Patent Publication Number: US-11641519-B2

Title: Focus detection device, imaging device, and interchangeable lens

Description:
TECHNICAL FIELD 
     The present invention relates to a focus detection device, an imaging device, and an interchangeable lens. 
     BACKGROUND ART 
     An image sensor that reads out a signal for focus detection and a signal for image generation is known (for example, Patent Literature 1: PTL1). In such an image sensor, it is desired to increase the speed of signal reading. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Laid-Open Patent Publication No. 2017-34606 
     SUMMARY OF INVENTION 
     According to the 1st aspect of the present invention, a focus detection device comprises: an imaging unit having a first pixel and a second pixel each of which receives light transmitted through an optical system and outputs signal used for focus detection, and a third pixel which receives light transmitted through the optical system and outputs signal used for image generation; an input unit to which information regarding the optical system is input; a selection unit that selects at least one of the first pixel and the second pixel based on the information input to the input unit; a readout unit that reads out the signal from at least one of the first pixel and the second pixel based on a selection result of the selection unit at a timing different from a timing of reading out the signal from the third pixel to be read out; and a focus detection unit that performs the focus detection based on at least one of the signals of the first pixel and the second pixel read out by the readout unit. 
     According to the 2nd aspect of the present invention, an imaging device comprises: the focus detection device according to the 1st aspect, and a generation unit that generates image data based on signals output from at least one of the first pixel, the second pixel, and the third pixel. 
     According to the 3rd aspect of the present invention, an interchangeable lens comprises: a detachable portion that enables to attach and detach to the focus detection device according to the 1st aspect. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a diagram showing a configuration example of an imaging device according to the first embodiment. 
         FIG.  2    is a diagram showing a focus detection area of an imaging surface of the imaging device according to the first embodiment. 
         FIG.  3    is a diagram showing an arrangement example of pixels in the focus detection area of the imaging device according to the first embodiment. 
         FIG.  4    is a diagram showing a s configuration example of pixels in the imaging device according to the first embodiment. 
         FIG.  5    is a cross-sectional view showing three types of AF pixel pairs to be arranged at the central region of the imaging device according to the first embodiment. 
         FIG.  6    is a cross-sectional view showing three types of AF pixel pairs to be arranged at a region corresponding to a predetermined image height in the imaging device according to the first embodiment. 
         FIG.  7    is a cross-sectional view showing three types of AF pixel pairs to be arranged at a region corresponding to a predetermined image height in the imaging device according to the first embodiment. 
         FIG.  8    is a diagram showing the relationship between the reference exit pupil and the image height in the imaging device according to the first embodiment. 
         FIG.  9    shows various optical characteristics of an interchangeable lens whose exit pupil distance changes according to the image height, in the imaging device according to the first embodiment. 
         FIG.  10    is a diagram showing the relationship between the image height and the exit pupil in the imaging device according to the first embodiment. 
         FIG.  11    is a table showing a constant term and coefficients of a function that approximates representative optical characteristic curve in each focus position zone in the imaging device according to the first embodiment. 
         FIG.  12    is a table showing a constant term and coefficients of a function that approximates representative optical characteristic curve in each zone in the imaging device according to the first embodiment. 
         FIG.  13    is a diagram showing, in the imaging device according to the first embodiment, a threshold value of an exit pupil distance, first to third exit pupil distance ranges, and an optical characteristic curve. 
         FIG.  14    is a diagram showing a circuit configuration of the pixel of an image sensor according to the first embodiment. 
         FIG.  15    is a diagram showing a configuration of part of the image sensor according to the first embodiment. 
         FIG.  16    is a diagram showing a configuration sample of an AF pixel of an image sensor according to a variation. 
         FIG.  17    is a diagram showing a configuration sample of an AF pixel of an image sensor according to a variation. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG.  1    is a diagram showing a configuration example of an electronic camera  1  (hereinafter, referred to as a camera  1 ) which is an example of an imaging device according to the first embodiment. The camera  1  is configured with a camera body  2  and an interchangeable lens  3 . Since the camera  1  is configured with the camera body  2  and the interchangeable lens  3 , it is sometimes called a camera system. 
     The camera body  2  is provided with a body-side mount unit  201  to which the interchangeable lens  3  is to be attached. The interchangeable lens  3  is provided with a lens-side mount unit  301  that is to be attached to the camera body  2 . The lens-side mount unit  301  and the body-side mount unit  201  are provided with a lens-side connection portion  302  and a body-side connection portion  202 , respectively. The lens-side connection portion  302  and the body-side connection portion  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 supplying power. The interchangeable lens  3  is to be detachably attached to the camera body  2  by the lens-side mount unit  301  and the body-side mount unit  201 . 
     Upon being attached the interchangeable lens  3  to the camera body  2 , the terminal provided on the body-side connection portion  202  and the terminal provided on the lens-side connection portion  302  are electrically connected. Thereby, it becomes to be possible to supply power from the camera body  2  to the interchangeable lens  3  or to communicate between the camera body  2  and the interchangeable lens  3 . 
     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)  31   a  for changing the focal length and a focusing lens (focus adjustment lens)  31   b , and an aperture  31   c , and forms a subject image on the imaging surface  22   a  of the image sensor  22 . Although the zoom lens  31   a  and the focusing lens  31   b  are schematically shown in  FIG.  1   , a common photographing optical system is generally configured with a lot of optical elements. 
     Further, as will be described later, the photographing optical system  31  of the interchangeable lens  3  has an optical characteristic that the position of the exit pupil thereof, that is, 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 surface  22   a , that is, the distance from the optical axis OA 1  of the photographing optical system  31  on the imaging surface  22   a . The optical axis OA 1  of the photographing optical system  31  intersects the imaging surface  22   a  at the center position of the imaging surface  22   a . 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 . It is to be noted, the imaging surface  22   a  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 microlenses are arranged. 
     Moreover, the photographing optical system  31  differs depending on the type of the interchangeable lens  3  to be mounted on the body-side mount unit  201 . Therefore, the exit pupil distance of the photographing optical system  31  differs depending on the type of the interchangeable lens  3 . Further, the optical characteristics in which the exit pupil distance changes depending on the image height, also differ depending on the type of the interchangeable lens  3 . 
     The lens control unit  32  is configured with a processor such as a CPU, FPGA, and ASIC, and a memory such as ROM and 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  31   a , the position of the focusing lens  31   b , and the drive of the aperture  31   c  based on the signal output from a body control unit  210  of the camera body  2 . Upon being input a signal indicating moving direction, movement amount or the like of the focusing lens  31   b  from the body control unit  210 , the lens control unit  32  moves the focusing lens  31   b  forward or backward in the optical axis OA 1  direction based on the signal, to adjust the focal position of the photographing optical system  31 . Further, the lens control unit  32  controls the position of the zoom lens  31   a  and/or the aperture diameter of the aperture  31   c  based on the signal output from the body control unit  210  of the camera body  2 . 
     The lens memory  33  is configured with, for example, a non-volatile storage medium or the like. Information related to the interchangeable lens  3  is stored (recorded) as lens information in the lens memory  33 . The lens information includes data on the optical characteristics (the exit pupil distance and/or an F number) of the photographing optical system  31 , data on the infinity position and the closest position of the focusing lens  31   b , and data on the shortest focal length and the longest focal length of the interchangeable lens  3 . It is to be noted that the lens information differs depending on the type of the interchangeable lens  3 . The lens information may be stored in the internal memory of the lens control unit  32 . Further, the lens information may be stored in the body memory  23  in the camera body  2  described later. In this case, the body memory  23  stores the lens information of the plurality of types of interchangeable lenses  3 . 
     In the present embodiment, the lens information includes information regarding the exit pupil distance of the photographing optical system  31 . Although regarding the information with respect to the exit pupil distance will be described later, it includes the information indicating the exit pupil distance (Co) at the position where the imaging surface  22   a  and the optical axis OA 1  intersect (the position where the image height is zero) and the information on coefficients (h 4 , h 2 ) of the calculation formula showing the relationship between the exit pupil distance and the image height. The writing of data to the lens memory  33  and the reading of data from the lens memory  33  are controlled by the lens control unit  32 . Upon being attached the interchangeable lens  3  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 portion  302  and the body-side connection portion  202 . Further, the lens control unit  32  transmits position information (focal length information) of the zoom lens  31   a  being controlled, position information of the focusing lens  31   b  being controlled, information of the F number of the aperture  31   c  being controlled, and the like to the body control unit  210 . 
     In the present 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 being input information, from the interchangeable lens  3 , regarding the exit pupil distance of the photographing optical system  31 . 
     The lens control unit  32  performs bidirectional communication between the camera body  2  and the interchangeable lens  3  via the terminals of the lens-side connection portion  302  and the body-side connection portion  202 . Upon being input a signal requesting transmission of information (h 4 , h 2 , Co) regarding the exit pupil distance from the camera body  2 , the lens control unit  32  transmits the information regarding the exit pupil distance to the camera body  2 . It is to be noted that the information regarding the exit pupil distance differs depending on the type of the interchangeable lens  3 . Further, the lens control unit  32  may transmit information regarding the exit pupil distance to the camera body  2  each time the image sensor  22  performs an image capturing. The lens control unit  32  may transmit information regarding the exit pupil distance to the camera body  2  in a case where the zoom lens  31   a  moves and the focal length of the photographing optical system  31  changes. The lens control unit  32  may transmit the information on the focal length of the photographing optical system  31  and the information on the exit pupil distance to the camera body  2  by one time bidirectional communication. 
     Next, the configuration of the camera body  2  will be described. The camera body  2  is provided with the image sensor  22 , the body memory  23 , a display unit  24 , an operation unit  25 , and the body control unit  210 . The image sensor  22  is a CMOS image sensor, a CCD image sensor or the like. The image sensor  22  performs an image capturing of a subject image formed by the photographing optical system  31 . In the image sensor  22 , a plurality of pixels each having a photoelectric conversion unit are arranged in two-dimensional manner (row direction and column direction). The photoelectric conversion unit is configured with a photodiode (PD). The image sensor  22  performs photoelectric conversion of the received light by the photoelectric conversion unit to generate a signal, and outputs the generated signal to the body control unit  210 . 
     As will be described later, the image sensor  22  has an imaging pixel that outputs a signal used for image generation and an AF pixel (a focus detection pixel) that outputs a signal used for focus detection. The imaging pixel includes a pixel (hereinafter, referred to as an R pixel) having a filter of a spectral characteristic that spectrally disperses the light having the first wavelength region (red (R) light) from the incident light, a pixel (hereinafter, referred to as a G pixel) having a filter of a spectral characteristic that spectrally disperses the light having the second wavelength region (green (G) light) from the incident light, and a pixel (hereinafter, referred to as a B pixel) having a filter of a spectral characteristic that spectrally disperses the light having the third wavelength region (blue (B) light) from the incident light. The R pixel, the G pixel, and the B pixel are arranged according to the Bayer arrangement. The AF pixels are arranged by replacing a part of the imaging pixels and are dispersedly arranged on substantially the entire surface of the imaging surface  22   a  of the image sensor  22 . It is to be noted, in the following description, in a case the term “pixel” is simply used, it means either one or both of the imaging pixel and the AF pixel. 
     The body memory  23  is configured with, for example, a non-volatile storage medium or the like. In the body memory  23 , an image data, a control program, and the like are recorded. The writing of data to the body memory  23  and the reading of data from the body memory  23  are controlled by the body control unit  210 . The display unit  24  displays an image based on image data, an image showing a focus detection area (an AF area) such as an AF frame, information on photographing such as a shutter speed and the F number, a menu screen, and the like. The operation unit  25  includes various setting switches such as a release button, a power switch, and a switch for switching various modes, and outputs a signal corresponding to each operation to the body control unit  210 . Further, the operation unit  25  is a setting unit capable of setting an arbitrary focus detection area among a plurality of focus detection areas, and a user can select the arbitrary focus detection area by operating the operation unit  25 . 
     The body control unit  210  is configured with a processor such as a CPU, FPGA, and ASIC, and a memory such as ROM and RAM, and controls each part of the camera  1  based on a control program. The body control unit  210  includes an area setting unit  211 , a distance calculation unit  212 , a pixel selection unit  213 , a readout unit  214 , a focus detection unit  215 , and an image data generation unit  216 . 
     The area setting unit  211  sets (selects) at least one focus detection area  100  among the plurality of focus detection areas  100  provided on the imaging surface  22   a  of the image sensor  22  shown in  FIG.  2 ( a ) . The plurality of AF frames displayed on the display unit  24  correspond to the plurality of focus detection areas  100  provided on the image sensor  22 , respectively. The area setting unit  211  sets, among the plurality of AF frames displayed on the display unit  24 , 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  which is selected by the camera  1  in automatically, as the area in which the focus detection is performed. As will be described later, the focus detection unit  215  detects the deviation amount (defocus amount) between the image by the photographing optical system  31  and the imaging surface  22   a  using a signal output from the AF pixel in the focus detection area  100  set by the area setting unit  211 . 
     As shown schematically in  FIG.  2 ( b ) , in the focus detection area  100 , in addition to the imaging pixels, a plurality types of pair of the AF pixels (the AF pixel pairs) are arranged. In the present embodiment, a first AF pixel pair, a second AF pixel pair, and a third AF pixel pair are arranged. The first AF pixel pair, the second AF pixel pair, and the third AF pixel pair are arranged for accurately detecting the defocus amount at the exit pupil distance that differs depending on the image height or the type of interchangeable lens. One of the AF pixel among the AF pixel pair outputs a first signal Sig 1 , and the other of the AF pixel among the AF pixel pair outputs a second signal Sig 2 . The first AF pixel pair, the second AF pixel pair, and the third AF pixel pair will be described later. 
     As shown in  FIG.  2 ( a ) , the plurality of focus detection areas  100  are arranged in two-dimensional directions (row direction and column direction), and the image height differs depending on arranged position. The small region  110   a  (see  FIG.  2 ( b ) ) in the focus detection area  100   a  at the center part of the imaging surface  22   a  is located on the optical axis OA 1  of the photographing optical system  31 , and the image height H here is substantially zero. As the focus detection area  100  being away from the center (optical axis OA 1  of the photographing optical system  31 ) of the imaging surface  22   a , the image height H thereat increases. In other words, as the distance from the center of the imaging surface  22   a  to the focus detection area  100  increases, the image height H thereat increases. Therefore, in the row where the focus detection area  100   a  exists, the focus detection areas  100  farthest from the optical axis OA 1  of the photographing optical system  31  (the image height H is the highest) are a focus detection areas  100   b  and  100   c  located at the left end (the end in the −X direction) and the right end (the end in the +X direction). The focus detection areas  100  at which the image height H is highest in the image sensor  22  are four focus detection areas  100  at the corners of the imaging surface  22   a.    
     Since the focus detection area  100  has a predetermined area, the image height differs for each AF pixel depending on the position in the focus detection area  100 . That is, within the focus detection area  100 , the image height at the central small region  110   a  (see  FIG.  2 ( b ) ) is different from the image heights at the small regions  110   b  and  110   c  located at the left end (end in the −X direction) and the right end (end in the +X direction) respectively (see  FIG.  2 ( b ) ). However, in the present embodiment, the value of the image height H at the center position of one focus detection area  100  is used as the value representing the image height of the entire focus detection area  100 . The image height of the focus detection area  100   a  in the center part of the imaging surface  22   a  is zero, and the image heights of the focus detection areas  100   b  and  100   c  are predetermined image heights H. 
     The distance calculation unit  212  calculates the exit pupil distance of the photographing optical system  31  at the image height H. The distance calculation unit  212  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  211  by the following formula (1).
 
