic curve, and an optical characteristic curve in which the exit pupil distance Po increases as the image height H increases, such as the optical characteristic curve 200b, is referred to as a positive optical characteristic curve.

[0074] The photographing optical system 31 of the interchangeable lens 3 shown in FIG. 9(c) has an optical characteristic curve that differs, i.e., changes, depending on the position of the focus lens 31b in FIG. 1. This photographing optical system 31 exhibits an optical characteristic curve 200c when the focus lens 31b is located at a first position, and exhibits an optical characteristic curve 200d when the focus lens 31b is located at a second position. The first and second positions of the focus lens 31b are any positions between the infinity position and the close position, including the infinity position and the close position of the focus lens 31b. The infinity position of the focus lens 31b is a position where an object at an infinite distance is focused, and the close position is a position where an object at a close distance is focused.

[0075] In FIG. 9C, an optical characteristic curve 200c represents the optical characteristic of the photographing optical system 31 when the focus lens 31b is located at the first position. The optical characteristic curve 200c represents that the exit pupil distance is Poc at an image height of zero, the exit pupil distance gradually decreases as the image height H increases, and the exit pupil distance is (Poc-Δp3) at the maximum image height Hmax. The optical characteristic curve 200d represents the optical characteristic of the photographing optical system 31 when the focus lens 31b is located at the second position. The optical characteristic curve 200d represents that the exit pupil distance is Pod at an image height of zero, the exit pupil distance gradually increases as the image height H increases, and the exit pupil distance is (Pod+Δp4) at the maximum image height Hmax. 9(c), the optical characteristic curve 200c when the focus lens 31b is in the first position is shown as a negative optical characteristic curve, and the optical characteristic curve 200d when the focus lens 31b is in the second position is shown as a positive optical characteristic curve. However, there are also interchangeable lenses 3 having optical characteristics in which the optical characteristic curve 200c and the optical characteristic curve 200d are both positive or both negative.

[0076] The optical characteristic curve of the photographing optical system 31 of the interchangeable lens 3 shown in Fig. 9(d) differs, i.e., changes, depending on the focal length of the zoom lens (the position of the zoom lens 31a in Fig. 1). This photographing optical system 31 exhibits an optical characteristic curve 200e when the focal length is f1, and an optical characteristic curve 200f when the focal length is f2.

[0077] In Fig. 9(d), an optical characteristic curve 200e represents the optical characteristic of the photographing optical system 31 when the focal length is f1. The optical characteristic curve 200e indicates that the exit pupil distance is Poe at an image height of zero, and that as the image height H increases, the exit pupil distance gradually decreases, and that at the maximum image height Hmax, the exit pupil distance is (Poe-Δp5). The optical characteristic curve 200f represents the optical characteristic of the photographing optical system 31 when the focal length is f2. The optical characteristic curve 200f indicates that the exit pupil distance is Pof at an image height of zero, and that as the image height H increases, the exit pupil distance gradually increases, and that at the maximum image height Hmax, the exit pupil distance is (Pof+Δp6). 9(d), the optical characteristic curve 200e when the focal length is f1 is shown as a negative optical characteristic curve, and the optical characteristic curve 200f when the focal length is f2 is shown as a positive optical characteristic curve. However, there are also interchangeable lenses 3 having optical characteristics in which the optical characteristic curves 200e and 200f are both positive or both negative.

[0078] In the above description, the exit pupil distance Po at the image height H is the distance of the exit pupil of the photographing optical system 31 as viewed from the image height H of the imaging plane 22a. In other words, the exit pupil distance Po at the image height H is the distance of the exit pupil of the photographing optical system 31 (the distance from the imaging plane 22a) through which the light flux that has passed through the photographing optical system 31 and is incident on the position of the image height H on the imaging plane 22a passes. Fig. 10 shows the relationship between the image height H and the exit pupil distance Po. In Fig. 10, a light beam that has passed through the exit pupil EPa (exit pupil distance Poa) of the photographing optical system 31 is incident on a focus detection pixel (in Fig. 10, a microlens 44 is shown as a representative of the focus detection pixel) located at the center position 0 (image height zero) of the imaging surface 22a. The exit pupil distance Poa of this exit pupil EPa is the exit pupil distance of the exit pupil EPa for the image height zero. Furthermore, a light beam that has passed through an exit pupil EPb of the photographing optical system 31 is incident on a focus detection pixel (in FIG. 10, a microlens 44 is illustrated as a representative focus detection pixel) located at image height He. The exit pupil distance (Poa-Δp) of this exit pupil EPb is the exit pupil distance of the exit pupil EPb relative to the image height H.

[0079] Here, the relationship between the optical characteristics of each interchangeable lens 3 and the above formula (1) will be described. Po(H)=h4×H in the above formula (1) 4 +h2×H 2 +Co is a function that approximates the optical characteristic curves 200a, 200b, 200c, 200d, 200e, 200f, etc., shown in Figures 9(a) to 9(d). The optical characteristic curve 200a in Figure 9(a) is approximated by the calculation of formula (1) by setting the constant term Co in formula (1) to the exit pupil distance Poa at the image height of zero in Figure 9(a) and setting the coefficients h4 and h2 to coefficients h4a and h2a according to the curve of the optical characteristic curve 200a. The interchangeable lens 3 having the optical characteristic in Figure 9(a) stores the constant term Poa and the coefficients h4a and h2a in the lens memory 33 as lens information, as described above. Similarly, the interchangeable lens 3 having the optical characteristics of FIG. 9(b) stores the constant term Pob and coefficients h4b and h2b that specify the calculation of equation (1) that approximates the optical characteristic curve 200b in the lens memory 33 as lens information.

[0080] 9(c) has optical characteristics in which the optical characteristic curve changes depending on the position of the focus lens 31b. The interchangeable lens 3 stores in the lens memory 33 the constant term Co and coefficients h4 and h2 of the calculation of formula (1) that approximates the optical characteristic curve for each position of the focus lens 31b. The range in which the focus lens 31b moves (between the infinity position and the close position) is divided into a number of sections Z1 to Zn, and one optical characteristic curve representing each section (range) is determined for each section Z1 to Zn. For example, the optical characteristic curve when the focus lens 31b is located at the center position of one section is set as the optical characteristic curve representing that section.

[0081] The optical characteristic curve representing the section Zk is defined as the optical characteristic curve Zk (k=1, 2...n). For the calculation of formula (1) that approximates the representative optical characteristic curve Z1 of the section Z1, the constant term Co and coefficients h4 and h2 are set to Poz1, h4z1, and h2z1. For the calculation of formula (1) that approximates the optical characteristic curve Z2 of the section Z2, the constant term Co and coefficients h4 and h2 are set to Poz2, h4z2, and h2z2, respectively. Similarly, for the calculation of formula (1) that approximates the optical characteristic curve Zn of the section Zn, the constant term Co and coefficients h4 and h2 are set to Pozn, h4zn, and h2zn, respectively. FIG. 11 shows the constant terms and coefficients of the calculation that approximates these sections and the optical characteristic curves representing those sections. The interchangeable lens 3 stores in the lens memory 33 as lens information the relationships between the intervals Z1 to Zn and the constant terms Poz1 to Pozn and the coefficients h4z1 to h4zn and h2z1 to h2zn shown in FIG.

[0082] The interchangeable lens 3 in Fig. 9(d) is a zoom lens, and has optical characteristics in which the optical characteristic curve changes depending on the focal length. The interchangeable lens 3 stores in the lens memory 33 the constant term Co and coefficients h4 and h2 of the calculation of formula (1) that approximates the optical characteristic curve for each focal length. The range between the maximum focal length and the minimum focal length of the zoom lens set by the zoom lens 31a in Fig. 1 is divided into a plurality of sections W1 to Wn, and one optical characteristic curve representing each section W1 to Wn is determined. For example, the optical characteristic curve at the intermediate focal length in one section is set as the optical characteristic curve representing that section.

