JP5961979B2 - Focus adjustment device and imaging device - Google Patents

Description

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

  2. Description of the Related Art Conventionally, a technique for detecting a focus state of an optical system by calculating an evaluation value related to contrast by the optical system while driving a focus adjustment lens in the optical axis direction is known (see, for example, Patent Document 1). .

JP 2010-139666 A

  However, since the conventional technique is to drive the focus adjustment lens at a predetermined speed in order to detect the focus state of the optical system, the focus adjustment lens is used when shooting using a lens barrel for close-up photography. As the aperture value of the optical system changes with the movement in the optical axis direction, and the depth of field changes thereby, even when the focus adjustment lens is driven at a predetermined speed, As the depth of field changes, the driving speed of the focus adjustment lens may become faster than the speed suitable for focus detection or slower than the speed suitable for focus detection. In some cases, the focus state of the system could not be detected properly.

  The problem to be solved by the present invention is to provide a focus adjustment device that can appropriately detect the focus state of an optical system.

  The present invention solves the above problems by the following means. In the following description, reference numerals corresponding to the drawings showing the embodiment of the present invention are given and described. However, the reference numerals are only for facilitating the understanding of the invention and are not intended to limit the invention. .

[1] The focus adjustment apparatus according to the first aspect of the present invention calculates the evaluation value related to the contrast of the image by the optical system while driving the focus adjustment lens in the optical axis direction by the drive unit, thereby the optical system. a focus detection unit for detecting the focus state of the open aperture value when position that put in the optical axis direction of the focusing lens is a first position, and, that put in the optical axis direction of the focusing lens position of open aperture value when location is a second position different from the first position, a first obtaining unit that retrieve and the smaller the predetermined open aperture value, a second acquisition unit for acquiring the current aperture number And the aperture value when the focus adjustment lens is moved to the lens position corresponding to the predetermined aperture value with the current aperture level based on the predetermined aperture value and the current aperture level. A calculation unit for calculating the value, and the drive While the by driving the focusing lens to the part, and a control unit to perform the detection of the focusing state of the optical system in the focus detection unit, wherein the control unit, on the basis of the predetermined stop value, the focus detection part is to determine the driving speed of said focusing lens when the detection of focus state of the optical system.

[ 2 ] In the focus adjusting apparatus according to the second aspect of the present invention, the first value which is an open aperture value when the position of the focus lens is the first position, and the position of the focus lens is the first position. An acquisition unit that acquires a smaller one of the second values that are the full aperture value when the second position is different from the position, and the current aperture stage number, the first value, and the second value Using the smaller value of the values and the current number of apertures, the current aperture position at the position of the focus lens where the maximum aperture value is the smaller of the first value and the second value. A calculation unit that calculates a third value that is an aperture value when the number of aperture stages is set, and the focus at a speed determined using the third value when the focus lens is detected by moving the focus lens And a control unit that performs control to move the lens .

  According to the present invention, it is possible to appropriately detect the focus state of the optical system.

FIG. 1 is a block diagram showing a camera according to the present embodiment. FIG. 2 is a front view showing an imaging surface of the imaging device shown in FIG. FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the III part of FIG. FIG. 4 is an enlarged front view showing one of the imaging pixels 221. FIG. 5A is an enlarged front view showing one of the focus detection pixels 222a, and FIG. 5B is an enlarged front view showing one of the focus detection pixels 222b. FIG. 6 is an enlarged cross-sectional view showing one of the imaging pixels 221. FIG. 7A is an enlarged cross-sectional view showing one of the focus detection pixels 222a, and FIG. 7B is an enlarged cross-sectional view showing one of the focus detection pixels 222b. 8 is a cross-sectional view taken along line VIII-VIII in FIG. FIG. 9 is a flowchart showing the operation of the camera according to the present embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a main part configuration diagram showing a digital camera 1 according to the present embodiment. A digital camera 1 according to the present embodiment (hereinafter simply referred to as a camera 1) includes a camera body 2 and a lens barrel 3, and the camera body 2 and the lens barrel 3 are detachably coupled by a mount unit 4. Yes.

  The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. As shown in FIG. 1, the lens barrel 3 includes a photographic optical system including lenses 31, 32, 33 and a diaphragm 34.

  The lens 32 is a focus lens, and can adjust the focal length of the photographing optical system by moving in the direction of the optical axis L1. The focus lens 32 is provided so as to be movable along the optical axis L1 of the lens barrel 3, and its position is adjusted by the focus lens drive motor 36 while its position is detected by the encoder 35.

  The specific configuration of the moving mechanism along the optical axis L1 of the focus lens 32 is not particularly limited. For example, a rotating cylinder is rotatably inserted into a fixed cylinder fixed to the lens barrel 3, a helicoid groove (spiral groove) is formed on the inner peripheral surface of the rotating cylinder, and the focus lens 32 is fixed. The end of the lens frame is fitted into the helicoid groove. Then, by rotating the rotating cylinder by the focus lens drive motor 36, the focus lens 32 fixed to the lens frame moves straight along the optical axis L1.