 Po ( H )= h 4× H   4   +h 2× H   2   +Co   (1)
 
     Formula (1) is a calculation formula with the image height H as a variable, the parameter (h 4 ) is the coefficient of the fourth-order term of the variable H, the parameter (h 2 ) 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 OA 1  on the imaging surface  22   a ). The parameters (h 4 ), (h 2 ), and the constant term Co are information on the exit pupil distances corresponding to different image heights, and are values determined by the optical characteristics of the photographing optical system  31 . Information indicating the parameters (h 4 ), (h 2 ) and the constant term Co is transmitted from the interchangeable lens  3  to the camera body  2  as lens information. It is to be noted, the calculation formula (1) is stored in the internal memory of the body control unit  210 . 
     Based on the image height H of the focus detection area  100  set by the area setting unit  211 , the lens information (h 4 , h 2 , Co), and the calculation formula (1), the distance calculation unit  212  calculates the exit pupil distance Po (H) for the image height H of the focus detection area  100  having been set. It is to be noted that the calculation formula (1) may be stored in the internal memory of the lens control unit  32 . The lens control unit  32  may transmit the calculation formula (1) to the camera body  2  as lens information together with the parameters (h 4 ), (h 2 ) and the constant term Co. 
     The pixel selection unit  213  selects at least one type of the AF pixel pair among a plurality of types of the AF pixel pairs provided in the image sensor  22 . In the present embodiment, the pixel selection unit  213  selects any one type of three types of the AF pixel pairs (the first to third AF pixel pairs) arranged in the focus detection area  100  set by the area setting unit  211 . As will be described later, the pixel selection unit  213  selects the AF pixel pair suitable for the exit pupil distance Po (H) calculated by the distance calculation unit  212  from among three types of the AF pixel pairs. In a case that a plurality of focus detection areas  100  are set by the area setting unit  211 , the pixel selection unit  213  selects the same type of the AF pixel pair in each selected focus detection area  100 . 
     The readout unit  214  reads out a signal from the image sensor  22 . In a case displaying a through image (live view image) of the subject on the display unit  24  and/or in a case shooting a moving image, the readout unit  214  reads out a signal used for image generation and/or a signal used for focus detection from the image sensor  22  at a predetermined cycle. The readout unit  214  sequentially selects the pixels of the image sensor  22  in row units and reads out the signal from the selected pixel row, that is, by a so-called rolling shutter method. 
     The readout unit  214  can perform to read out in a first readout mode and in a second readout mode. In the first readout mode, the readout unit  214  sequentially selects a row of pixels (hereinafter referred to as AF pixel row) in which the AF pixels constituting the AF pixel pair selected by the pixel selection unit  213  are arranged and a row of pixels (hereinafter referred to as an imaging pixel row) in which the AF pixel is not arranged, and reads out a signal from each pixel. In the second readout mode, the readout unit  214  separately reads out signals from the AF pixel row and from the imaging pixel row. 
     For example, the readout unit  214  reads out in the first readout mode in a case continuously shooting still images or in a case shooting a high-resolution moving image (for example, 4K moving image shooting). The readout unit  214  reads out in the second readout mode in a case displaying a through image on the display unit  24  or in a case performing low-resolution moving image shooting (for example, Full HD moving image shooting). The first readout mode and the second readout mode will be described later. 
     The focus detection unit  215  performs focus detection processing necessary for automatic focus adjustment (AF) of the photographing optical system  31 . The focus detection unit  215  detects the focus position (movement amount of the focusing lens  31   b  to the focusing position) for focusing (forming) the image formed by the photographing optical system  31  on the imaging surface  22   a . The focus detection unit  215  calculates the defocus amount by the pupil division type phase difference detection method using the first and second signals Sig 1  and Sig 2  of the AF pixel pair read out by the readout unit  214 . 
     The focus detection unit  215  calculates an image shift amount by performing correlation calculation with a first signal Sig 1  generated by capturing an image formed of a first light flux passed through a first pupil region of the exit pupil of the photographing optical system  31  and a second signal Sig 2  generated by capturing an image formed of a second light flux passed through a second pupil region of the exit pupil of the photographing optical system  31 . The focus detection unit  215  converts the image shift amount into a defocus amount based on a predetermined conversion formula. The focus detection unit  215  calculates the movement amount of the focusing lens  31   b  to the in-focus position based on the calculated defocus amount. 
     The focus detection unit  215  determines whether or not the defocus amount is within the permissible value. If the defocus amount is within the permissible value, the focus detection unit  215  determines that being an in-focus state. On the other hand, if the defocus amount exceeds the permissible value, the focus detection unit  215  determines that not being in-focus state and transmits signal for instructing the movement amount and moving operation of the focusing lens  31   b  to the lens control unit  32  of the interchangeable lens  3 . Focus adjustment is performed automatically by the lens control unit  32  moving the focusing lens  31   b  according to the movement amount. 
     Further, the focus detection unit  215  can also perform the focus detection processing by the contrast detection method in addition to the focus detection processing by the phase difference detection method. The body control unit  210  calculates the contrast evaluation value of the subject image one after another based on the signal output from the imaging pixels while moving the focusing lens  31   b  of the photographing optical system  31  along the optical axis OA 1  direction. The body control unit  210  associates the position of the focusing lens  31   b  and the contrast evaluation value by using the position information of the focusing lens  31   b  transmitted from the interchangeable lens  3 . Then, the body control unit  210  detects the position of the focusing lens  31   b  at which shows the peak value of the contrast evaluation value, that is, the maximum value, as the in-focus position. The body control unit  210  transmits information on the position of the focusing lens  31   b  corresponding to the detected focusing position to the lens control unit  32 . The lens control unit  32  moves the focusing lens  31   b  to the in-focus position to perform the focus adjustment. 
     The image data generation unit  216  generates image data by performing various image processing on the signals read out from the imaging pixels by the readout unit  214 . It is to be noted that the image data generation unit  216  may generate image data also using signals output from the AF pixels. 
       FIG.  3    is a diagram showing an arrangement example of pixels in the focus detection area  100 . The R pixel  13 , the G pixel  13 , and the B pixel  13  are arranged according to the Bayer arrangement. The first AF pixel  11  and the second AF pixel  12  are arranged by being replaced to a part of the imaging pixels  13  of the R, G, and B arranged in the Bayer arrangement. The first AF pixel  11  and the second AF pixel  12  each have a light-shielding portion  43 . The position of the light-shielding portion  43  in the first AF pixel  11  is different from the position of the light-shielding portion  43  in the second AF pixel  12 . 
     As shown in  FIG.  3   , the image sensor  22  has a pixel group (a first imaging pixel row)  401  in which the R pixels  13  and the G pixels  13  are alternately arranged in left-right direction, that is, the row direction, and a pixel group (a second imaging pixel row)  402  in which the G pixels  13  and the B pixels  13  are alternately arranged in the row direction. Further, the image sensor  22  has a pixel group (a first AF pixel row)  403  in which the G pixels  13  and the first AF pixels  11  are alternately arranged in the row direction, and a pixel group (a second AF pixel row)  404  in which the G pixels  13  and the second AF pixels  12  are alternately arranged in the row direction. 
     In a first AF pixel row  403   a , the first AF pixels  11   a  and the G pixels  13  are alternately arranged. In a second AF pixel row  404   a , which is separated from the first AF pixel row  403   a  with a predetermined number of rows, the second AF pixels  12   a  and the G pixels  13  are alternately arranged. It is to be noted, the arrangement position of the first AF pixel  11   a  in the first AF pixel row  403   a  and the arrangement position of the second AF pixel  12   a  in the second AF pixel row  404   a  are the same as each other. That is, the first AF pixel  11   a  and the second AF pixel  12   a  are arranged in the same column. The first AF pixel  11   a  of the first AF pixel row  403   a  and the second AF pixel  12   a  of the second AF pixel row  404   a  compose the first AF pixel pair. 
     In the first AF pixel row  403   b , which is separated from the second AF pixel row  404   a  with a predetermined number of rows, the first AF pixels  11   b  and the G pixels  13  are alternately arranged. In the second AF pixel row  404   b , which is separated from the first AF pixel row  403   b  with a predetermined number of rows, the second AF pixels  12   b  and the G pixels  13  are alternately arranged. It is to be noted, the arrangement position of the first AF pixel  11   b  in the first AF pixel row  403   b  and the arrangement position of the second AF pixel  12   b  in the second AF pixel row  404   b  are the same as each other. That is, the first AF pixel  11   b  and the second AF pixel  12   b  are arranged in the same column. The first AF pixel  11   b  of the first AF pixel row  403   b  and the second AF pixel  12   b  of the second AF pixel row  404   b  compose the second AF pixel pair. 
     In the first AF pixel row  403   c , which is separated from the second AF pixel row  404   b  with a predetermined number of rows, the first AF pixels  11   c  and the G pixels  13  are alternately arranged. In the second AF pixel row  404   c , which is separated from the first AF pixel row  403   c  with a predetermined number of rows, the second AF pixels  12   c  and the G pixels  13  are alternately arranged. It is to be noted, the arrangement position of the first AF pixel  11   c  in the first AF pixel row  403   c  and the arrangement position of the second AF pixel  12   c  in the second AF pixel row  404   c  are the same as each other. That is, the first AF pixel  11   c  and the second AF pixel  12   c  are arranged in the same column. The first AF pixel  11   c  of the first AF pixel row  403   c  and the second AF pixel  12   c  of the second AF pixel row  404   c  compose the third AF pixel pair. 
     It is to be noted, the first AF pixel row  403   a  and the second AF pixel row  404   a  may be arranged in a plurality of rows, respectively, and a plurality of the first AF pixel pairs may be arranged. Further, the first AF pixel row  403   b  and the second AF pixel row  404   b  may be arranged in a plurality of rows, respectively, and a plurality of the second AF pixel pairs may be arranged. The first AF pixel row  403   c  and the second AF pixel row  404   c  may be arranged in a plurality of rows, respectively, and a plurality of the third AF pixel pairs may be arranged. 
