JP2013011762A - Focus detection device and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detection device which can detect a focus state of an optical system appropriately.SOLUTION: An focus detection device comprises: an imager 22 with plural imaging pixels 221 and plural focus detection pixels 221a, 221b; a storage part 21 to store an address of a defect pixel which is a defective pixel among plural focus detection pixels 221a, 222b; an interpolation part 21 to interpolate an output of the defect pixel located at a position corresponding to the address stored in the storage part 21 based on an output of the focus detection pixels 221a,222b located around the defect pixel; and a focus detection part 21 to detect a focus state of an optical system by detecting a shift amount of an image surface by the optical system based on the outputs of plural focus detection pixels 221a,222b including the output of the interpolated defect pixel.

Description

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

  Conventionally, an image sensor has a plurality of focus detection pixels, and based on the output of the focus detection pixels, the amount of deviation of the image plane by the optical system is detected to detect the focus state of the optical system. An apparatus is known (Patent Document 1).

JP 2003-107324 A

  However, in the prior art, since focus detection is performed based on the output of the focus detection pixel, there is a problem that the focus state of the optical system cannot be detected properly if the focus detection pixel has a defect. .

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

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

  [1] A focus detection apparatus according to the present invention includes an image sensor (22) including a plurality of imaging pixels (221) and a plurality of focus detection pixels (222a, 222b), and a plurality of focus detection pixels. A storage unit (21) that stores an address of a defective pixel that is a defective pixel, and an output of the defective pixel that is located at a position corresponding to the address stored in the storage unit. An interpolation unit (21) that interpolates based on the output of the focus detection pixels located around the image, and an image plane by the optical system based on the outputs of the plurality of focus detection pixels including the output of the interpolated defective pixel And a focus detection unit (21) for detecting a focus state of the optical system by detecting a shift amount of the optical system.

  [2] In the invention relating to the focus detection device, the imaging element (22) includes a plurality of first focus detection pixels (221a) that receive one of the pair of light beams divided into pupils, and A plurality of second focus detection pixels (222b) that receive the other light beam are arranged one-dimensionally, and the interpolation unit (21) is a focal point that receives the light beam from the same pupil as the defective pixel. Among the detection pixels, the output of the defective pixel is interpolated based on the output of the nearest effective pixel which is a pixel located closest to the defective pixel and which is not a defective pixel. Can be configured.

  [3] In the invention according to the focus detection apparatus, when there are two closest effective pixels, the interpolation unit (21) is based on an average value of outputs of the two closest effective pixels, The output of the defective pixel is interpolated, and when there is one closest effective pixel, the output of the defective pixel is interpolated based on the output of the one closest effective pixel. it can.

  [4] In the invention relating to the focus detection apparatus, the interpolation unit (21) interpolates the output of the defective pixel based on the output of the focus detection pixels (221a, 222b) positioned around the defective pixel. Thereafter, the correction of the non-uniformity of the focus detection pixel due to the dark current characteristic and the correction of the non-uniformity of the focus detection pixel due to the light receiving sensitivity characteristic can be performed.

  [5] In the invention relating to the focus detection apparatus, the focus detection unit (21) may focus the optical system at a predetermined focus detection position among a plurality of focus detection positions set in the image plane of the optical system. The state is detected based on the output of the focus detection pixels (222a, 222b) corresponding to the focus detection position, and the interpolation unit (21) detects that the focus detection position corresponding to the defective pixel is the defective pixel. The output of the defective pixel is configured to be interpolated based on the output of the focus detection pixel located around the defective pixel even when the focus detection position is different from the focus detection position corresponding to the focus detection pixel located around the defective pixel. be able to.

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

  According to the present invention, it is possible to appropriately detect the focus state of the optical system.

FIG. 1 is a block diagram showing a camera according to the present embodiment. FIG. 2 is a front view showing an imaging surface of the imaging device shown in FIG. FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the vicinity of 22a in FIG. FIG. 4 is an enlarged front view showing one of the imaging pixels 221. FIG. 5A is an enlarged front view showing one of the focus detection pixels 222a, and FIG. 5B is an enlarged front view showing one of the focus detection pixels 222b. FIG. 6 is an enlarged cross-sectional view showing one of the imaging pixels 221. FIG. 7A is an enlarged cross-sectional view showing one of the focus detection pixels 222a, and FIG. 7B is an enlarged cross-sectional view showing one of the focus detection pixels 222b. 8 is a cross-sectional view taken along line VIII-VIII in FIG. FIG. 9 is a flowchart illustrating an adjustment process for adjusting the output of a defective pixel. FIG. 10 is a flowchart showing the operation of the camera 1 according to this embodiment. FIG. 11 is a diagram for explaining a defective pixel interpolation method according to this embodiment. FIG. 12 is a diagram for explaining a defective pixel interpolation method according to this embodiment.

