JP2018191304A - Imaging element and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device that enables focus detection with suppressed influence of vignetting, and can capture an image of high quality.SOLUTION: An imaging device according to the present invention comprises: an imaging element in which a plurality of pixels corresponding to each of a plurality of pixel groups is arranged on an imaging plane, a pair of photoelectric conversion units receiving a light flux passing through a pair of regions in a pupil plane located at range-finding pupil distance corresponding to each group from the imaging plane is included in each pixel, and which outputs a pair of electric signals corresponding to light reception by the pair of the photoelectric conversion units; exit pupil distance information acquisition means that acquires information on exit pupil distance of an optical system; selection means that selects one group corresponding to one range-finding pupil distance close to the exit pupil distance; focus detection means that detects a focus adjustment state of the optical system by a pupil division phase difference detection method on the basis of the pair of electric signals; and image creation means that creates an image on the basis of an addition signal having the pair of electric signals mutually added.SELECTED DRAWING: Figure 14

Description

  The present invention relates to an imaging element and an imaging apparatus.

  An imaging element in which focus detection pixels that receive a light beam passing through a pair of regions of the exit pupil of the optical system are arranged on a part of the imaging surface is disposed on the planned focal plane of the optical system, whereby the pair of light beams is A pair of image signals corresponding to the pair of images to be formed are output from the focus detection pixels, and the amount of image shift (spatial phase difference) between the pair of image signals is detected to adjust the focus adjustment state of the optical system. There is known an imaging apparatus that detects the above.

  Furthermore, it has a plurality of types of focus detection pixels optimized for different exit pupil distances, and selects one type of focus detection pixel according to the exit pupil distance of the optical system. An imaging apparatus that performs focus detection based on a signal is known (see Patent Document 1).

  In the prior art disclosed in Patent Document 1, in order to receive a pair of light beams that pass through the exit pupil of the optical system for focus detection, a pair of pixels that receive one light beam and a pixel that receives the other light beam. The focus detection pixels are used. The pair of focus detection pixels have the same color filter. Imaging pixels are used for imaging. The imaging pixel has a filter arranged in accordance with a predetermined color arrangement, and receives all light beams passing through the exit pupil.

JP 2009-204987 A

  However, in the prior art disclosed in Patent Document 1 described above, the size and color of the light beams received by the focus detection pixels and the imaging pixels are different from each other. Therefore, in order to obtain an image having no pixel abnormality, an image pickup signal at the position of the focus detection pixel is interpolated (pixel signal interpolation) using signals of pixels around the focus detection pixel. Need to ask. However, due to the adverse effects of using signals from surrounding pixels, it has been difficult to maintain image quality due to a decrease in resolution or generation of false colors.

  In particular, in an imaging device having a plurality of types of focus detection pixels as disclosed in Patent Document 1, when selecting one type of focus detection pixels according to the exit pupil distance of the optical system, There was a problem. Since a plurality of types of focus detection pixels are arranged on the image sensor, the number of focus detection pixels is increased as compared with the case where only one type of focus detection pixels is arranged. At the same time, it is necessary to arrange a plurality of types of focus detection pixels in close proximity so that the focus detection position on the shooting screen does not change greatly in accordance with the selection of the focus detection pixel type. Become. However, in such a configuration, the above-described pixel signal interpolation error is recognized more remarkably.

The image sensor according to the first aspect of the present invention is an image sensor having a first pixel and a second pixel, and the first pixel is at a predetermined distance from a line passing through the center of the image sensor in the first direction. A first microlens and a first photoelectric conversion unit that photoelectrically convert light transmitted through the first microlens and a first distance from the optical axis of the first microlens in the first direction; And a separation unit that separates the first photoelectric conversion unit and the second photoelectric conversion unit, wherein the second pixel is located at a predetermined distance from a line passing through the center of the imaging element in the first direction. The third and fourth photoelectric conversion units that are disposed and photoelectrically convert the light transmitted through the second microlens and the second microlens, and the first distance in the first direction from the optical axis of the second microlens. Set at a different second distance It is, and a separation unit separating the said fourth photoelectric conversion unit and the third photoelectric conversion unit.
An imaging device according to a second aspect of the present invention includes a first microlens, first and second photoelectric conversion units that photoelectrically convert light transmitted through the first microlens, and an optical axis of the first microlens. A first unit provided at a first distance in one direction, having a separation unit that separates the first photoelectric conversion unit and the second photoelectric conversion unit, and disposed at a predetermined image height position in the first direction; A pixel, a second microlens, third and fourth photoelectric conversion units that photoelectrically convert light transmitted through the second microlens, and the first distance in the first direction from the optical axis of the second microlens. A second pixel that is provided at a different second distance, has a separation unit that separates the third photoelectric conversion unit and the fourth photoelectric conversion unit, and is disposed at the predetermined image height position in the first direction. And comprising.
The imaging device according to the third aspect of the present invention outputs the signal output from the first pixel and the second pixel based on the imaging element according to the first or second aspect and the pupil distance of the optical system. A detecting unit that selects at least one of the signals to detect the focus of the optical system.

  According to the present invention, it is possible to detect a focus while suppressing the influence of injuries and to obtain a high-quality image.

It is a cross-sectional view which shows the structure of the digital still camera of 1st Embodiment. It is a front view of the imaging | photography screen prescribed | regulated on the imaging surface of an image pick-up element. It is a front view which shows the detailed structure of an image pick-up element. It is sectional drawing of a pixel. It is sectional drawing of a pixel. It is a figure which shows the relationship of a pair of light beam which arrives at each focus detection area from a pair of ranging pupil. It is a figure which shows the relationship of a pair of light beam which arrives at each focus detection area from a pair of ranging pupil. It is the figure which showed the relationship between the light beam which the pixel which belongs to each group light-receives, and each ranging pupil distance. It is a circuit structure conceptual diagram of an image sensor. It is a detailed circuit diagram of each pixel. It is a figure which shows the detailed circuit structure for every row | line | column of a CDS circuit. It is an operation | movement timing chart of an image pick-up element. It is an operation | movement timing chart of an image pick-up element. It is a flowchart which shows the imaging operation of a digital still camera. It is a figure for demonstrating which pixel is selected among the pixels which belong to three groups according to an exit pupil distance. It is a front view of the imaging | photography screen prescribed | regulated on the imaging surface of an image pick-up element. It is a front view which shows the detailed structure of an image pick-up element. It is the front view which showed the range of the light beam which injects into a pair of photoelectric conversion part of a pixel. It is the figure which showed the relationship between F value and a correction coefficient. It is the front view which showed the range of the light beam which injects into a pair of photoelectric conversion part of a pixel. It is the figure which showed the relationship between F value and a correction coefficient.

--- First embodiment ---
A lens interchangeable digital still camera will be described as an example of the imaging apparatus according to the first embodiment. FIG. 1 is a cross-sectional view illustrating a configuration of a digital still camera 201 according to the first embodiment. A digital still camera 201 according to the present embodiment includes an interchangeable lens 202 and a camera body 203, and the interchangeable lens 202 is attached to the camera body 203 via a mount unit 204. An interchangeable lens 202 having various photographing optical systems can be attached to the camera body 203 via a mount unit 204.

  The interchangeable lens 202 includes a lens 209, a zooming lens 208, a focusing lens 210, a diaphragm 211, a lens drive control device 206, and the like. The lens drive control device 206 includes a microcomputer (not shown), a memory, a drive control circuit, and the like. The lens drive control device 206 performs drive control for adjusting the focus of the focusing lens 210 and adjusting the aperture diameter of the aperture 211, and detecting the states of the zooming lens 208, the focusing lens 210, and the aperture 211, and the like. Further, lens information is transmitted and camera information (defocus amount, aperture value, etc.) is received by communication with a body drive control device 214 described later. The aperture 211 forms an aperture having a variable aperture diameter at the center of the optical axis in order to adjust the amount of light and the amount of blur.

