JP5211590B2 - Image sensor and focus detection apparatus - Google Patents

Description

  The present invention relates to an imaging element, a focus detection device, and an imaging device.

  There is known a solid-state imaging device in which charge accumulation type focus detection pixels of a pupil division type phase difference detection system are two-dimensionally arranged (see, for example, Patent Document 1).

Prior art documents related to the invention of this application include the following.
JP 2002-314062 A

  However, in the above-described conventional solid-state imaging device, the charge accumulation time is uniformly controlled for all of the focus detection pixels arranged in a two-dimensional manner. On the contrary, there is a problem that the output of the focus detection pixel may be insufficient in a dark part, and the focus detection becomes partially impossible.

An image pickup device according to a first aspect of the present invention divides a rectangular area on a single semiconductor substrate into at least first and second partial rectangular areas having two orthogonal sides in common with a part of the sides of the rectangular area. In each of the first and second partial rectangular areas, each of the first and second partial rectangular areas is arranged in a two-dimensional manner in each of the first and second partial rectangular areas and has a focus detection pixel having a charge storage type photoelectric conversion unit. A first readout circuit and a second readout circuit that are arranged to read out the output of the focus detection pixel in the first partial rectangular area and the output of the focus detection pixel in the second partial rectangular area, respectively, A control circuit that controls the charge accumulation of the focus detection pixels in the partial rectangular region and the charge accumulation of the focus detection pixels in the second partial rectangular region independently of each other, and the first and second partial rectangles The regions are spaced apart from each other and the first The focus detection pixels in the partial rectangular area receive a pair of light beams that have passed through the first pair of areas of the pupil of the optical system, and output a pair of image signals. A first photoelectric conversion unit and arranged in the arrangement direction of the pair of first photoelectric conversion units, and the focus detection pixels of the second partial rectangular region are a second pair of pupils of the optical system. In addition to having a single microlens and a pair of second photoelectric conversion units so as to receive a pair of light beams that have passed through the region and output a pair of image signals, the arrangement direction of the pair of second photoelectric conversion units The alignment direction of the pair of first photoelectric conversion units of the focus detection pixels in the first partial rectangular area is arranged so that the pair of second photoelectric conversions of the focus detection pixels in the second partial rectangular area Unlike the arrangement direction of the units, the first readout circuit uses the first readout circuit. The readout of the focus detection pixel output in the partial rectangular area of each of the focus detection pixel columns arranged in the alignment direction of the pair of first photoelectric conversion units and the alignment direction of the pair of first photoelectric conversion units Reading of the focus detection pixel output of the second partial rectangular area by the second readout circuit is performed by scanning in the vertical direction, and the focal points arranged in the arrangement direction of the pair of second photoelectric conversion units. Scanning is performed in a direction perpendicular to the arrangement direction of the pair of second photoelectric conversion units for each pixel row for detection.
An image pickup device according to a second aspect of the present invention divides a rectangular area on a single semiconductor substrate into at least first and second partial rectangular areas having two orthogonal sides in common with a part of the sides of the rectangular area. In each of the first and second partial rectangular areas, each of the first and second partial rectangular areas is arranged in a two-dimensional manner in each of the first and second partial rectangular areas and has a focus detection pixel having a charge storage type photoelectric conversion unit. A first readout circuit and a second readout circuit that are arranged to read out the output of the focus detection pixel in the first partial rectangular area and the output of the focus detection pixel in the second partial rectangular area, respectively, A control circuit that controls the charge accumulation of the focus detection pixels in the partial rectangular region and the charge accumulation of the focus detection pixels in the second partial rectangular region independently of each other, and the first and second partial rectangles The regions are spaced apart from each other and the first The focus detection pixels in the partial rectangular area of one microlens receive the first pair of light beams that have passed through the first pair of areas of the pupil of the optical system and output a pair of image signals. And a photoelectric conversion unit that receives one of the first pair of light beams, a first focus detection pixel, one microlens, and a photoelectric sensor that receives the other of the first pair of light beams. Second focus detection pixels having a conversion unit are alternately arranged, and the focus detection pixels of the second partial rectangular region are second pixels that have passed through a second pair of regions of the pupil of the optical system. A third focus detection pixel including one microlens and a photoelectric conversion unit that receives one of the second pair of light beams so as to receive a pair of light beams and output a pair of image signals; A photoelectric conversion unit that receives one microlens and the other of the second pair of light beams; The fourth focus detection pixels provided are alternately arranged, and the direction of the alternate arrangement of the first and second focus detection pixels of the first partial rectangular region is the first direction of the second partial rectangular region. Unlike the direction of the alternating arrangement of the third and fourth focus detection pixels, the readout of the focus detection pixel output of the first partial rectangular area by the first readout circuit is performed in the alternating arrangement direction. For each of the first and second focus detection pixel columns, scanning is performed in a direction perpendicular to the alternate arrangement direction, and readout of the focus detection pixel output of the second partial rectangular area is performed by the second readout circuit. Is performed by scanning each of the third and fourth focus detection pixel columns arranged in the alternate arrangement direction in a direction perpendicular to the alternate arrangement direction.

  According to the present invention, the output of the focus detection pixel can be set to a level suitable for focus detection regardless of the position in the photographing screen where there is a luminance difference, and focus detection can be reliably performed.

  FIG. 1 shows a configuration of a digital still camera according to an embodiment. A digital still camera 201 according to an embodiment includes an interchangeable lens 202 and a camera body 203 and is coupled by a mount unit 204.

  The interchangeable lens 202 includes a lens 209, a zooming lens 208, a focusing lens 210, an aperture 211, a lens drive control device 206, and the like. The aperture 211 forms an aperture whose aperture diameter at the center of the optical axis is variable in order to adjust the amount of light and the amount of blur. The lens drive control device 206 controls the driving of the focusing lens 210, the drive control for adjusting the aperture diameter of the aperture 211, the state detection of the zooming lens 208, the focusing lens 210 and the aperture 211, and a body drive control device 214 which will be described later. The lens information is transmitted and the camera information is received by communicating with the camera.

  The camera body 203 includes a light splitting prism 220, an image pickup device 212 for image pickup, an image pickup device 218 for focus detection, a body drive control device 214, a liquid crystal display device drive circuit 215, a liquid crystal display device 216, an eyepiece lens 217, and a memory card 219. Etc. The light branching prism 220 splits the light beam coming from the interchangeable lens 202 by a semi-transmissive surface (half mirror) 221.

  The image sensor 212 is disposed on the planned imaging plane of the interchangeable lens 202 on the transmission side of the light branching prism 220 and is used for imaging. On the other hand, the image sensor 218 is disposed on the planned imaging plane of the interchangeable lens 202 on the reflection side of the light branching prism 220 and is used for focus detection. The memory card 219 is an image storage for storing and storing a subject image captured by the imaging image sensor 212.

  The body drive control device 214 includes a microcomputer and peripheral components such as a memory and an A / D converter. The body drive control device 214 controls drive of the image sensors 212 and 218 and communicates with the lens drive control device 206 (receive lens information / camera information ( (Defocus amount) transmission), image processing, focus detection and focus adjustment of the interchangeable lens 202, sequence control of the entire digital still camera, and the like. The body drive control device 214 and the lens drive control device 206 exchange various information (lens information, defocus amount for driving the focusing lens, etc.) via the electrical contact portion 213 provided in the mount portion 204.

