JP2010128205A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus achieving quick focus adjustment so that a photographer can surely keep capturing a subject on an observation optical system until imaging. <P>SOLUTION: While a main mirror 205 (beam splitter, half mirror) is inserted in an imaging optical path, a sub mirror 217 (deflection mirror, total reflection mirror) is inserted in the imaging optical path to detect a focusing state by a focus detection sensor 207, and also the sub mirror 217 is retracted to the outside of the imaging optical path to detect the focusing state by a focus detecting pixel column of an imaging device 212. By adjusting the focusing state coarsely or finely by driving a focusing lens 210 or the imaging device 212 according to the result of the focusing state detected by the focus detection sensor 207 and the focus detecting pixel column of the imaging device 212, focusing is rapidly and accurately performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus including a focus adjustment unit.

For example, an imaging apparatus as disclosed in Patent Document 1 is known. In the imaging apparatus, a light beam coming from the photographing optical system is branched by a main mirror (half mirror). One of the branched light beams is guided to an observation optical system (viewfinder) so that the focus adjustment state of the photographing optical system can be observed visually. The light beam that has passed through the main mirror, which is the other branched light beam, is deflected by the sub-mirror (total reflection mirror) and guided to the focus detection means of the pupil division phase difference detection method, and the focus detection means performs the focus of the photographing optical system. An adjustment state is detected, and focus adjustment (coarse adjustment) of the photographing optical system is performed based on the detection result. Thereafter, the main mirror and the sub mirror are withdrawn from the photographing optical path, and an image formed by the photographing optical system is picked up by the image pickup element arranged on the planned focal plane of the photographing optical system, and an image signal is obtained. Image sharpness detection (contrast detection) is performed based on the image signal, and the focus adjustment state of the photographing optical system is detected based on the sharpness. Based on the detection result, focus adjustment (fine adjustment) of the photographic optical system is performed. Finally, the image pickup device picks up an image formed by the photographic optical system, and the obtained image signal is stored.
JP 2006-106173 A

  However, in the imaging apparatus described in Patent Document 1 described above, after performing focus adjustment based on the focus adjustment state detection result, the main mirror and the sub mirror are both retracted from the imaging optical path to perform focus adjustment. Therefore, it takes a long time (blackout time) from when the main mirror and the sub mirror are both retracted from the photographing optical path until the actual imaging is performed, and it is difficult for the photographer to keep capturing the subject in the viewfinder reliably. At the same time, quick focus adjustment operation could not be performed.

An image pickup apparatus according to a first aspect of the present invention includes an image pickup pixel that outputs a signal for generating image data corresponding to an image formed by an image pickup optical system, and a focus that outputs a signal for detecting a focus state of the image. An imaging device in which a detection pixel is arranged, and a first light beam that is arranged in a photographing optical path between the imaging optical system and the imaging device and that passes a light flux coming from the imaging optical system along the photographing optical path. A beam splitter that divides the light beam into a second light beam that branches off the optical path, an observation optical system that observes an image formed by the second light beam, and an insertion into the photographing optical path and a retraction out of the photographing optical path are arranged. And a deflection mirror that deflects the first light beam out of the photographing optical path when inserted into the photographing optical path, and the first light beam deflected out of the photographing optical path by the deflection mirror, and is formed by the first light flux. The focus of the image Based on a signal output from the focus detection pixel, the first focus detection means for detecting the image by the pupil division type phase difference detection method and the focus state of the image formed by the first light flux coming along the photographing optical path The second focus detection means, and a control means for individually controlling the detection of the focus state by the first focus detection means and the second focus detection means according to the arrangement state of the deflection mirrors.
An image pickup apparatus according to a thirteenth aspect of the present invention is an image pickup pixel that outputs a signal for generating image data corresponding to an image formed by an image pickup optical system, and a focus that outputs a signal for detecting the focus state of the image. An imaging device in which a detection pixel is arranged, and a first light beam that is arranged in a photographing optical path between the imaging optical system and the imaging device and that passes a light flux coming from the imaging optical system along the photographing optical path. A beam splitter that splits into a second light beam that branches off the optical path, an observation optical system that observes an image formed by the second light beam, a deflection mirror that deflects the first light beam outside the imaging optical path, and a deflection by the deflection mirror A first focus detecting means for receiving the first light flux and detecting a focus state of an image formed by the first light flux by a pupil division type phase difference detection method; and a first light flux arriving along the photographing optical path. Formed Second focus detection means for detecting the focus state of the image based on a signal output from the focus detection pixel, beam splitter driving means for inserting the beam splitter into the imaging optical path and withdrawing out of the imaging optical path, A deflection mirror driving means for inserting the deflection mirror into the imaging optical path and retracting the imaging mirror out of the imaging optical path, and the deflection mirror inserted into the imaging optical path with the beam splitter inserted into the imaging optical path. The beam splitter driving unit and the deflecting mirror driving unit are controlled so as to retract to the outside, and the focus state is detected by the first focus detecting unit and the second focus detecting unit according to the arrangement state of the beam splitter and the deflecting mirror. And a control means for individually controlling.

  According to the present invention, it is possible to provide an imaging apparatus that enables a photographer to reliably keep capturing an object in the observation optical system immediately before photographing and that can perform quick focus adjustment.

  An embodiment of an image pickup apparatus according to the present invention will be described by taking a lens interchangeable digital still camera as an example. FIG. 1 is a cross-sectional view showing a configuration of a digital still camera 201 as an embodiment. The digital still camera 201 includes an interchangeable lens 202 and a camera body 203, and the interchangeable lens 202 is attached to the camera body 203 via a mount unit 204. An interchangeable lens 202 having various photographing optical systems (imaging optical systems) can be attached to the camera body 203 via a mount unit 204.

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

  The lens drive control device 206 adjusts the aperture diameter of the aperture 211 via the aperture drive unit 231, drives the zooming lens 208 via the zoom drive unit 232, performs zooming, and performs focusing via the focus lens drive unit 233. The lens 210 is driven to adjust the focus.

  The focus lens driving unit 233 includes a motor and a speed reduction mechanism (consisting of a gear, a helicoid, and the like), and performs focusing by driving the focusing lens 210 at a high speed.

  The lens drive control device 206 updates the lens information according to the focus adjustment state, zooming state, aperture diameter adjustment state, aperture opening F value, and the like. Specifically, the positions of the zooming lens 208 and the focusing lens 210 and the aperture value of the aperture 211 are detected, and lens information is calculated according to these lens positions and aperture values, or prepared in advance. Lens information corresponding to the lens position and aperture value is selected from the lookup table. The lens drive control device 206 transmits lens information to the body drive control device 214 via an electrical contact 213 provided on the mount unit 204.

  The lens drive control device 206 calculates a lens drive amount based on the focus adjustment information (defocus amount) received from the body drive control device 214, and the focusing lens 210 via the focus lens drive means 233 according to the lens drive amount. To the in-focus position. Further, the lens drive control device 206 drives the diaphragm 211 in accordance with the received diaphragm value.

  A camera body 203 includes a main mirror 205 (beam splitter, half mirror) and sub mirror 217 (deflection mirror, total reflection mirror), an optical finder 216 (observation optical system, view finder), and an image sensor 212 that can be inserted / retracted in the photographing optical path. , A focus detection sensor 207, a body drive control device 214, and a circuit associated therewith.

  The light flux from the subject coming from the interchangeable lens 202 through the opening of the mount unit 204 is branched and guided to the optical finder 216 including a pentaprism and an eyepiece by the main mirror 205 inserted in the photographing optical path. The subject can be optically observed through the optical finder 216.

  On the other hand, the light beam from the subject that has passed through the main mirror 205 is deflected by the sub-mirror 217 inserted in the photographing optical path and guided to the focus detection sensor 207. The focus detection sensor 207 has a configuration of a focus detection device of a re-imaging pupil division type phase difference detection method, and an output signal of the focus detection sensor 207 is processed by the body drive control device 214, and the phase difference detection method is used. The focus adjustment state of the subject image is detected. Details of the focus detection sensor 207 will be described later.

  Insertion / retraction of the main mirror 205 and the sub mirror 217 into the photographing optical path is performed independently by the mirror driving means 234 based on an instruction from the body drive control device 214.

  The imaging element 212 has two-dimensionally arranged imaging pixels, and a focus detection pixel is incorporated in a portion corresponding to the focus detection position, and an output signal of the focus detection pixel is processed by the body drive control device 214. Thus, the focus adjustment state of the subject image is detected by the re-imaging pupil division type phase difference detection method. Details of the image sensor 212 will be described later.