     As described above, the first, second and third AF pixel pairs are arranged so as to accurately detect defocus amount even if the exit pupil distance changes depending on an image height or a type of the interchangeable lens. Accordingly, except for in the pixel pairs arranged around the optical axis OA 1  (the center of the imaging surface  22   a ) of the photographing optical system  31 , areas of the light-shielding portions of the first, second and third AF pixel pairs are different to each other. Except for the AF pixels around the optical axis OA 1  of the photographing optical system  31 , the incident angles of the light incident on the AF pixels are different depending on the exit pupil distances being different. The incident angle increases as the exit pupil distance decreases, and the incident angle decreases as the exit pupil distance increases. The area of the light-shielding portion  43  differs depending on the AF pixel pair in order to block a part of the light incident at different incident angles depending on the exit pupil distance. Thereby, the focus detection unit  215  can accurately detect the defocus amount even if the exit pupil distance differs. It is to be noted, with respect to the pixel pair around the optical axis OA 1  (center of the imaging surface  22   a ) of the photographing optical system  31 , an incident angle is 0° in regardless of the exit pupil distance. Therefore, 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 the same. As will be described later, the area of the light-shielding portion  43  differs also depending on the position (image height) of the AF pixel. 
     Each of the first AF pixels  11   a ,  11   b ,  11   c  and the second AF pixels  12   a ,  12   b ,  12   c  is provided with a filter having spectral characteristics that spectrally disperses the second wavelength region (green (G)) of the incident light. It is to be noted, the filter being provided with each of the AF pixels of the first AF pixels  11   a  to  11   c  and the second AF pixels  12   a  to  12   c  may have spectral characteristics that spectrally disperses the first wavelength range (red (R) light) or the third wavelength range (blue (B) light). Alternatively, the first AF pixels  11   a  to  11   c  and the second AF pixels  12   a  to  12   c  may have filters having spectral characteristics that spectrally disperses the first, second, and third wavelength regions of the incident light. 
       FIG.  4    is a diagram for explaining a configuration example of an AF pixel and an imaging pixel provided in the image sensor  22  according to the first embodiment.  FIG.  4 ( a )  shows an example of a cross section of the first AF pixel  11  among the first and second AF pixels  11  and  12  constituting the AF pixel pair.  FIG.  4 ( b )  shows an example of a cross section of the second AF pixel  12  among the first and second AF pixels  11  and  12  constituting the AF pixel pair.  FIG.  4 ( c )  shows an example of a cross section of the imaging pixel  13  (R pixel, G pixel, B pixel). 
     In  FIG.  4   , each of the first and second AF pixels  11  and  12  and the imaging pixel  13  includes a microlens  44 , a color filter  51 , and a photoelectric conversion unit  42  (PD 42 ) which photoelectrically converts the light transmitted (passed) through the microlens  44  and the color filter  51 . The first light flux  61  is a light flux that has passed through the first pupil region of the exit pupil of the photographing optical system  31  among divided in substantially two equal regions. The second light flux  62  is a light flux that has passed through the second pupil region of the exit pupil of the photographing optical system  31  among divided in substantially two equal regions. 
     In  FIG.  4 ( a ) , the first AF pixel  11  is provided with a light-shielding portion  43 L that blocks the second light flux  62  among the first and second light fluxes  61  and  62 . The light-shielding portion  43 L is provided, between the color filter  51  and the photoelectric conversion unit  42  and so as to position above the photoelectric conversion unit  42 . In the example shown in  FIG.  4 ( a ) , the light-shielding portion  43 L is arranged so as to block the left half (−X direction side) of the photoelectric conversion unit  42 . The right end (end in the +X direction) of the light-shielding portion  43 L substantially coincides with the center line that bisects the photoelectric conversion portion  42  to the left and right. The photoelectric conversion unit  42  of the first AF pixel  11  receives the first light flux  61 . The photoelectric conversion unit  42  of the first AF pixel  11  photoelectrically converts the first light flux  61  to generate an electric charge, and the first AF pixel  11  outputs signal Sig 1  based on the electric charge generated by the photoelectric conversion unit  42 . 
     The area of the light-shielding portion  43 L differs depending on the position (image height) of the first AF pixel  11 , except for the first AF pixel  11  around the optical axis OA 1  (center of the imaging surface  22   a ) of the photographing optical system  31 . If the position of the first AF pixel  11  differs, that is, the image height differs, the incident angle of the light incident to the first AF pixel  11  differs. If the image height increases, the incident angle increases, if the image height decrease, the incident angle decreases, and if the image height is 0, the incident angle is 0°. The area of the light-shielding portion  43 L differs depending on the image height in order to block the second light flux  62  of the light incident at the incident angle that differs depending on the image height. 
     In  FIG.  4 ( b ) , the second AF pixel  12  is provided with a light-shielding portion  43 R that blocks the first light flux  61  among the first and second light fluxes  61  and  62 . The light-shielding portion  43 R is provided, between the color filter  51  and the photoelectric conversion unit  42  and so as to position above the photoelectric conversion unit  42 . In the example shown in  FIG.  4 ( b ) , the light-shielding portion  43 R is arranged so as to block the right half (+X direction side) of the photoelectric conversion unit  42 . The left end (end in the −X direction) of the light-shielding portion  43 R substantially coincides with the center line that bisects the photoelectric conversion portion  42  to the left and right. The photoelectric conversion unit  42  of the second AF pixel  12  receives the second light flux  62 . The photoelectric conversion unit  42  of the second AF pixel  12  photoelectrically converts the second light flux  62  to generate an electric charge, and the second AF pixel  12  outputs signal Sig 2  based on the electric charge generated by the photoelectric conversion unit  42 . 
     Similarly to that of the first AF pixel  11 , the area of the light-shielding portion  43 R differs depending on the position (image height) of the second AF pixel  12 , except for the second AF pixel  12  around the optical axis OA 1  (center of the imaging surface  22   a ) of the photographing optical system  31 . The area of the light-shielding portion  43 R differs depending on the image height in order to block the first light flux  61  of the light incident at the incident angle that differs depending on the image height. 
       FIG.  4 ( c )  shows that the photoelectric conversion unit  42  of the imaging pixel  13  receives the first and second light fluxes  61  and  62  that have passed through the first and second pupil regions of the exit pupil of the photographing optical system  31 . The photoelectric conversion unit  42  of the imaging pixel  13  photoelectrically converts the first and second light fluxes  61  and  62  to generate an electric charge, and the imaging pixel  13  outputs signal based on the electric charge generated by the photoelectric conversion unit  42 . 
       FIG.  5    is a cross-sectional view of three types of AF pixel pairs arranged in a small region  110   a  (see  FIG.  2 ( b ) ) within the focus detection area  100   a .  FIG.  5 ( a )  shows the first and second AF pixels  11   a  and  12   a  constituting the first AF pixel pair arranged in the first AF pixel row  403   a  and the second AF pixel row  404   a  of  FIG.  3   , respectively.  FIG.  5 ( b )  shows the first and second AF pixels  11   b  and  12   b  constituting the second AF pixel pair arranged in the first AF pixel row  403   b  and the second AF pixel row  404   b  of  FIG.  3   , respectively.  FIG.  5 ( c )  shows the first and second AF pixels  11   c  and  12   c  constituting the third AF pixel pair arranged in the first AF pixel row  403   c  and the second AF pixel row  404   c  of  FIG.  3   , respectively. As shown in  FIG.  5   , in each of the first AF pixels  11   a  to  11   c  and the second AF pixels  12   a  to  12   c , the center line of the photoelectric conversion unit  42  and the optical axis OA 2  of the microlens  44  substantially coincide. Light incident at an incident angle of 0° with respect to the optical axis OA 2  of the microlens  44  is focused on the optical axis OA 2  of the microlens. Since the line passing through the center of the photoelectric conversion unit  42  coincides with the optical axis OA 2  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 a line passing through the center of the photoelectric conversion unit  42 . 
     In the first AF pixel  11   a  shown in  FIG.  5 ( a ) , the right end (end in the +X direction) of the light-shielding portion  43 L substantially coincides with the optical axis OA 2  of the microlens  44 . The light-shielding portion  43 L of the first AF pixel  11   a  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  43 L without being incident on the photoelectric conversion unit  42 . Thereby, the photoelectric conversion unit  42  of the first AF pixel  11   a  receives the first light flux  61 . In the second AF pixel  12   a , the left end (end in the −X direction) of the light-shielding portion  43 R substantially coincides with the optical axis OA 2  of the microlens  44 . The first light flux  61  transmitted through the microlens  44  is shielded by the light-shielding portion  43 R without being incident on the photoelectric conversion unit  42 . Thereby, the photoelectric conversion unit  42  of the second AF pixel  12   a  receives the second light flux  62 . 
     In each of the first AF pixels  11   b  and  11   c  shown in  FIG.  5 ( b )  and  FIG.  5 ( c ) , the right end (end in the +X direction) of the light-shielding portion  43 L substantially coincides with the optical axis OA 2  of the microlens  44 . Therefore, each photoelectric conversion unit  42  of the first AF pixels  11   b  and  11   c , similarly to that of the first AF pixel  11   a , receives the first light flux  61 . Further, in each of the second AF pixels  12   b  and  12   c , the left end (end in the −X direction) of the light shielding portion  43 R substantially coincides with the optical axis OA 2  of the microlens  44 . Therefore, similarly to the first AF pixel  12   a , each photoelectric conversion unit  42  of the second AF pixels  12   b  and  12   c  receives the second light flux  62 . 
       FIG.  6    is a cross-sectional view of three types of AF pixel pairs arranged in a small region  110   c  (see  FIG.  2 ( b ) ) separated from the small region  110   a  in the focus detection area  100   a  in the +X direction.  FIG.  6 ( a )  shows the first and second AF pixels  11   a  and  12   a  constituting the first AF pixel pair.  FIG.  6 ( b )  shows the first and second AF pixels  11   b  and  12   b  constituting the second AF pixel pair.  FIG.  6 ( c )  shows the first and second AF pixels  11   c  and  12   c  constituting the third AF pixel pair. 
     As shown in  FIG.  6   , in each of the first AF pixels  11   a  to  11   c  and the second AF pixels  12   a  to  12   c , a line passing through the center of the photoelectric conversion unit  42  is being shifted in the +X direction with respect to the optical axis OA 2  of the microlens  44 . In the present embodiment, in the first and second AF pixels arranged apart from the small region  110   a  in the +X direction, the line passing through the center of the photoelectric conversion unit  42  is being shifted in the +X direction with respect to the optical axis OA 2  of the microlens  44 . Further, in the first and second AF pixels arranged apart from the small region  110   a  in the −X direction, the line passing through the center of the photoelectric conversion unit  42  is being shifted in the −X direction with respect to the optical axis OA 2  of the microlens  44 . 
     As shown in  FIG.  6   , the areas of the light-shielding portions  43 L of the first AF pixels  11   a  to  11   c  are different to each other. The area of the light-shielding portion  43 L of the first AF pixel  11   a  is smaller than the area of the light-shielding portion  43 L of the first AF pixel  11   b . The area of the light-shielding portion  43 L of the first AF pixel  11   b  is smaller than the area of the light-shielding portion  43 L of the first AF pixel  11   c . The areas of the light-shielding portions  43 R of the second AF pixels  12   a  to  12   c  are different to each other. The area of the light-shielding portion  43 R of the second AF pixel  12   a  is larger than the area of the light-shielding portion  43 R of the second AF pixel  12   b . The area of the light-shielding portion  43 R of the second AF pixel  12   b  is larger than the area of the light-shielding portion  43 R of the second AF pixel  12   c.    