  The liquid crystal display element driving circuit 215 drives the liquid crystal display element 216 in accordance with the body drive control device 214 and displays a subject image and information related to photographing on the liquid crystal display element 216. The photographer visually recognizes the subject image and shooting information displayed on the liquid crystal display element 216 via the eyepiece lens 217. That is, the liquid crystal display element driving circuit 215 and the liquid crystal display element 216 function as a liquid crystal viewfinder (electronic viewfinder EVF).

  Imaging pixels 212 are two-dimensionally arranged on the imaging element 212 for imaging, and focus detection pixels are two-dimensionally arranged on the imaging element 218 for focus detection. The subject image that is transmitted through the interchangeable lens 202 and formed on the image sensor 212 is subjected to photoelectric conversion by the image sensor 212 and the output is sent to the body drive controller 214. On the other hand, the subject image formed on the image sensor 218 through the interchangeable lens 202 is photoelectrically converted by the image sensor 218, and the output is sent to the body drive control device 214.

  The body drive control device 214 calculates the defocus amount of the interchangeable lens 202 based on the output of the focus detection pixel, and sends this defocus amount to the lens drive control device 206. In addition, the body drive control device 214 stores the image signal generated based on the output of the imaging pixel in the memory card 219 and sends the image signal to the liquid crystal display element drive circuit 215 for display 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 size of the aperture opening.

  The lens drive control device 206 changes the lens information according to the focusing state, zooming state, aperture setting state, aperture opening F value, and the like. Specifically, the lens drive control device 206 monitors the positions of the lenses 208 and 210 and the diaphragm position of the diaphragm 211, calculates lens information according to the monitor information, or a lookup table prepared in advance. Select the lens information according to the monitor information.

  The lens drive control device 206 calculates a lens drive amount based on the defocus amount received from the body drive control device 214, and brings the focusing lens 210 into focus by a drive source such as a motor (not shown) based on the lens drive amount. And drive. Further, the lens drive control device 206 drives the diaphragm 211 by a drive source such as a motor (not shown) based on the diaphragm control information received from the body drive control apparatus 214.

  FIG. 2 is a front view showing a detailed configuration of the imaging element 212 for imaging, and shows a part of the imaging element 212 in an enlarged manner. The imaging element 212 for imaging is composed of imaging pixels 310. As illustrated in FIG. 4, the imaging pixel 310 includes a microlens 10, a photoelectric conversion unit 11, and a color filter (not illustrated). The color filters include three types of red (R), green (G), and blue (B), and each spectral sensitivity has the characteristics shown in FIG. In the image pickup device 212 for image pickup, image pickup pixels including these color filters are arranged in a Bayer array. The photoelectric conversion unit 11 of the imaging pixel 310 is designed in such a shape that the microlens 10 receives all the light beams that pass through the exit pupil (for example, F1.0) of a bright interchangeable lens.

  FIG. 3 is a front view showing a detailed configuration of the image sensor 218 for focus detection, and shows a part of the image sensor 218 in an enlarged manner. The image sensor 218 includes focus detection pixels 311 for focus detection. As shown in FIG. 5, the focus detection pixel 311 includes a microlens 10 and a pair of photoelectric conversion units 12 and 13. The alignment direction of the pair of photoelectric conversion units 12 and 13 is the horizontal direction, and in such an array of focus detection pixels, image shift detection for focus detection is performed in the horizontal direction. In the array of focus detection pixels 311 shown in FIG. 3, image shift detection is performed in units of rows.

  A color filter is not set in the focus detection pixel 311 in order to increase the amount of light, and its spectral characteristic is a spectral characteristic that combines the spectral sensitivity of a photodiode that performs photoelectric conversion and the spectral characteristic of an infrared cut filter (not shown). 7), that is, spectral characteristics such as those obtained by adding the spectral characteristics of the green pixel, red pixel, and blue pixel shown in FIG. 6, and the light wavelength region of the sensitivity is light having the sensitivity of the green pixel, red pixel, and blue pixel. It covers the wavelength range. The pair of photoelectric conversion units 12 and 13 of the focus detection pixel 311 are designed in such a shape that the microlens 10 receives all the light beams passing through a specific exit pupil (for example, F2.8) of the interchangeable lens.

  FIG. 8 is a cross-sectional view of the imaging pixel 310. In the imaging pixel 310, the microlens 10 is disposed in front of the photoelectric conversion unit 11 for imaging, and the photoelectric conversion unit 11 is projected forward by the microlens 10. The photoelectric conversion unit 11 is formed on the semiconductor circuit substrate 28. A color filter (not shown) is disposed at a position intermediate between the microlens 10 and the photoelectric conversion unit 11.

  FIG. 9 is a cross-sectional view of the focus detection pixel 311. In the focus detection pixel 311, the microlens 10 is disposed in front of the focus detection photoelectric conversion units 12 and 13, and the photoelectric conversion units 12 and 13 are projected forward by the microlens 10. The photoelectric conversion units 12 and 13 are formed on the semiconductor circuit substrate 29.

  The focus detection by the pupil division method using the microlens will be described with reference to FIG. Reference numeral 90 denotes an exit pupil set at a distance d in front of the microlens arranged on the planned imaging plane of the interchangeable lens. The distance d is a distance determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion unit, and is hereinafter referred to as a distance measuring pupil distance. 91 is an optical axis of the interchangeable lens, 50 and 60 are microlenses, (52, 53) (62, 63) are a pair of photoelectric conversion units of focus detection pixels, and 72, 73, 82, 83 are focus detection light beams.

  Reference numeral 92 denotes an area of the photoelectric conversion units 52 and 62 projected by the microlenses 50 and 60, and is hereinafter referred to as a distance measuring pupil. Reference numeral 93 denotes an area of the photoelectric conversion units 53 and 63 projected by the microlenses 50 and 60, and is hereinafter referred to as a distance measuring pupil. In FIG. 10, a focus detection pixel (consisting of a microlens 50 and a pair of photoelectric conversion units 52 and 53) on the optical axis 91 and an adjacent focus detection pixel (a microlens 60 and a pair of photoelectric conversion units 62 and 63). In other focus detection pixels, the pair of photoelectric conversion units receive light beams coming from the pair of distance measurement pupils 92 and 93 to the microlenses, respectively. The arrangement direction of the focus detection pixels is made to coincide with the arrangement direction of the pair of distance measurement pupils.

  The microlenses 50 and 60 are disposed in the vicinity of the planned imaging plane of the optical system, and the shape of the pair of photoelectric conversion units 52 and 53 disposed behind the microlens 50 disposed on the optical axis 91 is micro. The projections are projected onto the exit pupil 90 separated from the lenses 50 and 60 by the distance measurement pupil distance d, and the projection shapes form distance measurement pupils 92 and 93.

  The shape of the pair of photoelectric conversion units 62 and 63 disposed behind the microlens 60 disposed adjacent to the microlens 50 is projected onto the exit pupil 90 separated by the distance measuring pupil distance d, and the projected shape thereof. Forms distance measuring pupils 92 and 93. That is, the positions of the microlens and the photoelectric conversion unit of each pixel so that the projection shapes (ranging pupils 92 and 93) of the photoelectric conversion unit of each focus detection pixel match on the exit pupil 90 at the distance measurement pupil distance d. The relationship has been determined.

  The photoelectric conversion unit 52 passes through the distance measuring pupil 92 and outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 72 directed to the microlens 50. The photoelectric conversion unit 53 passes through the distance measuring pupil 93 and outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 73 directed to the microlens 50.