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

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

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

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

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

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

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

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

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

  The diaphragm 34 is configured such that the aperture diameter around the optical axis L1 can be adjusted in order to limit the amount of light flux that passes through the photographing optical system and reaches the image sensor 22 and to adjust the blur amount. The adjustment of the aperture diameter by the diaphragm 34 is performed, for example, by sending an appropriate aperture diameter calculated in the automatic exposure mode from the camera control unit 21 via the lens control unit 37. Further, the set aperture diameter is input from the camera control unit 21 to the lens control unit 37 by a manual operation by the operation unit 28 provided in the camera body 2. The aperture diameter of the aperture 34 is detected by an aperture sensor (not shown), and the lens controller 37 recognizes the current aperture diameter.

  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 camera memory 24 which is a recording medium. The camera memory 24 can be either a removable card type memory or a built-in memory. Details of the structure of the image sensor 22 will be described later.

  The camera body 2 is provided with an observation optical system for observing an image picked up by the image pickup device 22. The observation optical system of the present embodiment includes an electronic viewfinder (EVF) 26 composed of a liquid crystal display element, a liquid crystal driving circuit 25 that drives the electronic viewfinder (EVF) 26, and an eyepiece lens 27. The liquid crystal drive circuit 25 reads the captured image information captured by the image sensor 22 and sent to the camera control unit 21, and drives the electronic viewfinder 26 based on the read image information. Thereby, the user can observe the current captured image through the eyepiece lens 27. Note that, instead of or in addition to the observation optical system using the optical axis L2, a liquid crystal display may be provided on the back surface of the camera body 2, and a photographed image may be displayed on the liquid crystal display.

  A camera control unit 21 is provided in the camera body 2. The camera control unit 21 is electrically connected to the lens control unit 37 through an electric signal contact unit 41 provided in the mount unit 4, receives lens information from the lens control unit 37, and defocuses to the lens control unit 37. Send information such as volume and aperture diameter. The camera control unit 21 reads out the pixel output from the image sensor 22 as described above, generates image information by performing predetermined information processing on the read out pixel output as necessary, and generates the generated image information. Is output to the liquid crystal driving circuit 25 and the memory 24 of the electronic viewfinder 26. The camera control unit 21 controls the entire camera 1 such as correction of image information from the image sensor 22 and detection of a focus adjustment state and an aperture adjustment state of the lens barrel 3.

  In addition to the above, the camera control unit 21 detects the focus state of the photographic optical system by the phase detection method and the focus state of the photographic optical system by the contrast detection method based on the pixel data read from the image sensor 22. I do. A specific focus state detection method will be described later.

  The operation unit 28 is a shutter release button or an input switch for a 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 imaging element 22, and FIG. 3 is a front view schematically showing the arrangement of the focus detection pixels 222a and 222b by enlarging the vicinity of the focus detection pixel row 22a in FIG.

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

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

  FIG. 4 is an enlarged front view showing one of the imaging pixels 221, and FIG. 6 is a cross-sectional view. One imaging pixel 221 includes a micro lens 2211, a photoelectric conversion unit 2212, and a color filter (not shown), and a photoelectric conversion unit is formed on the surface of the semiconductor circuit substrate 2213 of the image sensor 22 as shown in the cross-sectional view of FIG. 2212 is built in and a microlens 2211 is formed on the surface. The photoelectric conversion unit 2212 is configured to receive an imaging light beam that passes through an exit pupil (for example, F1.0) of the photographing optical system 31 by the micro lens 2211 and receives the imaging light beam.

  In addition, on the imaging surface of the imaging element 22, focus detection pixel rows 22 a to 22 e in which focus detection pixels 222 a and 222 b are arranged instead of the above-described imaging pixel 221 are 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 to 22 e). In the present embodiment, the focus detection pixels 222a and 222b are densely arranged without providing a gap at the position of the green pixel G and the blue pixel B of the image pickup pixel 221 arranged in the Bayer array.

