JP5003132B2 - Imaging device and imaging apparatus - Google Patents

Description

  The present invention relates to an image sensor technology capable of generating an image signal based on a subject light image formed by a photographing optical system.

  Some imaging devices have specific pixels (phase difference AF pixels) for performing phase difference detection type autofocus control (hereinafter also referred to as “phase difference AF”).

  For example, according to the technique of Patent Document 1, an imaging element having a plurality of pairs of phase difference AF pixels in which the centers of the openings of the metal light shielding layer are biased in opposite directions with respect to the center of the microlens is provided. In a digital camera, the pair of phase difference AF pixels receive the light beam that has passed through the pair of partial areas in the exit pupil of the photographing lens (shooting optical system) to generate a pair of image rows, and the pair of image rows The phase difference AF is performed by obtaining the shift amount related to.

JP 2005-303409 A

  However, in the technique of Patent Document 1 described above, since the phase difference AF is performed using the pair of specific pixels for phase difference AF described above, the size of the exit pupil increases with the change in the actual aperture value related to the photographing lens. The pair of partial areas are assumed to be within the area assuming a relatively small exit pupil so that an appropriate phase difference AF is possible even if the phase changes. It is not always done. For example, when the actual aperture value is small and the exit pupil is relatively large, the focus detection accuracy may be improved in the phase difference AF by effectively using the large exit pupil to define the pair of partial regions. .

The present invention has been made in view of the above problems, an object of Rukoto improve accuracy out focus inspection.

The first aspect of the present invention, a plurality according to a difference in position in the predetermined direction and the image pickup pixels, a pair of light passing areas of the exit pupil plane to generate an image signal based on the object Utsushitai light image group are classified into groups, and an image pickup element and a phase difference detection pixels to be used in focus detection by phase difference detection method, based on the group used for focus detection by the phase difference detection method on the aperture value of said plurality A phase difference detection unit that performs focus detection by the phase difference detection method based on a signal generated by the phase difference detection pixels belonging to the selected group, and focus detection by the phase difference detection method On the basis of the image signals acquired at a plurality of timings when the focus lens is moved based on the evaluation value, an evaluation value for focus detection by a contrast detection method is obtained. An evaluation value calculation unit for calculating each focus, a first evaluation value that is the evaluation value when the focus lens is moved to a focus position based on focus detection by the phase difference detection method, and the first evaluation value Whether or not the focus lens position is the in-focus position is determined based on the second evaluation value that is the previous evaluation value, and the focus lens position is determined not to be the in-focus position. In this case, the imaging apparatus includes a control unit that performs control to move the focus lens to a focus position detected by using the calculated evaluation value or the newly calculated evaluation value . In the first aspect, the control unit calculates a focus position determination value based on the first evaluation value and the second evaluation value, and the focus position determination value is a value within a predetermined range. In such a case, it may be determined that the position of the focus lens is the in-focus position. In this first aspect, if the control unit determines that the position of the focus lens is not the in-focus position, whether or not the focus lens has passed the in-focus position during the movement of the focus lens. Is determined based on the in-focus position determination value, and when it is determined that the focus lens has not passed through the in-focus position during the movement of the focus lens, the aperture when the first evaluation value is acquired is determined. An evaluation value acquired at the latest position by moving the focus lens in the same direction as the movement direction of the focus lens at the time of focus detection by the phase difference detection method using a step reflecting the depth of focus corresponding to the value Is used as the new first evaluation value, the in-focus position determination value is calculated by using the evaluation value immediately before the new first evaluation value as the new second evaluation value, and the calculated in-focus position determination. The value is the above The value a position of囲内may perform control to move the focus lens. In the first aspect, the control unit determines that the focus lens has passed the focus position when the focus lens moves when it is determined that the position of the focus lens is not the focus position. When the focus lens is driven by focus detection by the phase difference detection method, the plurality of evaluation values calculated at each of the plurality of timings and the focus when the plurality of evaluation values are acquired. You may make it perform control which moves the said focus lens to the focus position detected based on the position of a lens. In the first aspect, the control unit determines whether the position of the focus lens is the in-focus position with the single range as the predetermined range regardless of the selected group. You may do it. In the first aspect, the phase difference detection unit performs focus detection by the phase difference detection method until the focus lens position is detected as a focus position by focus detection by the phase difference detection method. The control unit repeatedly performs the control based on the first evaluation value and the second evaluation value when the focus lens position is detected as a focus position by focus detection by the phase difference detection method. It may be determined whether or not the position of the focus lens is an in-focus position. In the first aspect, the group and the aperture value are associated with each other, and the phase difference detection unit selects the group associated with the aperture value at the time of acquiring the image signal. It may be. In the first aspect, the evaluation value calculation unit is configured to evaluate the evaluation based on the image signal output from the imaging pixel arranged in the vicinity of the phase difference detection pixel belonging to the selected group. A value may be calculated.

According to the present invention, it is possible to improve the accuracy out focus inspection.

<Appearance configuration of imaging device>
1 and 2 are diagrams showing an external configuration of an imaging apparatus 1 according to the embodiment of the present invention. Here, FIGS. 1 and 2 show a front view and a rear view, respectively. FIG. 3 is a longitudinal sectional view of the imaging apparatus 1.

  The imaging device 1 is configured as, for example, a single-lens reflex digital still camera, and includes a camera body 10 and a photographing lens 2 as an interchangeable lens that is detachable from the camera body 10.

  In FIG. 1, on the front side of the camera body 10, a mount portion 301 on which the photographing lens 2 is mounted at the center of the front surface, a lens exchange button 302 disposed on the right side of the mount portion 301, and a front left end (X Left side of the direction), and a mode setting dial 305 disposed on the upper left side of the front (upper left side in the Y direction), and a right upper part of the front. A control value setting dial 306 arranged on the screen and a shutter button 307 arranged on the upper surface of the grip unit 303 are provided.

  In FIG. 2, on the rear side of the camera body 10, there are an LCD (Liquid Crystal Display) 311, a setting button group 312 arranged on the left side of the LCD 311, and a cross key 314 arranged on the right side of the LCD 311. And a push button 315 disposed in the center of the cross key 314. Further, on the back side of the camera body 10, an EVF (Electronic View Finder) 316 disposed above the LCD 311, an eye cup 321 surrounding the EVF 316, and a main switch 317 disposed on the left side of the EVF 316. An exposure correction button 323 and an AE lock button 324 disposed on the right side of the EVF 316, and a flash unit 318 and a connection terminal unit 319 disposed above the EVF 316.

  The mount portion 301 is provided with a plurality of electrical contacts for electrical connection with the mounted taking lens 2 and a coupler for mechanical connection.

  The lens exchange button 302 is a button that is pressed when the photographing lens 2 attached to the mount unit 301 is removed.

  The grip part 303 is a part where the user grips the imaging device 1 at the time of photographing, and is provided with surface irregularities that match the finger shape in order to improve fitting properties. Note that a battery storage chamber and a card storage chamber (not shown) are provided inside the grip portion 303. A battery 69B (see FIG. 4) is stored in the battery storage chamber as a power source for the camera, and a recording medium (for example, a memory card) for recording image data of the photographed image is detachably stored in the card storage chamber. It has become so. The grip unit 303 may be provided with a grip sensor for detecting whether or not the user has gripped the grip unit 303.

  The mode setting dial 305 and the control value setting dial 306 are made of a substantially disk-shaped member that can rotate in a plane substantially parallel to the upper surface of the camera body 10. The mode setting dial 305 is used for various types of shooting such as an automatic exposure (AE) control mode, an autofocus (AF) control mode, a still image shooting mode for shooting a single still image, and a continuous shooting mode for continuous shooting. This mode is used to selectively select a mode and a function installed in the imaging apparatus 1, such as a mode and a reproduction mode for reproducing a recorded image. On the other hand, the control value setting dial 306 is for setting control values for various functions installed in the imaging apparatus 1.