     As shown in  FIG.  6   , the line passing through the center line of the photoelectric conversion unit  42  and the optical axis OA 2  of the microlens  44  are deviated, and the area of the light-shielding portions  43  of the first AF pixel and the area of the light-shielding portions  43  of the second AF pixel are different. Thus, in each of the first and second AF pixels, the edge of the light-shielding portion and the optical axis OA 2  of the microlens  44  are deviated from each other. In  FIG.  6 ( a ) , for example, in the first AF pixel  11   a , the right end (end in the +X direction) of the light-shielding portion  43 L is located on the +X direction side by the deviation amount d 1  from the optical axis OA 2  of the microlens  44 . Further, in the second AF pixel  12   a , the left end (end in the −X direction) of the light-shielding portion  43 R is located on the +X direction side by the deviation amount d 1  from the optical axis OA 2  of the microlens  44 . 
     As shown in  FIG.  6   , each of the deviation amounts in the second and third AF pixel pairs is different from the deviation amount in the first AF pixel pair. The deviation amount d 2  in the first and second AF pixels  11   b  and  12   b  constituting the second AF pixel pair is larger than the deviation amount d 1  in the first and second AF pixels  11   a  and  12   a  constituting the first AF pixel pair. The deviation amount d 3  in the first and second AF pixels  11   c  and  12   c  constituting the third AF pixel pair is larger than the deviation amount d 2  in the first and second AF pixels  11   b  and  12   b  constituting the second AF pixel pair. That is, d 1 &lt;d 2 &lt;d 3 . 
       FIG.  7    is a cross-sectional view of three types of AF pixel pairs in a part of the focus detection area  100   c  separated from the focus detection region  100   a  shown in  FIG.  2    in the +X direction.  FIG.  7 ( a )  shows the first and second AF pixels  11   a  and  12   a  constituting the first AF pixel pair.  FIG.  7 ( b )  shows the first and second AF pixels  11   b  and  12   b  constituting the second AF pixel pair.  FIG.  7 ( c )  shows the first and second AF pixels  11   c  and  12   c  constituting the third AF pixel pair. 
     Similarly to the three types of AF pixel pairs shown in  FIG.  6   , in each of the first AF pixels  11   a  to  11   c  and the second AF pixels  12   a  to  12   c  shown in  FIG.  7   , a line passing through the center of the photoelectric conversion unit  42  is being shifted in the +X direction with respect to the optical axis OA 2  of the microlens  44 . Further, similarly to the three types of AF pixel pairs shown in  FIG.  6   , the areas of the light-shielding portions  43 L of the first AF pixels  11   a  to  11   c  are different to each other. Also, the areas of the light-shielding portions  43 R of the second AF pixels  12   a  to  12   c  are different to each other. 
     In the three types of AF pixel pairs shown in  FIG.  6    and  FIG.  7   , each of the amounts of deviation of the line passing through the center of the photoelectric conversion unit  42  with respect to the optical axis OA 2  of the microlens  44  differs to each other. Further, in the AF pixels other than the first AF pixel  11   b  and the second AF pixel  12   b , the area of the light-shielding portion  43 L and the area of the light-shielding portion  43 R are different. Compared with the three types of AF pixel pairs shown in  FIG.  6   , the three types of AF pixel pairs shown in  FIG.  7    have a larger deviation amount with respect to the optical axis OA 2  of the microlens  44 . Further, as compared with the first AF pixel  11   a  and the second AF pixel  12   a  shown in  FIG.  6   , the first AF pixel  11   a  and the second AF pixel  12   a  shown in  FIG.  7    respectively have a smaller area of the light-shielding portion  43 L and a larger area of the light-shielding portion  43 R. As compared with the first AF pixel  11   c  and the second AF pixel  12   c  shown in  FIG.  6   , the first AF pixel  11   c  and the second AF pixel  12   c  shown in  FIG.  7    respectively have a larger area of the light-shielding portion  43 L and a smaller area of the light-shielding portion  43 R. The areas of the light-shielding portion  43 L and the light-shielding portion  43 R in each of the first AF pixel  11   b  and the second AF pixel  12   b  shown in  FIG.  7    are the same as the areas of those shown in  FIG.  6   . 
     In the first AF pixel  11   a , the right end (end in the +X direction) of the light-shielding portion  43 L is deviated by the amount d 4  in the +X direction with respect to the optical axis OA 2  of the microlens  44 . In the second AF pixel  12   a , the left end (end in the −X direction) of the light-shielding portion  43 R is deviated by the amount d 4  in the +X direction with respect to the optical axis OA 2  of the microlens  44 . 
     Each of the deviation amounts in the second and third AF pixel pairs is different from the deviation amount in the first AF pixel pair. The deviation amount d 5  in the first and second AF pixels  11   b  and  12   b  constituting the second AF pixel pair is larger than the deviation amount d 4  in the first and second AF pixels  11   a  and  12   a  constituting the first AF pixel pair. The deviation amount d 6  in the first and second AF pixels  11   c  and  12   c  constituting the third AF pixel pair is larger than the deviation amount d 5  in the first and second AF pixels  11   b  and  12   b  constituting the second AF pixel pair. That is, d 4 &lt;d 5 &lt;d 6 . 
     As shown in  FIG.  5   ,  FIG.  6    and  FIG.  7   , the deviation amount between the line passing through the center of the photoelectric conversion unit  42  and the optical axis OA 2  of the microlens  44  differs depending on the image height. The higher the image height, the larger the deviation amount, and the lower the image height, the smaller the deviation amount. At a position where the image height is high, light passes through the photographing optical system  31  and is obliquely incident to the microlens  44 . That is, the light is incident at an incident angle larger than 0° with respect to the optical axis OA 2  of the microlens  44 . Therefore, it can also be said that the larger the incident angle of light with respect to the microlens  44 , the larger the deviation amount. Incident light having an incident angle larger than 0° with respect to the optical axis OA 2  of the microlens  44  is focused as shifting in the +X direction or −X direction from the optical axis OA 2  of the microlens. Because the line passing through the center of the photoelectric conversion unit  42  and the optical axis OA 2  of the microlens  44  deviate from each other, 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 a line passing through the center of the photoelectric conversion unit  42 . Thereby, the amount of light transmitted through the photographing optical system  31  and incident on the photoelectric conversion unit  42  can be increased. 
     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, each of the first AF pixel pair, the second AF pixel pair, and the third AF pixel pair has a light-shielding portion  43  having a different area in order to accurately detect the defocus amount at different exit pupil distances. Further, the area of the light-shielding portion  43 L and the area of the light-shielding portion  43 R of the first AF pixel pair differ depending on the position (image height) where 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 a light-shielding portion  43 L and a light-shielding portion  43 R having an area that differs depending on the image height in order to accurately detect the defocus amount at different exit pupil distances. The same applies to the third AF pixel pair as in the first AF pixel pair. Thereby, the focus detection unit  215  can accurately detect the defocus amount even at different exit pupil distances. That is, the focus detection unit  215  can accurately detect the defocus amount even if the image height or the type of the interchangeable lens changes. 
     In the first to third AF pixel pairs, the deviation amount between the light-shielding portion  43  and the optical axis of the microlens  44  increases as the image height increases in the +X direction from the small region  110   a  shown in  FIG.  2 ( b ) . Comparing the deviation amounts of the first to third AF pixel pairs in the three regions where the image heights are Ha, Hb, and Hc (Ha&lt;Hb&lt;Hc) is as follows. The deviation amount in the first AF pixel pair at the region of image height Hb is larger than the deviation amount in the first AF pixel pair at the region of image height Ha, and is smaller than the deviation amount in the first AF pixel pair at the region of image height Hc. Similarly, the deviation amount in each the second and third AF pixel pairs at the region of image height Hb is respectively larger than the deviation amount in each the second and third AF pixel pairs at the region of image height Ha, and is respectively smaller than the deviation amount in each the second and third AF pixel pairs at the region of image height Hc. The deviation amount d 4  in the first AF pixel pair arranged in the focus detection area  100   c  shown in  FIG.  7    is larger than the deviation amount d 1  in the first AF pixel pair arranged in the small region  110   c  shown in  FIG.  6   . The deviation amounts d 5  and d 6  in the second and third AF pixel pairs arranged in the focus detection region  100   c  shown in  FIG.  7    are respectively larger than the deviation amounts d 2  and d 3  in the second and third AF pixel pairs arranged in the small region  110   c  shown in  FIG.  6   . 
     To the first to third AF pixel pairs arranged in the small region  110   b  separated from the small region  110   a  shown in  FIG.  2 ( b )  in the −X direction, deviation amounts of the same amount as d 1  to d 3  are respectively given in the direction opposite to the deviation direction shown in  FIG.  6   . To the first to third AF pixel pairs arranged in the small region  110   b  shown in  FIG.  2 ( a ) , deviation amounts of the same amount as d 4  to d 6  are respectively given in the direction opposite to the deviation direction shown in  FIG.  7   . The deviation amount in the first to third AF pixel pairs arranged apart from the small region  110   a  in the −X direction also increases as the image height increases. 
     As described above, the deviation amounts in the first to third AF pixel pairs are different from each other. Therefore, on the surfaces intersecting in the light incident direction, the areas of light receiving portions of the photoelectric conversion units  42  in each of the first AF pixels  11   a  to  11   c  are different from each other, and the areas of light receiving portions of the photoelectric conversion units  42  in each of the second AF pixels  12   a  to  12   c  are different from each other. As described above, in the present embodiment, since the light receiving areas of the photoelectric conversion units  42  are different from each other in the first to third AF pixel pairs, it is possible to perform pupil division corresponding to different incident angles. As a result, the focus detection unit  215  can accurately detect the defocus amount. 
     Next, an example of a method for determining the deviation amounts in the first to third AF pixel pairs in the focus detection area  100  will be described. In  FIG.  8 ,  110     a  represents the position of the small region  110  located at a distance corresponding to the image height Hd from the position 0 (the center position of the imaging surface  22   a ) where the optical axis OA 1  of the photographing optical system  31  intersects the imaging surface  22   a  of the image sensor  22 . A first reference exit pupil EP 1 , a second reference exit pupil EP 2 , and a third reference exit pupil EP 3  are set on the optical axis OA 1  of the photographing optical system  31 . The second reference exit pupil EP 2  exists closer to the imaging surface  22   a  than the first reference exit pupil EP 1  and exists to the +Z direction side than the first reference exit pupil EP 1 . The third reference exit pupil EP 3  exists closer to the imaging surface  22   a  than the second reference exit pupil EP 2  and exists to the +Z direction side than the second reference exit pupil EP 2 . 
     The distance between the first reference exit pupil EP 1  and the imaging surface  22   a  is defined as the first reference exit pupil distance Po 1 , the distance between the second reference exit pupil EP 2  and the imaging surface  22   a  is defined as the second reference exit pupil distance Po 2 , and the distance between the third reference exit pupil EP 3  and the imaging surface  22   a  is defined as the third reference exit pupil distance Po 3 . It is to be noted that Po 1 &gt;Po 2 &gt;Po 3 . 