[0083] The optical characteristic curve representing the section Wk is defined as the optical characteristic curve Wk (k=1, 2...n). For the calculation of equation (1) that approximates the optical characteristic curve W1 in the section W1, the constant term Co and coefficients h4 and h2 are set to Pow1, h4w1, and h2w1, respectively. For the calculation of equation (1) that approximates the optical characteristic curve W2 in the section W2, the constant term Co and coefficients h4 and h2 are set to Pow2, h4w2, and h2w2, respectively. Similarly, for the calculation of equation (1) that approximates the optical characteristic curve Wn in the section Wn, the constant term Co and coefficients h4 and h2 are set to Pown, h4wn, and h2wn, respectively. FIG. 12 shows the constant terms and coefficients of the calculation that approximates these sections and the optical characteristic curves representing those sections. The interchangeable lens 3 stores in the lens memory 33 as lens information the relationship between the intervals W1 to Wn and the constant terms Pow1 to Pown and the coefficients h4w1 to h4wn and h2w1 to h2wn shown in FIG.

[0084] 9(d) is a zoom lens having optical characteristics in which the optical characteristic curve changes depending on the focal length, another zoom lens has optical characteristics in which the optical characteristic curve changes depending on the focal length and also depending on the position of the focus lens 31b. That is, the optical characteristic curve of the other zoom lens changes depending on both the position (focal length) of the zoom lens 31a and the position of the focus lens 31b.

[0085] Next, the relationship between the optical characteristic curve showing the optical characteristics of the interchangeable lens 3 shown in FIG. 9 and the first to third exit pupil distance ranges R1 to R3 shown in FIG. 8 will be described. FIG. 13 shows the first and second thresholds Th1 and Th2 related to the exit pupil distance shown in FIG. 8, the first to third exit pupil distance ranges R1 to R3, and the optical characteristic curve exemplified in FIG. 9. In FIG. 13, the entire optical characteristic curve 200g, that is, the exit pupil distance from the image height zero to the maximum image height Hmax, is located within the second exit pupil distance range R2. When the interchangeable lens 3 having such an optical characteristic curve 200g is attached to the camera body 2, the selection unit 214 selects the second AF pixel pair regardless of the image height H of the focus detection area 100 set by the area setting unit 212.

[0086] In the optical characteristic curve 200h, the exit pupil distance from image height zero to image height Hf belongs to the second exit pupil distance range R2, but the exit pupil distance from image height Hf to the maximum image height Hmax belongs to the first exit pupil distance range R1. The selection unit 214 selects the second AF pixel pair when the area setting unit 212 sets the focus detection area 100 with an image height equal to or less than Hf, and selects the first AF pixel pair when the area setting unit 212 sets a focus detection area with an image height greater than the image height Hf.

[0087] In the optical characteristic curve 200i, the exit pupil distance from image height zero to image height Hg belongs to a third exit pupil distance range R3, but the exit pupil distance from image height Hg to the maximum image height Hmax belongs to a second exit pupil distance range R2. The selection unit 214 selects the third AF pixel pair when the area setting unit 212 sets the focus detection area 100 with an image height equal to or less than Hg, and selects the second AF pixel pair when the area setting unit 212 sets a focus detection area with an image height greater than the image height Hg.

[0088] As described above, when a plurality of focus detection areas 100 are set by the area setting unit 212, the selection unit 214 selects the same type of AF pixel pair in each selected focus detection area 100. In this case, the selection unit 214 selects the AF pixel pair based on the position of the focus detection area 100 that is the farthest from the optical axis OA1 of the photographing optical system 31 (has the highest image height H) among the selected plurality of focus detection areas 100. In this embodiment, the selection unit 214 selects the AF pixel pair as described above based on the image height of the focus detection area 100 with the highest image height among the selected plurality of focus detection areas 100. The selection unit 214 selects the same type of AF pixel pair in the other focus detection areas 100 as the AF pixel pair selected in the focus detection area 100 with the highest image height among the selected plurality of focus detection areas 100.

[0089] 14 to 16 are flow charts showing an example of the operation of the camera 1 of this embodiment. Fig. 14 shows the operation when an interchangeable lens 3 having a type in which the photographing optical system 31 has a single optical characteristic curve as shown in Fig. 9(a) or (b) is attached to the camera body 2. In the following explanation, a case will be described in which an interchangeable lens 3 having a single optical characteristic curve 200a shown in Fig. 9(a) is attached to the camera body 2.

[0090] In FIG. 14, in step S100, when the camera body 2 is powered on, for example, it transmits a signal requesting transmission of lens information to the interchangeable lens 3. In step S200, the interchangeable lens 3 receives the request signal for lens information from the camera body 2. In step S201, the interchangeable lens 3 transmits lens information stored in the lens memory 33 (or the internal memory of the lens control unit 32) to the camera body 2. This lens information includes the above-mentioned constant term Poa and coefficients h4a and h2a of the calculation that approximates the optical characteristic curve 200a. In step S101, the camera body 2 receives the lens information from the interchangeable lens 3 and stores the lens information in the internal memory of the body control unit 210. It should be noted that the lens information may be stored in the body memory 23.

[0091] In step S102, for example, when the user operates the operation unit 25 to set the autofocus (AF) mode, the area setting unit 212 of the camera body 2 sets the focus detection area 100 of a predetermined image height Hx as an area for focus detection. In step S103, the distance calculation unit 213 of the camera body 2 substitutes the image height Hx of the set focus detection area 100 into equation (1) determined by the constant term Poa of the lens information and the coefficients h4a and h2a, to calculate the exit pupil distance Pox for the image height Hx.

[0092] In step S104, the distance calculation unit 213 of the camera body 2 determines whether or not the calculated exit pupil distance Pox belongs to the first exit pupil distance range R1. If the result of this determination is YES, the process proceeds to step S105, where the selection unit 214 selects the first AF pixel pair. If the result of the determination in step S104 is NO, the process proceeds to step S106, where the distance calculation unit 213 determines whether or not the calculated exit pupil distance Pox belongs to the second exit pupil distance range R2. If the result of this determination is YES, the process proceeds to step S107, where the selection unit 214 selects the second AF pixel pair. If the determination result in step S106 is NO, the exit pupil distance Pox belongs to the third exit pupil distance range R3, so the process proceeds to step S108, where the selection unit 214 selects the third AF pixel pair.

[0093] In step S109, the focus detection unit 215 of the camera body 2 calculates the amount of image shift by performing a correlation operation on the first and second signals Sig1, Sig2 of the first and second focus detection pixels of the AF pixel pair selected in step S105, S107, or S108. The focus detection unit 215 converts the calculated amount of image shift into a defocus amount, and calculates the amount of movement of the focus lens 31b based on this defocus amount.

[0094] In step S110, the camera body 2 transmits a signal related to the calculated movement amount of the focus lens 31b to the interchangeable lens 3. In step S202, the interchangeable lens 3 receives a signal related to the movement amount of the focus lens 31b from the camera body 2. In step S203, the interchangeable lens 3 moves the focus lens 31b based on the movement amount of the focus lens 31b to perform a focus adjustment operation.

[0095] In step S111, the camera body 2 determines whether or not a release operation has been performed by the operation unit 25. The camera body 2 repeats the series of operations from step S102 to step S110 until a release operation is performed.

[0096] Fig. 15 shows the operation when an interchangeable lens 3 whose optical characteristic curve changes depending on the focus lens position is attached to a camera body 2. In the following explanation, a case will be described in which an interchangeable lens 3 whose optical characteristic curve changes depending on the focus lens position shown in Fig. 9(c) is attached to a camera body 2.

