JP5760792B2 - Focus adjustment device and imaging device - Google Patents

Description

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

  2. Description of the Related Art Conventionally, a focus adjustment device that detects a focus state of an optical system after a release button is half-pressed is known. In such a focus adjustment device, when detecting the focus state of the optical system, if the exposure is not suitable for focus detection, exposure control is performed so that the exposure is suitable for focus detection, and it is suitable for focus detection. A technique for detecting a focus state of an optical system after exposure to light is known (for example, Patent Document 1).

JP 2005-316271 A

  However, in the conventional technology, after the release button is pressed halfway, when the exposure is not suitable for focus detection, exposure control is performed so that the exposure is suitable for focus detection. In some cases, it takes time to drive the focus lens.

  The problem to be solved by the present invention is to provide a focus adjustment device capable of suitable focus adjustment.

  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 adjusting apparatus according to the present invention includes a pair of light receiving sensors (222a, 222b) that receive a pair of light beams via an optical system having a focus adjusting optical system (32), and outputs of the pair of light receiving sensors. And a phase difference detector (21) for detecting the amount of deviation of the image plane by the optical system, and focus adjustment for adjusting the focus of the optical system by driving the focus adjustment optical system in the optical axis direction. Unit (36), an activation unit (28) that activates focus adjustment by the focus adjustment unit, a storage unit (24) that stores the amount of deviation detected by the phase difference detection unit, exposure time, imaging sensitivity, And an exposure control unit (21) that performs exposure control of the pair of light receiving sensors based on an exposure control value including an aperture value, and a first threshold value that is a reliability threshold value of the deviation amount, and the reliability of the deviation amount. When the sex is greater than or equal to the first threshold A first threshold value setting unit (21) that sets a threshold value so that it can be determined that the shift amount after focus adjustment is within the range of the depth of field of the subject by performing focus adjustment based on the shift amount; When the reliability of the deviation amount is less than the second threshold value, the second threshold value, which is the reliability threshold value of the deviation amount, indicates the direction in which the in-focus position exists in the optical axis direction based on the deviation amount. When the focus adjustment is activated by the second threshold value setting unit (21) that sets a threshold that can be determined and the activation unit, the shift detected before the focus adjustment is activated. Determining means (21) for determining whether or not the reliability of the quantity is equal to or greater than the first threshold and less than the second threshold, and is detected before starting the focus adjustment It is determined that the reliability of the deviation amount is not less than the first threshold value. In this case, the focus adjustment unit drives the focus adjustment optical system based on the shift amount detected before starting the focus adjustment without causing the exposure control unit to change the exposure control value. 1 control unit (21) and the reliability of the deviation detected before starting the focus adjustment is less than the first threshold and greater than or equal to the second threshold, the optical By changing at least one of the exposure time and the imaging sensitivity while fixing the aperture value of the system, it is determined whether or not the exposure is suitable for focus detection, and the exposure is suitable for focus detection. In this case, the exposure control unit performs exposure control by changing at least one of the exposure time and the imaging sensitivity while keeping the aperture value of the optical system fixed, and exposure suitable for focus detection If not, the exposure control unit In addition to the aperture value of the optical system, at least one of the exposure time and the imaging sensitivity is changed to perform exposure control, and before starting the focus adjustment. When the reliability of the detected deviation amount is less than the second threshold value, the exposure control unit does not fix the aperture value of the optical system without fixing the aperture value, the exposure time, and the A third control unit (21) for performing exposure control by changing at least one of the imaging sensitivities.

  [2] In the invention according to the focus adjustment device, the second control unit (21) changes at least one of the exposure time and the imaging sensitivity while fixing the aperture value of the optical system. In addition, even when the exposure is a predetermined number of steps brighter than the exposure optimal for focus detection or the exposure is dark by a predetermined number of steps, it is determined that the exposure is suitable for focus detection, and the exposure control unit (21) transmits the optical The exposure control can be performed by changing at least one of the exposure time and the imaging sensitivity while the aperture value of the system is fixed.

  [3] In the invention relating to the focus adjustment device, an image pickup unit (22) that picks up an image by the optical system and outputs an image signal corresponding to the picked-up image, and the image signal output by the image pickup unit And a contrast detection unit (21) for detecting a focus state of the optical system by calculating an evaluation value related to the contrast of the image by the optical system, and the pair of light receiving sensors (222a, 222b). Can be configured to be provided on the light receiving surface of the imaging unit.

