JP5434992B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus.

  2. Description of the Related Art Conventionally, there has been known an image pickup apparatus that detects a focus state of an optical system by detecting a shift amount of an image plane of the optical system based on an output of a focus detection pixel provided in the image pickup element. As such an imaging device, for example, in order to prevent vignetting when performing focus detection, the aperture value of the optical system is set to a value (open side value) smaller than a predetermined aperture value, A method of performing focus detection is known (for example, Patent Document 1).

JP 2010-217618 A

  However, in the prior art, when the aperture value of the optical system is changed from the aperture value at the time of focus detection to the imaging aperture value in order to actually capture an image, the image plane of the optical system is changed along with the change of the aperture value. Moved, and as a result, there was a case where an image focused on the subject could not be taken.

  The problem to be solved by the present invention is to provide an imaging apparatus capable of capturing an image satisfactorily.

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

[1] An imaging apparatus according to a first aspect of the present invention includes an imaging unit (22) that captures an image by an optical system including a focus adjustment optical system (32) and outputs an image signal corresponding to the captured image. , based on the previous SL image signals, the focus detection unit which detects a focus state of the optical system (21), on the basis of the focus detection result of the focus detection unit, drives the focal optics in the optical axis direction Thus, in a state where the aperture value of the focus adjustment unit (36) that performs the focus adjustment of the optical system and the aperture value (34) that restricts the light beam that passes through the optical system and enters the imaging unit is set to the open aperture value. , Causing the focus detection unit to perform focus detection, causing the focus adjustment unit to start driving the focus adjustment optical system based on the focus detection result, and narrowing down the aperture while driving the focus adjustment optical system The focus detection unit in a state where the aperture is stopped Control unit to perform focus detection (21), obtains a limit value of the open side of the aperture value of the aperture the at the time of performing focus detection by the focus detection unit, the lens barrel (3) as an open side limit value An acquisition unit (21), and when the control unit is able to acquire the open side limit value from the lens barrel, the aperture value of the diaphragm is set to the open side limit value, The focus detection unit performs focus detection, and based on the focus detection result, causes the focus adjustment unit to start driving the focus adjustment optical system, and narrows down the aperture during the drive of the focus adjustment optical system, If the focus detection unit performs focus detection with the aperture stopped, and the aperture state of the aperture is set to the open side limit value, and the focus state of the optical system cannot be detected, the aperture The aperture value of A point detection unit that performs focus detection, and based on the focus detection result, causes the focus adjustment unit to start driving the focus adjustment optical system, and narrows down the diaphragm while the focus adjustment optical system is being driven, A control operation for causing the focus detection unit to perform focus detection is performed in a state where the aperture is stopped .

[2] An imaging device according to a second aspect of the present invention is based on the imaging unit (22) that captures an image by an optical system including a focus adjustment optical system (32) and outputs an imaging signal, and the imaging signal. A focus detection unit (21) for detecting a focus adjustment state of the optical system, and a control unit (21) for driving and controlling the focus adjustment optical system in the optical axis direction based on a focus detection result by the focus detection unit; An acquisition unit (21) for acquiring, from the lens barrel, an open-side limit value of the aperture value of the aperture (34) when focus detection is performed by the focus detection unit, and the control And when the focus adjustment state of the optical system can be detected in a state where the aperture value of the aperture is set to the open side limit value, the focus is based on the focus adjustment state detected by the focus detection unit. Start driving control of the adjusting optical system, and The aperture is narrowed down during driving of the optical saving system, the focus detection state is detected by the focus detection unit in a state in which the aperture is stopped, and the aperture value of the aperture is set to the open side limit value. When the focus adjustment state of the system cannot be detected, drive control of the focus adjustment optical system is started based on the focus adjustment state detected by the focus detection unit with the aperture value of the aperture set to the open aperture value And performing a control operation of causing the focus detection unit to detect a focus adjustment state in a state in which the aperture is reduced while the focus adjustment optical system is being driven .

