JP2017223870A - Imaging device and control method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce focusing deviations accompanied by an insertion state into an optical path of a half mirror in consideration for an influence of errors due to K value in an imaging device equipped with the half mirror.SOLUTION: An imaging device has: a main mirror that is configured using a half mirror; imaging means that receives a light flux passing through an imaging optical system to photoelectrically convert the received light influx; focus detection means that acquires an amount of image deviation based on a signal output from the imaging means, and detects an amount of defocus from the amount of image deviation, using a conversion coefficient; and control means that controls focus adjustments on the basis of the amount of defocus. The control means is configured to switch, in accordance with the conversion coefficient, a first mode in which focus adjustments are made based on the signal output from the imaging means in a state with the main mirror put downward, and a second mode in which the focus adjustments are made based on the signal output from the imaging means in a state with the mina mirror put upward.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an imaging apparatus having a focus detection function.

  2. Description of the Related Art Conventionally, an imaging apparatus having a configuration (imaging surface phase difference detection method) that realizes focus detection of a phase difference detection method by receiving a light beam that has passed through different exit pupil regions of a photographing optical system by a pixel of an imaging element is known. ing. There is also known an imaging apparatus that includes a half mirror that reflects part of incident light and transmits part of the incident light, and that performs focus detection based on a light beam incident on the image sensor with the half mirror inserted in the optical path. ing. In this way, when performing focus detection by the imaging surface phase difference detection method based on the light beam incident through the half mirror, if the half mirror is withdrawn from the optical path after focusing, the image plane position is determined. There is a risk of changing and out of focus.

  Patent Document 1 describes a configuration in which the defocus amount is offset-corrected by the amount of image plane movement due to insertion of the half mirror into the optical path in focus detection before the release button is pressed. The correction amount at this time is an amount determined theoretically or experimentally in advance, and is determined according to information on the image height and the aperture opening F value acquired from the interchangeable lens. In another embodiment of Patent Document 1, focus detection is performed again in a state where the release button is pressed and the half mirror is moved to the retracted position, and imaging is performed after the focus lens is moved to the in-focus position. Is described.

Japanese Patent No. 5610005

  However, Patent Document 1 does not consider the influence of an error due to a K value that is a conversion coefficient for calculating the defocus amount from the image shift amount in the focus detection of the phase difference detection method. Although it is assumed that the imaging apparatus has K value data corresponding to each condition, if the influence of the K value error is large, the defocus amount deviates greatly from the ideal value. When the influence of the K value error is large in this way, the accuracy of the defocus amount obtained by the offset correction of Patent Document 1 may be low. Further, if the focus adjustment operation is performed again in a state where the release button is pressed and the half mirror is moved to the retracted position, the time lag from when the release button is pressed until imaging is increased.

  In view of the above-described problems, the present invention reduces the out-of-focus caused by the change in the insertion state of the half mirror in the optical path in consideration of the influence of the error due to the K value in the imaging device including the half mirror. With the goal.

  In order to achieve the above object, an imaging apparatus according to a first aspect of the present invention includes a first position inserted in an optical path of a light beam that has passed through a photographing optical system, and a second position retracted from the optical path. An optical member that is movable and transmits a part of an incident light beam and reflects a part thereof, an imaging unit that receives and photoelectrically converts a light beam that has passed through the imaging optical system, and is output from the imaging unit A focus detection unit that acquires an image shift amount based on the obtained signal, detects a defocus amount from the image shift amount using a conversion coefficient, and a control unit that controls focus adjustment based on the defocus amount. The control means controls the focus adjustment based on a signal output from the imaging means in a state where the optical member is in the first position, and the optical according to the conversion factor; With the member in the second position Serial and switches the second mode for controlling the focus adjustment based on a signal output from the imaging means.

  According to a second aspect of the present invention, there is provided an imaging apparatus in which an interchangeable lens having a photographic optical system is detachable, wherein the first position inserted in the optical path of a light beam that has passed through the photographic optical system is retracted from the optical path. An optical member that is movable to the second position and transmits a part of the incident light beam and reflects a part thereof; an imaging unit that receives and photoelectrically converts the light beam that has passed through the photographing optical system; A focus detection unit that acquires an image shift amount based on a signal output from the image pickup unit and detects a defocus amount from the image shift amount using a conversion coefficient, and controls focus adjustment based on the defocus amount. Control means and acquisition means for acquiring lens information from the interchangeable lens, wherein the control means is output from the imaging means in a state where the optical member is in the first position in accordance with the lens information. Focus on the signal Switching between a first mode for controlling a node and a second mode for controlling focus adjustment based on a signal output from the imaging means in a state where the optical member is at the second position. .

  According to the present invention, in an imaging apparatus provided with a half mirror, it is possible to reduce the focus shift caused by a change in the insertion state of the half mirror in the optical path in consideration of the error due to the K value.

FIG. 3 is a cross-sectional view illustrating a configuration of a digital single-lens reflex camera (mirror down state) in the present embodiment. Sectional drawing which shows the structure of the digital single-lens reflex camera (mirror up state) in this embodiment. 1 is a block diagram showing an electrical configuration of a digital single-lens reflex camera according to an embodiment. 5 is a flowchart illustrating focus adjustment control in the first embodiment. 3A and 3B illustrate a structure of an imaging pixel used for an imaging element. 3A and 3B illustrate a structure of a focus detection pixel used for an image sensor. The figure explaining the structure of the other pixel for focus detection used for an image sensor. 9 is a flowchart showing focus adjustment control in the second embodiment. 10 is a flowchart showing focus adjustment control in the third embodiment.

