JP2018151508A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device with which it is possible to detect each eccentricity amount of an optimum lens eccentricity mechanism and automatically and easily execute a function that requires the eccentricity amount of the lens eccentricity mechanism even when each eccentricity amount cannot be automatically detected in an interchangeable lens having a lens eccentricity function.SOLUTION: The imaging device is configured by including: an imaging optical system 10 in which at least some lens unit can be made eccentric to the optical axis; an imaging element 24 in which an imaging pixel is arrayed in plurality so that a beam of light incident from the imaging optical system 10 is pupil-divided into a plurality of regions; image signal generation means 44 for generating a pair of image signals from output values outputted from the imaging element 24 by photoelectric conversion; and eccentricity amount calculation means 45 for calculating the eccentricity amount of at least some eccentric lens unit of the imaging optical system 10 from the pair of image signals generated by the image signal generation means 44.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus having an imaging plane phase difference AF function.

  Conventionally, imaging plane phase difference AF is known as a method for detecting a focus state using an imaging element. The imaging plane phase difference AF is obtained by receiving a divided light beam obtained by dividing a light beam that has passed through the exit pupil of the imaging optical system by a plurality of focus detection pixels, and a deviation amount of a signal output according to the received light amount. Based on this, the driving amount of the focus lens required for focusing is obtained. According to the imaging plane phase difference AF, a high-speed and smooth focus adjustment operation is possible.

  Patent Document 1 discloses an imaging apparatus including a two-dimensional imaging element in which a photoelectric conversion unit divided into a plurality of microlenses is formed. The divided photoelectric conversion units are configured to receive different pupil partial areas of the exit pupil of the imaging optical system via one microlens, and perform pupil division. When the focus state of the imaging optical system is detected (focus detection is performed), the phase difference between the pair of image signals generated by the pupil-divided pixels is obtained, and the focus state is obtained from the phase difference.

  Conventionally, an interchangeable lens having a lens decentering function (shift mechanism, tilt mechanism, revolving mechanism) and a camera having a photographing function using the interchangeable lens are known. Patent Document 2 discloses an adjustment function that detects the tilt angle of a lens and automatically adjusts the optimum tilt eccentricity. In Patent Document 3, when a lens unit having a lens decentering function cannot detect the decentering amount of each mechanism, each decentering amount is set in the camera by manual input, and an optimum electronic front curtain scan is performed to perform uneven exposure. Can be corrected.

U.S. Pat. Japanese Patent No. 5176912 JP 2013-156600 A

  However, some interchangeable lenses having a lens decentering function cannot detect the decentering amount of each mechanism. In Patent Document 2, the camera tilt angle can be detected by an acceleration sensor provided on the camera side, but each eccentric amount of the imaging optical system cannot be detected. Further, in Patent Document 3, since the user inputs each decentering amount of the imaging optical system to the interchangeable lens that cannot detect the decentering amount of each mechanism, the operation is troublesome.

In order to achieve the above object, the present invention provides:
An imaging optical system (10) capable of decentering at least a part of the lens unit with respect to the optical axis;
An imaging device (24) in which a plurality of imaging pixels are arranged so as to divide the light beam incident from the imaging optical system (10) into a plurality of regions;
Image signal generation means (44) for generating a pair of image signals from output values output by the image sensor (24) photoelectric conversion;
Eccentricity amount calculating means (45) for calculating the eccentricity amount of at least a part of the decentered lens unit of the imaging optical system (10) from the pair of image signals generated by the image signal generating means (44). )When,
It is characterized by having.

  According to the present invention, in an interchangeable lens having a lens decentering function, even when each decentering amount cannot be automatically detected, each decentering amount of the lens decentering mechanism is detected and the decentering amount of the lens decentering mechanism is detected. It is possible to automatically and easily execute a function that requires.