  [4] In the invention related to the focus adjustment device, the phase difference detection unit (21) can be configured to detect the shift amount regardless of whether or not the focus adjustment is activated. .

  [5] An imaging apparatus according to the present invention includes the above-described focus adjustment apparatus.

  According to the present invention, suitable focus adjustment can be realized.

FIG. 1 is a block diagram showing a camera according to the present embodiment. FIG. 2 is a front view showing a focus detection position on the 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 illustrating an operation example of the camera according to the present embodiment. FIG. 10 is a flowchart showing the scan operation execution process in step S119.

  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 rotary 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.

  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 photographer to set various operation modes of the camera 1, and switches between the auto focus mode / manual focus mode and the one shot mode / continuity even in the auto focus mode. It is possible to switch between the numeric modes. 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 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 kinds of focus detection pixels 222a and 222b are arranged in a straight line 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.

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

  Next, an operation example of the camera 1 according to the present embodiment will be described. FIG. 9 is a flowchart showing an operation example of the camera 1 according to the present embodiment. The following operation is started when the camera 1 is turned on. In the following, a description will be given by taking as an example a case where the one-shot mode, that is, the mode in which the focus lens 32 that has been adjusted once is fixed and the mode for photographing at the focus lens position is selected.

  First, in step S101, generation of a through image by the camera control unit 21 and display of a through image by the electronic viewfinder 26 of the observation optical system are started. Specifically, an exposure operation is performed by the imaging element 22, and pixel data of the imaging pixel 221 is read by the camera control unit 21. Then, the camera control unit 21 generates a through image based on the read data, and the generated through image is sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder 26 of the observation optical system. As a result, the user can visually recognize the image of the subject through the eyepiece lens 27. Note that the generation of the through image and the display of the through image are repeatedly executed at predetermined intervals.

  In step S102, the camera control unit 21 starts exposure control for generating a through image. Specifically, the camera control unit 21 divides the shooting screen into a plurality of areas, and performs multi-division metering (multi-pattern metering) in which photometry is performed for each of the divided areas, whereby the luminance value Bv of the entire shooting screen. Is calculated. Then, the camera control unit 21 changes the imaging sensitivity Sv, the exposure time Tv, and the aperture Av so as to obtain an appropriate exposure on the entire shooting screen based on the calculated luminance value Bv of the entire shooting screen. I do. Note that the exposure control at the time of generating the through image is repeatedly executed at a predetermined interval. However, the interval at which the exposure control for generating the through image is performed is longer than the interval at which the generation of the through image and the display of the through image are repeated. can do. For example, the exposure control for generating the through image can be performed once while the generation of the through image and the display of the through image are repeated three times.

  In step S103, the camera control unit 21 starts defocus amount calculation processing by the phase difference detection method. In the present embodiment, the defocus amount calculation process by the phase difference detection method is performed as follows. That is, first, the image sensor 22 receives a light beam from the photographing optical system, and the camera control unit 21 performs focus detection pixels 222a and 222b constituting the three focus detection pixel rows 22a to 22c of the image sensor 22. A pair of image data corresponding to the pair of images is read out. In this case, when a specific focus detection position is selected by a manual operation of the photographer, only data from focus detection pixels corresponding to the focus detection position may be read. Then, the camera control unit 21 performs image shift detection calculation processing (correlation calculation processing) based on the read pair of image data, and images at the focus detection positions corresponding to the three focus detection pixel rows 22a to 22c. The shift amount is calculated, and the image shift amount is converted into a defocus amount.

  In step S103, the camera control unit 21 evaluates the reliability of the defocus amount for the calculated defocus amount. In the present embodiment, the camera control unit 21 sets the reliability of the defocus amount to “high”, “medium”, “low”, and “measurement” based on, for example, the matching degree and contrast of a pair of image data. Evaluation is based on four levels, “distance impossible”.

  Specifically, the camera control unit 21 uses the three determination values of the first determination value, the second determination value, and the third determination value to evaluate the reliability of the defocus amount. The reliability of the defocus amount is evaluated using these three determination values stored in advance in the memory.

  If the reliability of the defocus amount is equal to or higher than the first determination value, the first determination value is adjusted based on the defocus amount so that the defocus amount after the focus adjustment is It is set to a value that can be determined to be within the depth range. Therefore, for example, when the reliability of the defocus amount obtained for a specific subject is equal to or higher than the first determination value, the camera control unit 21 drives the focus lens 32 based on the defocus amount. Therefore, it is determined that the camera can focus on a specific subject, and the reliability of such a defocus amount is evaluated as “high”. In addition, when the reliability of the defocus amount obtained for a specific subject is less than the first determination value and is equal to or higher than a second determination value described later, the camera control unit 21 performs, for example, the defocus amount. By driving the focus lens 32 on the basis of the focus amount, it is possible to focus on a specific subject with a relatively high probability. The focus amount is determined to be close to the depth of field of a specific subject, and the reliability of such a defocus amount is evaluated as “medium”.

