JP6127730B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus.

  2. Description of the Related Art Conventionally, there has been known an imaging apparatus that moves a focus lens in accordance with the movement of a zoom lens in order to capture an image that is focused on a subject during a zoom operation (see, for example, Patent Document 1).

JP 2002-228913 A

  However, the conventional technology stores in advance a zoom tracking table indicating the relationship between the position of the zoom lens and the position of the focus lens in accordance with the zoom lens and the focus lens designed with predetermined design values. Since the focus lens is driven based on the stored zoom tracking table, if there is an error between the actual value of the zoom lens or focus lens and the lens design value, zoom During operation, there was a case where an image focused on the subject could not be taken.

  The problem to be solved by the present invention is to provide an imaging apparatus capable of suitable focus adjustment control.

  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] An imaging apparatus according to the present invention includes a zoom operation detection unit that detects a zoom operation driven by a zoom lens in the optical axis direction, and a plurality of focus detection positions set at a plurality of positions in the image plane of the optical system. A focus detection unit that detects a focus state of the optical system in each of the above, a target position setting unit that sets a focus detection position for performing focus adjustment among the plurality of focus detection positions as a first target position, and A focus adjustment unit that performs focus adjustment of the optical system by causing the drive unit to drive a focus adjustment lens based on a focus state of the optical system at a first target position, the imaging apparatus comprising: When the first target position at the start of zooming is set outside a predetermined central area including the optical axis in the area on the shooting screen, the position setting unit is within the predetermined central area. Set focus A focus detection position for performing focus adjustment during the zoom operation is selected as a second target position from the detection positions, and the focus adjustment unit is configured to select the second target position during the zoom operation. The focus adjustment of the optical system during the zoom operation is performed based on the focus state of the optical system at the second target position.

  [2] In the invention related to the imaging apparatus, the target position setting unit is a focus detection position set in the central region when the second target position is selected, and the subject at the focus detection position A focus detection position in which the position of the image plane is within the range of three times the depth of focus of the optical system with respect to the position of the image plane of the subject at the first target position is selected as the second target position. It can be constituted as follows.

  [3] In the invention relating to the imaging apparatus, the target position setting unit may change a focus detection position for performing the focus adjustment during the zoom operation from the first target position to the second target position. When the zoom operation is completed, the focus detection position for performing the focus adjustment can be returned to the first target position at the start of the zoom operation.

  [4] In the invention according to the imaging apparatus, the imaging unit includes a plurality of imaging pixels and a plurality of focus detection pixels, captures an image by the optical system, and outputs an image signal corresponding to the captured image The focus detection unit detects a shift amount of an image plane by the optical system based on an image signal output from the focus detection pixel, and performs focus detection by a phase difference detection method. Can be configured.

  [5] In the invention related to the imaging apparatus, an imaging unit that captures an image by the optical system and outputs an image signal corresponding to the captured image, and a member independent of the imaging unit, the pupil of the optical system A light receiving unit that receives a pair of light fluxes that pass through different regions and outputs a pair of light reception signals, and the focus detection unit, based on the pair of light reception signals output from the light reception unit, By detecting the shift amount of the image plane by the optical system, it is possible to perform focus detection by the phase difference detection method.

  According to the present invention, it is possible to provide an imaging apparatus capable of suitable focus adjustment control.

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. 4A is an enlarged front view showing one of the imaging pixels 221, FIG. 4B is an enlarged front view showing one of the focus detection pixels 222a, and FIG. FIG. 4D is an enlarged front view showing one of the focus detection pixels 222b, FIG. 4D is a cross-sectional view showing one of the imaging pixels 221 in an enlarged manner, and FIG. 4E is one of the focus detection pixels 222a. FIG. 4F is an enlarged sectional view showing one of the focus detection pixels 222b. FIG. 5 is a cross-sectional view taken along the line VV in FIG. FIG. 6 is a diagram illustrating an arrangement example of the focus detection areas set in the photographing screen 50 of the photographing optical system. FIG. 7 is a flowchart showing the operation of the camera according to the present embodiment. FIG. 8 is a flowchart showing scan operation execution processing 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 an embodiment of the present invention. 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 photographing optical system including lenses 31, 32, 33, 34 and a diaphragm 35.

