JP2013015807A - Focus detector and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detector capable of excellently detecting a focus state of an optical system.SOLUTION: The focus detector comprises: an imaging section 22 for imaging an image by the optical system and outputting an image signal corresponding to the picked-up image; a light receiving section 22 including a line-shaped light receiving sensor receiving a pair of light fluxes via the optical system to output a pair of signals for detecting a focus; a recognition section 21 for recognizing the position of an image corresponding to a reference image equivalent to an object image as the position of a specific subject on the basis of an image signal outputted from the imaging section 22; a specifying section 21 for specifying a position corresponding to the position of the specific subject in the light receiving sensor as a corresponding sensor portion to be used for detecting a focus; and a focus detection section 21 for detecting the focus state of the optical system by detecting deviation amount of an image surface by the optical system on the basis of a pair of signals for detecting a focus outputted from the corresponding sensor portion.

Description

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

  Conventionally, a light receiving unit having a light receiving sensor for focus detection and an image sensor for taking an image are separately provided separately, and an optical system based on a pair of focus detection signals output from the light receiving sensor. A technique for detecting the focal state of an optical system by detecting the amount of image plane displacement due to the above is known (for example, Patent Document 1).

JP 2001-174692 A

  However, in the prior art, since the light receiving unit having the light receiving sensor for focus detection and the image sensor for taking an image are provided independently, the light receiving surface of the light receiving unit with respect to the optical axis direction due to an adjustment error. And the orientation of the imaging surface of the imaging device with respect to the optical axis direction may not match. In such a case, focus detection accuracy may be reduced.

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

  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] A focus detection apparatus according to the present invention captures an image by an optical system and outputs an image signal corresponding to the captured image, and receives a pair of light beams via the optical system. And a light receiving unit (22) having a line-shaped light receiving sensor (22a to 22e) for outputting a pair of focus detection signals, and the image signal output from the imaging unit corresponds to a target image. A recognition unit (21) that recognizes the position of the image corresponding to the reference image as the position of the specific subject, and a position corresponding to the position of the specific subject in the light receiving sensor as a corresponding sensor part for use in focus detection The focus state of the optical system is determined by detecting the amount of displacement of the image plane by the optical system based on the specifying unit (21) to be specified and the pair of focus detection signals output from the corresponding sensor part. detection That focus detection unit (21), characterized in that it comprises a.

  [2] In the invention relating to the focus detection device, the specifying unit (21) may be configured such that the corresponding sensor portion has a length corresponding to a width of the specific subject in the length direction of the light receiving sensors (22a to 22e). It can be configured to be specific.

  [3] In the invention relating to the focus detection apparatus, the specifying unit (21) may be configured to specify the corresponding sensor portion so as to be symmetrical about the center position of the specific subject.

  [4] In the invention according to the focus detection apparatus, the specifying unit (21) may determine the position of the specific subject when the position of the specific subject moves in the length direction of the light receiving sensors (22a to 22e). The corresponding sensor portion can be configured to move in response to the movement.

  [5] In the invention relating to the focus detection device, the light receiving sensors (22a to 22e) are configured by a plurality of focus detection pixels (222a and 222b) arranged in a line, and the specifying unit (21 ) Can be configured to change the focus detection pixels used for focus detection according to the position of the specific subject.

  [6] In the invention related to the focus detection apparatus, the specifying unit (21) changes the number of the focus detection pixels (222a, 222b) used for focus detection according to the size of the specific subject. Can be configured.

  [7] In the invention related to the focus detection apparatus, the light receiving unit (22) includes a plurality of the light receiving sensors (22a to 22e) arranged along a direction perpendicular to the length direction of the light receiving sensor. The specifying unit (21) selects a light receiving sensor closest to the center position of the specific subject among the plurality of light receiving sensors as a light receiving sensor used for focus detection, and the specific subject in the selected light receiving sensor is selected. A position corresponding to this position can be specified as the corresponding sensor portion.

  [8] In the invention relating to the focus detection apparatus, the specifying unit (32) may be configured such that the position of the specific subject does not overlap any of the plurality of light receiving sensors (22a to 22e) and is adjacent to the specific light receiving sensor (22a to 22e). When located between the light receiving sensors, among the plurality of light receiving sensors excluding the light receiving sensor located vertically above the position of the specific subject, the light receiving sensor closest to the center position of the specific subject Can be selected as the light receiving sensor used for focus detection.