  Note that the positions of the focus detection pixel rows 22a to 22e shown in FIG. 2 are not limited to the illustrated positions, and may be any one, two, three, or four locations, and more than six locations. It can also be arranged at the position. FIG. 3 shows an example in which the focus detection pixel array is configured by 16 focus detection pixels 222a and 222b, but the number of focus detection pixels configuring the focus detection pixel array is limited to this example. Is not to be done.

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

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

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

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

  FIG. 8 is a cross-sectional view taken along the line VIII-VIII in FIG. 3. The focus detection pixels 222 a-1, 222 b-1, 222 a-2, and 222 b-2 that are arranged in the vicinity of the photographing optical axis L 1 and adjacent to each other are It shows that light beams AB1-1, AB2-1, AB1-2, and AB2-2 irradiated from the distance measuring pupils 341 and 342 of the exit pupil 34 are received, respectively. 8 illustrates only the focus detection pixels 222a and 222b that are located in the vicinity of the photographing optical axis L1, but other focus detection pixels other than the focus detection pixels illustrated in FIG. 8 are illustrated. In the same manner, the light beams emitted from the pair of distance measuring pupils 341 and 342 are respectively received.

  Here, the exit pupil 34 is an image set at a distance D in front of the microlenses 2221a and 2221b of the focus detection pixels 222a and 222b arranged on the planned focal plane of the photographing optical system. The distance D is a value uniquely determined according to the curvature and refractive index of the microlens, the distance between the microlens and the photoelectric conversion unit, and the distance D is referred to as a distance measurement pupil distance. The distance measurement pupils 341 and 342 are images of the photoelectric conversion units 2222a and 2222b respectively projected by the micro lenses 2221a and 2221b of the focus detection pixels 222a and 222b.

  In FIG. 8, the arrangement direction of the focus detection pixels 222a-1, 222b-1, 222a-2, 222b-2 coincides with the arrangement direction of the pair of distance measuring pupils 341, 342.

  As shown in FIG. 8, the microlenses 2221a-1, 2221b-1, 2221a-2, and 2221b-2 of the focus detection pixels 222a-1, 222b-1, 222a-2, and 222b-2 are photographic optical systems. Near the planned focal plane. The shapes of the photoelectric conversion units 2222a-1, 2222b-1, 2222a-2, 2222b-2 arranged behind the micro lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 are the same as the micro lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2. Projected onto the exit pupil 34 separated from the lenses 2221a-1, 2221b-1, 2221a-2, 2221b-2 by the distance measurement distance D, and the projection shape forms the distance measurement pupils 341, 342.

  In other words, on the exit pupil 34 at the distance measurement distance D, the microlens and the photoelectric conversion unit in each focus detection pixel so that the projection shapes (the distance measurement pupils 341 and 342) of the photoelectric conversion unit of each focus detection pixel match. Is determined, and the projection direction of the photoelectric conversion unit in each focus detection pixel is thereby determined.

  As shown in FIG. 8, the photoelectric conversion unit 2222a-1 of the focus detection pixel 222a-1 is formed on the microlens 2221a-1 by the light beam AB1-1 that passes through the distance measuring pupil 341 and goes to the microlens 2221a-1. A signal corresponding to the intensity of the image to be output is output. Similarly, the photoelectric conversion unit 2222a-2 of the focus detection pixel 222a-2 passes through the distance measuring pupil 341, and the intensity of the image formed on the microlens 2221a-2 by the light beam AB1-2 toward the microlens 2221a-2. The signal corresponding to is output.

  Further, the photoelectric conversion unit 2222b-1 of the focus detection pixel 222b-1 passes through the distance measuring pupil 342, and the intensity of the image formed on the microlens 2221b-1 by the light beam AB2-1 directed to the microlens 2221b-1. Output the corresponding signal. Similarly, the photoelectric conversion unit 2222b-2 of the focus detection pixel 222b-2 passes through the distance measuring pupil 342, and the intensity of the image formed on the microlens 2221b-2 by the light beam AB2-2 toward the microlens 2221b-2. The signal corresponding to is output.

