JP5776210B2 - Focus adjustment device and imaging device - Google Patents

Description

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

  Conventionally, a technique for detecting the amount of deviation of an image plane by an optical system using a phase difference and performing scan driving of a focus adjustment optical system when the reliability of the detected deviation amount is a predetermined value or less is known. Yes. (For example, Patent Document 1).

JP-A-62-102214

  However, in the prior art, since the scan drive of the focus adjustment optical system is performed in a predetermined drive direction, the scan operation is required when the drive direction of the scan drive is opposite to the in-focus position. There was a problem that time would be long.

  The problem to be solved by the present invention is to provide a focus adjustment device capable of reducing the time required for focus detection.

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

[1] The focus adjustment apparatus according to the present invention is configured to capture an image by an optical system having a focus adjustment optical system (32) and output an image signal corresponding to the captured image, and the optical system. A phase difference detection unit (21) for detecting a phase difference between a pair of image signals based on light beams passing through different areas of the image, and based on the image signal output from the imaging unit, the contrast of the image by the optical system is determined. A contrast detection unit (21) for detecting, a shift amount detection unit for detecting a shift amount from an in-focus position of the image by the optical system based on the phase difference of the image signal, and an image by the optical system are focused. A notifying unit (26) for notifying the photographer of the fact that the image is being taken, and a reliability evaluating unit (21) for evaluating the reliability of the shift amount based on the phase difference of the image signal or the contrast of the image, , The focusing optical system with the optical axis A focus adjustment unit (36) that adjusts the focus state of the optical system by driving in the direction, and a control unit (21) that controls the notification unit and the focus adjustment unit. When the reliability of the shift amount is equal to or greater than a first threshold, the focus adjustment optical system is driven by the focus adjustment unit based on the shift amount, and the reliability of the shift amount is When the threshold value is less than 1, the focus adjustment unit causes the focus adjustment optical system to perform scan driving, and the control unit has a reliability of the shift amount equal to or greater than the first threshold value. And when it is more than the 2nd threshold higher than the 1st threshold, when the focus state of the optical system turns into an in-focus state, it reports to the informing part to the informing part. The reliability of the deviation amount is less than the first threshold value, and , If it is more than lower third threshold than the first threshold value, a direction in which the shift amount is small, and determining a driving direction of the scan driver.

  [2] In the invention related to the focus adjustment device, the controller (21) has a tendency that the reliability of the shift amount calculated during the scan drive of the focus adjustment optical system (32) tends to be reduced. When it is determined, the driving direction of the scan driving can be reversed.

[ 3 ] In the invention related to the focus adjustment device, the control unit (21) may detect the deviation of the focus adjustment optical system (32) when a deviation amount having a reliability equal to or higher than the first threshold is detected. It can be configured to prohibit scan driving.

[ 4 ] An imaging apparatus according to the present invention includes the focus adjustment apparatus.

  According to the present invention, the time required for focus detection can be shortened.

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 S108.

  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.

  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, for example, by extracting a high-frequency component of an image output from the imaging pixel 221 of the image sensor 22 using a high-frequency transmission filter and integrating the extracted high-frequency components to detect a focus voltage. It can also be obtained by extracting high-frequency components using two high-frequency transmission filters having different cutoff frequencies and integrating them to detect the focus voltage.

  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 view the moving 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 determines whether or not the shutter release button provided in the operation unit 28 is half-pressed (the first switch SW1 is turned on). If the shutter release button is pressed halfway, the process proceeds to step S103. On the other hand, if the shutter release button is not half-pressed, step S102 is repeated until the shutter release button is half-pressed. That is, generation and display of a through image is repeatedly executed until the shutter release button is pressed halfway.

  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 calculated defocus amount. In the present embodiment, the camera control unit 21 sets the reliability of the defocus amount to “high”, “medium”, “low”, and “ranging” based on, for example, the degree of coincidence and contrast of a pair of image data Evaluation is based on four levels, “impossible”. Specifically, the camera control unit 21 can evaluate the reliability of the defocus amount as described below.