  [9] In the invention related to the focus detection device, the specifying unit (21) may detect the specific subject when the position of the specific subject moves in the arrangement direction of the plurality of light receiving sensors (22a to 22e). The light receiving sensor used for focus detection can be changed in accordance with the movement of the position.

  [10] In the invention related to the focus detection device, the specifying unit (21) focuses the plurality of light receiving sensors when the position of the specific subject extends over the plurality of light receiving sensors (22a to 22e). A light receiving sensor used for detection may be selected, and a position corresponding to the position of the specific subject in the selected light receiving sensor may be specified as the corresponding sensor portion.

  [11] In the invention relating to the focus detection apparatus, the light receiving unit (22) includes a plurality of the light receiving sensors (22a to 22e) arranged along a direction perpendicular to a length direction of the light receiving sensor. The specifying unit (21) selects, from among the plurality of light receiving sensors, a light receiving sensor that is positioned below the center position of the specific subject as a light receiving sensor used for focus detection, and selects the selected light receiving sensor. A position corresponding to the position of the specific subject in the light receiving sensor can be specified as the corresponding sensor portion.

  [12] In the invention related to the focus detection apparatus, the light receiving sensors (22a to 22e) may be configured to be provided on a light receiving surface of the imaging unit (22).

  [13] An imaging apparatus according to the present invention includes the focus detection apparatus.

  According to the present invention, the focus state of the optical system can be detected satisfactorily.

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 vicinity of 22a in 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 diagram for explaining a method of specifying a focus detection portion for use in focus detection. FIG. 10 is a diagram for explaining a method of performing focus detection in a preset focus detection area. FIG. 11 is a diagram for explaining a method of changing the number of focus detection pixels 222a and 222b used for focus detection according to the size of a specific subject. FIG. 12 is a diagram illustrating an example of a scene in which the position of the specific subject extends over a plurality of focus detection pixel rows. FIG. 13 is a diagram illustrating an example of a scene in which the position of the specific subject does not overlap with any of the plurality of focus detection pixel rows.

  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 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. Adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending the aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the aperture diameter corresponding to the set aperture value 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.

  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 memory 24 that is a recording medium. As the memory 24, any of a removable card type memory and a built-in type memory can be used. An infrared cut filter for cutting infrared light and an optical low-pass filter for preventing image aliasing noise are disposed in front of the imaging surface of the image sensor 22. 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 37 through an electric signal contact unit 41 provided in the mount unit 4, receives lens information from the lens control unit 37, and defocuses to the lens control unit 37. Send information such as volume and aperture diameter. 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 photographing optical system by the phase detection method based on the pixel data read from the image sensor 22. A specific focus state detection method will be described later.

  The operation unit 28 is a shutter release button or an input switch for the user to set various operation modes of the camera 1, and can switch between an autofocus 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 element 22, and FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the vicinity of the focus detection pixel row 22a in 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.

  Further, on the imaging surface of the imaging element 22, five focus detection pixel rows 22a to 22e in which focus detection pixels 222a and 222b are arranged instead of the above-described imaging pixel 221 are provided. These focus detection pixel columns 22a to 22e are arranged along a direction perpendicular to the length direction of the focus detection pixel columns 22a to 22e, as shown in FIG. As shown in FIG. 3, one focus detection pixel column is configured by a plurality of focus detection pixels 222 a and 222 b being alternately arranged adjacent to each other in a horizontal row. 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 22e shown in FIG. 2 are not limited to the illustrated positions, and may be any one, two, three, or four locations, and more than six locations. It can also be arranged at the position. FIG. 3 shows an example in which the focus detection pixel array is configured by 16 focus detection pixels 222a and 222b, but the number of focus detection pixels configuring the focus detection pixel array is limited to this example. Is not to be done.

  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 22e 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 341 and 342 of the exit pupil 34 are received, respectively. 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 341 and 342 are respectively received.

  Here, the exit pupil 34 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 341 and 342 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 341, 342.

  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 34 separated from the lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 by the distance measurement distance D, and the projection shape forms the distance measurement pupils 341, 342.

  In other words, on the exit pupil 34 at the distance measurement distance D, the microlens and the photoelectric conversion unit in each focus detection pixel so that the projection shapes (the distance measurement pupils 341 and 342) of the photoelectric conversion unit of each focus detection pixel match. 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 341 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 341, 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 342, 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 342, 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 line shape as shown in FIG. Of the pair of images formed on the focus detection pixel row by the focus detection light fluxes that pass through each of the distance measurement pupil 341 and the distance measurement pupil 342. 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 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). The deviation of the focal plane at the detection position, 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.