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

(First embodiment)
1 and 2 are diagrams illustrating a configuration of a digital single-lens reflex camera as an example of an imaging apparatus according to the first embodiment. 1 and 2, an interchangeable lens 3 is detachably mounted on a mount 2 fixed to a main body 1 (hereinafter referred to as a camera main body) of a digital single-lens reflex camera. The mount 2 is provided with an interface unit (not shown) for communicating various signals with the interchangeable lens 3 and supplying power to the interchangeable lens 3 from the camera body 1.

  Inside the interchangeable lens 3, an optical system including a focus lens (focus element) 3a, a variable power lens 3b, and a diaphragm 19 is accommodated. An optical system including the focus lens 3a, the variable power lens 3b, and the diaphragm 19 is referred to as a photographing optical system. In the drawing, each lens is shown as being constituted by one lens, but it may be constituted by a plurality of lenses.

  In the camera body 1, a main mirror 4 (optical member) configured by using a half mirror that reflects a part of incident light and transmits a part thereof is a down position that is a position inserted in the optical path shown in FIG. 1. The position can be moved to an up position, which is a position retracted from the optical path shown in FIG. When observing a subject image formed by the photographing optical system through a finder optical system to be described later (in the finder observation state), the main mirror 4 is in a down position that is disposed obliquely in the photographing optical path as shown in FIG. Moved. The main mirror 4 arranged at the down position partially reflects the light beam from the photographing optical system and guides it to a finder optical system described later, and guides a part thereof to the image sensor 6. Further, at the time of shooting or during live view display (shooting / live view observation state), the main mirror 4 is moved to the up position retracted from the shooting optical path as shown in FIG. Thereby, the light beam from the photographing optical system is guided to the shutter 5 and the image sensor 6 described later.

  The light shielding plate 7 which is processed to block the transmitted light and suppress the reflection of light on the entire plate is connected to the main mirror 4 by a link mechanism (not shown), and according to the rotation of the main mirror, FIG. 1 and FIG. Move to position 2. In the position of FIG. 2, the light shielding plate 7 is not necessary because it is processed to suppress light reflection while preventing light entering the imaging element 6 from a finder optical system, which will be described later, by blocking transmitted light over the entire plate. Light is prevented from entering the image sensor 6.

  The shutter 5 controls exposure of the image sensor 6 with a light beam from the photographing optical system. The imaging element 6 is configured using a CCD or CMOS image sensor and its peripheral circuit, and photoelectrically converts a subject image and outputs an imaging signal. Various processes are performed on the imaging signal in an image processing circuit 54 (see FIG. 3) described later, and an image signal is generated. The imaging signal is configured to be output independently for all pixels. Some pixels are focus detection pixels, and are configured to output a pair of image signals having parallax. The focus detection circuit 36 calculates using this image signal and performs focus adjustment (AF) based on the obtained defocus amount, thereby enabling AF of the imaging surface phase difference detection method.

  5 to 7 are diagrams illustrating the structures of the imaging pixels and focus detection pixels of the imaging device 6. In the present embodiment, among 4 pixels of 2 rows × 2 columns, pixels having G (green) spectral sensitivity are arranged in 2 diagonal pixels, and R (red) and B (blue) are arranged in the other 2 pixels. A Bayer arrangement in which one pixel having spectral sensitivity is arranged is employed. Then, between the Bayer arrays, focus detection pixels having a structure described later are arranged according to a predetermined rule.

  FIG. 5 shows the arrangement and structure of the imaging pixels. FIG. 5A is a plan view of 2 × 2 imaging pixels. As is well known, in the Bayer array, G pixels are arranged diagonally, and R and B pixels are arranged in the other two pixels. A structure of 2 rows × 2 columns is repeatedly arranged. FIG. 5B is a cross-sectional view taken along the line AA in FIG. ML is an on-chip microlens disposed on the forefront of each pixel, CFR is an R (red) color filter, and CFG is a G (green) color filter. PD (Photo Diode) schematically shows a photoelectric conversion element of a CMOS image sensor. CL (Contact Layer) is a wiring layer for forming signal lines for transmitting various signals in the CMOS image sensor. TL (Taking Lens) schematically shows a photographing optical system of the interchangeable lens 3.

  Here, the on-chip microlens ML and the photoelectric conversion element PD of the imaging pixel are configured to capture the light beam that has passed through the photographing optical system TL as effectively as possible. In other words, the exit pupil EP (Exit Pupil) of the photographing optical system TL and the photoelectric conversion element PD are in a conjugate relationship by the microlens ML, and the effective area of the photoelectric conversion element is designed to be large. Further, FIG. 5B describes the incident light beam of the R pixel, but the G pixel and the B (blue) pixel have the same structure. Therefore, the exit pupil EP corresponding to each RGB pixel for imaging has a large diameter, and the S / N of the image signal is improved by efficiently taking in the light flux (photon) from the subject.