  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 322 while its position is detected by the focus lens encoder 321.

  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 driving motor 322, 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 moving the rotating cylinder with respect to the lens barrel 3 moves straight in the direction of the optical axis L1, but the focus lens drive motor 322 as the drive source is the lens. The lens barrel 3 is provided. The focus lens drive motor 322 and the rotating cylinder are connected by a transmission composed of a plurality of gears, for example, and when the drive shaft of the focus lens driving motor 322 is driven to rotate in any one direction, it is transmitted to the rotating 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 322 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 a focus lens encoder 321. 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 focus lens encoder 321 of this embodiment, the rotation of a rotating disk connected to the rotational drive of a rotating cylinder is detected by an optical sensor such as a photo interrupter, and a pulse signal corresponding to the number of rotations is output. The brush contact provided on either one of the encoder pattern on the surface of the flexible printed wiring board provided on one of the fixed cylinder and the rotating cylinder is brought into contact with the moving amount of the rotating cylinder (in the optical axis direction even in the rotation direction). Any of which can detect a change in the contact position according to the detection circuit by 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 focus lens encoder 321 is sent to the camera control unit 21 (to be described later) via the lens control unit 36, and the focus lens drive motor 322 calculates based on this information. The focus lens 32 thus driven is driven by being sent from the camera control unit 21 via the lens control unit 36.

  The zoom lens 33 is provided so as to be movable along the optical axis L1 of the lens barrel 2, and its position is adjusted by the zoom lens drive motor 332 while its position is detected by the zoom lens encoder 331. The position of the zoom lens 33 changes, for example, when the photographer turns the zoom ring (not shown) of the lens barrel 2 and the focal length of the optical system changes accordingly. Then, the position information of the zoom lens 33 detected by the zoom lens encoder 331 is transmitted to the lens control unit 36. The moving mechanism of the zoom lens 33 may be the same as the moving mechanism of the focus lens 32 described above, and the zoom lens encoder 331 may be the same as the focus lens encoder 321 described above. .

  The diaphragm 35 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 adjust the amount of blur. The adjustment of the aperture diameter by the diaphragm 35 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 36. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 36 by a manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the aperture 35 is detected by an aperture sensor (not shown), and the lens controller 36 recognizes the current aperture diameter.

  The lens control unit 36 detects the position of the zoom lens 33 detected by the zoom lens encoder 332, and when the zoom lens 33 is driven, the lens control unit 36 moves the focus lens 32 according to the movement amount of the zoom lens 33. It is driven to perform zoom tracking control for fine adjustment of focus.

  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.

  A camera control unit 21 is provided in the camera body 2. The camera control unit 21 is electrically connected to the lens control unit 36 through an electrical signal contact unit 41 provided on the mount unit 4, receives lens information from the lens control unit 36, and defocuses to the lens control unit 36. Send information such as volume and aperture diameter. The lens information transmitted from the lens control unit 36 includes position information on the focus lens 32 and the zoom lens 33, a zoom operation signal indicating that the zoom lens 33 is being driven, and the like.

  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 a moving image shooting start switch, and can switch between an auto focus mode and a manual focus mode. Yes. 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.

  4A is an enlarged front view showing one of the imaging pixels 221 and FIG. 4D is a cross-sectional view. One imaging pixel 221 includes a microlens 2211, a photoelectric conversion unit 2212, and a color filter (not shown), and on the surface of the semiconductor circuit substrate 2213 of the imaging element 22 as shown in the cross-sectional view of FIG. A photoelectric conversion portion 2212 is built, and a microlens 2211 is formed on the surface thereof. 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, the imaging element 22 is provided with a plurality of focus detection pixel rows 220 in which focus detection pixels 222a and 222b are arranged in place of the above-described imaging pixels 221. As shown in FIG. 3, one focus detection pixel row 220 includes a plurality of focus detection pixels 222 a and 222 b that are alternately arranged adjacent to each other. 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.