  In this embodiment, the camera control unit 21 recognizes a specific subject in the captured image, and the position of the recognized specific subject among the focus detection pixels 222a and 222b constituting the focus detection pixel rows 22a to 22e. Based on the outputs of the focus detection pixels 222a and 222b corresponding to the above, the above-described calculation of the image shift amount and the calculation of the defocus amount based on this are performed.

  Specifically, the camera control unit 21 first compares the template image data (reference image data) stored in the memory included in the camera control unit 21 with the captured image captured by the image sensor 22 and determines the captured image. Image recognition processing for detecting the position of the specific subject from the inside is performed. For example, in the present embodiment, image data of a person's face is compared with a captured image captured by the image sensor 22 as template image data, thereby recognizing the person's face in the captured image as a specific subject. The specific subject is not limited to a human face, and for example, an animal face may be detected as the specific subject.

  The camera control unit 21 uses the focus detection pixels 222a and 222b corresponding to the position of the specific subject among the focus detection pixels 222a and 222b constituting the focus detection pixel rows 22a to 22e for focus detection. Identify as part. Here, FIG. 9 is a diagram for explaining a method of specifying the focus detection portion. In the following, with reference to FIG. 9, a method for specifying a focus detection portion will be described in detail. In the following description, it is assumed that a human face is detected as a specific subject as shown in FIG.

  First, the camera control unit 21 detects the center coordinates of a specific subject on the image sensor 22 based on the result of the image recognition process. For example, in the example shown in FIG. 9, the center coordinates of the face area of a person recognized as a specific subject are detected.

  And the camera control part 21 selects the focus detection pixel row | line | column used for focus detection from several focus detection pixel row | line | columns 22a-22e based on the detected center coordinate of the specific subject. Specifically, the camera control unit 21 selects a focus detection pixel row that is closest to the center coordinates of the specific subject in the arrangement direction of the focus detection pixel rows 22a to 22e among the plurality of focus detection pixel rows 22a to 22e. Are selected as a focus detection pixel array used for focus detection. For example, in the example shown in FIG. 9, since the focus detection pixel row 22a is located closest to the center coordinates of the specific subject, the camera control unit 21 uses the focus detection pixel row 22a of the specific subject for focus detection. Select as a pixel row for detection.

  Next, as shown in FIG. 9, the camera control unit 21 selects the focus detection pixels 222a and 222b corresponding to the position of the specific subject among the focus detection pixels 222a and 222b constituting the selected focus detection pixel row. It is specified as a focus detection portion for use in focus detection. In the present embodiment, the camera control unit 21 sets the width of the focus detection portion to the length of the focus detection pixel rows 22a to 22e as shown in FIG. 9 so that focus detection can be performed at a position corresponding to the specific subject. The width direction of the specific subject is specified so as to be substantially the same as the width of the specific subject in the vertical direction, and the focus detection portion is specified so as to be symmetric with respect to the center coordinates of the specific subject.

  Then, the camera control unit 21 calculates the image shift amount based on the output of the identified focus detection portion, and calculates the defocus amount based on the calculated image shift amount. For example, in the example shown in FIG. 9, among the focus detection pixels 222a and 222b constituting the focus detection pixel row 22a, the focus detection pixels 222a and 222b corresponding to the position of the specific subject are specified as the focus detection portion. An image shift amount is calculated based on the output of the focus detection portion, and a defocus amount is calculated based on the calculated image shift amount.

  In the present embodiment, the position of the specific subject is repeatedly recognized by the image recognition processing, and the position corresponding to the position of the specific subject among the focus detection pixels 222a and 222b constituting the focus detection pixel rows 22a to 22e is the focus. It is repeatedly identified as a focus detection part for use in detection. Therefore, for example, when the position of the specific subject moves along the arrangement direction of the focus detection pixel rows 22a to 22e, the focus detection pixel row used for focus detection corresponds to the movement of the position of the specific subject. The defocus amount is calculated based on the output of the focus detection pixel row corresponding to the position of the specific subject. Further, when the specific subject moves along the length direction of the focus detection pixel rows 22a to 22e, the focus detection portion used for focus detection also moves according to the movement of the position of the specific subject, The defocus amount is calculated based on the outputs of the focus detection pixels 222a and 222b corresponding to the position of the specific subject.