  FIG. 6 shows the arrangement and structure of focus detection pixels for performing pupil division in the horizontal direction (left-right direction or horizontal direction) of the photographing optical system. Here, the horizontal direction is along a straight line that is orthogonal to the optical axis and extends in the horizontal direction when the imaging apparatus is held so that the optical axis of the imaging optical system and the long side of the imaging region are parallel to the ground. Refers to the direction. FIG. 6A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. When obtaining an image signal for recording or viewing, the main component of luminance information is acquired by G pixels. Since human image recognition characteristics are sensitive to luminance information, image quality degradation is easily recognized when G pixels are lost. On the other hand, the R pixel or the B pixel is a pixel that acquires color information (color difference information). However, since human visual characteristics are insensitive to color information, the pixel that acquires color information has some defects. However, image quality degradation is difficult to recognize. Therefore, in the present embodiment, among the pixels of 2 rows × 2 columns, the G pixel is left as an imaging pixel, and the R pixel and the B pixel are replaced with focus detection pixels. The focus detection pixels are denoted as SHA and SHB in FIG.

  FIG. 6B is a cross-sectional view taken along the line AA in FIG. The microlens ML and the photoelectric conversion element PD have the same structure as the imaging pixel shown in FIG. In the present embodiment, since the signal of the focus detection pixel is not used for image generation, a transparent film CFW (white) is disposed instead of the color separation color filter. Further, since pupil division is performed by the image sensor 6, the opening of the wiring layer CL is deviated in one direction with respect to the center line of the microlens ML. Specifically, the pixel SHA and the opening OPHA are biased to the right side and receive the light flux that has passed through the left exit pupil EPHA of the imaging optical system TL. The opening OPHB of the pixel SHB is biased to the left side and receives the light beam that has passed through the right exit pupil EPHB of the photographing optical system TL. The pixels SHA are regularly arranged in the horizontal direction, and a subject image acquired by these pixel groups is defined as an A image. The pixels SHB are also regularly arranged in the horizontal direction, and the subject image acquired by these pixel groups is defined as a B image. Then, by detecting the relative position between the A image and the B image, the amount of defocus (defocus amount) of the subject image can be detected. In the pixels SHA and SHB, focus detection is possible for a subject having a luminance distribution in the horizontal direction of the imaging region, for example, a vertical line, but focus detection is not possible for a horizontal line having a luminance distribution in the vertical direction. Therefore, the latter may also be configured to include pixels that perform pupil division in the vertical direction (longitudinal direction) of the photographing optical system so that the focus state can be detected.

  FIG. 7 shows the arrangement and structure of focus detection pixels for pupil division in the vertical direction (vertical direction or vertical direction) of the photographing optical system. Here, the vertical direction is along a straight line that is perpendicular to the optical axis and extends in the vertical direction when the imaging device is set so that the optical axis of the imaging optical system and the long side of the imaging region are parallel to the ground. The direction. FIG. 7A is a plan view of pixels of 2 rows × 2 columns including focus detection pixels. As in FIG. 7A, the G pixel is left as an imaging pixel, and the R pixel and the B pixel are replaced. Focus detection pixels are used. The focus detection pixels are denoted as SVC and SVD in FIG.

  FIG. 7B is a cross-sectional view taken along the line AA in FIG. The pixel shown in FIG. 6B has a structure in which pupils are separated in the horizontal direction, whereas the pixel in FIG. 7B has a vertical pupil separation direction, but the other pixels have the same structure. is there. The opening OPVC of the pixel SVC receives a light beam that has been biased downward and has passed through the upper exit pupil EPVC of the imaging optical system TL. Similarly, the opening OPVD of the pixel SVD is biased upward and receives the light beam that has passed through the lower exit pupil EPVD of the imaging optical system TL. Pixels SVC are regularly arranged in the vertical direction, and a subject image acquired by these pixel groups is defined as a C image. The pixels SVD are also regularly arranged in the vertical direction, and the subject image acquired by these pixel groups is defined as a D image. Then, by detecting the relative positions of the C image and the D image, it is possible to detect the focus shift amount (defocus amount) of the subject image having the luminance distribution in the vertical direction.

  In addition, instead of providing focus detection pixels as shown in FIGS. 6 and 7, it is possible to enable AF of the imaging surface phase difference detection method by a configuration including a plurality of photoelectric conversion elements corresponding to one microlens. Good. In this case, a signal from one of the photoelectric conversion elements is an A image, and a signal from another photoelectric conversion element is a B image. Further, a signal obtained by combining the A image and the B image can be handled as an imaging signal.

  A subject image is formed on the focusing plate 9 of FIG. 1 by the light beam reflected by the main mirror 4. The pentaprism 10 inverts the subject image formed on the exit surface of the focusing plate 9 into an erect image. The eyepiece 11 guides the light flux from the pentaprism 10 to the user's eyes and allows the user to observe the subject image on the focusing screen 9. An optical system configured using the focus plate 9, the pentaprism 10, and the eyepiece lens 11 is referred to as a viewfinder optical system.

  The display device is configured using a polymer-dispersed liquid crystal panel (PN liquid crystal panel 12) disposed in the vicinity of the focus plate 9 in the finder optical system, and displays various information such as an AF frame in the finder.

  The RGB photometric sensor 13 configured using a CMOS sensor, a CCD sensor, or the like performs photometry of the luminance of the subject image on the focus plate 9 from the image pickup signal by a configuration with a photometric optical system (not shown). Based on the photometric result by the RGB photometric sensor 13, automatic exposure adjustment (AE) is performed. Further, the RGB photometric sensor 13 can perform color measurement of color, face detection from an image generated based on an imaging signal, and the like. A liquid crystal monitor 14 provided outside the camera body displays image signals (live view images and captured images) and various types of information.