  Then, a plurality of the above-described two types of focus detection pixels 222a and 222b are arranged in a 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 converted into the distance measurement pupil 341, respectively. 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.

  In the present embodiment, as shown in FIG. 2, a plurality of focus detection areas AFP (indicated by broken lines in FIG. 2) for detecting the focus state of the optical system are set in the imaging screen. The defocus amount is detected for each focus detection area AFP. Also, the camera control unit 21 performs the calculation of the image shift amount by the phase difference detection method and the calculation of the defocus amount based on the calculation.

  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 adjustment process for adjusting the output of the defective pixel will be described as a pre-process for interpolating the output of the defective pixel with reference to FIG. FIG. 9 is a flowchart showing an adjustment process for adjusting the output of the defective pixel. This adjustment process is a process for identifying a defective pixel and storing the address of the defective pixel, and is performed, for example, before factory shipment.

  First, in step S101, for example, the light emitted from the light source is diffused by a diffusion plate, tracing paper, or the like to generate a uniform luminance surface, and each focus detection of the image sensor 22 on the uniform luminance surface is detected by the camera control unit 21. An output for each of the pixels 222a and 222b is acquired as a light-time output.

  Next, in step S102, the light incident on the image sensor 22 is blocked, the surrounding environment is set to a dark state, and the camera control unit 21 outputs an output for each focus detection pixel 222a, 222b of the image sensor 22 in the dark state. Get as dark output.

  In step S103, the camera control unit 21 determines whether the focus detection pixels 222a and 222b are defective. Here, the defects of the focus detection pixels 222a and 222b are, for example, abnormalities in the linearity of the outputs of the focus detection pixels 222a and 222b according to the intensity of received light, and the focus detection pixels 222a and 222b on a uniform luminance surface. Output current abnormality (light output fluctuation abnormality), and dark current characteristics abnormality such as dark current flowing over a predetermined level in a dark state.

Specifically, the camera control unit 21 obtains the bright output Vout _{1 of} the focus detection pixels 222a and 222b acquired in step S101 and the dark output Vout _{2 of} the focus detection pixels 222a and 222b acquired in step S102, respectively. Then, it is determined whether or not the conditions shown in the following formula (1) and the following formula (2) are satisfied.
Vth ₁ ≦ Vout ₁ ≦ Vth ₂ (1)
Vout ₂ <Vth ₃ (2)
Here, in the above formula (1), Vth ₁ and Vth ₂ are reference values for determining that the outputs of the focus detection pixels 222a and 222b are normal at the time of light irradiation with light of a predetermined intensity. In the above formula (2), Vth ₃ is a reference value for determining that the outputs of the focus detection pixels 222a and 222b are normal in the dark when the light is shielded.

Then, the camera control unit 21 relates to the focus detection pixels 222a and 222b in which the light output Vout ₁ satisfies the condition shown in the above formula (1) and the dark output Vout ₂ satisfies the condition shown in the above formula (2). Detects that there is no defect, and on the other hand, focus detection where the light output Vout ₁ does not satisfy the condition shown in the above equation (1) or the dark output Vout ₂ does not satisfy the condition shown in the above equation (2). The pixels 222a and 222b are determined to be defective.

  In step S104, the address of the focus detection pixel (hereinafter, also referred to as a defective pixel) determined to be defective in step S103 by the camera control unit 21 is stored in a memory provided in the camera control unit 21. In the present embodiment, the light output and the dark output for each of the focus detection pixels 222 a and 222 are also stored in a memory provided in the camera control unit 21.

  Next, an operation example of the camera 1 according to the present embodiment will be described. FIG. 10 is a flowchart illustrating an operation example of the camera 1 according to the present embodiment. The following operation is started, for example, when the camera 1 is turned on.

  In step S201, the image sensor 22 receives the light flux from the optical system, and the camera control unit 21 receives the focus detection pixels 222a and 222b constituting the five focus detection pixel rows 22a to 22e of the image sensor 22. Reading of a pair of image data corresponding to the pair of images is started. Note that, when a specific focus detection area is selected by a manual operation of the photographer, only the outputs from the focus detection pixels 222a and 222b corresponding to the focus detection area may be read. The camera control unit 21 repeatedly reads out a pair of image data from the image sensor 22 at a predetermined interval.