  When the specific subject is moving in the optical axis direction of the camera 1, the size of the specific subject changes. In such a case, the camera control unit 21 changes the number of focus detection pixels 222a and 222b used for focus detection according to the size of the specific subject. Here, FIG. 10 is a diagram for explaining a method of changing the number of focus detection pixels 222a and 222b used for focus detection according to the size of the specific subject. FIG. 10A is an enlarged view of the vicinity of the focus detection portion shown in FIG. 9, and FIG. 10B shows the specific subject facing the camera 1 in the scene example shown in FIG. It is a figure which shows an example of the position of the specific subject at the time of moving. 10A and 10B, only the focus detection pixels 222a and 222b constituting the focus detection pixel row 22a are shown, and the description of the imaging pixel 221 is omitted.

  For example, in the example shown in FIG. 10A, the camera control unit 21 uses ten focus detection pixels 222a and 222b corresponding to the position of the specific subject for focus detection according to the size of the specific subject. Is specified as the focus detection part. On the other hand, in the example shown in FIG. 10B, since the specific subject is larger than the example shown in FIG. 10A, the camera control unit 21 detects the specific subject in the length direction of the focus detection pixel row. Corresponding to the width, the 14 focus detection pixels 222a and 222b are specified as focus detection portions for use in focus detection. Thus, in this embodiment, when the size of the specific subject changes, the number of focus detection pixels for focus detection is changed according to the size of the specific subject, and the size of the specific subject is changed. A corresponding focus detection portion is identified.

  The width of the focus detection part is preferably set to a width that can appropriately detect the image shift amount in the above-described image shift amount calculation. For example, as shown in FIGS. 10A and 10B, when the camera control unit 21 calculates the image shift amount, the correlation amount between the pair of output signals output from the focus detection pixels 222a and 222b is calculated. The width of the focus detection portion can be made longer by a predetermined number of focus detection pixels than the width of the specific subject in the length direction of the focus detection pixel row so as to increase.

  Then, the camera control unit 21 calculates the image shift amount based on the output of the identified focus detection portion, and calculates the defocus amount based on the calculated image shift amount. Then, the camera control unit 21 calculates a lens driving amount necessary to drive the focus lens 32 to the in-focus position based on the calculated defocus amount, and the calculated lens driving amount is supplied to the lens control unit 37. To the focus lens drive motor 36. Thereby, the lens driving amount is acquired by the focus lens driving motor 36, and the focus lens 32 is driven based on the acquired lens driving amount.

  As described above, in the present embodiment, the imaging element 22 includes the plurality of focus detection pixel arrays 22a to 22e, and performs focus detection from the plurality of focus detection pixel arrays 22a to 22e according to the position of the specific subject. A focus detection pixel row to be used is selected, and a position corresponding to the position of the specific subject in the selected focus detection pixel row is specified as a focus detection portion for use in focus detection. Then, the focus state of the optical system is detected based on the pair of focus detection signals output from the specified focus detection part. Thus, in the present embodiment, when focus detection is performed by the phase difference detection method, focus detection can be performed based on the outputs of the focus detection pixels 222a and 222b corresponding to the position of the specific subject. It is possible to satisfactorily detect the focus state of the optical system corresponding to the above.

  On the other hand, as shown in FIG. 11, a plurality of focus detection areas AFP are set in advance in the shooting screen, and a focus detection area for performing focus detection is selected from these focus detection areas and selected. When detecting the focus state of the optical system in the focus detection area, the position of the specific subject and the position of the selected focus detection area are greatly shifted, and the focus state of the position with respect to the specific subject is detected appropriately. In some cases, the focus detection accuracy is reduced. For example, as shown in FIG. 11, even when the focus detection area AFP where the center coordinates of the specific subject are located is selected as the focus detection area AFP for performing focus detection, the specific subject is compared with the example shown in FIG. And the position of the selected focus detection area AFP are largely deviated from each other, the focus state at the position corresponding to the specific subject may not be detected properly. In addition, there is a case where the other subject existing in the focus detection area AFP for performing focus detection is focused and the specific subject is not focused.