  The photoelectric conversion unit 62 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 82 passing through the distance measuring pupil 92 and directed to the microlens 60. The photoelectric conversion unit 63 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 83 passing through the distance measuring pupil 93 and directed to the microlens 60.

  A large number of such focus detection pixels are arranged in a straight line, and the output of the pair of photoelectric conversion units of each pixel is grouped into an output group corresponding to the distance measurement pupil 92 and the distance measurement pupil 93, whereby the distance measurement pupil 92 and the measurement pupil 92 are measured. Information on the intensity distribution of a pair of images formed on the focus detection pixel array by the focus detection light fluxes that pass through the distance pupil 93 is obtained. By applying an image shift detection calculation process (correlation calculation process, phase difference detection process), which will be described later, to this information, an image shift amount of a pair of images is detected by a so-called pupil division method.

  Further, by applying a predetermined conversion process to the image shift amount, the deviation of the current imaging plane (imaging plane at the focus detection position corresponding to the position of the microlens array on the planned imaging plane) with respect to the planned imaging plane (Defocus amount) is calculated.

  FIG. 11 is a flowchart illustrating the operation of the digital still camera (imaging device) according to the embodiment. When the power is turned on in step 100, the body drive control device 214 starts operation from step 110. In step 110, the image pickup pixel data is read out from the image pickup device (image pickup sensor) 212 for image pickup and displayed on the electronic viewfinder.

  In step 120, the data of the focus detection pixel is read out from the image sensor (AF sensor) 218 for focus detection. This data is a pair of image data corresponding to a pair of images. In the following step 130, an image shift detection calculation process (correlation calculation process) described later is performed based on the pair of image data, and the image shift amount is calculated and converted into a defocus amount. The defocus amount is calculated in a plurality of areas in the screen as will be described later, and the final defocus amount is determined based on the calculated plurality of defocus amounts. For example, there is a method in which an average of a plurality of defocus amounts is used as a final defocus amount, or a defocus amount indicating the closest distance among the plurality of defocus amounts is used as a final defocus amount.

  In step 140, it is determined whether or not the focus is close, that is, whether or not the calculated absolute value of the final defocus amount is within a predetermined value. If it is determined that the subject is not in focus, the process proceeds to step 150, where the defocus amount is transmitted to the lens drive control device 206, the focusing lens 210 of the interchangeable lens 202 is driven to the in-focus position, and the process returns to step 110 and described above. Repeat the process.

  Even when focus detection is impossible, the process branches to step 150, a scan drive command is transmitted to the lens drive control device 206, the focusing lens 210 of the interchangeable lens 202 is scan-driven between infinite and close, and the process returns to step 110. The above operation is repeated.

  On the other hand, if it is determined that it is close to the in-focus state, the process proceeds to step 160, where it is determined whether or not a shutter release has been performed by operating a release means (not shown), and if it is determined that the shutter release has not been performed, the process proceeds to step 110. It returns and repeats the process mentioned above.

  If it is determined that the shutter release has been performed, the process proceeds to step 170, where an aperture adjustment command is transmitted to the lens drive control unit 206, and the aperture value of the interchangeable lens 202 is controlled as an F value (F value set by the photographer or automatically). To. When the aperture control is completed, the image pickup device 212 for image pickup performs an image pickup operation, and image data is read from the image pickup pixels of the image pickup device 212. In step 180, the image pickup pixel data is stored in the memory card 219 as image data, and the process returns to step 110 to repeat the above-described processing.

  Next, details of the image shift detection calculation process (correlation calculation process) in step 130 of FIG. 11 will be described. The pair of images detected by the focus detection pixels has a possibility that the distance measurement pupil is displaced by the aperture of the lens and the balance of the light quantity is lost. Perform the operation.

For the pair of data strings (A11 to A1M, A21 to A2M, where M is the number of data) read from the focus detection pixel string, a correlation calculation formula is calculated by the following formula to calculate the correlation amount C (k).
C (k) = Σ | A1n · A2n + 1 + k−A2n + k · A1n + 1 | (1)
In equation (1), the Σ operation is accumulated for n, and the range that n takes is limited to the range in which the data of A1n, A1n + 1, A2n + k, and A2n + 1 + k exist according to the image shift amount k. Is done. Further, 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. 12A, the calculation result of the expression (1) shows that the correlation amount C (k) is minimal in the shift amount having high correlation between the pair of data (k = kj = 2 in FIG. 12A). (The smaller the value, the higher the degree of correlation). The shift amount x that gives the minimum value C (x) with respect to the continuous correlation amount is obtained using the three-point interpolation method according to the equations (2) to (5).
x = kj + D / SLOP (2),
C (x) = C (kj) − | D | (3),
D = {C (kj-1) -C (kj + 1)} / 2 (4),
SLOP = MAX {C (kj + 1) -C (kj), C (kj-1) -C (kj)} (5)

  Whether or not the shift amount x calculated by the equation (1) is reliable is determined as follows. As shown in FIG. 12B, when the correlation degree between the pair of data is low, the value of the interpolated correlation minimum value C (x) becomes large. Therefore, when C (x) is equal to or greater than a predetermined threshold value, it is determined that the calculated shift amount has low reliability, and the calculated shift amount x is canceled. Alternatively, in order to normalize C (x) with the contrast of data, when the value obtained by dividing C (x) by SLOP that is proportional to the contrast is equal to or greater than a predetermined value, the reliability of the calculated shift amount Is determined to be low, and the calculated shift amount x is canceled. Alternatively, when SLOP that is a value proportional to the contrast is equal to or less 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 x is canceled.

  As shown in FIG. 12C, when the correlation between the pair of data is low and there is no drop in the correlation amount C (k) between the shift ranges knin to kmax, the minimum value C (x) is obtained. In such a case, it is determined that the focus cannot be detected.

  The correlation calculation formula is not limited to the above formula (1), and any correlation calculation formula that can maintain the image shift detection accuracy with respect to the light quantity balance may be used.

If it is determined that the calculated shift amount x is reliable, it is converted into the image shift amount shft by the following equation.
shft = PY · x (6)
In the equation (6), PY is a detection pitch (a pitch of focus detection pixels). The image shift amount calculated by the equation (6) is multiplied by a predetermined conversion coefficient k to be converted into a defocus amount def.
def = k · shft (7)

  FIG. 13 shows a detailed configuration of the image sensor 218 for focus detection. On the semiconductor substrate surface 230 of the image sensor 218 for focus detection, focus detection pixels 311 are two-dimensionally arranged without a gap as shown in FIG. The semiconductor substrate surface 230 corresponding to the imaging screen is divided into four partial regions 311, 321, 331, and 341 by horizontal and vertical lines passing through the center of the surface. The first scanning circuits 312, 322, 332, and 342 and the second scanning circuits 313, 323, 333, and 343 are provided independently for each region.

  The signals of the focus detection pixels belonging to the partial region 311 are scanned by the first scanning circuit 312 in the direction of the arrow 314 one line at a time in the vertical direction, and the signal for one scanned line is scanned by the second scanning circuit 313 as indicated by the arrow 315. One pixel is output in the direction. Further, the signals of the focus detection pixels belonging to the partial area 321 are scanned by the first scanning circuit 322 in the direction of the arrow 324 one line at a time in the vertical direction, and the signal for one scanned line is scanned by the second scanning circuit 323. One pixel is output in the direction of 325.