  The imaging element 212 is supported so as to be movable within a predetermined movable range in the optical axis direction of the interchangeable lens, and is driven in the optical axis direction by the imaging element driving means 235 based on an instruction from the body drive control device 214, thereby High-precision focus adjustment can be performed.

  The image sensor driving means 235 is composed of a motor, a speed reduction mechanism (consisting of gears and helicoids) and a piezoelectric actuator, and is configured to enable high-precision focus adjustment compared to the focus lens driving means 233. However, the movable range is narrower than the movable range of the focus lens driving means 233.

  In this specification, the focus adjustment based on the focus detection result by the focus detection sensor 207 is referred to as “dedicated AF (Autofocus)”. On the other hand, focus adjustment based on the focus detection result by the focus detection pixel array of the image sensor 212 is referred to as “image sensor AF” as focus adjustment by the image sensor.

  The body drive control device 214 includes a microcomputer, a memory, a timer, a drive control circuit, and the like. The body drive control device 214 controls the drive of the image sensor 212, reads out the image signal and the focus detection signal, drives the focus detection sensor 207, and controls the focus detection signal. The focus detection calculation based on the readout and focus detection signal, and the focus adjustment by driving the focusing lens 210 or the image sensor 212 based on the focus detection result are repeatedly performed, and image signal processing and recording, camera operation control, and the like are performed. The body drive control device 214 communicates with the lens drive control device 206 via the electrical contact 213 to receive lens information and send camera information (defocus amount, aperture value, etc.).

  The external operation means 220 is a means for the photographer to select a focus detection area and an AF mode, which will be described later, and the body drive control device 214 performs a focus adjustment operation according to the selected focus detection area and the selected AF mode. Switch.

  The external operation means 221 has a first stage operation state and a second stage operation state, and a second stage in which the photographer instructs the photographing operation through a first stage operation (half-press) instructing the start of the focus adjustment operation. It leads to operation (full press).

  The body drive control device 214 controls the focus adjustment operation / shooting operation according to the operation state of the external operation means 221. The body drive control device 214 calculates a defocus amount based on output signals from the image sensor 212 and the focus detection sensor 207, and sends the defocus amount to the lens drive control device 206. The body drive control device 214 processes image signals from the image sensor 212 to generate image data, stores the image data in the memory card 219, and causes the liquid crystal display element 215 to display an image based on the image data. Further, the body drive control device 214 sends aperture control information to the lens drive control device 206 to control the aperture of the aperture 211.

  FIG. 2 is a diagram showing a focus detection position on the shooting screen of the interchangeable lens 202, and a focus detection pixel array on the imaging element 212 described later is a focus that is an area where an image is sampled on the shooting screen when focus detection is performed. The detection area is indicated by P0 (thick line), and the areas to be sampled by the focus detection sensor 207 are indicated by P1, P2, and P3. In this example, focus detection areas P 1, P 2, and P 3 are arranged at the center and three left and right positions on the rectangular shooting screen 100, and the focus detection areas P 0 are arranged on the shooting screen 100 in a grid pattern. A part of the focus detection area P0 is arranged so as to overlap the focus detection areas P1, P2, and P3.

  When focus detection is performed using the output signal of the focus detection pixel array on the image sensor 212, focus detection is performed using an output signal corresponding to a part of the focus detection area P0 arranged in a grid pattern. For example, focus detection is performed using the output signal of the focus detection area P0 in a portion superimposed on the focus detection area P1.

  FIG. 3 is a front view showing a detailed configuration of the image sensor 212, and is an enlarged view of a part of the image sensor 212 corresponding to the region 101 of FIG. In the imaging device 212, the imaging pixels 310 are densely arranged in a two-dimensional square lattice pattern (Bayer arrangement including green pixels, red pixels, and blue pixels), and a focus detection focus is provided at a position corresponding to the focus detection area. The detection pixels 313 and 314 are alternately arranged on a straight line. The focus detection pixels 313 and 314 are disposed at positions where the blue pixel and the green pixel of the imaging pixel 310 are to be disposed, respectively.

  3 shows the focus detection pixel arrangement corresponding to the focus detection area in the vertical direction, the focus detection pixel arrangement corresponding to the focus detection area in the horizontal direction is equivalent to that obtained by rotating FIG. 3 by 90 degrees.

  As illustrated 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 the respective spectral sensitivities have the characteristics shown in FIG. In the imaging device 212, a red pixel, a green pixel, and a blue pixel, which are imaging pixels 310 having respective color filters, are arranged in a Bayer array.

  FIG. 5 is a diagram showing the configuration of the focus detection pixels in the focus detection pixel array shown in FIG. 3, and the focus detection pixel 313 includes the microlens 10, the photoelectric conversion unit 13, and the like as shown in FIG. The photoelectric conversion unit 13 has a rectangular shape. Further, the focus detection pixel 314 includes the microlens 10 and the photoelectric conversion unit 14 as illustrated in FIG. 5B, and the photoelectric conversion unit 14 has a rectangular shape. If the microlens 10 of the focus detection pixel 313 and the microlens 10 of the focus detection pixel 314 are overlapped and illustrated, the photoelectric conversion units 13 and 14 are in a positional relationship in the vertical direction.

  5A and 5B show the configuration of the focus detection pixels in the focus detection pixel array corresponding to the focus detection area in the vertical direction, but in the focus detection pixel array corresponding to the focus detection area in the horizontal direction. The configuration of the focus detection pixel is obtained by rotating FIGS. 5A and 5B by 90 degrees.

  The focus detection pixels 313 and 314 are not provided with a color filter to increase the amount of light, and the spectral characteristics of the focus detection pixels 313 and 314 include the spectral sensitivity of a photodiode that performs photoelectric conversion and the spectral characteristics of an infrared cut filter (not shown). Spectral characteristics (see FIG. 7). That is, the spectral characteristics are 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 includes the light wavelength regions of the sensitivity of the green pixel, the red pixel, and the blue pixel. ing.

  The focus detection pixels 313 and 314 for focus detection are arranged in a column where the blue pixel and the green pixel of the imaging pixel 310 should be arranged. The focus detection pixels 313 and 314 for focus detection are arranged in the column where the blue pixel and the green pixel of the imaging pixel 310 are to be arranged in order to obtain an image signal for imaging at the position of the focus detection pixel. This is because when an interpolation error occurs in the interpolation process, the blue pixel interpolation error is less conspicuous than the red pixel interpolation error due to human visual characteristics.

  The photoelectric conversion unit 11 of the imaging pixel 310 is designed so as to receive all the light beams that pass through the exit pupil diameter (for example, F1.0) of the brightest interchangeable lens by the microlens 10. In addition, the photoelectric conversion units 13 and 14 of the focus detection pixels 313 and 314 are shaped so that the microlens 10 receives approximately half of the luminous flux that passes through the exit pupil diameter (for example, F1.0) of the brightest interchangeable lens. Designed.

  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 shape 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. 9A is a cross-sectional view of the focus detection pixel 313 shown in FIG. In the focus detection pixel 313 arranged corresponding to the focus detection area 101 in the center of the screen in FIG. 2, the microlens 10 is arranged in front of the photoelectric conversion unit 13 (leftward in FIG. 9A). 10, the shape of the photoelectric conversion unit 13 is projected forward. The photoelectric conversion unit 13 is formed on the semiconductor circuit substrate 29, and the microlens 10 is integrally and fixedly formed in front of the photoelectric conversion unit 13 by a semiconductor image sensor manufacturing process.

  FIG. 9B is a cross-sectional view of the focus detection pixel 314 shown in FIG. In the focus detection pixel 314 arranged corresponding to the focus detection area 101 in the center of the screen in FIG. 2, the microlens 10 is arranged in front of the photoelectric conversion unit 14 (leftward in FIG. 9B). 10, the shape of the photoelectric conversion unit 14 is projected forward. The photoelectric conversion unit 14 is formed on the semiconductor circuit substrate 29, and the microlens 10 is integrally and fixedly formed in front of the photoelectric conversion unit 14 by a semiconductor image sensor manufacturing process.