  In the interchangeable lens 3, the focus motor 15 serves as a drive source for moving the focus lens 3a in the optical axis direction. The lead screw 16 is rotated by the focus motor 15. The lead screw 16 meshes with a rack attached to the focus lens 3a (actually attached to a holding frame that holds the focus lens 3a). For this reason, when the lead screw 16 is rotated by the focus motor 15, the focus lens 3a moves in the optical axis direction due to the engagement of the lead screw 16 and the rack.

  A pulse plate 17 is attached to the tip of the lead screw 16 so as to be rotatable integrally with the lead screw 16. In the interchangeable lens 3, a photocoupler 18 having a light emitting element and a light receiving element arranged so as to sandwich a part of the pulse plate 17 is arranged. The photocoupler 18 generates a pulse signal every time the light from the light emitting element is received by the light receiving element by the rotation of the pulse plate 17. This pulse signal is input to a focus adjustment circuit 34 (see FIG. 3), which will be described later, and the amount of movement (or position) of the focus lens 3a is detected by counting the number of input pulse signals. The aperture drive unit 20 includes an aperture drive circuit 35 (see FIG. 3) described later, and drives the aperture 19 in the opening / closing direction.

  FIG. 3 is a block diagram showing an electrical configuration of the digital single-lens reflex camera in the present embodiment. A microcomputer (hereinafter referred to as MPU) 30 is a main controller that controls the camera body 1 and the entire camera system. The memory controller 31 controls the operation of the image sensor 6 and controls related to image data. The EEPROM 32 as a memory stores data for performing various controls.

  A lens control circuit 33 provided in the interchangeable lens 3 controls the focus adjustment circuit 34 and the aperture drive circuit 35 in the interchangeable lens 3 in accordance with a signal from the MPU 30 transmitted via the mount 2. Information indicating the target movement amount of the focus lens 3a is input from the lens control circuit 33 to the focus adjustment circuit 34, and a pulse signal (information of the actual movement amount indicating the actual movement amount of the focus lens 3a) is output from the photocoupler 18. ) Is entered. The focus adjustment circuit 34 drives the focus motor 15 based on the information about the target movement amount and the actual movement amount to move the focus lens 3a. The diaphragm drive circuit 35 drives the diaphragm 19 in accordance with the diaphragm drive signal from the lens control circuit 33.

  Based on the AF command transmitted from the MPU 30, the lens control circuit 33 calculates the target movement amount of the focus lens 3a for moving the focus lens 3a from the current position to the in-focus position, and obtains information on the target movement amount. Output to the focus adjustment circuit 34. Accordingly, as described above, the focus adjustment circuit 34 drives the focus motor 15 (not shown) and moves the focus lens 3a to the in-focus position. In this way, the phase difference AF is performed by controlling the position of the focus lens 3a based on the focus detection result by the phase difference detection method.

  The photometry circuit 37 outputs the luminance signal from the RGB photometry sensor 13 to the MPU 30. The MPU 30 performs A / D conversion of the luminance signal to obtain photometric information of the subject, and uses this photometric information to calculate and set the photographic exposure. A series of operations from obtaining this photometric information to setting the photographic exposure is called an AE operation. Similarly, subject color information is obtained from the RGB signals, and face detection is performed from the imaging signals.

  The motor drive circuit 38 controls a mirror motor (not shown) that drives the main mirror 4 and a charge motor (not shown) that charges the shutter 5. The shutter drive circuit 39 controls power supply to an electromagnet (coil) (not shown) that holds the shutter 5 in a charged state.

  The liquid crystal drive circuit 40 controls the drive of the PN liquid crystal panel 12 and displays AF frames and various information in the viewfinder. The DC / DC converter 41 converts the voltage of the power source (battery) 42 into a voltage necessary for each circuit in the camera body 1 and the interchangeable lens 3. The power source 42 is detachable from the camera body 1.

  The release button 43 is an operation member that is operated to start shooting by the user. When the release button 43 is half-pressed (first stroke operation), the first switch SW1 for starting shooting preparation operations such as AE and AF is turned on. That is, the focus adjustment (for recording image recording) is instructed by half-pressing the release button 43. Further, the second switch SW2 for starting the exposure of the image sensor 6 for generating the recording image is turned on by the full pressing operation (second stroke operation) of the release button 43. The ON signals of the first switch SW1 and the second switch SW2 are output to the MPU 30.

  The mode button 44 is operated together with an electronic dial 45 to be described later, so that the shooting mode in the camera body 1 can be changed. In the electronic dial 45, a click signal corresponding to the rotation operation amount is counted by an up / down counter in the MPU 30, and various numerical values and data are selected according to the count value.

  The multi-control button 46 is an operation input unit for selecting or setting the details of the AF frame and various shooting modes by the user operating the up, down, left, and right and eight button units provided therebetween.

  The SET button 47 is selected or set when the mode button 44, the electronic dial 45, the multi-control button 46, or the like is operated to select or set the details of the AF frame, various shooting modes, or various numerical values. It is an operation input part for determining. When the power button 48 is operated by the user, the power of the camera body 1 (and the interchangeable lens 3) is turned on / off. The AF lock button 49 starts shooting preparation operations such as AE and AF, in the same manner as the half-press operation of the release button 43.

  A CDS (correlated double sampling) / AGC (automatic gain adjustment) circuit 50 performs sample hold and automatic gain adjustment on the imaging signal output from the imaging device 6. The A / D converter 51 converts the analog output from the CDS / AGC circuit 50 into a digital signal. A TG (timing generation) circuit 52 supplies a drive timing signal to the image sensor 6, a sample hold timing signal to the CDS / AGC circuit 50, and a sample clock signal to the A / D converter 51. The memory controller 31 detects the defocus amount by the imaging surface phase difference detection method using the output signal from the focus detection pixel of the image sensor 6. Based on this defocus amount, the MPU 30 transmits a drive command for the focus lens 3 a to the lens control circuit 33.