[3] In the invention relating to the imaging apparatus, the control unit (21) may open the aperture value of the aperture (34) when the acquisition unit (21) fails to acquire the open limit value. In a state where the aperture value is set, drive control of the focus adjustment optical system (32) is started based on the focus adjustment state detected by the focus detection unit (21), and the diaphragm is driven while the focus adjustment optical system is being driven. It is possible to perform a control operation for causing the focus detection unit to detect a focus adjustment state in a state where the aperture is reduced.

[4] In the invention relating to the imaging apparatus, the illumination unit that illuminates the subject with the illumination light, and the luminance of the subject are detected, and whether the illumination by the illumination unit is necessary is determined based on the detected luminance of the subject. And a control unit (21) configured to perform the control operation when it is determined that illumination by the illumination unit is necessary .

[ 5 ] In the invention relating to the imaging apparatus, the control unit (21) may determine that the aperture value of the optical system is a shooting aperture value at the time of shooting an image while the focus adjustment optical system (32) is being driven. Thus, the diaphragm (34) can be configured to be narrowed.

[ 6 ] In the invention related to the imaging apparatus, the storage unit further stores a restriction value on the narrowing side of the aperture value of the optical system when performing focus detection by the focus detection unit (21) as a restriction value on the narrowing side. The control unit (21) is configured to drive the focus adjustment optical system (32) when the imaging aperture value at the time of capturing an image is a value closer to the aperture than the aperture limit value. The aperture (34) can be narrowed down so that the aperture value of the optical system becomes the aperture limit value.

[ 7 ] In the invention relating to the imaging apparatus, the imaging unit (22) includes a plurality of imaging pixels (221) arranged in a two-dimensional manner and a one-dimensional or two-dimensional configuration mixed with the imaging pixels. A plurality of focus detection pixels (222a, 222b) arranged on the focus detection unit (21), and the focus detection unit (21) generates an image by the optical system based on the image signal output from the focus detection pixels. Based on the phase difference detection type focus detection for detecting the focus state of the optical system by detecting the amount of deviation of the surface, and the image signal output by the imaging pixels, the image of the image by the optical system is detected. An evaluation value related to contrast is calculated, and based on the calculated evaluation value, focus detection is performed by at least one of the focus detection methods of the contrast detection method that detects the focus state of the optical system. It can be configured to be.

  According to the present invention, an image can be taken satisfactorily.

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 showing the operation of the camera according to the present embodiment. FIG. 10 is a diagram illustrating an example of the relationship between the aperture value at the time of focus detection set in the present embodiment and the photographing aperture value.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a main part configuration diagram showing a digital camera 1 according to an embodiment of the present invention. A digital camera 1 according to the present embodiment (hereinafter simply referred to as a camera 1) includes a camera body 2 and a lens barrel 3, and the camera body 2 and the lens barrel 3 are detachably coupled by a mount unit 4. Yes.

  The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. As shown in FIG. 1, the lens barrel 3 includes a photographic optical system including lenses 31, 32, 33 and a diaphragm 34.

  The lens 32 is a focus lens, and can adjust the focal length of the photographing optical system by moving in the direction of the optical axis L1. The focus lens 32 is provided so as to be movable along the optical axis L1 of the lens barrel 3, and its position is adjusted by the focus lens drive motor 36 while its position is detected by the encoder 35.

  The specific configuration of the moving mechanism along the optical axis L1 of the focus lens 32 is not particularly limited. For example, a rotating cylinder is rotatably inserted into a fixed cylinder fixed to the lens barrel 3, a helicoid groove (spiral groove) is formed on the inner peripheral surface of the rotating cylinder, and the focus lens 32 is fixed. The end of the lens frame is fitted into the helicoid groove. Then, by rotating the rotating cylinder by the focus lens drive motor 36, the focus lens 32 fixed to the lens frame moves straight along the optical axis L1.