[0097] In FIG. 15, in step S300, when the camera body 2 is powered on, for example, the camera body 2 transmits a signal to the interchangeable lens 3 requesting transmission of lens information. In step S400, the interchangeable lens 3 receives a request signal for lens information from the camera body 2. In step S401, the interchangeable lens 3 transmits the lens information stored in the lens memory 33 or the like to the camera body 2. This lens information includes the intervals Z1 to Zn shown in FIG. 11, and the constant terms Poz1 to Pozn and coefficients h4z1 to h4zn and h2z1 to h2zn for each interval. Furthermore, the lens information also includes position information of the focus lens 31b at the time of transmission. This position information of the focus lens 31b is repeatedly transmitted to the camera body 2 periodically or whenever the position of the focus lens 31b changes. In step S301, the camera body 2 receives the lens information from the interchangeable lens 3 and stores the lens information in an internal memory or the like of the body control unit 210.

[0098] In step S302, when the AF mode is set, the area setting unit 212 of the camera body 2 sets the focus detection area 100 of a predetermined image height Hx as an area for performing focus detection. In step S303A, the distance calculation unit 213 judges to which of the sections Z1 to Zn the position of the focus lens 31b represented by the latest transmitted position information belongs. In step S303B, the image height Hx of the set focus detection area 100 is substituted into equation (1) determined by the constant term Poz and coefficients h4z and h2z related to the determined section, to calculate the exit pupil distance Pox for the image height Hx. If the determined section is Z1, the image height Hx is substituted into equation (1) determined by the constant term Poz1 and coefficients h4z1 and h2z1, to calculate the exit pupil distance Pox for that image height Hx.

[0099] In step S304, the distance calculation unit 213 determines whether or not the calculated exit pupil distance Pox belongs to the first exit pupil distance range R1. If the result of this determination is YES, the process proceeds to step S305, where the selection unit 214 selects the first AF pixel pair. If the result of the determination in step S304 is NO, the process proceeds to step S306, where the distance calculation unit 213 determines whether or not the calculated exit pupil distance Pox belongs to the second exit pupil distance range R2. If the result of this determination is YES, the process proceeds to step S307, where the selection unit 214 selects the second AF pixel pair. If the determination result in step S306 is NO, the exit pupil distance Pox belongs to the third exit pupil distance range R3, so the process proceeds to step S308, where the selection unit 214 selects the third AF pixel pair.

[0100] In step S309, the focus detection unit 215 calculates the amount of image shift by performing a correlation operation on the first and second signals Sig1, Sig2 of the AF pixel pair selected in step S305, S307, or S308. The focus detection unit 215 converts the calculated amount of image shift into a defocus amount, and calculates the amount of movement of the focus lens 31b based on the defocus amount. In step S310, the camera body 2 transmits a signal related to the calculated amount of movement of the focus lens 31b to the interchangeable lens 3. In step S402, the interchangeable lens 3 receives a signal related to the amount of movement of the focus lens 31b from the camera body 2. In step S403, the interchangeable lens 3 moves the focus lens 31b based on the amount of movement of the focus lens 31b to perform a focus adjustment operation. In step S311, the camera body 2 determines whether or not a release operation has been performed by the operation unit 25. The camera body 2 repeats the series of operations from step S302 to step S310 until a release operation is performed.

[0101] FIG. 16 shows the operation when the interchangeable lens 3 is a zoom lens and the optical characteristics of the photographing optical system 31 change according to the focal length as shown in FIG. 9(d). In FIG. 16, in step S500, when the camera body 2 is turned on, for example, the camera body 2 transmits a signal to the interchangeable lens 3 requesting transmission of lens information. In step S600, the interchangeable lens 3 receives a request signal for lens information from the camera body 2. In step S601, the interchangeable lens 3 transmits the lens information stored in the lens memory 33 or the like to the camera body 2. This lens information includes the intervals W1 to Wn shown in FIG. 12, and the constant terms Pow1 to Pown and coefficients h4w1 to h4wn and h2w1 to h2wn for each interval. Furthermore, the lens information also includes information on the focal length of the photographing optical system 31 at the time of transmission (i.e., position information of the zoom lens 31a). This focal length information is repeatedly transmitted to the camera body 2 periodically or each time the position of the zoom lens 31a changes. In step S501, the camera body 2 receives the lens information from the interchangeable lens 3 and stores the lens information in an internal memory or the like of the body control unit 210.

[0102] In step S502, when the AF mode is set, the area setting unit 212 sets the focus detection area 100 of a predetermined image height Hx as an area for performing focus detection. In step S503A, the distance calculation unit 213 determines which of the sections W1 to Wn the focal length of the photographing optical system 31 belongs to, based on the latest position information transmitted. In step S503B, the image height Hx of the set focus detection area 100 is substituted into equation (1) determined by the constant term Pow and coefficients h4w and h2w related to the determined section, to calculate the exit pupil distance Pox for the image height Hx. If the determined section is W1, the image height Hx is substituted into equation (1) determined by the constant term Pow1 and coefficients h4w1 and h2w1, to calculate the exit pupil distance Pox for the image height Hx.

[0103] In step S504, the distance calculation unit 213 determines whether or not the calculated exit pupil distance Pox belongs to the first exit pupil distance range R1. If the result of this determination is YES, the process proceeds to step S505, where the selection unit 214 selects the first AF pixel pair. If the result of the determination in step S504 is NO, the process proceeds to step S506, where the distance calculation unit 213 determines whether or not the calculated exit pupil distance Pox belongs to the second exit pupil distance range R2. If the result of this determination is YES, the process proceeds to step S507, where the selection unit 214 selects the second AF pixel pair. If the determination result in step S506 is NO, the exit pupil distance Pox belongs to the third exit pupil distance range R3, so the process proceeds to step S508, where the selection unit 214 selects the third AF pixel pair.

[0104] In step S509, the focus detection unit 215 calculates the amount of image shift by performing a correlation operation on the first and second signals Sig1, Sig2 of the AF pixel pair selected in step S505, S507, or S508. The focus detection unit 215 converts the calculated amount of image shift into a defocus amount, and calculates the amount of movement of the focus lens 31b based on the defocus amount. In step S510, the camera body 2 transmits a signal related to the calculated amount of movement of the focus lens 31b to the interchangeable lens 3. In step S602, the interchangeable lens 3 receives a signal related to the amount of movement of the focus lens 31b from the camera body 2. In step S603, the interchangeable lens 3 moves the focus lens 31b based on the amount of movement of the focus lens 31b to perform a focus adjustment operation. In step S511, the camera body 2 determines whether or not a release operation has been performed by the operation unit 25. The camera body 2 repeats the series of operations from step S502 to step S510 until a release operation is performed.

[0105] 14, 15, and 16, the AF modes described include a first AF mode in which the user can select any focus detection area 100, and a second AF mode in which the camera 1 automatically selects the focus detection area 100. The first AF mode and the second AF mode each include a mode in which one focus detection area 100 is selected, and a mode in which multiple focus detection areas 100 are selected. The area setting unit 212 sets the focus detection area 100 selected by the user or the camera 1 as the area in which focus detection is performed.

[0106] According to the above-described embodiment, the following advantageous effects can be obtained. (1) The focus detection device includes an imaging section (image sensor 22) having a first pixel and a second pixel that receive light transmitted through the optical system and output a signal used for focus detection, an input section (body control section 210) to which first information related to a position on the image plane and an exit pupil distance of the optical system is input, a selection section 214 that selects first focus detection based on a signal output from the first pixel or second focus detection based on a signal output from the second pixel based on the first information input to the input section, and a focus detection section 215 that performs first focus detection or second focus detection based on the selection by the selection section. In this embodiment, information related to the exit pupil distance (h4, h2, Co) is input from the interchangeable lens 3 to the body control section 210. The body control section 210 calculates the exit pupil distance of the photographing optical system 31 at the image height of the focus detection area 100, and selects an AF pixel pair based on the calculated exit pupil distance. Furthermore, the body control unit 210 selects an AF pixel pair to be used for focus detection by the photographing optical system 31 having different optical characteristics. That is, the camera 1 selects an AF pixel pair to be used for focus detection depending on the exit pupil distance that changes with one interchangeable lens 3, or depending on the exit pupil distance that changes as the interchangeable lens 3 is changed. This allows the camera 1 to perform highly accurate focus detection even if the exit pupil distance changes. As a result, it is possible to suppress a decrease in focus detection accuracy.