  4B is an enlarged front view of one of the focus detection pixels 222a, and FIG. 4E is a cross-sectional view of the focus detection pixel 222a. 4C is an enlarged front view showing one of the focus detection pixels 222b, and FIG. 4F is a cross-sectional view of the focus detection pixel 222b. As shown in FIG. 4B, 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. 4C, and a semiconductor of the image sensor 22 as shown in the cross-sectional view of FIG. 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 to form a focus detection pixel row 220 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. 4B and 4C have a semicircular shape, the shape of the photoelectric conversion units 2222a and 2222b is 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. 5 is a cross-sectional view taken along the line V-V 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. In FIG. 5, only the focus detection pixels 222 a and 222 b that are located in the vicinity of the photographing optical axis L <b> 1 are illustrated, but other focus detection pixels other than the focus detection pixels illustrated in FIG. 5 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. 5, the arrangement direction of the focus detection pixels 222 a-1, 222 b-1, 222 a-2, and 222 b-2 coincides with the arrangement direction of the pair of distance measuring pupils 351 and 352.

  As shown in FIG. 5, 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 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. 5, the photoelectric conversion unit 2222a-1 of the focus detection pixel 222a-1 is formed on the microlens 2221a-1 by a 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. The intensity distribution data is subjected to an image shift detection calculation process such as a correlation calculation process or a phase difference detection process to detect an image shift amount by a so-called phase difference detection method.

  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 current focal plane with respect to the planned focal plane (the focal point corresponding to the position of the microlens array on the planned focal plane). Deviation of the focal plane in the detection area), that is, the defocus amount.

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

  Further, in the present embodiment, as shown in FIG. 2, 51 focus detection pixel columns 220 are provided, and as shown in FIG. 6, corresponding to the respective positions of these focus detection pixel columns 220, On the shooting screen 50, 51 focus detection areas AFP indicated by AFP1 to AFP51 are set. The camera control unit 21 calculates the defocus amount in each focus detection area AFP based on the output of the focus detection pixel row 220 corresponding to these focus detection areas AFP. FIG. 6 is a diagram showing an example of the arrangement of focus detection areas set in the imaging screen 50 of the imaging optical system, and the number and arrangement of the focus detection areas AFP are limited to the mode shown in FIG. It is not a thing.

  Further, the camera control unit 21 sets a focus detection area for performing focus adjustment among the plurality of focus detection areas AFP1 to AFP51 as a first target area, and based on the defocus amount in the first target area, The focus state of the optical system is adjusted by driving the focus lens 32. For example, when the photographer selects a focus detection area for performing focus adjustment among the plurality of focus detection areas AFP1 to AFP51 via the operation unit 28, the camera control unit 21 selects the focus selected by the photographer. The detection area AFP can be set as the first target area. The camera control unit 21 may automatically set, for example, the focus detection area that is closest to the camera or the focus detection area that is located in the center of the shooting screen 50 as the first target area.

  Furthermore, 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 control signal to the lens control unit 36 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 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. FIG. 7 is a flowchart showing the operation of the camera 1 according to this embodiment. In the following, a focus adjustment method at the time of moving image shooting will be described with reference to FIG. In the focus adjustment process described below, a focus detection area for performing focus adjustment among the plurality of focus detection areas AFP1 to AFP51 set in the shooting screen 50 is already set as the first target area. A scene is illustrated and demonstrated. In addition, the focus adjustment process described below is started, for example, when a moving image shooting start switch provided in the operation unit 28 is turned on.

  First, in step S101, the camera control unit 21 starts calculating the defocus amount in the plurality of focus detection areas AFP1 to AFP51 set in the shooting screen 50. Specifically, the camera control unit 21 reads a pair of image data corresponding to a pair of images from the focus detection pixels 222a and 222b of the focus detection pixel row 220 corresponding to the focus detection areas AFP1 to AFP51, respectively. Then, the camera control unit 21 performs an image shift detection calculation process (correlation calculation process) based on the read pair of image data, calculates an image shift amount, and further converts the image shift amount into a defocus amount. Thus, the defocus amounts in the focus detection areas AFP1 to AFP51 are calculated. Further, the camera control unit 21 repeatedly executes the calculation of the defocus amount at a predetermined cycle until it is determined in step S111 that the moving image shooting has been completed.

