JP5962830B2 - Focus detection device - Google Patents

Description

The present invention relates to a focus detection apparatus.

  2. Description of the Related Art An imaging device that includes an imaging element in which an imaging pixel and a pupil division type focus detection pixel are mounted together is known (see, for example, Patent Document 1). In such an imaging apparatus, pupil-divided focus detection pixels are linearly arranged on the imaging surface, and the focus adjustment state of the image formed on the focus detection pixel array is detected based on the output of the focus detection pixel array. doing. In addition, a complementary metal oxide semiconductor (CMOS) image sensor is known as an image sensor. In the basic operation method of the CMOS image sensor, image data is read in time series by a rolling shutter (line exposure sequential reading method).

JP-A-1-216306

  However, when a CMOS sensor is applied to the imaging device described in Patent Document 1, the exposure time of the CMOS image sensor is shifted for each horizontal line due to the rolling shutter. Therefore, when the exposure conditions of the focus detection pixels change during the rolling shutter operation, each focus detection pixel in the focus detection pixel array outputs a signal under a different exposure condition, and accurate focus detection is performed. May not be able to perform.

In the focus detection device, the first focus detection pixel having the first and second photoelectric conversion units that receive the first and second light beams that have passed through the first and second pupil regions of the optical system is the first focus detection pixel. A second focus detection pixel having first and second photoelectric conversion units arranged in the direction and receiving the third and fourth light fluxes passing through the third and fourth pupil regions of the optical system; are arranged in a second direction different from the first direction, and an image pickup element which performs a rolling shutter operation in which the first and readout of the second focus detection pixels are sequentially performed for each row of said first direction, said first The focus of the optical system based on the signals of the first and second photoelectric conversion units of one focus detection pixel or based on the signals of the first and second photoelectric conversion units of the second focus detection pixel a focus detection unit for detecting the state, a diaphragm driver that changes the aperture value by driving the aperture The focus detection unit detects the focus state using signals of the first and second photoelectric conversion units of the first focus detection pixel when the diaphragm is driven, and The focus state is not detected using the signals of the first and second photoelectric conversion units of the second focus detection pixel.

  According to the present invention, it is possible to prevent a focus detection malfunction even when the aperture diameter changes during the rolling shutter operation and the exposure conditions change.

It is a cross-sectional view showing the configuration of the digital still camera of one embodiment. It is a figure which shows the focus detection position on the imaging | photography screen of an interchangeable lens. It is a front view which shows the detailed structure of an image pick-up element. It is a front view which shows the detailed structure of an image pick-up element. It is a figure which shows the shape of the micro lens of an imaging pixel and a focus detection pixel. It is a front view of an imaging pixel. It is a front view of a focus detection pixel. It is a figure which shows the spectral characteristics of a green pixel, a red pixel, and a blue pixel. It is a figure which shows the spectral characteristic of a focus detection pixel. It is sectional drawing of an imaging pixel. It is sectional drawing of a focus detection pixel. It is a figure for demonstrating the mode of the imaging light beam which an imaging pixel receives. It is a figure for demonstrating the mode of the imaging light beam which a focus detection pixel receives. It is a figure which simplifies and shows the circuit structure of an image pick-up element. It is a figure which shows the basic circuit structure with respect to one photoelectric conversion part in an imaging pixel and a focus detection pixel. 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 which shows the relationship of the correlation amount C (k) with respect to the shift amount k of a pair of data. It is explanatory drawing in the case of converting an image shift amount into a defocus amount. It is a flowchart which shows the detail of a defocusing amount calculation process. 6 is a timing chart showing the relationship between the state of the aperture diameter and the operation of the image sensor and the passage of time. It is a front view which shows the detailed structure of an image pick-up element. It is a front view which shows the detailed structure of an image pick-up element. It is a front view of a focus detection pixel. It is sectional drawing of a focus detection pixel. It is a figure which shows the focus detection position on the imaging | photography screen of an interchangeable lens. It is a front view which shows the detailed structure of an image pick-up element. It is a front view which shows the detailed structure of an image pick-up element. It is a front view of a focus detection pixel.

  As an imaging apparatus according to an embodiment, an interchangeable lens digital still camera will be described as an example. FIG. 1 is a cross-sectional view showing a configuration of a digital still camera according to an 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 unit 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. Further, transmission of lens information and reception of camera information (defocus amount, aperture value, etc.) are performed 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. In the imaging element 212, imaging pixels are two-dimensionally arranged, and focus detection pixels are incorporated in portions corresponding to focus detection positions (focus detection areas). 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 an image signal and a focus detection signal, focus detection calculation based on the focus detection signal, and focus adjustment of the interchangeable lens 202, and the image signal Processing and recording, and operation control of the digital still camera 201 are performed. The body drive control device 214 communicates with the lens drive control device 206 through the electrical contact 213 to receive lens information and transmit 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 by the imaging element 212 on the liquid crystal display element 216, and the photographer can observe the through image through the eyepiece lens 217. The memory card 219 is an image storage that stores an image captured by the image sensor 212.

  A subject image is formed on the light receiving surface of the image sensor 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 an image signal and a focus detection signal are sent to the body drive control device 214.

  The body drive control device 214 calculates the defocus amount based on the focus detection signal from the focus detection pixel of the image sensor 212 and sends the defocus amount to the lens drive control device 206. The body drive control device 214 processes the image signal from the image sensor 212 to generate image data, stores the image data in the memory card 219, and transmits the through image signal from the image sensor 212 to the liquid crystal display element drive circuit 215. 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 a lookup prepared in advance. Lens information corresponding to the lens position and aperture value is selected from the 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.

  FIG. 2 is a diagram showing a focus detection position (focus detection area) on the shooting screen of the interchangeable lens 202, and an image is sampled on the shooting screen when a focus detection pixel column on the image sensor 212 described later performs focus detection. An example of a region (focus detection area, focus detection position) to be performed is shown. 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, and 103, focus detection pixels are arranged in the horizontal direction, and in the focus detection areas 104 and 105, focus detection pixels are arranged in the vertical direction.

  3 and 4 are front views showing a detailed configuration of the image sensor 212. FIG. 3 shows details of the pixel array in which the vicinity of the focus detection areas 101, 102, 103 in FIG. 2 is enlarged, and FIG. 4 shows details of the pixel array in which the vicinity of the focus detection areas 104, 105 in FIG. Show. Imaging pixels 310 are densely arranged on the imaging element 212 in a two-dimensional square lattice pattern. 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. In FIG. 4, focus detection pixels 313 and 314 for vertical focus detection having the same pixel size as that of the imaging pixel 310 for focus detection in the vertical direction are alternately arranged, and originally green pixels and blue pixels are continuously arranged. Arranged continuously on a vertical straight line to be done. Similarly, in FIG. 3, focus detection pixels 315 and 316 for horizontal focus detection having the same pixel size as the imaging pixels for horizontal focus detection are alternately arranged, and originally green pixels and blue pixels are continuously formed. They are arranged continuously on a horizontal straight line to be arranged.