  The shutter button 307 is a push switch that can be operated in a “half-pressed state” that is pressed halfway and further operated in a “full-pressed state”. When the shutter button 307 is half-pressed (S1) in the still image shooting mode, a preparatory operation for capturing a still image of the subject (preparation operations such as setting of exposure control values and focus adjustment) is executed, and the shutter button 307 is operated. When is fully pressed (S2), a photographing operation (a series of operations for exposing the imaging sensor, performing predetermined image processing on the image signal obtained by the exposure, and recording the image signal on a memory card or the like) is performed.

  The LCD 311 includes a color liquid crystal panel that can display an image. The LCD 311 displays an image picked up by the image pickup device 101 (FIG. 3), reproduces and displays a recorded image, and is mounted on the image pickup apparatus 1. The function and mode setting screen is displayed. Note that an organic EL or a plasma display device may be used instead of the LCD 311.

  The setting button group 312 is a button for performing operations on various functions installed in the imaging apparatus 1. The setting button group 312 includes, for example, a selection confirmation switch for confirming the content selected on the menu screen displayed on the LCD 311, a selection cancel switch, a menu display switch for switching the content of the menu screen, a display on / off switch, A display enlargement switch is included.

  The cross key 314 has an annular member having a plurality of pressing portions (triangle marks in the figure) arranged at regular intervals in the circumferential direction, and is not shown and provided corresponding to each pressing portion. The pressing operation of the pressing portion is detected by the contact (switch). The push button 315 is arranged at the center of the cross key 314. The cross key 314 and the push button 315 are used to change the photographing magnification (movement of the zoom lens in the wide direction and the tele direction), frame advance of the recorded image to be reproduced on the LCD 311 and the like, and photographing conditions (aperture value, shutter speed, flash emission). This is for inputting an instruction such as setting or not.

  The EVF 316 includes, for example, a color liquid crystal panel that can display an image, and performs display of an image captured by the image sensor 101 (FIG. 3), reproduction display of a recorded image, and the like. Here, the live view (preview) display for displaying the subject in a moving image mode is performed on the EVF 316 or the LCD 311 based on the image signal sequentially generated by the image sensor 101 before the main shooting (shooting for image recording). The user can visually recognize a subject actually captured by the image sensor 101.

  The main switch 317 is a two-contact slide switch that slides to the left and right. When the switch is set to the left, the power of the imaging apparatus 1 is turned on, and when the switch is set to the right, the power is turned off.

  The flash unit 318 is configured as a pop-up built-in flash. On the other hand, when attaching an external flash or the like to the camera body 10, the connection is made using the connection terminal portion 319.

  The eye cup 321 is a “U” -shaped light shielding member that has light shielding properties and suppresses intrusion of external light into the EVF 316.

  The exposure correction button 323 is a button for manually adjusting an exposure value (aperture value or shutter speed), and the AE lock button 324 is a button for fixing exposure.

  The photographic lens 2 functions as a lens window that captures light (light image) from the subject and also functions as a photographic optical system for guiding the subject light to the image sensor 101 disposed inside the camera body 10. It is. The photographing lens 2 can be detached from the camera body 10 by pressing the lens exchange button 302 described above.

  The taking lens 2 includes a lens group 21 including a plurality of lenses arranged in series along the optical axis LT (FIG. 3). The lens group 21 includes a focus lens 211 (see FIG. 4) for adjusting the focal point and a zoom lens 212 (see FIG. 4) for performing zooming, each in the direction of the optical axis LT. By driving the zoom lens, zooming and focus adjustment are performed. The photographing lens 2 is provided with an operation ring that can rotate along the outer peripheral surface of the lens barrel at a suitable position on the outer periphery of the lens barrel. The zoom lens 212 can be operated by manual operation or automatic operation. It moves in the optical axis direction according to the rotation direction and rotation amount of the operation ring, and is set to a zoom magnification (imaging magnification) according to the position of the movement destination.

  The image sensor 101 is arranged in a direction perpendicular to the optical axis LT on the optical axis LT of the lens group 21 provided in the photographing lens 2 when the photographing lens 2 is attached to the camera body 10. Yes. As the image sensor 101, for example, a plurality of pixels configured with photodiodes are two-dimensionally arranged in a matrix and each has a spectral characteristic, for example, R (red), G (green), or B (blue) color. A CMOS color area sensor (CMOS type image sensor) having color pixels provided with filters is used. The image sensor (imaging sensor) 101 converts an object light image formed by the photographing lens (photographing optical system) 2 into analog electrical signals (image signals) of R (red), G (green), and B (blue) color components. ) To generate and output image signals of R, G, and B colors. The configuration of the image sensor 101 will be described in detail later.

  A shutter unit 40 is disposed in front of the imaging device 1. The shutter unit 40 includes a curtain that moves in the vertical direction, and is configured as a mechanical focal plane shutter that performs an optical path opening operation and an optical path blocking operation of subject light guided to the image sensor 101 along the optical axis LT. The shutter unit 40 can be omitted when the image sensor 101 is an image sensor capable of complete electronic shutter.

<Electrical Configuration of Imaging Device 1>
FIG. 4 is a block diagram illustrating an electrical configuration of the entire imaging apparatus 1. Here, the same members as those in FIGS. 1 to 3 are denoted by the same reference numerals. For convenience of explanation, the electrical configuration of the photographic lens 2 will be described first.

  The photographing lens 2 includes a lens driving mechanism 24, a lens position detection unit 25, a lens control unit 26, and an aperture driving mechanism 27 in addition to the lens group 21 constituting the photographing optical system described above.

  In the lens group 21, a focus lens 211 and a zoom lens 212, and a diaphragm 23 for adjusting the amount of light incident on the image sensor 101 provided in the camera body 10 are arranged in an optical axis LT (FIG. 3) in the lens barrel. The optical image of the subject is captured and formed on the image sensor 101. The focus adjustment operation is performed by driving the lens group 21 in the direction of the optical axis LT by the AF actuator 71M in the camera body 10.

  The lens driving mechanism 24 includes, for example, a helicoid and a gear (not shown) that rotates the helicoid. The lens driving mechanism 24 receives a driving force from the AF actuator 71M via the coupler 74, and moves the focus lens 211 and the like parallel to the optical axis LT. Move in the direction. Note that the movement direction and the movement amount of the focus lens 211 are in accordance with the rotation direction and the rotation speed of the AF actuator 71M, respectively.

  The lens position detection unit 25 is integrated with the lens barrel 22 while being in sliding contact with the encode plate in which a plurality of code patterns are formed at a predetermined pitch in the optical axis LT direction within the movement range of the lens group 21. And a moving encoder brush for detecting the amount of movement of the lens group 21 during focus adjustment. The lens position detected by the lens position detection unit 24 is output as the number of pulses, for example.

  The lens control unit 26 includes a microcomputer in which a memory unit 261 including, for example, a ROM that stores a control program and a flash memory that stores data related to state information is built. The lens control unit 26 includes a communication unit 262 that communicates with the main control unit 62 of the camera body 10. The communication unit 262 includes, for example, a focal length, an exit pupil position, an aperture value, and the like of the lens group 21. While transmitting state information data such as a focusing distance and a peripheral light amount state to the main control unit 62, for example, data on the driving amount of the focus lens 211 is received from the main control unit 62. At the time of photographing, data such as focal length information regarding the photographing lens 2, the position of the focus lens 211, and an aperture value are transmitted from the communication unit 262 to the main control unit 62. The memory unit 261 stores the state information data of the lens group 21 described above, the F number (Fno) of the photographing lens 2, the driving amount data of the focus lens 211 transmitted from the main control unit 62, and the like. The

  The aperture drive mechanism 27 receives the driving force from the aperture drive actuator 73M via the coupler 75 and changes the aperture diameter of the aperture 23.