  In step S102, the camera control unit 21 determines whether a zoom operation has been started. For example, in the present embodiment, when the movement of the zoom lens 33 is detected by the zoom lens encoder 331, a signal indicating that the zoom operation is being performed is output to the camera control unit 21 via the lens control unit 36. Thus, the camera control unit 21 can determine whether or not the zoom operation has been started. If it is determined that the zoom operation has not been started, the process proceeds to step S112. On the other hand, if it is determined that the zoom operation has been started, the process proceeds to step S103.

  In step S <b> 103, whether or not the first target area set as the focus detection area for performing focus adjustment at the start of the zoom operation by the camera control unit 21 is set outside the central region of the shooting screen 50. Judgment is made. As shown in FIG. 6, the focus detection area AFP1 according to the present embodiment is designed so as to be positioned on the optical axis, and an area having a predetermined size including the optical axis is set as a central area. The central region is not limited to the range shown in FIG. 6 and can be set as appropriate. For example, even when the captured image is changed at a constant magnification by the zoom operation (the captured image is changed by a constant angle of view), the same as the face of the person before and after the change of the magnification of the captured image An area where there is a focus detection area that can capture the subject can be set as the central area. As an example of such a central region, a region including the optical axis, a region having a size of about ¼ of the shooting screen 50, and a region having a shape similar to the shooting screen 50 is set in the center. It can be set as an area. If it is determined that the first target area is set within the central area of the shooting screen 50, the process proceeds to step S106, while the first focus target area is set outside the central area of the shooting screen 50. If it is determined that it has been performed, the process proceeds to step S104.

  In step S <b> 104, the camera control unit 21 stores a first target area set as a focus detection area for performing focus adjustment at the start of the zoom operation in a memory included in the camera control unit 21. For example, in the example shown in FIG. 6, the face detection mode is set, a human face exists in the focus detection area AFP39 located outside the center area of the shooting screen 50, and the focus detection area AFP39 performs focus adjustment. Therefore, the camera control unit 21 stores the focus detection area AFP39 as the first target area at the start of the zoom operation. In addition, the 1st object area memorize | stored in memory is utilized by step S110 mentioned later.

  In step S105, the camera control unit 21 selects a second target area for performing focus adjustment during the zoom operation. Specifically, the camera control unit 21 selects, from the plurality of focus detection areas set in the center area of the shooting screen 50, the focus detection area used for focus adjustment during the zoom operation as the second target. Select as area. For example, the camera control unit 21 is a focus detection area set in the central region of the shooting screen 50, and the defocus amount in the focus detection area AFP is smaller than the defocus amount in the first target area. A focus detection area that is within the range of three times the depth of focus of the optical system can be set as the second target area. That is, the camera control unit 21 determines the amount of image plane deviation in the optical axis direction indicated by the difference between the defocus amount in the focus detection area set in the central region of the shooting screen 50 and the defocus amount in the first target area. A focus detection area that does not exceed the range of three times the focal depth of the optical system can be set as the second target area. Alternatively, the camera control unit 21 may select the focus detection area AFP1 corresponding to the optical axis among the plurality of focus detection areas set in the central area as the second target area, or in the central area. A focus detection area that is located directly below the first target area and is closest to the first target area among the plurality of set focus detection areas may be selected as the second target area.

  Here, when the focus lens 32 is driven based on the focus state of the first target area located outside the shooting screen 50 during the zoom operation, the magnification of the captured image is changed by the zoom operation (the captured image is changed). When the angle of view changes), the subject captured in the first target area may move with the change in the magnification of the captured image, and may deviate from the first target area. As a result, the subject in the first target area may change, and the defocus amount in the first target area may change significantly. As a result, the focus lens 32 is driven based on the greatly changed defocus amount. For this reason, it may become impossible to capture an image in which the subject is in focus during the zoom operation. In contrast, in the present embodiment, the first target area set outside the central area of the shooting screen 50 at the start of the zoom operation is changed to the second target area in the central area of the shooting screen 50 at the zoom operation. By changing, the change in the defocus amount in the second target area can be suppressed even when the magnification of the captured image changes due to the zoom operation (the angle of view of the captured image changes). You can shoot images that are in focus.