  Further, the second determination value is a value lower than the first determination value, and when the reliability of the defocus amount is less than the second determination value, the in-focus position is based on the defocus amount, The value is set so that it can be determined whether the optical axis direction is on the infinity side or the close side. Further, the third determination value is a value lower than the first determination value and the second determination value, and when the reliability of the defocus amount is less than the third determination value, the direction in which the in-focus position exists. Is set to a value that cannot be determined. Therefore, when the reliability of the defocus amount is less than the second determination value and greater than or equal to the third determination value, the camera control unit 21 determines that the in-focus position is based on this defocus amount. It is determined that it is possible to determine whether it exists on the infinity side or the close side in the optical axis direction, and the reliability of such a defocus amount is evaluated as “low”. Further, when the reliability of the defocus amount is less than the third determination value, the camera control unit 21 evaluates the reliability of the defocus amount as “distance cannot be measured”.

  Note that the calculation of the defocus amount and the evaluation of the reliability of the defocus amount are repeatedly performed at predetermined intervals while the operation of the camera 1 is being performed. Further, the defocus amount and the reliability of the defocus amount obtained in this way are stored in the memory 24 as defocus amount history data.

  In step S104, the camera control unit 21 determines whether the shutter release button provided in the operation unit 28 is half-pressed (the first switch SW1 is turned on). If the shutter release button is pressed halfway, the process proceeds to step S105. On the other hand, if the shutter release button is not half-pressed, step S104 is repeated until the shutter release button is half-pressed. That is, until the shutter release button is pressed halfway, through image generation / display, through image generation exposure control, defocus amount calculation, and defocus amount reliability evaluation are repeatedly performed.

  In step S105, the camera control unit 21 sets n, which is a predetermined parameter, to 0. In subsequent step S106, the defocus amount history data stored in step S103 is referred to, and the defocus amount calculated before the shutter release button is half-pressed and the reliability of the defocus amount according to the parameter n is selected. The focus amount and the reliability of the defocus amount are read out, and it is determined whether or not the reliability of the read defocus amount is “high”. For example, when the parameter n is set to zero, the camera control unit 21 reads the defocus amount calculated immediately before the shutter release button is half-pressed and the reliability of the defocus amount, and the shutter release. It is determined whether or not the reliability of the defocus amount calculated immediately before the button is half-pressed is “high”. Further, when the parameter n is set to 1, the camera control unit 21 determines the defocus amount calculated immediately before the defocus amount calculated immediately before the shutter release button is half-pressed and the defocus amount. The reliability of the focus amount is read, and it is determined whether or not the reliability of the read defocus amount is “high”. Similarly, as the value of n increases, the camera control unit 21 goes back to the past and determines the defocus amount calculated n times before the defocus amount calculated immediately before the shutter release button is pressed halfway. It is determined whether or not the reliability is “high”.

  If it is determined in step S106 that the reliability of the defocus amount calculated n times before the defocus amount immediately before the shutter release button is half-pressed is “high”, the process proceeds to step S107. On the other hand, if it is determined that the reliability of the defocus amount calculated n times before the defocus amount immediately before the shutter release button is half-pressed is not “high”, the process proceeds to step S112.

  In step S107, since it is determined that the reliability of the defocus amount calculated before the shutter release button is half-pressed is “high”, the camera control unit 21 prohibits the AE lock (change of the exposure condition). Process). In step S108, it is necessary to drive the focus lens 32 to the in-focus position based on the defocus amount before the shutter release button is half-depressed, which is determined to have high reliability. The calculated lens drive amount is calculated, and the calculated lens drive amount is sent to the focus lens drive motor 36 via the lens control unit 37. Next, in step S109, the focus lens drive motor 36 drives the focus lens 32 based on the lens drive amount calculated in step S108.

  When the driving of the focus lens 32 to the in-focus position is completed, the process proceeds to step S110 where a focus display is performed, and then the process proceeds to step S111 where the focus lock (process for prohibiting the drive of the focus lens 32) is performed. Done. The focus display in step S110 is performed by the electronic viewfinder 26, for example.

