JP2013057839A - Focus detector and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detector capable of properly performing focus detection of an optical system.SOLUTION: A focus detector includes: an imaging part 22 having imaging pixels for inputting an image signal corresponding to an image imaged by an optical system and a pair of pixel columns for focus detection receiving a pair of light fluxes subjected to the pupil division; a diaphragm 34 which restricts light flux made incident on the imaging part 22; a phase difference detection part for performing a shift operation for calculation of a correlation amount for all of a predetermined shift range, while one-dimensionally and relatively shifting a first data column and a second data column outputted from the pair of pixel columns for focus detection, respectively, and detecting a shift amount by which an extreme value of the correlation amount is obtained, thus detecting a focus state; and a setting part for setting an effective shift range for obtaining the extreme value of the correlation amount corresponding to a diaphragm value. The phase difference detection part detects the shift amount by which the extreme value of the correlation amount is obtained, by using the calculation result in the effective shift range among the shift calculation result performed for all of the predetermined shift range.

Description

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

  Conventionally, the imaging device includes a pair of focus detection pixel rows, and the first data row and the second data row output from the pair of focus detection pixel rows are relatively shifted. A focus detection device is known that calculates a defocus amount based on a shift amount by which a correlation amount with a second data string is calculated and an extreme value of the correlation amount is obtained (for example, Patent Document 1).

JP 2011-90143 A

  However, in the conventional technique, the correlation amount is calculated while relatively shifting the first data sequence and the second data sequence for the entire range of the predetermined shift range, and the correlation amount calculated over the entire range of the predetermined shift range is obtained. Since the extremum of the correlation amount is calculated based on this, and the defocus amount is calculated from the shift amount corresponding to the calculated extremum, depending on the aperture value of the aperture provided in the optical system, the false focus is obtained. There was a problem that.

  The problem to be solved by the present invention is to provide a focus detection apparatus capable of appropriately performing focus detection of an optical system.

  The present invention solves the above problems by the following means. In the following description, the reference numerals corresponding to the drawings showing the embodiments of the present invention are used for explanation, but these reference numerals are only for facilitating the understanding of the present invention and are not intended to limit the invention. Absent.

  [1] A focus detection apparatus according to the present invention captures an image by an optical system including a focus adjustment optical system (32), outputs an image signal corresponding to the captured image, and pupil division. An imaging unit (22) having a pair of focus detection pixel rows (22a, 22b, 22c) for receiving the pair of light fluxes, and an aperture that restricts the light flux that passes through the optical system and enters the imaging unit (34) and the first data row and the second data row while relatively shifting the first data row and the second data row respectively output from the pair of focus detection pixel rows in a one-dimensional manner. By performing a shift operation for calculating the correlation amount between the columns over a predetermined range of a predetermined shift range, and detecting a shift amount from which the extreme value of the correlation amount is obtained based on the shift calculation result , The focus state of the optical system A phase difference detection unit (21) to be output, and a setting unit (21) for setting an effective shift range for obtaining the extreme value of the correlation amount corresponding to the aperture value based on the aperture value by the aperture; The phase difference detection unit uses the calculation result in the effective shift range corresponding to the aperture value of the diaphragm among the shift calculation results performed for the entire predetermined shift range, and the extreme value of the correlation amount is The obtained shift amount is detected.

  [2] In the focus detection apparatus of the present invention, the focus adjustment of the optical system is driven by driving the focus adjustment optical system (32) in the optical axis direction based on the detection result of the focus state by the phase difference detection unit. And the phase difference detection unit (21) drives the focus adjustment optical system with the focus adjustment unit. As a result, the focus adjustment optical system includes a focus position. When it can be determined that the position is in the vicinity of the in-focus position, instead of performing a shift operation for the entire predetermined shift range, the calculation of the correlation amount is started from the smallest absolute value of the shift amount, While sequentially increasing the absolute value of the shift amount, the calculation of the correlation amount and the detection of the shift amount that obtains the extreme value of the correlation amount are performed sequentially, and the shift amount that obtains the extreme value of the correlation amount is detected. Is In this case, when a shift amount at which the extreme value of the correlation amount is obtained is detected, the calculation of the correlation amount is terminated, and based on the shift amount from which the extreme value of the correlation amount is obtained, the optical system The focus state can be detected.