  On the other hand, in the present embodiment, as shown in FIG. 9, since the focus detection portion for use in focus detection can be specified according to the position of the specific subject, the focus at the position corresponding to the specific subject. The state can be detected appropriately, and the focus detection accuracy can be improved. In particular, in the present embodiment, the width of the focus detection portion is specified corresponding to the width of the specific subject, and the focus detection portion is specified to be symmetric with respect to the center coordinates of the specific subject. The focus detection at the position corresponding to the subject can be performed more appropriately. Further, by detecting the focus detection pixel row closest to the center coordinates of the specific subject among the plurality of focus detection pixel rows 22a to 22e as the focus detection pixel row for performing focus detection, Since the position of the focus detection portion for performing focus detection can be made closer, the focus state at the position corresponding to the specific subject can be detected better.

  Furthermore, in this embodiment, focus detection pixel rows 22a to 22e for performing focus detection by the phase difference detection method are provided in the image sensor 22, and based on outputs of the focus detection pixel rows 22a to 22e provided in the image sensor 22. By detecting the focus state of the optical system, the following effects can be obtained. That is, when the focus detection module that detects the focus state by the phase difference detection method is provided independently of the image sensor 22 as in the prior art, the orientation of the light receiving surface of the focus detection module with respect to the optical axis direction When the orientation of the imaging surface of the imaging element 22 with respect to the optical axis direction does not match, the focus detection accuracy may be reduced. In addition, since a dedicated focus detection module is provided, the manufacturing cost may be high, or the camera 1 may not be downsized. On the other hand, in the present embodiment, since the imaging element 22 includes the focus detection pixel rows 22a to 22e for performing focus detection, such a problem can be effectively solved.

  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 specific subject is detected by the image recognition processing, but the configuration is not limited to this configuration. For example, when a tracking operation is performed, the target is a tracking target. The subject may be detected as a specific subject. In the above-described embodiment, in order to focus on a person's face, a focus detection part to be used for focus detection is specified based on the center coordinates of the person's face area. When it is desired to focus on the subject, the coordinates of the person's eyes may be predicted from the center coordinates of the person's face area, and the focus detection portion may be specified based on the coordinates of the person's eyes.

  In the embodiment described above, as shown in FIG. 9, among the plurality of focus detection pixel rows 22 a to 22 e, the focus detection pixel rows 22 a to 22 e are positioned closest to the center coordinates of the specific subject in the arrangement direction of the focus detection pixel rows 22 a to 22 e. The focus detection pixel row is selected as the focus detection pixel row for performing focus detection, and the position corresponding to the position of the specific subject in the selected focus detection pixel row is specified as the focus detection portion. As shown in FIG. 12, when a specific subject extends over a plurality of focus detection pixel rows, a plurality of focus detection pixel rows corresponding to the position of the specific subject are selected as focus detection pixel rows for performing focus detection. The position corresponding to the position of the specific subject in the selected focus detection pixel array may be specified as the focus detection portion. For example, in the example shown in FIG. 12, since the position of the specific subject extends over the focus detection pixel row 22a and the focus detection pixel row 22b, the position corresponding to the position of the specific subject in the focus detection pixel row 22a is the focus. In addition to being specified as the detection portion, the position corresponding to the position of the specific subject in the focus detection pixel row 22b is also specified as the focus detection portion. Then, an image shift amount is calculated based on the output of the focus detection portion in the focus detection pixel row 22a and the output of the focus detection portion in the focus detection pixel row 22b, and defocusing is performed based on the calculated image shift amount. It is good also as a structure which calculates quantity. In such a case, the defocus amount calculated based on the output of the focus detection portion in the focus detection pixel array 22a and the defocus calculated based on the output of the focus detection portion in the focus detection pixel array 22b. The defocus amount for driving the focus lens 32 may be calculated based on the average value with the amount, or the defocus calculated based on the output of the focus detection portion in the focus detection pixel row 22a. The weight and the defocus amount calculated based on the output of the focus detection portion in the focus detection pixel row 22b are weighted according to the distance from the focus detection pixel rows 22a and 22b to the center coordinates of the specific subject, and weighted. The defocus amount for driving the focus lens 32 is calculated based on the average value of the defocus amounts. It may be formed. FIG. 12 is a diagram illustrating an example of a scene in which the position of the specific subject extends over a plurality of focus detection pixel rows.