  The SDRAM 53 as a memory temporarily records data such as images digitally converted by the A / D converter 51 and output signals of focus detection pixels of the image sensor 6. The image processing circuit 54 performs various processes such as Y / C (luminance signal / color difference signal) separation, white balance correction, and γ correction on the imaging signal (digital signal) output from the A / D converter 51. To generate image data for live view or recording. The memory controller 31 can obtain photometric information of the subject (perform so-called imaging surface AE) from the image data generated by the image processing circuit 54.

  The image compression / decompression circuit 55 compresses the image data according to a format such as JPEG or decompresses the compressed image data. The D / A converter 56 converts the image data into an analog signal in order to display the image data recorded on the SDRAM 53 or the recording medium 58 on the liquid crystal monitor 14. An I / F (interface) 57 is an interface with the recording medium 58.

  Next, the flow of focus adjustment control in the present embodiment will be described using the flowchart shown in FIG. The process shown in FIG. 4 is executed by the MPU 30 and the memory controller 31, which are computers, according to a computer program.

  The process of FIG. 4 is started with the main mirror 4 in the down position. In step S <b> 401, the MPU 30 determines whether SW <b> 1 is turned on by a half-press operation of the release button 43. If SW1 is not turned on, the process returns to step S401 to enter a standby state. If SW1 is turned on, the process proceeds to step S402.

  In step S <b> 402, the memory controller 31 acquires a prediction amount P <b> 1 that is an image shift amount detected by the focus detection circuit 36. In step S403, the memory controller 31 calculates the defocus amount D1 based on the prediction amount P1 acquired in step S402.

  In step S404, the MPU 30 determines whether or not the defocus amount D1 is smaller than the threshold value A (second threshold value). The threshold A moves to the in-focus position where the main mirror 4 is in the up position with a small driving amount even if the amount of image plane movement that occurs when the main mirror 4 is moved from the down position to the up position is taken into account. This is a possible value and is defined by the defocus amount. By providing the comparison determination with the threshold A, even if it is determined that the error influence of the coefficient K, which will be described later, is large, the main mirror 4 is in the down position if it is far away from the in-focus position. In this state, focus detection is performed to control driving of the focus lens 3a. When the defocus amount D1 is smaller than the threshold A, the process proceeds to step S405, and when the defocus amount D1 is equal to or greater than the threshold A (second threshold or greater), the process proceeds to step S416.

  In step S405, the MPU 30 determines whether or not the error influence degree of the coefficient K is larger than the threshold value C (first threshold value). When the error influence degree of the coefficient K is larger than the threshold value C, the process proceeds to step S406, and when it is equal to or less than the threshold value C (below the first threshold value), the process proceeds to step S416.

The coefficient K (K value) is a coefficient for converting the prediction amount P into the movement amount of the focus lens 3a, and the defocus amount D is obtained by the following equation.
D = P × K

  The coefficient K has a representative value of each condition in the camera as a table according to each condition. However, an error occurs in the offset amount because the coefficient K uses the representative value of each condition when focusing on the offset position by mirror transmission. When an offset amount including an error is applied, there are the following problems. If the focus lens 3a is moved to the in-focus position with the main mirror 4 in the down position and the main mirror 4 is in the up position, then the main mirror 4 is moved to the up position and imaging is performed. This leads to a decrease in hunting and final focusing accuracy.

  In this embodiment, the magnitude of the influence of the error of the coefficient K is determined based on the magnitude of the coefficient K with respect to the above problem. If the coefficient K is larger than the threshold value C in step S405, the process proceeds to step S406, the main mirror 4 is moved to the up position, and focus detection and focus adjustment operations are performed in step S407 and later described later. Thereby, accurate focus adjustment can be performed regardless of the accuracy of the coefficient K. The threshold C is a value determined by each parameter such as image height, open F value, Po value (mirror length).

  If the coefficient K is less than or equal to the threshold C, it is assumed that there is little decrease in focusing accuracy due to the error of the coefficient K, and the process proceeds to step S416. In this case, as will be described later, the MPU 30 performs focus detection and drive control of the focus lens 3a based on information transmitted through the main mirror 4 while the main mirror 4 is in the down position.

  In step S407, the memory controller 31 obtains the prediction amount P2 after the main mirror 4 has moved to the up position. In step S408, the memory controller 31 calculates the defocus amount D2 when the mirror is raised based on the prediction amount P2. In step S409, the MPU 30 determines whether or not the defocus amount D2 is within the in-focus range. When the defocus amount D2 is within the in-focus range, the process proceeds to step S410, and when not within the in-focus range, the process proceeds to step S417. In step S417, the MPU 30 moves the focus lens 3a so as to approach the in-focus position, and performs the processing from step S407 again. In step S410, the MPU 30 moves the main mirror 4 to the down position and advances the process to step S411.

  On the other hand, when the process proceeds to step S416 due to the determination in either step S404 or step S405, the MPU 30 determines whether the defocus amount D1 calculated in step S403 is within the in-focus range. If the defocus amount D1 is within the in-focus range, the process proceeds to step S411, and if not within the in-focus range, the process proceeds to step S415. In step S415, the MPU 30 moves the focus lens 3a so as to approach the in-focus position, and performs the processing from step S402 again.