1 is a schematic configuration diagram of an imaging apparatus according to Embodiment 1 of the present invention. Schematic of pixel arrangement in Embodiment 1 of the present invention Schematic plan view and schematic cross-sectional view of a pixel in Embodiment 1 of the present invention Schematic explanatory diagram of pixel and pupil division in Embodiment 1 of the present invention Schematic explanatory diagram of an image sensor and pupil division in Embodiment 1 of the present invention Schematic relationship diagram of defocus amount and image shift amount of first focus detection signal and second focus detection signal in Embodiment 1 of the present invention Graph of shading at the time of eccentricity (shift) of the first focus detection signal and the second focus detection signal in Embodiment 1 of the present invention Graph of shading at the time of eccentricity (tilt) of the first focus detection signal and the second focus detection signal in Embodiment 1 of the present invention Graph of shading signal ratio when eccentricity of first focus detection signal and second focus detection signal in Embodiment 1 of the present invention The figure showing the relationship of the signal ratio of the 1st focus detection signal of a right-and-left end pixel in Example 1 of this invention, and a 2nd focus detection signal, and a signal ratio difference. Operation flowchart of electronic front curtain photography in which correction is performed using the calculated lens eccentricity in Embodiment 1 of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Example 1]
[overall structure]
FIG. 1 shows a schematic configuration diagram of an imaging apparatus according to the present invention. FIG. 1 shows a configuration of a camera system including a digital single-lens reflex camera 2 that is Embodiment 1 of the present invention and an interchangeable lens 1 that can be interchanged with the camera 2.

An imaging optical system 10 is accommodated in the interchangeable lens 1. The imaging optical system 10 includes a plurality of lenses and a diaphragm. In addition, the interchangeable lens 1 can decenter at least one or more lenses with respect to the optical axis, and shifts the eccentric lens in a predetermined direction perpendicular to the optical axis of the interchangeable lens 1. The mechanism 16, the tilt mechanism 17 for decentering in a predetermined direction on an arc with respect to the optical axis of the interchangeable lens 1, and the revolving mechanism 18 capable of changing the eccentric direction of the tilt mechanism by rotating the tilt mechanism 17. have. The lens storage unit 14 is configured by a ROM or the like, and stores various types of information such as identification information of the interchangeable lens 1 and optical information of the imaging optical system 10. The electrical contact 15 enables communication between the interchangeable lens 1 and the digital single lens reflex camera 2, and information such as information stored in the lens storage unit 14 and focus lens position information output from the lens driving unit 11 described later. Can be transferred to the camera control unit 40. The focus lens 10a is movable in the optical axis direction and can be focused by moving in the optical axis direction.

  The lens driving unit 11 controls and drives the focus lens 10a movable in the optical axis direction by a lens control unit 13 described later. Further, it is possible to detect the position of the focus lens 10a and transfer the focus lens position information to the camera control unit 40 via the lens control unit 13 and the electrical contact 15 described above.

  In the camera 2, the main mirror 20 composed of a half mirror is disposed at a down position in the photographing optical path as shown in the drawing when the user observes the subject through the optical viewfinder, and the light from the imaging optical system 10 is displayed. Is reflected toward the focus plate 30. In addition, the main mirror 20 rotates to the up position for retreating from the photographing optical path during live view observation in which a live view image is displayed on the rear monitor 43 or during photographing for generating recording images (still images and moving images). Thereby, the light from the imaging optical system 10 goes to the shutter 23 and the imaging element 24.

  The sub mirror 21 rotates together with the main mirror 20 and guides the light transmitted through the main mirror 20 disposed at the down position to the AF sensor unit 22. When the main mirror 20 is rotated to the up position, the sub mirror 21 is also retracted from the photographing optical path.

  The AF sensor unit 22 uses a phase difference detection method in a plurality of focus detection areas provided in a shooting range by the camera 2 using light incident from the subject through the imaging optical system 10 and reflected by the sub mirror 21. The focus state of the imaging optical system is detected (focus detection). The AF sensor unit 22 is an area in which a secondary imaging lens that forms a pair of images (subject images) on the light from each focus detection region and a pair of light receiving element arrays that photoelectrically convert the pair of subject images. Sensor (CCD or CMOS). The pair of light receiving element rows of the area sensor outputs a pair of image signals, which are photoelectric conversion signals corresponding to the luminance distribution of the pair of subject images, to the camera control unit 40. A plurality of pairs of light receiving element arrays corresponding to a plurality of focus detection areas are two-dimensionally arranged on the area sensor.

  The camera control unit 40 calculates the phase difference between the pair of image signals, and calculates the focus state (defocus amount) of the imaging optical system 10 from the phase difference. Furthermore, the camera control unit 40 calculates a focus position, which is a position where the focus lens 10a should be moved, in order to obtain a focus state of the image pickup optical system 10 based on the detected focus state of the image pickup optical system 10. Then, the camera control unit 40 transmits a focus command to the lens control unit 13 so as to move the focus lens 10a to the in-focus position calculated by the phase difference AF. The lens control unit 13 moves the focus lens 10a to the in-focus position via the lens driving unit 11 in accordance with the received focus command. Thereby, the focused state of the imaging optical system 10 is obtained.