  As described above, the focus lens 32 fixed to the lens frame by rotating the rotary cylinder with respect to the lens barrel 3 moves straight in the direction of the optical axis L1, but the focus lens drive motor 36 as the drive source is the lens. The lens barrel 3 is provided. The focus lens drive motor 36 and the rotary cylinder are connected by a transmission composed of a plurality of gears, for example, and when the drive shaft of the focus lens drive motor 36 is driven to rotate in any one direction, it is transmitted to the rotary cylinder at a predetermined gear ratio. Then, when the rotating cylinder rotates in any one direction, the focus lens 32 fixed to the lens frame moves linearly in any direction of the optical axis L1. When the drive shaft of the focus lens drive motor 36 is rotated in the reverse direction, the plurality of gears constituting the transmission also rotate in the reverse direction, and the focus lens 32 moves straight in the reverse direction of the optical axis L1. .

  The position of the focus lens 32 is detected by the encoder 35. As described above, the position of the focus lens 32 in the optical axis L1 direction correlates with the rotation angle of the rotating cylinder, and can be obtained by detecting the relative rotation angle of the rotating cylinder with respect to the lens barrel 3, for example.

  As the encoder 35 of this embodiment, an encoder that detects the rotation of a rotating disk coupled to the rotational drive of the rotating cylinder with an optical sensor such as a photo interrupter and outputs a pulse signal corresponding to the number of rotations, or a fixed cylinder And the contact point of the brush on the surface of the flexible printed wiring board provided on either one of the rotating cylinders, and the brush contact provided on the other, the amount of movement of the rotating cylinder (in either the rotational direction or the optical axis direction) A device that detects a change in the contact position according to the detection circuit using a detection circuit can be used.

  The focus lens 32 can move in the direction of the optical axis L1 from the end on the camera body side (also referred to as the closest end) to the end on the subject side (also referred to as the infinite end) by the rotation of the rotating cylinder described above. it can. Incidentally, the current position information of the focus lens 32 detected by the encoder 35 is sent to the camera control unit 21 to be described later via the lens control unit 37, and the focus lens drive motor 36 calculates the focus calculated based on this information. The driving position of the lens 32 is driven by being sent from the camera control unit 21 via the lens control unit 37.

  The diaphragm 34 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light flux that passes through the photographing optical system and reaches the image sensor 22 and to adjust the blur amount. The adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending an aperture diameter corresponding to the aperture value calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the aperture diameter corresponding to the set photographing aperture value is input from the camera control unit 21 to the lens control unit 37 by 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.

  In the present embodiment, the lens control unit 37 stores in advance the limit value on the open side of the aperture value of the optical system when detecting the focus state of the optical system in the memory 39 as the open side limit value. Yes. Here, for example, when the aperture value at the time of detecting the focus state of the optical system is F1.4 and the imaging aperture value at the time of actual imaging of the image is F2.8, the main imaging is performed after the focus detection. In addition, when the aperture value of the optical system is changed from F1.4, which is the aperture value at the time of focus detection, to F2.8, which is the photographing aperture value, the image plane of the optical system is moved along with the change of the aperture value. As a result, the in-focus position detected at the time of focus detection deviates from the depth of field of the optical system at the time of actual image capture, and an in-focus image cannot be captured on the subject that was in focus at the time of focus detection. There is a case. In particular, this tendency increases as the aperture value of the optical system becomes a value on the open side. Therefore, in such a case, for example, by restricting the aperture value at the time of detecting the focus state of the optical system to F2 so that it cannot be F1.4, the amount of image plane movement accompanying the change of the aperture value can be reduced. Even when the aperture value of the optical system is suppressed and the aperture value at the time of detecting the focus state is changed to the imaging aperture value, an image in focus on the subject can be captured. In this way, the open side limit value is an open aperture value of the optical system that can capture a good image even when the aperture value of the optical system is changed from the aperture value at the time of focus detection to the shooting aperture value. This limit value is stored in the memory 39 in advance as a unique value for each lens barrel 3.