  As described above, the focus lens 32 fixed to the lens frame by rotating the rotary cylinder with respect to the lens barrel 3 moves straight in the direction of the optical axis L1, but the focus lens drive motor 36 as the drive source is the lens. The lens barrel 3 is provided. The focus lens drive motor 36 and the rotary cylinder are connected by a transmission composed of a plurality of gears, for example, and when the drive shaft of the focus lens drive motor 36 is driven to rotate in any one direction, it is transmitted to the rotary cylinder at a predetermined gear ratio. Then, when the rotating cylinder rotates in any one direction, the focus lens 32 fixed to the lens frame moves linearly in any direction of the optical axis L1. When the drive shaft of the focus lens drive motor 36 is rotated in the reverse direction, the plurality of gears constituting the transmission also rotate in the reverse direction, and the focus lens 32 moves straight in the reverse direction of the optical axis L1. .

  The position of the focus lens 32 is detected by the encoder 35. As described above, the position of the focus lens 32 in the optical axis L1 direction correlates with the rotation angle of the rotating cylinder, and can be obtained by detecting the relative rotation angle of the rotating cylinder with respect to the lens barrel 3, for example.

  As the encoder 35 of this embodiment, an encoder that detects the rotation of a rotating disk coupled to the rotational drive of the rotating cylinder with an optical sensor such as a photo interrupter and outputs a pulse signal corresponding to the number of rotations, or a fixed cylinder And the contact point of the brush on the surface of the flexible printed wiring board provided on either one of the rotating cylinders, and the brush contact provided on the other, the amount of movement of the rotating cylinder (in either the rotational direction or the optical axis direction) A device that detects a change in the contact position according to the detection circuit using a detection circuit can be used.

  The focus lens 32 can move in the direction of the optical axis L1 from the end on the camera body side (also referred to as the closest end) to the end on the subject side (also referred to as the infinite end) by the rotation of the rotating cylinder described above. it can. Incidentally, the current position information of the focus lens 32 detected by the encoder 35 is sent to the camera control unit 21 to be described later via the lens control unit 37, and the focus lens drive motor 36 calculates the focus calculated based on this information. The driving position of the lens 32 is driven by being sent from the camera control unit 21 via the lens control unit 37.

  The diaphragm 34 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light flux that passes through the photographing optical system and reaches the image sensor 22 and to adjust the blur amount. The adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 37 by a manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the aperture 34 is detected by an aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

  In the present embodiment, a close-up microlens (close-up lens) is used as the lens barrel 3. A micro lens (lens for close-up) has a short minimum shooting distance and a minimum shooting distance of, for example, 200 mm or less (for example, 105 mm) as compared with a normal lens barrel. Further, in the microlens, the open aperture value changes as the focus lens 32 moves in the optical axis direction. For example, the open aperture value is F4 at the closest focus lens position, but at infinity. The open aperture value may be F2.8 at the focus lens position on the side. In this way, the lens control unit 37 stores the minimum aperture value among the plurality of aperture values for each lens position in the optical axis direction of the focus lens 32 as a minimum aperture value in a memory included in the lens control unit 37. The minimum aperture value is stored and transmitted to the camera control unit 21. In this embodiment, a microlens whose aperture value changes as the focus lens 32 moves in the optical axis direction is used as the lens barrel 3, but the lens barrel 3 is the focus lens 32. As long as the aperture value changes as the lens moves in the optical axis direction, the microlens for close-up photography is not particularly limited.

  On the other hand, the camera body 2 is provided with an imaging element 22 that receives the light beam L1 from the photographing optical system on a planned focal plane of the photographing optical system, and a shutter 23 is provided on the front surface thereof. The image sensor 22 is composed of a device such as a CCD or CMOS, converts the received optical signal into an electrical signal, and sends it to the camera control unit 21. The captured image information sent to the camera control unit 21 is sequentially sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder (EVF) 26 of the observation optical system, and a release button ( When (not shown) is fully pressed, the photographed image information is recorded in the camera memory 24 which is a recording medium. The camera memory 24 can be either a removable card type memory or a built-in memory. Details of the structure of the image sensor 22 will be described later.

  The camera body 2 is provided with an observation optical system for observing an image picked up by the image pickup device 22. The observation optical system of the present embodiment includes an electronic viewfinder (EVF) 26 composed of a liquid crystal display element, a liquid crystal driving circuit 25 that drives the electronic viewfinder (EVF) 26, and an eyepiece lens 27. The liquid crystal drive circuit 25 reads the captured image information captured by the image sensor 22 and sent to the camera control unit 21, and drives the electronic viewfinder 26 based on the read image information. Thereby, the user can observe the current captured image through the eyepiece lens 27. Note that, instead of or in addition to the observation optical system using the optical axis L2, a liquid crystal display may be provided on the back surface of the camera body 2, and a photographed image may be displayed on the liquid crystal display.