  As described above, in step S404, a comparison determination between the defocus amount D1 and the threshold A is performed. As a result, even if it is determined that the degree of error influence of the coefficient K is large, focus detection is performed in a state where the main mirror 4 is in the down position if the distance from the in-focus position is some extent, and the focus lens 3a Control the position. When the focus is greatly blurred, the waveform of the image signal used for focus detection tends to collapse, and it is difficult to obtain a highly accurate defocus amount in the first place. Therefore, when the focus is greatly blurred, focus detection is performed with the main mirror 4 down, and the focus detection is performed by moving the main mirror 4 up after approaching the in-focus position. Can be prevented.

  Note that the offset amount when the main mirror 4 is in the down position and the up position is the design value of the camera body, and the defocus amount D1 detected in the down position in step S403 is offset to obtain the offset amount in the up position. A defocus amount is calculated. The determination in step S416 as to whether or not it is within the focusing range is made based on the defocus amount offset to the state where the main mirror 4 is in the up position. In the lens driving in step S415, the focus lens 3a is driven so as to approach the in-focus position offset to the state where the main mirror 4 is in the up position.

  As described above, when it is determined that the influence of the coefficient K is small in the process of step S405, based on the defocus amount at the up position obtained by offsetting the defocus amount detected at the down position. The focus adjustment operations in steps S416 and S415 are performed. Thereby, when it is determined in step S416 that it is within the focusing range, the subject image is focused on the image sensor 6 when the main mirror 4 is raised in step S412 described later.

  In step S <b> 411, the MPU 30 determines whether SW <b> 2 is turned on by a full pressing operation of the release button 43. If SW2 is not turned on, the imaging apparatus enters a standby state. If SW2 is turned on, the process proceeds to step S412.

  In step S412, the MPU 30 moves the main mirror 4 to the up position. In step S413, an exposure operation is performed. After that, in step S414, the main mirror 4 is moved to the down position, and the process ends.

  As described above, in the present embodiment, the focal point based on the light flux that has been transmitted through the main mirror 4 and incident is determined by determining the influence of the error of the conversion coefficient for converting the image shift amount into the defocus amount. It is determined whether or not the detection accuracy is high. When the influence of the error of the conversion coefficient is large, in focus adjustment before SW2 is turned on, focus detection is performed with the main mirror 4 moved to the up position, and focus lens drive control is performed. . Thereby, in consideration of the influence of the error of the conversion coefficient, it is possible to reduce the focus shift accompanying the change in the insertion state of the half mirror in the optical path.

(Second Embodiment)
In the first embodiment, the method of determining the influence degree of the error of the coefficient K from the magnitude of the coefficient K has been described. On the other hand, in the second embodiment, the error influence degree of the coefficient K is determined based on information acquired from the lens. Below, it demonstrates centering around the difference with 1st Embodiment, and abbreviate | omits description about the content which is common in 1st Embodiment. FIG. 8 is a flowchart showing the flow of focus adjustment control in the present embodiment.

  The processes in steps S801 to S804 are the same as those in FIG. 4 and steps S401 to S404, and thus the description thereof is omitted. If the defocus amount D1 is smaller than the threshold value A in step S804, the process proceeds to step S805.

  In step S805, the MPU 30 determines the degree of influence of the coefficient error based on the lens information. In the present embodiment, the magnitude of the influence of the error of the coefficient K is determined based on information acquired from the interchangeable lens 3 such as information stored in the lens in advance or the type of lens. For example, the determination may be made based on the identification information of the interchangeable lens 3 transmitted from the interchangeable lens 3 in the initial communication performed when the power of the camera body 1 is turned on. The MPU 30 determines whether or not the error influence degree of the coefficient K affects the focusing accuracy based on the information acquired from the interchangeable lens 3. If it is determined that the error influence degree of the coefficient K is large, the process proceeds to step S806, and if it is determined that the error influence degree of the coefficient K is small, the process proceeds to step S816.

  The processing after step S806 is the same as the processing after step S406 in FIG.

  With the above configuration, also in this embodiment, it is possible to reduce the focus shift caused by the change in the insertion state of the half mirror in the optical path in consideration of the influence of the error due to the K value.

(Third embodiment)
In the first embodiment and the second embodiment described above, when the influence of the error of the coefficient K is large, the main mirror 4 is raised in the focus adjustment operation before shooting is instructed (before SW2 ON). Focus detection was performed. In this case, since the finder disappears when the main mirror 4 is raised, there is a risk of inconvenience for a user who takes a picture while observing the finder.

  Therefore, as an alternative means, it is assumed that the focus adjustment operation is performed with the main mirror 4 kept down before SW2 ON, and the main mirror 4 is raised and the focus adjustment operation is performed again after SW2 is turned ON. . Thereby, it is possible to prevent the focus detection accuracy from being lowered due to the error of the coefficient K while preventing the occurrence of the finder disappearance time until the user confirms the composition and turns on SW2. However, in the case of so-called place pin shooting, where the composition is changed after focusing once on the intended position, the focus is adjusted in advance if the focus adjustment operation is performed again after the shooting is instructed. There is a possibility of being out of focus from the position.