  Next, the electrical configuration of the camera body 10 will be described. The camera body 10 includes an AFE (analog front end) 5, an image processing unit 61, an image memory 614, a main control unit 62, a flash circuit 63, an operation unit, in addition to the imaging element 101 and the shutter unit 40 described above. 64, VRAM 65 (65a, 65b), card I / F 66, memory card 67, communication I / F 68, power supply circuit 69, battery 69B, focus drive control unit 71A and AF actuator 71M, shutter drive control unit 72A, and shutter drive actuator 72M, an aperture drive control unit 73A, and an aperture drive actuator 73M.

  The image sensor 101 is composed of a CMOS sensor as described above, and the timing control circuit 51 described below starts (and ends) the exposure operation of the image sensor 101, outputs selection of each pixel included in the image sensor 101, and pixels Imaging operations such as signal readout are controlled.

  The AFE 5 gives a timing pulse for causing the image sensor 101 to perform a predetermined operation, and performs predetermined signal processing on an image signal (analog signal group received by each pixel of the CMOS area sensor) output from the image sensor 101. Is converted into a digital signal and output to the image processing unit 61. The AFE 5 includes a timing control circuit 51, a signal processing unit 52, an A / D conversion unit 53, and the like.

  The timing control circuit 51 generates a predetermined timing pulse (a pulse for generating a vertical scanning pulse φVn, a horizontal scanning pulse φVm, a reset signal φVr, etc.) based on the reference clock output from the main control unit 62, and the imaging device 101. And the imaging operation of the image sensor 101 is controlled. In addition, the operation of the signal processing unit 52 and the A / D conversion unit 53 is controlled by outputting predetermined timing pulses to the signal processing unit 52 and the A / D conversion unit 53, respectively.

  The signal processing unit 52 performs predetermined analog signal processing on the analog image signal output from the image sensor 101. The signal processing unit 52 includes a CDS (correlated double sampling) circuit, an AGC (auto gain control) circuit that amplifies the charge signal output from the image sensor 101, a clamp circuit, and the like.

  In the AGC circuit of the signal processing unit 52, the charge signal from each pixel in the pixel array Lp for phase difference AF described later is amplified by a gain (amplification factor) α and each pixel in the pixel column Ln for imaging described later is used. The charge signals from (G pixel 11gb, R pixel 11r, and B pixel 11b) are amplified with a gain β different from the gain α. This is because the phase difference AF pixel that receives the light beam that has passed through a part of the exit pupil of the photographing lens 2 has a lower sensitivity than the photographing pixel, and is therefore amplified with a higher gain than the photographing pixel. This is because it is necessary to ensure an appropriate output level.

  The A / D converter 53 converts the analog R, G, and B image signals output from the signal processor 52 into a plurality of bits (for example, 12 bits) based on the timing pulse output from the timing control circuit 51. ) Are converted into digital image signals.

  The image processing unit 61 performs predetermined signal processing on the image data output from the AFE 5 to create an image file, and includes a black level correction circuit 611, a white balance control circuit 612, a gamma correction circuit 613, and the like. Has been. The image data captured by the image processing unit 61 is temporarily written in the image memory 614 in synchronization with the reading of the image sensor 101. Thereafter, the image data written in the image memory 614 is accessed to access the image processing unit. Processing is performed in each of the 61 blocks.

  The black level correction circuit 611 corrects the black level of each of the R, G, and B digital image signals A / D converted by the A / D conversion unit 53 to a reference black level.

  The white balance correction circuit 612 performs level conversion (white balance (WB) adjustment) of digital signals of each color component of R (red), G (green), and B (blue) based on a white reference corresponding to the light source. Is what you do. That is, the white balance control circuit 612 identifies a portion that is originally estimated to be white based on luminance, saturation data, and the like in the photographic subject based on the WB adjustment data provided from the main control unit 62, and R, G of that portion. , B, the average of the color components, the G / R ratio and the G / B ratio are obtained, and the levels are corrected as R and B correction gains.

  The gamma correction circuit 613 corrects the gradation characteristics of the image data subjected to WB adjustment. Specifically, the gamma correction circuit 613 performs non-linear conversion and offset adjustment using a gamma correction table set in advance for each color component.

  The image memory 614 temporarily stores the image data output from the image processing unit 61 in the photographing mode, and is also used as a work area for performing predetermined processing on the image data by the main control unit 62. It is. In the playback mode, the image data read from the memory card 67 is temporarily stored.

  The main control unit 62 is composed of a microcomputer incorporating a storage unit such as a ROM for storing a control program or a flash memory for temporarily storing data, and controls the operation of each unit of the imaging apparatus 1.

  The flash circuit 63 controls the light emission amount of the external flash connected to the flash unit 318 or the connection terminal unit 319 to the light emission amount set by the main control unit 62 in the flash photographing mode.

  The operation unit 64 includes the mode setting dial 305, the control value setting dial 306, the shutter button 307, the setting button group 312, the cross key 314, the push button 315, the main switch 317, etc., and the operation information is sent to the main control unit 62. It is for input.

  The VRAMs 65a and 65b have a storage capacity of image signals corresponding to the number of pixels of the LCD 311 and the EVF 316, and are buffer memories between the main control unit 62 and the LCD 311 and the EVF 316. The card I / F 66 is an interface for enabling transmission / reception of signals between the memory card 67 and the main control unit 62. The memory card 67 is a recording medium that stores image data generated by the main control unit 62. The communication I / F 68 is an interface for enabling transmission of image data and the like to a personal computer and other external devices.

  The power supply circuit 69 includes a constant voltage circuit, for example, and generates a voltage (for example, 5 V) for driving the entire imaging apparatus 1 such as a control unit such as the main control unit 62, the imaging element 101, and other various driving units. . Note that energization control to the image sensor 101 is performed by a control signal supplied from the main control unit 62 to the power supply circuit 69. The battery 69B includes a primary battery such as an alkaline battery or a secondary battery such as a nickel metal hydride battery, and is a power source that supplies power to the entire imaging apparatus 1.

  The focus drive control unit 71A generates a drive control signal for the AF actuator 71M necessary for moving the focus lens 211 to the in-focus position based on the AF control signal given from the main control unit 62. The AF actuator 71M includes a stepping motor and the like, and applies a lens driving force to the lens driving mechanism 24 of the photographing lens 2 via the coupler 74.

  The shutter drive control unit 72A generates a drive control signal for the shutter drive actuator 72M based on a control signal given from the main control unit 62. The shutter drive actuator 72M is an actuator that performs opening / closing drive of the shutter unit 40.

  The aperture drive control unit 73A generates a drive control signal for the aperture drive actuator 73M based on the control signal given from the main control unit 62. The aperture driving actuator 73M applies a driving force to the aperture driving mechanism 27 via the coupler 75.

  The camera body 10 also includes a phase difference AF calculation circuit 76 and a contrast AF calculation circuit 77 that perform calculations necessary for autofocus (AF) control based on the black level corrected image data output from the black level correction circuit 611. It has.

  The AF operation of the image pickup apparatus 1 using the phase difference AF calculation circuit 76 and the contrast AF calculation circuit 77 and the configuration of the image sensor 101 will be described in detail below.

<Regarding Configuration of Image Sensor 101 and AF Operation of Imaging Device 1>
In the imaging apparatus 1, a phase difference detection AF (position detection method) that performs focus detection by receiving transmitted light that has passed through (passed through) different portions (a pair of partial regions) of the exit pupil of the imaging lens 2 in the imaging element 101. Phase difference AF) is possible. The configuration of the image sensor 101 and the principle of phase difference AF using the image sensor 101 will be described below.

  FIG. 5 is a diagram for explaining the configuration of the image sensor 101.

  As shown in FIG. 5A, the image sensor 101 includes a pixel column Ln for photographing and a pixel column Lp for phase difference AF arranged along the horizontal direction.