  The camera body 2 is provided with a camera control unit 21. The camera control unit 21 is electrically connected to the lens control unit 37 through an electrical signal contact unit 41 provided on the mount unit 4, receives lens information from the lens control unit 37, and receives data from the lens control unit 37. Information such as the focus amount and aperture diameter is transmitted. The camera control unit 21 reads out the pixel output from the image sensor 22 as described above, generates image information by performing predetermined information processing on the read out pixel output as necessary, and generates the generated image information. Is output to the liquid crystal driving circuit 25 and the memory 24 of the electronic viewfinder 26. The camera control unit 21 controls the entire camera 1 such as correction of image information from the image sensor 22 and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 3.

  In addition to the above, the camera control unit 21 detects the focus state of the photographic optical system by the phase detection method and the focus state of the photographic optical system by the contrast detection method based on the pixel data read from the image sensor 22. I do. A specific focus state detection method will be described later.

  The operation unit 28 is an input switch for a photographer to set various operation modes of the camera 1, such as a shutter release button, and can switch between an auto focus mode and a manual focus mode. Various modes set by the operation unit 28 are sent to the camera control unit 21, and the operation of the entire camera 1 is controlled by the camera control unit 21. The shutter release button includes a first switch SW1 that is turned on when the button is half-pressed and a second switch SW2 that is turned on when the button is fully pressed.

  Next, the image sensor 22 according to the present embodiment will be described.

  FIG. 2 is a front view showing the imaging surface of the imaging device 22, and FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the III part of FIG.

  As shown in FIG. 3, the imaging element 22 of the present embodiment includes a green pixel G having a color filter in which a plurality of imaging pixels 221 are two-dimensionally arranged on the plane of the imaging surface and transmit a green wavelength region. A red pixel R having a color filter that transmits a red wavelength region and a blue pixel B having a color filter that transmits a blue wavelength region are arranged in a so-called Bayer Arrangement. That is, in four adjacent pixel groups 223 (dense square lattice arrangement), two green pixels are arranged on one diagonal line, and one red pixel and one blue pixel are arranged on the other diagonal line. The image sensor 22 is configured by repeatedly arranging the pixel group 223 on the imaging surface of the image sensor 22 in a two-dimensional manner with the Bayer array pixel group 223 as a unit.

  The unit pixel group 223 may be arranged in a dense hexagonal lattice arrangement other than the dense square lattice shown in the figure. Further, the configuration and arrangement of the color filters are not limited to this, and an arrangement of complementary color filters (green: G, yellow: Ye, magenta: Mg, cyan: Cy) can also be adopted.

  FIG. 4 is an enlarged front view showing one of the imaging pixels 221, and FIG. 6 is a cross-sectional view. One imaging pixel 221 includes a micro lens 2211, a photoelectric conversion unit 2212, and a color filter (not shown), and a photoelectric conversion unit is formed on the surface of the semiconductor circuit substrate 2213 of the image sensor 22 as shown in the cross-sectional view of FIG. 2212 is built in and a microlens 2211 is formed on the surface. The photoelectric conversion unit 2212 is configured to receive an imaging light beam that passes through an exit pupil (for example, F1.0) of the photographing optical system by the micro lens 2211, and receives the imaging light beam.

  In addition, focus detection pixel rows 22a, 22b, and 22c in which focus detection pixels 222a and 222b are arranged in place of the above-described imaging pixels 221 at the center of the image pickup surface of the image pickup element 22 and three positions that are symmetrical from the center. Is provided. As shown in FIG. 3, one focus detection pixel column includes a plurality of focus detection pixels 222 a and 222 b that are alternately arranged adjacent to each other in a horizontal row (22 a, 22 c, 22 c). Yes. In the present embodiment, the focus detection pixels 222a and 222b are densely arranged without providing a gap at the position of the green pixel G and the blue pixel B of the image pickup pixel 221 arranged in the Bayer array.

  Note that the positions of the focus detection pixel rows 22a to 22c shown in FIG. 2 are not limited to the illustrated positions, and may be any one or two, or may be arranged at four or more positions. it can. In actual focus detection, a photographer manually operates the operation unit 28 from among a plurality of focus detection pixel rows 22a to 22c, and selects a desired focus detection pixel row as a focus detection area. You can also

  FIG. 5A is an enlarged front view showing one of the focus detection pixels 222a, and FIG. 7A is a cross-sectional view of the focus detection pixel 222a. FIG. 5B is an enlarged front view showing one of the focus detection pixels 222b, and FIG. 7B is a cross-sectional view of the focus detection pixel 222b. As shown in FIG. 5A, the focus detection pixel 222a includes a micro lens 2221a and a semicircular photoelectric conversion unit 2222a. As shown in the cross-sectional view of FIG. A photoelectric conversion portion 2222a is formed on the surface of the semiconductor circuit substrate 2213, and a micro lens 2221a is formed on the surface. The focus detection pixel 222b includes a micro lens 2221b and a photoelectric conversion unit 2222b as shown in FIG. 5B, and a semiconductor of the image sensor 22 as shown in a cross-sectional view of FIG. 7B. A photoelectric conversion unit 2222b is formed on the surface of the circuit board 2213, and a microlens 2221b is formed on the surface. Then, as shown in FIG. 3, these focus detection pixels 222a and 222b are alternately arranged adjacent to each other in a horizontal row, thereby forming focus detection pixel rows 22a to 22c shown in FIG.