  In the present embodiment, the lens control unit 37 stores the open side limit value in the memory 39 as the number of aperture stages from the open aperture value. For example, when the open side limit value is F2 as an aperture value (F value), the open aperture value is F1.2, and the aperture value of the optical system is changed from the open aperture value F1.2 to the open side limit value. When the number of aperture stages of the aperture 34 for changing to F2 is 2, the camera control unit 37 stores the open side limit value as two stages. Thus, by storing the open side limit value as the number of aperture stages from the open aperture value, for example, even when the lens position of the zoom lens is changed, the open aperture value according to the lens position of the zoom lens Based on the above, it is possible to obtain the open side limit value according to the lens position of the zoom lens, and it is not necessary to store the open aperture value for each lens position of the zoom lens. The above-described open aperture value, open side limit value, and number of aperture stages are examples, and are not limited to these values.

  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 photographing optical system by the phase detection method and the focus state of the optical system by the contrast detection method based on the pixel data read from the image sensor 22. Do. A method for detecting the focus state will be described later.

  The operation unit 28 is a shutter release button and an input switch for the photographer to set various operation modes of the camera 1, and can switch between an auto focus mode and a manual focus mode. Various modes set by the operation unit 28 are sent to the camera control unit 21, and the operation of the entire camera 1 is controlled by the camera control unit 21. The shutter release button includes a first switch SW1 that is turned on when the button is half-pressed and a second switch SW2 that is turned on when the button is fully pressed.

  Next, the image sensor 22 according to the present embodiment will be described.

  FIG. 2 is a front view showing the imaging surface of the 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 It shows that light beams AB1-1, AB2-1, AB1-2, and AB2-2 irradiated from the distance measuring pupils 351 and 352 of the exit pupil 350 are received. 8 illustrates only the focus detection pixels 222a and 222b that are located in the vicinity of the photographing optical axis L1, but other focus detection pixels other than the focus detection pixels illustrated in FIG. 8 are illustrated. In the same manner, the light beams emitted from the pair of distance measuring pupils 351 and 352 are respectively received.

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

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

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

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

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

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

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

  Then, 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 focal plane corresponding to the current focal plane (the position corresponding to the position of the microlens array on the planned focal plane). The deviation of the focal plane in the detection area), 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 imaging element 22 using a high-frequency transmission filter. It can also be obtained by extracting high-frequency components using two high-frequency transmission filters having different cutoff frequencies.

  Then, the camera control unit 21 sends a control signal to the lens control unit 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.

  First, in step S101, the camera control unit 21 acquires an open side limit value. Specifically, the camera control unit 21 acquires, from the lens control unit 37, the open side limit value of the aperture value of the optical system when detecting the focus state of the optical system as the open side limit value. In the present embodiment, since the open side limit value is stored in the memory 39 as the number of apertures from the aperture value, the camera control unit 21 sets the aperture value from the aperture value to the aperture value. Based on this, the limit value (F value) on the open side of the aperture value of the optical system when performing focus detection is obtained as the open side limit value.

  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, the process waits in step S102.

  In step S103, the camera control unit 21 determines whether or not the open side limit value has been acquired in step S101. If it is determined that the open side limit value can be acquired, the process proceeds to step S104. On the other hand, if it is determined that the open side limit value cannot be acquired, the process proceeds to step S105. Here, the lens barrel 3 according to the present embodiment stores the open side limit value in the memory 39, and the camera control unit 21 acquires the open side limit value via the lens control unit 37. Therefore, the process proceeds to step S104. On the other hand, depending on the type of the lens barrel, there is a lens barrel that does not store the open side limit value. When such a lens barrel is used, the camera control unit 21 opens the lens barrel from the open side. The limit value cannot be obtained. In such a case, it is determined that the open side limit value cannot be acquired, and the process proceeds to step S105.

  In step S104, since the open side limit value is acquired, the camera control unit 21 sets the aperture value (F value) of the optical system to the open side limit value. Here, FIG. 10 is a diagram illustrating an example of the relationship between the aperture value set for performing focus detection and the imaging aperture value. In the example shown in FIG. 10, in the lens barrel 3 having the maximum aperture value of F1.2 and the maximum aperture value (maximum F value) of F16, the open side limit value is acquired as F2.8. Is shown. In step S104, since the open side limit value is acquired, as shown in FIG. 10A, the aperture value of the optical system is set to F2.8, which is the open side limit value.