     In  FIG.  8   , L 1  indicates the principal ray of the light flux that passes through the first reference exit pupil EP 1  and is incident on the AF pixel in the small region  110  at the position  110 α. L 2  indicates the principal ray of the light flux that passes through the second reference exit pupil EP 2  and is incident on the AF pixel in the small region  110  at the position  110 α. L 3  indicates the principal ray of the light flux that passes through the third reference exit pupil EP 3  and is incident on the AF pixel in the small region  110  at the position  110 α. 
     In  FIG.  8   , assuming that θ 1  is the angle of incidence of the principal ray L 1  to the AF pixel, the deviation amount in the first AF pixel pair in the small region  110  at the image height Hd is determined based on the angle of incidence θ 1 . Similarly, assuming that θ 2  and θ 3  respectively are the angles of incidence of the principal rays L 2  and L 3  to the AF pixels, the deviation amounts in the second and third AF pixel pairs in the small region  110  at the image height Hd are determined based on the angles of incidence θ 2  and θ 3 , respectively. As described above, the deviation amount increases as the incident angle increases. Further, except for the position where the image height is 0 (position 0), the longer the exit pupil distance, the smaller the incident angle, so that θ 1 &lt;θ 2 &lt;θ 3 . Therefore, in the first, second, and third AF pixel pairs shown in  FIGS.  6 ( a ) through  6 ( c ) , the deviation amounts d 1 , d 2 , and d 3  are as d 1 &lt;d 2 &lt;d 3 . Further, in the first, second, and third AF pixel pairs shown in  FIGS.  7 ( a ) through  7 ( c ) , the deviation amounts d 4 , d 5 , and d 6  are as d 4 &lt;d 5 &lt;d 6 . 
     In such a way, the deviation amount of the first AF pixel pair with respect to the first reference exit pupil EP 1  (the first reference exit pupil distance Po 1 ) is determined. Similarly, the deviation amount of the second AF pixel pair with respect to the second reference exit pupil EP 2  (the second reference exit pupil distance Po 2 ) and the deviation amount of the third AF pixel pair with respect to the third reference exit pupil EP 3  (the third reference exit pupil distance Po 3 ) are determined. 
     Next, the relationship between the exit pupil distance of the photographing optical system  31  and the first to third AF pixel pairs will be described. As shown in  FIG.  8   , a first threshold value Th 1  regarding the exit pupil distance is set at an intermediate position between the first reference exit pupil EP 1  and the second reference exit pupil EP 2 , and a second threshold value Th 2  regarding the exit pupil distance is set at an intermediate position between the second reference exit pupil EP 2  and the third reference exit pupil EP 3 . The region where the exit pupil distance is equal to or greater than the first threshold Th 1  is defined as a first exit pupil distance range R 1 , the region where the exit pupil distance is between the first threshold Th 1  and the second threshold Th 2  is defined as a second exit pupil distance range R 2 , and the region where the exit pupil distance is equal to or less than the second threshold Th 2  is defined as a third exit pupil distance range R 3 . 
     In a case that the exit pupil distance of the photographing optical system  31  is equal to or greater than the first threshold Th 1 , that is, in a case that the exit pupil distance of the photographing optical system  31  belongs to the first exit pupil distance range R 1 , the pixel selection unit  213  selects the first AF pixel pair. In a case that the exit pupil distance of the photographing optical system  31  is between the first threshold Th 1  and the second threshold Th 2 , that is, in a case that the exit pupil distance of the photographing optical system  31  belongs to the second exit pupil distance range R 2 , the pixel selection unit  213  selects the second AF pixel pair. In a case that the exit pupil distance of the photographing optical system  31  is equal to or less than the second threshold Th 2 , that is, in a case that the exit pupil distance of the photographing optical system  31  belongs to the third exit pupil distance range R 3 , the pixel selection unit  213  selects the third AF pixel pair. 
     As described above, the pixel selection unit  213  selects an appropriate AF pixel pair from the first to third AF pixel pairs depending on, which the exit pupil distance of the photographing optical system belongs to among the first to third exit pupil distance ranges R 1  to R 3 . 
     Next, the optical characteristics of the photographing optical system  31  of the interchangeable lens  3 , specifically, the optical characteristics in which the exit pupil distance thereof changes depending on the image height will be described.  FIG.  9    shows the optical characteristics of the interchangeable lens  3  to be mounted on the camera body  2  shown in  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.  FIG.  9 ( a ) ,  FIG.  9 ( b ) ,  FIG.  9 ( c ) , and  FIG.  9 ( d )  respectively show the optical characteristics of different types of interchangeable lenses. With respect to the optical characteristics of the photographing optical system  31  of the interchangeable lens  3 , which is represented by the optical characteristic curve  200   a  in  FIG.  9 ( a ) , the exit pupil distance Po decreases as the image height H increases. The optical characteristic curve  200   a  in  FIG.  9 ( a )  shows that, the exit pupil distance is Poa at image height zero, the exit pupil distance gradually decreases as the image height H increases, and the exit pupil distance becomes (Poa−Δp 1 ) at the maximum image height Hmax. 
     With respect to the optical characteristics of the photographing optical system  31  of the interchangeable lens  3 , which is represented by the optical characteristic curve  200   b  in  FIG.  9 ( b ) , the exit pupil distance Po increases as the image height H increases. The optical characteristic curve  200   b  in  FIG.  9 ( b )  shows that, the exit pupil distance is Pob at image height zero, the exit pupil distance gradually increases as the image height H increases, and the exit pupil distance becomes (Pob+Δp 2 ) 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  200   a , is referred to as a negative optical characteristic curve. On the other hand, an optical characteristic curve in which the exit pupil distance Po increases as the image height H increases, such as the optical characteristic curve  200   b , is referred to as a positive optical characteristic curve. 
     The photographing optical system  31  of the interchangeable lens  3  shown in  FIG.  9  ( c )  has an optical characteristic curve that differs, that is, changes depending on the position of the focusing lens  31   b  shown in  FIG.  1   . This photographing optical system  31  exhibits an optical characteristic curve  200   c  when the focusing lens  31   b  is located at a first position and exhibits an optical characteristic curve  200   d  when the focusing lens  31   b  is located at a second position. The first and second positions of the focusing lens  31   b  are arbitrary positions between the infinity position and the closest position, of the focusing lens  31   b , including the infinity position and the closest position. The infinity position of the focusing lens  31   b  is a position where the subject at the infinity distance is in focus, and the closest position is a position where the subject at the closest distance is in focus. 
     In  FIG.  9 ( c ) , the optical characteristic curve  200   c  represents the optical characteristics of the photographing optical system  31  in a case where the focusing lens  31   b  is at the first position. The optical characteristic curve  200   c  shows that, the exit pupil distance is Poc at image height zero, the exit pupil distance gradually decreases as the image height H increases, and the exit pupil distance becomes (Poc−Δp 3 ) at the maximum image height Hmax. The optical characteristic curve  200   d  represents the optical characteristics of the photographing optical system  31  in a case where the focusing lens  31   b  is at the second position. The optical characteristic curve  200   d  shows that, the exit pupil distance is Pod at image height zero, the exit pupil distance gradually increases as the image height H increases, and the exit pupil distance becomes (Pod+Δp 4 ) at the maximum image height Hmax. 
     In  FIG.  9 ( c ) , the optical characteristic curve  200   c  in the case where the focusing lens  31   b  is at the first position is shown as the negative optical characteristic curve, and the optical characteristic curve  200   d  in the case where the focusing lens  31   b  is at the second position is shown as the positive optical characteristic curve. However, there can also be an interchangeable lens  3  having an optical characteristic in which both the optical characteristic curve  200   c  and the optical characteristic curve  200   d  are both positive or negative. 
     The photographing optical system  31  of the interchangeable lens  3  shown in  FIG.  9 ( d )  has an optical characteristic curve that differs, that is, changes depending on the focal length of the zoom lens (the position of the zoom lens  31   a  in  FIG.  1   ). This photographing optical system  31  exhibits an optical characteristic curve  200   e  in a case where both the focal length is f 1  and exhibits an optical characteristic curve  200   f  in a case where the focal length is f 2 . 
     In  FIG.  9 ( d ) , the optical characteristic curve  200   e  represents the optical characteristics of the photographing optical system  31  in a case where the focal length is f 1 . The optical characteristic curve  200   e  shows that, the exit pupil distance is Poe at image height zero, the exit pupil distance gradually decreases as the image height H increases, and the exit pupil distance becomes (Poe−Δp 5 ) at the maximum image height Hmax. The optical characteristic curve  200   f  represents the optical characteristics of the photographing optical system  31  in a case where the focal length is f 2 . The optical characteristic curve  200   f  shows that, the exit pupil distance is Pof at image height zero, the exit pupil distance gradually increases as the image height H increases, and the exit pupil distance becomes (Pof+Δp 6 ) at the maximum image height Hmax. 
     In  FIG.  9 ( d ) , the optical characteristic curve  200   e  in the case where the focal length is f 1  is shown as the negative optical characteristic curve, and the optical characteristic curve  200   f  in the case where the focal length is f 2  is shown as the positive optical characteristic curve. However, there can also be an interchangeable lens  3  having an optical characteristic in which both the optical characteristic curve  200   e  and the optical characteristic curve  200   f  are both positive or negative. 
     It is to be noted that the exit pupil distance Po at the image height H in the above description is the distance of the exit pupil of the photographing optical system  31  from view of the image height H of the imaging surface  22   a . In other words, the exit pupil distance Po at the image height H is the exit pupil distance (distance from the imaging surface  22   a ) of the photographing optical system  31  through which the light flux that passes through the photographing optical system  31  and is incident on the position in correspondence with the image height H of the imaging surface  22   a.    
       FIG.  10    is a diagram showing the relationship between the image height H and the exit pupil distance Po. In  FIG.  10   , to the AF pixel (in  FIG.  10   , the microlens  44  is shown on behalf of the AF pixel) located at the center position 0 (image height zero) of the imaging surface  22   a , the light flux that has passed through the exit pupil EPa (exit pupil distance Poa) of the imaging optical system  31  is incident. 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. 
     Further, a light flux that has passed through the exit pupil EPb of the photographing optical system  31  is incident on the AF pixel (in  FIG.  10   , the microlens  44  is shown as representative of the AF pixel) located at the image height He. The exit pupil distance (Poa−Δp) of the exit pupil EPb is the exit pupil distance of the exit pupil EPb for the image height H. 
