JP2008103885A - Imaging device, focus detecting device, and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a pixel output readout circuit of an imaging device from becoming complex. <P>SOLUTION: The imaging device is constituted by arraying pixels for imaging each having a photoelectric conversion unit and pixels for focus detection each having a pair of a first photoelectric conversion unit and a second photoelectric conversion unit in two dimensions. The imaging device has an output unit which outputs a signal, generated by adding together outputs of first photoelectric conversion units 322 and 332 of a first pixel 321 for focus detection and a second pixel 331 for focus detection which are adjacent to each other among the plurality of pixels for focus detection from the first pixel 321 for focus detection and also outputs a signal generated by adding together outputs of second photoelectric conversion units 323 and 333 from the second pixel 331 for focus detection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  A focus detection pixel consisting of a microlens and a pair of photoelectric conversion units arranged behind the microlens is arranged in a partial area of the image sensor, and this image sensor is arranged on the planned focal plane of the optical system to thereby divide the pupil. A focus detection apparatus that detects a focus adjustment state of an optical system using a phase difference detection method is known (see, for example, Patent Document 1).

Prior art documents related to the invention of this application include the following.
Japanese Unexamined Patent Publication No. 01-216306

  In the conventional focus detection apparatus described above, when the output is read out from each pixel of the image sensor, since there are two photoelectric conversion units in the focus detection pixel, in the normal readout sequence, the two photoelectric conversion units have two photoelectric conversion units. There is a problem that signals cannot be read independently.

(1) The invention of claim 1 is an imaging device in which an imaging pixel having a photoelectric conversion unit and a focus detection pixel having a pair of first photoelectric conversion unit and second photoelectric conversion unit are two-dimensionally arranged. The first focus detection pixel is a signal obtained by adding the outputs of the first photoelectric conversion units of the first focus detection pixel and the second focus detection pixel adjacent to each other among the plurality of focus detection pixels. And an output unit that outputs a signal obtained by adding the outputs of the second photoelectric conversion units from the second focus detection pixels.
(2) The image pickup device according to claim 2 includes an address circuit that specifies a position in the arrangement of the image pickup pixel and the focus detection pixel, and the output unit includes an image pickup pixel corresponding to the position specified by the address circuit, or A signal is output from the first focus detection pixel or the second focus detection pixel.
(3) In the imaging device according to claim 3, a plurality of first focus detection pixels and second focus detection pixels are arranged adjacent to each other in the arrangement direction of the first photoelectric conversion unit and the second photoelectric conversion unit.
(4) In the imaging device according to claim 4, the first focus detection pixel and the second focus detection pixel are arranged adjacent to each other in a direction intersecting with the arrangement direction of the first photoelectric conversion unit and the second photoelectric conversion unit. In addition, a plurality of sets of first focus detection pixels and second focus detection pixels are arranged along the alignment direction.
(5) The invention according to claim 5 is based on the image sensor according to any one of claims 1 to 4 and a signal output from the first focus detection pixel and the second focus detection pixel. And a focus detection unit that detects a focus adjustment state of an image formed on the element.
(6) The invention according to claim 6 is based on the image pickup device according to any one of claims 1 to 4 and a signal output from the first focus detection pixel and the second focus detection pixel. A focus detection unit that detects a focus adjustment state of an image formed on the element, and a signal output from the imaging pixel, the first focus detection pixel, and the second focus detection pixel of the image sensor. An imaging apparatus comprising imaging means for generating a signal.

  According to the present invention, an output signal can be read out in units of pixels from focus detection pixels on an image sensor, and it is possible to avoid a complicated image signal read circuit.

  An example in which the imaging apparatus according to an embodiment of the present invention is applied to a digital still camera will be described. FIG. 1 shows the configuration of an embodiment. A digital still camera 201 according to an embodiment includes an interchangeable lens 202 and a camera body 203, and the interchangeable lens 202 is attached to the camera body 203 by a mount unit 204.

  The interchangeable lens 202 includes a lens drive control device 206, a zooming lens 208, a lens 209, a focusing lens 210, a diaphragm 211, and the like. The lens drive control device 206 includes peripheral components such as a microcomputer and a memory. The lens drive control device 206 controls driving of the focusing lens 210 and the aperture 211, detects the state of the aperture 211, the zooming lens 208 and the focusing lens 210, and body drive control described later. Transmission of lens information to the device 214 and reception of camera information are performed.