  The signals of the focus detection pixels belonging to the partial region 331 are scanned by the first scanning circuit 332 in the direction of the arrow 334 one line at a time in the vertical direction, and the signal for one scanned line is scanned by the second scanning circuit 333 as indicated by the arrow 335. One pixel is output in the direction. Further, the signals of the focus detection pixels belonging to the partial region 341 are scanned by the first scanning circuit 342 in the direction of the arrow 344 one line at a time in the vertical direction, and the signal for one scanned line is scanned by the second scanning circuit 343. One pixel is output in the direction of 345.

  The scanning circuit is independent for each region, and by changing the operation (scanning time) of the scanning circuit, the charge accumulation time of the focus detection pixel can be controlled independently for each region to which the focus detection pixel belongs.

  FIG. 14 is a conceptual diagram showing a circuit configuration of an image sensor 218 for focus detection. Here, an example in which the configuration of one region of the imaging element 218 for focus detection shown in FIG. 13 is configured by a CMOS circuit is shown, and a layout of 4 photoelectric conversion units × 4 photoelectric conversion units is shown for easy understanding. .

  The signal holding unit 502 is a buffer that temporarily holds an output signal from the photoelectric conversion unit 503 of the focus detection pixels for one row, and is a control in which the first scanning circuit 504 emits an image signal output to the output line 501. Latch based on the signal ΦH. The charge accumulation operation of the photoelectric conversion unit 503 is independently controlled for each row by a control signal (ΦR1 to ΦR4) generated by the first scanning circuit 504. Therefore, simultaneity between the photoelectric conversion units belonging to the same row is ensured.

  The signal output of the photoelectric conversion unit 503 of the focus detection pixel is independently controlled for each row by a control signal (ΦS1 to ΦS4) generated by the first scanning circuit 504. The signal of the photoelectric conversion unit 503 selected by the control signal is output to the output line 501. The image signals held in the signal holding unit 502 are sequentially transferred to the output circuit 506 by the control signals (ΦV1 to ΦV4) generated by the second scanning circuit 505, amplified by the amplification degree set by the output circuit 506, and externally transmitted. Is output.

  FIG. 15 is a detailed circuit diagram of the photoelectric conversion unit 503 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 section 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 ΦR4), the charges accumulated in the FD and PD are cleared and reset. (Charge accumulation start).

  The output of AMP is connected to the 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 (ΦS1 to ΦS4), the output of AMP is output to the output line 501. The

  FIG. 16 is a timing chart showing the operation of the focus detection image sensor shown in FIG. The charge accumulation time control, charge accumulation timing control, and signal readout control of the focus detection image sensor 218 are performed by a rolling shutter method in the same manner as the control of the so-called CMOS image sensor. The photoelectric conversion unit 503 of the focus detection pixel in the first row is selected by the control signal ΦS1 generated by the first scanning circuit 504, and the image signal of the photoelectric conversion unit 503 of the selected focus detection pixel is output to the output line 501.

  The image signal of the first row output to the output line 501 by the control signal ΦH issued in synchronization with the control signal ΦS1 is temporarily held in the signal holding unit 502. The image signal of the photoelectric conversion unit 503 of the focus detection pixel in the first row held in the signal holding unit 502 is transferred to the output circuit 506 in accordance with the control signals ΦV1 to ΦV4 sequentially issued from the second scanning circuit 505, and output circuit The signal is output to the outside after being amplified with the amplification degree set in 506.

  When the transfer of the image signals of the imaging pixels in the first row to the signal holding unit 502 is completed, the photoelectric conversion unit 503 of the focus detection pixel in the first row is reset by the control signal ΦR1 issued from the first scanning circuit 504. The next charge accumulation of the photoelectric conversion unit 503 of the focus detection pixel in the first row is started. When the output from the image signal output circuit of the photoelectric conversion unit 503 of the focus detection pixel in the first row is finished, the photoelectric conversion unit 503 of the focus detection pixel in the second row outputs the control signal ΦS2 generated by the first scanning circuit 504. The image signal of the photoelectric conversion unit 503 of the selected focus detection pixel is output to the output line 501.

  Thereafter, similarly, the image signal of the photoelectric conversion unit 503 of the focus detection pixel in the second row is held, the photoelectric conversion unit 503 of the focus detection pixel is reset, and the image signal is output. Subsequently, the image signal of the photoelectric conversion unit 503 of the focus detection pixel in the third row is held, the photoelectric conversion unit 503 of the focus detection pixel is reset, and the image signal of the photoelectric conversion unit 503 of the focus detection pixel is output. Subsequently, the image signal of the photoelectric conversion unit 503 of the focus detection pixel in the fourth row is held, the photoelectric conversion unit 503 of the focus detection pixel is reset, and the image signal of the photoelectric conversion unit 503 of the focus detection pixel is output.

  Subsequently, returning to the first line again, the above operation is repeated. The period Ts from the charge holding timing of the image signal of the photoelectric conversion unit 503 of the focus detection pixel to the charge holding timing of the image signal of the next photoelectric conversion unit, and the charge accumulation time Tin (exposure time: pixel reset of the photoelectric conversion unit) The time from the timing to the holding timing of the image signal is controlled according to the brightness of each region so that the level of the image signal becomes a level suitable for the focus detection calculation.

  The brightness (luminance) of each region can be detected by a divided photometric sensor (not shown in FIG. 1). The charge accumulation time may be feedback controlled based on the average value of the image signals in each region. The charge accumulation time Tin can be changed by changing the ON period Tn of the control signal ΦRn. The charge accumulation period Ts can be changed by changing the rising timing interval Tx of the control signal ΦSn.

  As described above, the focus detection pixels arranged two-dimensionally are divided into a plurality of regions, and the charge accumulation operation is controlled by providing independent control circuits in each region. In addition, it is possible to perform the charge accumulation operation in each region at the same time, prevent a decrease in the response of the focus detection operation, and make it possible to set the output level of the focus detection pixel in each region to a level suitable for focus detection, A defocus amount can be reliably detected in each region.

  Note that the charge accumulation operation can be controlled with a plurality of regions as a single region by uniformly and simultaneously controlling control circuits provided independently for the plurality of regions. In this way, focus detection can be performed at a portion including the boundaries of a plurality of regions.

<< Other Embodiments of the Invention >>
FIG. 17 is a front view showing a detailed configuration of a modified example of the focus detection image sensor. In the focus detection image sensor 218 illustrated in FIG. 3, the focus detection pixel 311 includes a pair of photoelectric conversion units in one pixel. However, the focus detection image sensor 218 </ b> A of the modification illustrated in FIG. The focus detection pixels 313 and 314 include one photoelectric conversion unit in one pixel. In this modification, the focus detection pixel 313 and the focus detection pixel 314 are paired, and correspond to the focus detection pixel 311 of the focus detection image sensor 218 shown in FIG.

  FIG. 18A shows the configuration of the focus detection pixel 313. The focus detection pixel 313 includes the microlens 10 and the photoelectric conversion unit 16. FIG. 18B shows the configuration of the focus detection pixel 314. The focus detection pixel 314 includes the microlens 10 and the photoelectric conversion unit 17. The photoelectric conversion units 16 and 17 are projected onto the exit pupil of the interchangeable lens 202 by the microlens 10 to form distance measuring pupils 92 and 93 shown in FIG. Therefore, an output of a pair of images used for focus detection can be obtained by the arrangement of the focus detection pixels 313 and 314. By providing one photoelectric conversion unit in the focus detection pixel, it is possible to avoid a complicated reading circuit configuration of the image sensor 218A.