  The pixel row Ln for photographing has an R pixel 11r, a G pixel 11g, and a B pixel 11b in which R (red), G (green), and B (blue) color filters are provided on a photodiode. The pixel arrangement of these R pixel 11r, G pixel 11g, and B pixel 11b is a Bayer array.

  The pixel row Lp for phase difference AF is a pixel (specific pixel) for use in phase difference AF, and only subject luminous flux that passes through a pair of left and right partial areas of the exit pupil when the actual aperture value corresponds to F2. Only a subject light beam that passes through a pair of pixels (hereinafter also referred to as “first pixels”) 111 (111a, 111b) and a pair of left and right partial areas of the exit pupil when the actual aperture value corresponds to F6 is received. A pair of pixels (hereinafter also referred to as “second pixels”) 112 (112a, 112b). That is, the specific pixels arranged in the pixel row Lp for phase difference AF are each light flux corresponding to a part of the subject light flux limited by a slit of a light shielding plate BD described later (each light flux Ja in FIGS. 6 to 7 described later). To Jd), a pair of partial areas of the exit pupil plane that are different from each other due to a difference in actual aperture value, that is, a group of the first pixels 111 (hereinafter also referred to as “first pixel group”) and It is divided into a group of second pixels 112 (hereinafter also referred to as “second pixel group”), and each of the first pixel group and the second pixel group receives a subject luminous flux that has passed through a pair of partial areas of the exit pupil. A pair of pixel groups (a group of a pair of first pixels 111a and 111b and a group of a pair of second pixels 112a and 112b) are configured. Further, in the pixel row Lp for phase difference AF, a pair of first pixels 111 and a pair of second pixels 112 are alternately arranged.

  The pair of first pixels 111 includes a first pixel 111a on the left side and a first pixel 111b on the right side that are arranged adjacent to each other, and are arranged along the arrangement direction (horizontal direction) of the pixel row Lp for phase difference AF. Has been. The first pixel 111a on the left side and the first pixel 111b on the right side are the photographing lens 2 through slits (openings) Sa and Sb (FIG. 5B) provided in the light shielding plate BD functioning as a selective transmission part. By selectively transmitting a part of the subject luminous flux that has passed through the exit pupil, the subject luminous flux that passes through a pair of left and right partial areas in the exit pupil whose actual aperture value is equivalent to F2 can be received by the light receiving areas Pa and Pb. It has become. Here, the left first pixel 111a and the right first pixel 111b have a mirror-surface relationship with respect to the positions of the slits Sa and Sb.

  In addition, the pair of second pixels 112 includes a left second pixel 112a and a right second pixel 112b that are disposed adjacent to each other, and extends along the arrangement direction (horizontal direction) of the pixel row Lp for phase difference AF. Are arranged. The second pixel 112a on the left side and the second pixel 112b on the right side are the photographing lens 2 through slits (openings) Ta and Tb (FIG. 5B) provided in the light shielding plate BD functioning as a selective transmission part. By selectively transmitting a part of the subject luminous flux that has passed through the exit pupil, the subject luminous flux that passes through a pair of left and right partial areas in the exit pupil whose actual aperture value is equivalent to F6 can be received by the light receiving areas Qa and Qb. It has become. Here, the second pixel 112a on the left side and the second pixel 112b on the right side have a mirror surface relationship in the positions of the slits Ta and Tb, like the pair of first pixels 111.

  As described above, in the pixel row Lp for phase difference AF, the light shielding plate BD in which the positions of the slits Sa, Sb, Ta, and Tb are different every four pixels is provided (FIG. 5B). Therefore, in the first pixel 111 and the second pixel 112 arranged in the pixel row Lp for phase difference AF, the amount of received light is smaller than that in each of the pixels 11r, 11g, and 11b arranged in the imaging pixel row Ln. In order to improve sensitivity, a color filter is not provided. For this reason, in the pixel row Lp for phase difference AF, pixel data for photographing for one horizontal line is lost. This data loss is dealt with by pixel interpolation for a known general line loss. And In the charge readout of the image sensor 101, a readout method is used for the RGB pixels 11r, 11g, and 11b in the imaging pixel row Ln and the first pixel 111 and the second pixel 112 in the phase difference AF pixel row Lp. The charge can be read simultaneously by making different.

  Next, the principle of phase difference AF using the pixel row Lp for phase difference AF will be described in detail.

  6 and 7 are diagrams for explaining the principle of phase difference AF using the pixel row Lp for phase difference AF in the image sensor 101. FIG. Here, FIG. 6 shows light beams Ja and Jb partially passing through the exit pupil when the actual aperture value of the photographic lens (photographic optical system) 2 corresponds to F2.0. Represents the light beams Jc and Jd partially passing through the exit pupil when the actual aperture value of the photographing lens 2 corresponds to F5.6.

  When the actual aperture value is F2.0, in the pair of first pixels 111a and 111b, as shown in FIG. 6, the light beam Ja that has passed through the right area Epa of the exit pupil passes through the microlens ML and the slit Sa of the light shielding plate BD. The light beam Jb that forms an image in the light receiving region Pa near the left end of the photoelectric conversion unit 110 and passes through the left region Epb of the exit pupil passes through the microlens ML and the slit Sb of the light shielding plate BD and is near the right end of the photoelectric conversion unit 110. An image is formed in the light receiving region Pb. Hereinafter, in the pair of first pixels 111a and 111b, the light reception data obtained from the left first pixel 111a is referred to as “A series data”, and the light reception data obtained from the right first pixel 111b is referred to as “B series data”. For example, A series data and B series data obtained from a pair of first pixels 111a and 111b arranged in a certain pixel row Lp (FIG. 5) for phase difference AF are referred to as “data”. The principle of phase difference AF when the actual aperture value is F2.0 will be described with reference to FIGS.

  FIG. 8 is a diagram illustrating a simulation result when the focal plane is defocused closer to 200 μm from the imaging plane of the image sensor 101. FIG. 9 is a diagram illustrating the focal plane defocused closer to 100 μm from the imaging plane. It is a figure which shows the simulation result in the case of being. FIG. 10 is a diagram showing a simulation result in a focused state where the focal plane coincides with the imaging plane. Further, FIG. 11 is a diagram showing a simulation result when the focal plane is defocused 100 μm away from the imaging plane, and FIG. 12 is a diagram showing the focal plane defocused 200 μm away from the imaging plane. It is a figure which shows the simulation result in a case. 8 to 12, the horizontal axis indicates the positions of the first pixels 111a and 111b in the phase difference AF pixel row Lp, and the vertical axis indicates the output from each of the first pixels 111a and 111b. Yes. 8 to 12, graphs Ga1 to Ga5 (shown by solid lines) represent A-series data, and graphs Gb1 to Gb5 (shown by broken lines) represent B-series data.

  In FIG. 8 to FIG. 12, when comparing the A-sequence image sequence indicated by the A-sequence graphs Ga1 to Ga5 and the B-sequence image sequences indicated by the B-sequence graphs Gb1 to Gb5, the larger the defocus amount, the greater the defocus amount. It can be seen that the shift amount (deviation amount) in the horizontal direction of the image sensor 101 generated between the A-sequence image sequence and the B-sequence image sequence is increased.

When the relationship between the shift amount and the defocus amount in such a pair of image sequences (A-sequence and B-sequence image sequences) is graphed, it is represented as a graph Gc shown in FIG. In FIG. 13, the horizontal axis represents the defocus amount (mm), and the vertical axis represents the difference (number of pixels) of the centroid position of the B-sequence image sequence to the centroid position of the A-sequence image sequence. Incidentally, the center-of-gravity position X _g for each image column, for example, be determined by the following calculation formula (1).

However, in the above equation (1), X _{1 to} X _n represent, for example, the position of the first pixel 111 from the left end in the pixel row Lp for phase difference AF, and Y _{1 to} Y _n represent the positions X ₁ to X _n. The output value from the 1st pixel 111 of _Xn is represented.