  On the other hand, if it is determined in step S103 that the open side limit value could not be acquired, the process proceeds to step S105, where the camera control unit 21 sets the aperture value (F value) of the optical system to the open aperture value. The For example, in step S105, as shown in FIG. 10B, the aperture value of the optical system is set to F1.2 which is the full aperture value.

  In step S106, the camera control unit 21 performs exposure control for focus detection. 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, A luminance value SpotBv within a predetermined area including the focus detection area is calculated. Then, the camera control unit 21 controls the exposure with respect to the image sensor 22 so that an exposure suitable for focus detection (for example, an exposure one step brighter than the appropriate exposure) is obtained based on the calculated luminance value SpotBv. .

  In the exposure control in step S106, when the aperture value of the optical system is set to the open side limit value in step S104, the camera control unit 21 receives the light while keeping the aperture Av according to the open side limit value. Exposure to the image sensor 22 is controlled by changing at least one of the sensitivity Sv and the exposure time Tv. Similarly, when the aperture value of the optical system is set to the open aperture value in step S105, the camera control unit 21 keeps the aperture Av according to the open aperture value, out of the light receiving sensitivity Sv and the exposure time Tv. By changing at least one, exposure to the image sensor 22 is controlled.

  In step S107, the camera control unit 21 performs a defocus amount calculation process using a phase difference detection method. Specifically, first, a light beam from the optical system is received by the image sensor 22, and each focus detection pixel 222 a configuring the three focus detection pixel rows 22 a to 22 c of the image sensor 22 by the camera control unit 21. , 222b, 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. Further, the camera control unit 21 evaluates the reliability of the calculated defocus amount. For example, the camera control unit 21 can determine the reliability of the defocus amount based on the matching degree and contrast of the pair of image data.

  In step S108, the camera control unit 21 calculates and calculates the lens driving amount necessary to drive the focus lens 32 to the in-focus position based on the defocus amount calculated in step S107. The lens driving amount is sent to the focus lens driving motor 36 via the lens control unit 37. Thereby, the focus lens driving motor 36 starts driving the focus lens 32 based on the calculated lens driving amount.

  When the drive of the focus lens 32 is started, the process proceeds to step S109, and in step S109, the camera control unit 21 sets the aperture value of the optical system to the photographing aperture value. For example, in FIG. 10A, in step S104, the aperture value of the optical system is set to F2.8, which is the open-side aperture value, but in step S109, the aperture value of the optical system is set to the photographing aperture. The value is set to F4. In FIG. 10B, the aperture value of the optical system is set to F1.2 which is the open aperture value in step S105, but the aperture value of the optical system is set to the photographing aperture value in step S109. Is set to F4.

  In step S110, as in step S106, the camera control unit 21 performs exposure control for focus detection. Specifically, the camera control unit 21 calculates a luminance value SpotBv within a predetermined region including the focus detection area, and calculates the calculated luminance value SpotBv and the aperture Av corresponding to the imaging aperture value set in step S109. Based on the light reception sensitivity Sv and the exposure time Tv, the shutter speed of the shutter 23 and the image pickup sensitivity of the image sensor 22 are set based on the determined light reception sensitivity Sv and exposure time Tv. In step S110, as in step S104, exposure control for the image sensor 22 is performed by changing the light receiving sensitivity Sv and the exposure time Tv while fixing the aperture Av corresponding to the imaging aperture value set in step S109. Is done.

  In step S111, the defocus amount is calculated in a state where the aperture value of the optical system is set to the photographing aperture value. In subsequent step S112, the focus lens is calculated based on the defocus amount calculated in step S111. 32 driving is executed.

  In step S113, the camera control unit 21 performs in-focus determination. Specifically, the camera control unit 21 determines whether or not the calculated absolute value of the defocus amount is equal to or smaller than a predetermined value, and when the calculated absolute value of the defocus amount is equal to or smaller than the predetermined value. Determines that the focus state of the optical system is the in-focus state, and proceeds to step S114. On the other hand, if the calculated absolute value of the defocus amount is larger than the predetermined value, the focus is not achieved. If it is determined, the process returns to step S111, and the calculation of the defocus amount and the driving of the focus lens 32 based on the calculated defocus amount are repeated.