  FIG. 10 shows a configuration of a pupil division type phase difference detection type focus detection optical system using a microlens. The focus detection pixel portion is shown in an enlarged manner. In FIG. 10, the exit pupil 90 is set at a position of a distance d forward from the microlens 10 disposed on the planned imaging plane of the interchangeable lens 202 (see FIG. 1). This 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 referred to as a distance measuring pupil distance in this specification. Reference numeral 91 is an optical axis of the interchangeable lens, reference numerals 10a to 10d are microlenses, reference numerals 13a, 13b, 14a, and 14b are photoelectric conversion units, reference numerals 313a, 313b, 314a, and 314b are focus detection pixels, reference numerals 73, 74, 83, and Reference numeral 84 denotes a focus detection light beam.

  Reference numeral 93 denotes an area of the photoelectric conversion units 13a and 13b projected by the micro lenses 10a and 10c, and is referred to as a distance measuring pupil in this specification. In FIG. 10, an elliptical region is illustrated for easy understanding, but in reality, the shape of the photoelectric conversion units 13 a and 13 b is an enlarged projection shape. Similarly, reference numeral 94 denotes an area of the photoelectric conversion units 14a and 14b projected by the microlenses 10b and 10d, which is a distance measuring pupil. In FIG. 10, an elliptical region is shown for easy understanding, but the shape of the photoelectric conversion units 14a and 14b is actually a magnified shape.

  In FIG. 10, four focus detection pixels 313a, 313b, 314a, and 314b adjacent to the optical axis 91 of the interchangeable lens are schematically illustrated, but the other focus detection pixels in the focus detection area 101 may also be displayed on the screen. Also in the focus detection pixels in the focus detection areas 102 and 103 in the peripheral portion, the photoelectric conversion unit is configured to receive the light flux that arrives at each microlens through the corresponding distance measurement pupils 93 and 94, respectively. The arrangement direction of the focus detection pixels is made to coincide with the arrangement direction of the pair of distance measuring pupils 93 and 94, that is, the arrangement direction of the pair of photoelectric conversion units 13a and 14a (or 13b and 14b).

  The microlenses 10a to 10d are disposed in the vicinity of the planned image plane of the interchangeable lens 202 (see FIG. 1), and the photoelectric conversion unit 13a disposed behind (by the right in FIG. 10) the microlenses 10a to 10d. , 13b, 14a, and 14b are projected onto the exit pupil 90 separated from the microlenses 10a to 10c by the distance measurement pupil distance d, and the projection shapes form the distance measurement pupils 93 and 94. That is, the microlens in each focus detection pixel is matched with the projection shape (ranging pupils 93 and 94) of the photoelectric conversion unit of each focus detection pixel on the exit pupil 90 at the distance pupil distance d from the microlens. The relative positional relationship of the photoelectric conversion units is determined, and thereby the projection direction of the photoelectric conversion unit of each focus detection pixel is determined.

  The photoelectric conversion unit 13a outputs a signal corresponding to the intensity of the image formed on the microlens 10a by the light flux 73 that passes through the distance measuring pupil 93 and arrives at the microlens 10a. Similarly, the photoelectric conversion unit 13b outputs a signal corresponding to the intensity of the image formed on the microlens 10c by the light beam 83 that passes through the distance measuring pupil 93 and arrives at the microlens 10c. Further, the photoelectric conversion unit 14a outputs a signal corresponding to the intensity of the image formed on the microlens 10b by the light flux 74 that passes through the distance measuring pupil 94 and arrives at the microlens 10b. Similarly, the photoelectric conversion unit 14b outputs a signal corresponding to the intensity of the image formed on the microlens 10d by the light beam 84 that passes through the distance measuring pupil 94 and arrives at the microlens 10d.

  A large number of the two types of focus detection pixels described above are arranged in a straight line, and the output of the photoelectric conversion unit of each pixel is grouped into a distance measurement pupil 93 and an output group corresponding to the distance measurement pupil 94, thereby measuring the distance measurement pupil 93 and the measurement pupil 93. Information on the intensity distribution of the pair of images formed on the pixel array by the focus detection light beams that respectively pass through the distance pupil 94 is obtained. By applying an image shift detection calculation process (correlation calculation process, phase difference detection process) described later to this information, the image shift amount of a pair of images by the pupil division type phase difference detection method is detected. Furthermore, by performing a conversion operation according to the center of gravity distance between the pair of distance measuring pupils, the current image plane (corresponding to the position of the microlens array) is used to detect the focus on the shooting screen. The deviation (defocus amount) of the imaging plane corresponding to the position is calculated.

  The configuration and focus detection operation of the focus detection sensor 207 of the re-imaging pupil division type phase difference detection method will be described with reference to FIG. FIG. 11 is a view of the configuration of the focus detection sensor 207 including three re-imaging optical system units corresponding to the focus detection areas P1, P2, and P3 shown in FIG. 2, as viewed from above in FIG. In FIG. 11, reference numeral 91 is an optical axis of the interchangeable lens, reference numerals 110 and 120 are condenser lenses, reference numerals 111 and 121 are aperture masks, 112, 113, 122, and 123 are aperture mask openings, and reference numerals 114, 115, 124, and 125 are Re-imaging lenses 116 and 126 are focus detection image sensors (CCDs).

  Reference numerals 132, 133, 142, and 143 denote focus detection light beams. The exit pupil 90 is set at a position of a distance d forward from the planned imaging plane of the interchangeable lens. Here, the distance d is a distance determined according to the focal length of the condenser lenses 110 and 120 and the distance between the condenser lenses 110 and 120 and the aperture openings 112, 113, 122, and 123. This is called the pupillary distance. This distance measuring pupil distance d is set to be approximately equal to the distance d in FIG. Reference numeral 192 denotes a region of the aperture openings 112 and 122 projected by the condenser lenses 110 and 120, and is hereinafter referred to as a distance measuring pupil. Similarly, reference numeral 193 denotes a region of the aperture openings 113 and 123 projected by the condenser lenses 110 and 120, and is hereinafter referred to as a distance measuring pupil. The condenser lens 110, the diaphragm mask 111, the diaphragm mask apertures 112 and 113, the re-imaging lenses 114 and 115, and the image sensor 116 perform focus detection at one position, and a re-imaging pupil division type phase difference detection type focus detection unit. Configure.

  FIG. 11 schematically illustrates a focus detection unit that is on the optical axis 91 of the interchangeable lens and a focus detection unit that is not on the optical axis 91 of the interchangeable lens. By combining a plurality of focus detection units, it is possible to realize a focus detection device that performs focus detection by the re-imaging pupil division type phase difference detection method in the three focus detection areas P1, P2, and P3 shown in FIG. .

  The focus detection unit including the condenser lens 110 includes a condenser lens 110 disposed in the vicinity of a planned imaging plane of the interchangeable lens, an imaging element 116 disposed behind (on the right side in FIG. 11), the condenser lens 110 and the imaging element. 116 and a pair of re-imaging lenses 114 and 115 for re-imaging a primary image formed in the vicinity of a predetermined imaging plane on the image sensor 116, in the vicinity of the pair of re-imaging lenses ( The aperture mask 111 has a pair of aperture mask openings 112 and 113 arranged on the left side in FIG.

  The image sensor 116 is a line sensor in which a plurality of photoelectric conversion units are densely arranged along a straight line, and the arrangement direction of the photoelectric conversion units is the alignment direction of a pair of distance measurement pupils (that is, the alignment direction of the aperture openings). Match. Information corresponding to the intensity distribution of the pair of images re-imaged on the image sensor 116 is output from the image sensor 116, and an image shift detection calculation process (correlation calculation process, phase difference) described later is performed on this information. By performing the detection process, the image shift amount of the pair of images by the re-imaging pupil division type phase difference detection method is detected. Further, the deviation (defocus amount) of the current imaging plane with respect to the planned imaging plane is calculated by multiplying the image shift amount by a predetermined conversion coefficient.

  The image sensor 116 is projected onto the planned imaging plane by the re-imaging lenses 114 and 115, and the detection accuracy of the defocus amount (image deviation amount) is determined by the detection pitch of the image deviation amount (re-imaging pupil division type position). In the case of the phase difference detection method, it is determined by the arrangement pitch of the photoelectric conversion units projected on the planned imaging plane.

  The condenser lens 110 projects the aperture mask openings 112 and 113 of the aperture mask 111 as regions 192 and 193 on the exit pupil 90. Regions 192 and 193 are called distance measurement pupils. That is, a pair of images re-imaged on the image sensor 116 is formed by a light beam that passes through the pair of distance measuring pupils 192 and 193 on the exit pupil 90. The light beams 132 and 133 that pass through the pair of distance measuring pupils 192 and 193 on the exit pupil 90 are referred to as focus detection light beams.