  That is, when the degree of coincidence between the pair of image data is high and the reliability of the defocus amount is equal to or higher than the first determination value, the camera control unit 21 has high accuracy and the defocus amount is high. When the focus lens 32 is driven based on the amount, it can be determined that the focus lens 32 can be expected to be driven to the in-focus position, and the reliability of the defocus amount can be evaluated as “high”.

  In addition, when the reliability of the defocus amount is less than the first determination value and greater than or equal to the second determination value that is smaller than the first determination value, the camera control unit 21 determines the defocus amount. The accuracy of the amount is not higher than when the reliability of the defocus amount is “high”, but when the focus lens 32 is driven based on the defocus amount, the focus position of the focus lens 32 is set. It can be determined that driving to the vicinity of the in-focus position including it can be expected, and the reliability of the defocus amount can be evaluated as “medium”.

  Furthermore, when the reliability of the defocus amount is less than the second determination value and greater than or equal to the third determination value smaller than the second determination value, the camera control unit 21 determines the defocus amount. When the focus lens 32 is driven based on the amount, it cannot be expected to drive the focus lens 32 to the vicinity of the in-focus position, but the direction in which the in-focus position exists is detected based on the defocus amount. Therefore, the reliability of the defocus amount can be evaluated as “low”.

  In addition, when the reliability of the defocus amount is less than the third determination value, the camera control unit 21 is also expected to detect the direction in which the in-focus position is located based on the defocus amount. The reliability of the defocus amount can be evaluated as “incapable of distance measurement” by judging that it is impossible.

  The first determination value, the second determination value, and the third determination value used when evaluating the defocus amount are set so that the above-described evaluation can be performed on the reliability of the defocus amount. Is. The first determination value, the second determination value, and the third determination value may be unique values set in advance, or may be different values depending on the magnitude of the defocus amount. . For example, when the first determination value, the second determination value, and the third determination value are different values depending on the defocus amount, the smaller the defocus amount, The first determination value, the second determination value, and the third determination value can be increased.

  Note that the calculation of the defocus amount and the evaluation of the defocus amount by such a phase difference detection method are repeatedly executed at predetermined intervals while the operation of the camera 1 is being performed.

  In step S104, the camera control unit 21 determines whether the reliability of the defocus amount is “high”. If it is determined that the reliability of the defocus amount is “high”, the process proceeds to step S116, whereas if it is determined that the reliability of the defocus amount is not “high”, the process proceeds to step S105.

  If it is determined in step S104 that the reliability of the defocus amount is “high”, the process proceeds to step S116. In step S116, the camera control unit 21 performs a process for prohibiting the scanning operation. Details of the scanning operation will be described later.

  In step S117, the camera control unit 21 starts calculating the lens driving amount necessary to drive the focus lens 32 to the in-focus position based on the calculated defocus amount. The drive amount is sent to the focus lens drive motor 36 via the lens control unit 37. Next, in step S118, the focus lens driving motor 36 drives the focus lens 32 based on the lens driving amount calculated in step S117. Similar to the calculation of the defocus amount, the calculation of the lens driving amount of the focus lens 32 is repeatedly executed at a predetermined interval, and even during the driving of the focus lens 32, based on the newly calculated lens driving amount. The driving of the focus lens 32 is instructed.

  As described above, in this embodiment, the calculation of the defocus amount started in step S103 is repeatedly performed at predetermined intervals, and the reliability of the newly calculated defocus amount is “high” or “medium”. In some cases, the lens driving amount of the focus lens 32 is newly calculated based on the defocus amount whose reliability is “high” or “medium”, and based on the newly calculated lens driving amount, The focus lens 32 is driven. On the other hand, after the calculation of the defocus amount is started, when the reliability of the newly calculated defocus amount is “low” or “distance cannot be measured”, the scan operation is also executed. The driving amount is not calculated, and the driving of the focus lens 32 is continued based on the defocus amount whose reliability is already “high” or “medium”.