  If it is determined in step S113 that the subject is in focus, the process proceeds to step S114, and the camera control unit 21 determines whether or not the shutter release button has been fully pressed (the second switch SW2 is turned on). If the second switch SW2 is on, the process proceeds to step S115. On the other hand, if the second switch SW2 is not on, the process returns to step S102.

  In step S <b> 115, an image is captured by the image sensor 22, and the captured image data is stored in the memory 24. In this embodiment, since the aperture value of the optical system is set to the shooting aperture value in step S109, an image is shot with the shooting aperture value unchanged.

  As described above, in this embodiment, when the open side limit value cannot be acquired from the lens barrel 3, the aperture value of the optical system is set to the open aperture value, focus detection is performed, and based on the focus detection result. Then, the driving of the focus lens 32 is started, and while the focus lens 32 is being driven, the aperture value of the optical system is changed from the open aperture value to the photographing aperture value, and focus detection is performed. As described above, in the present embodiment, first, the aperture value of the optical system is set to the open aperture value, and focus detection is performed, so that the focus state of the optical system is appropriately detected even when the luminance of the subject is low. In addition, while the focus lens 32 is being driven, the aperture value of the optical system is set to the photographing aperture value, and focus detection is performed, thereby focusing on focus detection due to a change in the image plane accompanying the change of the aperture value. Thus, it is possible to effectively prevent the subject that is in focus from being out of focus during shooting, and it is possible to appropriately shoot an image that is in focus on the subject.

  In the present embodiment, when the open limit value can be obtained from the lens barrel 3, focus detection is performed by setting the aperture value of the optical system to the open limit value instead of the open stop value. . Thereby, in this embodiment, when the aperture value of the optical system is changed from the open side limit value to the shooting aperture value, the amount of movement of the image plane of the optical system can be set to a predetermined value or less, and the open side The focus position detected by the limit value can be set within the range of the depth of field at the time of shooting. For this reason, in the present embodiment, even when the in-focus position cannot be detected with the photographing aperture value, an image in which the subject is in focus can be captured.

  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 the open-side limit value can be acquired from the lens barrel 3, as shown in FIG. 10A, the aperture value of the optical system is set to the open-side limit value, The configuration in which focus detection is performed and the aperture 34 is narrowed down so that the aperture value of the optical system becomes the shooting aperture value during driving of the focus lens 32 based on the focus detection result has been illustrated. Even when the side limit value can be obtained, the aperture value of the optical system is set to the open aperture value, focus detection is performed, and the aperture value of the optical system is opened while the focus lens 32 is driven based on the focus detection result. The diaphragm 34 may be narrowed down so that the same value as the side limit value or a value closer to the narrower side than the open side limit value. For example, as shown in FIG. 10C, even when the open limit value can be acquired as F2.8, the aperture value of the optical system is set to F1.2 which is the open aperture value, and focus detection is performed. Do. Then, during the driving of the focus lens 32 based on the focus detection result, the aperture value of the optical system is the same value as F2.8 which is the open side limit value, or more than F2.8 which is the open side limit value. The diaphragm 34 is narrowed so that the value on the narrowing side is obtained, and focus detection is performed. For example, in FIG. 10C, while the focus lens 32 is being driven, focus detection is performed by setting the aperture value of the optical system to F3.5, which is a value closer to the aperture side than the open side limit value. Then, when shooting an image, the aperture value of the optical system is set to F4, which is the shooting aperture value, and the image is shot. As a result, the amount of image plane movement when shifting from focus detection to main shooting can be set to a predetermined value or less, and an image in focus on the subject can be shot.

  In the above-described embodiment, when the open limit value can be acquired from the lens barrel 3, the aperture value of the optical system is set to the open limit value, and the focus detection is performed. In addition to the configuration, if the focus state of the optical system cannot be detected with the aperture value of the optical system set to the open limit value, the focus value is detected by changing the aperture value of the optical system to the open aperture value. It is good also as composition which performs. Thereby, the focus state of the optical system can be detected more appropriately when the luminance of the subject is low.

