JP2018116296A - Focus detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform focus adjustment.SOLUTION: A camera system 1 includes: first focus detection means for detecting a focus adjustment state by using phase difference; second focus detection means for detecting the focus adjustment state on the basis of contrast; determination means for determining whether the focus adjustment state is detected by the first focus detection means or by the second focus detection means; and focus adjustment means for performing focus adjustment on the basis of detection result of the focus adjustment state by the focus detection means determined by the determination means. When the focus adjustment is continued after the focus adjustment is performed by the focus adjustment means to complete focusing, the first focus detection means is used.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a focus detection apparatus.

  Conventionally, when adjusting the focus of an optical system, in order to improve the focus adjustment accuracy, first, the focus state of the optical system is detected by the phase difference detection method, and the focus is determined based on the detection result by the phase difference detection method. The adjustment lens is driven to the vicinity of the in-focus position, and then the focus state of the optical system is detected in the vicinity of the in-focus position by the contrast detection method. Based on the detection result by the contrast detection method, the focus adjustment optical system A technique for driving the lens to the in-focus position is known (for example, Patent Document 1).

JP 2004-109690 A

  However, in Patent Document 1, focus detection is performed first by the phase difference detection method, and subsequently focus detection is performed by the contrast detection method. Therefore, there is a problem that it takes time to adjust the focus. there were.

A focus detection apparatus according to the present invention includes a first focus detection unit that detects a focus adjustment state using a phase difference, a second focus detection unit that detects a focus adjustment state based on contrast, and a first focus detection. Based on the result of detection of the focus adjustment state by the focus detection unit determined by the determination unit and the determination unit that determines whether the focus adjustment state is detected using either the first focus detection unit or the second focus detection unit, The first focus detection unit is used when a focus adjustment unit that performs focus adjustment is provided and the focus adjustment is continued after the focus adjustment is performed by the focus adjustment unit.
The focus detection apparatus according to the present invention also includes a first focus detection unit that detects a focus adjustment state using a phase difference, a second focus detection unit that detects a focus adjustment state based on contrast, and a first focus. Based on the detection result of the focus adjustment state by the determination unit that determines whether the focus adjustment state is detected using the detection unit or the second focus detection unit, and the focus detection unit determined by the determination unit A first focus detection unit and a second focus detection unit when the focus adjustment is performed after the focus adjustment is performed by the focus adjustment unit and after focusing. Is used.
The focus detection apparatus according to the present invention also includes a first focus detection unit that detects a focus adjustment state using a phase difference, a second focus detection unit that detects a focus adjustment state based on contrast, and a first focus. Based on the detection result of the focus adjustment state by the determination unit that determines whether the focus adjustment state is detected using the detection unit or the second focus detection unit, and the focus detection unit determined by the determination unit The second focus detection unit is used when the focus adjustment unit is provided with a focus adjustment unit that performs focus adjustment and the focus adjustment is continued after the focus adjustment is performed by the focus adjustment unit.

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

It is a block diagram which shows the structure of one embodiment of a camera system. It is a figure which shows the focus detection area in the imaging surface of an image pick-up element. It is a figure which shows typically the arrangement | sequence of a focus detection pixel. It is a front view of an imaging pixel. It is sectional drawing of an imaging pixel. It is a spectral characteristic figure which shows the relative sensitivity with respect to the wavelength of each of three imaging pixels RGB. It is a front view of a focus detection pixel. It is sectional drawing of a focus detection pixel. It is a spectral characteristic figure which shows the relative sensitivity with respect to the wavelength of a focus detection pixel. It is sectional drawing which follows the XI-XI line of FIG. It is a figure which shows a correlation calculation result. It is a flowchart figure which shows the flow of the process in 1st Embodiment. It is a figure which shows typically operation | movement when an in-focus position is found by contrast AF. It is a flowchart figure which shows the flow of the process in 2nd Embodiment. It is a figure which shows typically the continuous AF operation | movement in contrast AF. It is a flowchart figure which shows the flow of the process in 3rd Embodiment.

  FIG. 1 is a block diagram showing a configuration of an embodiment of a camera system in the present embodiment. The camera system 1 according to the present embodiment 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.