  The photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b have such a shape that the microlenses 2221a and 2221b receive a light beam that passes through a predetermined region (eg, F2.8) of the exit pupil of the photographing optical system. Is done. Further, the focus detection pixels 222a and 222b are not provided with color filters, and their spectral characteristics are the total of the spectral characteristics of a photodiode that performs photoelectric conversion and the spectral characteristics of an infrared cut filter (not shown). ing. However, it may be configured to include one of the same color filters as the imaging pixel 221, for example, a green filter.

  In addition, although the photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b illustrated in FIGS. 5A and 5B have a semicircular shape, the shapes of the photoelectric conversion units 2222a and 2222b are not limited thereto. Other shapes such as an elliptical shape, a rectangular shape, and a polygonal shape can also be used.

  Here, a so-called phase difference detection method for detecting the focus state of the photographing optical system based on the pixel outputs of the focus detection pixels 222a and 222b described above will be described.

  FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. 3. The focus detection pixels 222 a-1, 222 b-1, 222 a-2, and 222 b-2 that are arranged in the vicinity of the photographing optical axis L 1 and adjacent to each other are It shows that light beams AB1-1, AB2-1, AB1-2, and AB2-2 irradiated from the distance measuring pupils 351 and 352 of the exit pupil 350 are received. 8 illustrates only the focus detection pixels 222a and 222b that are located in the vicinity of the photographing optical axis L1, but other focus detection pixels other than the focus detection pixels illustrated in FIG. 8 are illustrated. In the same manner, the light beams emitted from the pair of distance measuring pupils 351 and 352 are respectively received.

  Here, the exit pupil 350 is an image set at a distance D in front of the microlenses 2221a and 2221b of the focus detection pixels 222a and 222b arranged on the planned focal plane of the photographing optical system. The distance D is a value uniquely determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion unit, and the distance D is referred to as a distance measurement pupil distance. The distance measurement pupils 351 and 352 are images of the photoelectric conversion units 2222a and 2222b respectively projected by the micro lenses 2221a and 2221b of the focus detection pixels 222a and 222b.

  In FIG. 8, the arrangement direction of the focus detection pixels 222a-1, 222b-1, 222a-2, 222b-2 coincides with the arrangement direction of the pair of distance measuring pupils 351, 352.

  As shown in FIG. 8, the microlenses 2221a-1, 2221b-1, 2221a-2, and 2221b-2 of the focus detection pixels 222a-1, 222b-1, 222a-2, and 222b-2 are photographic optical systems. Near the planned focal plane. The shapes of the photoelectric conversion units 2222a-1, 2222b-1, 2222a-2, 2222b-2 arranged behind the micro lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 are the same as the micro lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2. Projected onto the exit pupil 350 that is separated from the lenses 2221 a-1, 2221 b-1, 2221 a-2, and 2221 b-2 by a distance measurement distance D, and the projection shape forms distance measurement pupils 351 and 352.

  That is, the microlens and the photoelectric conversion unit in each focus detection pixel so that the projection shapes (distance measurement pupils 351 and 352) of the focus detection pixels coincide on the exit pupil 350 at the distance D. Is determined, and the projection direction of the photoelectric conversion unit in each focus detection pixel is thereby determined.

  As shown in FIG. 8, the photoelectric conversion unit 2222a-1 of the focus detection pixel 222a-1 is formed on the microlens 2221a-1 by the light beam AB1-1 that passes through the distance measuring pupil 351 and goes to the microlens 2221a-1. A signal corresponding to the intensity of the image to be output is output. Similarly, the photoelectric conversion unit 2222a-2 of the focus detection pixel 222a-2 passes through the distance measuring pupil 351, and the intensity of the image formed on the microlens 2221a-2 by the light beam AB1-2 toward the microlens 2221a-2. The signal corresponding to is output.

  Further, the photoelectric conversion unit 2222b-1 of the focus detection pixel 222b-1 passes through the distance measuring pupil 352, and the intensity of the image formed on the microlens 2221b-1 by the light beam AB2-1 directed to the microlens 2221b-1. Output the corresponding signal. Similarly, the photoelectric conversion unit 2222b-2 of the focus detection pixel 222b-2 passes through the distance measuring pupil 352, and the intensity of the image formed on the microlens 2221b-2 by the light beam AB2-2 toward the microlens 2221b-2. The signal corresponding to is output.

  Then, a plurality of the above-described two types of focus detection pixels 222a and 222b are arranged in a straight line as shown in FIG. 3, and the outputs of the photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b are used as the distance measurement pupil 351. Of the pair of images formed on the focus detection pixel array by the focus detection light fluxes passing through each of the distance measurement pupil 351 and the distance measurement pupil 352. Data on the distribution is obtained. Then, by applying an image shift detection calculation process such as a correlation calculation process or a phase difference detection process to the intensity distribution data, an image shift amount by a so-called phase difference detection method can be detected.