  [3] In the focus detection apparatus of the present invention, as a result of the phase difference detection unit (21) driving the focus adjustment optical system (32) by the focus adjustment unit (36), the focus adjustment optical system is When it can be determined that the position is in the vicinity of the in-focus position including the in-focus position, the calculation of the correlation amount and the extreme value of the correlation amount are obtained in the effective shift range set by the setting unit (21). The shift amount can be detected.

  [4] In the focus detection apparatus of the present invention, the setting unit (21) can be configured such that the effective shift range is made smaller as the aperture value by the aperture (34) is larger.

  [5] In the focus detection apparatus of the present invention, the evaluation value relating to the contrast of the image by the optical system is calculated based on the image signal output from the imaging pixel (221), thereby the focus of the optical system. It can comprise so that the contrast detection part (21) which detects a state may be further provided.

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

  According to the present invention, focus detection of an optical system can be performed appropriately.

FIG. 1 is a block diagram showing a camera according to the present embodiment. FIG. 2 is a front view showing an imaging surface of the imaging device shown in FIG. FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the III part of FIG. FIG. 4 is an enlarged front view showing one of the imaging pixels 221. FIG. 5A is an enlarged front view showing one of the focus detection pixels 222a, and FIG. 5B is an enlarged front view showing one of the focus detection pixels 222b. FIG. 6 is an enlarged cross-sectional view showing one of the imaging pixels 221. FIG. 7A is an enlarged cross-sectional view showing one of the focus detection pixels 222a, and FIG. 7B is an enlarged cross-sectional view showing one of the focus detection pixels 222b. 8 is a cross-sectional view taken along line VIII-VIII in FIG. FIG. 9 is a flowchart (part 1) showing the calculation processing of the image shift amount by the phase difference detection method in the camera 1 according to the present embodiment. FIG. 10 is a flowchart (part 2) illustrating the image shift amount calculation processing by the phase difference detection method in the camera 1 according to the present embodiment. FIG. 11A is a diagram showing an example of the relationship between the exit pupil and the distance measurement pupil of the focus detection pixel when the aperture value is F2.8, and FIG. 8 is a graph showing an example of signal strengths of a first data string and a second data string when the number is 8. FIG. FIG. 12A is a diagram showing an example of the relationship between the exit pupil and the distance measurement pupil of the focus detection pixel when the aperture value is F5.6, and FIG. 6 is a graph showing an example of signal intensities of a first data string and a second data string in the case of 6. FIG.

  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. The adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 37 by a manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the aperture 34 is detected by an aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

  The lens control unit 37 is electrically connected to the camera control unit 21 by an electric signal contact unit 41 provided on the mount unit 4, and is driven by the focus lens 32 and opened by the diaphragm 34 based on a command from the camera control unit 21. In addition to adjusting the aperture, lens information such as the position of the focus lens 32 and the aperture diameter of the diaphragm 34 is transmitted to the camera control unit 21.

  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 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 a shutter release button or an input switch for the user to set various operation modes of the camera 1. Switching between the autofocus mode / manual focus mode and the one-shot mode / continuous mode is also possible in the autofocus mode. The as mode can be switched. Here, the one-shot mode is a mode in which the position of the focus lens 32 once adjusted is fixed and photographing is performed at the focus lens position, whereas the continuous mode is a mode in which the position of the focus lens 32 is fixed. In this mode, the focus lens position is adjusted according to the subject. 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 image sensor 22, and FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the III part of FIG.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  Then, by converting the obtained image shift amount according to the center-of-gravity distance between the pair of distance measuring pupils, the 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 on the calculation are performed by the camera control unit 21.

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

  Then, the camera control unit 21 sends a control signal to the lens control unit 37 to drive the focus lens 33 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 33 is determined as the in-focus position. Note that this in-focus position is obtained when, for example, the focus evaluation value is calculated while the focus lens 33 is driven, and 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, the calculation process of the image shift amount by the phase difference detection method in the camera 1 according to the present embodiment will be described in more detail with reference to the flowcharts shown in FIGS. Note that the processing described below is started, for example, when the camera 1 is turned on.

  First, in step S <b> 101, the aperture value of the aperture 34 is acquired by the camera control unit 21 via the lens control unit 37.

  Next, in step S102, the camera control unit 21 performs processing for determining an effective shift range based on the aperture value acquired in step S101.