  The camera body 203 includes an imaging element 212, a body drive control device 214, a liquid crystal display element drive circuit 215, a liquid crystal display element 216, an eyepiece lens 217, a memory card 219, and the like. Pixels, which will be described later, are arranged in a two-dimensional manner on the imaging element 212, and are arranged on the planned imaging plane of the interchangeable lens 202 to capture a subject image formed by the interchangeable lens 202. Although details will be described later, focus detection pixels are arranged at predetermined focus detection positions of the image sensor 212.

  The body drive control device 214 includes a microcomputer and peripheral components such as a memory. The body drive control device 214 reads an image signal from the image sensor 212, corrects the image signal, detects the focus adjustment state of the interchangeable lens 202, and outputs from the lens drive control device 206. It receives lens information, transmits camera information (defocus amount), and controls the operation of the entire digital still camera. The body drive control device 214 and the lens drive control device 206 communicate via the electrical contact portion 213 of the mount portion 204 to exchange various information.

  The liquid crystal display element driving circuit 215 drives a liquid crystal display element 216 of an electronic viewfinder (EVF: electric viewfinder). The photographer can observe an image displayed on the liquid crystal display element 216 via the eyepiece lens 217. The memory card 219 is removable from the camera body 203 and is a portable storage medium that stores and stores image signals.

  The subject image formed on the image sensor 212 through the interchangeable lens 202 is photoelectrically converted by the image sensor 212 and the output is sent to the body drive controller 214. The body drive control device 214 calculates a defocus amount at a predetermined focus detection position based on the output data of the focus detection pixels on the image sensor 212, and sends this defocus amount to the lens drive control device 206. The body drive control device 214 stores an image signal generated based on the output of the image sensor 212 in the memory card 219 and sends the image signal to the liquid crystal display element drive circuit 215 to display an image on the liquid crystal display element 216. Let

  The camera body 203 is provided with operation members (not shown) (shutter buttons, focus detection position setting members, etc.), and the body drive control device 214 detects operation state signals from these operation members. The corresponding operations (imaging operation, focus detection position setting operation, image processing operation) are controlled.

  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 monitors from a lookup table prepared in advance. Select lens information according to the information. The lens drive control device 206 calculates a lens drive amount based on the received defocus amount, and drives the focusing lens 210 to a focal point by a drive source such as a motor (not shown) based on the lens drive amount.

  FIG. 2 shows a region (focus detection area, focus detection position) on which an image is sampled on the screen when a focus detection pixel column described later performs focus detection. A focus detection area 101 is arranged at the center of the screen 100. Focus detection pixels are linearly arranged in the longitudinal direction of the focus detection area indicated by a rectangle.

  FIG. 3 is a front view showing a detailed configuration of the image sensor 212, and shows an enlarged vicinity of the focus detection area on the image sensor 212. In the figure, the vertical and horizontal directions correspond to the vertical and horizontal directions of the screen 100 of FIG. The imaging element 212 includes an imaging pixel 310 for imaging and a focus detection pixel 311 for focus detection.

  As shown in FIG. 4, the imaging pixel 310 includes a microlens 10, a photoelectric conversion unit 11, and a color filter (not shown). There are three types of color filters, red (R), green (G), and blue (B), and each spectral sensitivity has the characteristics shown in FIG. An imaging pixel 310 having each color filter is arranged in a Bayer array.

  On the other hand, the focus detection pixel 311 includes a microlens 10 and a pair of photoelectric conversion units 12 and 13 as shown in FIG. The focus detection pixel 311 is not provided with a color filter in order to increase the amount of light, and the spectral characteristics thereof include the spectral sensitivity of a photodiode that performs photoelectric conversion and the spectral characteristics of an infrared cut filter (not shown) as shown in FIG. Spectral characteristics combining characteristics. This spectral characteristic is a spectral characteristic obtained by adding the spectral characteristics of the green pixel, the red pixel, and the blue pixel shown in FIG. 6, and the light wavelength region of the sensitivity is the light wavelength of the sensitivity of the green pixel, the red pixel, and the blue pixel. Comprehensive area.

  The photoelectric conversion unit 11 of the imaging pixel 310 is designed so as to receive all the light flux that passes through the exit pupil (for example, F1.0) of the brightest interchangeable lens by the microlens 10. In addition, the pair of photoelectric conversion units 12 and 13 of the focus detection pixel 311 are designed to receive a light beam having a predetermined aperture diameter (for example, F2.8) by the microlens 10.