  In step S106, the camera control unit 21 determines whether the defocus amount has been calculated in the second target area set in step S105. If the defocus amount can be calculated in the second target area, it is determined that distance measurement is possible, and the process proceeds to step S107, where the focus lens 32 is driven based on the defocus amount in the second target area. In step S108, the camera control unit 21 determines whether or not the zoom operation has ended. If it is determined that the zoom operation has ended, the process proceeds to step S110, while the zoom operation is performed. If it is determined that the focusing is performed, the process returns to step S106, and the focus adjustment of the optical system is repeatedly executed based on the defocus amount in the second target area.

  In step S106, when the defocus amount cannot be calculated in the second target area, the process proceeds to step S109, and the focus lens 32 is driven by zoom tracking. Specifically, the camera control unit 21 uses a zoom tracking table that indicates the relationship between the position of the zoom lens 33 and the position of the focus lens 32 for each shooting distance, according to the amount of movement of the zoom lens 33. The driving amount of the focus lens 32 is calculated. The calculated driving amount of the focus lens 32 is transmitted to the focus lens drive motor 322, and the focus lens 32 is driven to perform zoom tracking control for finely adjusting the focus. Then, the process proceeds to step S108, and when the zoom operation is being performed, the focus adjustment is repeatedly executed based on the defocus amount in the second target area.

  In step S110, since the zoom operation has ended, the camera control unit 21 causes the first target area at the start of the zoom operation stored in step S105 to focus for adjusting the focus after the zoom operation ends. Set as detection area. That is, in this embodiment, when the focus detection area for performing focus adjustment is changed from the first target area to the second target area during the zoom operation, the focus adjustment is performed after the zoom operation is completed. The focus detection area is returned from the second target area to the first target area.

  If the first target area is set in the central area in step S103, the process proceeds to step S106, and the focus adjustment of the optical system is performed based on the defocus amount in the first target area. . In this case, the process of step S110 is omitted.

  In step S111, the camera control unit 21 determines whether or not the moving image shooting has ended. When the moving image shooting is completed, the operation of the camera 1 shown in FIG. 7 is ended. On the other hand, when the moving image shooting is not ended, the process returns to step S102 and the operation of the camera 1 described above is repeated.

  If it is determined in step S102 that the zoom operation is not started, the process proceeds to step S112, and the camera control unit 21 determines whether or not the defocus amount can be calculated in the first target area. If the defocus amount can be calculated in the first target area, it is determined that distance measurement is possible, and the process proceeds to step S113, and the focus lens 32 is driven based on the defocus amount in the first target area. . On the other hand, if the defocus amount cannot be calculated in the first target area, the process proceeds to step S114.

  In step S114, the camera control unit 21 performs a wobbling operation for minutely driving the focus lens 32 in the vicinity of the current position. The camera control unit 21 calculates the focus evaluation value by the contrast detection method during the wobbling operation, and thereby determines the drive direction of the focus lens 32 when performing the scanning operation described later based on the calculated focus evaluation value. decide. During the wobbling operation, the focus evaluation value is calculated by the contrast detection method, the defocus amount is calculated by the phase difference detection method, and the scan operation is performed based on the calculated focus evaluation value and the defocus amount. The driving direction of the focus lens 32 at that time may be determined.

  In step S115, the camera control unit 21 performs a scan operation execution process for executing the scan operation. Here, the scan operation refers to the calculation of the defocus amount by the phase difference detection method and the focus evaluation value by the contrast detection method by the camera control unit 21 while the focus lens 32 is scan-driven by the focus lens drive motor 322. The calculation is performed simultaneously 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 are simultaneously performed at the predetermined interval. Hereinafter, the scan operation execution process according to the present embodiment will be described with reference to FIG. FIG. 8 is a flowchart showing a scan operation execution process according to the present embodiment.