  The camera body 203 includes an image sensor 212, a body drive control device 214, a liquid crystal display element drive circuit 215, a liquid crystal display element 216, an eyepiece lens 217, a memory card 219, and the like. Pixels are arranged two-dimensionally on the image sensor 212. Details of the image sensor 212 will be described later.

  The body drive control device 214 includes a microcomputer, a memory, a drive control circuit, and the like. The body drive control device 214 repeatedly performs drive control of the image sensor 212, readout of the pixel signal, focus detection calculation based on the pixel signal, and focus adjustment of the interchangeable lens 202, and generation processing on image data based on the pixel signal Also performs recording, camera operation control, etc. The body drive control device 214 communicates with the lens drive control device 206 via the electrical contact 213 to receive lens information and send camera information.

  The liquid crystal display element 216 functions as an electric view finder (EVF). The liquid crystal display element driving circuit 215 displays a through image on the liquid crystal display element 216 based on the image data read from the image sensor 212, and the photographer can observe the through image through the eyepiece 217. The memory card 219 is an image storage that stores image data captured by the image sensor 212.

  A subject image is formed on the imaging surface of the imaging element 212 by the light beam that has passed through the interchangeable lens 202. This subject image is photoelectrically converted by the image sensor 212, and the pixel output signal is sent to the body drive control device 214.

  The body drive control device 214 has an imaging control function and a focus detection control function, as will be described later with reference to FIG. The body drive control device 214 calculates the defocus amount based on the output signal (focus detection signal) of the pixel of the image sensor 212 and sends this defocus amount to the lens drive control device 206. In addition, the body drive control device 214 processes the output signal (image pickup signal) of the pixel of the image pickup device 212 to generate image data, stores the image data in the memory card 219, and sends it to the liquid crystal display device drive circuit 215 to display the through image. Is displayed on the liquid crystal display element 216. Further, the body drive control device 214 sends aperture control information to the lens drive control device 206 to control the aperture of the aperture 211.

  The lens drive controller 206 updates the lens information according to the focusing state, zooming state, aperture setting state, aperture opening F value, and the like. Specifically, the positions of the zooming lens 208 and the focusing lens 210 and the aperture value of the aperture 211 are detected, and lens information is calculated according to these lens positions and aperture values, or prepared in advance. Lens information (F value, exit pupil distance information, etc.) corresponding to the lens position and aperture value is selected from the look-up table.

  The lens drive control device 206 calculates a lens drive amount based on the received defocus amount, and drives the focusing lens 210 to the in-focus position according to the lens drive amount. Further, the lens drive control device 206 drives the diaphragm 211 in accordance with the received diaphragm value.

  The focus detection area selection operation member 220 is used by the user to designate a position for focus detection on the photographing screen.

  FIG. 2 is a front view of the imaging screen 100 defined on the imaging surface of the imaging device 212. Pixels to be described later are two-dimensionally arranged on the imaging screen 100 in a rectangular area. The center on the rectangular imaging screen 100 is located on the optical axis of the interchangeable lens 202, and the horizontal direction centering on the position is the X direction and the vertical direction is the Y direction. The center 191 of the photographing screen 100 coincides with the optical axis of the photographing optical system.

  FIG. 3 is a front view showing a detailed configuration of the image sensor 212 on the photographing screen 100, and shows details of the pixel arrangement when a partial region 180 of FIG. 2 is enlarged. As shown in FIG. 3, the image sensor 212 has three types of pixels 311a, 311b, and 311c densely arranged in a two-dimensional square lattice (matrix). Each pixel indicated by a rectangle includes a rectangular microlens 10 and a pair of photoelectric conversion units 15 and 16 in which a light receiving region is separated in the horizontal direction. That is, the arrangement direction of the pair of photoelectric conversion units is the horizontal direction (row direction). The pixels 311a belonging to the A group are arranged in a horizontal row, and the position of the row is a multiple of 3, that is, 3n (n is an integer). The pixels 311b belonging to the B group are arranged in a horizontal row, and the position of the row is a value obtained by adding 1 to a multiple of 3, that is, 3n + 1. The pixels 311c belonging to the C group are arranged in a horizontal row, and the row position is a value obtained by adding 2 to a multiple of 3, that is, 3n + 2.

  FIG. 3 shows the arrangement of color filters provided in each pixel. The color filters include three types of color filters having different spectral sensitivity characteristics of a red filter (R), a green filter (G), and a blue filter (B), and three types having these three types of color filters. Pixels are arranged according to the arrangement rule of the Bayer array.

  The light beam incident on the pixel 311 a is condensed on the pair of photoelectric conversion units 15 and 16 by the microlens 10.

  Here, a detailed structure of the pixel 311a will be described with reference to FIG.

  4 is a cross-sectional view of the pixel 311a when the cross section of the pixel array is taken along a straight line in the horizontal direction (X direction) in the vicinity of the center 191 of the photographing screen 100 shown in FIG. In the pixel 311 a, the light shielding mask 30 is formed on the surface 41 close to the photoelectric conversion units 15 and 16. The photoelectric conversion units 15 and 16 receive light limited by the opening 30 d of the light shielding mask 30. The pair of photoelectric conversion units 15 and 16 are formed on the semiconductor circuit substrate 29 with the element isolation region 17 as a boundary region. In the horizontal direction of the screen 100 (lateral direction in FIG. 4), the position of the axis 43 passing through the center of the element isolation region 17 coincides with the position of the optical axis 42 of the microlens 10.

  The opening 30 d is substantially square and the center thereof coincides with the axis 43. A planarizing layer 31 is formed on the light shielding mask 30, and a color filter 34 is formed thereon. A planarizing layer 32 is formed on the color filter 34, and the microlens 10 is formed thereon as an on-chip lens. By the microlens 10, the surface 40 on which the pair of photoelectric conversion units 15 and 16 are arranged has a conjugate relationship with a pupil plane (hereinafter referred to as a distance measurement pupil plane A) that is a predetermined distance away from the imaging surface.

  The photoelectric conversion units 15 and 16 formed on the semiconductor circuit substrate 29 receive incident light on the semiconductor substrate surface 40, and generate an amount of electric charge corresponding to the amount of received light by photoelectric conversion. This electric charge is read out of the image sensor 212 as an electric signal. The alignment direction of the pair of photoelectric conversion elements 15 and 16 is the horizontal direction, which is equal to the alignment direction of the region through which the pair of light beams pass on the distance measuring pupil plane described later. The photoelectric conversion element 15 receives one of the pair of light beams, and the photoelectric conversion element 16 receives the other of the pair of light beams. The same material as that of the planarization layer 31 is filled between the semiconductor substrate surface 40 and the light shielding mask 30.

  5 is a cross-sectional view of the pixel 311a when the cross section of the pixel array is taken along a straight line in the horizontal direction (X direction) in the vicinity of the position 192 that is separated from the center 191 of the shooting screen 100 in FIG. 2 by the distance Xa in the horizontal direction. Therefore, the same components as those shown in FIG. 4 are indicated by the same symbols as in FIG. 5 differs from FIG. 4 in that the position of the axis 43 passing through the center position of the element isolation region 17 in the horizontal direction of the screen 100 (the horizontal direction in FIG. 4) is greater than the position of the optical axis 42 of the microlens 10. This is a point that is deviated by ΔPa in a direction away from the center 191 (rightward in FIG. 5). Similar to FIG. 4, the surface 40 on which the pair of photoelectric conversion units 15 and 16 are arranged has a conjugate relationship with the distance measuring pupil plane A by the microlens 10. Compared to FIG. 4, in FIG. 5, the light beam received by the photoelectric conversion units 15 and 16 is a light beam inclined in the direction of the center 191 of the screen 100 with respect to the optical axis 42 of the microlens 10.