  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 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, when the rotating cylinder is rotated by the lens driving motor 36, the focus lens 32 fixed to the lens frame moves linearly along the optical axis L1.

  As described above, the focus lens 32 fixed to the lens frame by moving the rotating cylinder with respect to the lens barrel 3 moves straight in the direction of the optical axis L1, but the lens drive motor 36 as its drive source is operated by the lens mirror. The tube 3 is provided. The lens driving motor 36 and the rotating cylinder are connected by, for example, a transmission composed of a plurality of gears. When the driving shaft of the lens driving motor 36 is driven to rotate in any one direction, it is transmitted to the rotating cylinder at a predetermined gear ratio, and When the rotating cylinder rotates in any one direction, the focus lens 32 fixed to the lens frame moves straight in any direction of the optical axis L1. When the drive shaft of the lens drive motor 36 is driven to rotate 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 lens driving motor 36 calculates the focus lens calculated based on this information. The drive position 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, 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. Note that the 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 system 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 imaging optical system by the phase detection method (phase difference AF) and the imaging optical system by the contrast detection method based on the pixel data read from the image sensor 22. The focus state is detected (contrast AF). A specific focus state detection method will be described later.

  The operation unit 28 is a shutter release button or an input switch for the user to set various operation modes of the camera system 1, and switches between the auto focus mode / manual focus mode and the one shot mode / continuous mode even in the auto focus mode. It is possible to switch between the numeric modes. Here, the one-shot mode is a mode in which the position of the focus lens 32 once adjusted is fixed and photographing is performed at the focus lens position, whereas the continuous mode is a mode in which the position of the focus lens 32 is fixed. In this mode, the focus lens position is adjusted according to the subject. Various modes set by the operation unit 28 are sent to the camera control unit 21, and the operation of the entire camera system 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. FIG. 3 is an enlarged view of the vicinity of the focus detection area 22 a on the image sensor 22.

  As shown in FIG. 3, the imaging element 22 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 transmits a green wavelength region, and a red pixel. A red pixel R having a color filter that transmits a 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 the four adjacent pixel groups 223, 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 pickup device 22 is configured by repeatedly arranging the pixel group 223 on the image pickup surface of the image pickup device 22 in a two-dimensional manner with the pixel group arranged in the Bayer arrangement 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.

  4 is an enlarged front view showing one of the imaging pixels 221 and FIG. 5 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). As shown in the cross-sectional view of FIG. 5, a photoelectric conversion unit is formed on the surface of the semiconductor circuit substrate 2213 of the imaging element 22. 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.

  Note that the color filter of this embodiment is provided between the microlens 2211 and the photoelectric conversion unit 2212. The spectral sensitivities of the color filters of the green pixel G, the red pixel R, and the blue pixel B are shown, for example, in FIG. It is said to be as follows. FIG. 6 is a spectral characteristic diagram showing the relative sensitivity with respect to the wavelength of each of the three imaging pixels RGB shown in FIG.

  Returning to FIG. 2, focus detection areas 22 a to 22 c in which focus detection pixels 222 a and 222 b are arranged in place of the above-described imaging pixels 221 are arranged at the center of the imaging surface of the imaging element 22 and on the left and right sides thereof. As shown in FIG. 3, the focus detection pixel row in one focus detection area 22a is configured by a plurality of focus detection pixels 222a and 222b being alternately arranged adjacent to each other in a horizontal row. . 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 areas 22a to 22c illustrated in FIG. 2 are not limited to the illustrated positions, and may be disposed at any one, two, or four or more positions. In actual focus detection, the user can manually select the desired focus detection area as the focus detection position by manually operating the operation unit 28 from among the plurality of focus detection areas 22a to 22c. .