  First, in step S201, the camera control unit 21 performs a scan operation start process. Specifically, the camera control unit 21 sends a scan drive start command to the lens control unit 36, and the lens control unit 36 drives the focus lens drive motor 322 based on the command from the camera control unit 21 to focus. The lens 32 is scan-driven along the optical axis L1. Note that the camera control unit 21 scans and drives the focus lens 32 in the drive direction of the focus lens 32 determined by the wobbling operation in step S114.

  Then, while driving the focus lens 32, the camera control unit 21 reads out 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 predetermined intervals. The phase difference detection method calculates the defocus amount, evaluates the reliability of the calculated defocus amount, and drives the focus lens 32 to drive the pixel output from the imaging pixel 221 of the imaging element 22 at a predetermined interval. Reading is performed, and based on this, a focus evaluation value is calculated, thereby acquiring a focus evaluation value at a different focus lens position, thereby detecting a focus position by a contrast detection method.

  In step S202, it is determined whether or not the defocus amount has been calculated by the phase difference detection method as a result of the scanning operation performed by the camera control unit 21. If the defocus amount can be calculated, it is determined that distance measurement is possible and the process proceeds to step S205. 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 S203. . In step S202, even when the defocus amount can be calculated, if the reliability of the calculated defocus amount is equal to or less than a predetermined value, the defocus amount cannot be calculated. The process proceeds to step S203.

  In step S203, 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 S206. If the in-focus position cannot be detected, the process proceeds to step S204.

  In step S <b> 204, the camera control unit 21 determines whether the scan operation has been performed for the entire driveable range of the focus lens 32. If the scan operation is not performed for the entire driveable range of the focus lens 32, the process returns to step S202, and steps S202 to S204 are repeated to perform the scan operation, that is, while the focus lens 32 is scan-driven. 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, when the execution of the scan operation is completed for the entire driveable range of the focus lens 32, the process proceeds to step S207.

  If it is determined in step S202 that the defocus amount can be calculated by the phase difference detection method in step S202, the process proceeds to step S205, and the defocus amount calculated by the phase difference detection method is set. Based on the focusing operation.

  That is, the camera control unit 21 first performs a stop process of the scanning operation, and the lens driving amount necessary to drive the focus lens 32 from the defocus amount calculated by the phase difference detection method to the in-focus position. Is calculated. The calculated lens driving amount is sent to the focus lens driving motor 322 via the lens control unit 36, and the focus lens driving motor 322 moves the focus lens 32 to the in-focus position based on the calculated lens driving amount. Drive.

  In this embodiment, the camera control unit 21 repeatedly calculates the defocus amount by the phase difference detection method even while the focus lens driving motor 322 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 focus lens 32 is driven based on the new defocus amount.

  As a result of executing the scanning operation, if it is determined in step S203 that the in-focus position has been detected by the contrast detection method, the process proceeds to step S206 and is based on the in-focus position detected by the contrast detection method. The drive operation of the focus lens 32 is performed.

  That is, first, after a scan operation stop process is performed, a lens drive process for driving the focus lens 32 to the focus position is performed based on the focus position detected by the contrast detection method. Note that when driving the focus lens 32 to the in-focus position based on the detection result by the contrast detection method, the focus by the phase difference detection method is completed until the drive of the focus lens 32 to the in-focus position is completed. It is preferable to prohibit the driving of the focus lens 32 based on the detection result. Thereby, the hunting phenomenon of the focus lens 32 can be suppressed.

  On the other hand, if it is determined in step S204 that the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S207. In step S207, as a result of performing the scanning operation, focus detection could not be performed by any of the phase difference detection method and the contrast detection method. Therefore, the scanning operation end processing is performed, and this scanning operation execution processing is performed. Is done.

  Thus, after the scan operation execution process of step S115 is performed and the scan operation execution process of step S115 is completed, the operation of the camera 1 is also ended.

  As described above, the camera 1 in the present embodiment operates.