[0107] (2) The imaging device is an imaging device equipped with a focus detection device, and includes an attachment / detachment section (body side mount section 201, body side connection section 202) to which an interchangeable lens 3 having an optical system can be attached / detached, and the input section receives first information from the interchangeable lens 3 attached to the attachment / detachment section. In this embodiment, information regarding the exit pupil distance is input to the body control section 210 from the interchangeable lens 3 via the body side connection section 202. For this reason, the body control section 210 can select an AF pixel pair to be used for focus detection based on the information regarding the exit pupil distance, and can perform highly accurate focus detection even if the exit pupil distance changes.

[0108] (3) The interchangeable lens 3 is an interchangeable lens that is detachable from a camera having an imaging unit, and includes an optical system in which the exit pupil distance changes depending on the position of the imaging unit on the image plane, and an output unit (lens control unit 32) that outputs first information relating to the position on the image plane and the exit pupil distance to the camera. In this embodiment, the lens control unit 32 of the interchangeable lens 3 outputs information relating to the exit pupil distance of the photographing optical system 31 to the camera body 2. This allows the camera body 2 to select an AF pixel pair to be used for focus detection based on the information relating to the exit pupil distance, enabling highly accurate focus detection even if the exit pupil distance changes.

[0109] (Variation 1) Fig. 17(a) shows the first and second focus detection pixels of the AF pixel pair extracted from the pixels of the image sensor 22 shown in Fig. 3. Figs. 17(b) and (c) show modified focus detection pixels. Note that in the example shown in Fig. 3, the photoelectric conversion unit 42, the light shielding unit 43L, and the light shielding unit 43R are each illustrated as having a rectangular shape, but they may be circular or have another shape. In Figs. 17(a) to (c), the photoelectric conversion unit 42, the light shielding unit 43L, and the light shielding unit 43R are each illustrated as having an approximately circular shape.

[0110] In FIG. 17(a), the first focus detection pixel 11 (microlens 44 and light shielding portion 43L) and the second focus detection pixel 12 (microlens 44 and light shielding portion 43R) constituting the AF pixel pair are arranged in different rows. On the other hand, the first focus detection pixel 11 (microlens 44 and light shielding portion 43L) and the second focus detection pixel 12 (microlens 44 and light shielding portion 43R) constituting the AF pixel pair of the modified example shown in FIG. 17(b) are arranged alternately in the same row. In FIGS. 17(a) and 17(b), the first focus detection pixel 11 outputs a first signal Sig1, and the second focus detection pixel 12 outputs a second signal Sig2. Note that an imaging pixel 13 may be arranged between the first focus detection pixel 11 and the second focus detection pixel 12.

[0111] In the first embodiment, an example in which one photoelectric conversion unit is arranged per pixel has been described, but the pixel may have two or more photoelectric conversion units per pixel. In the modified example shown in FIG. 17(c), each of the focus detection pixels has a microlens 44 and a first photoelectric conversion unit 42a and a second photoelectric conversion unit 42b that photoelectrically convert light transmitted through the microlens 44. That is, the focus detection pixel has a microlens 44 on which the first and second light beams that have passed through the first and second pupil regions of the exit pupil of the photographing optical system 31, respectively, are incident, and a first and second photoelectric conversion unit 42a, 42b that receive the first and second light beams that have passed through the microlens 44, respectively. The first photoelectric conversion unit 42a outputs a first signal Sig1, and the second photoelectric conversion unit 42b outputs a second signal Sig2.

[0112] The first photoelectric conversion unit 42a and the second photoelectric conversion unit 42b have different light receiving areas for receiving light. Just as the areas of the light-shielding unit 43L of the first focus detection pixel 11 and the light-shielding unit 43R of the second focus detection pixel 12 change depending on the image height, the light receiving areas of the first photoelectric conversion unit 42a and the second photoelectric conversion unit 42b change depending on the image height. Also, just as the areas of the light-shielding units 43 differ depending on the types of AF pixel pairs (first, second, and third AF pixel pairs) described above, the light receiving areas of the first photoelectric conversion unit 42a and the second photoelectric conversion unit 42b differ depending on the AF pixel pairs.

[0113] (Variation 2) In the first embodiment, three reference exit pupils (first to third exit pupils EP1 to EP3) are used as the reference exit pupils, but two reference exit pupils or four or more reference exit pupils may be used.

[0114] (Variation 3) In the flowchart shown in FIG. 15, in step S401, the intervals Z1 to Zn shown in FIG. 11 and the constant terms Poz1 to Pozn and coefficients h4z1 to h4zn, h2z1 to h2zn for each interval are all transmitted to the camera body 2. However, instead, the interchangeable lens 3 may transmit to the camera body 2 the constant term Poz and coefficients h4z, h2z related to the interval determined in step 303A of FIG. 15.

[0115] Similarly, in the flowchart shown in FIG. 16, in step S601, the intervals W1 to Wn shown in FIG. 12 and the constant terms Pow1 to Pown and coefficients h4w1 to h4wn, h2w1 to h2wn for each interval are all transmitted to the camera body 2, but instead, the interchangeable lens 3 may transmit to the camera body 2 the constant term Pow and coefficients h4w, h2w related to the interval determined in step 503A of FIG. 16.

[0116] (Variation 4) The method of calculating the exit pupil distance at a predetermined image height is not limited to the method using the above-mentioned formula (1). For example, instead of formula (1), an arithmetic expression using the cube of the image height may be used. Furthermore, information (table) showing the relationship between the image height and the exit pupil distance may be used without using an arithmetic expression.

[0117] (Variation 5) In the first embodiment, an example has been described in which information on the exit pupil distance is stored in advance in the lens memory 33 or the like, and the information on the exit pupil distance is input to the camera body 2 from the interchangeable lens 3. However, the information on the exit pupil distance may be input to the camera body 2 from a source other than the interchangeable lens 3. For example, the information on the exit pupil distance may be stored in advance in the body memory 23, and the body control unit 210 may acquire the information on the exit pupil distance from the body memory 23. In addition, the camera body 2 may acquire the information on the exit pupil distance from a storage medium, or may acquire the information on the exit pupil distance from an external device via wired communication or wireless communication. The information on the exit pupil distance may be information on the exit pupil distance corresponding to one image height.

[0118] (Variation 6) In the first embodiment, the parameters (h4), (h2) and the constant term Co used in calculating the exit pupil distance Po(H) have been given as examples of information related to the exit pupil distance. However, the camera body 2 may acquire the value Po(H) of the exit pupil distance at a predetermined image height itself from the interchangeable lens 3, a storage medium, etc. as information related to the exit pupil distance.

[0119] (Variation 7) In the first embodiment, an example has been described in which the selection unit 214 selects an AF pixel pair to be used for focus detection from among a plurality of types of AF pixel pairs arranged in the focus detection area 100 set by the area setting unit 212. However, the selection unit 214 may select the first and second signals Sig1, Sig2 to be used for focus detection. In this case, the image sensor 22 outputs the first and second signals Sig1, Sig2 of the first, second, and third AF pixel pairs to the body control unit 210. The selection unit 214 may select the first and second signals Sig1, Sig2 output from the AF pixel pair to be used for focus detection from among the first and second signals Sig1, Sig2 output from the first, second, and third AF pixel pairs.

[0120] The selection unit 214 may switch between selecting an AF pixel pair or selecting the first and second signals Sig1, Sig2 depending on the shooting mode (operation mode) of the camera body 2 (or camera 1). For example, when a through image (live view image) of a subject is displayed on the display unit 24 or when low-resolution video shooting is performed, the selection unit 214 may select an AF pixel pair to be used for focus detection. Also, when high-speed continuous shooting is performed or high-resolution video shooting is performed, the selection unit 214 may select the first and second signals Sig1, Sig2 output from the AF pixel pair to be used for focus detection.