  FIG. 5 is a diagram illustrating the shape of the microlens 10 of the imaging pixel 310 and the focus detection pixels 313, 314, 315, and 316. The shape of the microlens 10 of the imaging pixel 310 and the focus detection pixels 313, 314, 315, and 316 is originally a shape cut out from a circular microlens 9 larger than the pixel size in a square shape corresponding to the pixel size. . The cross section in the direction of the diagonal line passing through the optical axis of the microlens 10 and the cross section in the direction of the horizontal line passing through the optical axis of the microlens 10 have shapes shown in FIGS.

  As shown in FIG. 6, the imaging pixel 310 includes a rectangular microlens 10, a photoelectric conversion unit 11 whose light receiving area is limited to a square by a light shielding mask described later, and a color filter (not shown). There are three types of color filters, red (R), green (G), and blue (B). Each spectral sensitivity has the characteristics shown in FIG. In the image pickup device 212, image pickup pixels 310 having respective color filters are arranged in a Bayer array.

  The focus detection pixels 313, 314, 315, and 316 are provided with white filters that transmit all visible light in order to perform focus detection for all colors. The spectral sensitivity characteristics of the white filters are shown in FIG. It becomes the characteristic to show. That is, the spectral sensitivity characteristic is obtained by adding the spectral sensitivity characteristics of the green pixel, the red pixel, and the blue pixel shown in FIG. 8, and the light wavelength region corresponding to such spectral sensitivity characteristic is the green pixel, the red pixel, and the blue pixel. Includes a light wavelength region exhibiting high spectral sensitivity.

  FIG. 7 is a front view of the focus detection pixels 313, 314, 315, and 316. As shown in FIG. 7A, the focus detection pixel 313 is limited to the upper half of a square (upper half when the square is divided into two equal parts by a horizontal line) with a rectangular microlens 10 and a light shielding mask described later. And a photoelectric filter 13 and a white filter (not shown).

  In addition, as shown in FIG. 7B, the focus detection pixel 314 has a light receiving area in the lower half of the square (lower half when the square is divided into two equal parts by a horizontal line) using a rectangular microlens 10 and a light shielding mask described later. It is composed of a restricted photoelectric conversion unit 14 and a white filter (not shown).

  When the focus detection pixel 313 and the focus detection pixel 314 are displayed so as to overlap each other with the microlens 10 as a reference, the photoelectric conversion units 13 and 14 whose light receiving areas are limited by the light shielding mask are arranged in the vertical direction.

  7A and 7B, when the remaining part (broken line part) obtained by halving the square is added to the light receiving area part obtained by halving the square, a square having the same size as the light receiving area of the imaging pixel 310 is obtained. Become.

  As shown in FIG. 7 (c), the focus detection pixel 315 has a light receiving area divided into a left half of a square (a left half when a square is divided into two equal parts by a vertical line) using a rectangular microlens 10 and a light shielding mask described later. It is composed of a limited photoelectric conversion unit 15 and a white filter (not shown).

  Further, as shown in FIG. 7D, the focus detection pixel 316 includes a rectangular microlens 10 and a light shielding mask, which will be described later, in which the light receiving region is a right half of a square (a right half when a square is divided into two equal parts by a vertical line). ) And a white color filter (not shown).

  When the front view of the focus detection pixel 315 and the front view of the focus detection pixel 316 are displayed so as to overlap each other with the microlens 10 as a reference, the photoelectric conversion units 15 and 16 in which the light receiving area is limited by the light shielding mask are arranged in the horizontal direction. Yes.

  7C and 7D, when the remaining part (broken line part) obtained by halving the square is added to the light receiving area part obtained by halving the square, a square having the same size as the light receiving area of the imaging pixel 310 is obtained. Become.

  FIG. 10 is a cross-sectional view of the image pickup pixel 310 when the cross section of the image pickup pixel array is taken along a straight line in the vertical direction. In the imaging pixel 310, a light shielding mask 30 is formed in proximity to the imaging photoelectric conversion unit 11, and the photoelectric conversion unit 11 receives light that has passed through the opening 30 a of the light shielding mask 30. A planarizing layer 31 is formed on the light shielding mask 30, and a color filter 38 is formed thereon. A planarizing layer 32 is formed on the color filter 38, and the microlens 10 is formed thereon. The shape of the opening 30 a is projected forward by the microlens 10. The photoelectric conversion unit 11 is formed on the semiconductor circuit substrate 29.

  FIG. 11 is a cross-sectional view of the focus detection pixels 313 and 314 when a cross section of the focus detection pixel array including the focus detection pixels 313 and 314 is taken along a straight line in the vertical direction. In the focus detection pixels 313 and 314, a light shielding mask 30 is formed in proximity to the focus detection photoelectric conversion units 13 and 14, and the photoelectric conversion units 13 and 14 pass through the openings 30 b and 30 c of the light shielding mask 30. Is received. A planarizing layer 31 is formed on the light shielding mask 30, and a white filter 34 is formed thereon. A planarizing layer 32 is formed on the white filter 34, and the microlens 10 is formed thereon. The shapes of the openings 30b and 30c are projected forward by the microlens 10. The photoelectric conversion units 13 and 14 are formed on the semiconductor circuit substrate 29.

  The structure of the focus detection pixels 315 and 316 is only the structure of the focus detection pixels 313 and 314 rotated by 90 degrees, and is basically the same as the structure of the focus detection pixels shown in FIG.

  FIG. 12 is a diagram for explaining the state of the imaging light beam received by the imaging pixel 310 shown in FIGS. 3, 4, and 10, and takes a cross-section of the imaging pixel array along a straight line in the vertical direction.

  The photoelectric conversion units 11 of all the imaging pixels 310 arranged on the image sensor 212 receive the light flux that has passed through the opening 30 a of the light shielding mask 30 disposed in the vicinity of the photoelectric conversion unit 11. The shape of the opening 30a of the light shielding mask 30 is projected by the microlens 10 of each imaging pixel 310 onto a region 95 common to all the imaging pixels on the exit pupil 90 that is separated from the microlens 10 by the distance measurement pupil distance d.

  Accordingly, the photoelectric conversion unit 11 of each imaging pixel 310 receives the imaging light flux 71 that passes through the region 95 and the microlens 10 of each imaging pixel 310, and performs imaging that passes through the region 95 toward the microlens 10 of each imaging pixel 310. A signal corresponding to the intensity of the image formed on each microlens 10 by the light beam 71 is output.

  FIG. 13 is a diagram for explaining the state of the focus detection light beam received by the focus detection pixels 313 and 314 shown in FIGS. 4 and 11 in comparison with FIG. 12, and the focus detection pixel array is represented by a straight line in the vertical direction. The cross section is taken.