  As in the graph Gc shown in FIG. 13, the relationship between the defocus amount and the difference between the center of gravity positions of the pair of image rows is a proportional relationship. This relationship can be expressed by the following equation (2) when the defocus amount is DF (μm) and the difference in the center of gravity is C (μm).

  Here, the coefficient k1 in the above equation (2) represents a gradient Gk (shown by a broken line) with respect to the graph Gc in FIG. 13, and can be obtained in advance by a factory test or the like.

  Next, when the actual aperture value is F5.6, in the pair of second pixels 112a and 112b, as shown in FIG. 7, the light beam Jc that has passed through the right part Eqa of the exit pupil is slit in the microlens ML and the light shielding plate BD. The light beam Jd that passes through Ta and forms an image in the light receiving region Qa on the left side of the center of the photoelectric conversion unit 110 and passes through the left part Eqb of the exit pupil passes through the microlens ML and the slit Tb of the light shielding plate BD. An image is formed in the light receiving region Qb at the right end of the center. Hereinafter, in the pair of second pixels 112a and 112b, the light reception data obtained from the left second pixel 112a is referred to as “A series data”, and the light reception data obtained from the right second pixel 112b is referred to as “B series data”. For example, A series data and B series data obtained from a pair of second pixels 112a and 112b arranged in a certain pixel row Lp (FIG. 5) for phase difference AF are referred to as “data”. The principle of the phase difference AF when the actual aperture value is F5.6 will be described with reference to FIGS.

  FIG. 14 is a diagram illustrating a simulation result when the focal plane is defocused closer to 200 μm from the imaging plane of the image sensor 101. FIG. 15 is a diagram illustrating the focal plane defocused closer to 100 μm from the imaging plane. It is a figure which shows the simulation result in the case of being. FIG. 16 is a diagram illustrating a simulation result in an in-focus state in which the focal plane matches the imaging surface. Further, FIG. 17 is a diagram showing a simulation result when the focal plane is defocused 100 μm away from the imaging plane, and FIG. 18 is a diagram showing the focal plane defocused 200 μm away from the imaging plane. It is a figure which shows the simulation result in a case. 14 to 18, the horizontal axis indicates the position of the second pixels 112a and 112b in the phase difference AF pixel row Lp, and the vertical axis indicates the output from each of the second pixels 112a and 112b. Yes. 14 to 18, graphs Ha1 to Ha5 (shown by solid lines) represent A series data, and graphs Hb1 to Hb5 (shown by broken lines) represent B series data.

  In FIG. 14 to FIG. 18, comparing each A series image sequence indicated by A series graphs Ha1 to Ha5 with each B series image sequence indicated by B series graphs Hb1 to Hb5, the larger the defocus amount, the greater the defocus amount. It can be seen that the shift amount (deviation amount) in the horizontal direction of the image sensor 101 generated between the A-sequence image sequence and the B-sequence image sequence is increased.

When the relationship between the shift amount and the defocus amount in such a pair of image sequences (A-sequence and B-sequence image sequences) is graphed, it is represented as a graph Hc shown in FIG. In FIG. 19, the horizontal axis represents the defocus amount (mm), and the vertical axis represents the difference (number of pixels) of the centroid position of the B-sequence image sequence to the centroid position of the A-sequence image sequence. Incidentally, the center-of-gravity position X _g for each image column, for example, be determined by the above-mentioned calculation equation (1).

  As in the graph Hc shown in FIG. 19, the relationship between the defocus amount and the difference between the centroid positions in the pair of image rows is a proportional relationship. When this relationship is expressed by a mathematical expression in which the defocus amount is DF (μm) and the difference in the center of gravity is C (μm), the following expression (3) is obtained.

  Here, the coefficient k2 in the above equation (3) represents a slope Hk (shown by a broken line) with respect to the graph Hc in FIG. 19, and can be obtained in advance by a factory test or the like.

  As described above, A-series data obtained from the pair of first pixels 111a and 111b when the actual aperture value is F2.0 and from the pair of second pixels 112a and 112b when the actual aperture value is F5.6. Is obtained by calculating the defocus amount using the above equation (2) and the above equation (3) after obtaining the difference (phase difference) between the center of gravity positions of the data and the B series data by the phase difference AF calculation circuit 76. By providing the focus lens 211 with a drive amount corresponding to the defocus amount, autofocus (AF) control for quickly moving the focus lens 211 to the detected focus position (detection focus position) becomes possible. That is, in the imaging apparatus 1, a pair of first light beams that receive subject light beams Ja and Jb (Jc, Jd) that have passed through a pair of partial areas Epa, Epb (Eqa, Eqb) in the exit pupil shown in FIG. 6 (FIG. 7). A pair of image rows is generated based on the charge signal from the group of pixels 111a and 111b (a pair of second pixels 112a and 112b), and the arrangement direction (horizontal direction) of the pixel row Lp for phase difference AF relating to the pair of image rows ) Is detected, the phase difference AF is performed. The relationship between the defocus amount and the drive amount of the focus lens 211 is uniquely determined from the design value of the photographing lens 2 mounted on the camera body 10.

  Further, comparing the graph Gc in FIG. 13 with the graph Hc in FIG. 19, since the gradient Gk of the graph Gc is larger than the gradient Hk of the graph Hc, the graph Gc has a shift amount of a pair of image rows with respect to the defocus amount ( The amount of change in the difference in the center of gravity is increased. That is, the AF accuracy of the phase difference AF can be improved when the actual aperture value is F2.0 than when the actual aperture value is F5.6.

  Therefore, in the imaging apparatus 1 of the present embodiment, when the actual stop is F2.0 or less in the photographic lens 2, for example, the light beams Ja and Jb from the exit pupil shown in FIG. When the phase difference AF using the pair of first pixels 111a and 111b is performed for detection and the actual aperture is larger than F2.0, for example, each light beam Jc from the exit pupil shown in FIG. In order to detect Jd and perform focus detection, phase difference AF using a pair of second pixels 112a and 112b is performed.

  In general, in consideration of the depth of field of a digital camera, it is preferable to perform final focusing by focus detection (contrast AF) using a contrast detection method with higher focusing accuracy than phase difference AF. Thus, the imaging apparatus 1 of the present embodiment also employs contrast AF in order to achieve highly accurate focusing. The principle of this contrast AF will be described below.

  In contrast AF in the imaging apparatus 1, the pixel group of the G pixel 11g is read out in an AF area set in a part of the photographing range (for example, the central part), and an AF evaluation value is calculated. The AF evaluation value is calculated, for example, as the sum of absolute values of adjacent differences of the G pixel 11g in the AF area.

  Here, if the AF evaluation value is sequentially calculated while moving the focus lens 211 in a fixed direction, the AF evaluation value increases monotonously as shown in FIG. 20 and then decreases monotonously with the peak Qk as a boundary. Thus, the relationship between each position of the focal lens 211 and the AF evaluation value is obtained. The focus lens 211 is moved until it exceeds the peak of focus, that is, the peak Qk of the AF evaluation value.

Then, as shown in FIG. 20, AF evaluation values D _n−1 , D _n , D _{n + 1} near the peak Qk and the positions P _n−1 , P _n , P _{n + 1 of the} focus lens 211 are acquired. Then, the in-focus position P _f of the focus lens 211 can be calculated using the quadratic interpolation approximation formula shown in the following formula (4).

  In the contrast AF described above, an AF evaluation value is obtained by the contrast AF calculation circuit 77, and the focus lens 211 is moved to the in-focus position obtained by the above equation (4) by the focus drive control unit 71A. Autofocus control with high focus accuracy is possible.

  In the imaging apparatus 1 of the present embodiment, hybrid AF is performed in which phase difference AF using the pixel row Lp for phase difference AF and contrast AF using the pixel row Ln for photographing are used in combination. A specific operation of the imaging apparatus 1 relating to the hybrid AF will be described below.