  The shutter 23 is closed during optical viewfinder observation, and is opened during live view observation and moving image shooting, and photoelectric conversion (generation of a live view image and a captured moving image) by the image sensor 24 of a subject image formed by the imaging optical system 10 is possible. And Further, during still image shooting, the shutter is opened and closed at a set shutter speed, and exposure of the image sensor 24 is controlled.

  The image sensor 24 is composed of a CMOS image sensor or a CCD image sensor and its peripheral circuits, and photoelectrically converts a subject image formed by the imaging optical system 10 and outputs an analog imaging signal. In each pixel portion of the image sensor 24, a plurality of sub-pixels for pupil division that serve both as an image sensor and a focus detection element are arranged. This will be described in detail later. The image sensor 24 can measure the luminance of the subject image formed by the imaging optical system 10.

  The focus plate 30 is disposed on the primary imaging plane of the imaging optical system 10 that is equivalent to the imaging element 24. A subject image (finder image) is formed on the focus plate 30 during optical viewfinder observation. The pentaprism 31 converts the subject image formed on the focus plate 30 into an erect image. The eyepiece 32 allows the user to observe an erect image. The focus plate 30, the pentaprism 31 and the eyepiece lens 32 constitute an optical finder.

  The AE sensor 33 receives light from the focus plate 30 via the pentaprism 31 and measures the luminance of the subject image formed on the focus plate 30. The AE sensor 33 has a plurality of photodiodes, and can measure the luminance in each of a plurality of photometric areas set so as to divide the imaging range of the camera 2. In addition to measuring the brightness of the subject image, it also has a subject detection function for determining the state of the subject by measuring the shape and color of the subject image.

The camera control unit 40 is configured by a microcomputer including an MPU and the like, and controls the operation of the entire camera system including the camera 2 and the interchangeable lens 1.
The digital processing means 41 converts the analog image signal from the image sensor 24 into a digital image signal, and further performs various processes on the digital image signal to generate an image signal (image data). The imaging device 24 and the digital processing means 41 constitute an imaging system.

  The digital processing means 41 detects the focus state by the phase difference detection method using a plurality of pupil-dividing subpixels arranged in the image sensor 24. Further, the digital processing means 41 calculates a focus position, which is a position where the focus lens 10a should be moved, in order to obtain a focus state of the imaging optical system 10 based on the detected focus state of the imaging optical system 10. Is referred to as imaging plane phase difference AF. Further, the digital processing means 41 has an image signal generation means 44 and an eccentricity amount calculation means 45, and the image signal generation means 44 outputs outputs from a plurality of sub-pixels arranged in the image sensor 24 described later. Based on this, a first focus detection signal and a second focus detection signal are generated. Further, the decentering amount calculating unit 45 can detect the lens decentering amount of the imaging optical system from the first focus detection signal and the second focus detection signal generated by the image signal generating unit 44.

  The camera storage unit 42 stores various data used in the operation of the camera control unit 40 and the digital processing means 41. In addition, the camera storage unit 42 stores the generated recording image.

  The rear monitor 43 includes a display element such as a liquid crystal panel, and displays a live view image, a recording image, and various types of information.

[Image sensor]
FIG. 2 shows a schematic diagram of the arrangement of the image sensor 24 of the first embodiment. FIG. 2 shows the pixel (imaging pixel) array of the two-dimensional CMOS sensor (imaging device) of this embodiment in a range of 4 columns × 4 rows and the sub-pixel array in a range of 8 columns × 8 rows. .

  In the first embodiment, the pixel group 200 of 2 columns × 2 rows shown in FIG. 2 includes a pixel 200R having an R (red) spectral sensitivity on the upper left and a pixel 200G having a G (green) spectral sensitivity on the upper right. A pixel 200B having a spectral sensitivity of B (blue) is arranged at the lower left. Further, each pixel includes subpixels 201 to 204 arranged in 2 columns × 2 rows.

A large number of 4 columns × 4 rows of pixels (8 columns × 8 rows of sub-pixels) shown in FIG. 2 are arranged on the surface, and a captured image (sub-pixel signal) can be acquired. In this embodiment, the pixel period P is 4 μm, the number of pixels N is 5575 columns × 3725 rows = approximately 20.75 million pixels, the subpixel cycle P _SUB is 2 μm, and the number of subpixels N _SUB is 11150 columns × 7450 columns. The description will be made assuming that the image sensor having a row = about 83 million subpixels.