  FIG. 19 is a diagram illustrating a modification of the pixel array of the focus detection image sensor. In the configuration of the focus detection imaging element 218 shown in FIG. 13, focus detection is provided with a pair of photoelectric conversion units arranged in the horizontal direction in the four partial regions 311, 321, 331, and 341 of the semiconductor substrate surface corresponding to the screen. Although the example in which the pixels 311 are arranged in a two-dimensional manner is shown, the pixel arrangement of the focus detection imaging element 218B shown in FIG. 19 includes a pair of photoelectric conversion units arranged in two horizontal regions 321 and 341. The focus detection pixels 311 are arranged in a two-dimensional form, and the focus detection pixels 315 (focus detection pixels 311) having a pair of photoelectric conversion units arranged in the vertical direction in the two partial regions 311 and 331 as shown in FIG. In a two-dimensional array.

  FIG. 21 is a configuration diagram of the focus detection imaging device 218B having the pixel array of FIG. 19. The first scanning circuits 312, 322, 332, 342 and the fourth scanning regions 311, 321, 331, 341 and Two scanning circuits 313, 323, 333, and 343 are provided independently, but the arrangement of the first scanning circuits 312 and 332 and the second scanning circuits 313 and 333 is reversed as compared with the image sensor 218 shown in FIG. 13. Yes.

  The signals of the focus detection pixels belonging to the partial region 311 are scanned in the direction of the arrow 316 (horizontal direction) one row at a time in the vertical direction by the first scanning circuit 312, and the scanned signal for one row is the second scanning circuit 313. As a result, one pixel is output in the direction of arrow 317 (vertical direction). Further, the signals of the focus detection pixels belonging to the partial area 321 are scanned in the direction of the arrow 324 (vertical direction) one row at a time in the vertical direction by the first scanning circuit 322, and the signal for one row scanned is the second scan. The circuit 323 outputs one pixel at a time in the direction of the arrow 325 (horizontal direction).

  The signals of the focus detection pixels belonging to the partial region 331 are scanned by the first scanning circuit 332 in the direction of the arrow 336 (horizontal direction) one row at a time in the vertical direction, and the scanned signal for one row is the second scanning circuit 333. Thus, one pixel is output in the direction of arrow 337 (vertical direction). Further, the signals of the focus detection pixels belonging to the partial area 341 are scanned in the direction of the arrow 344 (vertical direction) one line at a time in the vertical direction by the first scanning circuit 342, and the signal for one line scanned is the second scan. The circuit 343 outputs one pixel at a time in the direction of the arrow 345 (horizontal direction).

  The scanning circuit is independent for each region, and by changing the operation (scanning time) of the scanning circuit, the charge accumulation time of the focus detection pixel can be controlled independently for each region to which the focus detection pixel belongs.

  With the configuration as described above, after performing the charge accumulation operation independently for each of the plurality of regions in the screen, it is possible to detect the image shift in two directions, the horizontal direction and the vertical direction, and image in only one direction. Compared to the case where the shift cannot be detected, the focus detection capability for various subjects is improved.

  FIG. 22 is a diagram illustrating another modification of the pixel array of the focus detection image sensor. In the pixel array of the focus detection imaging device 218B shown in FIG. 19, the semiconductor substrate surface corresponding to the imaging screen is divided into four partial areas 311, 321, 331, and 341, and the image shift detection direction is horizontal in each area. The example in which the focus detection pixels in the direction and the focus detection pixels in the image shift detection direction are arranged in the vertical direction is shown. However, in the image sensor 218C shown in FIG. 22, a plurality of rectangles separated from each other on the semiconductor substrate surface corresponding to the image pickup screen. Block areas 401 to 409 are formed, and a reduced focus detection pixel array in which the number of focus detection pixel arrays capable of focus detection in two directions shown in FIG. 19 is reduced is arranged in each rectangular block area.

  That is, each rectangular block area is divided into four partial rectangular areas, and image shift detection can be performed in different directions in each partial rectangular area. In the rectangular block areas 403, 405, 407, and 409 located in the diagonal direction of the imaging screen, the reduced version is such that one side of the rectangular block area is parallel to the radiation direction from the center of the screen toward the center of the rectangular block area. The focus detection pixel array is rotated.

  FIG. 23 is a configuration diagram of the focus detection imaging device 218C having the pixel array shown in FIG. 22, and the same circuit configurations 411 to 419 as those in FIG. 21 are arranged in the rectangular block regions 401 to 409, respectively. The charge accumulation operation is performed independently between the rectangular block regions, and the charge accumulation operation is also performed independently in the four partial rectangular regions in one rectangular block region. By separating the rectangular block areas, a circuit configuration for controlling the rectangular block areas can be arranged around the rectangular block areas.

  With the configuration as described above, it is possible to perform image misalignment detection in two directions in each rectangular block area after performing charge accumulation operation independently for each of the partial rectangular areas of the plurality of rectangular block areas in the screen. The focus detection ability for various subjects is improved.

  In addition, the reduced focus detection pixel array can be rotated and arranged in any direction in the rectangular block area, reducing the influence of vignetting of the focus detection light beam due to the aperture of the optical system according to the position of the rectangular block area on the screen. In addition to being able to adjust the rotation direction to the direction of the image, it is possible to detect image shift in an oblique direction in addition to the horizontal direction and the vertical direction in one screen.

  FIG. 24 is a diagram showing a modification of the circuit configuration of the focus detection image sensor. In the configuration of the focus detection imaging element 218C shown in FIG. 23, the reduced-size circuit configuration shown in FIG. 21 is arranged in a plurality of rectangular block regions spaced from each other on the semiconductor substrate surface corresponding to the imaging screen, and each rectangular block is arranged. The area is divided into four partial rectangular areas and image shift detection is performed in two directions. However, in the focus detection image sensor 218D shown in FIG. 24, two straight lines orthogonal to the area corresponding to each rectangular block area. The focus detection pixel arrangement units 421 to 429 arranged above are arranged, and the charge accumulation operation of the focus detection pixels arranged on each straight line is independently controlled.

  In the focus detection pixel array units 423, 425, 427, and 429 arranged in the diagonal direction of the imaging screen, the unit is rotated so that one focus detection pixel array extends along the radiation direction from the screen center toward the unit center. Arranged.

  FIG. 25 is a diagram showing a detailed configuration of the focus detection pixel array unit. The focus detection pixels 313 and 314 shown in FIG. 18 are arrayed on a straight line 320, and the focus is configured by rotating the focus detection pixels 313 and 314 by 90 degrees. The detection pixels 316 and 317 are arranged on a straight line 321 orthogonal to the straight line 320. The pixel interval between the focus detection pixels 313 and 314 and the pixel interval between the focus detection pixels 316 and 317 are √2 times the pixel size, and the focus detection pixel 313 (314) and the focus detection pixel at the intersection of the pixel array. The pixel interval with 316 (317) is equal to the pixel size. By setting the pixel interval in this way, it is possible to cross the pixel arrangement with the minimum pixel interval.

  A scanning circuit 353 is disposed below the array on the right side of the pixel intersection position among the array of focus detection pixels 313 and 314. The scanning circuit 353 controls the charge accumulation for the array, and the pixel signal is output in the direction of the arrow 356. In addition, the scanning circuit 363 is disposed above the array on the left side of the pixel crossing position in the array including the focus detection pixels 313 and 314. The scanning circuit 363 controls the charge accumulation for the array, and the pixel signal is output in the direction of the arrow 366.