  As described above, in this embodiment, when it is determined that the reliability of the defocus amount calculated before half-pressing the shutter release button is “high”, the focus detection is performed after half-pressing the shutter release button. The focus lens 32 is driven in focus based on the defocus amount calculated before the shutter release button is half-pressed without performing the exposure control.

  On the other hand, if it is determined in step S106 that the reliability of the defocus amount calculated n times before the defocus amount immediately before the shutter release button is half-pressed is not “high”, the process proceeds to step S112. . In step S112, the camera control unit 21 determines whether or not the reliability of the defocus amount calculated n times before the defocus amount immediately before the shutter release button is half-pressed is “medium”. . If it is determined that the reliability of the defocus amount is “medium”, the process proceeds to step S113, whereas if it is determined that the reliability of the defocus amount is not “medium”, the process proceeds to step S120.

  In step S113, as in step S108, the lens driving amount is calculated based on the defocus amount before the shutter release button is pressed halfway, for which the reliability is determined to be “medium”, and In step S114, driving of the focus lens 32 is started based on the lens driving amount calculated in step S113.

  In step S115, the camera control unit 21 determines whether or not an exposure suitable for focus detection can be obtained by changing only the imaging sensitivity Sv and the exposure time Tv while the aperture Av of the exposure control value is fixed. Judgment is made.

  Specifically, the camera control unit 21 performs spot photometry in predetermined areas including the focus detection areas (focus detection pixel rows 22a, 22b, and 22c shown in FIG. 2) based on the output of the image sensor 22, Luminance value SpotBv in a predetermined area including the focus detection area is calculated, and based on the calculated luminance value SpotBv, the imaging sensitivity Sv and exposure at which the exposure in the predetermined area including the focus detection area becomes an exposure suitable for focus detection By determining the time Tv, it is determined whether exposure suitable for focus detection can be obtained. In the present embodiment, the camera control unit 21 changes only the imaging sensitivity Sv and the exposure time Tv, and the exposure in the predetermined area including the focus detection area is, for example, the exposure in the predetermined area including the focus detection area. However, exposure that is suitable for focus detection can be obtained even when the exposure is in the range from exposure that is one step darker than the optimal exposure for focus detection to one step brighter than the optimal exposure for focus detection. Judge.

  However, the imaging sensitivity Sv and the exposure time Tv are predetermined in a range that can be changed, and there are cases where exposure suitable for focus detection cannot be obtained only by changing the imaging sensitivity Sv and the exposure time Tv. Therefore, the camera control unit 21 changes only the imaging sensitivity Sv and the exposure time Tv, determines whether exposure suitable for focus detection is obtained, changes only the imaging sensitivity Sv and the exposure time Tv, If it is determined that an exposure suitable for focus detection can be obtained, the process proceeds to step S116. On the other hand, if only the imaging sensitivity Sv and the exposure time Tv are changed and an exposure suitable for focus detection cannot be obtained, Proceed to step S122.

  If it is determined in step S115 that only the imaging sensitivity Sv and the exposure time Tv can be changed to obtain an exposure suitable for focus detection, the process proceeds to step S116, and the camera control unit 21 performs focus detection. Exposure control is performed. Specifically, the camera control unit 21 sets the imaging sensitivity Sv and the exposure time Tv used for focus detection to the imaging sensitivity Sv and the exposure time Tv calculated in step S115 while the aperture Av is fixed among the exposure control values. change. Thereby, for example, the gain of the amplifier that amplifies the signal output from the focus detection pixels 222a and 222b is changed according to the imaging sensitivity Sv calculated in step S115, or the exposure time Tv calculated in step S115. The exposure time for the focus detection pixels 222a and 222b of the image sensor 22 is changed accordingly. As a result, in a predetermined area including the focus detection area (focus detection pixel rows 22a, 22b, and 22c shown in FIG. 2), an exposure suitable for focus detection (for example, exposure that is one step darker than the appropriate exposure, from the appropriate exposure). Can be obtained within a range up to one step brighter exposure).

  Next, in step S117, the camera control unit 21 performs focus detection with an exposure suitable for focus detection, calculates a defocus amount, and evaluates the reliability of the defocus amount. In step S118, the camera control unit 21 determines whether or not the reliability of the defocus amount calculated after changing to an exposure suitable for focus detection is “high” or “medium”. If it is determined that the reliability of the defocus amount calculated after changing to an exposure suitable for focus detection is “high” or “medium”, the process proceeds to step S107, and focus detection is performed in steps S107 to S111. A focusing operation is performed based on the defocus amount calculated after changing to an appropriate exposure. On the other hand, if it is determined that the reliability of the defocus amount calculated after changing to an exposure suitable for focus detection is not “high” or “medium”, the process proceeds to step S119.