  FIG. 3A shows a plan view of one pixel 200G of the image pickup device shown in FIG. 2 viewed from the light receiving surface side (+ Z side) of the image pickup device, and a cross section taken along the line aa in FIG. A cross-sectional view viewed from the Y side is shown in FIG.

As shown in FIG. 3, in the pixel 200G of the present embodiment, a microlens 305 for condensing incident light is formed on the light receiving side of each pixel, and is divided into _NH (two divisions) in the X direction and in the Y direction. the photoelectric conversion unit 304 is formed from N _V division (2 divided) photoelectric conversion unit 301. Photoelectric converters 301 to 304 correspond to subpixels 201 to 204, respectively.

  The photoelectric conversion unit 301 to the photoelectric conversion unit 304 may be a pin structure photodiode in which an intrinsic layer is sandwiched between a p-type layer and an n-type layer, or an intrinsic layer is omitted as necessary, and a pn junction is provided. A photodiode may be used.

In each pixel, a color filter 306 is formed between the microlens 305 and the photoelectric conversion unit 301 to the photoelectric conversion unit 304. Further, if necessary, the spectral transmittance of the color filter may be changed for each sub-pixel, or the color filter may be omitted.
The light that has entered the pixel 200 </ b> G illustrated in FIG. 3 is collected by the microlens 305, dispersed by the color filter 306, and then received by the photoelectric conversion unit 304 from the photoelectric conversion unit 301.

  In the photoelectric conversion unit 301 to the photoelectric conversion unit 304, a pair of electrons and holes are generated according to the amount of received light and separated by a depletion layer, and then negatively charged electrons are accumulated in an n-type layer (not shown), The holes are discharged to the outside of the image sensor through a p-type layer connected to a constant voltage source (not shown).

  Electrons accumulated in the n-type layer (not shown) of the photoelectric conversion unit 301 from the photoelectric conversion unit 301 are transferred to the electrostatic capacitance unit (FD) via the transfer gate and converted into a voltage signal.

  FIG. 4 is a schematic explanatory diagram showing the correspondence between the pixel structure of this embodiment shown in FIG. 3 and pupil division. FIG. 4A shows a cross-sectional view of the pixel structure of the present embodiment shown in FIG. 3A as seen from the + Y side and an exit pupil plane of the imaging optical system. In FIG. 4A, the X axis and Y axis of the cross-sectional view are reversed with respect to FIG. 3 in order to correspond to the coordinate axis of the exit pupil plane.

  In FIG. 4A, the first pupil partial region 501 of the first focus detection pixel 201 is generally conjugated with the light receiving surface of the photoelectric conversion unit 301 whose center of gravity is decentered in the −X direction and the microlens. This represents a pupil region that can be received by the first focus detection pixel 201. The first pupil partial region 501 of the first focus detection pixel 201 has a center of gravity eccentric to the + X side on the pupil plane.

  In FIG. 4A, the second pupil partial region 502 of the second focus detection pixel 202 is generally in a conjugate relationship by the light receiving surface of the photoelectric conversion unit 302 whose center of gravity is decentered in the + X direction and the microlens. This represents a pupil region that can be received by the second focus detection pixel 202. The center of gravity of the second pupil partial region 502 of the second focus detection pixel 202 is eccentric to the −X side on the pupil plane.

  In FIG. 4A, the pupil region 500 can receive light in the entire pixel 200G when the photoelectric conversion unit 301 to the photoelectric conversion unit 304 (first focus detection pixel 201 to second focus detection pixel 204) are all combined. This is a pupil area.

  FIG. 4B shows a cross-sectional view of the pixel structure of the present embodiment shown in FIG. 3A as viewed from the + X side and an exit pupil plane of the imaging optical system. 4 (b), like FIG. 4 (a), in order to correspond to the coordinate axis of the exit pupil plane, the X-axis and Y-axis of the sectional view are reversed with respect to FIG.

  In FIG. 4B, the first pupil partial region 503 of the third focus detection pixel 203 is generally in a conjugate relationship by the light receiving surface of the photoelectric conversion unit 303 whose center of gravity is eccentric in the + Y direction and the microlens. This represents a pupil region that can be received by the third focus detection pixel 203. The third pupil partial region 503 of the third focus detection pixel 203 has an eccentric center of gravity on the −Y side on the pupil plane.