  Then, a conversion calculation is performed on the obtained image shift amount according to the center-of-gravity interval of the pair of distance measuring pupils, thereby obtaining a focal plane corresponding to the current focal plane (the position corresponding to the position of the microlens array on the planned focal plane) The deviation of the focal plane in the detection area), that is, the defocus amount can be obtained.

  The calculation of the image shift amount by the phase difference detection method and the calculation of the defocus amount based thereon are executed by the camera control unit 21.

  Further, the camera control unit 21 reads the output of the imaging pixel 221 of the imaging element 22 and calculates a focus evaluation value based on the read pixel output. This focus evaluation value can be obtained, for example, by extracting a high-frequency component of an image output from the imaging pixel 221 of the imaging element 22 using a high-frequency transmission filter. It can also be obtained by extracting high-frequency components using two high-frequency transmission filters having different cutoff frequencies.

  Then, the camera control unit 21 sends a drive signal to the lens control unit 37 to drive the focus lens 32 at a predetermined sampling interval (distance) to obtain a focus evaluation value at each position, and the focus evaluation value is the maximum. The focus detection by the contrast detection method is performed in which the position of the focus lens 32 is determined as the in-focus position. Note that this in-focus position is obtained when, for example, when the focus evaluation value is calculated while driving the focus lens 32, the focus evaluation value rises twice and then moves down twice. Can be obtained by performing an operation such as interpolation using the focus evaluation value.

  Next, an example of the operation of the camera 1 according to this embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing the operation of the camera 1 according to this embodiment. The following operation is started when the camera 1 is turned on.

  First, in step S101, the camera control unit 21 starts calculating the defocus amount by the phase difference detection method. In the present embodiment, the calculation process of the defocus amount by the phase difference detection method is performed as follows. That is, first, the camera control unit 21 reads a pair of image data corresponding to a pair of images from each of the focus detection pixels 222a and 222b constituting the three focus detection pixel rows 22a to 22c of the image sensor 22. In this case, when a specific focus detection position is selected by a user's manual operation, only data from focus detection pixels corresponding to the focus detection position may be read. Then, the camera control unit 21 performs image shift detection calculation processing (correlation calculation processing) based on the read pair of image data, and images at the focus detection positions corresponding to the three focus detection pixel rows 22a to 22c. The shift amount is calculated, and the image shift amount is converted into a defocus amount. Further, the camera control unit 21 evaluates the reliability of the calculated defocus amount. Note that the reliability of the defocus amount is evaluated based on, for example, the degree of coincidence and contrast of a pair of image data. The defocus amount calculation process using such a phase difference detection method is repeatedly executed at predetermined intervals.

  In step S102, the camera control unit 21 starts a focus evaluation value calculation process. In the present embodiment, the focus evaluation value calculation process is performed by reading out the pixel output of the imaging pixel 221 of the imaging element 22, extracting a high-frequency component of the read-out pixel output using a high-frequency transmission filter, and accumulating these. Done. Further, when a specific focus detection position is selected by a manual operation of the photographer, only the pixel output of the imaging pixel 221 corresponding to the selected focus detection position is read and a focus evaluation value is calculated. Also good. The focus evaluation value calculation process is repeatedly executed at predetermined intervals.

  In step S103, the camera control unit 21 determines whether or not the shutter release button provided in the operation unit 28 is half-pressed (the first switch SW1 is turned on). If the first switch SW1 is turned on, the process proceeds to step S104. On the other hand, if the first switch SW1 is not turned on, the process waits in step S103 and calculates the defocus amount until the first switch SW1 is turned on. And the calculation of the focus evaluation value are repeated.

  In step S104, the camera control unit 21 determines whether or not the defocus amount has been calculated by the phase difference detection method. If the defocus amount can be calculated, the process proceeds to step S113. On the other hand, if the defocus amount cannot be calculated, the process proceeds to step S105. In the present embodiment, even when the defocus amount can be calculated, if the reliability of the calculated defocus amount is low, it is treated that the defocus amount cannot be calculated, and the process proceeds to step S105. I will do it. In the present embodiment, for example, when the subject has a low contrast, the subject is an ultra-low brightness subject, or the subject is an ultra-high brightness subject, it is determined that the reliability of the defocus amount is low. The

  In step S104, the above determination is performed using the result of the most recent defocus amount calculation process. However, the defocus amount is continuously calculated in the most recent predetermined number of defocus amount calculation processes. If not, or if the reliability of the defocus amount is low continuously, it is determined that distance measurement is impossible, and the process proceeds to step S105. Conversely, in the defocus amount calculation process of the most recent predetermined number of times. If the defocus amount is calculated even once, it may be determined that distance measurement is possible and the process proceeds to step S113.