  In step S202, the camera control unit 21 determines whether the shutter release button provided in the operation unit 28 is half-pressed (the first switch SW1 is turned on). If the shutter release button is half-pressed, the process proceeds to step S203. On the other hand, if the shutter release button is not half-pressed, step S202 is repeated until the shutter release button is half-pressed.

  In step S203, the camera control unit 21 reads the address of the defective pixel. In the present embodiment, the defective pixel address is stored in the memory included in the camera control unit 21 by the above-described defective pixel adjustment process (see FIG. 9), and the camera control unit 21 stores the memory of the camera control unit 21. By reading out the address of the defective pixel stored in the image sensor 22, the defective pixel which is a defective focus detection pixel out of the focus detection pixels 222 a and 222 b constituting the five focus detection pixel rows 22 a to 22 e of the image sensor 22. Can be specified.

  In step S204, the defect pattern of the defective pixel is determined by the camera control unit 21 based on the address of the defective pixel read in step S203. In step S205, the camera control unit 21 determines in step S204. The interpolation of the output of the defective pixel is performed by an interpolation method corresponding to the determined defect pattern.

  Here, FIGS. 11A to 11D are diagrams for explaining the defective pixel interpolation method according to the present embodiment, and defective pixels for each defective pattern (details will be described later) of the defective pixels. Shows an interpolation method. In FIG. 11, focus detection pixels that receive one of the pair of pupil-divided light beams are illustrated in white, and focus detection pixels that receive the other light beam are illustrated in gray.

  For example, in the example shown in FIG. 11A, one of the focus detection pixels is a defective pixel, and the focus detection pixel that receives a light beam from the same pupil as the defective pixel is located at the position closest to the defective pixel. In addition, the closest effective pixel that is a pixel that does not correspond to the defective pixel indicates a single pixel defect pattern that is a defect pattern located on both sides of the defective pixel. When the camera control unit 21 determines that the defect pattern is a single pixel defect pattern, the camera control unit 21 calculates the average value of the outputs of the two closest effective pixels located on both sides of the defective pixel as shown in FIG. The average interpolation is performed to interpolate the calculated average value as the output of the defective pixel.

  FIG. 11B shows a continuous pixel defect pattern in which two defective pixels are continuous in the arrangement direction. When the camera control unit 21 determines that the defect pattern is a continuous pixel defect pattern, as shown in FIG. 11B, the camera control unit 21 outputs the output of the closest effective pixel located closest to each defective pixel to the output of the defective pixel. Interpolate as For example, in the example shown in FIG. 11B, for a defective pixel located on the left side of consecutive defective pixels, the output of the nearest valid pixel located on the left side of the defective pixel is the output of the defective pixel. Interpolated (pre-interpolation). In addition, for a defective pixel located on the right side of consecutive defective pixels, the output of the nearest valid pixel located on the right side of the defective pixel is interpolated as the output of the defective pixel (post-interpolation).

  Further, in FIG. 11C, the defective pixel is located at the left end of the focus detection pixel rows 22a to 22e shown in FIG. 2, for example, and the nearest effective pixel for interpolating the defective pixel on the left side of the defective pixel. Indicates a left-end pixel defect pattern that does not exist. If the camera control unit 21 determines that the defect pattern is the left-end pixel defect pattern, for example, as shown in FIG. Perform post interpolation to interpolate as output.

  In addition, in FIG. 11D, the defective pixel is positioned at the right end of, for example, the focus detection pixel rows 22a to 22e shown in FIG. 2, and nearest neighbor effective for interpolating the defective pixel on the right side of the defective pixel. A right end pixel defect pattern in which no pixel exists is shown. When the camera control unit 21 determines that the defect pattern is the right-end pixel defect pattern, for example, as shown in FIG. 11D, the camera control unit 21 outputs the output of the nearest valid pixel located on the right side of the defective pixel, as shown in FIG. Performs pre-interpolation to interpolate as output.