  Here, with reference to FIG. 11 and FIG. 12, the relationship between the aperture value and the shift amount of the pair of data strings will be described. FIG. 11A is a diagram illustrating an example of the relationship between the exit pupil 350 and the focus detection pupils 351 and 352 when the aperture value is F2.8, and FIG. It is a figure which shows an example of the relationship between the exit pupil 35 in case a value is F5.6, and the ranging pupils 351 and 352 of a focus detection pixel. 11A and 12A exemplify a scene where the defocus amount is also 1 mm, for example (scene where the lens position of the focus lens 32 is moving to the in-focus position). In FIGS. 11B and 12B, the horizontal axis indicates the pixel position of each pixel in the focus detection pixel rows 22a, 22b, and 22c.

In the example shown in FIG. 11A, the aperture value is F2.8, and the exit pupil 350 is larger than that in the example shown in FIG. 12A. Therefore, most of the distance measurement pupils 351 and 352 are large. It is included in the exit pupil 350. Therefore, in the example shown in FIG. 11A, the light receiving areas of the distance measuring pupils 351 and 352 included in the exit pupil 350 are also large, and the barycentric position 351a of the light receiving area of the distance measuring pupil 351 (the light receiving area of the distance measuring pupil 351). and position) of the center of gravity, also increases the distance between the centers of gravity L ₁ between the gravity center position 352a of the light receiving area of the range-finding pupils 352 (position of the center of gravity of the light receiving area of the range-finding pupil 352). On the other hand, in the example shown in FIG. 12A, the aperture value is F5.6, which is smaller than that in the example shown in FIG. The light receiving areas of the distance measuring pupils 351 and 352 are also small. Therefore, in the example shown in FIG. 12 (A), also shortens the distance between the centers of gravity _{L 2} between the gravity center position 352a of the light receiving area of the gravity center position 351a and range-finding pupils 352 of the light-receiving region of the range-finding pupils 351.

  FIG. 11B shows the first data sequence output from the focus detection pixels 222a and 222b constituting the pair of focus detection pixel sequences 22a, 22b, and 22c when the aperture value is F2.8. It is a graph which shows an example of the signal strength of a 2nd data sequence. In the example shown in FIG. 11B, a data string based on the output from each focus detection pixel 222a is shown as a first data string, and a data string based on the output from each focus detection pixel 222b is shown as a second data string. .

  Similarly, FIG. 12B shows the first data output from the focus detection pixels 222a and 222b constituting the pair of focus detection pixel rows 22a, 22b, and 22c when the aperture value is F5.6. FIG. 12 is a graph showing an example of signal intensities of a column and a second data column. In FIG. 12B as well, a data column based on an output from each focus detection pixel 222a is represented by a first data column and each focus detection pixel 222b A data string based on the output is shown as a second data string. 11 (A) and 12 (A), both FIG. 11 (B) and FIG. 12 (B) exemplify a scene where the defocus amount is 1 mm, for example.

As shown in FIG. 11B, when the aperture value is F2.8, as shown in FIG. 12B, compared to the case where the aperture value is F5.6, the distance measurement pupils 351 and 352 are different. gravity position 351a of the light receiving region, because the long distance between the centers of gravity L ₁ between 352a, deviation amount W ₁ between the first and second data streams increases. On the other hand, as shown in FIG. 12B, when the aperture value is F5.6, as compared with the case where the aperture value is F2.8 as shown in FIG. 352 gravity position 351a of the light receiving region of is short distance between the centroids _{L 2} between 352a, deviation amount _{W 2} between the first and second data streams is reduced. As described above, even when the defocus amount is the same, the shift amount between the first data string and the second data string differs depending on the aperture value.

  In this case, in the example shown in FIG. 11B, the first data string and the second data string are shifted so that the first data string and the second data string substantially overlap each other. Therefore, compared with the example shown in FIG. 12B, the shift amount for shifting the first data string and the second data string becomes relatively large. That is, even when the defocus amount is the same, when the aperture value is small (when it is on the open side), the first data string and the second data string are compared with when the aperture value is large (when it is on the narrow side). It is necessary to relatively increase the shift amount for shifting the data string.

  Or, conversely, when the aperture value is large (when it is on the narrowing side), the first data sequence and the second data sequence are shifted compared to when the aperture value is small (when it is on the open side). When the shift amount for increasing the amount of shift is increased, the corresponding defocus amount also increases. In such a case, even if the minimum value of the correlation amount is detected, the focus state of the optical system is appropriately detected. For example, there is a high possibility of false focusing.