  In FIG. 4B, the first pupil partial region 501 of the first focus detection pixel 201 is generally conjugated with the light receiving surface of the photoelectric conversion unit 301 whose center of gravity is eccentric in the −Y direction and the microlens. This represents a pupil region that can be received by the first focus detection pixel 201. The first pupil partial region 501 of the first focus detection pixel 201 is decentered on the + Y side on the pupil plane.

  FIG. 5 shows a schematic diagram showing the correspondence between the image sensor 24 of this embodiment and pupil division. Light fluxes that have passed through different pupil partial regions from the first pupil partial region 501 to the fourth pupil partial region 504 are incident on each pixel of the image sensor at different angles, and are divided into 2 × 2 first focus detection pixels. Light is received by the fourth focus detection pixel 204 from 201. In this embodiment, the pupil region is divided into two pupils in the horizontal direction and two in the vertical direction. If necessary, one of the pupil divisions in the vertical direction or the horizontal direction may be made one.

  The imaging device 24 of the present invention includes a first focus detection pixel that receives a light beam passing through the first pupil partial region of the imaging optical system, and a second pupil partial region of the imaging optical system that is different from the first pupil partial region. A second focus detection pixel for receiving a light beam passing therethrough, a third focus detection pixel for receiving a light beam passing through a third pupil partial region of an imaging optical system different from the third pupil partial region, and a fourth pupil partial region, A fourth focus detection pixel that receives a light beam passing through a fourth pupil partial region of a different imaging optical system, and a light beam that passes through a pupil region obtained by combining the first pupil partial region and the fourth pupil partial region of the imaging optical system. A plurality of imaging pixels that receive light is arranged. In the imaging device of the present embodiment, each imaging pixel is composed of a first focus detection pixel to a fourth focus detection pixel.

  If necessary, the imaging pixel and the first focus detection pixel to the fourth focus detection pixel are configured as separate pixels, and the first focus detection pixel to the fourth focus detection pixel are partially arranged in a part of the imaging pixel array. It is good also as composition to do.

  In this embodiment, an image signal (captured image) with a resolution of N effective pixels is generated by adding the signals of the sub-pixel 201 to the sub-pixel 204 for each pixel of the image sensor. Further, in this embodiment, the first focus detection signal and the second focus detection signal are added by combining the light reception signals of the first focus detection pixel 201 to the fourth focus detection pixel 204 of each pixel of the image sensor in a combination as necessary. A focus detection signal can be generated.

  In this embodiment, for each pixel, the signals of the sub-pixel 201 and the sub-pixel 203 are added to generate a first focus detection signal in the X direction, and the signals of the sub-pixel 202 and the sub-pixel 204 are added to add the signals in the X direction. A bifocal detection signal can be generated. Since the first focus detection signal in the X direction and the second focus detection signal in the X direction are focus detection signals corresponding to pupil division in the horizontal direction, the imaging plane phase difference AF in the X direction (horizontal direction and horizontal direction) is Is possible.

  Similarly, for each pixel, the signals of the sub-pixel 201 and the sub-pixel 202 are added to generate a first focus detection signal in the Y direction, and the signals of the sub-pixel 203 and the sub-pixel 204 are added to generate a second Y-direction signal. A focus detection signal can be generated. Since the first focus detection signal in the Y direction and the second focus detection signal in the Y direction become focus detection signals corresponding to the pupil division in the vertical direction, the imaging plane phase difference AF in the Y direction (vertical direction and vertical direction) is Is possible.

  In the case of the arrangement of the imaging pixels of the imaging element 24 in the present embodiment, the imaging pixels are arranged in two parts in the X direction and two parts in the Y direction, so that the first focus detection signal and the second focus detection are performed. The signal generation can be selected in the X direction and the Y direction.

[Relationship between defocus amount and image shift amount]
Hereinafter, the relationship between the defocus amount and the image shift amount of the first focus detection signal and the second focus detection signal acquired by the image sensor of the present embodiment will be described.

  FIG. 6 shows a schematic relationship diagram of the defocus amounts of the first focus detection signal and the second focus detection signal and the image shift amount between the first focus detection signal and the second focus detection signal. The imaging element (not shown) of the present embodiment is arranged on the imaging surface 800, and the exit pupil of the imaging optical system is changed from the first pupil partial region 501 to the fourth pupil partial region 504 as in FIGS. Divided into four.