  FIG. 7A is an enlarged front view showing one of the focus detection pixels 222a, and FIG. 8A is a cross-sectional view of the focus detection pixel 222a. FIG. 7B is an enlarged front view showing one of the focus detection pixels 222b, and FIG. 8B is a cross-sectional view of the focus detection pixel 222b. As shown in FIG. 7A, 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. 7B. As shown in the cross-sectional view of FIG. A photoelectric conversion unit 2222b is formed on the surface of the circuit board 2213, and a microlens 2221b is formed on the surface. These focus detection pixels 222a and 222b are alternately arranged adjacent to each other in a horizontal row as shown in FIG. 3, thereby forming focus detection areas 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. FIG. 9 shows the spectral characteristics of the focus detection pixels 222a and 222b. The relative sensitivity is a spectral characteristic obtained by adding the sensitivities of the blue pixel B, the green pixel G, and the red pixel R of the imaging pixel 221 shown in FIG. The light wavelength region where the sensitivity appears is a region including the light wavelength regions of the sensitivity of the blue pixel B, the green pixel G, and the red pixel R of the imaging pixel 221 shown in FIG. However, it may be configured to include one of the same color filters as the imaging pixel 221, for example, a green filter. FIG. 9 is a spectral characteristic diagram showing the relative sensitivity with respect to the wavelengths of the focus detection pixels 222a and 222b shown in FIG.

  In addition, although the photoelectric conversion units 2222a and 2222b of the focus detection pixels 222a and 222b illustrated in FIGS. 7A and 7B have a semicircular shape, the shape of the photoelectric conversion units 2222a and 2222b is not limited thereto, and other For example, an elliptical shape, a rectangular shape, or a polygonal shape can 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. 10 is a cross-sectional view taken along the line XI-XI in FIG. 3. The focus detection pixels 222 a-1, 222 b-1, 222 a-2, and 222 b-2 arranged in the vicinity of the photographing optical axis L 1 are adjacent to each other. 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. In FIG. 10, only the focus detection pixels 222 a and 222 b that are located in the vicinity of the photographing optical axis L are illustrated, but other focus detection pixels other than the focus detection pixels illustrated in FIG. 10 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. 10, the arrangement direction of the focus detection pixels 222a-1, 222b-1, 222a-2, and 222b-2 coincides with the arrangement direction of the pair of distance measuring pupils 341 and 342.

  Further, as shown in FIG. 10, 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. 10, the photoelectric conversion unit 2222a-1 of the focus detection pixel 222a-1 is formed on the microlens 2221a-1 by a 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 an image formed on the microlens microlens 2221a-2 by the light beam AB1-2 toward the microlens 2221a-2. A signal corresponding to the intensity of the signal is output.

  In addition, the photoelectric conversion unit 2222b-1 of the focus detection pixel 222b-1 passes through the distance measuring pupil 342, and an image formed on the microlens microlens 2221b-1 by the light beam AB2-1 directed to the microlens 2221b-1. A signal corresponding to the intensity is output. 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 used as the distance measurement pupil 341, 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 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 at the detection position, that is, the defocus amount can be obtained.

  The calculation of the image shift amount by the phase difference detection method and the calculation of the defocus amount based thereon are executed by the camera control unit 21. Here, a method of calculating the defocus amount will be described. Each licensor is composed of a plurality of photoelectric conversion elements, and as shown in FIGS. 11A and 11B, a plurality of photoelectric conversion outputs a1, a2,... An, b1, b2,. bn is output. Then, correlation calculation is performed while each data string is relatively shifted by predetermined data L. The defocus amount is obtained by multiplying the shift amount that gives the minimum correlation amount among the correlation amounts C (L) thus obtained by a constant determined by the pitch width of the photoelectric conversion elements of the optical system and the image sensor array. . However, the correlation amount C (L) is a discrete value as shown in FIG. 11C, and the minimum unit of defocus amount that can be detected is limited by the pitch width of the photoelectric conversion element of the licensor. Therefore, by performing an interpolation calculation from the discrete correlation amount C (L), a new minimum value Cex is newly calculated, and precise focus detection is performed by a known three-point interpolation calculation.