  FIG. 12 is a diagram comparing the distance measurement pupils 93 and 94 of the image sensor AF on the exit pupil 90 with the distance measurement pupils 192 and 193 of the dedicated AF. Note that the focus detection pixel array direction in the image sensor AF in this case is the horizontal direction in FIG. 2, and the alignment direction of the pair of distance measurement pupils is aligned with the alignment direction of the pair of distance measurement pupils of the dedicated AF.

  In FIG. 12, the distance measuring pupils 93 and 94 of the image sensor AF are set so as to include the aperture F1.0. On the other hand, the distance measuring pupils 192 and 193 of the dedicated AF are set so as to enter the opening F5.6. This is to prevent the vignetting of the focus detection light beam when any interchangeable lens is used in an interchangeable lens system in which the open F values of all the interchangeable lenses are brighter than F5.6.

  In the pupil division type phase difference detection method, a shift amount of a pair of images (a shift amount in a direction perpendicular to the optical axis) formed by a pair of focus detection light beams passing through a pair of distance measuring pupils is detected, Focus detection is performed by converting the image shift amount into a defocus amount in the optical axis direction.

  In dedicated AF, focus detection is performed according to the shift amount of a pair of images formed by a pair of focus detection light beams that pass through a pair of distance measuring pupils 192 and 193 having a narrow center-of-gravity distance between each other. The amount can be detected.

  On the other hand, in the image sensor AF, since the focus detection is performed according to the shift amount of the pair of images formed by the pair of focus detection light beams that pass through the pair of distance measuring pupils 93 and 94 having a large center-to-center distance, detection of the defocus amount is performed. Accuracy is improved.

  In addition, regarding the detection pitch of the image on the planned imaging plane, the detection pitch of the image sensor AF is twice the pixel pitch, and the detection pitch of the dedicated AF is determined by the re-imaging lens. This is the pitch when projected onto the image plane. By making the detection pitch of the image sensor AF smaller than the detection pitch of the dedicated AF, the detection accuracy of the defocus amount of the image sensor AF is further improved.

  FIG. 13 is a flowchart showing the imaging operation of the digital still camera 201 of the present embodiment. In step S10, when the external operation means 221 is operated by the photographer to enter the first stage operation state in step S10, the body drive control device 214 is set by the external operation means 220 in step S20. In accordance with the AF mode thus set, the process branches to the one-shot AF mode in step S100, the continuous AF mode in step S300, the high-precision AF mode in step S500, and the high-speed continuous shooting AF mode in step S700.

  The one-shot AF mode is an AF mode that locks the focus adjustment operation once focus is detected, and the continuous AF mode is an AF mode that always continues quick focus adjustment operation regardless of the focus. The high-precision AF mode is an AF mode in which high-precision continuous focus adjustment operation is continued regardless of the focus, and the high-speed continuous shooting mode is an AF mode in which a focus adjustment operation suitable for high-speed continuous shooting is performed.

  When branching to the one-shot AF mode, the operation starts from step S100 in FIG. If the main mirror 205 and the sub mirror 217 are retracted from the photographing optical path in step S110, the main mirror 205 and the sub mirror 217 are inserted into the photographing optical path. In step S <b> 120, the position of the image sensor 212 is reset, and the image sensor 212 is positioned at the center of the movable range by the image sensor driving means 235. In step S130, data is read from the focus detection area (AF area) of the dedicated AF. The AF area is previously selected by the photographer by the external operation means 220.

  In step S140, an image shift amount is calculated based on the data read from the AF area of the dedicated AF. In step S150, the image shift amount is converted into a defocus amount. Details of steps S140 and S150 will be described later.

  In step S160, based on the calculated defocus amount, it is determined whether or not the focus is close to the focus. If the focus is not close, the process proceeds to step S170, and the defocus amount is transmitted to the lens drive control device (lens CPU) 206. The focusing lens 210 of the interchangeable lens 202 is driven to the in-focus position. Then, it returns to step S130 and repeats the operation | movement mentioned above. If it is determined that the focus is close, only the sub mirror 217 is retracted from the imaging optical path in step S180, and the state shown in FIG. 15 is obtained.

  In step S190, data is read out from the AF area of the image sensor AF (the AF area selected by the photographer and coincides with the AF area of the dedicated AF). In step S200, an image shift amount is calculated based on the data read from the AF area of the image sensor AF. In step S210, the image shift amount is converted into a defocus amount. Details of steps S200 and S210 will be described later.

  In step S220, based on the calculated defocus amount, it is determined whether or not it is in focus. If not in focus, the process proceeds to step S230 to determine whether the defocus amount is within the movable range of the image sensor 212. If not, the sub mirror 217 is inserted into the photographing optical path in step S240, and the process returns to step S130 to repeat the above-described operation. If within the movable range, the image sensor 212 is moved in the optical axis direction in accordance with the defocus amount in step S250.

  FIG. 16 is a diagram schematically showing the movable range of the focusing lens 210 and the movable range of the image sensor 212. The movable range of the focusing lens 210 ranges from the closest shooting distance to infinity (∞) (FIG. 16). 16 (a)), the movable range of the image sensor 212 is narrower than the movable range of the focusing lens 210 (FIG. 16B).

  When the focusing lens 210 is driven by the focus adjustment of the dedicated AF and enters the vicinity of the focus, the lens position is the center (reset position) of the movable range of the image sensor 210 and is detected by the image sensor AF. The image sensor 212 is moved within the movable range in accordance with the defocus amount. When the moving position (focus position) of the image sensor 212 based on the defocus amount detected with respect to the current position Cp of the image sensor 212 falls within the movable range (FIG. 16C), the image sensor 212 is deselected. Move according to the focus amount. When the movement position (focus position) of the image sensor 212 based on the defocus amount detected with respect to the current position Cp of the image sensor 212 does not fall within the movable range (FIG. 16D), the image sensor 212 is moved. Focus adjustment by dedicated AF without moving.

  In FIG. 14, if it is determined in step S220 that the subject is in focus, in step S260, the photographer takes the external operation means 221 into the second stage operation state, and waits for an instruction for shutter release. In response to the shutter release instruction, in step S270, the main mirror 205 is retracted from the photographing optical path, and an aperture adjustment command is transmitted to the lens drive control device 206, so that the aperture value of the interchangeable lens 202 is controlled by the control F value (shooter or F value set automatically). When the aperture control is completed, the image sensor 212 is caused to perform an image capturing operation in step S280, and image data is read from the image capturing pixel 310 and all focus detection pixels 313 and 314 of the image capturing element 212.

  In step S290, the image data is subjected to predetermined processing (for example, pixel data at each pixel position in the focus detection pixel row is interpolated based on data of imaging pixels around the focus detection pixel), and then the image data is stored in the memory. It memorize | stores in the card | curd 219, returns to step S110, and repeats the operation | movement mentioned above.

  In the above flow, when the defocus amount is outside the movable range of the image sensor in step S230, the process returns to step S130 through step S240, and the focus adjustment by the dedicated AF is performed. After transmitting to the lens drive control device 206 and driving the focusing lens 210 of the interchangeable lens 202 to the in-focus position, the process may return to step 190 to continue the focus adjustment by the image sensor AF. In this way, the insertion and withdrawal of the sub mirror 217 can be omitted, so that a quick focus adjustment operation can be achieved.

  In the one-shot AF mode, after the main mirror 205 and the sub mirror 217 are inserted into the photographing optical path, focus detection is performed by the dedicated AF to perform the first stage focus adjustment (coarse adjustment), and then the sub mirror 217 is moved from the photographing optical path. The second stage of focus adjustment (fine adjustment) is performed by retracting and performing focus detection by the image sensor AF. Even when the photographer is instructed to start the focus detection operation, even when the focus is greatly defocused, it is possible to reliably detect the focus and quickly bring it into the in-focus state. In addition to achieving focus, the photographer can continue to capture the subject image with the optical viewfinder until shutter release.

  When branching to the continuous AF mode, the operation starts from step S300 in FIG. In step S <b> 310, the position of the image sensor 212 is reset, and the image sensor 212 is positioned at the center of the movable range by the image sensor driving means 235. If the main mirror 205 and the sub mirror 217 are retracted from the photographing optical path in step S320, the main mirror 205 and the sub mirror 217 are inserted into the photographing optical path.