  The defocus amount d is a distance | d | from the imaging position of the subject to the imaging surface, and a negative sign (d <0) indicates a front pin state where the imaging position of the subject is on the subject side from the imaging surface. A rear pin state in which the imaging position of the subject is on the opposite side of the subject from the imaging surface is defined as a positive sign (d> 0). An in-focus state where the imaging position of the subject is on the imaging surface (in-focus position) is d = 0. In FIG. 7, the subject 801 shows an example in a focused state (d = 0), and the subject 802 shows an example in a front pin state (d <0). The front pin state (d <0) and the rear pin state (d> 0) are combined to form a defocus state (| d |> 0).

  In the front pin state (d <0), the luminous flux that has passed through the first pupil partial area 501 (second pupil partial area 502) out of the luminous flux from the subject 802 is once condensed and then the gravity center position G1 of the luminous flux. The image spreads in the width Γ 1 (Γ 2) with (G 2) as the center, resulting in a blurred image on the imaging surface 800. The blurred image is received by the first focus detection pixel 201 and the third focus detection pixel 203 (the second focus detection pixel 202 and the fourth focus detection pixel 204) constituting each pixel arranged in the image sensor, and the first image is received. A focus detection signal (second focus detection signal) is generated.

  Therefore, the first focus detection signal (second focus detection signal) is recorded as a subject image in which the subject 802 is blurred by the width Γ1 (Γ2) at the gravity center position G1 (G2) on the imaging surface 800. The first focus detection signal (second focus detection signal) in the X direction is received by the first focus detection pixel 201 and the third focus detection pixel 203 (second focus detection pixel 202 and fourth focus detection pixel 204). Generated by adding the respective signals. The first focus detection signal (second focus detection signal) in the Y direction is a signal received by the first focus detection pixel 201 and the second focus detection pixel 202 (second focus detection pixel 203 and fourth focus detection pixel 204). Are generated by adding each of them.

  The blur width Γ1 (Γ2) of the subject image of the first focus detection signal (second focus detection signal) generally increases in proportion as the magnitude | d | of the defocus amount d increases. Similarly, the magnitude | p | of the object image displacement amount p (= difference G1-G2 in the center of gravity of the light beam) between the first focus detection signal and the second focus detection signal is also the size of the defocus amount d. As | d | increases, it generally increases in proportion. Even in the rear pin state (d> 0), the image shift direction of the subject image between the first focus detection signal and the second focus detection signal is opposite to that in the front pin state, but the same.

  Therefore, in the present invention, as the magnitude of the defocus amount of the imaging signal obtained by adding the first focus detection signal and the second focus detection signal or the first focus detection signal and the second focus detection signal increases, The amount of image shift between the first focus detection signal and the second focus detection signal increases.

  In the imaging plane phase difference AF, the first focus detection signal and the second focus detection signal are relatively shifted to calculate a correlation amount (first evaluation value) representing the degree of coincidence of the signals, and the correlation (signal The image shift amount is detected from the shift amount that improves the degree of coincidence. As the defocus amount of the image pickup signal increases, the image shift amount is determined based on the relationship that the image shift amount increases between the first focus detection signal and the second focus detection signal. Focus detection is performed by converting into a focus amount.

[shading]
In the image pickup device 24 of the present embodiment, a part of the light beam traveling toward the focus detection pixel group (from the first focus detection pixel to the fourth focus detection pixel) holds the image pickup optical system 10 (an optical element such as a lens and a diaphragm, and this). In some cases, so-called vignetting occurs, which is interrupted by a lens barrel including In this case, at least one of the pair of image signals has a decrease in signal level due to a decrease in the amount of light, distortion of the image signal, and unevenness of the intensity of the image signal (unevenness of light receiving sensitivity for each focus detection pixel: hereinafter referred to as shading) Give rise to In particular, in an interchangeable lens having a lens decentering function, the lens is decentered by each lens decentering mechanism, so that the light beam traveling toward the focus detection pixel group causes shading different from general lens shading.

  FIG. 7 shows a first focus detection signal in the X direction and a second focus detection signal in the X direction when the imaging optical system 10 is decentered in the X direction by the shift mechanism 16. The horizontal axis of each graph represents a signal output pixel that outputs each signal. When X = 0 and Y = 0 at the intersection of the imaging region of the imaging device 24 and the optical axis, one row of Y = 0. These pixels are plotted from the left end to the right end from the end pixel on the −X direction side to the end pixel on the + X direction side. The vertical axis of each graph represents the output value of each signal. Note that the subject at this time represents the output value of the uniform luminance plane.

  In the shift mechanism 16 of the image pickup optical system 10 in the present embodiment, the shift eccentricity amount S can be decentered within a scale of ± 10, with 0 being an uncentered state. Each scale is equally spaced.