  As shown in FIG. 3, the imaging pixels 310 arranged on the two-dimensional plane are provided with RGB color filters of the Bayer array. The focus detection pixels 311 are linearly arranged in rows where B and G of the imaging pixels 310 are to be arranged in a region corresponding to the focus detection area 101 shown in FIG.

  FIG. 8 shows a cross section 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 an image of the photoelectric conversion unit 11 is projected forward by the microlens 10. The photoelectric conversion unit 11 is formed on the semiconductor circuit substrate 29. A color filter (not shown) is arranged between the microlens 10 and the photoelectric conversion unit 11.

  FIG. 9 shows a cross section 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 images of 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.

  FIG. 10 is an explanatory diagram of focus detection by a pupil division method using a microlens. Reference numeral 90 denotes an exit pupil set at a distance d0 in front of the microlens arranged on the planned imaging plane of the interchangeable lens. The distance d0 is the curvature and refractive index of the microlens and the distance between the microlens and the photoelectric conversion unit. The distance is determined depending on the distance, and is hereinafter referred to as a distance measuring pupil distance. 91 is an optical axis of the interchangeable lens 202, 50 and 60 are microlenses, 52, 53, 62 and 63 are a pair of photoelectric conversion units of focus detection pixels, and 72, 73, 82 and 83 are focus detection light beams. Reference numeral 92 denotes a region of the photoelectric conversion units 52 and 62 projected by the microlenses 50 and 60 (hereinafter referred to as a distance measuring pupil), and 93 denotes a region of the photoelectric conversion units 53 and 63 projected by the microlenses 50 and 60. (Hereinafter referred to as ranging pupil).

  In FIG. 10, for convenience, a focus detection pixel (consisting of a microlens 50 and a pair of photoelectric conversion units 52 and 53) on the optical axis and an adjacent focus detection pixel (a microlens 60 and a pair of photoelectric conversion units 62, 63). However, even when the focus detection pixel is at a position away from the optical axis at the periphery of the screen, the pair of photoelectric conversion units is connected to each microlens from the pair of distance measurement pupils. Receives the light flux coming in The arrangement direction of the focus detection pixels is made to coincide with the arrangement direction of the pair of distance measuring pupils, that is, the arrangement direction of the pair of photoelectric conversion units.

  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 is projected from the microlenses 50 and 60 to the projection distance d0. Projected onto the exit pupil 90 separated by a distance, the projection shape forms distance measuring pupils 92 and 93. The shape of the pair of photoelectric conversion units 62 and 63 arranged behind the microlens 60 is projected onto the exit pupil 90 separated by the projection distance d0, and the projection shape forms the distance measurement pupils 92 and 93. That is, the projection direction of each pixel is determined so that the projection shape (ranging pupils 92 and 93) of the photoelectric conversion unit of each focus detection pixel matches on the exit pupil 90 at the projection distance d0. The pair of distance measurement pupils 92 and 93, the pair of photoelectric conversion units (52 and 53), and the pair of photoelectric conversion units (62 and 63) have a conjugate relationship via the microlenses 50 and 60.

  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 toward 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 the focus detection pixels described above 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 distance measurement 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 pupils 93 is obtained. By applying an image shift detection calculation process (correlation calculation process, phase difference detection process) to be described later to this information, the image shift amount of a pair of images is detected by a so-called pupil division phase difference detection method. Furthermore, by performing a conversion calculation according to the center of gravity distance of the pair of distance measuring pupils to the image shift amount, the current imaging plane with respect to the planned imaging plane (the focal point corresponding to the position of the microlens array on the planned imaging plane) The deviation (defocus amount) of the imaging plane at the detection position is calculated.

  In the above description, the distance measuring pupil is described as being not limited by the aperture opening. However, the distance measuring pupil actually has a shape and size limited by the aperture opening.

  FIG. 11 is a diagram illustrating the relationship between the imaging pixels and the exit pupil. Note that description of similar elements shown in FIG. 10 is omitted. Reference numeral 70 denotes a microlens, 71 denotes a photoelectric conversion unit of an imaging pixel, 81 denotes an imaging light beam, and 94 denotes a region of the photoelectric conversion unit 71 projected by the microlens 70. In FIG. 11, the image pickup pixel (consisting of the microlens 70 and the photoelectric conversion unit 71) on the optical axis 91 is schematically illustrated, but in other image pickup pixels, the photoelectric conversion unit is changed from the region 94 to each microlens. Receives incoming light flux.