Therefore, in the present embodiment, in order to solve such a problem, it is effective when calculating the correlation amount while shifting the first data string and the second data string in accordance with the aperture value of the aperture 34. A shift range Sna is set. Specifically, the effective shift range Sna is set based on the following formula (1).
Sna = So × (k1 / k2) (1)
In the above formula (1), So is a reference shift range that is a reference for determining the effective shift range Sna. For example, when the aperture value is F5.6 and the defocus amount is 1 mm, By relatively shifting the one data string and the second data string, a shift range in which a minimum value of the correlation amount between the first data string and the second data string can be obtained can be obtained. Alternatively, So may be a shift range in which a minimum value of the correlation amount between the first data string and the second data string can be obtained when the defocus amount is 5 mm at a predetermined aperture value, for example. it can. In the above equation (1), k1 is a reference shift range among conversion coefficients (conversion coefficients will be described later) for converting a shift amount that provides a minimum value of the correlation amount into a defocus amount. A conversion coefficient corresponding to the aperture value of So, for example, a shift that can obtain a minimum value of the correlation amount when the reference shift range So is an aperture value of F2.8 and a defocus amount of 1 mm. When set as a range, k1 is a conversion coefficient corresponding to the aperture value F2.8. Further, in the above equation (1), k2 is a conversion coefficient corresponding to the aperture value obtained in step S101, among the conversion coefficients for converting the shift amount from which the minimum value of the correlation amount is obtained into the defocus amount. is there.

  For example, the reference shift range So is a shift range in which the minimum value of the correlation amount can be obtained when the aperture value is F5.6 and the defocus amount is 1 mm, and the aperture value acquired in step S101 is F2. In the case of 8, when the conversion coefficient k1 at the aperture value F5.6 is, for example, twice the conversion coefficient k2 at the aperture value F2.8, the effective shift range is based on the above equation (1). Sna can be determined as a range twice as large as the shift range So at the aperture value F5.6. Note that Sna and So are both integers. In this embodiment, when the effective shift range Sna is obtained, the decimal part of So × (k1 / k2) is rounded down or rounded off to calculate Sna as an integer. To do.

Note that the method for determining the effective shift range is not particularly limited to the above-described method. For example, since the conversion coefficient corresponding to the aperture value and the aperture value have a substantially linear relationship, the shift amount is converted into the defocus amount. Instead of the conversion coefficient for this purpose, the effective shift range may be determined using the aperture value as it is. Specifically, the effective shift range Sna may be determined based on the following formula (2).
Sna = So × (f1 / f2) (2)
In the above equation (2), f1 is the aperture value in the reference shift range So, and f2 is the aperture value acquired in step S101.

  Next, the process proceeds to step S103, and a pair of image data corresponding to a pair of images from the focus detection pixels 222a and 222b constituting the focus detection pixel rows 22a, 22b, and 22c of the image sensor 22 by the camera control unit 21, that is, a pair of image data. The first data string and the second data string are read out.

  Next, in step S104, the camera control unit 21 determines whether or not it can be determined that the focus lens 32 is located in the vicinity of the in-focus position including the in-focus position. For example, when the photographer does not half-press the release button provided in the operation unit 28 and the focus lens 32 is not focused based on the result of focus detection by the phase difference detection method. If it cannot be determined that the focus lens 32 is located in the vicinity of the in-focus position, the process proceeds to step S105. On the other hand, when the photographer presses the release button halfway and the focus lens 32 is driven based on the result of focus detection by the phase difference detection method, the focus lens 32 moves to the in-focus position or the focus position. If it can be determined that the position is in the vicinity of the focal position, the process proceeds to step S201 shown in FIG.

  In step S104, whether or not it can be determined that the focus lens 32 is positioned in the vicinity of the in-focus position including the in-focus position is determined based on whether the focus lens 32 is actually positioned in the vicinity of the in-focus position including the in-focus position. It can be determined that the focus lens 32 is positioned in the vicinity of the in-focus position including the in-focus position, for example, after performing in-focus driving based on the focus detection result by the phase difference detection method. In such a case, it is determined that it can be determined to be located in the vicinity of the in-focus position including the in-focus position. For this reason, in step S104, even when the focus lens 32 is not actually positioned in the vicinity of the in-focus position including the in-focus position, after performing focus drive based on the focus detection result by the phase difference detection method, etc. When it can be determined that the focus lens 32 is located in the vicinity of the in-focus position including the in-focus position, it is determined that the focus lens 32 can be determined in the vicinity of the in-focus position including the in-focus position.