  As described above, in the present embodiment, when the reliability of the defocus amount calculated before the shutter release button is half-pressed is determined to be “medium”, the imaging sensitivity Sv and the aperture sensitivity Av are fixed. By changing only the exposure time Tv and performing exposure control for focus detection, the exposure is suitable for focus detection, and the focus lens 32 is adjusted based on the defocus amount calculated with the exposure suitable for focus detection. Focus driving is performed.

  On the other hand, if it is determined in step S112 that the reliability of the defocus amount calculated n times before the defocus amount immediately before the shutter release button is half-pressed is not “medium”, the process proceeds to step S120. In step S120, the camera control unit 21 determines whether the value of the parameter n is less than a predetermined number. When the value of n is less than the predetermined number, the process proceeds to step S121, 1 is added to the value of n, and the process returns to step S106. That is, whether the reliability of the defocus amount calculated n times before the defocus amount immediately before half-pressing the shutter release button is “high” or “medium” until the value of n becomes a predetermined number or more. A determination of whether or not is made. If it is determined in step S120 that the value of n is greater than or equal to the predetermined number, the reliability of the defocus amount is determined to be “low” or “distance cannot be measured”, and the process proceeds to step S122. Become.

  When it is determined in step S120 that the reliability of the defocus amount is “low” or “distance cannot be measured”, or in step S115, only the imaging sensitivity Sv and the exposure time Tv are changed, and focus detection is performed. If it is determined that a suitable exposure cannot be obtained, the process proceeds to step S122. In step S122, the camera control unit 21 performs exposure control for focus detection by changing the aperture Av, the imaging sensitivity Sv, and the exposure time Tv. Specifically, the camera control unit 21 calculates a brightness value SpotBv within a predetermined area including the focus detection area, and based on the calculated brightness value SpotBv, an exposure suitable for focus detection is obtained. An exposure time Tv and an aperture Av are determined. In step S122, the camera control unit 21 preferentially changes the light receiving sensitivity Sv and the exposure time Tv among the exposure control values, and only by changing the light receiving sensitivity Sv and the exposure time Tv, an exposure suitable for focus detection is obtained. Only when it cannot be obtained, the aperture Av is changed. Then, the camera control unit 21 controls the exposure to the image sensor 22 based on the determined light receiving sensitivity Sv, exposure time Tv, and aperture stop Av. Then, after exposure control for focus detection is performed in step S122, the process proceeds to step S117, and the reliability of the defocus amount calculated after changing to an exposure suitable for focus detection is “high” or “medium”. A determination is made as to whether or not.

  In step S118, even when the exposure is suitable for focus detection, if the reliability of the defocus amount is not “high” or “medium”, the process proceeds to step S119. In step S119, the camera control unit 21 performs a scan operation execution process for executing the scan operation. Here, the scan operation is a predetermined calculation of the defocus amount and the focus evaluation value by the phase difference detection method by the camera control unit 21 while the focus lens 32 is scan-driven by the focus lens drive motor 36. Thus, the detection of the in-focus position by the phase difference detection method and the detection of the in-focus position by the contrast detection method are simultaneously performed at predetermined intervals. In the following, the scan operation execution process according to the present embodiment will be described with reference to FIG. FIG. 10 is a flowchart showing the scan operation execution process according to the present embodiment.

  First, in step S201, the camera control unit 21 performs a scan operation start process. Specifically, the camera control unit 21 sends a scan drive start command to the lens control unit 37, and the lens control unit 37 drives the focus lens drive motor 36 based on the command from the camera control unit 21 to focus. The lens 32 is scan-driven along the optical axis L1. The direction in which the scan drive is performed is not particularly limited, and the scan drive of the focus lens 32 may be performed from the infinite end to the close end, or may be performed from the close end to the infinite end. Good.

  Then, while driving the focus lens 32, the camera control unit 21 reads out a pair of image data corresponding to the pair of images from the focus detection pixels 222a and 222b of the image sensor 22 at predetermined intervals. The phase difference detection method calculates the defocus amount, evaluates the reliability of the calculated defocus amount, and drives the focus lens 32 to drive the pixel output from the imaging pixel 221 of the imaging element 22 at a predetermined interval. Reading is performed, and based on this, a focus evaluation value is calculated, thereby acquiring a focus evaluation value at a different focus lens position, thereby detecting a focus position by a contrast detection method.