  FIG. 7A shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is not decentered (shift eccentricity S = 0).

  FIG. 7B shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is decentered by the shift mechanism 16 to the shift eccentricity S = −2. ing.

  FIG. 7C shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is decentered to the shift eccentricity S = −4 by the shift mechanism 16. ing.

  FIG. 7D shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is decentered by the shift mechanism 16 to the shift eccentricity S = −6. ing.

  FIG. 8 shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is decentered in the X direction by the tilt mechanism 17. The horizontal axis of each graph represents a signal output pixel that outputs each signal. When the optical axis of the imaging region of the image sensor 24 is X = 0 and Y = 0, the pixels in one column of Y = 0 are represented. From the end pixel on the −X direction side to the end pixel on the + X direction side is plotted from the left end to the right end. The vertical axis of each graph represents the output value of each signal. Note that the subject at this time represents the output value of the uniform luminance plane.

  In the tilt mechanism 17 of the imaging optical system 10 in the present embodiment, the tilt decentering amount T can be decentered within a scale of ± 6, with 0 being not decentered. Each scale is equally spaced.

  FIG. 8A shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is not decentered (tilt eccentricity S = 0).

  FIG. 8B shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is decentered to the tilt eccentricity T = −2 by the tilt mechanism 17. ing.

  FIG. 8C shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is decentered to the tilt decentering amount T = −4 by the tilt mechanism 17. ing.

  FIG. 8D shows the first focus detection signal in the X direction and the second focus detection signal in the X direction when the imaging optical system 10 is decentered to the tilt eccentricity T = −6 by the tilt mechanism 17. ing.

  FIG. 9 shows the respective ratios of the output signals of the first focus detection signal and the second focus detection signal obtained from FIGS. 7 (a) to (d) and FIGS. 8 (a) to 8 (d). FIG. 9A shows the ratio of the output signals of the first focus detection signal and the second focus detection signal by the shift mechanism 16 shown in FIGS. 7A to 7D. FIG. 9B shows the ratio of the output signals of the first focus detection signal and the second focus detection signal by the tilt mechanism 17 shown in FIGS. 8A to 8D.

  FIG. 9A shows that the ratio of the first focus detection signal and the second focus detection signal is linearly changed by the shift mechanism 16. Further, in FIG. 9B, the ratio of the first focus detection signal and the second focus detection signal is linearly changed by the tilt mechanism 17, which is a change different from that in FIG. 9A. That is, it can be seen that the shift mechanism 16 and the tilt mechanism 17 have different trends in changes in the first focus detection signal and the second focus detection signal. If this tendency is utilized, the eccentric amount of the current shift mechanism 16 and tilt mechanism 17 can be calculated by calculating the ratio of the −X end and the ratio of the + X end where the change is particularly large.

  Note that the ratio between the first focus detection signal and the second focus detection signal does not depend on the subject and the focus position, and the ratio relationship shown in FIG. 9 does not collapse. Therefore, even in a scene where a general subject is photographed, the tendency of changes in the first focus detection signal and the second focus detection signal can be detected, so that the eccentric amounts of the shift mechanism 16 and the tilt mechanism 17 can be calculated. It is.

[Lens eccentricity detection]
Hereinafter, in this embodiment, a method for calculating the lens eccentricity of the imaging optical system 10 by the eccentricity calculation unit 45 using the pair of image signals output from the image signal generation unit 44 will be described.

  FIG. 10 is a diagram showing the relationship between the amount of decentration when the lens is decentered in the horizontal direction and the signal ratio of the first focus detection signal and the second focus detection signal of the left and right end pixels.

  FIG. 10A shows, as an example, the relationship between the signal ratios of the first focus detection signal and the second focus detection signal when the lens is decentered by the shift mechanism 16 of a predetermined interchangeable lens. The decentering amount of the lens decentered by the shift mechanism 16 can be calculated from the formula calculated from the average of the pixel signal ratios.

  FIG. 10B shows, as an example, the relationship between the signal ratio of the first focus detection signal and the second focus detection signal when the lens is decentered by the tilt mechanism 17 of a predetermined interchangeable lens. The decentering amount of the lens decentered by the tilt mechanism 17 can be calculated from an equation calculated from the average of the pixel signal ratios.

  FIG. 10C shows, as an example, the relationship between the lens eccentricity of a predetermined interchangeable lens and the signal ratio difference between the left and right end pixels. The tilt mechanism 17 and the shift mechanism 16 change the signal ratio of the left and right end pixels. By using the formula calculated from the difference, it is possible to detect whether the eccentric lens is eccentric by the tilt mechanism 17 or the shift mechanism 16.