  In the configuration of FIG. 4, a pair of regions through which the light beams received by the photoelectric conversion units 15 and 16 pass on the distance measurement pupil plane A, and the light beams received by the photoelectric conversion units 15 and 16 in the configuration of FIG. A pair of regions that pass through match.

  4 and 5 are diagrams for the pixel 311a arranged at a specific position. In general, the pixel 311a has a horizontal distance from the center of the shooting screen to the pixel position (an arrangement direction of a region through which a pair of light beams received by the pair of photoelectric conversion units 15 and 16 on the distance measurement pupil plane A). Accordingly, the amount of deviation ΔPa of the shaft 43 passing through the center position of the element isolation region 17 with respect to the optical axis 42 of the microlens 10 in FIG. 5 is determined. For example, in FIG. 2, the deviation amount ΔPa in the pixel 311 a disposed in the vicinity of the position 193 that is horizontally separated from the center 191 of the shooting screen 100 by the distance Xb is disposed in the vicinity of the position 192 that is closer to the center 191 than the position 193. This amount is larger than the deviation amount ΔPa in the pixel 311a. 2, in the pixel 311a arranged on the left side of the Y axis of the photographing screen 100, the direction of the deviation amount ΔPa, that is, the deviation direction of the axis 43 with respect to the optical axis 42 is the left direction opposite to FIG. Become. The distance da from the photographing screen 100 to the distance measuring pupil plane A, the distance ds from the principal point of the microlens 10 to the surface 40 on which the pair of photoelectric conversion units are arranged, and the horizontal distance D from the photographing screen center to the pixel position Therefore, the deviation amount ΔPa is roughly expressed by ds × D / da.

  With the above configuration, the pair of light beams received by the photoelectric conversion units 15 and 16 in all the pixels 311a belonging to the group A pass through the same pair of regions on the distance measurement pupil plane A.

  6 and 7 are schematic diagrams for explaining the state of light beams received by the photoelectric conversion units 15 and 16 of the pixel 311a having the structure shown in FIGS. The straight line of the conversion units 15 and 16) shows a cross section of the optical system and the pixel array. Note that the pixel structure is simplified in the figure.

  6 and 7, the photoelectric conversion units 15 and 16 of the pixel 311a arranged on the image pickup device 212 respectively receive the light beams that have passed through the half of the light-shielding mask opening 30d disposed in proximity thereto. . The shape of the region through which the light beam received by the photoelectric conversion unit 16 passes through the light shielding mask opening 30d is on the distance measurement pupil plane 90 (distance pupil plane A) that is separated from the microlens 10 by the distance pupil distance da by the microlens 10. The image is projected onto a region 96 common to the photoelectric conversion units 16 of all the pixels 311a. Similarly, the shape of the region through which the light beam received by the photoelectric conversion unit 15 passes through the light shielding mask opening 30d is such that all the photoelectric conversion units 15 on the distance measurement pupil plane 90 separated from the micro lens 10 by the distance measurement pupil distance da by the micro lens 10. Are projected onto a common area 95. The pair of regions 95 and 96 is called a distance measuring pupil, and this corresponds to a divided pupil in so-called pupil division type focus detection.

  Therefore, the photoelectric conversion unit 15 of each pixel 311a receives the light beam 85 passing through the distance measuring pupil 95 and the microlens 10 of each pixel, and corresponds to the intensity of the image formed on each microlens 10 by the light beam 85. Output the signal. The photoelectric conversion unit 16 of each pixel 311a receives a light beam 86 passing through the distance measuring pupil 96 and the micro lens 10 of each pixel, and corresponds to the intensity of an image formed on each micro lens 10 by the light beam 86. Output the signal.

  Actually, on the distance measuring pupil plane 90, the luminous flux is limited by the aperture of the interchangeable lens. Even in the case of the brightest aperture diameter, the aperture diameter is smaller than the area where the distance measuring pupils 95 and 96 are added. Is set to be 6 and 7, an axis 91 is a normal line to the imaging screen passing through the center of the imaging screen 100 and coincides with the optical axis of the imaging optical system. The shape of the distance measurement pupils 95 and 96 is a symmetric shape with a straight line 92 passing through the optical axis 91 in the distance measurement pupil plane 90 as an axis of symmetry.

  The structures of the pixels 311b and 311c are basically the same as those of the pixel 311a shown in FIGS. 3 to 5 except for the following points. A deviation amount (of the microlens 10) determined in accordance with the distance in the horizontal direction (the direction parallel to the direction in which the pair of light beams received by the pair of photoelectric conversion units pass) from the center of the photographing screen to each pixel position. The deviation amount of the axis 43 passing through the center position of the element isolation region 17 with respect to the optical axis 42 is different from the deviation amount ΔPa of the pixel 311a. That is, the displacement amount ΔPb in the case of the pixel 311b and the displacement amount ΔPc in the case of the pixel 311c are made different from the displacement amount ΔPa of the pixel 311a.

  For example, when the horizontal distance from the center of the shooting screen to each pixel position (pixel 311a, pixel 311b, pixel 311c) is the same, the displacement amount ΔPb of the pixel 311b is larger than the displacement amount ΔPa of the pixel 311a, and the pixel 311c The displacement amount ΔPc is set smaller than the displacement amount ΔPa of the pixel 311a.

  By setting the deviation amounts of the pixels 311b and 311c in this way, the distance db to the distance measuring pupil plane B common to all the pixels 311b becomes smaller than the distance da described above, and all the pixels 311c The distance dc to the common distance measuring pupil plane C is larger than the distance da described above.

  Distances db and dc from the photographing screen 100 to the distance measuring pupil plane B and the distance measuring pupil plane C, a distance ds from the principal point of the microlens 10 to the surface 40 on which the pair of photoelectric conversion units are arranged, and a pixel from the center of the photographing screen The displacement amount ΔPb is schematically represented by ds × D / db and the displacement amount ΔPc is represented by ds × D / db depending on the horizontal distance D to the position.

  FIG. 8 is a diagram showing the relationship between the luminous flux received by the pixel 311a belonging to the A group, the pixel 311b belonging to the B group, and the pixel 311c belonging to the C group, and the distance measurement pupil distances da, db, dc. 2 is a diagram illustrating a cross section of an optical system and an image pickup device taken along a horizontal straight line in FIG. In FIG. 8, each pixel is shown as being arranged at the same image height (image height position is arbitrary) on the image sensor.

  The pair of photoelectric conversion units of the pixel 311a is a pair of light fluxes that pass through a pair of regions 95 and 96 that are symmetrical with respect to the optical axis in a pupil plane that is separated from the imaging surface of the imaging element 212 in the direction of the optical axis 91 by the distance measuring pupil distance da. Receives a solid line.

  The pair of photoelectric conversion units of the pixel 311b is a pair of light beams that pass through a pair of regions 195 and 196 that are symmetrical with respect to the optical axis in a pupil plane that is separated from the imaging surface of the imaging device 212 in the direction of the optical axis 91 by the distance measuring pupil distance db. Receives a solid line.