  The photoelectric conversion units 13 and 14 of all the focus detection pixels arranged on the image sensor 212 pass the light beams that have passed through the openings 30b and 30c of the light shielding mask 30 disposed in proximity to the photoelectric conversion units 13 and 14. Receive light. The shape of the opening 30b of the light shielding mask 30 is an area 93 common to all focus detection pixels 313 on the exit pupil 90 separated from the microlens 10 by the distance measurement pupil distance d by the microlens 10 of each focus detection pixel 313. Projected. Similarly, the shape of the opening 30c of the light shielding mask 30 is common to all the focus detection pixels 314 on the exit pupil 90 separated from the microlens 10 by the distance measurement pupil distance d by the microlens 10 of each focus detection pixel 314. Projected onto area 94. The pair of areas 93 and 94 is called a distance measuring pupil.

  Therefore, the photoelectric conversion unit 13 of each focus detection pixel 313 receives the focus detection light beam 73 that passes through the distance measurement pupil 93 and the microlens 10 of each imaging pixel 310, passes through the distance measurement pupil 93, and passes through the distance detection pupil 93. A signal corresponding to the intensity of the image formed on each microlens 10 is output by the focus detection light beam 73 toward the microlens 10. The photoelectric conversion unit 14 of each focus detection pixel 314 receives the focus detection light beam 74 that passes through the distance measurement pupil 94 and the microlens 10 of each image pickup pixel 310, passes through the distance measurement pupil 94, and each image pickup pixel 310. A signal corresponding to the intensity of the image formed on each microlens 10 is output by the focus detection light beam 74 toward the microlens 10.

  In the region where the distance measuring pupils 93 and 94 on the exit pupil 90 through which the focus detection light beams 73 and 74 received by the pair of focus detection pixels 313 and 314 pass is integrated, the shooting light beam 71 received by the imaging pixel 310 passes through the exit. It coincides with the region 95 on the pupil 90. On the exit pupil 90, the focus detection light beams 73 and 74 are in a complementary relationship with the photographic light beam 71.

  A large number of the pair of focus detection pixels 313 and 314 described above are alternately and linearly arranged. By combining the outputs of the photoelectric conversion units 13 and 14 of the focus detection pixels 313 and 314 into a pair of output groups corresponding to the distance measuring pupil 93 and the distance measuring pupil 94, the distance measuring pupil 93 and the distance measuring pupil 94 are respectively passed. Information on the intensity distribution of the pair of images formed by the pair of luminous fluxes formed on the focus detection pixel array (vertical direction) is obtained. By applying an image shift detection calculation process (correlation calculation process, phase difference detection process) described later to this information, the image shift amount of a pair of images is detected by a so-called pupil division type phase difference detection method. 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, the deviation between the planned image formation surface and the image formation surface at the focus detection position (vertical direction) is performed. (Defocus amount) is calculated.

  The focus detection light beams received by the focus detection pixels 315 and 316 are also obtained by simply rotating the pair of focus detection light beams 73 and 74 received by the focus detection pixels 313 and 314 by 90 degrees, and basically the focus detection light beams shown in FIG. 73 and 74, a pair of distance measurement pupils obtained by rotating the distance measurement pupils 93 and 94 by 90 degrees are set. A large number of pairs of focus detection pixels 315 and 316 are arranged alternately and linearly. By combining the outputs of the photoelectric conversion units 15 and 16 of the focus detection pixels 315 and 316 into a pair of output groups corresponding to the pair of distance measurement pupils, a pair of light fluxes passing through the pair of distance measurement pupils are converted into focus detection pixels. Information on the intensity distribution of a pair of images formed on the array (horizontal direction) is obtained. Based on this information, the deviation (defocus amount) between the planned imaging plane and the imaging plane at the focus detection position (horizontal direction) is calculated.

  The image sensor 212 is configured as a CMOS image sensor. FIG. 14 is a conceptual diagram of a circuit configuration of the image sensor 212.

  The circuit configuration of the image sensor 212 will be described in a simplified manner with a layout of 8 pixels in the horizontal direction and 4 pixels in the vertical direction. FIG. 14 is drawn corresponding to the focus detection areas 101, 102, and 103 in the horizontal direction of FIG. 2, and the focus detection pixels 315 and 316 are arranged in the same row in the horizontal direction. In the focus detection areas 104 and 105 in the vertical direction, focus detection pixels 313 and 314 are arranged in the vertical direction and in different rows.

  In the second row, focus detection pixels 315 and 316 are arranged. In FIG. 14, the four focus detection pixels 315 and 316 at the center indicated by “◯” are shown as representative of a plurality of focus detection pixels, and two left and right imaging pixels 310 (indicated by “□”). ) Is shown representatively of a plurality of imaging pixels arranged on the left and right of the focus detection pixel.

  Only the imaging pixels 310 are arranged in the first, third, and fourth lines. In FIG. 14, the imaging pixels 310 in the first row, the third row, and the fourth row are shown as representative rows including a plurality of imaging pixels above and below the row in which the focus detection pixels are arranged.

  In FIG. 14, a line memory 320 is a buffer that samples and holds pixel signals of pixels for one row and temporarily holds them, and a vertical scanning circuit outputs pixel signals of the same row output to the vertical signal line 501. Sample and hold based on the control signal ΦH1 to be emitted. The pixel signal held in the line memory 320 is reset in synchronization with the rise of the control signals ΦS1 to ΦS4.

  Output of pixel signals from the imaging pixel 310 and the focus detection pixels 315 and 316 is independently controlled for each row by a control signal (ΦS1 to ΦS4) generated by the vertical scanning circuit. The pixel signals of the pixels in the row selected by the control signals (ΦS1 to ΦS4) are output to the vertical signal line 501.

  The pixel signals held in the line memory 320 are sequentially transferred to the output circuit 330 by the control signals (ΦV1 to ΦV8) generated by the horizontal scanning circuit, and are amplified by the set amplification degree in the output circuit 330 to be externally transmitted. Is output.

  The imaging pixel 310 and the focus detection pixels 315 and 316 are reset by the control signals (ΦR1 to ΦR4) generated by the vertical scanning circuit after the pixel signal is sampled and held, and the next pixel is detected at the falling edge of the control signals ΦR1 to ΦR4. Charge accumulation for signal output is started.

  The control signal φSync is a vertical synchronization signal and is output to the outside for each frame. Further, control signals ΦS1 to ΦS4 and control signals ΦR1 to ΦR4 are also output to the outside.

  FIG. 15 is a detailed circuit diagram of the imaging pixel 310 and the focus detection pixels 315 and 316 of the imaging device 212 shown in FIG. The photoelectric conversion unit is composed of a photodiode (PD). The charge accumulated in the PD is accumulated in a floating diffusion layer (floating diffusion: FD). The FD is connected to the gate of the amplification MOS transistor (AMP), and the AMP generates a signal corresponding to the amount of charge accumulated in the FD.

  The FD portion 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 (ΦR1 to ΦR3), the charges accumulated in the FD and PD are cleared and the reset state is set.