  A specific example will be described with reference to FIG. FIG. 11A shows data in column A obtained by photoelectrically converting a periodic subject image using a licensor. FIG. 11B shows B-row data obtained by photoelectrically converting a periodic subject image using a licensor. Then, correlation calculation is performed while each data string is relatively shifted by predetermined data L. FIG. 11C is a diagram illustrating a result of calculating a correlation amount that is a minimum value among the correlation amounts C (L) thus obtained. As shown in FIG. 11C, the amount of correlation with the periodic subject also has periodicity, and a minimum value appears for each predetermined shift amount L. Even if the focus position of the main body is the minimum value 3, if the lens is driven to the false focus position of the minimum value 1 or the minimum value 2, a defocused image is obtained. Therefore, a range including a plurality of minimum values obtained from the correlation amount C (L) is set as the contrast AF search range, and the lens is driven with the position having the highest contrast evaluation value as the in-focus position.

  At this time, the search range of contrast AF is set wider than the extreme value range because the extreme value positions at both ends can be detected. Originally, contrast AF has a slower focusing speed than phase difference AF, but by limiting the search range, it is possible to minimize the focusing time after switching to contrast AF. Also, with phase difference AF, it is possible to detect the position with the highest contrast by contrast AF even for a subject that is falsely focused, so even a periodic subject can be accurately detected without being falsely focused. It is possible to focus. Further, by limiting the search range for contrast AF, it is possible to minimize the increase in focusing time.

  Or you may employ | adopt as a focus position the minimum value with the largest high frequency component contained in the phase difference AF data in several minimum value, without switching to contrast AF. In this case, the phase difference AF data is obtained by driving the lens to a position where the lens is not yet driven by only the phase difference AF without switching to the contrast AF, and the content degree of high frequency is calculated. The phase difference AF data at the position where the lens has already been driven does not need to be obtained again by driving the lens. In this way, the position with the largest high-frequency component from the plurality of extreme value phase difference AF data is set as the in-focus position. However, if the pixel pitch of the phase difference AF is coarser than the method described above, the detectable frequency band is limited to the low frequency side. When a high frequency component is obtained from phase difference AF data, it is desirable that the filter characteristic be such that electrical noise is removed even if a digital filter is applied, and that the high frequency component remains as much as possible.

-First embodiment-
FIG. 12 is a flowchart showing the flow of the focus adjustment process in the first embodiment. The process shown in FIG. 12 is executed as a program that starts when the camera system 1 is turned on. In the process shown in FIG. 12, it is assumed that the autofocus mode (AF mode) is set in advance to a continuous mode, for example, a continuous AF servo (continuous AF servo). The continuous AF servo is a lens driving method in which focusing is not performed after focusing on a subject and the focus is continuously adjusted according to the subject change.

  In step S100, generation of a through image by the camera control unit 21 and display of the through image by the electronic viewfinder 26 of the observation optical system are started. Specifically, an exposure operation is performed by the imaging element 22, and pixel data of the imaging pixel 221 is read by the camera control unit 21. Then, the camera control unit 21 generates a through image based on the read data, and the generated through image is sent to the liquid crystal drive circuit 25 and displayed on the electronic viewfinder 26 of the observation optical system. As a result, the user can view the moving image of the subject through the eyepiece lens 27. Note that the generation of the through image and the display of the through image are repeatedly executed at predetermined intervals.

  Thereafter, the process proceeds to step S101, where the camera control unit 21 sends a scan operation permission command to the lens control unit 37, and the scan operation is permitted. The scan operation will be described later. Thereafter, the process proceeds to step S105, where the camera control unit 21 starts calculation of the above-described phase difference AF and contrast AF, and then proceeds to step S106.

  In step S106, the camera control unit 21 determines whether the release button provided in the operation unit 28 has been half-pressed. If a positive determination is made in step S106, the process proceeds to step S110. On the other hand, if a negative determination is made in step S106, step S106 is repeated until an affirmative determination is made. That is, until the release button is half-pressed, generation and display of a through image and calculation of phase difference AF and contrast AF are repeatedly executed.