     Here, the relationship between the optical characteristics of each interchangeable lens  3  and the above formula (1) will be described. Po (H)=h 4 ×H 4 +h 2 ×H 2 +Co of the above formula (1) is a function to approximate the optical characteristic curves  200   a ,  200   b ,  200   c ,  200   d ,  200   e ,  200   f  and the like shown in  FIG.  9  ( a )  through  FIG.  9  ( d ) . The optical characteristic curve  200   a  shown in  FIG.  9 ( a )  is approximated by the calculation of the formula (1); by setting the constant term Co to the exit pupil distance Poa at the image height zero of  FIG.  9 ( a ) , and by setting the coefficients h 4  and h 2  to the coefficients h 4   a  and h 2   a  corresponding to the curve of the optical characteristic curve  200   a . As described above, the interchangeable lens  3  having the optical characteristics of  FIG.  9 ( a )  stores the constant term Poa and the coefficients h 4   a  and h 2   a  in the lens memory  33  as lens information. 
     Similarly, with respect to the interchangeable lens  3  having the optical characteristics of  FIG.  9 ( b ) , the constant terms Pob and the coefficients h 4   b  and h 2   b , that determines a calculation of the formula (1) that approximates the optical characteristics curve  200   b  are stored in the lens memory  33  as the lens information. 
     Further, the interchangeable lens  3  shown in  FIG.  9 ( c )  has optical characteristics in which the optical characteristic curve changes depending on the position of the focusing lens  31   b . The interchangeable lens  3  stores in the lens memory  33  the constant terms Co and the coefficients h 4  and h 2  for the calculation of the formula (1) that approximate the optical characteristic curve for each position of the focusing lens  31   b . The range in which the focusing lens  31   b  moves (between the infinity position and the closest position) is divided into a plurality of zones Z 1  to Zn, and one optical characteristic curve representing the zone (range) is determined for each section Z 1  to Zn. For example, the optical characteristic curve in a case where the focusing lens  31   b  is located at the intermediate position of one zone is defined as the optical characteristic curve representing that zone. 
     The optical characteristic curve representing the zone Zk is defined as the optical characteristic curve Zk (k=1, 2, . . . n). For the calculation of the formula (1) that approximates the optical characteristic curve Z 1  representing the zone Z 1 , the constant term Co and the coefficients h 4  and h 2  are set to Poz 1 , h 4   z   1  and h 2   z   1 . For the calculation of the formula (1) that approximates the optical characteristic curve Z 2  representing the zone Z 2 , the constant term Co and the coefficients h 4  and h 2  are set to Poz 2 , h 4   z   2  and h 2   z   2 . Similarly, for the calculation of the formula (1) that approximates the optical characteristic curve Zn representing the zone Zn, the constant term Co and the coefficients h 4  and h 2  are set to Pozn, h 4   zn  and h 2   zn .  FIG.  11    shows these zones and the constant terms and coefficients for the calculation for approximating the optical characteristic curves representing these zones. The interchangeable lens  3  stores the zones Z 1  to Zn, the constant terms Poz 1  to Pozn, and the coefficients h 4   z   1  to h 4   zn  and h 2   z   1  to h 2   zn  shown in  FIG.  11    in the lens memory  33 , as lens information. 
     The interchangeable lens  3  shown 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 terms Co and the coefficients h 4  and h 2  for the calculation of the formula (1) that approximate the optical characteristic curve for each focal length. The distance between the maximum focal length and the minimum focal length of the zoom lens set by the zoom lens  31   a  shown in  FIG.  1    is divided into a plurality of zones W 1  to Wn, and one optical characteristic curve representing the zone is determined for each zone W 1  to Wn. For example, an optical characteristic curve at a focal length in the middle of one zone is defined as an optical characteristic curve representing that zone. 
     The optical characteristic curve representing the zone Wk is defined as the optical characteristic curve Wk (k=1, 2, . . . n). For the calculation of the formula (1) that approximates the optical characteristic curve W 1  representing the zone W 1 , the constant term Co and the coefficients h 4  and h 2  are set to Pow 1 , h 4   w   1  and h 2   w   1 . For the calculation of the formula (1) that approximates the optical characteristic curve W 2  representing the zone W 2 , the constant term Co and the coefficients h 4  and h 2  are set to Pow 2 , h 4   w   2  and h 2   w   2 . Similarly, for the calculation of the formula (1) that approximates the optical characteristic curve Wn representing the zone Wn, the constant term Co and the coefficients h 4  and h 2  are set to Pown, h 4   wn  and h 2   wn .  FIG.  12    shows these zones and the constant terms and coefficients for the calculation for approximating the optical characteristic curves representing these zones. The interchangeable lens  3  stores the zones W 1  to Wn, the constant terms Pow 1  to Pown, the coefficients h 4   w   1  to h 4   wn , and h 2   w   1  to h 2   wn  in the lens memory  33  shown in  FIG.  12   , as lens information. 
     Although the interchangeable lens  3  of  FIG.  9 ( d )  is a zoom lens having optical characteristics in which the optical characteristic curve changes depending on the focal length, there is another zoom lens having optical characteristics in which the optical characteristic curve changes depending on the position of the focusing lens  31   b  in addition that the optical characteristic curve changes depending on the focal length. That is, the optical characteristic curve of the another zoom lens changes depending on both the position (focal length) of the zoom lens  31   a  and the position of the focusing lens  31   b.    
     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 R 1  to R 3  shown in  FIG.  8    will be described.  FIG.  13    shows; the first and second threshold values Th 1  and Th 2  regarding the exit pupil distance shown in  FIG.  8   , the first to third exit pupil distance ranges R 1  to R 3 , and the optical characteristic curve exemplified in  FIG.  9   . As shown in  FIG.  13   , in the entire optical characteristic curve  200   g , 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 R 2 . In a case where the interchangeable lens  3  having such an optical characteristic curve  200   g  is attached to the camera body  2 , even if the region setting unit  211  set the focus detection area  100  for any image height H, the pixel selection unit  213  selects the second AF pixel pair. 
     With respect to the optical characteristic curve  200   h , the part corresponding to the exit pupil distance from the image height zero to the image height Hf belongs to the second exit pupil distance range R 2 , and the part corresponding to the exit pupil distance from the image height Hf to the maximum image height Hmax belongs to the first exit pupil distance range R 1 . In a case where the area setting unit  211  sets the focus detection area  100  at which the image height is Hf or less, the pixel selection unit  213  selects the second AF pixel pair. Further, in a case where the area setting unit  211  sets the focus detection area  100  at which the image height is larger than Hf, the pixel selection unit  213  selects the first AF pixel pair. 
     With respect to the optical characteristic curve  200   i , the part corresponding to the exit pupil distance from the image height zero to the image height Hg belongs to the third exit pupil distance range R 3 , and the part corresponding to the exit pupil distance from the image height Hg to the maximum image height Hmax belongs to the second exit pupil distance range R 2 . In a case where the area setting unit  211  sets the focus detection area  100  at which the image height is Hg or less, the pixel selection unit  213  selects the third AF pixel pair. Further, in a case where the area setting unit  211  sets the focus detection area  100  at which the image height is larger than Hg, the pixel selection unit  213  selects the second AF pixel pair. 
     It is to be noted, as described above, in a case where a plurality of focus detection areas  100  are set by the area setting unit  211 , the pixel selection unit  213  selects the same type of AF pixel pairs for all selected focus detection area  100 . In such case, the pixel selection unit  213  selects an AF pixel pair based on the position of the focus detection area  100  farthest from the optical axis OA 1  of the photographing optical system  31  (the image height H is the highest) among the plurality of selected focus detection areas  100 . In the present embodiment, the pixel selection unit  213  selects AF pixel pairs as described above based on the image height of the focus detection area  100  having the highest image height among the plurality of selected focus detection areas  100 . The pixel selection unit  213  selects AF pixel pairs of the same type as the selected AF pixel pair for the focus detection area  100  of the highest image height among the selected plurality of focus detection areas  100  with respect also to other focus detection areas  100 . 
     The circuit configuration and operation of the image sensor  22  according to the first embodiment will be described with reference to  FIG.  14    and  FIG.  15   .  FIG.  14    is a diagram showing a configuration of a pixel of the image sensor  22  according to the first embodiment. The pixel  13  includes the photoelectric conversion unit  42 , a transfer unit  52 , a reset unit  53 , a floating diffusion (FD)  54 , an amplification unit  55 , and a selection unit  56 . The photoelectric conversion unit  42  is a photodiode PD, which converts incident light into electric charge and stores the photoelectrically converted electric charges. 
     The transfer unit  52  is configured with a transistor M 1  controlled by a signal TX, and transfers the charge photoelectrically converted by the photoelectric conversion unit  42  to the FD  54 . The transistor M 1  is a transfer transistor. A capacitor C of the FD  54  accumulates (retains) the charge transferred to the FD  54 . 
     The amplification unit  55  outputs a signal corresponding to the electric charge stored in the capacitor C of the FD  54 . The amplification unit  55  and the selection unit  56  configure an output unit that generates and outputs a signal based on the electric charge generated by the photoelectric conversion unit  42 . 
     The reset unit  53  is configured with a transistor M 2  controlled by a signal RST, discharges the electric charge accumulated in the FD  54 , and resets the voltage of the FD  54 . The transistor M 2  is a reset transistor. 
     The selection unit  56  is configured with a transistor M 4  controlled by a signal SEL, and electrically connects or disconnects the amplification unit  55  and a vertical signal line  60 . The transistor M 4  is a selection transistor. 
     As described above, the charge photoelectrically converted by the photoelectric conversion unit  42  is transferred to the FD  54  by the transfer unit  52 . Then, a signal corresponding to the electric charge transferred to the FD  54  is output to the vertical signal line  60 . A pixel signal is an analog signal generated based on the electric charge photoelectrically converted by the photoelectric conversion unit  42 . The signal output from the imaging pixel  13  is converted into a digital signal and then output to the body control unit  210 . 
     It is to be noted, in the present embodiment, the circuit configurations of the first AF pixels  11  ( 11   a  to  11   c ) and the second AF pixels  12  ( 12   a  to  12   c ) are the same as the circuit configuration of the imaging pixel  13 . The signals output from the first AF pixel  11  and the second AF pixel  12  are converted into digital signals and then output to the body control unit  210  as the pair of signals (the first and second signals Sig 1  and Sig 2 ) used for focus detection. 
       FIG.  15    is a diagram showing a configuration example of the image sensor according to the first embodiment. The image sensor  22  includes a plurality of imaging pixels  13 , a first AF pixel  11  and a second AF pixel  12 , a vertical control unit  70 , and a plurality of column circuit units  80 . It is to be noted, in  FIG.  15   , for simplification of the description, only 128 pixels of 8 pixels in the row direction (±X direction)×16 pixels in the column direction (±Y direction) are shown. In  FIG.  15   , the pixel in the upper left corner is defined as the imaging pixel  13  (1,1) in the 1st row and the 1st column, and the imaging pixel in the lower right corner is defined as the imaging pixel  13  (16, 8) in the 16th row and the 8th column. The image sensor  22  is provided with a plurality of vertical signal lines  60  (vertical signal lines  60   a  to  60   h ). The plurality of vertical signal lines  60  are connected to each of the pixel columns (1st column to 8th column), which is a column of a plurality of pixels arranged in the column direction, that is, in the vertical direction. To each of the vertical signal lines  60   a ,  60   c ,  60   e ,  60   g , a plurality of imaging pixels  13  arranged in each of columns are connected, and the vertical signal lines  60   a ,  60   c ,  60   e ,  60   g  respectively output signals of the connected imaging pixels  13 . To each of the vertical signal lines  60   b ,  60   d ,  60   f ,  60   h , a plurality of imaging pixels  13 , a plurality of the first AF pixels and a plurality of the second AF pixels arranged in each of columns are connected, and the vertical signal lines  60   b ,  60   d ,  60   f ,  60   h  respectively output signals of the connected imaging pixels  13 , the first AF pixels and the second AF pixels. 