  The output of AMP is connected to a vertical output line 501 through a row selection MOS transistor 512. When the row selection MOS transistor 512 is turned on by the control signal ΦSn (ΦS1 to ΦS3), the output of the AMP is output to the vertical output line 501.

  FIG. 16 is an operation timing chart of the image sensor 212 shown in FIG. In the CMOS image sensor, pixel drive readout, that is, reset, exposure, and readout of pixel signals are sequentially performed for each row as described below by a so-called rolling shutter operation. A vertical synchronization signal φSync is generated in synchronization with the output of all pixel signals from the image sensor 212 (output of image signals for one frame).

  The imaging pixel 310 in the first row is selected by a control signal ΦS1 generated by the vertical scanning circuit in synchronization with the vertical synchronization signal φSync, and the pixel signal of the selected imaging pixel 310 is output to the vertical signal line 501. The pixel signal of the first row output to the vertical signal line 501 by the control signal ΦH1 generated in synchronization with the control signal ΦS1 is temporarily held in the line memory 320. The pixel signals of the imaging pixels 310 in the first row held in the line memory 320 are transferred to the output circuit 330 according to the control signals ΦV1 to ΦV8 sequentially issued from the horizontal scanning circuit, and the set amplification degree is set in the output circuit 330. Is amplified and output to the outside.

  When the transfer of the pixel signal of the imaging pixel 310 in the first row to the line memory 320 is completed, the imaging pixel 310 in the first row is reset by the control signal ΦR1 issued from the reset circuit, and at the falling edge of the control signal ΦR1. The next charge accumulation of the imaging pixels 310 in the first row is started.

  When the output of the pixel signal of the imaging pixel 310 in the first row from the output circuit 330 is completed, the imaging pixel 310 and the focus detection pixels 315 and 316 in the second row are selected by the control signal ΦS2 generated by the vertical scanning circuit. Then, the pixel signal of the selected imaging pixel 310 is output to the vertical signal line 501.

  Thereafter, the pixel signals of the imaging pixels 310 and the focus detection pixels 315 and 316 in the second row are similarly held, the imaging pixels 310 are reset, the pixel signals are output, and the next charge accumulation is started. Subsequently, the pixel signals of the imaging pixels 310 in the third row and the fourth row are held, the imaging pixels 310 are reset, the pixel signals of the imaging pixels 310 are output, and the next charge accumulation is started. When the output of the pixel signals of all the pixels is completed, the operation returns to the first row again and the above operation is repeated periodically.

  The reset operation of the n-th imaging pixel 310 and the focus detection pixels 315 and 316 is performed during the time from the rise to the fall of the control signal φRn, and the exposure of the n-th imaging pixel 310 and the focus detection pixels 315 and 316 is performed. The operation is performed during the time (exposure time, accumulation time) from the falling edge of the control signal φRn to the rising edge of the control signal φSn. The signal readout operation of the imaging pixels 310 and the focus detection pixels 315 and 316 in the n-th row is as follows. The time is from the rise of the control signal φSn to the rise of the control signal φSn + 1.

  FIG. 17 is a flowchart showing the imaging operation of the digital still camera 201. When the power of the digital still camera 201 is turned on in step S100, the body drive control device 214 starts an imaging operation after step S110. In step S110, the image sensor 212 is set to an operation mode (for example, outputting 60 frames per second) that repeats the imaging operation at a constant cycle. Then, all pixel data for one frame is read out. In the subsequent step S120, data obtained by partially thinning out the data of the imaging pixel 310 is displayed on the liquid crystal display element 216 (live view display). In step S130, focus detection is performed in the five focus detection areas 101 to 105 based on the data of the focus detection pixels 313, 314, 315, and 316, and finally one defocus amount is calculated. When the reliability of the defocus amount is low, or when the defocus amount cannot be calculated, the focus cannot be detected. Details of the defocus amount calculation processing in step S130 will be described later.

  In step S140, 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 focus is not close, the process proceeds to step S150, the defocus amount is transmitted to the lens drive control device 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 S140 that the focus is close, the process proceeds to step S160, 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 S170, 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 (F set by the photographer or automatically). Value). When the aperture control is completed, the image pickup device 212 is caused to perform an image pickup operation with an exposure time corresponding to the subject luminance, and image data is acquired from the image pickup pixel 310 of the image pickup device 212 and all the focus detection pixels 313, 314, 315, and 316. read out.

  In step S180, the data of the virtual imaging pixels at the respective pixel positions of the focus detection pixel row are changed to the data of the imaging pixels 310 around the focus detection pixels 313, 314, 315, and 316 and the focus detection pixels 313, 314, 315, and 316. Pixel interpolation is performed based on the data. In the subsequent step S190, image data composed of the data of the imaging pixel 310 and the interpolated virtual imaging pixel data is stored in the memory card 219, and the process returns to step S110 to repeat the above-described operation.

  The body drive control device 214 detects subject brightness in real time according to the output of a photometric sensor (not shown). An aperture adjustment command is sent to the lens drive controller 206 in parallel during the live view display operation period (loop operation from step S110 to step S160) so that the pixel signal has an appropriate level according to the detection result. To adjust the aperture diameter. Accordingly, the aperture diameter may change even during the exposure period for one frame.

  Next, details of general image shift detection calculation processing (correlation calculation processing, phase difference detection processing) used in step S130 of FIG. 17 will be described. For the sake of simplicity, processing for the focus detection pixel array in one focus detection area will be described, but processing in other focus detection areas is the same.

  In the pair of images detected by the focus detection pixels 313 and 314 or the focus detection pixels 315 and 316, the distance measurement pupil may be vignetted by the aperture of the lens and the light amount balance may be lost. Is subjected to a correlation calculation capable of maintaining the image shift detection accuracy.

For a pair of data strings (A1 _{1 to} A1 _M , A2 _{1 to} A2 _M : M is the number of data) read out from the focus detection pixel string, a correlation calculation formula (1 ) To calculate the correlation amount C (k).
C (k) = Σ | A1 n × A2 n + 1 + k -A2 n + k × A1 n + 1 | (1)

In equation (1), the Σ operation is accumulated for n, but the range taken by n is limited to a range in which data of A1 _n , A1 _{n + 1} , A2 _{n + k} , A2 _{n + 1 + k} exists according to the image shift amount k. . The image shift amount k is an integer and is a relative shift amount with the data interval of the data string as a unit.

As shown in FIG. 18A, the calculation result of the expression (1) indicates that the correlation amount C (k) is the amount of shift with high correlation between a pair of data (k = k _j = 2 in FIG. 18A). Minimal (the smaller the value, the higher the degree of correlation).