  In step S202, AE lock (processing for prohibiting change of exposure conditions) is performed to prevent the exposure from being changed while the focus position is detected by the contrast detection method. In step S203, the camera control unit 21 determines whether the defocus amount has been calculated by the phase difference detection method as a result of the scanning operation. If the defocus amount can be calculated, it is determined that distance measurement is possible and the process proceeds to step S206. On the other hand, if the defocus amount cannot be calculated, it is determined that distance measurement is not possible and the process proceeds to step S204. . In step S203, even when the defocus amount can be calculated, if the reliability of the calculated defocus amount is evaluated as “low” or “range measurement impossible”, the defocus amount is calculated. As a result, it proceeds to step S204.

  In step S204, the camera control unit 21 determines whether or not the in-focus position has been detected by the contrast detection method as a result of the scanning operation. If the in-focus position can be detected by the contrast detection method, the process proceeds to step S211. If the in-focus position cannot be detected, the process proceeds to step S205.

  In step S <b> 205, the camera control unit 21 determines whether the scan operation has been performed for the entire driveable range of the focus lens 32. If the scan operation is not performed for the entire driveable range of the focus lens 32, the process returns to step S203, and steps S203 to S205 are repeated to perform the scan operation, that is, while the focus lens 32 is driven to scan. The operation of simultaneously executing the calculation of the defocus amount by the phase difference detection method and the detection of the in-focus position by the contrast detection method at predetermined intervals is continuously performed. On the other hand, if the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S215.

  As a result of executing the scanning operation, if it is determined in step S203 that the defocus amount can be calculated by the phase difference detection method, the process proceeds to step S206, and in steps S206 to S210, the calculation is performed by the phase difference detection method. A focusing operation is performed based on the defocus amount.

  That is, first, in step S206, the camera control unit 21 performs a scan operation stop process, and then proceeds to step S207. The camera control unit 21 performs a scan operation prohibition process.

  In step S208, the lens driving amount required to drive the focus lens 32 to the in-focus position is calculated from the defocus amount calculated by the phase difference detection method in step S203, and the calculated lens is calculated. The driving amount is sent to the lens driving motor 36 via the lens control unit 37. Then, the lens driving motor 36 drives the focus lens 32 to the in-focus position based on the lens driving amount calculated by the camera control unit 21.

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

  When the driving of the focus lens 32 to the in-focus position is completed, the process proceeds to step S209, in-focus display is performed, and then the process proceeds to step S210, where focus lock (processing for prohibiting driving of the focus lens 32) is performed. Done. Note that the in-focus display in step S209 is performed by the electronic viewfinder 26, for example. Further, when performing the focus display, a display for notifying the user that the focus operation has been performed by the phase difference detection method may be performed together.

  As a result of executing the scanning operation, if it is determined in step S204 that the in-focus position has been detected by the contrast detection method, the process proceeds to step S211 and detected in steps S211 to S214 by the contrast detection method. Based on the in-focus position, the focus lens 32 is driven.

  That is, first, in step S211, the camera control unit 21 performs a scan operation stop process, and then proceeds to step S212. As in step S207 described above, the camera control unit 21 performs a scan operation prohibition process. Done.

  Then, the process proceeds to step S213, and a lens driving process for driving the focus lens 32 to the in-focus position is performed based on the in-focus position detected by the contrast detection method. When driving the focus lens 32 to the in-focus position based on the detection result by the contrast detection method, the focus by the phase difference detection method is completed until the drive of the focus lens 32 to the in-focus position is completed. It is preferable to prohibit the driving of the focus lens 32 based on the detection result. Thereby, the hunting phenomenon of the focus lens 32 can be suppressed.

  When the driving of the focus lens 32 to the in-focus position is completed, the process proceeds to step S214, in-focus display is performed, and then the process proceeds to step S210, where focus lock (processing for prohibiting driving of the focus lens 32) is performed. Done. Note that the in-focus display in step S214 is performed by the electronic viewfinder 26, for example. Further, when performing the in-focus display, a display for notifying the user that the in-focus operation has been performed by the contrast detection method may be performed together.