  In step S104, when it is not possible to determine that the focus lens 32 is positioned in the vicinity of the focus position, such as when focus drive of the focus lens 32 based on the result of focus detection by the phase difference detection method is not executed, Proceeding to step S105, in step S105, the camera control unit 21 performs a correlation operation for the entire predetermined shift range Sa set in advance. The predetermined shift range Sa is, for example, a shift range set based on the number of focus detection pixels 222a and 222b constituting the focus detection pixel rows 22a to 22c. When the aperture is wide open, the shift range can be set so that the correlation calculation can be appropriately performed.

Specifically, in step S103, the camera control unit 21 reads the first data strings a ₁ , a ₂ ,... Read from the focus detection pixel arrays 22a, 22b, and 22c. . . , _An and the second data string b ₁ , b ₂ ,. . . and b _n, in preset predetermined shift range Sa whole, while relatively shifting one-dimensionally, performing a correlation calculation shown by the following formula (3).
C (h) = Σ | a (n + h) −b (n) | (3)
In the above equation (3), the Σ operation indicates a cumulative operation (phase sum operation) for n. Further, h is a variable corresponding to the shift amount. In the calculation result of the above formula (3), the correlation amount C (h) is smaller as the correlation between the first data string and the second data string is higher. Become. In the present embodiment, such correlation calculation is executed for the entire predetermined shift range Sa set in advance.

  Next, in step S106, the shift amount is within the effective shift range Sna determined in step S102 among the calculation results of the correlation amount in the entire range of the predetermined shift range Sa calculated in step S105 by the camera control unit 21. Processing for detecting the minimum value of the correlation amount is executed using the calculation result. That is, for example, the predetermined shift range Sa subjected to the correlation calculation in step S105 is a range of shift amount = −20 to +20, while the effective shift range Sna determined in step S102 is the shift amount = −10 to +10. In this case, the process of detecting the minimum value of the correlation amount is performed using only the calculation result of the correlation amount when the shift amount = −10 to +10.

Note that the minimum value of the correlation amount is detected, for example, by using a three-point interpolation method shown in the following formulas (4) to (7) to obtain a minimum value C (x) for the continuous correlation amount. This is done by determining the quantity x. Here, C (hj) shown in the following equation is the smallest value among the correlation amounts C (h) calculated by the above equation (3).
D = {C (hj−1) −C (hj + 1)} / 2 (4)
C (x) = C (hj) − | D | (5)
x = hj + D / SLOP (6)
SLOP = MAX {C (hj + 1) -C (hj), C (hj-1) -C (hj)} (7)

  Next, in step S107, it is determined in step S106 whether or not the minimum value of the correlation amount has been detected within the effective shift range Sna. If the minimum value of the correlation amount can be detected, the process proceeds to step S108. On the other hand, if the minimum value of the correlation amount cannot be detected, the process proceeds to step S109.

In step S108, the defocus amount df is calculated according to the following equation (8) based on the shift amount x from which the minimum value C (x) of the correlation amount detected in step S106 is obtained.
df = x · k · p (8)
In the above equation (8), k is a conversion coefficient for converting the shift amount x from which the minimum value C (x) of the correlation amount is obtained into the defocus amount. As described above, since the shift amount for obtaining the minimum value of the correlation amount differs depending on the aperture value, the conversion coefficient is preset according to the aperture value. Further, p is a constant determined by the pitch width of the focus detection pixels 222a and 222b constituting the focus detection pixel rows 22a to 22c.

  The defocus amount calculated in this way is used to adjust the focus of the optical system by driving the focus lens 32 when the release button provided in the operation unit 28 is half-pressed by the photographer. Used when doing.

  On the other hand, in step S109, since the minimum value of the correlation amount cannot be detected within the effective shift range Sna, it is determined that the defocus amount cannot be detected.

  Then, in both cases where the defocus amount is calculated in step S108 and in the case where it is determined in step S109 that the defocus amount cannot be detected, the process returns to step S101, and the photographer prepares for the operation unit 28. When the release button is not half-pressed and the focus lens 32 is not driven based on the result of focus detection by the phase difference detection method, the focus lens 32 is in the vicinity of the focus position. As long as the state in which it cannot be determined continues (step S104 = No), the processes of steps S101 to S109 are repeated.