  If it is determined in step S104 that the defocus amount has been calculated and it is determined that distance measurement is possible, the process proceeds to step S113, and focusing driving based on the defocus amount calculated by the phase difference detection method is performed. Specifically, the camera control unit 21 calculates and calculates the lens driving amount necessary to drive the focus lens 32 to the in-focus position from the defocus amount calculated by the phase difference detection method. The lens driving amount is sent to the lens driving motor 36 via the lens control unit 37. Then, the lens driving motor 36 drives the focus lens 32 to the in-focus position based on the lens driving amount calculated by the camera control unit 21.

  In the present embodiment, the camera control unit 21 repeatedly calculates the defocus amount by the phase difference detection method while the lens driving motor 36 is driven and the focus lens 32 is driven to the in-focus position. As a result, when a new defocus amount is calculated, the camera control unit 21 drives the focus lens 32 based on the new defocus amount.

On the other hand, if it is determined in step S104 that the defocus amount cannot be calculated by the phase difference detection method, the process proceeds to step S105. In step S105, the camera control unit 21 obtains the minimum _opening aperture value _{A0_min} . Here, as described above, in the present embodiment, the lens barrel 3 is a lens barrel such as a close-up microlens whose aperture value changes as the focus lens 32 moves in the optical axis direction. The lens control unit 37 uses the minimum aperture value among the plurality of aperture values corresponding to the lens position in the optical axis direction of the focus lens 32 as the minimum aperture value _{A0_min.} Is stored in the memory prepared for. For example, in the lens barrel 3 where the open aperture value becomes smaller as the focus lens 32 is positioned on the infinity side, the open aperture value when the focus lens 32 is positioned at the closest end is F4, and the focus lens 32 is When the aperture value at the infinite end is F2.8, the minimum aperture value is F2.8. In this case, the lens control unit 37 sets the minimum aperture value _{A0_min} as F2. 8 is remembered. In step S _<b> 105, the camera control unit 21 _acquires such a minimum aperture value A _{0 —} min from a memory provided in the lens control unit 37.

  In step S106, the camera control unit 21 obtains the current aperture stage number S. Here, in this embodiment, for example, the aperture step number S is set based on the current open aperture value and the target aperture value of the optical system, for example, by exposure control by the camera control unit 21, and the camera control unit. 21 acquires the current aperture stage number S set in this way. For example, when the current maximum aperture value is F4 and the target aperture value of the optical system is F5.6, the number of aperture stages S is set to 1. In this case, the camera control unit 21 The aperture stage number S can be acquired as one stage. The aperture stage number S can also be set by a photographer's operation via the operation unit 28. In this case, the camera control unit 21 acquires the aperture stage number set by the photographer as the current aperture stage number S. You can also

In step S107, the camera control unit 21 and a minimum open aperture _{A 0_Min} acquired in step S105, based on the current stop number S obtained in step S106, the calculation of the minimum diaphragm value _{A min} is performed. In the present embodiment, since the open aperture value changes as the focus lens 32 moves in the optical axis direction, the aperture value of the optical system at the current aperture stage number S as the focus lens 32 moves in the optical axis direction. Also changes. For example, when the open aperture value is F4 when the focus lens 32 is located at the closest end, and the open aperture value is F2.8 when the focus lens 32 is located at the infinity end, the current aperture number Is set to one stage, the aperture value of the optical system when the focus lens 32 is located at the closest end is F5.6, and the optical system when the focus lens 32 is located at the infinity end. The aperture value is F4. Thus, in this embodiment, the aperture value of the optical system is obtained for each lens position in the optical axis direction of the focus lens 32. In step S107, the camera control unit 21 thus sets the minimum aperture value among the aperture values of the optical system for each lens position when the focus lens 32 is moved in the optical axis direction at the current aperture stage number S. The minimum aperture value A _min is calculated. Specifically, for example, when the minimum _opening aperture value _{A0_min} acquired in step S105 is F4 and the current aperture stage number S acquired in step S105 is 1, the camera control unit 21 The value A _min is calculated as F5.6.

In step 108, the camera control unit 21 based on the minimum diaphragm value A _min calculated in step S107, the scanning operation, the driving speed of the focus lens 32, the process of determining a scan driving speed V is performed. Here, the scan operation means that the focus lens 32 is driven by the focus lens drive motor 36 at the scan drive speed V determined in step S107, while the defocus amount by the phase difference detection method is driven by the camera control unit 21. Calculation and calculation of the focus evaluation value by the contrast detection method are simultaneously performed at a predetermined interval, whereby the detection of the in-focus position by the phase difference detection method and the detection of the in-focus position by the contrast detection method It is an operation that is executed at the same time in parallel at intervals.