  Furthermore, in the above-described embodiment, the configuration in which the limit value on the open side of the aperture value of the optical system when performing focus detection is illustrated as the open side limit value. However, for example, when performing focus detection, A limit value on the aperture side of the aperture value of the optical system may be stored in advance in a memory provided in the camera control unit 21 as a limit value on the aperture side, and focus detection may be performed based on the limit value on the aperture side. . It should be noted that the narrowing-side limit value is, for example, the most narrow-side value among aperture values that can effectively prevent the occurrence of vignetting and obtain good focus detection accuracy when performing focus detection. can do. For example, as shown in FIG. 10D, in the scene where the narrowing limit value is stored as F5.6 and the photographing aperture value is set as F8, the photographing aperture value F8 is the narrowing side. It is a value closer to the narrower side than the limit value F5.6. In such a case, the focus value is detected by limiting the aperture value of the optical system during driving of the focus lens 32 to F5.6 which is the limit value on the aperture side, thereby effectively preventing vignetting during focus detection. Therefore, the focus state of the optical system can be detected appropriately. In this case, after focus detection, the aperture value of the optical system is set to F8, which is the shooting aperture value, and the actual shooting of the image is performed with the set shooting aperture value.

  In the above-described embodiment, focus detection is performed by setting the aperture value of the optical system to the open side limit value or the open aperture value, and when the focus lens 32 starts to be driven based on the focus detection result, Although the configuration in which the aperture value of the optical system is set to the shooting aperture value is exemplified, for example, the aperture value of the optical system is changed from the open side limit value or the open aperture value while the focus lens 32 is being driven. The diaphragm 34 may be gradually narrowed so as to gradually change. Further, when the aperture limit value is stored, and the photographing aperture value is closer to the aperture side than the aperture limit value, the aperture value of the optical system is set to the open side limit while the focus lens 32 is being driven. A configuration may be adopted in which the diaphragm 34 is gradually narrowed so as to gradually change from the value or the open diaphragm value to the narrowing limit value.

  In addition, the camera body 2 is provided with an illumination light irradiation unit for irradiating the subject with illumination light, and the camera control unit 21 needs to irradiate the illumination light with the illumination light irradiation unit based on the luminance of the subject. Only when it is determined that the operation of the camera 1 described above is performed.

  In addition, in the above-described embodiment, the configuration in which focus detection is performed by the phase difference detection method has been illustrated. However, in addition to this configuration, focus detection by the contrast detection method may be performed. Alternatively, focus detection by phase difference detection may be performed with priority, and focus detection by a contrast detection method may be performed when focus detection by phase difference detection is not possible. Furthermore, while driving the focus lens 32, the focus detection by the phase difference detection method and the focus detection by the contrast detection method are simultaneously performed, and the focus drive is performed based on the focus detection result by the method in which the focus detection is completed. It is good.

  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 28 ... Operation part 3 ... Lens barrel 32 ... Focus lens 36 ... Focus lens drive motor 37 ... Lens Control unit

Claims (7)