  In the above description, the hill-climbing AF using a general contrast method has been described. In the present embodiment, the hybrid AF described below can be moved to the in-focus position even when the peak Qk is not exceeded.

<Operation of Imaging Device 1>
FIG. 21 is a flowchart showing the basic operation of the imaging apparatus 1. This operation is executed by the main control unit 62.

  First, the power source of the imaging apparatus 1 is turned on by the main switch 317, and the imaging element 101 is activated (step ST1).

  In step ST <b> 2, Fno of the photographing lens 2 attached to the mount unit 301 of the camera body 10 is acquired by the main control unit 62. Here, the Fno information stored in the memory unit 261 of the lens control unit 26 in the photographing lens 2 is taken into the main control unit 62.

  In step ST3, automatic exposure control (AE) is performed based on the output from the image sensor 101. By this AE operation, the electronic shutter speed (exposure time) of the image sensor 101, the aperture 23 of the photographing lens 2, and the gain of the AGC circuit of the signal processing unit 52 are changed.

  In step ST4, the current actual aperture value (Fno) is acquired. That is, the actual aperture value (Fno) is acquired based on the opening of the aperture 23 set in step ST3 and the (current) focal length of the taking lens 2.

  In step ST5, it is determined whether the shutter button 307 has been half-pressed (S1) by the user. If half-pressed, the process proceeds to step ST6. If not half-pressed, the process returns to step ST3.

  In step ST6, an AF evaluation value is calculated and acquired by the contrast AF calculation circuit 77 based on the output from the G pixel 11g in the AF area of the image sensor 101. Here, the pixel evaluation cycle (frame rate) in the image sensor 101 is set to 240 fps, and the AF evaluation value is calculated.

  In step ST7, the position of the focus lens 211 is detected based on the number of pulses output from the lens position detection unit 25 of the photographing lens 2. Here, it is preferable to detect the position of the focus lens 211 at the exposure center time (intermediate time of the exposure time) of the G pixel 11g used in the calculation of the AF evaluation value in step ST6.

  In step ST8, the current actual aperture value (Fno) is acquired. Specifically, the current actual aperture value in consideration of the position of the focus lens 211 detected in step ST7 is acquired from the actual aperture value acquired in step ST4. This is because the position of the focus lens 211 is changed by phase difference AF performed in step ST10 and step ST11 described later, and thus an accurate actual aperture value reflecting the latest position is obtained.

  That is, in step ST8, the actual aperture value is acquired based on the focal length related to the imaging lens (imaging optical system) 2, the position of the focus lens 211, and the opening of the aperture 23.

  In step ST9, it is determined whether the actual aperture value (Fno) acquired in step ST8 is greater than 2.0. Here, when Fno is larger than 2.0, the process proceeds to step ST10 in which the second pixel group including the second pixels 112 is selected by the phase difference AF, and when Fno is 2.0 or less, The process proceeds to step ST11 in which a first pixel group including one pixel 111 is selected by phase difference AF.

  In step ST10, phase difference AF is performed using output signals from the pair of second pixels 112a and 112b in the pixel row Lp for phase difference AF. Specifically, the phase difference AF calculation is performed on the difference between the centroid positions of the A-series data obtained from the left second pixel 112a and the B-series data obtained from the right second pixel 112b in the pair of second pixels. The focus lens 211 is driven by using the above equation (3) so that the difference between the positions of the center of gravity obtained by the circuit 76 is eliminated.

  In step ST11, phase difference AF is performed using output signals from the pair of first pixels 111a and 111b in the pixel row Lp for phase difference AF. Specifically, the phase difference AF calculation is performed on the difference between the centroid positions of the A series data obtained from the left first pixel 111a and the B series data obtained from the right first pixel 111b in the pair of first pixels. The focus lens 211 is driven using the above equation (2) so as to eliminate the difference in the center of gravity obtained by the circuit 76.

  Through the operations in steps ST9 to ST11 described above, a pair of image sequences (A-sequence image sequence and B sequence) used for the phase difference AF from the two pixel groups of the first pixel group and the second pixel group according to the actual aperture value. One pixel group that generates a charge signal related to a series of image sequences) is selected. Thereby, an appropriate pixel group can be selected.

  In step ST12, it is determined whether the focus adjustment by the phase difference AF is completed. Here, when the focus adjustment by the phase difference AF is completed, the process proceeds to step ST13, and when it is not completed, the process returns to step ST6.

  By repeating the above steps ST6 to ST12 until the focus adjustment by the phase difference AF is completed, when the focus lens 211 is driven by the phase difference AF, an AF evaluation value (focus detection information) for each position of the focus lens 211. Is acquired as the focus detection history information. The history information of the AF evaluation value is stored in the memory of the main control unit 62, for example.

In step ST13, the last AF evaluation value D _m that was last calculated among the history information of the phase difference AF evaluation value calculated in the AF, 1 preceding the final AF evaluation value D _m of the (pre-final) An AF evaluation value D _m-1 is acquired.

At step ST14, final ratio of the previous AF evaluation value D _m-1 final AF evaluation value D _m for it is determined whether the 1.01 or less 0.99 or more. This is because when the ratio of the final AF evaluation value D _{m to} the previous AF evaluation value D _m−1 is within 100% ± 1%, the peak Qk of the AF evaluation value with a gentle slope (FIG. 20). This is because the focus lens 211 is driven in the vicinity, so that the position of the focus lens 211 is regarded as the focus position and the focus position is specified.

In this step ST14, when 0.99 ≦ D _m / D _m−1 ≦ 1.01, that is, the history information of the AF evaluation value (the AF evaluation value D _m−1 before the last and the final AF evaluation value D). If the in-focus position of the focus lens 211 is specified based on _m ), the process goes out of this flowchart. Otherwise, the process proceeds to step ST15.

At step ST15, final ratio of the previous AF evaluation value D _m-1 final AF evaluation value D _m for judges greater than 1. Here, if D _m / D _m-1 > 1, it is determined that the AF evaluation value is monotonously increasing, and the process proceeds to step ST16. If D _m / D _m-1 ≦ 1, The AF evaluation value is determined to be monotonously decreasing, and the process proceeds to step ST21.

In step ST16, as in step ST6, the AF evaluation value D1 is acquired based on the output from the G pixel 11g in the AF area of the image sensor 101. Note that immediately after the completion of the focus adjustment by the phase difference AF, the final AF evaluation value _Dm is acquired from the AF evaluation value history information as the AF evaluation value D1.

  In step ST17, the focus lens 211 is additionally driven by 1Fδ corresponding to the focal depth (depth of field) in the same direction as the driving direction by the phase difference AF. Here, F is an F-number that represents an actual aperture for the photographic lens (photographic optical system) 2, and δ is twice the pixel pitch of the image sensor 101 (for example, δ = 12 μm for a pixel pitch of 6 μm).

  In step ST18, as in step ST6, the AF evaluation value D2 is acquired based on the output from the G pixel 11g in the AF area of the image sensor 101.

  In step ST19, it is determined whether the ratio of the AF evaluation value D2 acquired in step ST18 to the AF evaluation value D1 acquired in step ST16 is 0.99 or more and 1.01 or less. This is because, in the state where the AF evaluation value does not exceed the peak Qk (FIG. 20) and increases monotonously, for example, as shown in FIG. When the ratio of the AF evaluation value D1 to the AF evaluation value D2 is within 100% ± 1%, in other words, the difference Ef between the AF evaluation value D2 and the AF evaluation value D1 is equal to the AF evaluation value D1. If the focus lens 211 is 1% or less, the focus lens 211 is driven at a gentle slope near the peak Qk (FIG. 22) of the AF evaluation value. This is for the purpose of specifying the in-focus position.