  A scanning circuit 373 is arranged on the right side of the array including the focus detection pixels 316 and 317 above the pixel crossing position. The scanning circuit 373 controls the charge accumulation for the array, and the pixel signal is output in the direction of the arrow 376. In addition, the scanning circuit 383 is arranged on the left side of the array formed of the focus detection pixels 316 and 317 below the pixel crossing position. The scanning circuit 383 controls the charge accumulation for the array, and the pixel signal is output in the direction of the arrow 386.

  The scanning circuit 353 and the scanning circuit 363 are synchronized so as to perform charge accumulation operation and signal readout at the same timing, and the scanning circuit 373 and the scanning circuit 383 are synchronized so as to perform charge accumulation operation and signal readout at the same timing. Yes.

  As described above, the focus detection pixel array units arranged in a cross shape are compared with the rectangular two-dimensional focus detection pixel array unit shown in FIG. 23 in a two-direction region sandwiching the same point (pixel crossing position). Image shift detection is possible, and the identity of the subject when performing focus detection in two directions is improved.

  Further, by providing a scanning circuit for each focus detection pixel array at a point-symmetrical position with respect to the four focus detection pixel arrays with the pixel crossing position as a boundary, the focal point closest to the pixel crossing position is provided. Circuit wiring of the signal readout portion of the scanning circuit of the detection pixel is facilitated.

  Further, since the focus detection pixels 313 and 314 and the focus detection pixels 316 and 317 are arranged so that the position of the photoelectric conversion unit of the focus detection pixel closest to the pixel intersection position is farther than the pixel intersection position, the pixel intersection position The circuit wiring of the signal readout part of the scanning circuit of the focus detection pixel closest to is facilitated.

  Furthermore, since the number of focus detection pixels can be reduced as compared with the two-dimensional focus detection pixel array unit shown in FIG. 23, high-speed signal readout is possible and the focus detection calculation time is shortened. The response of the focus detection operation is improved.

  FIG. 26 is a diagram illustrating a configuration of a modified example of the imaging apparatus. In the imaging apparatus shown in FIG. 1, the example in which the focus detection imaging element 218 is arranged on the planned imaging surface of the interchangeable lens 202 on the reflection side of the light splitting prism 220 is shown, but in the imaging apparatus 201A shown in FIG. A field lens 601 is provided on the exit surface on the reflection side of the light splitting prism 220, and further includes a stop mask 602 having a stop aperture 603 in the reflected light path and a re-imaging lens 604, and a planned image plane (primary image plane). ) Is re-imaged on an image sensor 218 for focus detection arranged on the re-imaging plane (secondary image plane) of the re-imaging lens 604. Other configurations are the same as those of the imaging apparatus 201 shown in FIG.

  FIG. 27 is a perspective view of a re-imaging optical system that includes a field lens 601, a mask 602, a re-imaging lens 604, and an image sensor 218 for focus detection. The aperture 603 is a circular aperture with the optical axis 91 as the center. The aperture 603 is projected by the field lens 601 in the direction of the exit pupil of the interchangeable lens. The re-imaging lens 604 reduces the primary image to form a secondary image. Any of the image sensors described above can be applied as the image sensor 218. The photoelectric conversion unit of the focus detection pixel of the image sensor 218 is projected onto the exit pupil position of the diaphragm mask 602 (the position of the virtual image of the diaphragm mask 602 formed by the re-imaging lens 604) by the microlens.

  With the above configuration, the pair of light beams passing through the interchangeable lens is limited by the aperture opening and the aperture mask opening 603 of the interchangeable lens, and then received by the pair of photoelectric conversion units of the focus detection pixel.

  According to such a configuration, the size of the image sensor can be reduced compared to the case where the image sensor 218 is arranged on the primary image plane, and this is advantageous in terms of cost and the image sensor on the primary image plane. The adverse effect (ghost, stray light) on the imaging device 212 for imaging due to surface reflection of the imaging device 218 when the 218 is disposed can be removed.

  When the image sensor 218 is disposed on the primary image plane, the peripheral portion of the distance measuring pupil is blurred due to the diffraction of the micro lens of the focus detection pixel, and a pair of focus detection light beams are generated by the exit pupil of the interchangeable lens. The vignetting is easy, and the position of the exit pupil differs depending on the type of the interchangeable lens, so the vignetting of the pair of focus detection light beams becomes nonuniform in the periphery of the screen, which deteriorates the accuracy of image shift detection. Yes.

  On the other hand, when the re-imaging optical system is adopted, the pair of focus detection light beams received by the focus detection pixels are vignetted by the exit pupil of the stop mask 602 whose position is fixed. If the F value of the projected aperture when projected onto the interchangeable lens side by the field lens 601 is made larger than the F value of the exit pupil of the interchangeable lens, the vignetting of a pair of focus detection light beams around the screen Therefore, it is possible to prevent the deterioration of the accuracy of image shift detection.

  FIG. 28 is a diagram illustrating the configuration of another modification of the imaging apparatus. In the image pickup apparatus shown in FIG. 1, the image pickup image sensor 212 is disposed on the planned imaging plane of the interchangeable lens 202 on the transmission side of the light branch prism 220, and the focus detection image sensor 218 is disposed on the reflection side of the light branch prism 220. In the imaging apparatus 201B shown in FIG. 28, the optical branching prism 220 is eliminated, and the focus detection pixels for focus detection are imaged of a part of the imaging element 212. 2 shows a configuration of an imaging apparatus that is replaced with pixels. Other configurations are the same as those of the imaging apparatus 201 shown in FIG.

  FIG. 29 is a diagram illustrating a focus detection position on the screen. When the focus detection pixel array embedded in the imaging element 212A for imaging performs focus detection, an area for sampling an image on the screen (focus detection area, focus detection position). ). Focus detection areas 101 to 104 are arranged at four locations in the center of each area in an area divided into four by a horizontal line and a vertical line passing through the center of the screen on the screen 100. Focus detection pixels are linearly arranged in the longitudinal direction of the focus detection area indicated by a rectangle.

  FIG. 30 is a front view showing a detailed configuration of an image sensor 212A according to a modified example, and shows an enlarged view of the vicinity of one focus detection area on the image sensor 212A. The image pickup element 212A includes the image pickup pixel 310 and the focus detection pixel 311 shown in FIGS. The focus detection pixels 311 are arranged linearly and continuously in rows where B and G of the imaging pixels 311 are to be arranged. The circuit configuration of the image sensor 212A is the same as that shown in FIG. 19 in the four partial regions of the semiconductor substrate surface corresponding to the four regions on the screen of FIG. The charge storage operation and image signal readout can be performed independently of each other.

  FIG. 31 is a flowchart showing the operation of the digital still camera (imaging device) 201B of the modification shown in FIG. When the power is turned on at step 200, the body drive control device 214 starts the processing after step 210. In step 210, an image pickup operation is performed on the four partial regions in synchronism with the charge storage time and the charge storage timing, and the data of the image pickup pixels are read out and displayed on the electronic viewfinder.

  In step 220, an image pickup operation is performed on the four partial areas independently of the charge accumulation time and the charge accumulation timing so that the signal level of the focus detection pixel becomes a level suitable for focus detection in each partial area. A pair of image data corresponding to the pair of images is read out from the focus detection pixel array corresponding to the focus detection area. In the subsequent step 230, based on the read pair of image data, image shift amounts are calculated for the four focus detection areas and converted into defocus amounts. Further, a final defocus amount is calculated based on the obtained four defocus amounts.