[0121] (Second embodiment) Next, a camera according to a second embodiment will be described. In the camera according to the second embodiment, the focus detection unit 215 converts the image shift amount into a defocus amount, that is, the conversion formula is changed according to the image height. In the following description, the description of the same parts as those in the configuration and operation of the camera according to the first embodiment will be omitted, and the configuration and operation different from those in the camera according to the first embodiment will be mainly described.

[0122] 18 shows how exit pupil images 300a-300i and 300B-300I change depending on the image height on the imaging surface 22a of the image sensor 22. An exit pupil image is an image of the exit pupil of the photographing optical system 31 projected onto a photoelectric conversion unit by a microlens of a focus detection pixel. The shape of the exit pupil of the photographing optical system 31 changes depending on the shape of the opening of the diaphragm 31c.

[0123] 18 illustrates an exit pupil image 300a at an image height of zero (the center position of the imaging plane 22a), exit pupil images 300b-300i at a first image height H1, and exit pupil images 300B-300I at a second image height H2 that is larger than the first image height H1. The exit pupil images 300b-300i at the first image height H1 are distributed on concentric circles with the first image height H1 as a radius, and the exit pupil images 300B-300I at the second image height H2 are distributed on concentric circles with the second image height H2 as a radius.

[0124] When the x-coordinate and y-coordinate are defined with the center of the imaging surface 22a as the origin, the exit pupil images 300b and 300B are located on the x-axis, and the exit pupil images 300f and 300F are also located on the x-axis. The exit pupil images 300b and 300B and the exit pupil images 300f and 300F are point-symmetric with respect to the origin. The exit pupil images 300d and 300D are located on the y-axis, and the exit pupil images 300h and 300H are also located on the y-axis. The exit pupil images 300d and 300D and the exit pupil images 300h and 300H are point-symmetric with respect to the origin.

[0125] Exit pupil images 300c, 300C, 300g, and 300G are located on a radial line M1 tilted at 45° with respect to the x-axis, and exit pupil images 300c, 300C, 300g, and 300G are point-symmetric with respect to the origin. Exit pupil images 300e, 300E, 300i, and 300I are located on a radial line M2 tilted at 45° with respect to the y-axis, and exit pupil images 300e, 300E, 300i, and 300I are point-symmetric with respect to the origin.

[0126] The exit pupil image 300a at the image height of zero is an approximate circle obtained by reducing the approximate circle which is the shape of the opening of the diaphragm 31c, i.e., the shape of the exit pupil. The exit pupil images 300b-300i at the first image height H1 located on a concentric circle have the same approximate elliptical shape, and the exit pupil images 300B-300I at the second image height H2 located on a concentric circle also have the same approximate elliptical shape. The approximate elliptical shape of the exit pupil images 300b-300i at the first image height H1 has a major axis length, i.e., a major axis MA1, and a minor axis length, i.e., a minor axis MI1, which are each smaller than the diameter D0 of the approximate circle of the exit pupil image 300a at the image height of zero. The approximately elliptical shape of the exit pupil images 300B-300I at the second image height H2 has a major axis MA2 smaller than the major axis MA1 of the exit pupil images 300b-300i at the first image height H1, and a minor axis MI2 smaller than the minor axis MI1 of the exit pupil images 300b-300i at the first image height H1.

[0127] The direction of the major axis MA of the ellipse of each exit pupil image is perpendicular to the radiation direction. That is, the major axis of the exit pupil images 300b, 300B, 300f, and 300F on the x-axis is perpendicular to the x-axis, and the major axis of the exit pupil images 300d, 300D, 300h, and 300H on the y-axis is perpendicular to the y-axis. The major axes of the exit pupil images 300c, 300C, 300g, and 300G on the radiation M1 are perpendicular to the radiation M1, and the major axes of the exit pupil images 300e, 300E, 300i, and 300I on the radiation M2 are perpendicular to the radiation M2.

[0128] As described above, the exit pupil image is approximately circular at an image height of zero, but becomes approximately elliptical as the image height H increases. The major axis MA and minor axis MI of this approximately elliptical shape gradually become smaller as the image height H increases. The shape and size of the exit pupil image change depending on the image height H. In addition, the shape and size of the exit pupil image change depending on the optical characteristics of the photographic optical system 31, and therefore also differ depending on the type of interchangeable lens 3.

[0129] Next, the relationship between the photoelectric conversion unit of the focus detection pixel and the exit pupil image projected by the microlens onto this photoelectric conversion unit will be described. Fig. 19 shows the relationship between the pair of photoelectric conversion units 42a, 42b and the exit pupil image 300, using the focus detection pixel shown in Fig. 17(c) as an example. In the illustrated example, the pair of photoelectric conversion units 42a, 42b each have a semicircular shape obtained by dividing a circle with a diameter D0 into two equal parts.

[0130] 19A shows the relationship between the photoelectric conversion units 42a, 42b of the focus detection pixel and an exit pupil image 300a at an image height of zero. The approximately circular exit pupil image 300a has a diameter D0 and therefore entirely covers the pair of photoelectric conversion units 42a, 42b.

[0131] FIG. 19B shows the relationship between an exit pupil image 300b at a first image height H1 and the photoelectric conversion units 42a, 42b of the focus detection pixel at that position. The exit pupil image 300b has a vertically elongated, approximately elliptical shape, and its major axis MA1 is smaller than the diameter D0. The direction of the minor axis MI1 of the exit pupil image 300b coincides with the arrangement direction of the pair of photoelectric conversion units 42a, 42b (the x-axis direction in FIG. 18), and this minor axis MI1 is smaller than the diameter D0. The relationship between an exit pupil image 300f at a position point-symmetrical to the exit pupil image 300b with respect to the origin and the photoelectric conversion units 42a, 42b of the focus detection pixel at that position is also the same as that shown in FIG. 19B.

[0132] 19(c) shows the relationship between the exit pupil image 300B at the second image height H2 and the photoelectric conversion units 42a, 42b of the focus detection pixel at that position. The exit pupil image 300B has a vertically elongated, generally elliptical shape smaller than the exit pupil image 300b, and its major axis MA2 and minor axis MI2 are smaller than the major axis MA1 and minor axis MI1 of the exit pupil image 300b, respectively. The relationship between the exit pupil image 300F at a position point-symmetrical to the exit pupil image 300B with respect to the origin and the photoelectric conversion units 42a, 42b of the focus detection pixel at that position is also the same as that shown in FIG. 19(c).

[0133] FIG. 19(d) shows the relationship between an exit pupil image 300d at a first image height H1 and the photoelectric conversion units 42a, 42b of the focus detection pixel at that position. The exit pupil image 300d has a horizontally long, approximately elliptical shape. The direction of the major axis MA1 of the exit pupil image 300d coincides with the arrangement direction of the pair of photoelectric conversion units 42a, 42b, and this major axis MA1 is smaller than the diameter D0. The relationship between an exit pupil image 300h at a position point-symmetrical to the exit pupil image 300d with respect to the origin and the photoelectric conversion units 42a, 42b of the focus detection pixel at that position is also the same as that shown in FIG. 19(d).

[0134] Fig. 19(e) shows the relationship between the exit pupil image 300D at the second image height H2 and the photoelectric conversion units 42a, 42b of the focus detection pixel at that position. The exit pupil image 300D has a horizontally elongated, approximately elliptical shape smaller than the exit pupil image 300d, and its major axis MA2 and minor axis MI2 are smaller than the major axis MA1 and minor axis MI1 of the exit pupil image 300d, respectively. The relationship between the exit pupil image 300H at a position point-symmetrical to the exit pupil image 300D with respect to the origin and the photoelectric conversion units 42a, 42b of the focus detection pixel at that position is also the same as that shown in Fig. 19(e).

[0135] 19(f) shows the relationship between each of the exit pupil images 300c, 300g, 300e, and 300i at the first image height H1 on the radiation M1 and M2 and the photoelectric conversion units 42a and 42b of the focus detection pixels at those positions. The directions of the major axes MA and minor axes MI of the exit pupil images 300c, 300g, 300e, and 300i are inclined with respect to the arrangement direction of the pair of photoelectric conversion units 42a and 42b.