  The pair of photoelectric conversion units of the pixel 311c is a pair of light beams that pass through a pair of regions 295 and 296 that are optically symmetric on a pupil plane that is separated from the imaging surface of the imaging element 212 in the direction of the optical axis 91 by the distance measuring pupil distance dc. Receives a solid line.

  As disclosed in Japanese Patent Application Laid-Open No. 2009-282018, when the distance measurement pupil plane and the aperture opening (exit pupil plane) of the interchangeable lens do not coincide with each other, the vignetting of the pair of focus detection light fluxes occurs. . In the present embodiment, when focus detection is performed, the distance measuring pupil distance closest to the distance from the imaging surface 100 of the exit pupil of the interchangeable lens is selected from the three distance measuring pupil distances. As a result, the unbalance of the vignetting of the pair of focus detection light beams by the exit pupil of the interchangeable lens is reduced, and highly accurate focus detection is possible.

  A pair that passes through each of the pair of distance measurement pupils by combining the outputs of the pair of photoelectric conversion units of the pixels belonging to the group having the selected distance measurement pupil distance into a pair of output data corresponding to the pair of distance measurement pupils. Information on the intensity distribution of a pair of images formed on the pixel array (horizontal direction) by the focus detection light beam. By performing image shift detection calculation processing (correlation calculation processing, phase difference detection processing) on this information, the image shift amount of a pair of images by a so-called pupil division type phase difference detection method is detected. Furthermore, by performing a conversion operation according to the proportional relationship between the distance between the center of gravity of the pair of distance measurement pupils and the distance measurement pupil distance with respect to the image displacement amount, the current imaging plane at the focus detection position (vertical direction) and the current A deviation (defocus amount) from the image plane is calculated.

  Also, by adding the outputs of a pair of photoelectric conversion units of each pixel belonging to the three groups, the entire imaging light flux is received in the same manner as a normal imaging pixel having one photoelectric conversion unit instead of a pair of photoelectric conversion units. As a result, an output equivalent to that of the above case can be obtained, whereby high-quality image information with little deterioration can be obtained.

  FIG. 9 is a conceptual diagram of a circuit configuration of the image sensor 212. The image sensor is configured as a CMOS image sensor. The circuit configuration of the image sensor 212 will be described in a simplified manner with a layout of 4 pixels in the horizontal direction and 4 pixels in the vertical direction.

  In FIG. 9, pixels 311a surrounded by broken lines 110 and 113 are arranged in the first and fourth lines, pixels 311b surrounded by broken lines 111 are arranged in the second line, and broken lines 112 are enclosed in the third line. Pixels 311c are arranged.

  Common control signals φSn, φRn, φPn, and φQn are supplied from the vertical scanning circuit 503 to the pixels in the same row, for example, the n-th row, in order to control the operation of each pixel. The output of the pixel in each column is connected to a vertical signal line 501 common to each column. Each vertical signal line 501 is input to a correlated double sampling circuit (CDS circuit) 502, and sample hold and difference processing are performed for each column. The operation of the CDS circuit 502 is controlled by control signals φC1 and φC2 output from the vertical scanning circuit 503.

  The output signal for each column of the CDS circuit 502 is sequentially transferred to the output circuit 330 by the control signals φH1 to φH4 output from the horizontal scanning circuit 504, and is amplified with the amplification degree set by the output circuit 330 to be image pickup device. It is output outside 212.

  FIG. 10 is a detailed circuit diagram of each pixel (parts indicated by broken lines 110, 111, 112, and 113 in FIG. 9). A pair of photoelectric conversion units included in each pixel includes a pair of photodiodes PD1 and PD2. The pair of photodiodes PD1 and PD2 are connected to a floating diffusion layer (floating diffusion) FD via transfer MOS transistors 513 and 514, respectively. When the transfer MOS transistors 513 and 514 are turned on by the control signals φPn and φQn, respectively, the charges generated and stored in the pair of photodiodes PD1 and PD2 are transferred to the floating diffusion layer FD. The floating diffusion layer FD is connected to the gate of the amplification MOS transistor AMP, and the amplification MOS transistor AMP generates a signal corresponding to the amount of charge accumulated in the floating diffusion layer FD.

  The floating diffusion layer FD is connected to the power supply voltage Vdd via the reset MOS transistor 510. When the reset MOS transistor 510 is turned on by the control signal φRn, the charge accumulated in the floating diffusion layer FD is cleared and the reset state is set.

  The output of the amplification MOS transistor AMP is connected to the vertical output line 501 via the row selection MOS transistor 512. When the row selection MOS transistor 512 is turned on by the control signal φSn, the output of the amplification MOS transistor AMP is output to the vertical output line 501.

  In FIG. 10, when the transfer MOS transistor 513 is turned on by the control signal φPn, a signal corresponding to the amount of charge accumulated in the photodiode PD1 is output from the amplification MOS transistor AMP. Next, the transfer MOS transistor 514 is turned on by the control signal φQn in this state, whereby the charge amount accumulated in the photodiodes PD1 and PD2 in the floating diffusion layer FD is added, and a signal corresponding to the added charge amount is output. Output from the amplification MOS transistor AMP.

  FIG. 11 shows a detailed circuit configuration for each column of the CDS circuit 502 of FIG. The vertical output line 501 is input to the sample & hold circuit 521 (for holding the pixel reset level) and the sample & hold circuit 522 (for holding the pixel signal level). The signal on the vertical output line 501 is sampled and held in the sample & hold circuit 521 and sample & hold circuit 522 when the control signals φC1 and φC2 are turned ON. The difference circuit 523 subtracts the signal sampled and held by the sample and hold circuit 521 from the signal sampled and held by the sample and hold circuit 522 and outputs the result.

  The operation of the image sensor 212 has two operation modes, that is, a first readout mode and a second readout mode. In the first readout mode, a normal pixel signal output operation for recording an image generated by imaging, that is, an operation of reading out the added output signals of the photodiodes PD1 and PD2 from all the pixels is performed. In the second readout mode, an operation of reading out the added output signals of the photodiodes PD1 and PD2 from all the pixels to display an image on the liquid crystal display element 216 and reading out the single output signal of the photodiode PD1 to perform focus detection I do. The imaging device switches between the first readout mode and the second readout mode in accordance with a control signal from the body drive control device 214, and the vertical scanning circuit 503 and the horizontal scanning circuit 504 have various control signals described above in accordance with the readout mode. Change the timing.

  FIG. 12 is an operation timing chart of the image sensor shown in FIG. 9 in the first readout mode. At time t0, the pixels in the first row are selected by the control signal φS1 generated by the vertical scanning circuit 503. The control signal φR1 is turned ON at time t0, and the floating diffusion layer FD of the pixels in the first row is reset to the reset level. At time t1, the control signal φR1 is turned OFF and the control signal φC1 is turned ON, and the reset level of the pixel in each column is sampled and held by the CDS circuit 502 for each column. After the control signal φC1 is turned OFF, the control signals φP1 and φQ1 are simultaneously turned ON at time t2, the charges accumulated in the photodiodes PD1 and PD2 are added in the floating diffusion layer FD, and the electric charge corresponding to the added charge amount A signal is output to the vertical signal line 501. At time t3, the control signals φP1 and φQ1 are simultaneously turned OFF, the control signal φC2 is turned ON, and the added signal level of the pixels in each column is sampled and held by the CDS circuit 502 for each column. At this time, the CDS circuit 502 outputs a signal obtained by subtracting the reset level from the added signal level. After the control signal φC2 is turned OFF, the control signal φS1 is turned OFF at time t4, and the addition signal for each column of the CDS circuit 502 is transferred to the output circuit 330 according to the scanning signals φH1 to φH4 sequentially generated from the horizontal scanning circuit 504. Then, the signal is amplified with the amplification degree set by the output circuit 330 and output to the outside of the image sensor 212.