On the other hand, in step S104 described above, the photographer half-pressed the release button provided in the operation unit 28, and the focus lens 32 was driven to focus based on the result of focus detection by the phase difference detection method. When it is determined that the focus lens 32 can be positioned in the vicinity of the in-focus position including the in-focus position, such as after, the process proceeds to step S201 illustrated in FIG. 10 and in steps S201 to S210 illustrated in FIG. The defocus amount is calculated by a method different from steps S105 to S109.
Hereinafter, a method for calculating the defocus amount when it is determined that the focus lens 32 can be determined to be located in the vicinity of the in-focus position including the in-focus position will be described.

  First, in step S201 shown in FIG. 10, the camera control unit 21 performs processing for setting the variable N used for the shift calculation to N = 1, and then proceeds to step S202, where the camera control unit 21 sets the shift amount = At 0, the correlation amount calculation is performed.

Specifically, first, the camera control unit 21 in step S103 described above, the first data stream read from the focus detection pixel row _{22a, 22b, 22c a 1,} a 2, ···, and _{a n,} Using the second data string b ₁ , b ₂ ,..., B _n and performing the correlation amount calculation at shift amount = 0 according to the above equation (3), the correlation amount C (0 at shift amount = 0) ) Is calculated.

  Next, the process proceeds to step S203. In step S203, the camera control unit 21 performs a correlation amount calculation with a shift amount = + N. That is, in the above equation (3), the correlation amount C (+ N) at the shift amount = + N is calculated with h = + N. For example, when N = + 1, the correlation amount calculation is performed when the shift amount = + 1 according to the above equation (3), and the correlation amount C (+1) when the shift amount = + 1 is calculated.

  In step S203, the camera control unit 21 detects the minimum value of the correlation amount using the calculated correlation amount C (h). Note that the minimum value of the correlation amount is detected by using the three-point interpolation method shown in the above formulas (4) to (7) as in step S106 described above, with the minimum value C ( x) is performed by obtaining the shift amount x from which the result is obtained. In the present embodiment, for example, even when the correlation amount C (hj) which is the smallest correlation amount is obtained, the correlation amounts C (hj + 1) and C (hj−1) are not calculated (for example, When the smallest correlation amount is C (+1) and C (+2) is not calculated), the minimum value of the correlation amount cannot be detected. Do not perform detection.

  Next, in step S204, it is determined whether or not the minimum value of the correlation amount has been detected in step S203. If the minimum value of the correlation amount can be detected, the process proceeds to step S209. On the other hand, if the minimum value of the correlation amount cannot be detected, the process proceeds to step S205.

  In step S205, the camera control unit 21 calculates the correlation amount with the shift amount = −N. That is, in the above equation (3), assuming that h = −N, the correlation amount C (−N) at the shift amount = −N is calculated. For example, when N = −1, the correlation amount calculation at the shift amount = −1 is executed according to the above equation (3), and the correlation amount C (−1) at the shift amount = −1 is calculated.

  In step S205, as in step S203 described above, using the correlation amount C (h) calculated by the camera control unit 21, the three-point interpolation method shown in the above equations (4) to (7) is used. Is used to detect the minimum value of the correlation amount. In step S205, for example, when the correlation amount C (hj), which is the smallest correlation amount, is obtained, the correlation amounts C (hj + 1) and C (hj-1) are not calculated. Since the minimum value of the correlation amount cannot be detected, the minimum value of the correlation amount is not detected.

  Next, in step S206, it is determined whether or not the minimum value of the correlation amount has been detected in step S205. If the minimum value of the correlation amount can be detected, the process proceeds to step S209. On the other hand, if the minimum value of the correlation amount cannot be detected, the process proceeds to step S207. For example, when the correlation amounts C (−1), C (0), and C (+1) are calculated and the correlation amount is C (0), the above equations (4) to (7) Therefore, when the minimum value C (x) is obtained, the process proceeds to step S209.