The shift amount k _s that gives the minimum value C (k _s ) with respect to the continuous correlation amount is obtained using the three-point interpolation method according to equations (2) to (5).
k _s = k _j + D / SLOP (2)
C (k _s ) = C (k _j ) − | D | (3)
D = {C (k _j −1) −C (k _j +1)} / 2 (4)
SLOP = MAX {C ( _kj + 1) -C ( _kj ), C ( _kj- 1) -C ( _kj )}
(5)

Whether or not the shift amount k _s calculated by Expression (2) is reliable is determined as follows. As shown in FIG. 18 (b), when a low level of correlation between the pair of data, the value of the minimum value C of the interpolated correlation quantity (k _s) is increased. Therefore, when C (k _s ) is equal to or greater than a predetermined threshold, it is determined that the reliability of the calculated shift amount is low, and the calculated shift amount k _s is canceled.

Alternatively, in order to normalize C (k _s ) with the contrast of data, when the value obtained by dividing C (k _s ) by SLOP that is proportional to the contrast is equal to or greater than a predetermined value, the calculated shift amount It is determined that the reliability is low, and the calculated shift amount k _s is canceled.

Alternatively, when SLOP that is a value proportional to the contrast is equal to or smaller than a predetermined value, it is determined that the subject has low contrast and the reliability of the calculated shift amount is low, and the calculated shift amount k _s is canceled. .

As shown in FIG. 18 (c), the low level of correlation between the pair of data when there is no drop in correlation quantity C (k) is between the shift amount in the range _k min _{to k max,} the minimum value C _{(k s} In such a case, it is determined that the focus cannot be detected.

If it is determined that the calculated shift amount k _s is reliable, it is converted into the image shift amount shft by Equation (6). In Expression (6), PY is twice the pixel pitch (detection pitch) of the focus detection pixels 313 and 314 or the focus detection pixels 315 and 316.
shft = PY × k _s (6)

The image shift amount calculated by Expression (6) is multiplied by a predetermined conversion coefficient Kd to convert it to a defocus amount def. The conversion coefficient Kd corresponds to the opening angle of the pair of light beams received by the focus detection pixels 313 and 314 or the focus detection pixels 315 and 316, and the distance measurement pupil distance d is defined as the center-of-gravity interval between the pair of distance measurement pupils. The value divided by. Note that the conversion coefficient Kd changes according to the aperture diameter of the diaphragm because the distance between the centers of gravity of the distance measurement pupils changes according to the aperture diameter.
def = Kd × shft (7)

  FIG. 19 shows an image shift amount (relative displacement amount of a pair of images in a direction perpendicular to the optical axis of the optical system) and a defocus amount (actual image with respect to an imaging surface serving as a reference surface in the optical axis direction of the optical system). It is explanatory drawing in the case of converting to (surface deviation amount).

Reference numeral 110 denotes an imaging surface, reference numeral 140 denotes an image plane, reference numeral 125 denotes a diaphragm surface, and reference numeral 91 denotes an optical axis. A symbol def represents a defocus amount (a distance from the imaging surface 110 to the image surface 140), and a distance PO represents a distance from the imaging surface 110 to the diaphragm surface 125. A position G1 and a position G2 are positions where the central light beams of the pair of focus detection light beams 73 and 74 when the diaphragm F value is Fc intersect each other, and positions G3 and G4 have a diaphragm F value Fd (<Fc). In this case, each of the pair of focus detection light beams 73 and 74 represents a position where the central light beam intersects the diaphragm surface. The distance Q1 is the distance between the position G1 and the position G2, the distance Q2 is the distance between the position G3 and the position G4, the code S1 is the image shift amount of a pair of images when the aperture F value is Fc, and the code S2 is This represents the image shift amount of a pair of images when the aperture F value is Fd. The angle θ1 is the opening angle of the central beam of the pair of focus detection beams 73 and 74 when the aperture F value is Fc, and the angle θ2 is the opening of the center beam of the pair of focus detection beams 73 and 74 when the aperture F value is Fd. Suppose that it is a corner. Although the distance PO varies depending on the type of the interchangeable lens 202, the average distance is set substantially equal to the distance measuring pupil distance d in FIG. When the defocus amount def is small compared to the distance PO (that is, when it can be approximated as PO−def≈PO), the defocus amount def when the aperture F value is Fc is calculated by Expression (8). .
def = S1 / (2 · tan (θ1 / 2)) = S1 · PO / Q1 (8)

Therefore, the conversion coefficient Kd ₁ when the aperture F value is Fc is expressed by Expression (9).
Kd ₁ = 1 / (2 · tan (θ1 / 2)) = PO / Q1 (9)

Similarly, the defocus amount def and the conversion coefficient Kd ₂ when the aperture F value is Fd (> Fc) are calculated by equations (10) and (11).
def = S2 / (2 · tan (θ2 / 2)) = S2 · PO / Q2 (10)
Kd ₂ = 1 / (2 · tan (θ2 / 2)) = PO / Q2 (11)

  A conversion coefficient Kd corresponding to the aperture F value is stored as lens information on the interchangeable lens 202 side. When the image shift amount shft calculated with a certain aperture F value is converted into the defocus amount def, the aperture The conversion coefficient Kd corresponding to the F value is used.

  Details of the processing in step S130 in FIG. 17 will be described with reference to FIG. As described above, the aperture diameter may change even during the operation of one frame of the image sensor. In the CMOS image sensor, if the aperture diameter changes during the rolling shutter operation, the exposure timing differs for each row, so that there is a possibility that a defect may occur in focus detection.

  For this reason, first, in step S200, it is checked whether or not the aperture diameter has changed during the exposure period when the data of the focus detection pixels 313, 314, 315, and 316 used thereafter is acquired. FIG. 21 is an operation timing chart in which time is elapsed on the horizontal axis, the aperture aperture diameter is shown on the upper stage, and the operation of the image sensor is shown on the lower stage. In FIG. 21, the aperture diameter of the diaphragm changes from F1.4 at time t1 to F5.6 at time t2 over approximately two frames (frames A and B).

  The image sensor 212 sequentially performs drive readout of all pixels, that is, reset of all pixels, exposure, and pixel signal readout for each row as shown in FIG. In FIG. 21, the number of rows is 10, and a focus detection area including horizontal focus detection pixels 315 and 316 is arranged on the fifth row (indicated by “R” in FIG. 21). A focus detection area including vertical focus detection pixels 313 and 314 is arranged on the line.

  The lens drive control device 206 changes the aperture diameter as shown in FIG. 21 in response to a command from the body drive control device 214, but detects the aperture value in real time and controls the aperture value in the body drive. Feedback is provided to the device 214. Therefore, the body drive control device 214 monitors the value of the aperture opening diameter output from the lens drive control device 206 even during the imaging operation. If the value of the aperture opening diameter changes by a predetermined value or more during one frame period, exposure is performed. It is determined that the aperture diameter has changed during the period. For example, when focus detection is performed using focus detection pixel data read during the period of frame A (time t3 to t4), the difference between the aperture opening diameter at time t3 and the aperture opening diameter at time t4 is greater than or equal to a predetermined value. If it is, it is determined that there is a change in aperture opening diameter.