  In step S119, the camera control unit 21 determines whether or not the absolute value of the defocus amount is equal to or less than a predetermined value. Here, this predetermined value is a value by which it can be determined that the in-focus position is within the in-focus range if the absolute value of the defocus amount is equal to or less than the predetermined value. The value to be set. If it is determined that the absolute value of the defocus amount is greater than the predetermined value, it is determined that the in-focus position is not within the in-focus range, and the process returns to step S119, where the absolute value of the defocus amount is equal to or less than the predetermined value. Until then, the calculation of the defocus amount and the driving of the focus lens 32 based on the calculated defocus amount are repeated. On the other hand, if it is determined that the absolute value of the defocus amount is equal to or smaller than the predetermined value, it is determined that the in-focus position is within the in-focus range, and the process proceeds to step S120.

  When the driving of the focus lens 32 to the in-focus position is completed, it is determined that the focus state of the optical system is in the in-focus state, in-focus display is performed in step S120, and then the process proceeds to step S121. Focus lock (processing for prohibiting driving of the focus lens 32) is performed. Note that the in-focus display in step S120 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 described above, when the reliability of the defocus amount is determined to be “high”, the defocus amount is calculated until the absolute value of the defocus amount becomes a predetermined value or less after the scanning operation is prohibited. The focus lens 32 is repeatedly driven based on the calculated defocus amount. When the absolute value of the defocus amount becomes equal to or smaller than the predetermined value (step S119 = Yes), the focus lens 32 is driven to the in-focus position based on the defocus amount with high reliability. After the driving of the focus lens 32 to the in-focus position is completed, the in-focus display is performed.

  If it is determined in step S104 that the defocus amount reliability is not “high”, the process proceeds to step S105. In step S105, the camera control unit 21 determines whether or not the reliability of the defocus amount is “medium”. If it is determined that the reliability of the defocus amount is “medium”, the process proceeds to step S110. On the other hand, if it is determined that the reliability of the defocus amount is not “medium”, the process proceeds to step S106.

  In steps S110 to S113, processing is performed in the same manner as steps S116 to 119. That is, after the scanning operation prohibition process is performed (step S110), the defocus amount calculation started in step S103 is repeatedly performed until the defocus amount becomes a predetermined value or less, and the calculated defocus amount is calculated. The lens driving amount calculation based on (Step S111) and the lens driving based on the calculated lens driving amount (Step S112) are repeatedly performed. When it is determined that the defocus amount is equal to or smaller than the predetermined value (step S113 = Yes), the process proceeds to step S114.

  In step S114, the camera control unit 21 performs a process of stopping the driving of the focus lens 32. Next, in step S115, the camera control unit 21 calculates a defocus amount with high reliability. A determination is made whether or not. If the defocus amount with high reliability is calculated, the process proceeds to step S120, and after focus display is performed, focus lock (processing for prohibiting driving of the focus lens 32) is performed. On the other hand, if the defocus amount with high reliability is not calculated, step S115 is repeated until the defocus amount with high reliability is calculated. Repeatedly.

  As described above, when the reliability of the defocus amount is determined to be “medium”, the defocus amount is calculated until the defocus amount becomes a predetermined value or less, and the focus lens based on the calculated defocus amount. 32 is repeatedly performed, and when the defocus amount is equal to or less than a predetermined value (step S113 = Yes), the in-focus display is displayed until the defocus amount with high reliability is detected. The driving of the focus lens 32 is stopped without performing it. When a defocus amount with high reliability is detected, a focus display is performed, and the focus lens 32 reaches the in-focus position based on the defocus amount with high reliability. Driven.

  If it is determined in step S105 that the reliability of the defocus amount is not “medium”, the process proceeds to step S106. In step S106, the camera control unit 21 determines whether or not the reliability of the defocus amount is “low”. When it is determined that the reliability of the defocus amount is “low”, the process proceeds to step S107, whereas when it is determined that the reliability of the defocus amount is not “low”, the process proceeds to step S108.