  In this step ST19, when 0.99 ≦ D1 / D2 ≦ 1.01, the process goes out of this flowchart. Otherwise, the focus lens 211 still reaches the vicinity of the peak Qk (FIG. 20) of the AF evaluation value. It judges that it has not carried out, and progresses to step ST20.

  In step ST20, it is determined whether the follow-up driving of the focus lens 211 performed in step ST17 has been performed n (for example, n = 3) times. This is because when the follow-up driving of the focus lens 211 is performed many times, focusing is considered difficult and the AF operation is terminated. Here, when the follow-up drive is performed n times, the process exits this flowchart, and when it is less than n times, the process returns to step ST16.

In step ST21, the focus lens 211 is driven back to the peak position of the AF evaluation value. That is, when the ratio of the final AF evaluation value D _m Final before for AF evaluation value D _m-1 is determined to less than 1 in step ST15, the current position of the focus lens 211 is the peak position of the AF evaluation value Is determined, and the in-focus position of the focus lens 211 is specified using the above-described equation (4). Then, the focus lens 211 that has passed the peak position (focus position) of the AF evaluation value by the phase difference AF is driven so as to return to the specified focus position.

  In the image pickup apparatus 1 described above, the image pickup element 101 having a pair of first pixels 111a and 111b and a pair of second pixels 112a and 112b having different slit positions on the light shielding plate BD is provided. Therefore, if the pair of first pixels and the pair of second pixels are switched according to the actual aperture value of the photographing lens (photographing optical system) 2, focus detection accuracy can be improved in the phase difference AF. That is, since the pair of first pixels 111a and 111b can be used in the case of a relatively small actual aperture value, phase difference AF with higher accuracy than before can be performed.

  Further, in the imaging device 101 of the imaging device 1, a part of the subject luminous flux that has passed through the exit pupil of the photographing lens 2 is selectively transmitted by the slits Sa, Sb, Ta, and Tb (FIGS. 6 to 7) of the light shielding plate BD. Therefore, the light beam necessary for the phase difference AF can be easily received at the first pixel 111 and the second pixel 112.

<Modification>
In the imaging device in the above-described embodiment, it is not essential to have the pixel row Lp for phase difference AF in which a pair of first pixels and a pair of second pixels are alternately arranged as shown in FIG. As shown in FIG. 23, a phase difference AF pixel row Lpa in which only a pair of first pixels 111a and 111b is arranged, and a phase difference AF pixel row Lpb in which only a pair of second pixels 112a and 112b are arranged. You may have.

  Further, as shown in FIG. 24, the phase difference is a pixel arrangement in which the pair of second pixels 112a and 112b, the pair of first pixels 111a and 111b, and the color pixels (G pixel 11g and R pixel 11r) are sequentially repeated. You may have the pixel row Lq for AF. In this way, in the pixel array (pixel array) Lq for phase difference AF arranged along the horizontal line direction, the first pixel and the second pixel are included together with the color pixel from which the pixel data for photographing can be acquired. The pixel interpolation is less than the above-described pixel rows Lp, Lpa, and Lpb for phase difference AF, in which the image data for all the horizontal lines is missing, and the image quality is improved.

  In the embodiment described above, it is not essential to perform the phase difference AF using the pair of first pixels 111a and 111b and the pair of second pixels 112a and 112b having the light shielding plate BD in which the slits are formed. The phase difference AF may be performed using a pair of first pixels 111c and 111d and a pair of second pixels 112c and 112d as shown in FIG.

  FIG. 25 is a diagram for explaining a configuration of a pair of first pixels 111c and 111d according to a modification of the present invention.

  The pair of first pixels 111c and 111d is a microlens having light-shielding layers B1 and B2 that are blackened with a pigment or paint except for the light transmission regions Sc and Sd corresponding to the slits Sa and Sb in FIG. ML is provided, and a part of the subject luminous flux that has passed through the exit pupil of the photographing lens 2 is selectively transmitted by the light transmission regions Sc and Sd.

  In the pair of first pixels 111c and 111d having such a configuration, when the actual aperture value is F2.0, the light beam Ja that has passed through the right area Epa of the exit pupil passes through the light transmission area Sc in the microlens ML. The light beam Jb that forms an image in the light receiving region Pa near the left end of the photoelectric conversion unit 110 and passes through the left region Epb of the exit pupil passes through the light transmission region Sd in the microlens ML and near the right end of the photoelectric conversion unit 110. An image is formed in the light receiving region Pb.

  FIG. 26 is a diagram for explaining a configuration of a pair of second pixels 112c and 112d according to a modification of the present invention.

  The pair of second pixels 112c and 112d are microlenses having light-shielding layers B3 and B4 blackened with a pigment or paint except for the light transmission regions Tc and Td corresponding to the slits Ta and Tb in FIG. ML is provided, and a part of the subject luminous flux that has passed through the exit pupil of the photographing lens 2 is selectively transmitted through the light transmission regions Tc and Td.

  In the pair of second pixels 112c and 112d having such a configuration, when the actual aperture value is F5.6, the light beam Jc that has passed through the right region Eqa of the exit pupil passes through the light transmission region Tc in the microlens ML. The light beam Jd that forms an image in the light receiving region Qa on the left side of the center of the photoelectric conversion unit 110 and passes through the left region Eqb of the exit pupil passes through the light transmission region Td in the microlens ML and is located on the right side of the center of the photoelectric conversion unit 110. An image is formed in the light receiving region Qb.

  The phase difference between the pair of first pixels 111c and 111d and the pair of second pixels 112c and 112d is the same as that of the first pixels 111a and 111b and the pair of second pixels 112a and 112b shown in FIGS. If the AF is switched according to the actual aperture value of the photographic lens 2, the focus detection accuracy can be improved as compared with the conventional case.

  Further, in the first pixels 111c and 111d and the second pixels 112c and 112d, photographing is performed by the microlens ML as a selective transmission portion in which the light shielding layers B1 to B4 having the light transmission regions Sc, Sd, Tc and Td are formed on the surface. Since part of the subject luminous flux that has passed through the exit pupil of the lens 2 is selectively transmitted, the luminous flux necessary for the phase difference AF can be easily received in the first pixels 111c and 111d and the second pixels 112c and 112d.

  In the imaging device in the above embodiment, it is not essential that the two pixel rows Ln for photographing are sandwiched between the pixel rows Lp for phase difference AF as shown in FIG. The arrangement may be such that one or three or more imaging pixel columns Ln are sandwiched between the pixel columns Lp.

  A color filter may be provided for the first pixel 111 and the second pixel 112 in the above embodiment. Although the sensitivity is reduced by this color filter, color pixel data for photographing can be acquired.

  In the above-described embodiment, for the phase difference AF pixel column, the first pixel group including the first pixels 111 corresponding to the actual aperture value F2 and the second pixel 112 including the second pixels 112 corresponding to the actual aperture value F6. It is not essential to have only a pixel group, and a third pixel group consisting of third pixels corresponding to an intermediate actual aperture value (for example, F3) may be added.

  In such a pixel row for phase difference AF, the first pixel group, the second pixel group, or the third pixel group is selected according to the actual aperture value related to the photographing lens 2. Specifically, when the actual diaphragm Fno is 2.0 or less, the first pixel group is selected, and when the actual diaphragm Fno is larger than 3.0, the second pixel group is selected. On the other hand, when the actual aperture Fno is larger than 2.0 and not larger than 3.0, the third pixel group is selected.

  In this way, by selecting one pixel group from the first to third pixel groups according to the actual aperture value, it is possible to perform phase difference AF with higher accuracy than in the case of only the first pixel and the second pixel described above. . In the pixel column for phase difference AF, a different pixel group may be added.

  In the imaging device in the above embodiment, it is not essential that the photographic lens 2 is detachable from the camera body 10, and the photographic lens 2 may be fixed to the camera body 10.

  For the AF evaluation value in the above embodiment, it is not essential to calculate the absolute value sum of the adjacent differences in the G pixel 11g in the AF area, and the absolute value sum of the squares of the adjacent differences is calculated. Also good.