  The microlens 70 is disposed in the vicinity of the planned imaging plane of the optical system, and the shape of the photoelectric conversion unit 71 disposed behind the microlens 70 disposed on the optical axis 91 is projected from the microlens 70 to the projection distance d0. The projected shape is projected onto the exit pupil 90 separated by a distance, and the projection shape forms a region 94. The photoelectric conversion unit 71 passes through the region 94 and outputs a signal corresponding to the intensity of the image formed on the microlens 70 by the focus detection light beam 81 directed to the microlens 70. By arranging a large number of such imaging pixels two-dimensionally, image information can be obtained based on the photoelectric conversion unit of each pixel. In the above description, the region 94 is described as being not limited by the aperture opening. However, the region 94 actually has a shape and size limited by the aperture opening.

  FIG. 12 is a diagram for explaining the output relationship of the focus detection pixels. The output relationship between a pair of photoelectric conversion units will be described by taking adjacent focus detection pixels 321 and 331 as an example. The outputs of the photoelectric conversion unit 322 of the focus detection pixel 321 that receives the light beam passing through the distance measuring pupil 92 shown in FIG. 10 and the output of the photoelectric conversion unit 332 of the focus detection pixel 331 are synthesized and added, and the pixel at the position of the focus detection pixel 331 Output as a signal. On the other hand, the outputs of the photoelectric conversion unit 323 of the focus detection pixel 321 and the photoelectric conversion unit 333 of the focus detection pixel 331 that receive the light beam passing through the distance measuring pupil 93 shown in FIG. Are output as pixel signals.

  FIG. 13 is a detailed circuit diagram of the imaging pixel, and FIG. 14 is a plan view showing the element structure of the imaging pixel. The photoelectric conversion unit of the imaging pixel 310 is configured by a photodiode (PD). The electric charge accumulated in the photodiode PD is accumulated in a floating diffusion layer (floating diffusion: FD). The photodiode 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. The reset MOS transistor 510 is turned on by the control signal ΦRn, and the charges accumulated in the FD and PD are cleared to be in a reset state. The output of AMP is connected to the vertical output line 501 via the row selection MOS transistor 512. The row selection MOS transistor 512 is turned on by the control signal ΦSn, and the output of AMP is output to the vertical output line 501.

  FIG. 15 is a detailed circuit diagram of the focus detection pixel, and FIG. 16 is a plan view showing the element structure of the focus detection pixel. Here, description will be given by taking adjacent focus detection pixels 321 and 331 as an example. A pair of photoelectric conversion units of the focus detection pixel 321 includes photodiodes PD1a and PD2a. The pair of photoelectric conversion units of the focus detection pixel 331 includes photodiodes PD1b and PD2b. The charges accumulated in PD1a and PD1b are accumulated in floating diffusion layer (floating diffusion) FDa. The charges accumulated in PD2a and PD2b are accumulated in the floating diffusion layer (floating diffusion) FDb.

  FDa and FDb are connected to the gates of amplifying MOS transistors AMPa and AMPb, and AMPA and AMPb generate a signal corresponding to the amount of charge accumulated in FDa and FDb. FDa and FDb are connected to the power supply voltage Vdd via the reset MOS transistor 510. The reset MOS transistor 510 is turned on by the control signal ΦR3, and the charges accumulated in the FDa, FDb, PDa, and PDb are cleared to be in a reset state. . The outputs of AMPa and AMPb are connected to the vertical output line 501 via the row selection MOS transistor 512. The row selection MOS transistor 512 is turned on by the control signal ΦS3, and the outputs of AMPa and AMPb are output to the vertical output line 501. The

  FIG. 17 is a conceptual diagram showing a circuit configuration of the image sensor. Here, the circuit configuration of the entire image sensor will be described assuming that the number of pixels is 4 pixels × 4 pixels. The pixel arrangement is a 4 × 4 pixel layout. The focus detection pixels 311 are arranged in the second and third columns of the third row, and the other pixels are the imaging pixels 310. The signal holding unit 502 is a buffer that temporarily holds an image signal of pixels for one row, and latches the image signal output to the vertical signal line 501 based on a control signal ΦH generated by the vertical scanning circuit 503.