  In step S107, the camera control unit 21 performs a process of determining the drive direction of the focus lens 32 in the scanning operation. Specifically, when the reliability of the defocus amount is “low”, the camera control unit 21 determines that the in-focus position exists in a direction in which the defocus amount decreases, and the defocus amount Is determined as the driving direction of scan driving in the scanning operation.

  In step S108, the camera control unit 21 performs a scan operation execution process for executing a 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. If it is determined that the reliability of the defocus amount is “low” and the drive direction of the scan drive is determined in step S107 described above, the scan drive of the focus lens 32 is performed in the determined direction. Do. On the other hand, if the drive direction of the scan drive is not determined in step S107, the scan drive of the focus lens 32 may be performed in a preset direction, for example, from the infinite end to the closest end, or It may be performed from the closest end to the infinite end. Note that the drive direction of scan drive when the drive direction of scan drive is not determined in step S107 may be stored in the memory of the camera control unit 21 or stored in the memory of the lens control unit 37, for example. It may be left.

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

  In step S202, it is determined whether or not the defocus amount has been calculated by the phase difference detection method as a result of the scanning operation performed by the camera control unit 21. If the defocus amount can be calculated, it is determined that distance measurement is possible and the process proceeds to step S207. On the other hand, if the defocus amount cannot be calculated, it is determined that distance measurement is not possible and the process proceeds to step S203. . In step S202, even if the defocus amount can be calculated, if the reliability of the calculated defocus amount is evaluated as “low” or “distance cannot be measured”, the defocus amount is calculated. As a result, it proceeds to step S203.

  In step S203, it is determined whether the in-focus position has been detected by the contrast detection method as a result of the scanning operation performed by the camera control unit 21. If the in-focus position can be detected by the contrast detection method, the process proceeds to step S214. If the in-focus position cannot be detected, the process proceeds to step S204.

  In step S204, the camera control unit 21 determines whether or not the reliability of the defocus amount calculated in the scan operation tends to decrease. For example, if the reliability of a predetermined number of defocus amounts calculated after the start of the scan operation continuously decreases, the camera control unit 21 calculates the defocus calculated after the start of the scan operation. It can be determined that the reliability of the quantity tends to decrease. If it is determined that the reliability of the defocus amount is decreasing, the process proceeds to step S205. On the other hand, if it is determined that the reliability of the defocus amount is not decreasing, the process proceeds to step S206.

  In step S <b> 205, the camera control unit 21 sends a command for reversing the scan driving direction to the reverse direction to the focus lens driving motor 36 via the lens control unit 37. As a result, the focus lens drive motor 36 reverses the drive direction of the focus lens 32 in the reverse direction, and the focus lens 32 is driven in the direction opposite to the previous drive direction.

  In step S <b> 206, the camera control unit 21 determines whether or not the scan operation has been performed for the entire driveable range of the focus lens 32. If the scan operation is not performed for the entire driveable range of the focus lens 32, the process returns to step S202, and steps S202 to S206 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 advances to step S218.

  As a result of executing the scanning operation, if it is determined in step S202 that the defocus amount can be calculated by the phase difference detection method, the process proceeds to step S207, and in steps S207 to S213, 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 S207, the camera control unit 21 performs a scanning operation stop process, and then proceeds to step S208. The camera control unit 21 performs a scanning operation prohibition process.

  In step S209, the lens driving amount necessary 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 S202, 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 controller 21 repeatedly calculates the defocus amount by the phase difference detection method while the lens drive 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 control unit 21 drives the focus lens 32 based on the new defocus amount.

  In step S210, as in step S119, it is determined whether or not the absolute value of the defocus amount is equal to or smaller than a predetermined value. If the absolute value of the defocus amount is equal to or smaller than the predetermined value, the process proceeds to step S211. On the other hand, if the absolute value of the defocus amount is larger than the predetermined value, step S210 is repeated. In the subsequent step S211, it is determined whether or not the defocus amount with high reliability is calculated. If the defocus amount with high reliability is calculated, the reliability is determined. The focus lens 32 is driven to the in-focus position based on the defocus amount with “high”, and the process proceeds to step S212. On the other hand, if it is determined that the defocus amount with high reliability is not calculated, step S211 is repeated until the defocus amount with high reliability is calculated.