  In step S110, the camera control unit 21 determines whether or not the defocus amount has been calculated by the phase difference detection method. If the defocus amount can be calculated, it is determined that distance measurement is possible, and the process proceeds to step S136. On the other hand, if the defocus amount cannot be calculated, it is determined that distance measurement is impossible, and the process proceeds to step S111. In the present embodiment, even when the defocus amount can be calculated, even when the reliability of the calculated defocus amount is low, it is treated that the defocus amount cannot be calculated, and step S111 is performed. Let's go to. In the present embodiment, for example, when the subject has a low contrast, the subject is an ultra-low brightness subject, or the subject is an ultra-high brightness subject, it is determined that the reliability of the defocus amount is low. The

  In step S110, the above determination may be performed using the result of the most recent defocus amount calculation process. However, in the most recent defocus amount calculation process, the defocus amount is continuously obtained. If the defocus amount cannot be calculated, or if the reliability of the defocus amount is low continuously, it is determined that distance measurement is impossible, and the process proceeds to step S111. In this case, if the defocus amount is calculated even once, it may be determined that distance measurement is possible and the process proceeds to step S136.

  If it is determined in step S110 that the defocus amount has been calculated and it is determined that distance measurement is possible, the process proceeds to step S136. In step S136, the camera control unit 21 performs a scan operation prohibiting process. Specifically, the camera control unit 21 sends a scan operation prohibition command to the lens control unit 37, and the scan operation is prohibited. The scan operation will be described later.

  Thereafter, the process proceeds to step S200, and processing for driving the focus lens 32 to the in-focus position is performed based on the defocus amount calculated by the phase difference AF in step S105. Specifically, the camera control unit 21 calculates the lens drive amount necessary to drive the focus lens 32 to the in-focus position from the defocus amount calculated by the phase difference AF. The lens driving amount is sent to the lens driving motor 36 via the lens control unit 37. Then, the lens driving motor 36 drives the focus lens 32 to the in-focus position based on the lens driving amount calculated by the camera control unit 21. Then, the camera control unit 21 performs in-focus display when driving of the focus lens 32 to the in-focus position is completed. When performing the in-focus display, a display for notifying the user that the in-focus operation has been performed by the phase difference AF may be performed together.

  In the present embodiment, the camera control unit 21 repeatedly calculates the defocus amount by the phase difference detection method while the lens driving motor 36 is driven and the focus lens 32 is driven to the in-focus position. As a result, when a new defocus amount is calculated, the camera control unit 21 drives the focus lens 32 based on the new defocus amount. Then, it progresses to step S400 mentioned later.

  On the other hand, if it is determined in step S110 that the defocus amount cannot be calculated, or if it is determined that the reliability of the calculated defocus amount is low, the process proceeds to step S111, and the camera control unit 21 starts scanning operation. In the scanning operation of the present embodiment, while the focus lens 32 is scan-driven by the lens driving motor 36, the camera control unit 21 calculates the defocus amount and the focus evaluation value by a phase difference detection method. This is an operation of simultaneously performing the detection of the in-focus position by the phase difference detection method and the in-focus position detection by the contrast detection method at a predetermined interval.

  Specifically, the camera control unit 21 sends a scan drive start command to the lens control unit 37, and the lens control unit 37 drives the lens drive motor 36 based on the command from the camera control unit 21 to focus lens. 32 is driven to scan along the optical axis L1. Note that the scan driving of the focus lens 32 may be performed from the infinite end to the close end, or may be performed from the close end to the infinite end.

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

  In step S120, it is determined whether or not the defocus amount has been calculated by the phase difference detection method as a result of the scanning operation performed by the camera control unit 21. If the defocus amount can be calculated, it is determined that distance measurement is possible, and the process proceeds to step S136 described above. On the other hand, if the defocus amount cannot be calculated, it is determined that distance measurement is impossible, and the process proceeds to step S130. In step S120, similarly to step S110 described above, even when the defocus amount can be calculated, the defocus amount cannot be calculated if the reliability of the calculated defocus amount is low. It is assumed that the process proceeds to step S130.

  In step S130, the camera control unit 21 determines whether or not the in-focus position has been detected by the contrast detection method as a result of the scanning operation. If the in-focus position can be detected by the contrast detection method, the process proceeds to step S135. If the in-focus position cannot be detected, the process proceeds to step S140.