  In step S330, data is read from the AF area of the dedicated AF. The AF area is previously selected by the photographer by the external operation means 220. In step S340, an image shift amount is calculated based on the data read from the AF area of the dedicated AF. In step S350, the image shift amount is converted into a defocus amount. Details of steps S340 and S350 will be described later.

  In step S360, the calculated defocus amount is transmitted to the lens drive control device (lens CPU) 206, and the focusing lens 210 (imaging optical system) of the interchangeable lens 202 is driven to the in-focus position.

  In step S370, it is determined whether the photographer has placed the external operation means 221 in the second stage operation state and the shutter release is instructed. If there is no shutter release instruction, the process returns to step S330 to repeat the above-described operation.

  If there is an instruction for shutter release, in step S380, the main mirror 205 and the sub mirror 217 are retracted from the photographing optical path, and an aperture adjustment command is transmitted to the lens drive control unit 206 to control the aperture value of the interchangeable lens 202. Value (F value set by the photographer or automatically). When the aperture control is finished, the image sensor 212 is caused to perform an image capturing operation in step S390, and image data is read from the image capture pixel 310 and all focus detection pixels 313 and 314 of the image capture element 212.

  In step S400, predetermined processing is performed on the image data (for example, pixel data at each pixel position in the focus detection pixel row is interpolated based on data of imaging pixels around the focus detection pixel), and then the image data is stored in the memory. It memorize | stores in the card | curd 219, returns to step S320, and repeats the operation | movement mentioned above.

  In the continuous AF mode, focus adjustment is performed by always performing focus detection by dedicated AF while the main mirror 205 and the sub mirror 217 are inserted in the photographing optical path. Therefore, even when the subject moves at high speed and the defocus amount changes greatly, or when the composition is frequently changed by the photographer and the defocus amount changes greatly, the defocus amount suddenly changes without fail. Thus, the photographer can continue to capture the subject image with the optical viewfinder until the shutter is released.

  When branching to the high-precision AF mode, the operation starts from step S500 in FIG. If the sub mirror 217 has been inserted into the photographing optical path in step S510, the sub mirror 217 is retracted out of the photographing optical path. If the main mirror 205 has been retracted outside the imaging optical path in step S520, the main mirror 205 is inserted into the imaging optical path. In step S530, the position of the image sensor 212 is reset, and the image sensor 212 is positioned at the center of the movable range by the image sensor driving means 235.

  In step S540, data is read out from the AF area (AF area selected by the photographer) of the image sensor AF. In step S550, an image shift amount is calculated based on the data read from the AF area of the image sensor AF. In step S560, the image shift amount is converted into a defocus amount.

  In step S570, the defocus amount is transmitted to the lens drive control device 206, and the focusing lens 210 of the interchangeable lens 202 is driven to the in-focus position. In step S580, data is read from the AF area of the image sensor AF (the AF area selected by the photographer). In step S590, an image shift amount is calculated based on the data read from the AF area of the image sensor AF. Details of steps S540, S550, S590, and S600 will be described later.

  In step S610, it is determined whether the calculated defocus amount is within the movable range of the image sensor 212. If the defocus amount is not within the movable range, the process returns to step S570 and the above-described operation is repeated. If it is within the movable range, in step S620, the image sensor 212 is moved in the optical axis direction according to the defocus amount.

  In step S630, the photographer moves the external operation means 221 to the second stage operation state, and determines whether the shutter release is instructed. If there is no shutter release instruction, the process returns to step S540 or step S580 to perform the above-described operation. repeat.

  If there is an instruction for shutter release, in step S640, the main mirror 205 is retracted from the imaging optical path, and an aperture adjustment command is transmitted to the lens drive control unit 206, and the aperture value of the interchangeable lens 202 is controlled to an F value (imaging). Or F value set automatically or automatically). When the aperture control is completed, in step S650, the image sensor 212 is caused to perform an imaging operation, and image data is read from the image pickup pixel 310 and all the focus detection pixels 313 and 314 of the image pickup element 212.

  In step S660, predetermined processing is performed on the image data (for example, pixel data at each pixel position in the focus detection pixel row is interpolated based on data of imaging pixels around the focus detection pixel), and then the image data is stored in the memory. The data is stored in the card 219, and the process returns to step 520 to repeat the above-described operation.

  In the high-precision AF mode, the main mirror 205 is inserted into the imaging optical path, and the focus detection is performed by the imaging element AF with the sub mirror 217 retracted from the imaging optical path, and the detected defocus amount is outside the movable range of the imaging element 212. In this case, after the focusing lens 210 is moved and the first-stage focus adjustment (coarse adjustment) is performed, when the detected defocus amount is within the movable range of the image sensor 212, the image sensor 212. The second stage of focus adjustment (fine adjustment) is performed by moving. Therefore, even when the subject moves slightly in the optical axis direction, or when the relative position of the subject and the camera changes slightly due to handheld shooting, it is possible to always achieve a quick and highly accurate in-focus state. The photographer can continue to capture the subject image with the optical viewfinder until the shutter is released.

  When branched to the high-speed continuous shooting AF mode, the operation starts from step S700 of FIG. If the main mirror 205 and the sub mirror 217 are inserted in the photographing optical path in step S710, the main mirror 205 and the sub mirror 217 are retracted outside the photographing optical path, and the state shown in FIG. In step S720, the position of the image sensor 212 is reset, and the image sensor 212 is positioned at the center of the movable range by the image sensor driving means 235.

  In step S730, the imaging device 212 performs an imaging operation while fixing the aperture value of the interchangeable lens 202, and image data is read from the imaging pixel 310 and all the focus detection pixels 313 and 314 of the imaging device 212. In step S740, an image based on the image data is displayed on the liquid crystal display element 215.

  In step S750, the photographer determines whether the external operation means 221 is in the second stage operation state and the shutter release is instructed. If there is no shutter release instruction, the process proceeds to step 770.

  If there is an instruction for shutter release, in step S760, predetermined processing is performed on the image data (for example, pixel data at each pixel position in the focus detection pixel row is interpolated based on data of imaging pixels around the focus detection pixel). Then, the image data is stored in the memory card 219, and the process proceeds to step S770.

  In step S770, an image shift amount is calculated based on the focus detection pixel data corresponding to the selected AF area among the focus detection pixel data read out together with the image data at the time of imaging. In step S780, the image shift amount is converted into a defocus amount. Details of steps S770 and S780 will be described later.

  In step S790, it is determined whether the calculated defocus amount is within the movable range of the image sensor 212. If the defocus amount is within the movable range, the image sensor 212 is moved in the optical axis direction according to the defocus amount in step S800. Returning to step S730, the above-described operation is repeated. If it is not within the movable range, the defocus amount is transmitted to the lens drive controller 206 in step S800, the focusing lens 210 of the interchangeable lens 202 is driven to the in-focus position, and the process returns to step S730 to repeat the above-described operation. .

  In the high-speed continuous shooting AF mode, focus detection is performed based on focus detection pixel data read simultaneously with the imaging operation with the main mirror 205 and the sub-mirror 217 retracted from the imaging optical path, and always and quickly according to the detected defocus amount. Perform high-precision focus adjustment. Accordingly, it is possible to shorten the time for reading data dedicated to focus detection, and to shorten the time for inserting and retracting the main mirror 205 and the sub mirror 217 into the photographing optical path. Can be continuously captured by the liquid crystal display element 215.

  For the sake of simplicity, although not shown in the flowcharts of FIGS. 14, 17, 18, and 19, when the defocus amount cannot be calculated (that is, the focus cannot be detected), lens driving is performed. A command is transmitted to the control device 206, and focus detection is performed while the focusing lens 210 is driven to scan between the closest distance and infinity (∞).

  Image shift detection calculation processing (correlation calculation processing, step S140, S150, S200, S210 in FIG. 14, steps S340, S350 in FIG. 17, steps S540, S550, S590, S600 in FIG. 18, steps S770, S780 in FIG. Details of the phase difference detection process will be described below. In the following description, the output signal (data string) of the dedicated AF and the output signal (data string) of the image sensor AF are handled without distinction.

  The data string is composed of a reference data string corresponding to one of the pair of images and a sub data string corresponding to the other. For example, in the case of dedicated AF, data corresponding to an image formed on the image sensor 116 by the re-imaging lens 114 in FIG. 11 forms a reference data string, and is formed on the image sensor 126 by the re-image lens 125. Data corresponding to the formed image constitutes a sub data string. In the case of the image sensor AF, the output of the array of focus detection pixels 313 is a reference data string, and the output of the array of focus detection pixels 314 is a sub data string.