[0136] 19(g) shows the relationship between each of the exit pupil images 300C, 300G, 300E, and 300I at the second image height H2 on the radiation M1 and M2 and the photoelectric conversion units 42a and 42b of the focus detection pixels at those positions. The directions of the major axes MA and minor axes MI of the exit pupil images 300C, 300G, 300E, and 300I are also tilted with respect to the arrangement direction of the pair of photoelectric conversion units 42a, 42b.

[0137] In the first embodiment, it has been explained that the focus detection unit 215 converts the image shift amount into a defocus amount, but the conversion of this image shift amount into a defocus amount will be explained below. The conversion formula for converting the image shift amount Δ into the defocus amount Def can be expressed as follows using a conversion coefficient K1. Def = K1 × Δ … (2) The conversion coefficient K1 depends on the distance between the center of gravity of the overlapping region between the exit pupil images 300a-300I and the photoelectric conversion unit 42a and the center of gravity of the overlapping region between the exit pupil images 300a-300I and the photoelectric conversion unit 42b. The conversion coefficient K1 is proportional to the reciprocal of the distance between the centers of gravity.

[0138] 19(a) illustrates an example of a center-of-gravity distance G between a center-of-gravity position g1 of an overlapping region between the exit pupil image 300a and the photoelectric conversion unit 42a and a center-of-gravity position g2 of an overlapping region between the exit pupil image 300a and the photoelectric conversion unit 42b. The overlapping region between the exit pupil image and the photoelectric conversion unit 42a is a region where a light beam that has passed through a first pupil region of the exit pupil of the photographing optical system 31 enters the photoelectric conversion unit 42a. Similarly, the overlapping region between the exit pupil image and the photoelectric conversion unit 42b is a region where a light beam that has passed through a second pupil region of the exit pupil of the photographing optical system 31 enters the photoelectric conversion unit 42b.

[0139] Since the center-of-gravity spacing of the focus detection pixels of the exit pupil image 300b at the first image height H1 shown in Figure 19(b) is smaller than the center-of-gravity spacing for the focus detection pixels of the exit pupil image 300a at the image height of zero in Figure 19(a), the conversion coefficient K1 of the focus detection pixels in Figure 19(b) is larger than the conversion coefficient K1 in Figure 19(a). In addition, since the center-of-gravity interval for the focus detection pixels of the exit pupil image 300B at the second image height H2 shown in Figure 19(c) is smaller than the center-of-gravity interval for the focus detection pixels of the exit pupil image 300b at the first image height H1 in Figure 19(b), the conversion coefficient K1 of the focus detection pixels in Figure 19(c) is larger than the conversion coefficient in Figure 19(b).

[0140] The focus detection pixels of the exit pupil image 300d at the first image height H1 shown in Figure 19(d) have a center-of-gravity interval that is smaller than the center-of-gravity interval for the focus detection pixels of the exit pupil image 300a at the image height of zero in Figure 19(a), so the conversion coefficient K1 of the focus detection pixels in Figure 19(d) is larger than the conversion coefficient K1 in Figure 19(a). In addition, since the center-of-gravity interval for the focus detection pixels of the exit pupil image 300D at the second image height H2 shown in Figure 19(e) is smaller than the center-of-gravity interval for the focus detection pixels of the exit pupil image 300d at the first image height H1 in Figure 19(d), the conversion coefficient K1 of the focus detection pixels in Figure 19(e) is larger than the conversion coefficient K1 in Figure 19(d).

[0141] The center-of-gravity interval of each of focus detection pixels of exit pupil images 300c, 300g, 300e, and 300i at first image height H1 shown in Fig. 19(f) is an intermediate value between the center-of-gravity interval for the focus detection pixels of Fig. 19(b) and the center-of-gravity interval for the focus detection pixels of Fig. 19(d). The conversion coefficient K1 of the focus detection pixel of Fig. 19(f) is an intermediate value between the conversion coefficient K1 of the focus detection pixel of Fig. 19(b) and the conversion coefficient K1 of the focus detection pixel of Fig. 19(d).

[0142] Similarly, the center-of-gravity interval of each focus detection pixel of the exit pupil images 300C, 300G, 300E, and 300I at the second image height H2 shown in Fig. 19(g) is an intermediate value between the center-of-gravity interval of the focus detection pixel of Fig. 19(c) and the center-of-gravity interval of the focus detection pixel of Fig. 19(e). The conversion coefficient K1 of the focus detection pixel of Fig. 19(g) is an intermediate value between the conversion coefficient K1 of the focus detection pixel of Fig. 19(c) and the conversion coefficient K1 of the focus detection pixel of Fig. 19(e). Note that, as in Figs. 19(f) and (g), when the major axis and the minor axis of the exit pupil image are inclined with respect to the arrangement direction of the photoelectric conversion units 42a and 42b, the center-of-gravity interval is the interval in the arrangement direction of the photoelectric conversion units 42a and 42b.

[0143] Next, a configuration example of the focus detection unit 215 of the camera body 2 of the second embodiment will be described. In FIG. 20, a plurality of functions executed by the focus detection unit 215 are shown as blocks for each function. In FIG. 20, the focus detection unit 215 has a correlation calculation unit 215A, a defocus amount calculation unit 215B, a lens movement amount calculation unit 215C, an exit pupil image calculation unit 215D, and a conversion coefficient calculation unit 215E. In addition, the area setting unit 212 sets one focus detection area 100 from the plurality of focus detection areas 100, and outputs the image height H of the set focus detection area 100 and the coordinates (x, y) of the focus detection area. As described above, the area setting unit 212 outputs the image height at the center of the set focus detection area 100 as the image height H of the set focus detection area 100, and outputs the coordinates of the center of the focus detection area 100 as the coordinates (x, y) of the focus detection area.

[0144] The correlation calculation unit 215A of the focus detection unit 215 receives the first and second signals Sig1 and Sig2, and performs correlation calculation between the first and second signals Sig1 and Sig2 to calculate the phase difference between the first and second signals Sig1 and Sig2, that is, the image shift amount Δ. The defocus amount calculation unit 215B converts the image shift amount Δ into a defocus amount Def using the conversion formula shown in Equation (2), that is, multiplies the image shift amount Δ by a conversion coefficient K1 according to the exit pupil image to calculate the defocus amount Def. The lens movement amount calculation unit 215C calculates the movement amount of the focus lens 31b based on the defocus amount Def calculated by the defocus amount calculation unit 215B. The lens control unit 32 of the interchangeable lens 3 moves the focus lens 31b based on the calculated movement amount of the focus lens 31b to perform focus adjustment.

[0145] The exit pupil image calculation unit 215D receives as input the image height H of the focus detection area 100 set by the area setting unit 212, the F-number (aperture value) Fo of the diaphragm 31c transmitted from the interchangeable lens 3, and coefficients K2 and K3 (described later) transmitted from the interchangeable lens 3. The exit pupil image calculation unit 215D has the following calculation formulas (3) and (4) which express the exit pupil images on the concentric circle of the image height H with the image height H as a variable, stored in advance in an internal memory or the like. FoT = (1 + K2 × H 2 ) × Fo … (3) FoR = (1 + K3 × H 2 ) × Fo … (4) In the formulas (3) and (4), Fo is, for example, the maximum aperture (F value) of the aperture 31c of the photographing optical system 31. 2 The coefficients K2 and K3 are values ​​determined by the optical characteristics of the photographing optical system 31. These coefficients K2 and K3 are stored in the lens memory 33 or the like of the interchangeable lens 3, and are transmitted to the camera body 2. In this way, the camera body 2 acquires information on the coefficients K2 and K3 based on the shape of the exit pupil in the fully opened aperture state, for example, from the interchangeable lens 3. Note that the camera body 2 may also acquire information on the coefficients K2 and K3 based on the shape of the exit pupil in the state where the aperture 31c is stopped down by one step, from the interchangeable lens 3.