  At the time t5 when the output of the addition signal for the pixels in the first row from the output circuit 330 is completed, the pixels in the second row are selected by the control signal φS2 generated by the vertical scanning circuit 503, and the same operation as described above is performed. The addition signal for the pixels in the second row is output from the output circuit 330. Subsequently, the addition signal in the third and fourth rows is output from the output circuit 330. When the output of the addition signals for all the pixels is completed, the operation returns to the first row again and the above operation is repeated periodically.

  FIG. 13 is an operation timing chart of the image sensor shown in FIG. 9 in the second readout mode. A case will be described in which only the pixel in the third row (pixel 311c belonging to group C) outputs a single signal of the photodiode PD1 for focus detection in addition to the addition signal output.

  Output of the addition signal of the pixels in the first row and the second row is performed in the same manner as in the timing chart of FIG. The pixel in the third row is selected by the control signal φS3 generated by the vertical scanning circuit 503 at the time t10 when the output of the addition signal of the pixel in the second row from the output circuit 330 is completed. The control signal φR3 is turned ON at time t10, and the floating diffusion layer FD of the pixels in the third row is reset to the reset level. At time t11, the control signal φR3 is turned OFF and the control signal φC1 is turned ON, and the reset level of the pixel in each column is sampled and held by the CDS circuit 502 for each column. After the control signal φC1 is turned off, the control signal φP3 is turned on at time t12, the charge accumulated in the photodiode PD1 is transferred in the floating diffusion layer FD, and the electric signal corresponding to the transferred charge amount is a vertical signal line. 501 is output. At time t13, the control signal φP3 is turned off and the control signal φC2 is turned on, and the signal level corresponding to the amount of charge accumulated in the photodiode PD1 of the pixel in each column is sampled and held by the CDS circuit 502 for each column. The At this point, the CDS circuit 502 outputs a signal obtained by subtracting the reset level from the signal level corresponding to the amount of charge accumulated in the photodiode PD1. After the control signal φC2 is turned OFF, the output for each column of the CDS circuit 502 after time t14 is transferred to the output circuit 330 according to the scanning signals φH1 to φH4 sequentially issued from the horizontal scanning circuit 504 and set by the output circuit 330. The signal is amplified with the degree of amplification and output to the outside of the image sensor 212.

  When the output from the output circuit 330 of the single signal corresponding to the amount of charge accumulated in the photodiode PD1 of the pixel in the third row is finished (time t15), the control signal φQ3 is turned ON, and the floating diffusion layer FD performs photo The charge accumulated in the diode PD1 and the charge accumulated in the photodiode PD2 are added, and an electric signal corresponding to the added charge amount is output to the vertical signal line 501. At time t16, the control signal φQ3 is turned OFF and the control signal φC2 is turned ON, and the added signal level of the pixels in each column is sampled and held by the CDS circuit 502 for each column. At this time, the CDS circuit 502 outputs a signal obtained by subtracting the reset level from the added signal level. After the control signal φC2 is turned OFF, the output for each column of the CDS circuit 502 is transferred to the output circuit 330 according to the scanning signals φH1 to φH4 sequentially issued from the horizontal scanning circuit 504 and set by the output circuit 330 after time t17. The signal is amplified with the degree of amplification and output to the outside of the image sensor 212.

  When the output of the addition signal for the pixels in the third row is completed, the output of the addition signal for the pixels in the fourth row is performed in the same manner as in the timing chart of FIG. When the addition output signal of all the pixels and the output of the single signal of the third row are completed, the operation returns to the first row again and the above operation is repeated periodically.

  In the timing chart of FIG. 13, only the pixel in the third row (the pixel 311c belonging to the group C) has been described as outputting a single signal of the photodiode PD1 for focus detection in addition to the addition signal output. However, the pixel row that outputs a single signal can be changed according to the selection signal from the body drive control device 214, and the group A or B corresponding to the pixel row that outputs another single signal is the body drive control device 214. Can be selected in response to a selection signal from. When group A is selected, a single signal of the photodiode PD1 of the pixel 311a belonging to group A is output. When group B is selected, a single signal of the photodiode PD1 of the pixel 311b belonging to group B is output. The vertical scanning circuit 503 and the horizontal scanning circuit 504 can change the timing of the various control signals described above according to the selected pixel row.

  FIG. 14 is a flowchart illustrating an imaging operation of the digital still camera 201 according to the present embodiment. Each processing step shown in FIG. 14 is executed by the body drive control device 214. When the power of the digital still camera 201 is turned on by the body drive control device 214 in step S100, the image sensor 212 starts an operation of repeating an imaging operation at a constant cycle (for example, outputting 60 frames per second). In step S110, a set of pixel groups (pixel 311a, pixel 311b, and pixel 311c) extending over three consecutive rows according to the vertical position of the focus detection position on the shooting screen selected by operating the operation member 220. Selected. Furthermore, one row of a set of pixel groups (pixel 311a, pixel 311b, and pixel 311c) over three consecutive rows is selected according to the exit pupil distance of the interchangeable lens obtained by communication with the interchangeable lens.

  FIG. 15 is a diagram for explaining which pixel is selected from the pixels (pixel 311a, pixel 311b, and pixel 311c) that belong to three groups according to the exit pupil distance. In the body drive control unit 214, correspondence between distance d1 (da> d1 ≧ db), distance d2 (dc> d2 ≧ da), and distance measurement pupil distances da, db, and dc, and groups A, B, and C, which will be described later. Attribute information regarding the relationship and the correspondence relationship between the groups A, B, and C and the pixels 311a, 311b, and 311c belonging to the respective groups is stored in advance. Based on the information stored in advance, the body drive control device 214 selects the row of the pixels 311b belonging to the group B when the exit pupil distance of the interchangeable lens is smaller than the distance d1, and the exit pupil of the interchangeable lens. When the distance is larger than the distance d1 and smaller than the distance d2, the row of the pixel 311a belonging to the group A is selected, and when the exit pupil distance of the interchangeable lens is larger than the distance d2, the row of the pixel 311c belonging to the group C is selected. .

  The distance d1 is the unbalance amount generated by the exit pupil in the pair of focus detection light beams received by the pixels 311a belonging to the group A and the pixels belonging to the group B when the horizontal distance from the center of the photographing screen to the pixels is the same. It is determined as the distance at which the unbalance amount generated by the exit pupil is equal in the pair of focus detection light beams received by 311b. Specifically, in FIG. 15, the distance in the horizontal direction from the center of the shooting screen to the pixel 311a (the direction in which the pair of light beams received by the pair of photoelectric conversion units pass) is D, and from the center of the shooting screen to the pixel 311b. (−D), the distance in the horizontal direction (the direction in which the pair of light beams received by the pair of photoelectric conversion units pass) is (−D), and is directed from each pixel to the center of the distance measurement pupil plane A and the distance measurement pupil plane B. The above condition is satisfied by setting the distance at which the lines intersect to be d1. The distance d1 is a distance that internally divides the distance measurement pupil plane A and the distance measurement pupil plane B into da: db, and is d1 = 2 × da × db / (da + db).

  Similarly, the distance d2 is a distance that internally divides the distance measuring pupil plane A and the distance measuring pupil plane C into da: dc, and is d2 = 2 × da × dc / (da + dc).

  In step S115, data for one frame is read in the second reading mode. Note that the single signal readout row in the second readout mode is the row selected in step S110. A single signal is read from the pixels arranged in the row corresponding to the selected focus detection area, and an addition signal is read from all the pixels. The read single signal and addition signal are stored in the body drive control unit 214.