  In the present embodiment, the calculation was performed using the outputs of the left and right end pixels when obtaining the signal ratio of the first focus detection signal and the second focus detection signal. You may use for calculation, and you may use not only an edge pixel but the output of the pixel of all the lines for calculation, and various deformation | transformation and change are possible within the range of the summary.

[Effect when used for electronic front curtain]
Hereinafter, electronic front curtain photography in which correction is performed using the calculated lens eccentricity will be described with reference to FIG.

  FIG. 11 is a flowchart showing a series of operations for electronic front curtain shooting in a live view state in which correction is performed using the calculated lens eccentricity. When live view shooting starts, first, it waits for SW1 (not shown) to be turned on in S101. When SW1 is turned on, the process proceeds to S102.

  In S102, information stored in the lens storage unit 14 built in the interchangeable lens 1 and information such as focus lens position information output from the lens driving unit 11 are controlled by the camera via the lens control unit 13 and the electrical contact 15. Forward to unit 40. When the transfer ends, the process proceeds to S103. S103 is a photometric operation, and the image sensor 24 can measure the luminance of the subject image formed by the imaging optical system 10. When the photometric operation ends, the process proceeds to S104.

  S104 is a focus detection operation, and the first focus detection signal and the second focus detection signal are output by the image signal generation means 44 from the light incident from the imaging optical system 10 by the focus detection pixels arranged in the image sensor 24. . When the signal output ends, the process proceeds to S105. S105 is a step of acquiring lens decentering information, and the tilt mechanism 17 shift is calculated by the decentering amount calculating means 45 using the output results of the first focus detection signal and the second focus detection signal described above. The lens eccentricity information by the mechanism 16 is acquired. When the acquisition of the lens eccentricity information is completed, the process proceeds to S106.

  In S106, it is determined whether or not the lens is decentered. If the lens is not decentered, the lens-specific exit pupil distance stored in the lens storage unit 14 is acquired, and the process proceeds to S108. If the lens is decentered, the lens-specific exit pupil distance acquired from the lens storage unit 14 in S107 is corrected based on the lens decentering amount calculated in S105, and the process proceeds to S108.

  In S108, for the electronic front curtain scanning, the electronic front curtain scanning pattern is calculated using the exit pupil distance corrected in S107. When the calculation is completed, the process proceeds to S109. S109 waits for SW2 (not shown) to be turned on. When turned on, the process proceeds to S110, where electronic front curtain photography is performed and taken. When the imaging is completed, the process proceeds to S <b> 111, the charge accumulated in the image sensor 24 by exposure is photoelectrically converted by the photoelectric conversion unit 301, and the created image data is stored in the camera storage unit 42. When the storage is completed, the process proceeds to S112.

  In S112, it is determined whether or not a live view start / end button (not shown) is turned on. If turned on, the live view state is finished. If it is not turned on, the process proceeds to S101 and waits for SW1 to be turned on.

  According to the present embodiment, even in a lens where the amount of eccentricity cannot be detected, the amount of eccentricity is calculated from the signal ratio of the first focus detection signal and the second focus detection signal output from the image sensor, and the optimal electron Front curtain scanning and optimum electronic front curtain photography are possible.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 10 Imaging optical system 24 Image pick-up element 44 Image signal generation means 45 Eccentricity amount calculation means

Claims (4)

An imaging optical system (10) capable of decentering at least a part of the lens unit with respect to the optical axis;
An imaging device (24) in which a plurality of imaging pixels are arranged so as to divide the light beam incident from the imaging optical system (10) into a plurality of regions;
Image signal generation means (44) for generating a pair of image signals from output values output by the image sensor (24) photoelectric conversion;
Eccentricity amount calculating means (45) for calculating the eccentricity amount of at least a part of the decentered lens unit of the imaging optical system (10) from the pair of image signals generated by the image signal generating means (44). )When,
An imaging device comprising:   The imaging apparatus according to claim 1, wherein the imaging optical system (10) is capable of decentering at least a part of the lens unit perpendicular to the optical axis. The imaging apparatus according to claim 1, wherein the imaging optical system (10) is capable of rotating at least a part of a lens unit about an optical axis. 2. The imaging device according to claim 1, wherein the imaging device includes an imaging optical system that can split a light beam incident from the imaging optical system into a plurality of directions as a pair of images. Imaging device.