     The vertical control unit  70  is provided so as to be common to a plurality of pixel columns. The vertical control unit  70  supplies the signal TX, the signal RST, and the signal SEL shown in  FIG.  14    to each pixel to control the operation of each pixel. The vertical control unit  70  supplies a signal to the gate of each transistor of the pixel, and turns the transistor on (connected state, conducting state, short-circuited state) or off state (disconnected state, non-conducting state, open state, break-circuit state). 
     The column circuit unit  80  includes an analog/digital conversion unit (AD conversion unit), and converts an analog signal input from each pixel via the vertical signal line  60  into a digital signal and outputs the converted signal. The pixel signal converted into a digital signal is input to a signal processing unit (not shown), and after signal processing such as correlation double sampling and processing for correcting the signal amount, and output to the body control unit  210  of the camera  1 . 
     The readout unit  214  of the camera  1 , by controlling the vertical control unit  70 , performs the first readout mode in which all pixel rows are sequentially selected and signal of each pixel is readout, and the second readout mode in which signals from the AF pixel row and from the imaging pixel row are separately read out. 
     In a case the first readout mode has set by the readout unit  214 , the vertical control unit  70  sequentially selecting pixel row and makes each pixel output signal. In  FIG.  15   , the vertical control unit  70  sequentially selects the imaging pixel rows  401 ,  402 , the AF pixel rows  403   a ,  404   a ,  403   b , and  404   b  from the 1st row toward the 16th row. Further, the vertical control unit  70  makes each pixel of the selected imaging pixel row or AF pixel row output signal to the vertical signal line  60 . The readout unit  214  reads out the signal output to the vertical signal line  60 . An example of a signal readout method in the first readout mode will be described below. 
     First, the vertical control unit  70  turns to on state the selection units  56  of the R pixel  13  (1,1) through the G pixel  13  (1,8), which are the pixels in the first imaging pixel row  401  of the 1st row. Further, the vertical control unit  70  makes the selection units  56  of pixels in the rows other than the 1st row turn to off state. Thereby, each signal of the R pixel  13  (1,1) through the G pixel  13  (1,8) in the 1st row is output, via the selection unit  56 , to each of the signal lines  60   a  to  60   h  which are connected. The readout unit  214  reads out the signals of the R pixel  13  (1,1) through the G pixel  13  (1,8) having been output to the vertical signal lines  60 . 
     Next, the vertical control unit  70  turns to on state the selection units  56  of the G pixel  13  (2,1) through the first AF pixel  11   a  (2,8), which are the pixels in the first AF pixel row  403   a  of the 2nd row. Further, the vertical control unit  70  makes the selection units  56  of pixels in the rows other than the 2nd row turn to off state. Thereby, each signal of the G pixel  13  (2,1) through the first AF pixel  11   a  (2,8) in the 2nd row is output to each of the signal lines  60   a  to  60   h . The readout unit  214  reads out the signals of the G pixel  13  (2,1) through the first AF pixel  11   a  (2,8), in the 2nd row, having been output to the vertical signal lines  60 . 
     Similarly, the vertical control unit  70  selects the 3rd and subsequent pixel rows (the first imaging pixel row  401 , the second imaging pixel row  402 , the first AF pixel row  403 , the second AF pixel row  404 ) in the order of the 3rd row, the 4th row, the 5th row, and the 6th row. Further, the vertical control unit  70  makes each pixel of the selected imaging pixel row or AF pixel row output signal to the vertical signal line  60 . The readout unit  214  reads out the signal output to the vertical signal line  60 . 
     As described above, in the first readout mode, the readout unit  214  reads out a signal from each pixel of all the pixel rows. The signal having read out from each pixel is output to the body control unit  210  after being subjected to signal processing by the column circuit unit  80  or the like. 
     In a case the second readout mode is set by the readout unit  214 , the vertical control unit  70  separately performs of outputting of the signal of each pixel in the AF pixel row to the vertical signal lines  60  and outputting of the signal of each pixel in the imaging pixel row to the vertical signal lines  60 . In the present embodiment, the vertical control unit  70  first sequentially selects only the AF pixel row and let each pixel of the selected AF pixel row output a signal to the vertical signal lines  60 . Then, the vertical control unit  70  sequentially selects the imaging pixel row and let each pixel of the selected imaging pixel row output a signal to the vertical signal lines  60 . The readout unit  214  first reads out only the signal output to the vertical signal lines  60  from each pixel of the AF pixel row, and then reads out the signal output to the vertical signal lines  60  from each pixel of the imaging pixel row. 
     An example of a signal readout method in the second readout mode will be described below. It is to be noted, the vertical control unit  70  selects the AF pixel row in which the AF pixel pair selected by the pixel selection unit  213  is arranged, in one (or a plurality of) focus detection areas  100  set by the area setting unit  211 . In the example shown below, it is assumed that the first AF pixel pair is selected by the pixel selection unit  213  based on the exit pupil distance of the photographing optical system  31 . 
     First, the vertical control unit  70  turns to on state the selection units  56  of the G pixel  13  (2,1) through the first AF pixel  11   a  (2,8) which constitute the first AF pixel row  403   a  of the 2nd row shown in  FIG.  15   . Further, the vertical control unit  70  makes the selection units  56  of pixels in the rows other than the 2nd row turn to off state. Thereby, each signal of the G pixel  13  (2,1) through the first AF pixel  11   a  (2,8) is output, via the selection unit  56 , to each of the signal lines  60   a  to  60   h  which are connected. The readout unit  214  reads out the signals of the G pixel  13  (2,1) through the first AF pixel  11   a  (2,8) having been output to the vertical signal lines  60 . 
     Next, the vertical control unit  70  turns to on state the selection units  56  of the G pixels  13  (6,1) through the second AF pixel  12   a  (6,8) which constitute the second AF pixel row  404   a  of the 6th row shown in  FIG.  15   . Further, the vertical control unit  70  makes the selection units  56  of pixels in the rows other than the 6th row turn to off state. Thereby, each signal of the G pixel  13  (6,1) through the second AF pixel  12   a  (6,8) is output to each of the signal lines  60   a  to  60   h . The readout unit  214  reads out the signals of the G pixel  13  (6,1) through the second AF pixel  12   a  (6,8) in the 2nd row, having output to the vertical signal lines  60 . 
     Although not shown, a plurality of the first AF pixel rows  403   a  and a plurality of the second AF pixel rows  404   a  are also arranged in after the 16th row. The vertical control unit  70  sequentially selects only the plurality of the first AF pixel rows  403   a  and the plurality of the second AF pixel row  404   a  toward the column direction (+Y direction). The vertical control unit  70  causes each pixel of the selected first AF pixel row  403   a  and the second AF pixel row  404   a  to output a signal to the vertical signal lines  60 . The readout unit  214  reads out signals output to the vertical signal line  60  from the G pixels  13 , the first AF pixels  11   a , and the second AF pixels  12   a . The signals sequentially read from each AF pixel row are output to the body control unit  210  after being subjected to signal processing by the column circuit unit  80  or the like. 
     After reading out the signal from each pixel of the AF pixel row, the vertical control unit  70  sequentially selects the imaging pixel row toward the column direction (+Y direction). The vertical control unit  70  causes each pixel of the selected imaging pixel row to output a signal to the vertical signal line  60 . The readout unit  214  reads out signal output to the vertical signal line  60  from each pixel in the imaging pixel rows. The vertical control unit  70  turns to on state the selection units  56  of the R pixel  13  (1,1) through the G pixel  13  (1,8) which are in the first imaging pixel row  401  of the 1st row shown in  FIG.  15   . Further, the vertical control unit  70  makes the selection units  56  of pixels in the rows other than the 1st row turn to off state. Thereby, each signal of the R pixel  13  (1,1) through the G pixel  13  (1,8) is output to each of the signal lines  60   a  to  60   h . The readout unit  214  reads out the signals of the R pixel  13  (1,1) through the G pixel  13  (1,8) having been output to the vertical signal lines  60 . 
     Next, the vertical control unit  70  turns to on state the selection units  56  of the R pixel  13  (3,1) through the G pixel  13  (3,8) which constitute the first imaging pixel row  401  of the 3rd row shown in  FIG.  15   . Further, the vertical control unit  70  makes the selection units  56  of pixels in the rows other than the 3rd row turn to off state. Thereby, each signal of the R pixel  13  (3,1) through the G pixel  13  (3,8) is output to each of the signal lines  60   a  to  60   h . The readout unit  214  reads out the signals of the R pixel  13  (3,1) through the G pixel  13  (3,8) having been output to the vertical signal lines  60 . 
     Further, the vertical control unit  70  turns to on state the selection units  56  of the G pixel  13  (4,1) through the B pixel  13  (4,8) which constitute the first imaging pixel row  402  of the 4th row shown in  FIG.  15   . Further, the vertical control unit  70  makes the selection units  56  of pixels in the rows other than the 4th row turn to off state. Thereby, each signal of the G pixel  13  (4,1) through the B pixel  13  (4,8) is output to each of the signal lines  60   a  to  60   h . The readout unit  214  reads out the signals of the G pixel  13  (4,1) through the B pixel  13  (4,8) having been output to the vertical signal lines  60 . 
     Similarly, with respect to the 5th row and subsequent rows, the vertical control unit  70  sequentially selects the imaging pixel rows (first imaging pixel row  401 , second imaging pixel row  402 ). The vertical control unit  70  makes each pixel of the selected the first imaging pixel row  401  and the second imaging pixel row  402  output signal to the vertical signal line  60 . The readout unit  214  reads the signals output from the R pixel  13 , the G pixel  13 , and the B pixel  13  to the vertical signal line  60 . The signals sequentially read from each imaging pixel row are output to the body control unit  210  after being subjected to signal processing by the column circuit unit  80  or the like. 
     As described above, in the second readout mode, the readout unit  214  controls the vertical control unit  70  to read out a signal from each pixel in the AF pixel row prior to read out a signal from each pixel in the imaging pixel row. Therefore, the first and second signals Sig 1  and Sig 2  of the AF pixel pair can be read out at high speed, and the time required for focus adjustment can be shortened. Further, since the reading unit  214  reads out the signal of each pixel of the AF pixel row and the signal of each pixel of the imaging pixel row separately, the signal used for the focus detection can be efficiently obtained, and the load for processing signals for AF can be reduced. The camera  1  according to the present embodiment reads out the first and second signals Sig 1  and Sig 2  of the AF pixel pair selected based on the exit pupil distance of the photographing optical system  31  and performs the focus detection process. Thus, highly accurate focus detection can be performed. 