  In subsequent step S120, a display image is generated using the addition signal read in the second read mode as display data, and the liquid crystal display element 216 outputs the live view display. In step S130, a single signal (photodiode PD1 signal) read in the second read mode is subtracted from the addition signal (photodiode PD1 signal + photodiode PD2 signal) read and stored in the second read mode. A single signal (a signal of the photodiode PD2) corresponding to the amount of charge accumulated in the photodiode PD2 is generated.

  In step S140, out of a pair of pixel signals formed from the single signal (signal of photodiode PD1) read and stored in step S110 and the single signal generated in step S130 (signal of photodiode PD2). By calculating the phase difference between a pair of pixel signals (the signal of the photodiode PD1 and the signal of the photodiode PD2) of the pixels arranged in the column corresponding to the horizontal range in the screen of the selected focus detection area The focus adjustment state of the photographing optical system is detected. That is, focus detection is performed and a defocus amount is calculated. When the reliability of the defocus amount is low or when the defocus amount cannot be calculated, focus detection is impossible.

  In step S150, it is checked whether or not the focus is close, that is, whether or not the calculated absolute value of the defocus amount is within a predetermined value. If it is determined that the lens is not in focus, the process proceeds to step S160, where the defocus amount is transmitted to the lens drive controller 206, and the focusing lens 210 of the interchangeable lens 202 is driven to the focus position. Then, it returns to step S110 and repeats the operation | movement mentioned above.

  Even when focus detection is impossible, the process branches to this step, a scan drive command is transmitted to the lens drive control device 206, and the focusing lens 210 of the interchangeable lens 202 is scan-driven from infinity to the nearest. Then, it returns to step S110 and repeats the operation | movement mentioned above.

  If it is determined in step S150 that the focus is close to the focus, the process proceeds to step S170, and it is determined whether or not a shutter release has been performed by operating a shutter button (not shown). If it is determined that the shutter release has not been performed, the process returns to step S110 and the above-described operation is repeated. On the other hand, if it is determined that the shutter release has been performed, the process proceeds to step S180, where an aperture adjustment command is transmitted to the lens drive control unit 206, and the aperture value of the interchangeable lens 202 is set to the control F value (the F value set by the photographer or F value set automatically). When the aperture control is completed, the imaging device 212 is caused to perform an imaging operation with an exposure time corresponding to the subject brightness, and the addition signal is read out from all the pixels of the imaging device 212 in the first readout mode. Image processing is performed to generate image data.

  In subsequent step S190, the generated image data is output and stored in the memory card 219, and the process returns to step S110 to repeat the above-described operation. Further, in step S190, the generated image data may be output to the liquid crystal display element 216 for live view display.

  Next, details of calculation of the defocus amount in step S140 of FIG. 14 and general image shift detection calculation processing (correlation calculation processing) used for the calculation are disclosed in Japanese Patent Application Laid-Open No. 2010-129783, The defocus amount is calculated by multiplying the image shift amount by the conversion coefficient. If, for example, a green pixel and a red pixel are arranged in the row read in the second readout mode, the defocus amounts are calculated from the green pixel data and the red pixel data, respectively. The conversion coefficient changes according to the aperture diameter (F value) because the center-of-gravity distance of the distance measuring pupil changes according to the aperture diameter.

  Since the defocus amount is calculated based on the output signal of the green pixel and similarly the defocus amount is calculated based on the output signal of the red pixel, both are averaged to obtain the final defocus amount of the selected focus detection area. Focus amount.

  In the present embodiment, a pixel that is optimal for focus detection, that is, a pixel that minimizes the unbalance between a pair of focus detection light beams generated by the exit pupil is selected according to the exit pupil distance of the interchangeable lens. Therefore, the focus detection accuracy is improved, and the image data at the pixel position can be obtained simply and with high accuracy simply by adding the signals of the pair of photoelectric conversion units of the pixels arranged at the pixel position. The image quality is also improved.

  In the second readout mode, in one-frame pixel signal readout operation, signals from a pair of photoelectric conversion units of all pixels are added to read out signals, and only a pair of photoelectric conversions are performed on pixels arranged in a row used for focus detection. One of the signals can be read out independently. Therefore, the increase in the number of readout signals due to each pixel having a pair of photoelectric conversion units is minimal as compared with the prior art, and focus detection and image display / recording are performed by readout of one frame. The focus detection and image display / recording responses are not degraded.

  In addition, since the signals of the pair of photoelectric conversion units are added inside the image sensor, a configuration and load for adding the signals from the pair of photoelectric conversion units outside the image sensor are unnecessary, and the configuration is simple. Quick display and recording without delay is possible.

  In addition, it is possible to obtain image data at the pixel position with high accuracy by using only the signals of the pair of photoelectric conversion units of the pixel. That is, since interpolation processing using adjacent pixel signals is not necessary, pixels that generate signals used for focus detection can be arranged very close or adjacent to each other. Therefore, it is possible to minimize the movement of the focus detection position in the vertical direction that occurs when different pixels are used for focus detection according to group selection.

---- Modified example ---
(1) In the embodiment described above, one group is selected according to the exit pupil distance of the interchangeable lens, and one row belonging to the group is selected according to the position of the selected focus detection area. In the second read mode, a single signal is additionally read in that row. However, as a matter of course, a plurality of adjacent rows belonging to the selected group may be selected and a single signal may be read out in the plurality of rows.

  For example, when the range of the focus detection area is relatively wide in the vertical direction, a plurality of rows in the same group in the vertical range in the shooting screen of the focus detection area are selected, and single signals are read out in the plurality of rows. I do.

(2) In the above-described embodiment, the single signal is read out in all the pixels belonging to the selected row in the second readout mode. However, by limiting the control signal from the horizontal scanning circuit, the single signal may be read out only in some of the pixels belonging to the row.

  For example, when a single signal is read out, only a part of the pixels is obtained by applying a control signal from the horizontal scanning circuit only to the pixels constituting the pixel column corresponding to the horizontal range in the screen of the selected focus detection area. It is possible to read out a single signal in FIG. 1, and the reading time as a whole can be further shortened.

(3) In the above-described embodiment, in the second readout mode, single signals are read out from a row in which pixels including a pair of photoelectric conversion units arranged in the horizontal direction are arranged in the horizontal direction. However, a single signal may be read out from a column in which pixels including a pair of photoelectric conversion units arranged in the vertical direction are arranged in the vertical direction.

  For example, the timing of the control signals output from the vertical scanning circuit and the horizontal scanning circuit can be changed so that the single signal is read out only for pixels in a specific column in all rows. This makes it possible to detect the focus even when the contrast of the image changes only in the vertical direction.

(4) In the above-described embodiment, description has been made assuming that all the pixels of the image sensor have a pair of photoelectric conversion units. However, the present invention is not limited to this, and some pixels of the image sensor are The present invention can also be applied to a configuration having a pair of photoelectric conversion units.

  FIG. 16 is a front view showing the arrangement of focus detection areas on the imaging screen 100 (imaging screen of the interchangeable lens 202) defined on the imaging surface of the imaging element 212 in this modification. FIG. 16 shows regions (focus detection area, focus detection position) where an image is sampled on the shooting screen in focus detection using an array of focus detection pixels including a pair of photoelectric conversion units on the image sensor 212. It is an example. In this example, focus detection areas 101 to 105 are arranged at the center (on the optical axis) on the rectangular shooting screen 100 and at five locations on the top, bottom, left, and right. Focus detection pixels are linearly arranged in the longitudinal direction of the focus detection area indicated by a rectangle. In the focus detection areas 101, 102, 103, 104, and 105, focus detection pixels are arranged in the horizontal direction.