  In the present embodiment, as shown in FIG. 2, a plurality of focus detection areas AFP are set, and each focus detection area is based on the outputs of focus detection pixels 222a and 222b located in each focus detection area AFP. The defocus amount for each AFP is calculated. Here, in FIG. 12, the defective pixel is located at the right end of the focus detection area AFP, the focus detection area AFP where the defective pixel exists, and the focus detection area where the closest effective pixel located right of the defective pixel exists. A scene different from AFP is illustrated. As described above, even when the focus detection area AFP in which the defective pixel exists and the focus detection area AFP in which the closest proximity effective pixel exists are different, the camera control unit 21 performs focus detection different from the focus detection area AFP in which the defective pixel exists. Based on the output of the closest effective pixel existing in the area AFP, the output of the defective pixel is interpolated. For example, in the example illustrated in FIG. 12, the camera control unit 21 determines that the defect pattern is the same as the single pixel defect pattern in the example illustrated in FIG. The average value of the output of the closest effective pixel present and the output of the closest effective pixel existing in a focus detection area different from the focus detection area where the defective pixel exists is interpolated as the output of the defective pixel.

  Next, in step S206, the camera control unit 21 performs a process of correcting nonuniformity (DSNU: Dark Signal Non-Uniformity) of the focus detection pixels 222a and 222b due to dark current characteristics. The non-uniformity correction of the focus detection pixels 222a and 222b due to the dark current characteristics can be performed by a known method. For example, the camera control unit 21 acquires each of the defect pixel adjustment processes shown in FIG. Based on the dark output of the focus detection pixels 222a and 222b, the output of all the focus detection pixels 222a and 222b including the output of the defective pixel interpolated in step S205 can be corrected.

  In step S207, the camera control unit 21 performs processing for correcting nonuniformity (PRNU: Photo Response Non-Uniformity) of the focus detection pixels 222a and 222b due to the light receiving sensitivity characteristic. The non-uniformity correction of the focus detection pixels 222a and 222b caused by the light receiving sensitivity characteristic can also be performed by a known method. For example, in this embodiment, the camera control unit 21 adjusts the defective pixel shown in FIG. Based on the bright-time outputs of the focus detection pixels 222a and 222b obtained in the process, the outputs of all the focus detection pixels 222a and 222b including the output of the defective pixel interpolated in step S205 can be corrected.

  In step S208, the camera control unit 21 performs a focus detection calculation. In the present embodiment, the camera control unit 21 interpolates in step S205 and outputs the defective pixels corrected in steps S206 and S207, and the focus detection pixels 222a and 222b other than the defective pixels corrected in steps S206 and S207. Based on the output, image shift detection calculation processing (correlation calculation processing) is executed for each focus detection area AFP shown in FIG. 2 to calculate the image shift amount, and further convert the image shift amount into a defocus amount.

  In step S209, the focus control of the focus lens 32 is performed by the camera control unit 21 based on the focus detection result in step S208. For example, when the defocus amount is calculated by the phase difference detection method, the lens drive amount necessary to drive the focus lens 32 to the in-focus position is calculated based on the calculated defocus amount. The calculated lens driving amount is sent to the focus lens driving motor 36 via the lens control unit 37. As a result, the focus lens driving motor 36 drives the focus lens 32 based on the calculated lens driving amount.

  In step S210, the camera control unit 21 determines whether or not the shutter release button provided in the operation unit 28 has been fully pressed (the second switch SW2 is turned on). When the second switch SW2 is turned on, the process proceeds to step S211 to shoot a subject image. On the other hand, when the second switch SW2 is not turned on, the focus lens 32 is fixed at the current lens position, and the process waits until the second switch SW2 is turned on.

  As described above, the camera 1 according to the present embodiment stores the address of a defective pixel having a defect among the plurality of focus detection pixels 222a and 222b, and is located at a position corresponding to the address of the defective pixel. Is interpolated based on the output of the nearest effective pixel located closest to the defective pixel among the focus detection pixels that receive the light beam from the same pupil as the defective pixel, and the output of the interpolated defective pixel is The focus state of the optical system is detected based on the outputs of the plurality of focus detection pixels 222a and 222b. In particular, in the present embodiment, the defect pattern of the defective pixel is determined, and the output of the defective pixel is interpolated by an interpolation method according to the defect pattern of the defective pixel. Thereby, in this embodiment, since the output of the focus detection pixels 222a and 222b having defects can be appropriately interpolated, the output of the plurality of focus detection pixels 222a and 222b including the output of the interpolated defective pixels is obtained. Based on this, it is possible to appropriately detect the focus state of the optical system.