  The charge accumulation of the imaging pixel 310 is controlled for each row by a control signal (ΦR1 to ΦR4) generated by the accumulation control circuit 504. Output of image signals from the imaging pixel 310 and the focus detection pixel 311 is independently controlled for each row by a control signal (ΦS1 to ΦS4) generated by the vertical scanning circuit 503. The image signal of the pixel selected by the control signal is output to the vertical signal line 501. The image signals held in the signal holding unit 502 are sequentially transferred to the output circuit 505 by the control signals (ΦV1 to ΦV4) generated by the horizontal transfer circuit 505, amplified with the amplification set by the output circuit 506, and output to the outside. Is done.

  FIG. 18 is an operation timing chart of the image sensor shown in FIG. The imaging pixel 310 in the first row is selected by the control signal ΦS1 generated by the vertical scanning circuit 503, and the image signal of the selected imaging pixel 310 is output to the vertical signal line 501. The image signal of the first row output to the vertical signal line 501 is temporarily held in the signal holding unit 502 by the control signal ΦH issued in synchronization with the control signal ΦS1. The image signals of the imaging pixels in the first row held in the signal holding unit 502 are transferred to the output circuit 506 according to the control signals ΦV1 to ΦV4 sequentially issued from the horizontal scanning circuit 505, and the amplification degree set by the output circuit 506 is set. It is output to the outside amplified by.

  When the transfer of the image signal of the imaging pixel 310 in the first row to the signal holding unit is completed, the imaging pixel in the first row is reset by the control signal ΦR1 issued from the accumulation control circuit 504. The next charge accumulation at 310 is started. When the output from the image signal output circuit of the imaging pixel 310 in the first row is completed, the imaging pixel 310 in the second row is selected by the control signal ΦS2 generated by the vertical scanning circuit 503, and the selected imaging pixel 310 is selected. The image signal is output to the vertical signal line 501.

  Thereafter, similarly, the image signal of the image pickup pixel 310 in the second row is retained, the image pickup pixel is reset, and the image signal is output. Subsequently, the image signals of the imaging pixels 310 and the focus detection pixels 311 in the third row are held, the imaging pixels are reset, and the image signals of the imaging pixels 310 and the focus detection pixels 311 are output. Subsequently, the image signal of the imaging pixel 310 in the fourth row is held, the imaging pixel 310 is reset, and the image signal of the imaging pixel 310 is output. Subsequently, the above operation is repeated after returning to the first line. The period Ts from the charge holding timing of the image signal of the imaging pixel 310 of the first row to the charge holding timing of the image signal of the imaging pixel 310 of the next first row is controlled to be constant.

  The charge accumulation time Ti (exposure time) of the imaging pixel 310 and the focus detection pixel 311 is the time from the pixel reset timing to the image signal holding timing. In addition, the charge accumulation time Ti (exposure time) of the imaging pixel 310 and the focus detection pixel 311 can be adjusted by changing the pulse width of the control signals ΦR1 to ΦR4.

  As described above, when the third row is selected, the focus detection pixel 311 arranged in the second column of the third row accumulates in one photoelectric conversion unit of the pair of photoelectric conversion units of the pixel. The combined signal and the signal accumulated in one of the pair of photoelectric conversion units of the adjacent focus detection pixels (third column) are synthesized and added and output to the vertical signal line 501. On the other hand, from the focus detection pixel arranged in the third column of the third row, the signal accumulated in the other photoelectric conversion unit of the pair of photoelectric conversion units of the pixel and the adjacent focus detection pixel (3 A signal accumulated in the other photoelectric conversion unit of the pair of photoelectric conversion units in the column) is synthesized and added and output to the vertical signal line 501.

  As a result, although the focus detection pixels 311 are arranged as a whole in the image pickup device, it is as if all of the image pickup devices from the focus detection pixels 311 have the same image signal readout sequence as that of the image pickup device constituted by the image pickup pixels 310. The image signal can be read out, and the operation control of the image sensor can be prevented from becoming complicated.

  FIG. 19 is a flowchart showing the operation of the digital still camera (imaging device) shown in FIG. When the power of the camera is turned on in step 100, the body drive control device 214 proceeds to step 110 and starts an imaging operation. In step 110, the photographing aperture value automatically determined according to the field luminance measured by a photometer (not shown in FIG. 1), or manually set by the user using an operation member (not shown in FIG. 1). Aperture control information corresponding to the photographic aperture value is sent to the lens drive control device 206, the aperture aperture diameter is set to the photographic aperture value, and the data of the imaged pixels are thinned and read out with this aperture aperture diameter and displayed on the electronic viewfinder. .