  In step S207, it is determined whether or not the correlation amount calculation has been completed for the effective shift range Sna determined in step S102. If it is determined that the correlation calculation has not been completed for the effective shift range Sna, the process proceeds to step S208, the process of setting N = N + 1 is performed, the process returns to step S203, and the correlation amount calculation is performed again. . That is, for example, when the effective shift range Sna = −10 to +10 is set, and the range in which the correlation amount calculation is completed is the shift amount = −1 to +1, in step S208, N = 2 (N = 1 + 1), and the process returns to step S203. In step S203, when the correlation amount C (+2) at the shift amount = + 2 is calculated and the minimum value C (x) of the correlation amount cannot be detected, in step S205, the shift amount = −2. The calculation of the correlation amount C (−2) is performed. As described above, in this embodiment, the absolute value of the shift amount is set to 0, +1, -1, +2, -2, +3, -3, ... until the minimum value C (x) of the correlation amount is detected. The correlation calculation is performed while changing to a large shift amount.

  As a result of the correlation calculation, when the minimum value C (x) of the correlation amount is detected in step S203 or step S205, the process proceeds from step S204 or step S206 to step S209. In step S209, the defocus amount is determined. Is calculated. Specifically, since the minimum value C (x) of the correlation amount is detected in step S209, the camera control unit 21 ends the correlation amount calculation, and similarly to step S108 described above, the detected correlation amount is detected. The defocus amount df is calculated according to the above equation (8) based on the shift amount x that provides the minimum value C (x).

  Based on the defocus amount calculated in this way, it is determined whether or not the focus lens 32 needs to be driven. If the focus lens 32 needs to be driven (for example, the defocus amount is a predetermined value). In such a case, the focus lens 32 is driven based on the calculated defocus amount, and thereby the focus adjustment of the optical system is executed.

  On the other hand, if the correlation amount calculation is not performed for the effective shift range Sna determined in step S102, the minimum value C (x) of the correlation amount cannot be detected, the process proceeds to step S210, and the defocus amount cannot be detected. It is determined that

  Then, both when the defocus amount is calculated in step S209 and when it is determined that the defocus amount cannot be detected in step S210, the process returns to step S101, and the focus lens 32 is in the vicinity of the in-focus position. As long as the state that can be determined to be located continues (step S104 = Yes), the processes of steps S101 to S104 and S201 to S210 are repeatedly executed. On the other hand, when the focus lens 32 cannot be determined to be located in the vicinity of the in-focus position (step S104 = No), the processes of steps S101 to S109 described above are executed.

  In the present embodiment, when calculating the defocus amount by the phase difference detection method, if it cannot be determined that the focus lens 32 is positioned in the vicinity of the in-focus position, first, a predetermined shift range set in advance is set. When the correlation calculation is performed for the entire area Sa, and then the minimum value of the correlation amount is calculated using the correlation calculation result, the correlation calculation result executed for the entire predetermined shift range Sa is based on the aperture value of the diaphragm 34. The minimum value of the correlation amount is calculated using only the correlation calculation result within the effective shift range Sna set as described above. Then, the defocus amount is calculated based on the shift amount that provides the minimum value of the correlation amount. Therefore, according to the present embodiment, depending on the aperture value of the aperture 34, even if the minimum value of the correlation amount is detected, the focus state of the optical system cannot be detected properly, resulting in false focusing. (For example, the case where the aperture value of the aperture 34 is relatively large and the minimum value of the correlation amount is detected at a relatively large shift amount) can be effectively solved. Thus, the focus detection of the optical system can be performed satisfactorily.

  In addition, according to the present embodiment, when calculating the defocus amount by the phase difference detection method, if it can be determined that the focus lens 32 is located in the vicinity of the in-focus position, the calculation of the correlation amount is shifted. Starting from the amount = 0, the calculation of the correlation amount and the detection of the minimum value of the correlation amount are sequentially performed while increasing the absolute value of the shift amount in order, and when the minimum value of the correlation amount is detected, the correlation amount When the local minimum value is detected, the calculation of the correlation amount is terminated. Then, the defocus amount is calculated based on the shift amount that provides the minimum value of the correlation amount. Therefore, according to the present embodiment, it is possible to reduce the time required to calculate the defocus amount. In particular, when it can be determined that the focus lens 32 is located in the vicinity of the in-focus position, the minimum value of the correlation amount exists in the range where the absolute value of the shift amount is small, specifically, the shift amount = 0. Will increase. In such a case, as in the present embodiment, the calculation of the correlation amount is started from the shift amount = 0, and the calculation of the correlation amount and the minimum value of the correlation amount are sequentially increased while the absolute value of the shift amount is sequentially increased. When the detections are sequentially performed, it is possible to detect the minimum value of the correlation amount in a relatively short time, thereby shortening the time required to calculate the defocus amount. In addition to this, according to the present embodiment, it is possible to reduce the calculation load required for the correlation amount calculation.