  If it is determined in step S200 that there is no change in the aperture diameter, in step S210, the defocus amount def in all the five focus detection areas 101 to 105 is calculated, and the reliable defocus amount is determined. The defocus amount indicating the shortest distance is adopted as the final defocus amount, and the process proceeds to step S140 in FIG.

  As the conversion coefficient Kd for calculating the defocus amount def, the conversion coefficient Kd corresponding to the aperture diameter at time t3 or time t4 is used.

  If it is determined in step S200 that there is a change in the aperture diameter, the defocus amount def in the two focus detection areas 104 and 105 in which the focus detection pixels 313 and 314 are arranged in the vertical direction is determined in step S220. The calculation is prohibited, and the defocus amount def is calculated only by the three focus detection areas 101 to 103 in which the focus detection pixels 315 and 316 are arranged in the horizontal direction. When the focus detection pixels 313 and 314 are arranged in the vertical direction, if the aperture diameter changes, the exposure timing and exposure amount differ for each row, and the conversion coefficient Kd also differs for each row. The conversion error when calculating the focus amount becomes large. In order to prevent this, calculation of the defocus amount def in the vertical focus detection areas 104 and 105 is prohibited when the aperture diameter of the diaphragm changes. On the other hand, when the focus detection pixels 315 and 316 are arranged in the horizontal direction, even when the aperture diameter of the aperture is changed in the same row, the exposure timing and the exposure amount are the same, so that accurate focus detection is possible. However, since the aperture diameter is different for each row, the aperture diameter at the midpoint of the exposure time of each row where the three focus detection areas where the horizontal focus detection pixels 315 and 316 are arranged is detected, The image shift amount shft in the three focus detection areas 101 to 103 in the horizontal direction is converted into the defocus amount def, respectively, according to the conversion coefficient Kd corresponding to the detected aperture diameter.

  For example, in FIG. 21, a case will be described in which the image shift amount shft based on the focus detection pixel data of the focus detection pixels 315 and 316 arranged in the fifth row of the image sensor 212 is converted into the defocus amount def. The image shift amount shft based on the focus detection pixel data acquired in the frame A is obtained by using the conversion coefficient Kd corresponding to the aperture diameter Fa detected at the middle point ta of the exposure time of the fifth row of the frame A. The defocus amount is changed to def. Further, the image shift amount shft based on the focus detection pixel data acquired in the frame B uses a conversion coefficient corresponding to the aperture diameter Fb detected at the middle point tb of the exposure time of the fifth row of the frame B. To the defocus amount def. In this way, an accurate defocus amount def can be calculated based on the focus detection pixel data of the focus detection pixels 315 and 316 arranged in the horizontal direction in different rows.

  In step S220, the defocus amount def is calculated only in the three focus detection areas 101 to 103 in the horizontal direction as described above, and the defocus amount indicating the shortest distance among the reliable defocus amounts is finally determined. As a defocus amount, the process proceeds to step S140 in FIG.

  In the embodiment described above, a change in the aperture diameter during the rolling shutter operation of the CMOS image sensor in which the focus detection pixels are arranged in the horizontal direction (the same row) and the vertical direction (the same column) is detected, and When there is a change, focus detection based on the signal of the focus detection pixels arranged in the vertical direction is prohibited, so that it is possible to prevent a focus detection malfunction caused by a change in aperture diameter. In addition, when there is a change in the aperture diameter, the image shift amount based on the signal of the focus detection pixel arranged in the horizontal direction depends on the aperture diameter at the exposure timing at which the signal of the focus detection pixel is acquired. Since the conversion factor is used to convert the defocus amount, an accurate defocus amount can be calculated regardless of a change in the aperture diameter.

-Modification-
<Each focus detection pixel has a pair of light receiving regions>
In the partial enlarged view of the image sensor 212 shown in FIGS. 3 and 4, an example is shown in which a pair of focus detection pixels 313 and 314 and a pair of focus detection pixels 315 and 316 each having one photoelectric conversion unit are provided. A pair of photoelectric conversion units may be provided in one focus detection pixel. FIGS. 22 and 23 are partial enlarged views of the image sensor 212 corresponding to FIGS. 3 and 4. The focus detection pixels 311 and 312 include a pair of photoelectric conversion units.

  The focus detection pixel 311 shown in FIG. 24A functions as a pair of the focus detection pixel 313 and the focus detection pixel 314 shown in FIGS. 7A and 7B, and the focus detection pixel shown in FIG. The detection pixel 312 performs a function corresponding to a pair of the focus detection pixel 315 and the focus detection pixel 316 shown in FIGS. The focus detection pixels 311 and 312 include a microlens 10, a pair of photoelectric conversion units 13 and 14, and a pair of photoelectric conversion units 15 and 16 as illustrated in FIGS. 24A and 24B. White filters are arranged in the focus detection pixels 311 and 312, and the spectral sensitivity characteristics of the focus detection pixels 311 and 312 are a spectrum obtained by combining the spectral sensitivity of a photodiode that performs photoelectric conversion and the spectral sensitivity characteristics of an infrared cut filter (not shown). Sensitivity characteristics (see FIG. 9) are obtained. That is, the spectral sensitivity characteristic is obtained by adding the spectral sensitivity characteristics of the green pixel, the red pixel, and the blue pixel shown in FIG. The optical wavelength region in which the pixel and the blue pixel exhibit high spectral sensitivity is included.

  FIG. 25 is a cross-sectional view of the focus detection pixel 311 shown in FIG. 24A, in which a light shielding mask 30 is formed in proximity to the photoelectric conversion units 13 and 14, and the photoelectric conversion units 13 and 14 are Light that has passed through the opening 30d of the light shielding mask 30 is received. A planarizing layer 31 is formed on the light shielding mask 30, and a white filter 34 is formed thereon. A planarizing layer 32 is formed on the white filter 34, and the microlens 10 is formed thereon. The shape of the photoelectric conversion units 13 and 14 limited to the opening 30d by the microlens 10 is projected forward to form a pair of distance measuring pupils. The photoelectric conversion units 13 and 14 are formed on the semiconductor circuit substrate 29.

  The structure of the focus detection pixel 312 is only the structure of the focus detection pixel 311 rotated by 90 degrees, and is basically the same as the structure of the focus detection pixel shown in FIG.

<Focus detection pixel arrangement in a 45-degree direction>
FIG. 26 is a diagram illustrating a focus detection position (focus detection area) on the imaging screen of the interchangeable lens 202, and an area in which an image is sampled on the imaging screen when the focus detection pixel row on the image sensor 212 performs focus detection. An example of (focus detection area, focus detection position) is shown. In this example, focus detection areas 101 to 105 are arranged at five locations on the rectangular shooting screen 100 and up and down, left and right, and focus detection areas 106 to 109 are arranged in the diagonal direction of the shooting screen 100. In the focus detection areas 106 to 109, the focus detection pixels are linearly arranged in the longitudinal direction of the focus detection area indicated by a rectangle in the direction of 45 degrees obliquely upward to the right or 45 degrees obliquely upward.