  In step 120, data is read from the focus detection pixel array with the aperture diameter set to the photographing aperture value. In step 130, based on a pair of image data corresponding to the focus detection pixel row, an image shift detection calculation process (correlation calculation process) described later is performed to calculate an image shift amount, and a defocus amount is further calculated. In step 140, it is determined whether or not the focus is close, that is, whether or not the absolute value of the calculated defocus amount is within a predetermined value. If it is determined that the focus is not close, 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 focus position, and then the process returns to step 110 to perform the above operation. repeat.

  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, and the focusing lens 210 of the interchangeable lens 202 is driven to scan from infinity to the nearest position, and then step 110 is performed. Return to and repeat the above operation.

  On the other hand, if it is determined that it is in the vicinity of 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). Repeat the above operation. If it is determined that the shutter release has been performed, the aperture control information is transmitted to the lens drive control device 206, and the aperture value of the interchangeable lens 202 is set to the photographing aperture value. When the aperture control is completed, the image sensor 212 is caused to perform an imaging operation, and image data is read from the imaging pixels of the image sensor 212 and all focus detection pixels.

  In step 180, pixel data at each pixel position in the focus detection pixel row is interpolated based on data of surrounding imaging pixels. In the next step 190, 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 110 to repeat the above operation.

Here, details of the image shift amount detection and the defocus amount calculation executed in step 130 of FIG. 19 will be described. A pair of data strings (α1 to αM, β1 to βM, where M is the number of data) output from the focus detection pixel column is subjected to a high frequency cut filter process as shown in Equation (1), and the first data string By generating two data strings (A1 to AN, B1 to BN), noise components and high frequency components that adversely affect the correlation process are removed from the data strings.
An = αn + 2 × αn + 1 + αn + 2,
Bn = βn + 2 × βn + 1 + βn + 2 (1)
In the formula (1), n = 1 to N. Note that this processing can be omitted when the calculation time is shortened or when it is known that the high-frequency component is small because the focus is already largely defocused.

  Here, the data strings α1 to αM represent an image formed by a light beam passing through one of the pair of distance measurement pupils (the distance measurement pupil 92) as one of the pair of photoelectric conversion units of the focus detection pixels (photoelectric conversion). Corresponding to a signal obtained by adding the signal obtained by receiving the light at the unit 12) and the signal obtained by receiving at one of the pair of photoelectric conversion units (photoelectric conversion unit 12) of the adjacent focus detection pixels. . The data strings β1 to βM represent an image formed by a light beam passing through one of the pair of distance measurement pupils (the distance measurement pupil 93) as one of the pair of photoelectric conversion units (photoelectric conversion unit) of the focus detection pixel. 13) corresponds to a signal obtained by adding the signal obtained by receiving light at 13) and the signal obtained by receiving light at one of the pair of photoelectric conversion units (photoelectric conversion unit 13) of the adjacent focus detection pixels.

Next, the correlation calculation shown in the equation (2) is performed on the data strings An and Bn, and the correlation amount C (k) is calculated.
C (k) = Σ | An × Bn + 1 + k−Bn + k × An + 1 | (2)
In equation (2), the Σ operation is accumulated for n, and the range taken by n is limited to a range in which data of An, An + 1, Bn + k, and Bn + 1 + k exist according to the shift amount k. . The 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. 20A, the calculation result of the expression (2) indicates that the correlation amount C (k) is minimal in the shift amount with high correlation between the pair of data (k = kj = 2 in FIG. 20A). (The smaller the value, the higher the degree of correlation). Next, the shift amount x that gives the minimum value C (x) with respect to the continuous correlation amount is obtained by using the three-point interpolation method according to the equations (3) to (6).
x = kj + D / SLOP (3),
C (x) = C (kj) − | D | (4),
D = {C (kj-1) -C (kj + 1)} / 2 (5),
SLOP = MAX {C (kj + 1) -C (kj), C (kj-1) -C (kj)} (6)

  Whether or not the shift amount x calculated by the equation (3) is reliable is determined as follows. As shown in FIG. 20B, when the degree of correlation between a pair of data is low, the minimum value C (x) of the interpolated correlation amount increases. Accordingly, 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. 20C, when the degree of correlation between the pair of data is low and there is no drop in the correlation amount C (k) between the shift ranges kmin to kmax, the minimum value C (x) is obtained. In such a case, it is determined that the focus cannot be detected.