An imaging unit that captures an image by an optical system including a focus adjustment optical system and outputs an image signal corresponding to the captured image ;
Based on the previous SL image signal, and a focus detection unit which detects a focus state of said optical system,
A focus adjustment unit that performs focus adjustment of the optical system by driving the focus adjustment optical system in an optical axis direction based on a focus detection result by the focus detection unit;
The focus detection unit is configured to perform focus detection in a state where the aperture value of the aperture that restricts the light beam that passes through the optical system and enters the imaging unit is an open aperture value, and the focus is determined based on the focus detection result. A control unit that causes the adjustment unit to start driving the focus adjustment optical system, narrows down the diaphragm while the focus adjustment optical system is being driven, and causes the focus detection unit to perform focus detection in a state in which the diaphragm is reduced. When,
An acquisition unit that acquires, as an open side limit value, a limit value on the open side of the aperture value of the aperture when performing focus detection by the focus detection unit;
The controller is
When the open side limit value can be obtained from the lens barrel, the focus detection unit performs focus detection in a state where the aperture value of the aperture is set to the open side limit value, and the focus detection result Based on this, the focus adjustment unit starts to drive the focus adjustment optical system, the aperture is narrowed down while the focus adjustment optical system is being driven, and the focus detection unit detects the focus in a state where the aperture is reduced. Let
If the focus state of the optical system cannot be detected with the aperture value of the aperture set to the open side limit value, the focus detection unit performs focus detection using the aperture value of the aperture as the open aperture value. Based on the focus detection result, the focus adjustment unit starts driving the focus adjustment optical system, and when the focus adjustment optical system is driven, the aperture is narrowed down, and the aperture is in a reduced state, An image pickup apparatus that performs a control operation for causing the focus detection unit to perform focus detection . An imaging unit that captures an image by an optical system including a focus adjustment optical system and outputs an imaging signal;
A focus detection unit that detects a focus adjustment state of the optical system based on the imaging signal;
A control unit that drives and controls the focus adjustment optical system in an optical axis direction based on a focus detection result by the focus detection unit;
An acquisition unit that acquires, as an open side limit value, a limit value on the open side of the aperture value of the aperture when performing focus detection by the focus detection unit;
The controller is
When the focus adjustment state of the optical system can be detected in a state where the aperture value of the stop is the open side limit value, the focus adjustment optical system is based on the focus adjustment state detected by the focus detection unit. The drive control is started, the diaphragm is narrowed down while the focus adjustment optical system is being driven, and the focus detection state is detected by the focus detection unit in a state where the diaphragm is stopped,
If the focus adjustment state of the optical system cannot be detected when the aperture value of the aperture is set to the open limit value, the focus detection unit detects that the aperture value of the aperture is set to the open aperture value. Based on the focus adjustment state, the drive control of the focus adjustment optical system is started, the aperture is narrowed down while the focus adjustment optical system is being driven, and the focus detection unit is adjusted in the state where the aperture is reduced. An imaging apparatus characterized by performing a control operation for detecting a state. The imaging apparatus according to claim 2,
The control unit is configured based on the focus adjustment state detected by the focus detection unit in a state where the aperture value of the aperture is set to the open aperture value when the acquisition unit cannot acquire the open side limit value. A control operation of starting the drive control of the focus adjustment optical system, narrowing down the diaphragm while the focus adjustment optical system is driven, and causing the focus detection unit to detect the focus adjustment state in a state where the diaphragm is stopped. An imaging device characterized in that it performs. The imaging apparatus according to any one of claims 1 to 3,
An illumination unit that illuminates the subject with illumination light;
A determination unit that detects the luminance of the subject and determines whether illumination by the illumination unit is necessary based on the detected luminance of the subject;
The image pickup apparatus, wherein the control unit performs the control operation when it is determined that illumination by the illumination unit is necessary. The imaging apparatus according to claim 1,
The control unit narrows down the aperture so that the aperture value of the optical system becomes an imaging aperture value for capturing an image during driving of the focus adjustment optical system. An imaging apparatus according to any one of claims 1 to 5 ,
A storage unit that stores a limit value on the aperture side of the aperture value of the optical system when performing focus detection by the focus detection unit;
When the photographing aperture value at the time of capturing an image is a value closer to the aperture side than the aperture-side limit value, the aperture value of the optical system is set during the driving of the focus adjustment optical system. An image pickup apparatus that narrows down the diaphragm so as to be the limit value on the narrowing side. The imaging apparatus according to any one of claims 1 to 6 ,
The imaging unit has a plurality of imaging pixels arranged two-dimensionally, and a plurality of focus detection pixels mixed in the imaging pixels and arranged one-dimensionally or two-dimensionally,
The focus detection unit detects a focus state of the optical system by detecting a shift amount of an image plane by the optical system based on the image signal output from the focus detection pixel. And an evaluation value related to the contrast of the image by the optical system is calculated based on the image signal output from the imaging pixel and the image signal output, and the focus state of the optical system is calculated based on the calculated evaluation value. An image pickup apparatus characterized in that focus detection can be performed by at least one of the focus detection methods of the contrast detection method for detecting the image.

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