  Furthermore, when the position of the specific subject does not overlap with the focus detection pixel rows 22a to 22e and the position of the specific subject is located between adjacent focus detection pixel rows, the focus detection on the upper side in the vertical direction is performed. Of the plurality of focus detection pixel rows excluding the pixel row, the focus detection pixel closest to the center coordinate of the specific subject can be selected as the focus detection pixel row for performing focus detection. For example, in the example shown in FIG. 13, the specific subject does not overlap any of the focus detection pixel rows 22a to 22e, and the specific subject is located between the adjacent focus detection pixel rows 22a and 22b. . In this case, for example, the camera control unit 21 detects the vertical direction using a posture sensor (not shown), and identifies the focus detection pixel rows 22b to 22e excluding the focus detection pixel row 22a arranged on the upper side in the vertical direction. The focus detection pixel row 22b closest to the center coordinates of the subject is selected as a focus detection pixel row for focus detection, and the position corresponding to the specific subject in the focus detection pixel row 22b is specified as a focus detection portion, The focus state is detected. In this case, even when the specific subject does not exist at the position corresponding to the focus detection pixel rows 22a to 22e, for example, when the specific subject is a person's face or the like, focus detection is performed corresponding to the chest or torso of the person. Therefore, it is possible to appropriately detect an image focused on a specific subject.

  In the above-described embodiment, the focus detection pixel row arranged at the position closest to the center position of the specific subject is selected as the focus detection pixel row for performing focus detection. However, the present invention is not limited to this configuration. For example, a configuration may be adopted in which a focus detection pixel row arranged on the lower side in the vertical direction than the position of the specific subject is selected as a focus detection pixel row for performing focus detection. For example, in the example illustrated in FIG. 13, the camera control unit 21 detects the vertical direction using a posture sensor (not shown), and 1 out of the focus detection pixel rows 22 b to 22 e positioned below the specific subject in the vertical direction. One or more focus detection pixel arrays 22b to 22e are selected as focus detection pixel arrays for focus detection, and a position corresponding to the position of a specific subject in the selected focus detection pixel array is used for focus detection. It can be specified as a detection part. In this case, all the focus detection pixel rows 22b to 22e arranged on the lower side in the vertical direction than the position of the specific subject may be selected as focus detection pixel rows for performing focus detection. Alternatively, for example, the focus detection pixel row 22c arranged at the second closest position from the center position of the specific subject among the focus detection pixel rows arranged below the specific subject in the vertical direction is subjected to focus detection. You may select as a focus detection pixel row | line for performing. For example, when the specific subject is a person's face, the focus detection pixel array arranged closest to the center position of the specific subject is located at the neck portion of the person with relatively low contrast, and the focus state May not be detected properly, but a plurality of focus detection pixel rows arranged below the position of the specific subject, or a focus detection pixel row arranged, for example, at a position closest to the center position of the specific subject. Can be selected as a focus detection pixel row for performing focus detection, for example, focus detection can be performed at a position corresponding to a torso portion of a person with relatively high contrast, and the focus state is detected appropriately. be able to.

  Furthermore, in the above-described embodiment, a specific subject is recognized, and the position corresponding to the recognized position of the specific subject in the focus detection pixel rows 22a to 22e is specified as a focus detection portion, and output to the specified focus detection portion. Based on the configuration for performing focus detection based on the above, for example, when the specific subject does not exist in the shooting screen and the specific subject cannot be recognized, the focus detection area is set in advance. A focus detection area for performing focus detection may be selected, and focus detection may be performed in the selected focus detection area.

  In the above-described embodiment, the configuration in which focus detection is performed by the phase difference detection method based on the outputs of the focus detection pixels 222a and 222b is illustrated. However, in addition to this, the focus state of the optical system by the contrast detection method is illustrated. It is good also as a structure which performs a detection. Specifically, 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. Then, while driving the focus lens 32 at a predetermined sampling interval (distance), a focus evaluation value at each lens position is obtained, and a position of the focus lens 32 at which the focus evaluation value is maximized is obtained as a focus position. It may be configured to detect the focus state of the optical system. In this case, when the focus state cannot be detected by the phase difference detection method, the focus detection may be performed by the contrast detection method. Alternatively, the focus detection by the phase difference detection method and the focus detection by the contrast detection method may be used. It is good also as a structure which performs simultaneously.

  In the above-described embodiment, the focus detection pixels 222a and 222b of the image sensor 22 are exemplified by the configuration for detecting the focus state by the phase difference detection method. However, the configuration is not limited to this configuration, and the phase difference detection is performed. A focus detection module that detects the focus state by the method may be provided independently of the image sensor 22.