  In step 240, it is determined whether or not the focus is close to focus, that is, whether or not the absolute value of the final defocus amount is within a predetermined value. If it is determined that the lens is not in focus, the process proceeds to step 250, the defocus amount is transmitted to the lens drive control device 206, the focusing lens 210 of the interchangeable lens 202 is driven to the focus position, and the process returns to step 210 and described above. repeat.

  Even when focus detection is impossible, the process branches to step 250, a scan drive command is transmitted to the lens drive control unit 206, and the focusing lens 210 of the interchangeable lens 202 is scanned from infinity to the nearest position, and the process returns to step 210. The above processing is repeated.

  On the other hand, if it is determined that it is close to the in-focus state, the process proceeds to step 260, where it is determined whether or not a shutter release has been performed by operating an unillustrated release means. If it is determined that the shutter release has not been performed, the process returns to step 210. The above processing is repeated.

  If it is determined that the shutter release has been made, the process proceeds to step 270, where an aperture adjustment command is transmitted to the lens drive control device 206, and the aperture value of the interchangeable lens 202 is controlled as an F value (F value set by the photographer or automatically). To. When the aperture control is completed, the image capturing operation is performed on the four partial regions in synchronization with the charge accumulation time and the charge accumulation timing, and the image data is read from the imaging pixels and all the focus detection pixels of the imaging element 212A.

  In step 280, pixel interpolation of pixel data at each pixel position in the focus detection pixel row is performed based on data of imaging pixels around the focus detection pixel. In the subsequent step 290, image data composed of the imaged pixel data and the interpolated data is stored in the memory card 219, and the process returns to step 210 to repeat the above-described processing.

  According to the above configuration, it is possible to reliably detect the focus in the four focus detection areas on the screen without depending on the luminance difference, and it is necessary to provide the image pickup device for image pickup and the image pickup device for focus detection independently. Therefore, it is advantageous in terms of cost and space, and it is possible to eliminate a focus detection error due to a relative arrangement error between the image sensors.

  FIG. 32 is a front view showing a detailed configuration of an image sensor 212B according to another modification. In the image sensor 212A shown in FIG. 30, an example in which the array of focus detection pixels 311 including a pair of photoelectric conversion units is arranged in a horizontal direction in a part of a two-dimensional array of image pickup pixels is shown in FIG. As shown in the figure, an array of focus detection pixels 315 obtained by rotating the focus detection pixels 311 by 90 degrees may be arranged vertically in a part of a two-dimensional array of imaging pixels. Further, if a part of the four regions has a configuration as shown in FIG. 30 and a part of the configuration as shown in FIG. 32, image shift detection can be performed in two directions on one screen.

  FIG. 33 is a front view showing a detailed configuration of an imaging element 212C according to another modification. In the imaging device 212A shown in FIG. 30, an example in which the array of focus detection pixels 311 including a pair of photoelectric conversion units is arranged in a horizontal direction in a part of a two-dimensional array of imaging pixels is shown. As shown, focus detection pixels 313 and 314 shown in FIG. 18 may be arranged in the horizontal direction instead of the focus detection pixels 311.

  In the circuit configuration of the image sensor shown in FIGS. 13 and 21, signal lines (φSn, φRn, output line 501 shown in FIG. 14) for controlling the charge accumulation operation of the four rectangular regions are provided in the four rectangular regions. Since wiring can be performed without protruding into other regions, it is advantageous in semiconductor manufacturing and crosstalk between wirings can be prevented. As shown in FIG. 14, since the signal lines are wired in a grid pattern in two orthogonal directions, four rectangular areas of a rectangular screen have two orthogonal sides as part of the two sides of the screen. It is common.

  When the focus detection pixels 313 and 314 shown in FIG. 18 are adopted as the focus detection pixels, the space for one photoelectric conversion unit is vacant compared to the focus detection pixel 311 as shown in FIG. It is also possible to wire a signal line for controlling the charge storage time using the vacant space. In such a case, the number, shape, and arrangement of the divided areas are not limited. For example, in the circuit configuration shown in FIG. 13, the semiconductor substrate surface 230 corresponding to the imaging screen is divided into four partial regions 311, 321, 331, and 341 by horizontal and vertical lines passing through the center of the surface. It becomes possible to set the fifth partial area whose side is in contact with the partial areas 311, 321, 331, 341.

  In the case of the circuit configuration as shown in FIGS. 23 and 24, an empty space is formed on the semiconductor substrate, and therefore a circuit for processing a signal output from the focus detection pixel can be arranged in this portion. For example, an AD conversion circuit for converting an analog signal output from each focus detection block into digital data for each focus detection block, or for storing digital data converted by the AD conversion circuit It is possible to arrange a memory circuit or an arithmetic circuit that performs a correlation operation as shown in equation (1) using a signal of a focus detection pixel converted into digital data.

  In the imaging apparatus 201 shown in FIG. 1, a light beam is divided into two, image data is acquired with an imaging device for one light beam, and focus detection is performed with an image sensor for focus detection for the other light beam. However, when the quality of the image data is not questioned, the focus detection pixel output of the image sensor for focus detection can be directly used as the image data. For example, monochrome image data can be obtained by adding the outputs of a pair of photoelectric conversion units. In such a case, in FIG. 1, the image pickup apparatus does not need the light branching unit, and the focus detection image pickup element 218 may be disposed at the position of the image pickup image pickup element 212.

  2, 30, 32, and 33, the imaging pixel includes an example in which the imaging pixel includes a Bayer color filter, but the configuration and arrangement of the color filter are not limited to this, An arrangement of complementary color filters (green: G, yellow: Ye, magenta: Mg, cyan: Cy) may be employed.

  In the image sensor shown in FIGS. 5 and 18, an example in which the focus detection pixel is not provided with a color filter is shown. However, one of the color filters of the same color as the image pickup pixel (for example, a green filter) is provided. Even in this case, the present invention can be applied.

  5 and 18, the shape of the photoelectric conversion unit of the focus detection pixel is shown as a circle or a semicircle, but the shape of the photoelectric conversion unit is not limited to this, and may be another shape. For example, the shape of the photoelectric conversion unit of the focus detection pixel may be an ellipse, a rectangle, or a polygon.

  2, 3 and 30, the imaging pixels and focus detection pixels are arranged in a dense square lattice arrangement, but may be arranged in a dense hexagonal lattice arrangement.

  In the above description, the configuration of the image sensor has been described as a CMOS image sensor, but it can also be configured as a CCD image sensor. For example, when the CMOS circuit configuration shown in FIG. 14 is changed to a CCD circuit configuration, a vertical transfer CCD is arranged instead of the output line 501 for the photoelectric conversion units arranged in the vertical direction using the configuration of the interline CCD. A horizontal transfer CCD may be arranged instead of the second scanning circuit, and a drive clock line for each transfer CCD and a control line for controlling charge transfer from each photoelectric conversion unit to the vertical transfer CCD may be wired.

  In the case of a CMOS image sensor, the charge accumulation timing is controlled by a rolling shutter. Therefore, even in the same region, there is a deviation in the charge accumulation timing depending on the pixel position. Since the pixels are controlled uniformly, it is possible to align the charge accumulation timing within the same region.

  As described above, the present invention can be applied to both a CCD image sensor and a CMOS image sensor.

  The imaging device is not limited to a digital still camera or a film still camera including an interchangeable lens and a camera body, and can be applied to a lens-integrated digital still camera, a film still camera, and a video camera. Alternatively, the present invention can be applied to a small camera module built in a mobile phone, a surveillance camera, a robot vision recognition device, and the like. The present invention can also be applied to focus detection devices other than cameras, distance measuring devices, and stereo distance measuring devices.