  FIGS. 27 and 28 are front views showing a detailed configuration of the image sensor 212, and show the vicinity of the focus detection areas 106 and 108 and the focus detection areas 107 and 109 on the image sensor 212 in an enlarged manner. Imaging pixels 310 are densely arranged on the imaging element 212 in a two-dimensional square lattice pattern. 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. At the positions corresponding to the focus detection areas 106 and 108, focus detection pixels 323 and 324 having the same pixel size as the imaging pixel 310 and provided with a white filter are originally alternately arranged with green pixels. It is continuously arranged on a straight line in the direction of 45 degrees to the right. At the same time, at the positions corresponding to the focus detection areas 107 and 109, the focus detection pixels 325 and 326 having the same pixel size as that of the imaging pixel 310 and provided with the white filter are alternately continuously green. They are arranged continuously on a straight line in the direction of 45 degrees obliquely to the left. The focus detection pixels 323 and 324 and the focus detection pixels 325 and 326 are arranged at pixel positions where green pixels are originally arranged.

  As shown in FIG. 29A, the focus detection pixel 323 has a rectangular microlens 10 and a light-shielding mask 30 that divide the light-receiving region into a half of a square (the square is divided into two equal parts by a diagonal line in the 45 ° upward direction). The photoelectric conversion unit 23 is limited to a half and a white filter (not shown).

  In addition, as shown in FIG. 29B, the focus detection pixel 324 has a rectangular microlens 10 and a light-shielding mask 30 and divides the light-receiving region into half a square (a square is divided into two equal parts by a diagonal line in the 45 ° upward direction). The lower left half) of the photoelectric conversion unit 24 and a white filter (not shown).

  When the focus detection pixel 323 and the focus detection pixel 324 are displayed so as to overlap each other with the microlens 10 as a reference, the photoelectric conversion units 23 and 24 in which the light receiving area is limited by the light shielding mask are arranged in a 45 ° upward diagonal direction. .

  In FIGS. 29A and 29B, when the remaining part (broken line part) obtained by halving the square is added to the light receiving area part obtained by halving the square, a square having the same size as the light receiving area of the imaging pixel 310 is obtained. Become.

  As shown in FIG. 29 (c), the focus detection pixel 325 includes a rectangular microlens 10 and a light shielding mask 30, and the light receiving region is half a square (upper left in the case where the square is divided into two equal parts by a diagonal line in the 45 ° upward direction). The photoelectric conversion unit 25 is limited to a half and a white filter (not shown).

  Further, as shown in FIG. 29 (d), the focus detection pixel 326 has a rectangular microlens 10 and a light-shielding mask that divides the light-receiving area into a half of a square (the square is divided into two equal parts by a diagonal line in the 45 ° upward direction). The photoelectric conversion unit 26 is limited to the lower half) and a white filter (not shown).

  When the focus detection pixel 325 and the focus detection pixel 326 are displayed so as to overlap each other with the microlens 10 as a reference, the photoelectric conversion units 25 and 26 whose light receiving areas are limited by the light shielding mask are arranged in a 45 ° upward diagonal direction. .

  29 (c) and 29 (d), when the remaining part (broken line part) obtained by halving the square is added to the light receiving area part obtained by halving the square, a square having the same size as the light receiving area of the imaging pixel is obtained. Become.

  In the image sensor 212 having the focus detection area arrangement as shown in FIG. 26, a change in the aperture diameter is detected during the rolling shutter operation of the CMOS image sensor. The focus detection based on the pixel signals of the focus detection pixels 313 and 314 belonging to the focus detection areas 104 and 105 arranged in FIG. At the same time, focus detection based on the pixel signals of the focus detection pixels 323 to 326 belonging to the focus detection areas 106 to 109 arranged in an oblique direction is also prohibited. This is because the focus detection pixels 323 to 326 belonging to the focus detection areas 106 to 109 arranged in the oblique direction are arranged in different rows, so that when the aperture change occurs during the rolling shutter operation, the focus detection pixels 323 to 326 are arranged between the focus detection pixels. This is because it is difficult to perform accurate focus detection because the exposure timing and exposure amount are different.

  In the embodiment described above, a change in the aperture diameter is detected during the rolling shutter operation of the CMOS image sensor (image sensor 212), and when there is a change in the aperture diameter, the focal points arranged in different rows. Focus detection based on the pixel signals of the detection pixels 313, 314, and 323 to 326 was prohibited. However, based on the pixel signals of the focus detection pixels 313, 314, and 323 to 326 arranged in different rows as compared with the focus detection based on the signals of the focus detection pixels 315 and 316 arranged in the same row in the horizontal direction. The priority order of focus detection may be lowered. That is, they are arranged in different rows only when the reliability of focus detection based on the pixel signals of the focus detection pixels 315 and 316 arranged in the same row in the horizontal direction is extremely low, or when focus detection is disabled. Focus detection based on the pixel signals of the focus detection pixels 313, 314, and 323 to 326 may be allowed.

  In the embodiment described above, a change in the aperture diameter is detected during the rolling shutter operation of the CMOS image sensor (imaging device 212) in which the focus detection pixels are arranged in the vertical direction and the horizontal direction. In this case, the focus detection based on the pixel signals of the focus detection pixels 313, 314, and 323 to 326 arranged in different rows is prohibited. In the focus detection based on the pixel signals of the focus detection pixels 315 and 316 arranged in the same row in the horizontal direction, the aperture aperture diameter is detected in synchronization with the exposure timing of the row, and the aperture aperture diameter is set according to the aperture aperture diameter. By converting the image shift amount shft into the defocus amount def using the conversion coefficient Kd, accurate focus detection can be performed. However, the focus detection pixels 315 and 316 belonging to one focus detection area arranged only in the same row in the horizontal direction detect a change in the aperture diameter during the rolling shutter operation of the CMOS image sensor, and the change in the aperture diameter. If there is, the following focus detection may be performed. That is, in the focus detection based on the pixel signals of the focus detection pixels 315 and 316 arranged in the same row in the horizontal direction, the aperture diameter is detected in synchronization with the exposure timing of the row, and the conversion corresponding to the aperture size is performed. By converting the image shift amount shft into the defocus amount def using the coefficient Kd, accurate focus detection can be achieved.

  In the embodiment described above, an example of a pupil-division type focus detection pixel is shown as the focus detection pixel. However, the focus detection pixel is not limited to this, and the focus detection pixel using another focus detection method is not limited thereto. The present invention can also be applied. For example, in another method for detecting the contrast of an image as a focus detection method, the focus detection pixel may be the same as that of the image sensor, and when the contrast in the row direction and the column direction is detected, the above-described pupil division type The same problem as when using focus detection pixels occurs.