The reference data string (A1 _n , where n = 0 to N) is fixed, and the sub data string (A2 _n , where n = (− m) to (N + m)) is relatively data with respect to the reference data string The data is sequentially shifted by the data interval (data pitch) of the column, and the correlation amount at each shift is calculated by Equation 1.
C (k) = Σ | A1 _n −A2 _{(n + k)} | (1)
However, in the Σ operation, n is integrated from 0 to N. Further, the shift amount k is an integer, and the calculation of Expression (1) is performed in the range of k = (− m) to (+ m). As shown in FIG. 21A, the calculation result of Expression (1) shows that the correlation amount C (k) is minimal in the shift amount where the correlation between the pair of data is high (k = kj = 2 in FIG. 21A). (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 by using the three-point interpolation method according to the following 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 Expression (2) is reliable is determined as follows. As shown in FIG. 13B, when the degree of correlation between the pair of data is low, the value of the minimal value C (x) of the interpolated correlation amount is 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. 13C, 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 k _{min to} k _max , the minimum value C (x) is obtained. In such a case, it is determined that the focus cannot be detected.

When it is determined that the calculated shift amount x is reliable, the image shift amount shft is converted by the equation (6).
shft = PY · (x−X0) (6)
In Expression (6), PY is the detection pitch (in the case of dedicated AF, the pitch of the image sensor 116 multiplied by the projection magnification when the image sensor 116 is projected onto the planned focal plane by the re-imaging lenses 114 and 115, and the image sensor. In the case of AF, it is the actual pitch between the focus detection pixels 313 or 314, that is, twice the pixel pitch), and X0 is an offset amount. In the case of dedicated AF, X0 is an offset amount determined so that the image shift amount becomes 0 when the focal plane matches the planned focal plane. In the case of the image sensor AF, X0 = −0.5, and this amount is an offset amount for correcting that the focus detection pixel 313 and the focus detection pixel 314 are arranged with a shift of a half detection pitch.

The image shift amount calculated by Expression (6) is multiplied by a predetermined conversion coefficient q to be converted into a defocus amount def.
def = q · shft (7)
The conversion coefficient q is a different value between the dedicated AF and the image sensor AF. In the case of the dedicated AF, in FIG. 12, the distance between the center of gravity of the pair of distance measuring pupils 192 and 193 is converted to a value corresponding to the aperture F value. In the case of the image sensor AF, the value of the conversion coefficient q changes according to the open F value of the interchangeable lens used, and the distance between the centers of gravity of two semicircles obtained by dividing the aperture of the open F value of the interchangeable lens into two equal parts. Is converted to a value corresponding to the aperture F value.

In the case of the image sensor AF, the pair of distance measuring pupils 93 and 94 may be displaced by the aperture opening of the interchangeable lens and the light amount balance of the pair of images may be lost. A correlation calculation expression such as the following expression (8) may be used instead of expression (1).
C (k) = Σ | A1 _n · A2 _{(n + 1 + k)} −A2 _{(n + k)} · A1 _{(n + 1)} |
However, the Σ operation takes the sum in the range of n = 0 to (N−1).
<< Other Embodiments of the Invention >>

  The arrangement of the focus detection areas in the dedicated AF and the image sensor AF is not limited to that shown in FIG. 2, and the focus detection areas can be arranged in other positions and directions.

  In the above-described embodiment, the lens drive control device 206 performs the focus adjustment by driving the focusing lens 210 via the focus lens driving unit 233, but as shown in FIG. 22, the driving unit for the focusing lens 210 is driven. May be used in accordance with the defocus amount by providing two systems for high speed (first driving means 233A) and normal (second driving means 233B).

  FIG. 23 is an operation flowchart of the lens drive control device 206. In step S2000, the lens drive control device 206 waits for reception of a defocus amount from the body drive control device 214. When the defocus amount is received, it is determined in step S2010 whether or not the absolute value of the defocus amount is within a predetermined threshold value. If it is within the predetermined threshold, the second driving means 233B drives and moves the focusing lens 210 (shooting optical system) at a normal speed, and the process returns to step S2000.

  The first driving means 233A and the second driving means 233B are connected to the focusing lens 210 by a motor and a speed reduction mechanism (consisting of gears, helicoids, etc.), respectively. The motor used for the first drive means 233A operates at a higher speed than the motor used for the second drive means 233B, and the reduction ratio of the reduction mechanism used for the first drive means 233A is the second drive means 233B. Therefore, although the focusing lens 210 can be driven by the motor at a higher speed, the stopping accuracy of the focusing lens 210 is lowered.

  The focusing lens 210 may be divided into two focusing lenses, and each lens may be separately driven by the first driving means 233A and the second driving means 233B.

  In the embodiment described above, the body drive control device 214 performs focus adjustment by moving the image sensor 212 in the optical axis direction via the image sensor drive means 235, but as shown in FIG. Two driving means may be provided, one for high accuracy (first driving means 235A) and the other for ultra high accuracy (second driving means 235B), depending on the defocus amount.

  FIG. 25 is an operation flowchart of the body drive control device 214, which replaces the steps S610 to S620 in the high-precision AF mode operation shown in FIG.

  In step S611, it is determined whether the calculated defocus amount is within the movable range of the first image sensor driving unit. If not, the process returns to step S570.

  If it is within the movable range of the first image sensor driving means, the defocus amount calculated in step S612 is within the movable range of the second image sensor driving means (however, the movable range of the second image sensor driving means <the first If the image pickup element 212 is not within the movable range, the image pickup element 212 is moved with high accuracy in the optical axis direction by the first image pickup element drive means according to the defocus amount, Proceed to step S630.

  When the calculated defocus amount is within the movable range of the second image sensor driving unit, the image sensor 212 is moved in the optical axis direction by the second image sensor driving unit with very high accuracy according to the defocus amount, Proceed to step S630.

  In the embodiment described above, it is necessary to insert / withdraw the sub mirror 217 in the photographing optical path when switching between focus detection by the dedicated AF and focus detection by the image sensor AF.

  In the configuration of the imaging apparatus of the embodiment shown in FIG. 26, the sub-mirror 217A is a half mirror, so that focus detection by the dedicated AF and focus detection by the imaging element AF can be performed simultaneously.

  FIG. 27 shows a “parallel AF mode” which is one AF mode of the body drive control device 214 in the embodiment of FIG. 26 (an AF mode in which focus detection is performed simultaneously with focus detection by dedicated AF and focus detection by image sensor AF). Is an operation flowchart in FIG.

  In the parallel AF mode, the operation starts from step S900 in FIG. In step S910, when the main mirror 205 and the sub mirror 217A are retracted from the photographing optical path, the main mirror 205 and the sub mirror 217A are inserted into the photographing optical path. In step S920, the position of the image sensor 212 is reset, and the image sensor 212 is positioned at the center of the movable range by the image sensor driving means 235.

  In step S930, data is read from the dedicated AF and the AF area of the image sensor AF (the AF area selected by the photographer). In step S940, the image shift amounts are calculated based on the data read from the AF areas of the dedicated AF and the image sensor AF. In step S950, the image shift amounts of the dedicated AF and the image sensor AF are converted into defocus amounts.

  In step S960, it is determined whether the calculated defocus amount of the image sensor AF is within the movable range of the image sensor. If not, the defocus amount of the dedicated AF is determined in step S970. , The focusing lens 210 of the interchangeable lens 202 is driven to the in-focus position, and the process returns to step S930 to repeat the above-described processing. If the calculated defocus amount is within the movable range of the image sensor, the image sensor 212 is moved in the optical axis direction according to the defocus amount of the image sensor AF in step S980.

  In step S990, it is determined whether the photographer has put the external operation means 221 in the second stage operation state and the shutter release is instructed. If there is no shutter release instruction, the process returns to step S930 and the above-described operation is repeated. When the shutter release instruction is given, in step S1000, the main mirror 205 and the sub mirror 217A are retracted from the photographing optical path, and an aperture adjustment command is transmitted to the lens drive controller 206 to control the aperture value of the interchangeable lens 202. Value (F value set by the photographer or automatically). When the aperture control is finished, in step S1010, the imaging device 212 performs an imaging operation, and image data is read from the imaging pixel 310 and all the focus detection pixels 313 and 314 of the imaging device 212.