  In the scanning operation of the present embodiment, the above-described steps S203 to S205 are repeatedly executed, so that the focus lens 32 is driven to scan, the defocus amount is calculated by the phase difference detection method, and the contrast detection method is used. The detection of the focal position is simultaneously performed at a predetermined interval. Then, as a result of repeatedly executing steps S203 to S205 described above, the focus detection result by the detection method in which the defocus amount can be calculated or the in-focus position can be detected first among the phase difference detection method and the contrast detection method. The focus lens 32 is used to drive to the in-focus position. Further, as described above, in the scanning operation of the present embodiment, after determining whether or not the defocus amount can be calculated by the phase difference detection method (step S203), the in-focus position can be detected by the contrast detection method. If the phase difference detection method and the contrast detection method can calculate the defocus amount and detect the in-focus position at the same time by determining whether or not the focus position has been detected, the focus by the phase difference detection method is determined. The detection result is adopted in preference to the focus detection result by the contrast detection method.

  On the other hand, if it is determined in step S205 that the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S215. In step S215, as a result of performing the scanning operation, focus detection could not be performed by any of the phase difference detection method and the contrast detection method, so that the scanning operation end processing is performed, and then in step S216 Advancing and in-focus indication is performed. The in-focus indication is performed by the electronic viewfinder 26, for example.

  In this way, the scan operation execution process in step S119 is performed. Then, after the scan operation execution process in step S119 is completed, the operation of the camera 1 is also terminated.

  As described above, in this embodiment, when it is evaluated that the reliability of the defocus amount calculated before the shutter release button is half-pressed is “high”, the defocus whose reliability is “high”. By driving the focus lens 32 based on the amount, it is determined that the subject can be focused, and the shutter release button is half-pressed without performing exposure control for focus detection after the shutter release button is half-pressed. The focus lens 32 is driven based on the previously calculated defocus amount. As described above, in this embodiment, when the reliability of the defocus amount is evaluated as “high”, the exposure control after the shutter release button is half-pressed is not performed. The time from when it is pressed until the focus lens 32 is driven can be shortened.

  In this embodiment, when the reliability of the defocus amount calculated before half-pressing the shutter release button is evaluated as “medium”, the aperture Av is fixed after half-pressing the shutter release button. The exposure control for focus detection is performed by changing only the imaging sensitivity Sv and the exposure time Tv, and the focus lens 32 is driven based on the focus amount obtained with the exposure suitable for focus detection. As described above, in this embodiment, when the reliability of the defocus amount calculated before the shutter release button is half-pressed is evaluated as “medium”, the exposure control is performed without changing the aperture Av. Therefore, since the operation according to the change of the aperture Av that requires a relatively long time in exposure control, such as driving of the aperture 34 according to the change of the aperture Av, can be prevented, the time required for the exposure control can be shortened. The time from when the shutter release button is half-pressed until the focus lens 32 is driven can be shortened. In particular, in the present embodiment, the exposure within a predetermined region including the focus detection area is in a range from an exposure that is one step darker than the optimum exposure for focus detection to an exposure that is one step brighter than the optimum exposure for focus detection. Even in the case of exposure, since it is determined that the exposure is suitable for focus detection and exposure control for focus detection is performed, exposure control for focus detection is executed by changing only the imaging sensitivity Sv and the exposure time Tv. It becomes easy.

  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, when it is evaluated that the reliability of the defocus amount calculated before the shutter release button is half-pressed is “medium”, the exposure in a predetermined region including the focus detection area is Even if the exposure is in the range from exposure that is one step darker than the optimal exposure for focus detection to one step brighter than the optimal exposure for focus detection, it is determined that the exposure is suitable for focus detection and is used for focus detection. However, the present invention is not limited to this configuration. For example, even if the exposure is brighter by a predetermined number of steps than the exposure optimal for focus detection or darker by the predetermined number of steps, the exposure is suitable for focus detection. Therefore, the exposure control for focus detection may be performed.

  In the above-described embodiment, the lens driving amount of the focus lens 32 is calculated after the shutter release button is pressed halfway. However, the lens driving amount is calculated before the shutter release button is pressed halfway. It is good also as a structure to keep. Accordingly, it is possible to save time for calculating the lens driving amount of the focus lens 32 after the shutter release button is half-pressed. Therefore, the time from when the shutter release button is half-pressed until the focus lens 32 is driven. Time can be further reduced. Even when the driving amount of the focus lens 32 is calculated before the shutter release button is half-pressed, the drive of the focus lens 32 before the shutter release button is half-pressed is prohibited. .