  Therefore, in the third embodiment, in accordance with the difference in operation for instructing focus adjustment, the focus control operation is completed by raising the main mirror 4 and performing focus adjustment before SW2 ON, or after SW2 ON. Change the focus adjustment operation with. As an example, when the focus adjustment is instructed by the AF lock button 49 that is often used during shooting with a setting pin, the focus control is completed by raising the main mirror 4 and performing the focus adjustment operation before SW2 ON. Let On the other hand, when the focus adjustment is instructed by the release button 43, the focus adjustment operation is performed with the main mirror 4 kept down before the SW2 ON to prevent the occurrence of the finder disappearance time. , And adjust the focus again.

  FIG. 9 is a flowchart showing a flow of focus adjustment control in the present embodiment. Although FIG. 9 illustrates a case where the influence degree of the error of the coefficient K is determined by the same method as in the first embodiment, the determination method of the second embodiment may be applied.

  First, in step S9001, the MPU 30 resets the flag to 0. This flag stores which of the AF lock button 49 and the release button 43 has started the focus adjustment operation.

  In step S <b> 901, the MPU 30 determines whether SW <b> 1 is turned on by a half-press operation of the release button 43. If SW1 is not turned on, the process proceeds to step S9002, and it is determined whether the AF lock button 49, which is another focus adjustment instruction member, has been turned on. If the AF lock button 49 is not turned on, the process returns to step S901 to enter a standby state. On the other hand, if the AF lock button is ON, the process proceeds to step S9003 and the above-described flag is set to 1. If SW1 or the AF lock button is turned on, the process proceeds to step S902. The processing in steps S902 and S903 is the same as the processing in steps S403 and S403 in FIG.

  In step S9004, the MPU 30 determines whether the flag is 1. That is, it is determined whether the focus adjustment operation is instructed via the AF lock button 49 or the release button 43. If the flag is not 1 (instructed by the release button 43), the process proceeds to step S916, the same processing as steps S416 and S415 in FIG. 4 is performed, and if the defocus amount D1 is determined to be within the in-focus range, step is performed. The process proceeds to S911.

  On the other hand, if the flag is 1 (when instructed by the AF lock button 49), the process proceeds to step S904. The processing in steps S904 to S912 is the same as the processing in steps S404 to S412 in FIG. When SW2 is turned ON in step S911 and the main mirror 4 is moved to the up position in step S912, the process proceeds to step S9005.

  In step S9005, the MPU 30 determines whether the flag is 1. That is, it is determined whether the focus adjustment operation is instructed via the AF lock button 49 or the release button 43. If the flag is not 1 (when instructed by the release button 43), the process proceeds to step S9006. If the flag is 1 (instructed by the AF lock button 49), the process proceeds to step S913. The processes in steps S913 and S914 are the same as the processes in steps S413 and S414 in FIG.

  In step S9006, the memory controller 31 obtains the prediction amount P3 after the main mirror 4 has moved to the up position. In subsequent step S9007, the memory controller 31 calculates a defocus amount D3 based on the prediction amount P3 acquired in step S9006, and the process proceeds to step S9008.

  In step S9008, the MPU 30 determines whether or not the defocus amount D3 is within the focusing range. If the defocus amount D3 is within the in-focus range, the process proceeds to step S913. On the other hand, if it is not within the in-focus range, the process proceeds to step S9009, and the MPU 30 moves the focus lens 3a so as to approach the in-focus position, and performs the processing from step S906 again.

  It should be noted that between steps S9005 and S9006, a process for determining the error influence degree of the coefficient K is performed in the same manner as in step S905, and if it is determined that the error influence degree of the coefficient K is large, the process may proceed to step S9006. . In this case, if it is determined that the degree of error influence of the coefficient K is small, the focus adjustment operation is not performed again, and the exposure operation in step S913 may be performed. As a result, it is possible to prevent an unnecessarily long time lag from when SW2 is turned on until shooting.

  As described above, in the present embodiment, when focus adjustment is instructed by the release button 43, the main mirror 4 is lowered before the switch SW2 is turned on even under the condition that the influence of the coefficient K error is large. The focus adjustment operation is performed with the state kept (steps S915 and S916). Then, when SW2 is turned on, the focus adjustment operation is performed again immediately before exposure (steps S9006 to S9009), thereby taking a focused image while preventing a decrease in focus detection accuracy due to the influence of the coefficient K error. can do. In this case, the time lag from when SW2 is turned on to when the image is taken is relatively long. In this embodiment, by changing the control according to the difference in the method of instructing the focus adjustment, there is an advantage in that the user can select whether to prioritize prevention of finder disappearance before SW2 ON or time lag reduction after SW2 ON. is there. In addition, when placing-pin shooting is performed, by instructing focus adjustment with the AF lock button 49, it is possible to perform shooting while keeping the focus at the intended position.

  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.

4 Main mirror 6 Image sensor 30 MPU
31 Memory controller 36 Focus detection circuit

Claims (18)