Note that the correlation amount C (k) may be calculated by performing the correlation calculation shown in the following equation instead of the correlation calculation shown in the equation (2).
C (k) = Σ | An / An + 1−Bn + k / Bn + 1 + k | (7)
In equation (7), the Σ operation is accumulated for n, and the range taken by n is limited to a range in which data of An, An + 1, Bn + k, and Bn + 1 + k exist according to the shift amount k. .

When it is determined that the calculated shift amount x is reliable, the defocus amount DEF of the subject image plane with respect to the planned image formation plane can be obtained by Expression (8).
DEF = KX · PY · x (8)
In equation (8), PY is a detection pitch (twice the arrangement pitch of focus detection pixels), and KX is a conversion coefficient determined by the size of the opening angle of the center of gravity of the light beam passing through the pair of distance measurement pupils. Since the magnitude of the opening angle of the center of gravity of the light beam passing through the pair of distance measuring pupils changes according to the size of the aperture opening (aperture value) of the interchangeable lens, it is determined according to the lens information.

<Other examples>
FIG. 21 shows a configuration of an imaging element 212A according to a modification. In the image sensor 212 shown in FIG. 3, as shown in FIG. 12, the signals of the pair of photoelectric conversion units of the focus detection pixels adjacent in the alignment direction of the focus detection pixels are synthesized and added. The focus detection pixel columns are arranged in parallel in the vertical direction, and the signals of the photoelectric conversion units are synthesized and added between the focus detection pixels adjacent in the vertical direction.

  FIG. 22 is a diagram for explaining the output relationship of the focus detection pixels shown in FIG. The output relationship between the pair of photoelectric conversion units will be described using the focus detection pixels 321 and 341 adjacent in the vertical direction as an example. The outputs of the photoelectric conversion unit 322 of the focus detection pixel 321 and the photoelectric conversion unit 342 of the focus detection pixel 341 that receive the light beam passing through the distance measuring pupil 92 shown in FIG. Output as a signal. On the other hand, the outputs of the photoelectric conversion unit 323 of the focus detection pixel 321 and the photoelectric conversion unit 343 of the focus detection pixel 341 that receive the light beam passing through the distance measuring pupil 93 shown in FIG. Are output as pixel signals.

  With such a configuration, the data pitch of the pair of data rows output from the focus detection pixel row becomes the same as the pixel pitch, and becomes smaller than the configuration of the image sensor 212 shown in FIG. Will improve.

  FIG. 23 is a diagram illustrating a circuit configuration of an imaging element according to a modification. In the circuit configuration of the image sensor shown in FIG. 17, the output of the image signal from the image pickup pixel 310 and the focus detection pixel 311 is simultaneously output in units of rows by the control signal (ΦS1 to ΦS4) generated by the vertical scanning circuit 503 and holds the signal. 23, and then sequentially output to the outside by the control signals (ΦV1 to ΦV4) generated by the horizontal transfer circuit 505. In the circuit configuration illustrated in FIG. 23, pixels are selected and selected in units of pixels. The pixel outputs a pixel signal.

  In FIG. 23, a Y address circuit 510 selects a row by a control signal (ΦY1 to ΦY4). The X address circuit 511 selects a column by a control signal (ΦX1 to ΦX4). An image signal of a pixel whose row and column are selected at the same time is output to the vertical signal line 512. The signal is amplified by the amplification set by the output circuit 513 connected to the vertical signal line 512 and output to the outside. In such a circuit configuration, the pixel position can be designated and the pixel can be selected in units of pixels, so that only the pixel signal of the necessary pixel can be read out when necessary, and the pixel signal can be read out at high speed. it can. For example, when only focus detection is performed, only the pixel signal of the focus detection pixel may be read out.

  In the image pickup device shown in FIG. 3, the example in which the image pickup pixel includes the color filter of the Bayer arrangement is shown. However, the configuration and arrangement of the color filter are not limited to this, and the complementary color filters (green: G, yellow: Ye, magenta : Mg, cyan: Cy) may be employed. In this case, the focus detection pixel is arranged at a pixel position where cyan and magenta (including a blue component whose output error is relatively inconspicuous) should be arranged.

  In the image pickup device shown in FIG. 3, an example in which a color filter is not provided in the focus detection pixel is shown. However, even when one filter (for example, a green filter) is provided among the color filters of the same color as the image pickup pixel, The invention can be applied.