[0146] FoT in formula (3) is the size of the exit pupil image in the radial direction from the center of the imaging surface 22a (the optical axis of the photographing optical system 31), that is, the minor axis MI of the approximately elliptical exit pupil image, expressed by using the F-number Fo of the aperture 31c of the photographing optical system 31. Similarly, FoR in formula (4) is the size of the exit pupil image in the circumferential direction of the concentric circle of the image height H, that is, the major axis MA of the approximately elliptical exit pupil image, expressed by using the F-number Fo of the aperture 31c of the photographing optical system 31. As described above, since the exit pupil image 300 is a projected image of the exit pupil of the photographing optical system 31, the shape of this exit pupil image is expressed by using the F-number of the aperture 31c. Note that the F-number Fo does not have to be the open F-number of the aperture 31c, but may be the F-number of an aperture narrower than the open F-number.

[0147] When H=0, which is the image height of zero, is substituted into equations (3) and (4), FoT, which represents the radial size of the exit pupil image, and FoR, which represents the circumferential size, both become Fo. This represents the shape of the exit pupil image 300a with an image height of zero shown in FIG. 18. Furthermore, equations (3) and (4) indicate that as the image height H increases, both the radial size FoT and the circumferential size FoR of the exit pupil image increase. Equations (3) and (4) indicate that as the image height H increases, the major axis MA and minor axis MI of the exit pupil image 300 decrease, as shown in FIG. 18.

[0148] 20 again, the conversion coefficient calculation unit 215E receives as input the image height H and coordinate values ​​(x, y) of the focus detection region 100 set by the region setting unit 212, and the radial size FoT and circumferential size FoR of the exit pupil image calculated by the exit pupil image calculation unit 215D. The conversion coefficient calculation unit 215E has, stored in advance in an internal memory or the like, the following equation (5) for calculating FL representing the length of the exit pupil image 300 in the arrangement direction of the pair of photoelectric conversion units 42a, 42b shown in FIG. 19 (the x-axis direction in FIG. 18), that is, the size in the x direction. FL = (FoT × x 2 +FoR×y 2 ) / (x 2 +y 2 ) …(5) Since this FL is expressed by the F-number Fo, as FL increases, the length of the exit pupil image 300 in the x direction decreases. In equation (5), for example, the size FL in the x direction of exit pupil image 300b shown in Fig. 18 becomes the size in the radial direction FoT when the coordinates (xb, 0) of exit pupil image 300b are substituted. Similarly, for example, the size FL in the x direction of exit pupil image 300d shown in Fig. 18 becomes the size in the radial direction FoR when the coordinates (0, yd) of exit pupil image 300d are substituted.

[0149] The conversion coefficient calculation unit 215E sends the calculated size FL of the exit pupil image 300 in the x direction as a conversion coefficient to the defocus amount calculation unit 215B. The defocus amount calculation unit 215B sets the conversion coefficient K1 in the formula (2) as K1=a×FL 2The image shift amount Δ is converted into the defocus amount Def using +b, where a and b are constants.

[0150] In the above explanation, the size FL of the exit pupil image 300 in the x direction is used as the conversion coefficient K1 instead of the center-of-gravity interval G explained using Fig. 19(a). This is because as the size FL of the exit pupil image 300 in the x direction increases, the center-of-gravity interval G decreases. In order to improve the accuracy of converting the image shift amount into the defocus amount, the centroid interval can be calculated from the size FL, and the defocus amount can be converted using the centroid interval.

[0151] Fig. 21 is a flowchart showing an example of an operation for converting the amount of image shift into a defocus amount in the focus detection unit 215 of the camera according to the second embodiment. Fig. 21 shows the operation when an interchangeable lens 3 having optical characteristics such that the photographing optical system 31 generates exit pupil images 300a-300i and 300B-300I as shown in Fig. 18 is attached to the camera body 2.

[0152] 21, in step S700, when the camera body 2 is powered on, for example, it transmits a signal requesting transmission of lens information to the interchangeable lens 3. In step S800, the interchangeable lens 3 receives the lens information request signal from the camera body 2. In step S801, the interchangeable lens 3 transmits lens information stored in the lens memory 33 or the like to the camera body 2. The lens information includes coefficients K2, K3, and the F-number Fo of the aperture 31c. The F-number Fo of the aperture 31c is, for example, the maximum F-number of the aperture 31c. In step S701, the camera body 2 receives the lens information from the interchangeable lens 3 and stores the lens information in an internal memory or the like of the body control unit 210.

[0153] In step S702, when the AF mode is set, the area setting unit 212 of the camera body 2 sets the focus detection area 100 of a predetermined image height H as an area for focus detection. The area setting unit 212 outputs the image height H and coordinates (x, y) of the set focus detection area 100 to the focus detection unit 215.

[0154] In step S703, the exit pupil image calculation unit 215D substitutes the image height H of the set focus detection area 100 into equations (3) and (4) determined by the lens information coefficients K2 and K3 and the F-number Fo to calculate FoT and FoR. The conversion coefficient calculation unit 215E substitutes the coordinate values ​​(x, y) of the focus detection area 100 set by the area setting unit 212 and the FoT and FoR calculated by the exit pupil image calculation unit 215D into equation (5) to calculate the size FL of the exit pupil image 300 in the arrangement direction of the pair of photoelectric conversion units 42a and 42b (the x-axis direction in FIG. 18). The conversion coefficient calculation unit 215E sends the calculated size FL of the exit pupil image 300 in the x-direction to the defocus amount calculation unit 215B as a conversion coefficient.

[0155] In step S704, the defocus amount calculation unit 215B sets the conversion coefficient K1 in the equation (2) as K1=a×FL 2 +b is used to convert the image shift amount Δ into the defocus amount Def. When the F-number of the aperture 31c during focus detection is changed or when the focus detection area is changed, the camera 1 repeats the series of operations of step S801 and steps S701 to S704.

[0156] In addition, when the interchangeable lens 3 has both the optical characteristics described in the first embodiment using FIG. 9 and the optical characteristics described in the second embodiment using FIG. 18, the operations described in the first and second embodiments are performed.

[0157] According to the above-described embodiment, the following advantageous effects can be obtained. (1) The input unit (body control unit 210) receives second information on the shape of the exit pupil of the optical system, and the focus detection unit 215 performs focus detection based on the second information and the signal output from the first pixel or the signal output from the second pixel. In this embodiment, the body control unit 210 receives information (K2, K3) on the shape of the exit pupil from the interchangeable lens 3. The body control unit 210 calculates the size of the exit pupil image at the image height of the focus detection area, and calculates the defocus amount by multiplying the image shift amount by a conversion coefficient according to the calculated exit pupil distance. The camera 1 changes the conversion coefficient used to calculate the defocus amount depending on the exit pupil image that changes with one interchangeable lens 3, or the exit pupil image that changes due to a change in the interchangeable lens 3. This allows the camera 1 to perform highly accurate focus detection even if the exit pupil image changes. As a result, it is possible to suppress a decrease in focus detection accuracy.

[0158] (Variation 8) In the second embodiment, the radial size of the exit pupil images 300a-300i, 300B-300I, i.e., the minor axis MI of the approximately elliptical exit pupil image, is expressed by equation (3) using the F-number of the aperture 31c. Similarly, the circumferential size of the exit pupil images 300a-300i, 300B-300I, i.e., the major axis MA of the approximately elliptical exit pupil image, is expressed by equation (4) using the F-number of the aperture 31c. Instead of the F-number of the aperture 31c, the minor axis MI and major axis MA of the exit pupil image may be expressed using the opening diameter of the aperture 31c.