  In step S1020, predetermined processing is performed on the image data (for example, pixel data at each pixel position in the focus detection pixel row is interpolated based on data of imaging pixels around the focus detection pixel), and then the image data is stored in the memory. It memorize | stores in the card | curd 219, returns to step S930, and repeats the operation | movement mentioned above.

  In the parallel AF mode, the focus detection can be performed simultaneously with the dedicated AF and the image sensor AF without inserting / withdrawing the sub mirror 217A into / from the imaging optical path with the main mirror 205 inserted in the imaging optical path. Therefore, even when the defocus state changes drastically due to high-speed movement of the subject or composition change, the focus adjustment operation can be continued quickly, and at the same time, defocusing due to minute movement of the subject, camera shake, etc. Even when the focus state changes slightly, the focus adjustment operation can be continued with high accuracy, and the photographer can continue to capture the subject image with the optical viewfinder until the shutter release is performed. .

  In the above-described embodiments, the image pickup pixels are described as an RGB Bayer array. However, for example, a pixel array other than the Bayer array such as a complementary color filter array may be used.

  Further, in the focus detection pixels 313 and 314 shown in FIG. 5 of the embodiment described above, an example in which the shape of the photoelectric conversion unit is rectangular is shown, but the shape of the photoelectric conversion unit of the focus detection pixel is limited to these. Alternatively, other shapes may be used. For example, the shape of the photoelectric conversion unit of the focus detection pixel can be a semicircle, an ellipse, or a polygon.

  Further, in the focus detection pixels 313 and 314 shown in FIGS. 5 and 9 of the above-described embodiment, a distance measuring pupil is formed by projecting the shape of the photoelectric conversion units 13 and 14 forward by the microlens 10. However, it is also possible to configure the focus detection pixels 313 and 314 as shown in FIGS. 28A and 28B, light shielding masks 33 and 34 are provided immediately before the photoelectric conversion unit 30, and the shapes of the openings 43 and 44 provided in the light shielding masks 33 and 34 are projected forward by the microlens 10. Thus, a pair of distance measuring pupils are formed on the exit pupil. In this case, the photoelectric conversion unit 33 receives the light flux that has passed through the openings 43 and 44.

  In the imaging device 212 illustrated in FIG. 3, the focus detection pixels 313 and 314 are provided with one photoelectric conversion unit in one pixel, but a pair of photoelectric conversion units is provided in one pixel. Also good. FIG. 29 is an enlarged view of a part of the image sensor 212A corresponding to the image sensor 212 of FIG. 3, and the focus detection pixel 311 includes a pair of photoelectric conversion units in one pixel. The focus detection pixel 311 shown in the drawing performs a function corresponding to the pair of the focus detection pixel 313 and the focus detection pixel 314 shown in FIG.

  The focus detection pixel 311 includes a microlens 10 and a pair of photoelectric conversion units 13 and 14 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 its spectral characteristic is a spectral that combines the spectral sensitivity of a photodiode that performs photoelectric conversion and the spectral characteristic of an infrared cut filter (not shown). Characteristics (see FIG. 7). That is, the spectral characteristics are 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 includes the light wavelength regions of the sensitivity of the green pixel, the red pixel, and the blue pixel. ing.

  FIG. 31 is a diagram for explaining the focus detection operation of the pupil division type phase difference detection method by the focus detection pixels of the image sensor 212A shown in FIG. In FIG. 31, the exit pupil 90 is set at a position of a distance d ahead of the microlens arranged on the planned imaging plane of the interchangeable lens. Here, the distance d is a distance measurement pupil distance determined according to the curvature, refractive index, distance between the microlens and the photoelectric conversion unit, and the like. Reference numeral 91 is an optical axis of the interchangeable lens, reference numerals 50 and 60 are microlenses, reference numerals 53, 54, 63, and 64 are photoelectric conversion units of focus detection pixels, and reference numerals 73, 74, 83, and 84 are focus detection light beams. The photoelectric conversion units are paired (53, 54) and (63, 64) in each focus detection pixel.

  Reference numeral 93 denotes an area of the photoelectric conversion units 53 and 63 projected by the microlenses 50 and 60, which is a distance measuring pupil. Similarly, reference numeral 94 denotes an area of the photoelectric conversion units 54 and 64 projected by the microlenses 50 and 60, which is a distance measuring pupil. In FIG. 31, a focus detection pixel (consisting of a microlens 50 and a pair of photoelectric conversion units 53 and 54) on the optical axis 91 and an adjacent focus detection pixel (a microlens 60 and a pair of photoelectric conversion units 63 and 64). Schematically). Also in the focus detection pixels arranged in the periphery on the imaging surface, the pair of photoelectric conversion units receives the light flux that arrives at each microlens through the pair of distance measuring pupils 93 and 94, 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 photographing optical system, and are paired behind (to the right in FIG. 31) by the microlens 50 disposed on the optical axis 91. The shapes of the photoelectric conversion units 53 and 54 are projected onto the exit pupil 90 separated from the microlenses 50 and 60 by the distance measurement pupil distance d, and the projection shapes form the distance measurement pupils 93 and 94. In addition, the microlens 60 disposed adjacent to the microlens 50 causes the pair of photoelectric conversion units 63 and 64 disposed behind (to the right in FIG. 31) to be separated by the distance measurement pupil distance d. The projected image is projected onto the exit pupil 90, and the projection shape forms distance measuring pupils 93 and 94. That is, the microlens of each pixel and the photoelectric conversion so that the projection shape (ranging pupils 93 and 94) of the photoelectric conversion unit of each focus detection pixel matches on the exit pupil 90 at the distance pupil distance d from the microlens. The positional relationship of the parts has been determined.

  The photoelectric conversion unit 53 outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light flux 73 that passes through the distance measuring pupil 93 and arrives at the microlens 50. Further, the photoelectric conversion unit 54 outputs a signal corresponding to the intensity of the image formed on the microlens 50 by the focus detection light beam 74 that passes through the distance measuring pupil 94 and arrives at the microlens 50. Similarly, 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 that passes through the distance measuring pupil 93 and arrives at the microlens 60. The photoelectric conversion unit 64 outputs a signal corresponding to the intensity of the image formed on the microlens 60 by the focus detection light beam 84 that passes through the distance measuring pupil 94 and arrives at 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 93 and the distance measurement pupil 94, whereby the distance measurement pupil 93 and Information on the intensity distribution of the pair of images formed on the focus detection pixel array by the focus detection light fluxes that pass through the distance measuring pupils 94 is obtained. By applying the above-described image shift detection calculation process (correlation calculation process, phase difference detection process) to this information, the image shift amount of a pair of images is detected by a so-called pupil division type phase difference detection method. Further, by applying a predetermined conversion process to the image shift amount, the current image plane (image plane corresponding to the focus detection position on the photographing screen) relative to the planned image plane (corresponding to the position of the microlens array) is changed. A deviation (defocus amount) is calculated.

  Furthermore, in the imaging device 212 shown in FIG. 3, the example in which the imaging pixels and the focus detection pixels are arranged in a dense square lattice arrangement is shown, but a dense hexagonal lattice arrangement may be used.

  In the above-described embodiment, the focus detection operation by the pupil division type phase difference detection method using the microlens as the image sensor AF has been described. However, the present invention is not limited to this, and Japanese Unexamined Patent Application Publication No. 2008-15157. It is also possible to apply to the imaging device of the pupil division type phase difference detection method using the polarizing element disclosed in the above.

  In FIG. 1 described above, two focus adjustment mechanisms (moving the focusing lens / moving the image sensor) are used, but only one of them may be used.

  In the above-described embodiment, the pupil division type phase difference detection method is used for focus adjustment by the image sensor, but a contrast method (mountain climbing method) may be used. However, it is preferable to use the pupil division type phase difference detection method because the focus detection time and the focus adjustment time are shorter than the contrast method.

  In the embodiment described above, an optical viewfinder is used as the observation optical system, but an electronic viewfinder may be used.

  Note that the imaging apparatus is not limited to a digital still camera having a configuration in which an interchangeable lens is attached to the camera body as described above. For example, the present invention can be applied to a lens-integrated digital still camera or video camera. Furthermore, the present invention can also be applied to surveillance cameras, robot vision recognition devices, in-vehicle cameras, and the like.