  FIG. 17 is a front view showing a detailed configuration of the image sensor 212. Details of the pixel arrangement in which the vicinity of an arbitrary focus detection area in the focus detection areas 101, 102, 103, 104, and 105 in FIG. Show. In the imaging element 212, known imaging pixels 310 are densely arranged in a two-dimensional square lattice. Each imaging pixel 310 has one photoelectric conversion unit 11. The shape of the region through which the light beam received by the photoelectric conversion unit 11 passes corresponds to the shape of the region obtained by combining both the pair of regions 95 and 96 shown in FIGS. 6 and 7, that is, the shape of the exit pupil of the interchangeable lens 202. The imaging pixel 310 includes a red pixel (R), a green pixel (G), and a blue pixel (B), and is arranged according to a Bayer arrangement rule. For focus detection, the focus detection pixels 311a belonging to the A group having the same pixel size as the imaging pixels are arranged in a horizontal direction in a straight line in the horizontal direction in which the green pixels and the red pixels should be continuously arranged. The focus detection pixels 311b belonging to the B group are adjacent to the row in which the focus detection pixels 311a are arranged, and the original green pixels and blue pixels are continuously arranged in a straight line in the horizontal direction. The focus detection pixels 311c belonging to the group C are arranged in a horizontal direction and are adjacent to the row in which the focus detection pixels 311b are arranged, and the original green pixels and red pixels should be arranged continuously in a horizontal parallel manner. Are arranged horizontally in a row. The focus detection pixels 311a, 311b, and 311c are provided with a color filter having the same color arrangement as that of the imaging pixel that should be originally arranged at the position.

  In the imaging device having the above-described configuration, one group is selected according to the exit pupil distance, and three rows arranged at positions corresponding to the position of the focus detection area selected by the user according to the selected group. One row in (focus detection pixels 311a, 311b, 311c) is selected. In the second readout mode, the readout of the single signal and the readout of the addition signal are performed from the focus detection pixels arranged in the selected row, and the readout of the addition signal is performed only from the focus detection pixels of the row not selected. . Further, normal signals are read from the row where the imaging pixels are arranged. In such a configuration, normal imaging pixels other than the pixels corresponding to the focus detection area can be used, so that the structure of the imaging element can be simplified.

(5) In the above-described embodiment, since the image signal is generated by the signal obtained by adding the signals of the pair of photoelectric conversion units of the pixels, the quality of the image signal is improved as compared with the related art. As illustrated in FIGS. 4 and 5, since there is an element isolation region having no photosensitivity between the pair of photoelectric conversion units, when the aperture F value of the interchangeable lens is increased, the addition signal and the element isolation region 1 that has no element isolation region are present. The difference from the signal (actual imaging output) of the original imaging pixel having two photoelectric conversion units becomes large. By correcting the addition signal in consideration of this, a more accurate image signal can be obtained.

  FIG. 18 is a front view showing a range of light beams incident on the pair of photoelectric conversion units 15 and 16, taking the pixel 311 a arranged in the vicinity of the center 191 of the photographing screen 100 in FIG. 2 as an example. An image of the exit pupil of the optical system that is the interchangeable lens 202 is formed in a circular shape by the microlens 10 on the pair of photoelectric conversion units 15 and 16 of the pixel. The center position C of the image of the circular exit pupil coincides with the center position G of the element isolation region 17 corresponding to the position of the center of gravity of the photoelectric conversion elements 15 and 16.

  When the F value of the photographing optical system is small, the exit pupil image is represented by a circle 51. Since the luminous flux enters the circle 51 and the amount of the luminous flux incident on the element isolation region 17 is smaller than the total luminous flux, the added signal output is obtained by adding the outputs of the pair of photoelectric conversion units 15 and 16. And the actual imaging output is small.

  When the F value of the photographing optical system is medium, the image of the exit pupil is represented by a circle 52. Since the light beam enters the circle 52 and the amount of the light beam incident on the element isolation region 17 is larger than the total light beam amount, an addition signal obtained by adding the outputs of the pair of photoelectric conversion units 15 and 16. The deviation between the output and the actual imaging output becomes large.

  When the F value of the photographing optical system is further increased, the exit pupil image is represented by a circle 53. Since the light beam enters the circle 53 and the amount of the light beam incident on the element isolation region 17 is larger than the total light beam amount, the sum obtained by adding the outputs of the pair of photoelectric conversion units 15 and 16 is added. The deviation between the signal output and the actual imaging output is further increased.

  In order to correct the deviation caused by the presence of the element isolation region as described above, the addition signal obtained by adding the outputs of the pair of photoelectric conversion units is multiplied by a correction coefficient corresponding to the F value of the photographing optical system. Thus, the addition signal is corrected and converted into an imaging output. By doing so, a deviation between the imaging output and the actual imaging output is prevented.

  FIG. 19 is a diagram showing the relationship between the F value of the photographing aperture explained in FIG. 18 and the correction coefficient. As represented by the solid line 61, the value of the correction coefficient is approximately 1 when the F value is small, but changes to a value greater than 1 as the F value increases. The value of the correction coefficient may be an actual measurement value obtained by measuring the ratio between the actual imaging output and the added signal, or a design obtained by calculating the ratio between the actual imaging output and the added signal based on the design data. It may be a value. The ratio between the actual imaging output and the added signal is, for example, the area value of the circle 51, 52 or 53 representing the exit pupil image shown in FIG. 18, and the overlap between the circle and the element isolation region 17 based on the area value. It is a ratio to the value obtained by subtracting the area value.

  A lookup table based on the relationship between the F value and the correction coefficient shown in FIG. 19 is stored in, for example, a memory included in the body drive control device 214. F value information at the time of imaging is acquired by communication with an interchangeable lens, and a correction coefficient corresponding to the F value is selected with reference to a lookup table based on the relationship between the F value and the correction coefficient shown in FIG. By correcting the correction coefficient by the addition signal obtained by adding the outputs of the pair of photoelectric conversion units, it is possible to obtain a high-quality imaging output with little deviation from the actual imaging output.

  FIG. 20 is a front view showing a range of light beams incident on the pair of photoelectric conversion units 15 and 16 by taking, as an example, a pixel 311a arranged at a position horizontally separated from the center 191 of the photographing screen 100 in FIG. It is. The case where the exit pupil distance dn1 of the interchangeable lens 202 is shorter than the distance measurement pupil distance da is shown. On the pair of photoelectric conversion units 15 and 16 of the pixel, an image of the exit pupil of the optical system that is the interchangeable lens 202 is roughly formed in a circular shape by the microlens 10. Since the pair of light fluxes are limited asymmetrically, the center position C of the circular image of the exit pupil deviates from the center position G of the element isolation region 17 corresponding to the gravity center position of the photoelectric conversion units 15 and 16.

  The amount of deviation varies depending on the horizontal distance (image height) from the center 191 of the photographing screen 100 to the pixel, and the relationship between the distance measurement pupil distance and the exit pupil distance. In FIG. 20, when the F value of the photographing optical system is small, the image of the exit pupil is represented by a circle 51. Since the light beam enters the circle 51 and the amount of the light beam entering the element isolation region 17 is smaller than the total light beam amount, the sum signal obtained by adding the outputs of the pair of photoelectric conversion units 15 and 16 and Deviation from actual imaging output is small.

  When the F value of the photographing optical system is medium, the image of the exit pupil is represented by a circle 52. Since the light beam enters the circle 52 and the amount of the light beam incident on the element isolation region 17 is larger than the total light beam amount, an addition signal obtained by adding the outputs of the pair of photoelectric conversion units 15 and 16. And the actual imaging output become larger.