     It is to be noted, in a case the second readout mode is set, the readout unit  214  may read out a signal from each pixel of the imaging pixel row prior to read out a signal from each pixel in the AF pixel row. Even in such a case, since the signal of the AF pixel pair selected based on the exit pupil distance of the photographing optical system  31  is read out and the focus detection process is performed, the focus detection can be performed with high accuracy. Further, since the readout unit  214  reads out the signal of each pixel of the AF pixel row and the signal of each pixel of the imaging pixel row separately, the load for processing signals for AF can be reduced. 
     Moreover, the readout unit  214 , in a case reading out signals from each pixel in the imaging pixel row (the first imaging pixel row  401 , the second imaging pixel row  402 ) in the second readout mode, may read out signals by performing thinning out readout in which pixels of specific row or column are thinned. In a case performing the thinning out reading, the reading unit  214  selects imaging pixels in a specific row or column among all the imaging pixels and reads out a signal from the selected imaging pixel. By controlling the vertical control unit  70 , since the readout unit  214  skips reading the signal of the pixel of a specific row or column, the signal can be read out at high speed. In this case, the signals from the AF pixel row can be read out before reading out the signals from the imaging pixel row in the second read mode, and the signals from the imaging pixel row can be read out at high speed. Therefore, in a case displaying a live view image or shooting a moving image, by performing in the second readout mode, it is possible to perform high-speed focus detection and high-speed shooting. It is to be noted, the readout unit  214  may read out signals from a plurality of imaging pixels through adding the signals. 
     According to the above-described embodiment, the following effects can be obtained. 
     (1) The focus detection device, comprises: the imaging unit (the image sensor  22 ) having the first pixel and the second pixel (the AF pixels) each of which receives light transmitted through the optical system and outputs signal used for focus detection, and the third pixel (the imaging pixel) which receives light transmitted through the optical system and outputs signal used for image generation; the input unit (the body control unit  210 ) to which the information regarding the optical system is input; the selection unit (the image selection unit  213 ) that selects at least one of the first pixel and the second pixel based on the information input to the input unit; the readout unit (the readout unit  214 ) that reads out the signal from at least one of the first pixel and the second pixel based on a selection result of the selection unit at a timing different from the timing of reading out the signal from the third pixel to be read out; and the focus detection unit  215  that performs the focus detection based on at least one of the signals of the first pixel and the second pixel which read out by the readout unit. In the present embodiment, the readout unit  214  reads a signal from each pixel in the AF pixel row prior to read out a signal from each pixel in the imaging pixel row. Therefore, the focus detection device can read out the signals of the AF pixel pair at high speed, and can perform focus adjustment at high speed. Moreover, since the readout unit  214  reads out the signal of each pixel of the AF pixel row and the signal of each pixel of the imaging pixel row separately, the load for processing signals for AF can be reduced. Further, the focus detection unit  215  performs the focus detection process using the signal output from the AF pixel pair selected based on the exit pupil distance of the photographing optical system  31 . Therefore, highly accurate focus detection can be performed. 
     The following variations are also within the scope of the present invention, and one or more of the variations can be combined with the above-described embodiment. 
     Variation 1 
     In the first embodiment, although three reference exit pupils (the first to third exit pupils EP 1  to EP 3 ) were used as the reference exit pupils, it may be two reference exit pupils or four or more reference exit pupils. 
     Variation 2 
     The method of obtaining the exit pupil distance depending on the image height is not limited to the method of obtaining using the above-mentioned formula (1). For example, instead of the formula (1), a calculation formula using the cube of the image height can be used. Further, information (table) showing the relationship between the image height and the exit pupil distance may also be used without using the calculation formula. 
     Variation 3 
     In the first embodiment, an example in which information regarding the exit pupil distance is stored in advance in the lens memory  33  or the like and the information regarding the exit pupil distance is input from the interchangeable lens  3  to the camera body  2  has been described. However, the information regarding the exit pupil distance may be input to the camera body  2  from other than the interchangeable lens  3 . For example, the body memory  23  may store the information regarding the exit pupil distance in advance, and the body control unit  210  may acquire the information regarding the exit pupil distance from the body memory  23 . Further, the camera body  2  may acquire the information regarding the exit pupil distance from a storage medium or may acquire the information regarding the exit pupil distance from an external device by wired communication or wireless communication. It is to be noted, the information regarding the exit pupil distance may be information regarding the exit pupil distance corresponding to one image height. 
     Variation 4 
     In the first embodiment, the parameters (h 4 ) and (h 2 ) and the constant term Co, used for calculating the exit pupil distance Po (H) have been described as examples of the information regarding the exit pupil distance. However, the camera body  2  may acquire the value Po (H) itself of the exit pupil distance according to an image height, from the interchangeable lens  3 , the storage medium, or the like as the information regarding the exit pupil distance. 
     Variation 5 
     In the above-described embodiment, an example in which first to third AF pixel pairs having different deviation amounts are arranged on the image sensor  22  as a plurality of types of AF pixel pairs has been described. However, a plurality of types of AF pixel pairs having different arrangement positions of the light-shielding portions between the color filter  51  and the photoelectric conversion unit  42  may be arranged on the image sensor  22 .  FIG.  16    is a diagram showing a configuration example of a AF pixel of the image sensor  22  according to the present variation. In the figure, the same reference signs are assigned to the same or corresponding parts as those in the above-described embodiment. 
     The light-shielding portion  43 L of the first AF pixel  11   a  is provided, between the color filter  51  and the photoelectric conversion unit  42 , with a predetermined distance h 1  from the photoelectric conversion unit  42 . The light-shielding portion  43 L of the first AF pixel  11   b  is provided, between the color filter  51  and the photoelectric conversion unit  42 , with a predetermined distance h 2  from the photoelectric conversion unit  42 . The light-shielding portion  43 L of the first AF pixel  11   c  is provided, between the color filter  51  and the photoelectric conversion unit  42 , with a predetermined distance h 3  from the photoelectric conversion unit  42 . The distance h 2  is smaller than the distance h 1  and larger than the distance h 3 . That is, h 1 &gt;h 2 &gt;h 3 . As described above, arranged positions of the light-shielding portions  43 L are different in the first AF pixels  11   a ,  11   b , and  11   c  to each other. Further, in the second AF pixels  12   a ,  12   b ,  12   c  constituting each AF pixel pair, the arrangement positions of the light-shielding portions  43 R are different from each other. Thereby, the first to third AF pixel pairs can perform pupil division corresponding to different incident angles, as in the case of the above-described embodiment. 
     Variation 6 
     In the first embodiment, an example in which one photoelectric conversion unit is arranged in one pixel has been described, however, a configuration in which two or more photoelectric conversion units are included per pixel may be adopted. 
     Variation 7 
       FIG.  17    is a diagram showing a configuration example of a AF pixel of the image sensor  22  according to the present variation. As an example,  FIG.  17    shows a cross-sectional view of a part of three types of AF pixel pairs in the focus detection area  100   c  shown in  FIG.  2   . In the figure, the same reference signs are assigned to the same or corresponding parts as those in the above-described embodiment. Each of the three types of AF pixels shown in  FIG.  17  ( a )  to  FIG.  17  ( c )  includes a microlens  44 , and a first and second photoelectric conversion units  42   a  and  42   b  each of which photoelectrically convert the light transmitted through the microlens  44 . In the present variation, the light receiving areas, of a first photoelectric conversion units  42   a  and a second photoelectric conversion unit  42   b  are different from each other in the first to third AF pixel pair. In this case as well, the first to third AF pixel pairs can perform pupil division corresponding to different incident angles, as in the case of the above-described embodiment. 
     Variation 8 
     The pixel selection unit  213  may configure to select a plurality of types of AF pixel pairs. In this case, the focus detection unit  215  may calculate a plurality of defocus amounts from selected plurality of types of AF pixel pairs, and the movement amount of the focusing lens  31   b  may be calculated based on the average value of the defocus amounts. For example, the moving amount of the focusing lens  31   b  may be determined based on the average value of, the defocus amount calculated using the first and second signals Sig 1  and Sig 2  of the first AF pixel pair and the defocus amount calculated using the first and second signals Sig 1  and Sig 2  of the second AF pixel pair. 
     Variation 9 
     In the above-described embodiment, the case where the primary color system (RGB) color filter is used for the image sensor  22  has been described, but the complementary color system (CMY) color filter may be used. 
     Variation 10 
     The imaging device described in the above-described embodiment and variations may be applied to a camera, a smartphone, a tablet, a camera built in a PC, an in-vehicle camera, a camera mounted on an unmanned aerial vehicle (drone, radio-controlled model, etc.), etc. 
     Although various embodiments and variations have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included within the scope of the present invention. 
     The disclosure of the following priority application is herein incorporated by reference: Japanese Patent Application No. 2018-137274 filed Jul. 20, 2018. 
     REFERENCE SIGNS LIST 
     
       
         
           
               
               
               
               
               
               
             
               
                   
               
             
            
               
                 1 
                 Imaging Device, 
                 2 
                 Camera Body, 
                 3 
                 Interchangeable Lens, 
               
               
                 11 
                 AF pixel, 
                 12 
                 AF pixel, 
                 13 
                 Imaging Pixel, 
               
               
                 22 
                 Image Sensor, 
                 31 
                 Photographing Optical System, 
               
               
                 32 
                 Lens Control Unit, 
                 42 
                 Photoelectric Conversion Unit, 
               
               
                 210 
                 Body Control Unit, 
                 211 
                 Area Setting Unit, 
               
               
                 212 
                 Distance Calculation Unit, 
                 213 
                 Pixel Selection Unit, 
               
               
                 214 
                 Readout Unit, 
                 215 
                 Focus Detection Unit, 
               
               
                 216 
                 Image Data Generation Unit.