1 is a cross-sectional view illustrating a configuration of a digital still camera as an embodiment of an imaging apparatus according to the present invention. The figure which shows the focus detection position on the imaging | photography screen of an interchangeable lens. The front view which shows the detailed structure of an image pick-up element. The figure which shows the structure of an imaging pixel. The figure which shows the structure of a focus detection pixel. The figure which shows the spectral characteristic of a green pixel, a red pixel, and a blue pixel. The figure which shows the spectral characteristic of a focus detection pixel. Sectional drawing of an imaging pixel. Sectional drawing of a focus detection pixel. The figure which shows the structure of the focus detection optical system of the pupil division type phase difference detection system using a micro lens. The figure which shows the structure of the focus detection sensor of a re-imaging pupil division type phase difference detection system. The figure which compared the ranging pupil of image pick-up element AF on the exit pupil, and the ranging pupil of exclusive AF. 3 is a flowchart showing an imaging operation of a digital still camera as an embodiment of an imaging apparatus according to the present invention. 6 is a flowchart showing an imaging operation of a digital still camera in a one-shot AF mode. The figure which shows the structure of the digital still camera which retracted | removed only the submirror from the imaging | photography optical path. The figure which showed typically the movable range of the lens for focusing, and the movable range of an image pick-up element. 6 is a flowchart illustrating an imaging operation of a digital still camera in a continuous AF mode. 6 is a flowchart showing an imaging operation of a digital still camera in a high-precision AF mode. 6 is a flowchart illustrating an imaging operation of a digital still camera in a high-speed continuous shooting AF mode. The figure which shows the structure of the digital still camera which retracted the main mirror and the submirror out of the imaging | photography optical path. The figure which shows the relationship of the correlation amount C (k) with respect to the shift amount k of a pair of data. The figure which shows the structure of the digital still camera which provided the drive means of the lens for focusing for high-speed and two systems for normal. The operation | movement flowchart of a lens drive control apparatus. The figure which shows the structure of the digital still camera which provided the drive means of the image pick-up element for two systems for high precision and for super high precision. The operation | movement flowchart of a body drive control apparatus. The figure which shows the structure of the digital still camera which replaced the submirror with the half mirror. 6 is a flowchart showing an imaging operation of a digital still camera in a parallel AF mode. Sectional drawing of the focus detection pixel which provided the light shielding mask. The enlarged view of a part of imaging device. The figure which shows the structure of the focus detection pixel comprised from a microlens and a pair of photoelectric conversion part. The figure for demonstrating the focus detection operation | movement of the pupil division type phase difference detection system by the focus detection pixel of an image sensor.

Explanation of symbols

201 Digital Still Camera, 202 Interchangeable Lens, 203 Camera Body, 204 Mount Unit, 205 Main Mirror, 206 Lens Drive Control Device, 207 Focus Detection Sensor, 208 Zooming Lens, 209 Lens, 210 Focusing Lens, 211 Aperture, 212 Imaging Element, 213 Electrical contact, 214 Body drive control device, 215 Liquid crystal display element, 216 Optical viewfinder, 217 Sub mirror, 219 Memory card, 220 and 221 External operation means, 231 Aperture drive means, 232 Zoom drive means, 233 Focus lens drive means 234 Mirror drive means, 235 Image sensor drive means

Claims (14)

An imaging device in which an imaging pixel that outputs a signal for generating image data corresponding to an image formed by the imaging optical system and a focus detection pixel that outputs a signal for detecting the focus state of the image are arranged When,
A first light beam that is disposed in the imaging optical path between the imaging optical system and the imaging element and branches the light beam coming from the imaging optical system along the imaging optical path and the outside of the imaging optical path. A beam splitter that separates into two light beams;
An observation optical system for observing an image formed by the second light flux;
A deflecting mirror that is arranged so as to be able to be inserted into the photographing optical path and retracted out of the photographing optical path, and deflects the first light beam out of the photographing optical path when inserted into the photographing optical path;
First focus detection means for receiving the first light beam deflected out of the photographing optical path by the deflection mirror and detecting a focus state of an image formed by the first light beam by a pupil division type phase difference detection method; ,
Second focus detection means for detecting a focus state of an image formed by the first light flux coming along the photographing optical path based on a signal output from the focus detection pixel;
An imaging apparatus comprising: control means for individually controlling detection of a focus state by the first focus detection means and the second focus detection means in accordance with an arrangement state of the deflection mirror. The imaging device according to claim 1,
The control means performs the detection of the focus state by the first focus detection means in a state where the deflection mirror is inserted in the photographing optical path, and then the state in which the deflection mirror is retracted out of the photographing optical path. In the imaging apparatus, the first focus detection unit and the second focus detection unit are controlled so that the focus state is detected by the second focus detection unit. The imaging device according to claim 1,
The image pickup apparatus according to claim 1, wherein the control unit performs control so that only the focus state is detected by the first focus detection unit in a state where the deflection mirror is always inserted in the photographing optical path. The imaging device according to claim 1,
The image pickup apparatus according to claim 1, wherein the control unit performs control so that only the focus state is detected by the second focus detection unit in a state where the deflecting mirror is always retracted out of the imaging optical path. The imaging device according to claim 1,
The beam splitter is arranged so that it can be inserted into the imaging optical path and retracted out of the imaging optical path,
The control unit individually controls the detection of the focus state by the first focus detection unit and the second focus detection unit according to the arrangement state of the beam splitter and the deflection mirror, and the beam splitter and the deflection An image pickup apparatus, wherein control is performed such that only the detection of the focus state by the second focus detection means is performed in a state in which the mirror is always retracted from the photographing optical path. The imaging device according to claim 1,
The focus detection pixel includes a photoelectric conversion unit, and a microlens provided corresponding to the photoelectric conversion unit,
The photoelectric conversion unit is configured to receive a pair of light beams that pass through a pair of pupil regions of the imaging optical system,
The second focus detection unit detects the focus state by calculating an image shift amount of a pair of images formed by the pair of light beams based on an output signal from the focus detection pixel. Imaging device. The imaging device according to claim 1,
Focus adjusting means for performing focus adjustment so that an image formed on the image sensor is in focus based on the detection result of the focus state by the first focus detecting means and the second focus detecting means. An imaging apparatus comprising: The imaging apparatus according to claim 7,
The focus adjusting means includes a first focus adjusting means and a second focus adjusting means,
The image pickup apparatus, wherein the second focus adjustment unit performs fine adjustment of the focus adjustment as compared with the first focus adjustment unit. The imaging device according to claim 8,
The first focus adjustment unit performs the focus adjustment by moving the imaging optical system, and the second focus adjustment unit performs the focus adjustment by moving the imaging element. . The imaging device according to claim 8,
The imaging apparatus according to claim 1, wherein the first focus adjustment unit and the second focus adjustment unit perform the focus adjustment by moving the imaging optical system. The imaging device according to claim 8,
The image pickup apparatus, wherein the first focus adjustment unit and the second focus adjustment unit perform the focus adjustment by moving the imaging element. In the imaging device according to claim 8-11,
The first focus adjustment unit performs the focus adjustment according to the detection result of the focus state by the first focus detection unit,
The imaging apparatus according to claim 2, wherein the second focus adjustment unit performs the focus adjustment according to a detection result of the focus state by the second focus detection unit. An imaging device in which an imaging pixel that outputs a signal for generating image data corresponding to an image formed by the imaging optical system and a focus detection pixel that outputs a signal for detecting the focus state of the image are arranged When,
A first light beam that is disposed in the imaging optical path between the imaging optical system and the imaging element and branches the light beam coming from the imaging optical system along the imaging optical path and the outside of the imaging optical path. A beam splitter that separates into two light beams;
An observation optical system for observing an image formed by the second light flux;
A deflecting mirror for deflecting the first light flux out of the photographing optical path;
First focus detection means for receiving the first light beam deflected by the deflection mirror and detecting a focus state of an image formed by the first light beam by a pupil division type phase difference detection method;
Second focus detection means for detecting a focus state of an image formed by the first light flux coming along the photographing optical path based on a signal output from the focus detection pixel;
Beam splitter driving means for inserting the beam splitter into the imaging optical path and retracting the beam splitter out of the imaging optical path;
Deflection mirror driving means for inserting the deflection mirror into the imaging optical path and retracting the imaging mirror from the imaging optical path;
With the beam splitter inserted into the imaging optical path, the beam splitter driving means and the deflection mirror driving means are inserted into the imaging optical path and retracted out of the imaging optical path. And control means for individually controlling the focus state detection by the first focus detection means and the second focus detection means in accordance with the arrangement state of the beam splitter and the deflection mirror. An imaging device. The imaging apparatus according to claim 13, wherein the observation optical system includes at least one of an optical viewfinder and an electronic viewfinder.

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