  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 correlation amount is calculated using the correlation calculation result in the effective shift range Sna set based on the aperture value of the aperture 34 among the correlation calculation results executed for the entire predetermined shift range Sa. However, for example, when a shift amount that can obtain the minimum value of the correlation amount is obtained in the previous processing (particularly, a shift amount that can obtain the minimum value of the correlation amount is obtained). And when the focus lens 32 is driven toward the in-focus position), a shift range Snp narrower than the effective shift range Sna is set based on the obtained shift amount, and a predetermined value is set. Of the correlation calculation results executed for the entire shift range Sa, only the correlation calculation result within the set shift range Snp may be used to calculate the minimum value of the correlation amount. There.

  Alternatively, in the above-described embodiment, the configuration in which focus detection is performed by the phase difference detection method has been described as an example, but in addition to such a configuration, for example, focus detection is performed by the phase difference detection method, and the phase difference detection method is performed. Then, when the focus state cannot be detected, the focus detection may be performed by the contrast detection method while driving the focus lens 32. Alternatively, when focus detection is performed by the phase difference detection method and the focus state cannot be detected by the phase difference detection method, focus detection by the phase difference detection method and focus detection by the contrast detection method are performed while the focus lens 32 is driven. It is good also as a structure performed simultaneously.

  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 (6)

An imaging pixel that captures an image by an optical system including a focus adjustment optical system and outputs an image signal corresponding to the captured image, and a pair of focus detection pixel rows that receive a pair of pupil-divided light beams An imaging unit;
A diaphragm that passes through the optical system and restricts a light beam incident on the imaging unit;
While the first data row and the second data row respectively output from the pair of focus detection pixel rows are relatively shifted in a one-dimensional manner, between the first data row and the second data row. A shift operation for calculating the correlation amount is performed over a predetermined predetermined shift range, and based on the shift calculation result, a shift amount at which an extreme value of the correlation amount is obtained is detected. A phase difference detection unit for detecting a focus state;
A setting unit that sets an effective shift range for obtaining an extreme value of the correlation amount corresponding to the aperture value based on the aperture value by the aperture; and
The phase difference detection unit shifts the extreme value of the correlation amount using a calculation result in an effective shift range corresponding to the aperture value of the diaphragm among the shift calculation results performed for the entire predetermined shift range. A focus detection apparatus that detects an amount. The focus detection apparatus according to claim 1,
Based on the detection result of the focus state by the phase difference detection unit, the focus adjustment optical system is further driven by driving the focus adjustment optical system in the direction of the optical axis, thereby further including a focus adjustment unit that performs focus adjustment of the optical system,
The phase difference detector is
As a result of driving the focus adjustment optical system by the focus adjustment unit, when it can be determined that the focus adjustment optical system is located in the vicinity of the focus position including the focus position,
Instead of performing a shift operation for the entire range of the predetermined shift range, the correlation amount calculation is started with the smallest absolute value of the shift amount, and the correlation amount is increased while increasing the absolute value of the shift amount in order. And the detection of the shift amount for obtaining the extreme value of the correlation amount, and the shift for obtaining the extreme value of the correlation amount when the shift amount for obtaining the extreme value of the correlation amount is detected. When the amount is detected, the calculation of the correlation amount is terminated, and the focus state of the optical system is detected based on the shift amount from which the extreme value of the correlation amount is obtained. . The focus detection apparatus according to claim 2,
When the phase difference detection unit can determine that the focus adjustment optical system is located in the vicinity of the focus position including the focus position as a result of driving the focus adjustment optical system by the focus adjustment unit. In the effective shift range set by the setting unit, the calculation of the correlation amount and the detection of the shift amount that provides the extreme value of the correlation amount are performed. The focus detection apparatus according to claim 1,
The focus detection apparatus characterized in that the setting unit sets the effective shift range to a smaller range as the aperture value by the aperture is larger. The focus detection device according to any one of claims 1 to 4,
A contrast detection unit that detects a focus state of the optical system by calculating an evaluation value related to a contrast of the image by the optical system based on the image signal output by the imaging pixel, Focus detection device.   An imaging device provided with the focus detection apparatus in any one of Claims 1-5.

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