  In this embodiment, in order to detect the focus state of the optical system, after performing an interpolation process (step S205) for interpolating the output of the defective pixel, the focus detection pixels 222a and 222b caused by dark current characteristics are not detected. By performing the correction of uniformity (step S206) and the correction of nonuniformity of the focus detection pixels 222a and 222b due to the light receiving sensitivity characteristic (step S207), the detection accuracy of the output of the defective pixel can be further improved. And the focus state of the optical system can be detected more appropriately.

  The embodiment described above is described for facilitating 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 in which focus detection is performed by the phase difference detection method is illustrated. However, the configuration is not limited to this configuration. For example, a configuration in which focus detection is performed by the contrast detection method may be used. The focus detection may be performed using the contrast detection method, and the focus detection may be performed using the contrast detection method when the focus state cannot be detected using the phase difference detection method. Alternatively, a configuration may be adopted in which focus detection is performed by the phase difference detection method, and focus detection by the phase difference detection method and focus detection by the contrast detection method are performed simultaneously when the focus state cannot be detected by the phase difference detection method.

  In the above-described embodiment, after performing the interpolation process (step S205) for interpolating the output of the defective pixel, correction of the non-uniformity of the focus detection pixels 222a and 222b due to the dark current characteristics (step S206), The configuration for correcting the non-uniformity of the focus detection pixels 222a and 222b (step S207) due to the light receiving sensitivity characteristic is illustrated, but the configuration is not limited to this configuration. For example, focus detection due to the dark current characteristic is performed. After performing correction of non-uniformity of the pixels 222a and 222b and correction of non-uniformity of the focus detection pixels 222a and 222b due to the light receiving sensitivity characteristic, an interpolation process for interpolating the output of the defective pixel may be performed. Good.

  In the above-described embodiment, the imaging element 22 includes the imaging pixel 221 and the focus detection pixels 222a and 222b, and the focus detection pixels 222a and 222b included in the imaging element 22 perform focus detection by the phase difference detection method. However, the present invention is not limited to this configuration, and a focus detection module for performing focus detection by the phase difference detection method may be provided independently of the image sensor 22.

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

Claims (6)

An imaging device comprising a plurality of imaging pixels and a plurality of focus detection pixels;
A storage unit storing addresses of defective pixels which are defective pixels among the plurality of focus detection pixels;
An interpolation unit that interpolates an output of the defective pixel located at a position corresponding to the address stored in the storage unit based on an output of a focus detection pixel located around the defective pixel;
A focus detection unit that detects a focus state of the optical system by detecting a shift amount of an image plane by the optical system based on outputs of a plurality of focus detection pixels including the output of the interpolated defective pixel; A focus detection apparatus comprising: The focus detection apparatus according to claim 1,
The imaging element includes a plurality of first focus detection pixels that receive one of the pair of pupil-divided light beams and a plurality of second focus detection pixels that receive the other light beam. Are arranged in an original form,
The interpolation unit is a closest pixel that is a pixel that is positioned closest to the defective pixel among focus detection pixels that receive a light beam from the same pupil as the defective pixel, and that is not a defective pixel. A focus detection apparatus that interpolates an output of the defective pixel based on an output of an effective pixel. The focus detection apparatus according to claim 2,
When there are two closest effective pixels, the interpolation unit interpolates the output of the defective pixel based on an average value of the outputs of the two closest effective pixels. In the case where there is one, the focus detection apparatus interpolates the output of the defective pixel based on the output of the one nearest effective pixel. In the focus detection apparatus according to any one of claims 1 to 3,
The interpolation unit corrects the non-uniformity of the focus detection pixel caused by dark current characteristics after interpolating the output of the defective pixel based on the output of the focus detection pixel located around the defective pixel. And a correction of non-uniformity of the focus detection pixels caused by the light receiving sensitivity characteristic. In the focus detection apparatus in any one of Claims 1-4,
The focus detection unit is configured to detect a focus state of the optical system at a predetermined focus detection position among a plurality of focus detection positions set in an image plane of the optical system, and the focus detection pixel corresponding to the focus detection position. Based on the output of
The interpolation unit outputs the output of the defective pixel even when the focus detection position corresponding to the defective pixel is different from the focus detection position corresponding to the focus detection pixel located around the defective pixel. A focus detection apparatus that performs interpolation based on an output of a focus detection pixel located around.   An imaging device provided with the focus detection apparatus in any one of Claims 1-5.

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