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

DESCRIPTION OF SYMBOLS 1 ... Digital camera 2 ... Camera body 21 ... Camera control part 22 ... Imaging device 221 ... Imaging pixel 222a, 222b ... Focus detection pixel 24 ... Memory 28 ... Operation part 3 ... Lens barrel 32 ... Focus lens 36 ... Focus lens drive motor 37 ... Lens control unit

Claims (13)

An imaging unit that captures an image by an optical system and outputs an image signal corresponding to the captured image;
A light receiving unit having a line-shaped light receiving sensor that receives a pair of light fluxes via the optical system and outputs a pair of focus detection signals;
A recognition unit that recognizes a position of an image corresponding to a reference image corresponding to a target image based on the image signal output from the imaging unit as a position of a specific subject;
A specifying unit that specifies a position corresponding to the position of the specific subject in the light receiving sensor as a corresponding sensor part for use in focus detection;
A focus detection unit that detects a focus state of the optical system by detecting a shift amount of the image plane by the optical system based on the pair of focus detection signals output from the corresponding sensor part. A focus detection apparatus. The focus detection apparatus according to claim 1,
The focus detection apparatus characterized in that the specifying unit specifies the corresponding sensor portion with a length corresponding to a width of the specific subject in a length direction of the light receiving sensor. The focus detection apparatus according to claim 1 or 2,
The focus detection apparatus characterized in that the specifying unit specifies the corresponding sensor portion so as to be symmetric with respect to a center position of the specific subject. The focus detection apparatus according to claim 1,
The focus detection unit is configured to move the corresponding sensor portion according to the movement of the position of the specific subject when the position of the specific subject moves in the length direction of the light receiving sensor. apparatus. The focus detection device according to any one of claims 1 to 4,
The light receiving sensor is composed of a plurality of focus detection pixels arranged in a line,
The focus detection apparatus, wherein the specifying unit changes the focus detection pixels used for focus detection according to a position of the specific subject. The focus detection apparatus according to claim 5,
The focus detection device, wherein the specifying unit changes the number of focus detection pixels used for focus detection according to the size of the specific subject. The focus detection apparatus according to any one of claims 1 to 6,
In the light receiving section, a plurality of the light receiving sensors are arranged along a direction perpendicular to the length direction of the light receiving sensors,
The specifying unit selects a light receiving sensor closest to the center position of the specific subject as the light receiving sensor used for focus detection among the plurality of light receiving sensors, and corresponds to the position of the specific subject in the selected light receiving sensor. A focus detection apparatus that identifies a position as the corresponding sensor portion. The focus detection apparatus according to claim 7,
When the position of the specific subject does not overlap any of the plurality of light receiving sensors and is positioned between the adjacent light receiving sensors, the specifying unit is more vertical than the position of the specific subject. A focus detection apparatus, wherein a light reception sensor closest to a center position of the specific subject is selected as a light reception sensor used for focus detection among the plurality of light reception sensors excluding the light reception sensor positioned on the upper side in the direction. The focus detection apparatus according to claim 7 or 8,
The specifying unit changes a light receiving sensor used for focus detection according to the movement of the position of the specific subject when the position of the specific subject moves in an arrangement direction of the plurality of light receiving sensors. Focus detection device. It is a focus detection apparatus in any one of Claims 7-9,
When the position of the specific subject spans a plurality of the light receiving sensors, the specifying unit selects the plurality of light receiving sensors as light receiving sensors used for focus detection, and the specific light receiving sensor in the selected light receiving sensor selects the specific subject. A focus detection apparatus that identifies positions corresponding to positions as the corresponding sensor portions. The focus detection apparatus according to any one of claims 1 to 6,
In the light receiving section, a plurality of the light receiving sensors are arranged along a direction perpendicular to the length direction of the light receiving sensors,
The specifying unit selects a light receiving sensor positioned vertically below a center position of the specific subject among the plurality of light receiving sensors as a light receiving sensor used for focus detection, and the selected light receiving sensor includes: A focus detection apparatus that specifies a position corresponding to the position of a specific subject as the corresponding sensor portion. It is a focus detection apparatus in any one of Claims 1-11,
The focus detection device, wherein the light receiving sensor is provided on a light receiving surface of the imaging unit.   An imaging device comprising the focus detection device according to claim 1.

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