  As described above, the camera 1 according to the present embodiment calculates the defocus amount by the phase difference detection method in the focus detection area AFP during the zoom operation, and drives the focus lens 32 based on the calculated defocus amount. The focus of the optical system can be adjusted based on the actual focus state of the optical system. Thereby, in this embodiment, compared with the case where zoom tracking control is performed using a predetermined zoom tracking table based on the zoom lens 33 and the focus lens 32 designed with predetermined design values. Even when an error occurs between the actual characteristic value of the zoom lens 33 or the focus lens 32 and the design value of these lenses, the focus adjustment of the optical system can be performed based on the actual focus state of the optical system. Therefore, it is possible to take an image in which the subject is in focus during the zoom operation.

  In the present embodiment, when the first target area for performing focus adjustment at the start of the zoom operation is located outside the central area of the shooting screen 50, the first target area is set within the central area of the shooting screen 50. The focus detection area AFP is selected as a second target area for performing focus adjustment during the zoom operation, and focus adjustment of the optical system is performed based on the defocus amount in the second target area. Here, for example, in the example shown in FIG. 6, when the focus detection area AFP39 located outside the central area of the shooting screen 50 is set as the first target area at the start of the zoom operation, the zoom operation is continued as it is. When the magnification of the captured image is changed (the angle of view of the captured image is changed), the subject supplemented in the first target area AFP39 moves with the change in the magnification of the captured image due to the zoom operation. Thus, the subject corresponding to the first target area AFP39 may change during the zoom operation. In such a case, the defocus amount in the first target area AFP 39 changes greatly, and the focus lens 32 is driven in accordance with the changed defocus amount. Therefore, an image focused on the subject during the zoom operation There was a case that could not shoot. On the other hand, in the present embodiment, the focus detection area for performing the focus adjustment during the zoom operation is selected from the first target area set outside the central region of the shooting screen 50 at the start of the zoom operation. By changing to the second target area set in the center area of the image, even if the magnification of the captured image is changed by the zoom operation (the angle of view of the captured image is changed), the subject greatly changes in the second target area. Therefore, it is possible to capture an image in which the subject is in focus even during a zoom operation. In particular, when the magnification of the captured image is increased by the zoom operation (when the angle of view of the captured image is decreased), the depth of field of the optical system is narrowed, and the subject is easily removed from the shooting screen 50. A greater effect can be achieved.

  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 focus adjustment process at the time of moving image shooting has been described. However, the present invention is not limited to this. For example, the same process can be performed in the focus adjustment process at the time of through image shooting.

  In the above-described embodiment, the configuration in which the focus detection area for performing the focus adjustment is returned to the first target area at the start of the zoom operation after the zoom operation is finished is exemplified. At the end of the zoom operation, a subject that is a focus detection area around the first target area at the start of the zoom operation and is close to the subject distance of the subject captured in the first target area at the start of the zoom operation The focus detection area supplementing the above may be set as a focus detection area for performing focus adjustment. Accordingly, even after the zoom operation, it becomes easy to capture the subject captured in the first target area at the start of the zoom operation.

  Further, in the above-described embodiment, the focus detection by the phase difference detection method is performed in the second target area, and the focus adjustment of the optical system is performed based on the focus detection result by the phase difference detection method. For example, the second target area may be configured to perform focus detection by the contrast detection method and adjust the focus of the optical system based on the focus detection result by the contrast detection method.

  In addition, in the above-described embodiment, the lens control unit 36 outputs a signal indicating that the zoom operation has started to the camera control unit 21, thereby exemplifying a configuration for determining whether or not the zoom operation has started. However, the present invention is not limited to this configuration. For example, when a zoom operation switch provided in the operation unit 28 is pressed, the operation unit 28 outputs a signal indicating that the zoom operation has been started. It may be configured to determine whether or not has started.

  In the above-described embodiment, when the first target area is located outside the central region of the shooting screen 50 at the start of the zoom operation, the focus detection area in the central region is selected as the second target area during the zoom operation. In the above example, the focus adjustment is performed based on the defocus amount in the second target area. For example, the zoom operation is performed so that the magnification of the captured image is increased (the angle of view of the captured image is reduced). In this case, as in the above embodiment, the focus detection area in the central region is selected as the second target area, and the focus is adjusted based on the defocus amount in the second target area. When the zoom operation is performed such that the angle of view is reduced (so that the angle of view of the captured image is widened), focus adjustment may be performed by zoom tracking.