In focus detection by the contrast detection method, a focus evaluation value is calculated at a predetermined sampling interval while the focus lens 32 is driven to scan, and a lens position where the focus evaluation value reaches a peak is detected as a focus position. To do. The sampling interval for the focus evaluation value increases as the driving speed of the focus lens 32 increases. When the driving speed of the focus lens 32 exceeds a predetermined speed, the sampling interval for the focus evaluation value becomes too large. The in-focus position cannot be detected properly. This is because, as the focus evaluation value sampling interval increases, the object to be detected can detect the focus state properly once even when the focus lens 32 is driven from the closest end to the infinite end. This is because the focus state at the position of the subject cannot be properly detected without entering the depth. In particular, the smaller the aperture value of the optical system, the narrower the subject depth. Therefore, in order to detect the in-focus position appropriately, the sampling interval of the focus evaluation value is made smaller than when the aperture value of the optical system is large. There is a need to. Therefore, in this embodiment, the camera control unit 21 uses the maximum driving speed among the driving speeds of the focus lens lens 32 that can appropriately detect the in-focus position at the minimum aperture value A _min calculated in step S108. Is calculated as the scan drive speed V.

  In step S109, the scan operation is started at the scan drive speed V determined in step S108. Specifically, the camera control unit 21 sends a scan drive start command to the lens control unit 37, and the lens control unit 37 drives the focus lens drive motor 36 based on the command from the camera control unit 21 to focus. The lens 32 is scan-driven at the scan drive speed V determined in step S108. The camera control unit 21 reads a pair of image data corresponding to the pair of images from the focus detection pixels 222a and 222b of the image sensor 22 at a predetermined interval while driving the focus lens 32 at the scan driving speed V. Based on this, the defocus amount is calculated and the reliability of the calculated defocus amount is evaluated by the phase difference detection method, and the focus lens 32 is driven at the scan drive speed V, and imaging is performed at predetermined intervals. The pixel output is read out from the imaging pixel 221 of the element 22, and based on this, a focus evaluation value is calculated, thereby acquiring a focus evaluation value at a different focus lens position. Perform detection.

  In step S110, the camera control unit 21 determines whether or not the defocus amount can be calculated by the phase difference detection method as a result of the scanning operation. If the defocus amount can be calculated, it is determined that distance measurement is possible and the process proceeds to step S113. On the other hand, if the defocus amount cannot be calculated, it is determined that distance measurement is not possible and the process proceeds to step S111. . In step S110, as in step S104, even when the defocus amount can be calculated, if the reliability of the calculated defocus amount is low, the defocus amount cannot be calculated. The process proceeds to step S111.

  In step S111, it is determined whether the in-focus position has been detected by the contrast detection method as a result of the scanning operation performed by the camera control unit 21. If the in-focus position can be detected by the contrast detection method, the process proceeds to step S114. If the in-focus position cannot be detected, the process proceeds to step S112.

  In step S <b> 112, the camera control unit 21 determines whether or not the scan operation has been performed over the entire driveable range of the focus lens 32. When the scan operation is not performed for the entire driveable range of the focus lens 32, the process returns to step S110, and steps S110 to S112 are repeated to perform the scan operation, that is, while the focus lens 32 is driven to scan. The operation of simultaneously executing the calculation of the defocus amount by the phase difference detection method and the detection of the in-focus position by the contrast detection method at predetermined intervals is continuously performed. On the other hand, if the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S115.

  As a result of executing the scanning operation, if it is determined in step S110 that the defocus amount can be calculated by the phase difference detection method, the scanning operation is stopped, and then the process proceeds to step S113. As described above, the focus drive for driving the focus lens 32 is performed up to the focus position detected by the phase difference detection method.

  As a result of executing the scanning operation, if it is determined in step S111 that the in-focus position has been detected by the contrast detection method, the scanning operation is stopped, and then the process proceeds to step S114 to control the camera. The unit 21 performs focus driving for driving the focus lens 32 to the focus position detected by the contrast detection method.

  On the other hand, if it is determined in step S112 that the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S115. In step S115, as a result of performing the scanning operation, focus detection could not be performed by the contrast detection method, so that the scanning operation is terminated, and then in-focus display is performed. Note that the in-focus state display is performed by the electronic viewfinder 26, for example.

  As described above, the camera 1 according to this embodiment operates.

As described above, in the present embodiment, when the open aperture value changes with the movement of the focus lens 32 in the optical axis direction, such as when shooting using a close-up microlens, Among the plurality of open aperture values corresponding to the lens position, the minimum open aperture value is acquired as the minimum open aperture value _{A0_min} . Then, based on the acquired minimum aperture value _{A0_min} and the current aperture stage number S, the minimum aperture value among the aperture values when the focus lens 32 is moved in the optical axis direction at the current aperture stage number S. and it is calculated as the minimum diaphragm value _{a min.} Then, the aperture value of the optical system as the minimum diaphragm value A _min, when performing a scan operation, the driving speed of the focus lens 32 to the focus position can be properly detected, determined as the scan driving speed V, A scan operation is executed at the determined scan drive speed V. Thus, in this embodiment, when the focus lens 32 is moved in the optical axis direction, such as when a close-up microlens is used, the aperture value changes, and the aperture of the optical system at the current aperture stage number S is changed. Even when the value changes, the scan operation can be performed at the scan drive speed V suitable for focus detection, and the in-focus position can be detected appropriately.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, in the above-described embodiment, the minimum aperture value A _{0 —} min that is the minimum aperture value among the plurality of aperture values corresponding to the lens position of the focus lens 32 is the minimum obtained with the current number of aperture stages. the aperture is calculated as the minimum diaphragm value a _min, even when the aperture value of the optical system is a minimum aperture value a _min, the driving speed of the detectable focus lens 32 the focus state of the optical system, as the scan driving speed V However, the present invention is not limited to this configuration, and may be configured as follows, for example.