  The present invention is not limited to the pupil division type phase difference detection type imaging device using a microlens, and can also be applied to an imaging device having a pixel including a pair of photoelectric conversion units in one pixel. For example, the present invention can be applied to a pupil division type image pickup device using polarized light.

  Further, the imaging apparatus is not limited to a digital still camera or a film still camera in which an interchangeable lens is mounted on the camera body, and can be applied to a lens-integrated digital still camera, a film still camera, or a video camera. Alternatively, the present invention can be applied to a small camera module or a surveillance camera built in a mobile phone or the like. Furthermore, the present invention can also be applied to a focus detection device other than a camera, a distance measuring device, and a stereo distance measuring device.

  As described above, according to one embodiment and its modification, the pixel output by the address circuit is applied to the image sensor in which focus detection pixels having a pair of photoelectric conversion units are arranged in a partial area of the image sensor. Even when reading is performed, signals can be read out in units of pixels by a normal reading sequence, and it is possible to avoid the complexity of the image signal reading circuit.

The figure which shows the structure of one embodiment Figure showing the focus detection area in the screen The figure which shows the detailed structure of an image sensor The figure which shows the structure of an imaging pixel The figure which shows the structure of a focus detection pixel Diagram showing spectral sensitivity characteristics of color filter The figure which shows the spectral sensitivity characteristic of a focus detection pixel Cross section of imaging pixel Cross section of focus detection pixel Illustration of focus detection by pupil division method using microlenses The figure explaining the relationship between an imaging pixel and an exit pupil The figure which shows the output relation of a focus detection pixel Detailed circuit diagram of imaging pixels Plan view showing element structure of imaging pixel Detailed circuit diagram of focus detection pixel Top view showing element structure of focus detection pixel Conceptual diagram showing the circuit configuration of the image sensor Operation timing chart of the image sensor shown in FIG. The flowchart which shows the operation | movement of the digital still camera of one embodiment Illustration of focus detection calculation The figure which shows the structure of the image pick-up element of a modification. The figure which shows the output relationship of the focus detection pixel shown in FIG. The figure which shows the circuit structure of the image pick-up element shown in FIG.

Explanation of symbols

212, 212A Imaging element 214 Body drive control device 310 Imaging pixel 311 Focus detection pixels 11, 12, 13 Photoelectric conversion unit AMPa, AMPb Amplifier

Claims (6)

An imaging element in which an imaging pixel having a photoelectric conversion unit and a focus detection pixel having a pair of first photoelectric conversion unit and second photoelectric conversion unit are two-dimensionally arranged,
A signal obtained by adding the outputs of the first photoelectric conversion units of the first focus detection pixel and the second focus detection pixel adjacent to each other among the plurality of focus detection pixels is output from the first focus detection pixel. An image pickup device comprising: an output unit that outputs and outputs a signal obtained by adding the outputs of the second photoelectric conversion units from the second focus detection pixels. The imaging device according to claim 1,
An address circuit for designating positions of the imaging pixels and the focus detection pixels in the array;
The output unit outputs a signal from the imaging pixel, the first focus detection pixel, or the second focus detection pixel corresponding to a position designated by the address circuit. The imaging device according to claim 1 or 2,
An imaging device, wherein a plurality of sets of the first focus detection pixels and the second focus detection pixels are arranged adjacent to each other in the arrangement direction of the first photoelectric conversion unit and the second photoelectric conversion unit. The imaging device according to claim 1 or 2,
The first focus detection pixel and the second focus detection pixel are disposed adjacent to each other in a direction intersecting with an alignment direction of the first photoelectric conversion unit and the second photoelectric conversion unit, and a plurality of sets of the pixels An image sensor, wherein the first focus detection pixels and the second focus detection pixels are arranged along the alignment direction. The imaging device according to any one of claims 1 to 4,
Focus detection means for detecting a focus adjustment state of an image formed on the image sensor based on signals output from the first focus detection pixel and the second focus detection pixel. Focus detection device. The imaging device according to any one of claims 1 to 4,
Focus detection means for detecting a focus adjustment state of an image formed on the image sensor based on signals output from the first focus detection pixel and the second focus detection pixel;
An image pickup unit configured to generate a signal of the image based on signals output from the image pickup pixel, the first focus detection pixel, and the second focus detection pixel of the image pickup device; Imaging device.

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