The figure which shows the structure of the digital still camera of one embodiment Front view showing a detailed configuration of an image sensor for imaging Front view showing a detailed configuration of an image sensor for focus detection The figure which shows the structure of an imaging pixel The figure which shows the structure of a focus detection pixel Diagram showing spectral characteristics of green, red, and blue pixels for imaging Diagram showing spectral characteristics of focus detection pixels Sectional view showing structure of imaging pixel Sectional view showing structure of focus detection pixel Diagram for explaining focus detection by pupil division method using microlenses The flowchart which shows operation | movement of the digital still camera (imaging device) of one embodiment The figure for demonstrating the determination method of the reliability of a focus detection result Front view showing a detailed configuration of an image sensor for focus detection Conceptual diagram showing the circuit configuration of an image sensor for focus detection Detailed circuit diagram of the photoelectric conversion unit shown in FIG. FIG. 14 is a timing chart showing the operation of the focus detection image sensor shown in FIG. Front view showing a detailed configuration of a modified example of the image sensor for focus detection Front view showing configuration of focus detection pixel The figure which shows the modification of the pixel arrangement | sequence of the image sensor for focus detection The figure which shows the modification of the pixel arrangement | sequence of the image sensor for focus detection FIG. 19 is a configuration diagram of a focus detection imaging device having the pixel array shown in FIG. The figure which shows the other modification of the pixel arrangement | sequence of the image sensor for focus detection FIG. 22 is a configuration diagram of a focus detection imaging device having the pixel array shown in FIG. The figure which shows the modification of the circuit structure of the image sensor for focus detection The figure which shows the detailed structure of a focus detection pixel arrangement unit. The figure which shows the structure of the modification of an imaging device Perspective view of re-imaging optical system for focus detection The figure which shows the structure of the other modification of an imaging device The figure which shows the focus detection position on the screen Front view showing a detailed configuration of an image sensor of a modification 28 is a flowchart showing the operation of the digital still camera (imaging device) of the modification shown in FIG. Front view showing a detailed configuration of an image sensor of another modification Front view showing a detailed configuration of an image sensor of another modification

Explanation of symbols

201, 201A, 201B; imaging device, 202; interchangeable lens, 214; body drive control device, 218, 218A, 218B, 218C, 218D; focus detection image sensor, 212, 212A, 212B, 212C; 311; focus detection pixel, 502; signal holding unit, 503; photoelectric conversion unit, 504; first scanning circuit, 505; second scanning circuit, 506; output circuit

Claims (5)

A rectangular area on a single semiconductor substrate is divided into at least first and second partial rectangular areas having two orthogonal sides common to a part of the sides of the rectangular area, and the first and second parts Focus detection pixels each having a charge storage type photoelectric conversion unit, arranged two-dimensionally in a rectangular region,
The first and second partial rectangular areas are arranged in the respective first and second partial rectangular areas, and the outputs of the focus detecting pixels of the first partial rectangular area and the outputs of the focus detecting pixels of the second partial rectangular area are respectively read out. A first and a second readout circuit;
A control circuit for controlling the charge accumulation of the focus detection pixels in the first partial rectangular area and the charge accumulation of the focus detection pixels in the second partial rectangular area independently of each other;
The first and second partial rectangular regions are spaced apart from each other;
The focus detection pixel in the first partial rectangular area receives a pair of light beams that have passed through the first pair of areas of the pupil of the optical system, and outputs a pair of image signals. And a pair of first photoelectric conversion units, and arranged in an alignment direction of the pair of first photoelectric conversion units,
The focus detection pixels in the second partial rectangular area receive one pair of light beams that have passed through the second pair of areas of the pupil of the optical system, and output a pair of image signals. And having a lens and a pair of second photoelectric conversion units, and arranged in an arrangement direction of the pair of second photoelectric conversion units,
The alignment direction of the pair of first photoelectric conversion units of the focus detection pixels in the first partial rectangular region is the alignment direction of the pair of second photoelectric conversion units of the focus detection pixels in the second partial rectangular region. Unlike
Reading of the focus detection pixel outputs of the first partial rectangular area by the first readout circuit is performed for each of the focus detection pixel columns arranged in the arrangement direction of the pair of first photoelectric conversion units. Scanning is performed in a direction perpendicular to the arrangement direction of the first photoelectric conversion units,
Reading of the focus detection pixel output of the second partial rectangular area by the second readout circuit is performed for each of the focus detection pixel columns arranged in the arrangement direction of the pair of second photoelectric conversion units. An image pickup device that is scanned in a direction perpendicular to the arrangement direction of the second photoelectric conversion units . A rectangular area on a single semiconductor substrate is divided into at least first and second partial rectangular areas having two orthogonal sides common to a part of the sides of the rectangular area, and the first and second parts Focus detection pixels each having a charge storage type photoelectric conversion unit, arranged two-dimensionally in a rectangular region,
The first and second partial rectangular areas are arranged in the respective first and second partial rectangular areas, and the outputs of the focus detecting pixels of the first partial rectangular area and the outputs of the focus detecting pixels of the second partial rectangular area are respectively read out. A first and a second readout circuit;
A control circuit for controlling the charge accumulation of the focus detection pixels in the first partial rectangular area and the charge accumulation of the focus detection pixels in the second partial rectangular area independently of each other;
The first and second partial rectangular regions are spaced apart from each other;
One focus detection pixel in the first partial rectangular area receives one first light flux that has passed through the first pair of areas of the pupil of the optical system and outputs a pair of image signals. A first focus detection pixel including a microlens and a photoelectric conversion unit that receives one of the first pair of light beams, one microlens, and the other of the first pair of light beams. Second focus detection pixels including photoelectric conversion units that receive light are alternately arranged,
The focus detection pixels in the second partial rectangular area receive a second pair of light beams that have passed through a second pair of areas of the pupil of the optical system, and output a pair of image signals. A third focus detection pixel including a microlens and a photoelectric conversion unit that receives one of the second pair of light fluxes, one microlens and the other of the second pair of light fluxes. And fourth focus detection pixels including photoelectric conversion units that receive light are alternately arranged,
The direction of the alternating arrangement of the first and second focus detection pixels in the first partial rectangular area is the direction of the alternating arrangement of the third and fourth focus detection pixels in the second partial rectangular area. Unlike
Reading of the focus detection pixel output of the first partial rectangular area by the first readout circuit is performed for each of the first and second focus detection pixel columns arranged in the alternate arrangement direction. Done in a direction perpendicular to the direction,
Reading of the focus detection pixel output of the second partial rectangular area by the second readout circuit is performed for each of the third and fourth focus detection pixel rows arranged in the alternate arrangement direction. An image sensor that is scanned in a direction perpendicular to a direction . The imaging device according to claim 1 or 2,
A processing circuit for processing the pair of image signals from the focus detection pixels is disposed in a region between the first and second partial rectangular regions on the single semiconductor substrate. element. The imaging device according to any one of claims 1 to 3,
An image pickup device comprising: a second control circuit that simultaneously controls charge accumulation of the focus detection pixels in the first and second partial rectangular regions . The imaging device according to claim 1 or 2 is disposed on a primary image plane of the optical system, and a focus adjustment state of the optical system is determined based on the pair of image signals output from the imaging device. A focus detection device comprising focus detection means for detecting.

Images