  When the drive of the focus lens 32 to the in-focus position is completed, in-focus display is performed in step S212, and then the process proceeds to step S213, where focus lock (processing for prohibiting drive of the focus lens 32) is performed. It is. Note that the focus display in step S212 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 S206 that the in-focus position has been detected by the contrast detection method, the process proceeds to step S214, and is detected by the contrast detection method in steps S214 to S217. Based on the in-focus position, the focus lens 32 is driven.

  That is, first, in step S214, the camera control unit 21 performs a scan operation stop process, and then proceeds to step S215. As in step S209 described above, the camera control unit 21 performs a scan operation prohibition process. It is.

  Then, the process proceeds to step S216, and lens driving processing 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.

  Then, when the driving of the focus lens 32 to the in-focus position is completed, the process proceeds to step S217, in-focus display is performed, and then the process proceeds to step S213, where focus lock (a process for prohibiting driving of the focus lens 32) is performed. Done. Note that the in-focus display in step S217 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 scan operation of the present embodiment, the above-described steps S202 to S206 are repeatedly executed, so that the focus lens 32 is driven to scan, and 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. As a result of repeatedly executing steps S202 to S206 described above, the focus detection result obtained by the detection method in which the defocus amount is 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 this embodiment, after determining whether or not the defocus amount can be calculated by the phase difference detection method (step S202), 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 S206 that the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S218. In step S218, as a result of performing the scanning operation, focus detection could not be performed by any of the phase difference detection method and the contrast detection method. Therefore, the scanning operation end processing is performed, and then in step S219 Advancing and in-focus indication is performed. The in-focus indication is performed by the electronic viewfinder 26, for example.

  In step S220, the camera control unit 21 determines whether or not the state where the shutter release button is half-pressed (the first switch SW1 is turned on) continues. If the shutter release button is half-pressed, the process proceeds to step S221. If the shutter release button is not half-pressed, the process proceeds to step S223.

  If it is determined in step S220 that the shutter release button is half-pressed, the process proceeds to step S221, and whether or not the defocus amount has been calculated by the phase difference detection method as in step S203 described above. A determination is made. As a result, if it is determined that the defocus amount can be calculated, the process proceeds to step S222, a process for turning off the in-focus display is performed, and then the process proceeds to step S209. In steps S209 to S213, the phase difference is determined. A focusing operation based on the defocus amount calculated by the detection method is performed. On the other hand, if it is determined that the defocus amount cannot be calculated, the process returns to step S220, and steps S220 and S221 are repeatedly executed while the shutter release button is being pressed halfway. In this case, since the focus lens 32 is in a stopped state, focus detection by the contrast detection method is not performed, and only focus detection by the phase difference detection method is performed.

  On the other hand, if it is determined in step S220 that the shutter release button is not half-pressed, the process proceeds to step S223, and processing for turning off the in-focus display is performed.

  As described above, when the reliability of the defocus amount is determined to be “low”, the drive direction of the scan drive is determined based on the defocus amount, and the scan drive of the focus lens 32 is performed in the determined drive direction. Is done. As a result of the scanning operation, when the defocus amount having the reliability of “high” or “medium” is calculated by the phase difference detection method, the scan driving is stopped, and the reliability is “high” or “ The focus lens 32 is driven based on the defocus amount “medium”. Further, when the focus position is detected by the contrast detection method as a result of the scan operation, the scan drive is stopped and the focus lens 32 is driven based on the detected focus position. When it is determined that the reliability of the defocus amount is “incapable of distance measurement”, scan driving is performed in a predetermined direction set in advance, and a scan operation is performed.