[0159] (Variation 9) In the second embodiment, the exit pupil image calculation unit 215D calculates FoT and FoR using the image height H, the coefficients K2 and K3, and the F-value Fo, and the conversion coefficient calculation unit 215E calculates FL using FoT and FoR and the coordinates (x, y). In the modified example, the exit pupil image calculation unit 215D is omitted, and the conversion coefficient calculation unit 215E directly calculates FL using the coefficients K2 and K3, the F-value Fo, and the coordinates (x, y). This will be explained below.

[0160] Substituting the FoT in equation (3) and the FoR in equation (4) into the FoT and FoR in equation (5) above gives the following equation (6). FL = {(1 + K2 × H 2 )Fo×x 2 +(1+K3×H 2 )Fo×y 2} / (x 2 +y 2 )…(6) Between the image height H of the focus detection area 100 set by the area setting unit 212 and the coordinates (x, y) of the focus detection area, 2 =x 2 +y 2 This H 2 =x 2 +y 2 H in equation (6) 2 By substituting this, FL can be expressed by the following equation (7). FL = {(1 + K2(x 2 +y 2 ))Fo×x 2 +(1+K3(x 2 +y 2 ))Fo×y 2} / (x 2 +y 2 ) …(7)

[0161] A conversion coefficient calculation section 215E according to the modified example calculates FL based on equation (7) using the coefficients K2, K3 and the F-number Fo transmitted from the interchangeable lens 3 and the coordinate values ​​(x, y) from the region setting section 212.

[0162] The method of calculating FoT and FoR is not limited to the above-mentioned formulas (3) and (4). A calculation formula other than formulas (3) and (4) may be used. A table showing the relationship between image height and FoT and FoR may be used. The method of calculating FL is not limited to the above-mentioned formula (5) or (6). Other calculation formulas may be used. A table showing the relationship between the coordinates (x, y) and the F values ​​Fo and FL may be used.

[0163] The following modifications are also within the scope of the present invention, and one or more of the modifications may be combined with the above-described embodiment.

[0164] (Variation 10) In the above-described embodiment, an example has been described in which first to third AF pixel pairs having different amounts of deviation are arranged on the image sensor 22 as multiple types of AF pixel pairs. However, multiple types of AF pixel pairs having different positions of light-shielding parts between the color filter 51 and the photoelectric conversion unit 42 may be arranged on the image sensor 22. FIG. 22 is a diagram showing an example of the configuration of focus detection pixels of the image sensor 22 according to a modified example. In the figure, the same reference numbers are used for parts that are the same as or equivalent to those in the above-described embodiment.

[0165] The light-shielding portion 43L of the first focus detection pixel 11a is provided at a predetermined distance h1 from the photoelectric conversion unit 42 between the color filter 51 and the photoelectric conversion unit 42. The light-shielding portion 43L of the first focus detection pixel 11b is provided at a predetermined distance h2 from the photoelectric conversion unit 42 between the color filter 51 and the photoelectric conversion unit 42. The light-shielding portion 43L of the first focus detection pixel 11c is provided at a predetermined distance h3 from the photoelectric conversion unit 42 between the color filter 51 and the photoelectric conversion unit 42. The distance h2 is smaller than the distance h1 and larger than the distance h3. That is, h1>h2>h3. In this way, the first focus detection pixels 11a, 11b, and 11c have different positions of the light-shielding portion 43L. Furthermore, the other second focus detection pixel 12a, 12b, 12c constituting each AF pixel pair has a different light-shielding portion 43R disposed in a different position. This allows the first to third AF pixel pairs to perform pupil division in response to different angles of incidence, as in the above-described embodiment.

[0166] (Variation 11) FIG. 23 is a diagram showing an example of the configuration of focus detection pixels of the image sensor 22 according to a modified example. As an example, FIG. 23 shows a cross-sectional view of some three types of AF pixel pairs in the focus detection area 100c of FIG. 2. In the figure, the same reference numerals are used for the same or corresponding parts as those in the above-mentioned embodiment. Each of the three types of focus detection pixels shown in FIG. 23(a) to (c) has a microlens 44 and a first photoelectric conversion unit 42a and a second photoelectric conversion unit 42b that photoelectrically convert light transmitted through the microlens 44. In this modified example, the first to third AF pixel pairs have different light receiving areas for the first photoelectric conversion unit 42a and the second photoelectric conversion unit 42b that receive light. In this case, the first to third AF pixel pairs can perform pupil division in response to different incident angles, as in the case of the above-mentioned embodiment.

[0167] (Variation 12) The selection unit 214 may select a plurality of types of AF pixel pairs. In this case, the focus detection unit 215 may calculate a plurality of defocus amounts using the first and second signals output from the plurality of types of AF pixel pairs, and may calculate the movement amount of the focus lens 31b based on the average value of the defocus amounts. For example, the movement amount of the focus lens 31b may be determined based on the defocus amount calculated using the first and second signals Sig1, Sig2 of the first AF pixel pair and the average value of the defocus amount calculated using the first and second signals Sig1, Sig2 of the second AF pixel pair.

[0168] (Variation 13) In the above embodiment, a case has been described in which a primary color (RGB) color filter is used in the imaging element 22, but a complementary color (CMY) color filter may also be used.

[0169] (Variation 14) The imaging devices described in the above-mentioned embodiments and modifications may be applied to cameras, smartphones, tablets, cameras built into PCs, in-vehicle cameras, cameras mounted on unmanned aerial vehicles (drones, radio-controlled aircraft, etc.), and the like.

[0170] Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments that are conceivable within the scope of the technical idea of ​​the present invention are also included within the scope of the present invention.

[0171] The disclosures of the following priority applications are incorporated herein by reference: Japan Patent Application No. 2018-137262 (filed July 20, 2018) [Explanation of symbols]

[0172] 1...imaging device, 2...camera body, 3...interchangeable lens, 11...focus detection pixel, 12...focus detection pixel, 13...imaging pixel, 22...imaging element, 23...body memory, 31...photographic optical system, 31a...zoom lens, 31b...focus lens, 31c...aperture, 32...lens control unit, 33...lens memory, 42...photoelectric conversion unit, 44...microlens, 210...body control unit, 211...image data generation unit, 212...area setting unit, 213...distance calculation unit, 214...selection unit, 215...focus detection unit

Claims

1. a first pixel and a second pixel each having a photoelectric conversion unit that performs photoelectric conversion on light transmitted through an optical system to generate electric charges, the photoelectric conversion units having different widths for receiving light and therefore different areas for receiving light, and each outputting a signal used for focus detection based on the electric charges generated by the photoelectric conversion unit; an output unit that outputs a signal from the first pixel or the second pixel in response to selection of focus detection by the first pixel or focus detection by the second pixel based on first information related to a position on an image plane and an exit pupil distance of the optical system; An imaging element comprising:

2. 2. The imaging device according to claim 1, The output unit is an image sensor that outputs a signal from the first pixel or the second pixel depending on selection of focus detection by the first pixel or focus detection by the second pixel based on the first information when at least one of the focal length of the optical system and the shooting distance changes.

3. 3. The imaging device according to claim 1, The first information is information about an exit pupil distance that changes depending on a position on an image plane of an image sensor.

4. The imaging device according to any one of claims 1 to 3, The first information is information indicating a relationship between a position on an image plane and an exit pupil distance, or a coefficient of an equation for calculating the exit pupil distance.

5. The imaging device according to any one of claims 1 to 4, A plurality of the first pixels and a plurality of the second pixels, the plurality of first pixels include a pixel that receives light that has passed through a first pupil region of the optical system and a pixel that receives light that has passed through a second pupil region different from the first pupil region, An imaging element, wherein the second pixels include a pixel that receives light that has passed through the first pupil region and a pixel that receives light that has passed through the second pupil region.

6. The imaging device according to any one of claims 1 to 5, the first pixel and the second pixel each have a light shielding portion that shields light from being incident on the photoelectric conversion portion; An imaging element in which an area of ​​the light-shielding portion of the first pixel and an area of ​​the light-shielding portion of the second pixel are different from each other.

7. The imaging element according to any one of claims 1 to 6, a generation unit that generates image data based on a signal output from the imaging element.

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