  Further, in the above-described embodiment, the defocus amount is calculated in the plurality of focus detection areas AFP set in the photographing screen 50, and the focus adjustment is performed based on the defocus amount in the second target area among these defocus amounts. However, the present invention is not limited to this configuration. For example, the defocus amount may be calculated only in the second target area, and the focus may be adjusted based on the calculated defocus amount in the second target area. Good. Moreover, it is good also as a structure which reads data only from the focus detection pixel row | line | column 220 corresponding to a 2nd object area among the some focus detection pixel row | line | columns 220 installed in the image pick-up element 22. FIG.

  In the above-described embodiment, the image sensor 22 has a plurality of imaging pixels 221 and a plurality of focus detection pixels 222a and 222b, and the focus detection provided in the image sensor 22 when a zoom operation is performed during moving image shooting. The configuration of performing focus adjustment while capturing a moving image by calculating the defocus amount by the phase difference detection method based on the image signals output from the pixels 222a and 222b is not limited to this configuration. For example, it is a member independent of the image sensor 22 and includes a light receiving sensor that receives a pair of pupil-divided light beams and outputs a pair of image data, and branches a light beam incident from the optical system by a half mirror. A part of the light beam is guided to the light receiving sensor and another light beam is guided to the image sensor 22, so that the image sensor 22 captures an image while the image sensor 22 captures an image. It may be configured to perform focus adjustment by the phase difference detection method.

  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 322 ... Focus lens drive motor 33 ... Zoom lens 37 ... Lens Control unit

Claims (5)

A zoom operation detector that detects a zoom operation in which the zoom lens is driven in the optical axis direction;
A focus detection unit capable of detecting a focus state of the optical system at each of a plurality of focus detection positions set at a plurality of positions in an image plane of the optical system;
A target position setting unit that sets a focus detection position for performing focus adjustment among the plurality of focus detection positions as a first target position;
A focus adjustment unit that adjusts the focus of the optical system by driving a focus adjustment lens based on a focus state of the optical system at the first target position;
The target position setting unit, when the first target position at the start of the zoom operation is set outside a predetermined central area including an optical axis among the areas in the photographing screen, A focus detection position for performing focus adjustment during the zoom operation is selected as a second target position from the focus detection positions set in the region;
The focus adjustment unit adjusts the focus of the optical system during the zoom operation based on the focus state of the optical system at the second target position when the second target position is selected during the zoom operation. An imaging apparatus characterized by performing The imaging device according to claim 1,
The target position setting unit is a focus detection position set in the central region when the second target position is selected, and the position of the subject image plane at the focus detection position is the first target position. An imaging apparatus, wherein a focus detection position that is within a range of three times the focal depth of the optical system is selected as the second target position with respect to the position of the image plane of the subject at the position. The imaging device according to claim 1 or 2,
The target position setting unit, when the focus detection position for performing the focus adjustment during the zoom operation is changed from the first target position to the second target position, when the zoom operation ends, An imaging apparatus, wherein a focus detection position for performing focus adjustment is returned to the first target position at the start of the zoom operation. In the imaging device in any one of Claims 1-3,
An imaging unit having a plurality of imaging pixels and a plurality of focus detection pixels, capturing an image by the optical system, and outputting an image signal corresponding to the captured image;
The focus detection unit performs focus detection by a phase difference detection method by detecting a shift amount of an image plane by the optical system based on an image signal output from the focus detection pixel. apparatus. In the imaging device in any one of Claims 1-3,
An imaging unit that captures an image by the optical system and outputs an image signal corresponding to the captured image;
A light-receiving unit that is a member independent of the imaging unit and that receives a pair of light beams that pass through different regions of the pupil of the optical system and outputs a pair of light-receiving signals;
The focus detection unit performs focus detection by a phase difference detection method by detecting a shift amount of an image plane by the optical system based on a pair of light reception signals output from the light reception unit. Imaging device.

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