It can move between a first position inserted in the optical path of the light beam that has passed through the photographing optical system and a second position retracted from the optical path, and transmits a part of the incident light beam and reflects a part of it. An optical member,
Imaging means for receiving and photoelectrically converting a light beam that has passed through the photographing optical system;
A focus detection unit that acquires an image shift amount based on a signal output from the imaging unit and detects a defocus amount from the image shift amount using a conversion coefficient;
Control means for controlling focus adjustment based on the defocus amount,
The control means controls the focus adjustment based on a signal output from the imaging means in a state where the optical member is at the first position according to the conversion factor, and the optical member An image pickup apparatus characterized by switching a second mode for controlling focus adjustment based on a signal output from the image pickup means in a state where is in the second position.   The imaging apparatus according to claim 1, wherein the control unit controls focus adjustment in the second mode when the conversion coefficient is larger than a first threshold.   The imaging apparatus according to claim 2, wherein the control unit controls focus adjustment in the first mode when the conversion coefficient is equal to or less than the first threshold value.   4. The control unit according to claim 1, wherein the control unit controls the focus adjustment in the first mode regardless of the conversion factor when the defocus amount is equal to or greater than a second threshold value. 5. The imaging apparatus according to item 1.   In the first mode, the control means indicates a defocus amount detected by the focus detection means in a state where the optical member is in the first position, and indicates that the optical member is in the second position. 5. The imaging apparatus according to claim 1, wherein the imaging apparatus is offset to the defocus amount detected in step (b) and the focus adjustment is controlled based on the offset defocus amount.   The optical member is moved to the first position until photographing is instructed when the defocus amount is within a focusing range by performing focus adjustment in the second mode. The imaging device according to any one of 1 to 5. A first member for instructing focus adjustment;
When the focus adjustment is instructed by the first member, the control means controls the focus adjustment by switching between the first mode and the second mode according to the conversion factor. The imaging device according to any one of claims 1 to 6. A member for instructing focus adjustment, the second member being different from the first member;
When focus adjustment is instructed by the second member, the control means controls focus adjustment in the first mode before instructing photographing, and exposure to the imaging means is instructed after photographing is instructed. The imaging apparatus according to claim 7, wherein focus adjustment is controlled in the second mode until.   When focus adjustment is instructed by the second member, the control unit determines whether or not to perform focus adjustment between the time when imaging is instructed and the time when the imaging unit is exposed according to the conversion factor. The imaging apparatus according to claim 8, wherein the imaging apparatus is switched.   The finder for observing a subject image by a light beam reflected by the optical member in a state where the optical member is at the first position. Imaging device. An imaging device in which an interchangeable lens equipped with a photographing optical system is detachable,
It is possible to move between a first position inserted in the optical path of the light beam that has passed through the photographing optical system and a second position retracted from the optical path. A reflecting optical member;
Imaging means for receiving and photoelectrically converting a light beam that has passed through the photographing optical system;
A focus detection unit that acquires an image shift amount based on a signal output from the imaging unit and detects a defocus amount from the image shift amount using a conversion coefficient;
Control means for controlling focus adjustment based on the defocus amount;
Obtaining means for obtaining lens information from the interchangeable lens;
The control means controls the focus adjustment based on a signal output from the imaging means in a state where the optical member is in the first position according to the lens information; and the optical member An image pickup apparatus characterized by switching a second mode for controlling focus adjustment based on a signal output from the image pickup means in a state where is in the second position.   When the lens information indicates the first lens, the control unit controls focus adjustment in the first mode, and the lens information is more influenced by the error of the conversion coefficient than the first lens. The imaging apparatus according to claim 11, wherein the control unit controls focus adjustment in the second mode when the second lens indicates that the second lens is a large second lens.   13. The control unit according to claim 11, wherein the control unit controls focus adjustment in the first mode regardless of the lens information when the defocus amount is equal to or greater than a second threshold value. Imaging device.   In the first mode, the control means indicates a defocus amount detected by the focus detection means in a state where the optical member is in the first position, and indicates that the optical member is in the second position. The imaging apparatus according to claim 11, wherein the imaging apparatus is offset to the defocus amount detected in step (b) and the focus adjustment is controlled based on the offset defocus amount.   The optical member is moved to the first position until photographing is instructed when focus adjustment is performed in the second mode and the defocus amount falls within a focusing range. 15. The imaging device according to any one of 1 to 14.   The finder for observing a subject image by a light beam reflected by the optical member in a state where the optical member is at the first position. Imaging device. An optical system that can move between a first position inserted in the optical path of a light beam that has passed through the photographing optical system and a second position that is retracted from the optical path, and that transmits a part of the incident light beam and reflects a part thereof. A method for controlling an image pickup apparatus including a member and an image pickup unit that receives and photoelectrically converts a light beam that has passed through the photographing optical system,
Obtaining an image shift amount based on a signal output from the imaging means;
Detecting a defocus amount from the image shift amount using a conversion coefficient;
Controlling the focus adjustment based on the defocus amount,
In accordance with the conversion factor, a first mode for controlling focus adjustment based on a signal output from the imaging means in a state where the optical member is at the first position, and the optical member is the second mode. A control method for an image pickup apparatus, wherein a second mode for controlling focus adjustment is switched based on a signal output from the image pickup means in a position. An image pickup apparatus in which an interchangeable lens having a photographing optical system is detachable, and moves to a first position inserted in an optical path of a light beam passing through the photographing optical system and a second position retracted from the optical path A method for controlling an imaging apparatus comprising: an optical member capable of transmitting a part of an incident light beam and reflecting a part thereof; and an imaging unit that receives and photoelectrically converts the light beam that has passed through the photographing optical system. ,
Obtaining an image shift amount based on a signal output from the imaging means;
Detecting a defocus amount from the image shift amount using a conversion coefficient;
Controlling focus adjustment based on the defocus amount;
Obtaining lens information from the interchangeable lens,
In accordance with the lens information, a first mode for controlling focus adjustment based on a signal output from the imaging means in a state where the optical member is at the first position, and the optical member is the second mode. A control method for an image pickup apparatus, wherein a second mode for controlling focus adjustment is switched based on a signal output from the image pickup means in a position.

Images