  In other words, the open aperture value (first open aperture value) corresponding to the first position closer to the current lens position than the current lens position of the focus lens 32 and the open position corresponding to the second position on the infinite side of the current lens position. A smaller one of the aperture values (second aperture value) is acquired from the lens barrel 3 as a predetermined aperture value. Then, the aperture value obtained when the focus lens 32 is moved to the lens position corresponding to the predetermined open aperture value with the current aperture stage number is calculated as the predetermined aperture value. Even when the aperture value of the optical system is a predetermined aperture value, scan driving may be performed with the drive speed of the focus lens 32 capable of detecting the focus state of the optical system as the scan drive speed V.

  Alternatively, when the open aperture value corresponding to the predetermined lens position of the focus lens 32 is smaller than the open aperture value corresponding to the current lens position, the open aperture value corresponding to the predetermined lens position. Is obtained from the lens barrel 3 as a predetermined maximum aperture value. Then, the aperture value obtained when the focus lens 32 is moved to the lens position corresponding to the acquired predetermined open aperture value with the current aperture number is calculated as the predetermined aperture value. Even when the aperture value of the optical system is a predetermined aperture value, the scan operation may be performed with the drive speed of the focus lens 32 capable of detecting the focus state of the optical system as the scan drive speed V.

Further, in the above-described embodiment, the scan drive speed V in the scan operation in which the focus detection by the phase difference detection method and the focus detection by the contrast detection method are simultaneously performed at a predetermined interval while driving the focus lens 32. has been illustrated a structure for calculating based on the minimum diaphragm value a _min, for example, without performing focus detection by a phase difference detection method, in a scene that perform only focus detection by the contrast detection method, the focus detection by the contrast detection method in the driving speed of the focus lens 32, it may be calculated based on the minimum diaphragm value a _min.

  The camera 1 of the embodiment described above is not particularly limited, and the present invention may be applied to other optical devices such as a digital video camera, a lens-integrated digital camera, and a camera for a mobile phone.

DESCRIPTION OF SYMBOLS 1 ... Digital camera 2 ... Camera body 21 ... Camera control part 22 ... Imaging device 221 ... Imaging pixel 222a, 222b ... Focus detection pixel 3 ... Lens barrel 32 ... Focus lens 36 ... Focus lens drive motor 37 ... Lens control part

Claims (6)

A focus detection unit that detects the focus state of the optical system by calculating an evaluation value related to the contrast of the image by the optical system while driving the focus adjustment lens in the optical axis direction by the drive unit;
Open aperture value when position that put in the optical axis direction is the first position of the focusing lens, and a different second and position is the first position that put in the optical axis direction of the focusing lens of open aperture value when a position, a first obtaining unit that retrieve and the smaller the predetermined open aperture value,
A second acquisition unit that acquires the current aperture stage number;
Based on the predetermined aperture value and the current aperture level, the aperture value when the focus adjustment lens is moved to the lens position corresponding to the predetermined aperture value at the current aperture level is set as the predetermined aperture value. A computing unit to calculate,
A control unit that causes the focus detection unit to detect the focus state of the optical system while driving the focus adjustment lens to the drive unit,
Wherein the control unit, the predetermined aperture value on the basis of the focus adjusting apparatus for determining the driving speed of said focusing lens when said focus detection unit detects the focus state of the optical system. The focus adjustment device according to claim 1,
The focus adjustment device, wherein the first position is a position closer to the current lens position, and the second position is an infinite position than the current lens position. A first value that is an open aperture value when the position of the focus lens is the first position, and a first value that is an open aperture value when the position of the focus lens is a second position different from the first position. An acquisition unit for acquiring the smaller one of the two values and the current aperture stage number;
Using the smaller value of the first value and the second value and the current number of aperture stages, the aperture value is the smaller of the first value and the second value. An arithmetic unit that calculates a third value that is an aperture value when the current aperture stage number is set at the position of the focus lens;
And a control unit that performs control to move the focus lens at a speed determined by using the third value when detecting the focus state by moving the focus lens. The focus adjustment device according to claim 3 ,
When the control unit performs control to move the focus lens at a speed determined using the third value, by calculating an evaluation value related to the contrast of the image by the optical system including the focus lens, A focus adjustment device having a focus detection unit for detecting a focus state of the optical system. An imaging apparatus comprising the focus adjustment apparatus according to any one of claims 1 to 4 . An imaging apparatus according to claim 5 , wherein
An imaging apparatus having a lens barrel having an optical system.

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