  When the F value of the photographing optical system is further increased, the exit pupil image is represented by a circle 53. Since the light beam enters the circle 53 and the amount of the light beam incident on the element isolation region 17 is larger than the total light beam amount, the sum obtained by adding the outputs of the pair of photoelectric conversion units 15 and 16 is added. The deviation between the signal and the actual imaging output is further increased.

  Comparing FIG. 18 with FIG. 20, in FIG. 20, since the center position G of the element isolation region 17 and the center position C of the circular image of the exit pupil are shifted, the amount of the light beam incident on the element isolation region 17 Is less in FIG.

  A deviation between the addition signal of the pair of photoelectric conversion units and the actual imaging output caused by the above phenomenon is corrected. By correcting the addition signal obtained by adding the outputs of the pair of photoelectric conversion units 15 and 16 by multiplying the correction coefficient corresponding to the F value of the photographing optical system, the exit pupil distance, and the image height of the pixel, Calculation to convert to imaging output is performed. By doing so, a deviation between the imaging output and the actual imaging output is prevented.

  FIG. 21 illustrates correction for correcting an error generated between the addition signal of the pair of photoelectric conversion units and the actual imaging output in accordance with the F value of the photographing aperture, the exit pupil distance, and the image height of the pixel as described above. It is the figure which showed the relationship between a coefficient and F value. The value of the correction coefficient is approximately 1 when the F value is small, but changes to a value larger than 1 as the F value increases. A solid line 61 represents the relationship between the F value and the correction coefficient when the exit pupil distance is equal to the distance measurement pupil distance, and is the same as the solid line 61 representing the correction coefficient in FIG.

  A broken line 62 represents the relationship between the F value and the correction coefficient when the exit pupil distance at the predetermined image height I1 is different from the distance measurement pupil distance, and the correction coefficient becomes a value smaller than the solid line 61 as the F value increases. A dotted line 63 represents the relationship between the F value and the correction coefficient in the case of the same exit pupil distance as that of the broken line 62 at a predetermined image height I2 that is larger than the predetermined image height I1, and the broken line 62 indicates that the F value increases. Small value.

  Although only correction coefficients for three types of image heights at typical exit pupil distances are shown in FIG. 21, correction coefficients can be determined according to any exit pupil distance and image height. Therefore, a correction coefficient corresponding to the F value at the time of imaging, the exit pupil distance, and the image height is selected, and the correction signal is multiplied by the addition signal obtained by adding the outputs of the pair of photoelectric conversion units 15 and 16. Thus, it is possible to obtain a high quality imaging output with a small deviation between the imaging output calculated by the above and the actual imaging output.

(6) The imaging device is not limited to a digital still camera having a configuration in which an interchangeable lens is attached to the camera body as described above. For example, the present invention can also be applied to a lens-integrated digital still camera or a video camera. Furthermore, the present invention can be applied to a small camera module built in a mobile phone, a surveillance camera, a visual recognition device for a robot, an in-vehicle camera, and the like.

10 microlens, 11, 15, 16 photoelectric conversion unit, 17 element isolation region,
29 semiconductor circuit board, 30 light shielding mask, 31, 32 planarization layer,
34 color filter, 40 semiconductor substrate surface, 41 surface, 42 optical axis, 43 axis,
51, 52, 53 circle, 61 solid line, 62 broken line, 63 dotted line,
85, 86 Luminous flux, 90 Distance pupil plane, 91 axis (optical axis), 92 straight line,
95, 96, 195, 196, 295, 296 area (ranging pupil),
100 shooting screen, 101-105 focus detection area,
110, 111, 112, 113 broken line,
180 region, 191 center, 192, 193 position,
201 digital still camera, 202 interchangeable lens, 203 camera body,
204 mount unit, 206 lens drive control device,
208 zooming lens, 209 lens, 210 focusing lens,
211 Aperture, 212 Image sensor, 213 Electrical contact,
214 body drive control device, 215 liquid crystal display element drive circuit, 216 liquid crystal display element,
217 eyepiece, 219 memory card, 220 operation member,
310 imaging pixel, 311 focus detection pixel, 330 output circuit,
501 vertical signal line, 502 CDS circuit,
503 vertical scanning circuit, 504 horizontal scanning circuit,
510 reset MOS transistor, 512 row selection MOS transistor,
513, 514 transfer MOS transistor,
521, 522 Sample & hold circuit, 523 Difference circuit

Claims (9)

An image sensor having a first pixel and a second pixel,
The first pixel is disposed at a predetermined distance from a line passing through the center of the image sensor in the first direction, and first and second photoelectric conversions that photoelectrically convert light transmitted through the first microlens and the first microlens. And a separation unit that is provided at a first distance in the first direction from the optical axis of the first microlens and separates the first photoelectric conversion unit and the second photoelectric conversion unit,
The second pixel is disposed at the predetermined distance from a line passing through the center of the imaging device in the first direction, and performs third and fourth photoelectric conversion on light transmitted through the second microlens and the second microlens. A photoelectric conversion unit and a separation that is provided at a second distance different from the first distance in the first direction from the optical axis of the second microlens and separates the third photoelectric conversion unit and the fourth photoelectric conversion unit An imaging device. The imaging device according to claim 1,
The imaging device includes a plurality of the first pixels and a plurality of the second pixels,
The plurality of first pixels have different first distances depending on the distance from a line passing through the center of the image sensor,
The plurality of second pixels are image sensors having different second distances depending on a distance from a line passing through a center of the image sensor. A first microlens and a first and second photoelectric conversion units for photoelectrically converting light transmitted through the first microlens; and a first distance from an optical axis of the first microlens in a first direction; A first pixel that has a separation unit that separates one photoelectric conversion unit and the second photoelectric conversion unit, and is disposed at a predetermined image height position in the first direction;
A second microlens and third and fourth photoelectric conversion units for photoelectrically converting light transmitted through the second microlens; a second different from the first distance in the first direction from the optical axis of the second microlens; A second pixel provided at a distance and having a separation unit that separates the third photoelectric conversion unit and the fourth photoelectric conversion unit, and is disposed at the predetermined image height position in the first direction; An image sensor provided. The imaging device according to claim 3,
The imaging device includes a plurality of the first pixels and a plurality of the second pixels,
The plurality of first pixels have different first distances depending on image height positions,
The plurality of second pixels are image sensors in which the second distance is different depending on an image height position. In the imaging device according to any one of claims 1 to 4,
The first pixel and the second pixel are image sensors arranged in a second direction that intersects the first direction. The imaging device according to any one of claims 1 to 5,
An imaging unit including: a detection unit configured to perform focus detection of the optical system by selecting at least one of a signal output from the first pixel and a signal output from the second pixel based on a pupil distance of the optical system; apparatus. The imaging device according to claim 6,
A receiver that receives information about the optical system from an interchangeable lens having the optical system;
The detection unit performs focus detection of the optical system by selecting at least one of a signal output from the first pixel and a signal output from the second pixel based on information received by the reception unit. Imaging device. The imaging device according to any one of claims 1 to 5,
Selecting at least one of the first pixel and the second pixel based on a pupil distance of an optical system, and based on a signal output from at least one of the selected first pixel and second pixel; An imaging apparatus comprising: a detection unit that performs focus detection of an optical system. The imaging device according to claim 8,
A receiver that receives information about the optical system from an interchangeable lens having the optical system;
The imaging unit is configured to perform focus detection of the optical system by selecting at least one of the first pixel and the second pixel based on information received by the reception unit.

Images