  As described above, in the present embodiment, when it is determined that the reliability of the defocus amount is “low”, the scan driving direction is set so that the defocus amount with the reliability “low” decreases. The driving direction is determined and the focus lens 32 is scanned. Thereby, for example, when the subject exists on the close side, the scan drive can be performed on the close side without performing the scan drive on the infinity side, so that the time required for the scan operation can be shortened. As a result, the time required for focus detection can be shortened. Further, in the present embodiment, by performing scan driving in the direction in which the in-focus position exists, it is possible to reduce blurring of the captured image due to the scanning operation, and it is possible to improve the usability. Furthermore, in this embodiment, even when the reliability of the defocus amount is low, if the reliability of the defocus amount is “low”, the driving direction of the scan drive is determined based on the defocus amount. Therefore, the wobbling operation for determining the drive direction of the scan drive can be omitted, and the time required for the scan operation can be further shortened.

  Further, in the present embodiment, during the scanning operation, it is determined whether or not the reliability of the defocus amount tends to decrease, and when it is determined that the reliability of the defocus amount tends to decrease, It is determined that the scan drive is performed in the direction opposite to the direction in which the subject exists, and the drive direction of the scan drive is reversed in the reverse direction. Thus, in the present embodiment, for example, when the subject is present on the close side and the scan drive of the focus lens 32 is performed toward the infinity side, the drive direction of the focus lens 32 is reversed. Since the focus lens 32 can be scan-driven toward the closest side where the subject exists, the time required for the scan operation can be further shortened.

  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 configuration for determining the reliability of the defocus amount calculated after the shutter release button is half-pressed is illustrated. However, the defocus calculated before the shutter release button is half-pressed is illustrated. It is good also as a structure which judges the reliability of quantity. In this case, for example, the defocus amount calculated a predetermined number of times before the shutter release button is pressed halfway or the defocus amount calculated a predetermined time before the shutter release button is pressed halfway is read and read. The reliability of the defocus amount thus determined may be determined retroactively. In addition, a predetermined number of defocus amounts (predetermined time) calculated before half-pressing the shutter release button are read, and the lens is determined based on the defocus amount with the highest reliability among the read defocus amounts. It may be configured to calculate the driving amount. Further, the lens driving amount may be calculated before the shutter release button is half-pressed.

  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 (4)

An imaging unit that captures an image by an optical system having a focus adjustment optical system and outputs an image signal corresponding to the captured image;
A phase difference detection unit for detecting a phase difference between a pair of image signals based on light beams passing through different regions of the optical system;
A contrast detection unit that detects a contrast of an image by the optical system based on the image signal output by the imaging unit;
Based on the phase difference of the image signal, a shift amount detection unit that detects a shift amount from an in-focus position of the image by the optical system;
An informing unit for informing the photographer that the image by the optical system is in focus;
A reliability evaluation unit that evaluates the reliability of the shift amount based on the phase difference of the image signal or the contrast of the image;
A focus adjustment unit that adjusts a focus state of the optical system by driving the focus adjustment optical system in an optical axis direction;
A control unit for controlling the notification unit and the focus adjustment unit,
When the reliability of the deviation amount is equal to or greater than a first threshold, the control unit drives the focus adjustment optical system to cause the focus adjustment optical system to drive the focus adjustment optical system based on the deviation amount. When the characteristic is less than the first threshold, the focus adjustment unit is caused to perform scan driving of the focus adjustment optical system,
When the reliability of the deviation amount is not less than the first threshold value and not less than a second threshold value that is higher than the first threshold value, the control unit determines that the focus state of the optical system is When the in-focus state is reached, the informing unit is informed that the in-focus state is present, the reliability of the deviation amount is less than the first threshold value, and more than the first threshold value. If it is equal to or lower than the third threshold value, the focus adjustment device determines the direction in which the shift amount decreases as the drive direction of the scan drive.
The focus adjustment apparatus according to claim 1,
The control unit reverses the drive direction of the scan drive when determining that the reliability of the shift amount calculated during the scan drive of the focus adjustment optical system tends to decrease. Focusing device. The focusing apparatus according to claim 1 or 2 ,
The control unit is configured to prohibit scan driving of the focus adjustment optical system when a deviation amount having a reliability equal to or higher than the first threshold is detected. The imaging device provided with the focus adjustment apparatus in any one of Claims 1-3 .

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