  That is, when the aperture diameter changes during the rolling shutter operation, the focus detection pixels arranged in the column direction (same as the imaging pixels) have different exposure amounts at different exposure timings, so that an accurate contrast evaluation value Cannot be calculated. On the other hand, the focus detection pixels arranged in the row direction (same as the imaging pixels) have the same exposure amount at different and identical exposure timings, so that an accurate contrast evaluation value can be calculated and the calculated contrast value is reduced. If standardized by the aperture diameter (exposure amount), comparative evaluation of contrast evaluation values obtained in different frames becomes possible. Therefore, as in the above-described embodiment, when the aperture diameter changes during the rolling shutter operation, the calculation of the contrast evaluation value based on the pixel signals of the focus detection pixels arranged in the column direction is prohibited, and the row direction By calculating the contrast evaluation value based on the pixel signal of the focus detection pixel arranged at, it is possible to prevent a failure of the focus detection operation caused by a change in the aperture diameter during the rolling shutter operation.

  In the embodiment described above, a change in the aperture diameter is detected during the rolling shutter operation of the CMOS image sensor (image sensor 212), and when there is a change in the aperture diameter, the focal points arranged in different rows. Focus detection based on the pixel signal of the detection pixel was prohibited. However, in such a case, the focus detection calculation may be performed without prohibition, and the focus adjustment operation (lens drive) based on the focus detection result may be prohibited.

  In the embodiment described above, a change in the aperture diameter is detected during the rolling shutter operation of the CMOS image sensor (imaging device 212) in the live view display operation. The focus detection based on the pixel signal of the focus detection pixel arranged at the position is prohibited. However, in the case where the focus detection operation and the aperture control are performed simultaneously between the frames in the continuous shooting operation, a change in the aperture diameter is detected during the rolling shutter operation of the CMOS image sensor between the frames in the continuous shooting operation. When there is a change in the aperture diameter, focus detection based on pixel signals of focus detection pixels arranged in different rows may be prohibited.

  In the embodiment described above, a change in the aperture diameter is detected during the rolling shutter operation of the CMOS image sensor (image sensor 212) in the live view display operation for still image shooting. Focus detection based on pixel signals of focus detection pixels arranged in different rows is prohibited. However, when the focus detection operation and the aperture control are performed in parallel during moving image shooting, a change in the aperture opening diameter is detected during the rolling shutter operation of the CMOS image sensor during moving image shooting. If there is, focus detection based on pixel signals of focus detection pixels arranged in different rows may be prohibited.

  In the embodiment described above, a change in the aperture diameter is detected during the rolling shutter operation of the CMOS image sensor (image sensor 212), and when there is a change in the aperture diameter, the focal points arranged in different rows. Focus detection based on the detection pixel signal was prohibited. However, even when an ND (neutral density) filter is mechanically inserted into and retracted from the optical path of the imaging optical system in order to adjust the exposure amount of the image sensor 212, the focus detection pixels arranged in different rows are different from each other. Since different exposure amounts are obtained at different exposure timings, accurate focus detection cannot be performed. Therefore, as in the above-described embodiment, when the exposure amount changes due to insertion and withdrawal of the ND filter during the rolling shutter operation, it is based on the pixel signals of the focus detection pixels arranged in different rows. By prohibiting focus detection, it is possible to prevent problems in focus detection operation.

  In the image sensor 212 in the above-described embodiment, the focus detection pixels 313 to 316 and 323 to 326 are provided with white filters. However, in the case where the same color filter (for example, a green filter) as the image pickup pixel 310 is provided. The present invention can also be applied to.

  In the imaging device 212 in the above-described embodiment, an example in which the imaging pixel 310 includes a Bayer array color filter is shown. However, the configuration and arrangement of the color filters are not limited to this, and the present invention can be applied to arrangements other than the arrangement of complementary color filters (green: G, yellow: Ye, magenta: Mg, cyan: Cy) and the Bayer arrangement. Can be applied. Further, the present invention can also be applied to a monochrome image sensor that does not include a color filter.

  In the above-described embodiment, no optical element is disposed between the image sensor 212 and the photographing optical system, but a necessary optical element can be appropriately inserted. For example, an infrared cut filter, an optical low-pass filter, a half mirror, or the like may be installed.

  Note that the imaging apparatus is not limited to the digital still camera configured as described above in which the interchangeable lens is mounted on the camera body. For example, the present invention can 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.

9, 10 micro lens,
11, 13, 14, 15, 16, 23, 24, 25, 26 photoelectric conversion unit,
29 Semiconductor circuit board,
30 shading mask, 30a, 30b, 30c, 30d opening,
31, 32 Flattening layer, 34 White filter, 38 color filter,
71 Shooting beam, 73, 74 Focus detection beam,
90 Exit pupil, 91 Optical axis of interchangeable lens, 93, 94 Distance pupil, 95 area,
100 shooting screen,
101, 102, 103, 104, 105, 106, 107, 108, 109 Focus detection area,
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 driving circuit, 216 liquid crystal display element, 217 eyepiece,
219 memory card,
310 imaging pixels,
311, 312, 313, 314, 315, 316, 323, 324, 325, 326 focus detection pixels,
320 line memory, 330 output circuit, 501 vertical output line,
510 reset MOS transistor, 512 row selection MOS transistor

Claims (4)

First focus detection pixels having first and second photoelectric conversion units that receive the first and second light beams that have passed through the first and second pupil regions of the optical system are arranged in a first direction, The second focus detection pixel having the first and second photoelectric conversion units that receive the third and fourth light fluxes that have passed through the third and fourth pupil regions of the optical system is the first direction. An imaging device arranged in a different second direction and performing a rolling shutter operation in which reading of the first and second focus detection pixels is sequentially performed for each row in the first direction ;
The optical system based on signals from the first and second photoelectric conversion units of the first focus detection pixel or based on signals from the first and second photoelectric conversion units of the second focus detection pixel. A focus detection unit for detecting the focus state of
An aperture drive unit that drives the aperture to change the aperture value, and
The focus detection unit detects the focus state using the signals of the first and second photoelectric conversion units of the first focus detection pixel when the diaphragm is driven, and the second focus The focus detection apparatus which does not detect the said focus state using the signal of the said 1st and 2nd photoelectric conversion part of a detection pixel. The focus detection apparatus according to claim 1,
The imaging element has imaging pixels arranged in a two-dimensional shape,
The focus detection apparatus that sequentially reads out the first and second focus detection pixels and the image pickup pixels for each row in the first direction . The focus detection apparatus according to claim 1 or 2, wherein
The focus detection device, wherein the focus detection unit detects the focus state using a value corresponding to an aperture value of an exposure time of the first focus detection pixel when the aperture is driven . The focus detection apparatus according to claim 3,
An aperture value detection unit for detecting an aperture value changed by the aperture drive unit;
The focus detection unit is configured to detect the focus state based on an aperture value detected by the aperture value detection unit at an exposure time of the first focus detection pixel in the rolling shutter operation .

Images