- operation of the imaging device in the above embodiments, contact with the ratio of the final AF evaluation value D _m for AF evaluation value D _m-1 before last is within 1% 100% ± to step ST14 in FIG. 21 It is not essential to determine whether or not, for example, it may be determined whether or not it is within 100% ± 3%.

  In the operation of the imaging apparatus in the above embodiment, it is not essential to drive the focus lens 211 by 1Fδ in step ST17 in FIG. That is, it is only necessary to drive the drive amount based on the focal depth of the photographic lens 2.

1 is a diagram illustrating an external configuration of an imaging apparatus 1 according to an embodiment of the present invention. 1 is a diagram illustrating an external configuration of an imaging apparatus 1. FIG. 1 is a longitudinal sectional view of an imaging apparatus 1. FIG. 2 is a block diagram illustrating an electrical configuration of the entire imaging apparatus 1. FIG. FIG. 2 is a diagram for describing a configuration of an image sensor 101. 4 is a diagram for explaining the principle of phase difference AF using an image sensor 101. FIG. 4 is a diagram for explaining the principle of phase difference AF using an image sensor 101. FIG. FIG. 10 is a diagram illustrating a simulation result when the focal plane is defocused closer to 200 μm from the imaging surface of the image sensor 101 at an actual aperture value F2.0. It is a figure which shows the simulation result in case the focal plane defocuses to the near 100 micrometer side from the imaging surface in the real aperture stop F2.0. It is a figure which shows the simulation result of the focusing state in which the focal plane corresponds to the imaging surface in the real aperture value F2.0. It is a figure which shows the simulation result in case the focal plane is defocused to the 100 micrometer far side from the imaging surface in the real aperture value F2.0. It is a figure which shows the simulation result in case the focal plane is defocused to the 200-micrometer far side from the imaging surface in the real aperture value F2.0. It is a figure for demonstrating the graph Gc which shows the relationship between the difference of the gravity center position of a pair of image sequence in the real aperture value F2.0, and the defocus amount. FIG. 10 is a diagram illustrating a simulation result when the focal plane is defocused closer to 200 μm from the imaging surface of the image sensor 101 at an actual aperture value F5.6. It is a figure which shows the simulation result in case the focal plane is defocused to the near 100 micrometer side from the imaging surface in the real aperture value F5.6. It is a figure which shows the simulation result of the in-focus state in which the focal plane corresponds to the imaging surface in actual aperture value F5.6. It is a figure which shows the simulation result in case the focal plane is defocused to the 100 micrometer far side from the imaging surface in the real aperture value F5.6. It is a figure which shows the simulation result in case the focal plane defocuses to the 200 micrometer far side from the imaging surface in the real aperture value F5.6. It is a figure for demonstrating the graph Gc which shows the relationship between the difference of the gravity center position of a pair of image sequence in the real aperture value F5.6, and the defocus amount. It is a figure for demonstrating the principle of contrast AF. 3 is a flowchart showing a basic operation of the imaging apparatus 1. 6 is a diagram for explaining an AF operation of the imaging apparatus 1. FIG. It is a figure for demonstrating the pixel row Lpa and Lpb for phase difference AF which concerns on the modification of this invention. It is a figure for demonstrating the pixel row Lq for phase difference AF which concerns on the modification of this invention. It is a figure for demonstrating the structure of a pair of 1st pixel 111c, 111d which concerns on the modification of this invention. It is a figure for demonstrating the structure of a pair of 2nd pixel 112c, 112d which concerns on the modification of this invention.

Explanation of symbols

1 Imaging device 2 Shooting lens (interchangeable lens)
DESCRIPTION OF SYMBOLS 10 Camera body 11b B pixel 11g G pixel 11r R pixel 23 Diaphragm 25 Lens position detection part 76 Phase difference AF calculating circuit 77 Contrast AF calculating circuit 101 Imaging element 110 Photoelectric conversion part 111a-111b, 111c-111d A pair of 1st pixel 112a -112b, 112c-112d A pair of second pixels 211 Focus lens 311 LCD
316 EVF
BD Light shielding plates B1 to B4 Light shielding layer Ln Pixel rows for imaging Lp, Lpa, Lpb, Lq Pixel rows for phase difference AF ML Micro lens Sa, Sb, Ta, Tb Slit Sc, Sd, Tc, Td Light transmission region

Claims (8)

And imaging pixels for generating an image signal based on the object Utsushitai light image are classified into a plurality of groups according to a difference in position in the predetermined direction of the pair of light passing areas of the exit pupil plane, the phase difference An image sensor including a phase difference detection pixel used for focus detection by a detection method;
A group used for focus detection by the phase difference detection method is selected from the plurality of groups based on an aperture value, and the phase difference is based on a signal generated by the phase difference detection pixels belonging to the selected group. A phase difference detection unit that performs focus detection by a detection method;
Based on the image signals acquired at a plurality of timings when the focus lens is moved based on the focus detection by the phase difference detection method, an evaluation value for focus detection by the contrast detection method is calculated for each of the plurality of timings. An evaluation value calculation unit to perform,
A first evaluation value that is the evaluation value when the focus lens moves to a focus position based on focus detection by the phase difference detection method, and a second evaluation value that is one evaluation prior to the first evaluation value. Based on the evaluation value, it is determined whether or not the position of the focus lens is an in-focus position. If it is determined that the position of the focus lens is not the in-focus position, the calculated evaluation value or a new value is determined. A control unit that performs control to move the focus lens to a focus position that is detected using the evaluation value calculated in
An imaging apparatus comprising: The control unit calculates a focus position determination value based on the first evaluation value and the second evaluation value, and when the focus position determination value is a value within a predetermined range, the focus lens The imaging apparatus according to claim 1, wherein the position is determined to be an in-focus position. When it is determined that the position of the focus lens is not the focus position, the control unit determines whether or not the focus lens has passed through the focus position determination value based on the focus position determination value. When the focus lens is determined to have not passed through the in-focus position, the depth of focus corresponding to the aperture value at the time of obtaining the first evaluation value is reflected. The focus lens is moved in the same direction as the movement direction of the focus lens at the time of focus detection by the phase difference detection method using a step, and the evaluation value acquired at the latest position is set as a new first evaluation value, The in-focus position determination value is calculated using the evaluation value immediately before the new first evaluation value as a new second evaluation value, and the calculated in-focus position determination value is a value within the predetermined range. At the position Imaging device according to claim 2, wherein the performing control to move the Kasurenzu. The control unit detects the phase difference when it is determined that the position of the focus lens is not the in-focus position, and when the focus lens is determined to have passed through the in-focus position during the movement of the focus lens. Detected based on the plurality of evaluation values calculated at each of the plurality of timings when the focus lens is driven by focus detection by a method and the position of the focus lens when the plurality of evaluation values are acquired. The imaging apparatus according to claim 3, wherein control is performed to move the focus lens to a focused position. The imaging apparatus according to claim 2, wherein the control unit determines whether the position of the focus lens is a focus position with a single range as the predetermined range regardless of the selected group. The phase difference detection unit repeatedly performs focus detection by the phase difference detection method until it is detected by focus detection by the phase difference detection method that the position of the focus lens is a focus position,
The control unit detects the focus lens based on the first evaluation value and the second evaluation value when the focus lens position is detected as a focus position by focus detection by the phase difference detection method. To determine whether or not the position is the in-focus position
The imaging device according to claim 1. The group is associated with the aperture value;
The phase difference detection unit selects a group associated with the aperture value at the time of acquiring the image signal.
The imaging device according to claim 1. 2. The evaluation value calculation unit according to claim 1, wherein the evaluation value calculation unit calculates the evaluation value based on the image signal output from the imaging pixel arranged in the vicinity of the phase difference detection pixel belonging to the selected group . Imaging device.

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