  Further, in the above-described embodiment, when the shutter release button is half-pressed, exposure control for focus detection is performed based on the reliability of the defocus amount calculated before the shutter release button is half-pressed. For example, when a button for starting the focus adjustment of the optical system is provided separately from the shutter release button, a button for starting the focus adjustment is provided. The defocus amount is calculated before the button is pressed, and when the button for starting focus adjustment is pressed, the reliability of the defocus amount calculated before the button for starting focus adjustment is pressed. Based on this, it may be configured to determine whether or not to perform exposure control for focus detection.

  In addition, in the above-described embodiment, the reliability of the defocus amount calculated before the defocus amount immediately before the shutter release button is half-pressed is determined retroactively by a predetermined number. For example, the reliability of the defocus amount calculated up to a predetermined time (for example, 0.1 second) before the defocus amount immediately before the shutter release button is half-pressed is determined retrospectively. It is good also as a structure.

  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 (5)

A pair of light receiving sensors for receiving a pair of light beams via an optical system having a focus adjusting optical system;
A phase difference detection unit that detects an image plane shift amount by the optical system based on outputs of the pair of light receiving sensors;
A focus adjustment unit that adjusts the focus of the optical system by driving the focus adjustment optical system in the optical axis direction;
An activation unit that activates focus adjustment by the focus adjustment unit;
A storage unit for storing a deviation amount detected by the phase difference detection unit;
An exposure control unit that performs exposure control of the pair of light receiving sensors based on an exposure control value including an exposure time, an imaging sensitivity, and an aperture value;
The first threshold value, which is a threshold value for the reliability of the shift amount, is set to a shift amount after focus adjustment by performing focus adjustment based on the shift amount when the reliability of the shift amount is equal to or greater than the first threshold value. A first threshold value setting unit that sets a threshold value that can be determined to be within the range of the depth of field of the subject;
The second threshold value, which is a threshold value for the reliability of the deviation amount, is a direction in which an in-focus position exists in the optical axis direction based on the deviation amount when the reliability of the deviation amount is less than the second threshold value. A second threshold value setting unit that sets the threshold value so that it can be determined,
Whether the reliability of the shift amount detected before starting the focus adjustment is greater than or equal to the first threshold when the focus adjustment is started by the starter, and Determining means for determining whether or not it is less than a second threshold;
When it is determined that the reliability of the shift amount detected before starting the focus adjustment is equal to or greater than the first threshold, the focus adjustment is performed without causing the exposure control unit to change the exposure control value. A first control unit that causes the focus adjustment unit to drive the focus adjustment optical system based on the shift amount detected before starting
When the reliability of the shift amount detected before starting the focus adjustment is less than the first threshold and greater than or equal to the second threshold, the aperture value of the optical system remains fixed. The exposure controller determines whether or not the exposure is suitable for focus detection by changing at least one of the exposure time and the imaging sensitivity. If the exposure is suitable for focus detection, the exposure control unit When the exposure control is performed by changing at least one of the exposure time and the imaging sensitivity while the aperture value of the optical system is fixed, and the exposure is not suitable for focus detection, the exposure control is performed. A second controller that controls exposure by changing at least one of the exposure time and the imaging sensitivity in addition to the aperture value of the optical system;
When the reliability of the shift amount detected before starting the focus adjustment is less than the second threshold value, the exposure control unit does not fix the aperture value of the optical system without fixing the aperture value. And a third control unit that controls exposure by changing at least one of a value, the exposure time, and the imaging sensitivity. The focus adjustment apparatus according to claim 1,
The second control unit is brighter by a predetermined number of steps than the optimum exposure for focus detection when at least one of the exposure time and the imaging sensitivity is changed while the aperture value of the optical system is fixed. Even if the exposure or exposure is dark by a predetermined number of steps, it is determined that the exposure is suitable for focus detection, and the exposure control unit keeps the aperture value of the optical system fixed in the exposure control unit. A focus adjustment device that controls exposure by changing at least one of them. The focusing apparatus according to claim 1 or 2,
An imaging unit that captures an image by the optical system and outputs an image signal corresponding to the captured image;
A contrast detection unit that detects a focus state of the optical system by calculating an evaluation value related to the contrast of the image by the optical system based on the image signal output by the imaging unit;
The pair of light receiving sensors are provided on a light receiving surface of the image pickup unit. In the focus adjustment apparatus according to any one of claims 1 to 3,
The focus adjustment apparatus, wherein the phase difference detection unit detects the shift amount regardless of whether or not the focus adjustment is activated.   The imaging device provided with the focus adjustment apparatus in any one of Claims 1-4.

Images