  In step S <b> 140, the camera control unit 21 determines whether or not the scan operation has been performed for the entire driveable range of the focus lens 32. If the scan operation is not performed for the entire driveable range of the focus lens 32, the process returns to step S120, and steps S120 to S140 are repeated to perform the scan operation, that is, while the focus lens 32 is scan-driven. The operation of simultaneously executing the calculation of the defocus amount by the phase difference detection method and the detection of the in-focus position by the contrast detection method at predetermined intervals is continuously performed. On the other hand, when the execution of the scan operation is completed for the entire driveable range of the focus lens 32, the process proceeds to step S141.

  As a result of executing the scanning operation, when it is determined in step S130 that the in-focus position has been detected by the contrast detection method, the process proceeds to step S135, and in steps S135 to S300, the detection is performed by the contrast detection method. A focusing operation based on the focusing position is performed.

  That is, first, in step S135, the camera control unit 21 performs a scanning operation stop process, and then proceeds to step S1137. In the same manner as in step S136 described above, the camera control unit 21 performs a scanning operation prohibition process. It is. Then, the process proceeds to step S300, and a focus drive process for driving the focus lens 32 to the focus position is performed based on the focus position detected by the contrast detection method. Then, it progresses to step S400 mentioned later.

  Here, FIG. 13 is a diagram showing the relationship between the focus lens position and the focus evaluation value and the relationship between the focus lens position and time when the in-focus position is detected by the contrast detection method as a result of the scanning operation. Show. As shown in FIG. 13, at the start of the scanning operation, the focus lens 32 is positioned at P0 shown in FIG. 13, and the focus evaluation is performed while driving the focus lens 32 from P0 from the infinity side to the close side. Get the value. When the focus lens 32 is moved to the position P1 shown in FIG. 13 and the peak position (focus position) of the focus evaluation value is detected (step S130 = Yes), the scanning operation is stopped ( After step S135) and the scanning operation prohibition process (step S137) are performed, focus drive (step S300) for driving the focus lens 32 to the focus position (position P2 in FIG. 13) is performed. . With such an operation, even if there is a backlash in the lens, the lens driving direction at the time of evaluation value acquisition and the lens driving direction at the time of focusing operation can be aligned, so the lens can be stopped accurately. Become.

  In this embodiment, when it is determined in step S130 that the in-focus position has been detected by the contrast detection method, the focus lens 32 is driven to the in-focus position based on the detection result by the contrast detection method. In other words, until the drive of the focus lens 32 to the in-focus position is completed, the drive of the focus lens 32 based on the focus detection result by the phase difference detection method is prohibited. That is, after it is determined that the in-focus position can be detected by the contrast detection method, the focus lens 32 is driven based on the result of the phase difference detection method even when the defocus amount can be calculated by the phase difference detection method. Is prohibited. Thereby, the hunting phenomenon of the focus lens 32 can be suppressed.

  Then, the camera control unit 21 performs in-focus display when driving of the focus lens 32 to the in-focus position is completed. When performing in-focus display, a display for notifying the user that the in-focus operation has been performed by contrast AF may be performed together.

  In the scan operation of the present embodiment, the above-described steps S120 to S140 are repeatedly executed, so that the focus lens 32 is driven to scan, the defocus amount is calculated by the phase difference detection method, and the contrast detection method is used. The detection of the focal position is simultaneously performed at a predetermined interval. Then, as a result of repeatedly executing steps S120 to S140 described above, the focus detection result by the detection method in which the defocus amount is calculated or the in-focus position can be detected first among the phase difference detection method and the contrast detection method. The focus lens 32 is used to drive to the in-focus position. Further, as described above, in the scanning operation of the present embodiment, after determining whether or not the defocus amount can be calculated by the phase difference detection method (step S120), the in-focus position can be detected by the contrast detection method. If the phase difference detection method and the contrast detection method can calculate the defocus amount and detect the in-focus position at the same time by determining whether or not the focus position has been detected, the focus by the phase difference detection method is determined. The detection result is adopted in preference to the focus detection result by the contrast detection method.

  On the other hand, if it is determined in step S140 that the scan operation has been completed for the entire driveable range of the focus lens 32, the process proceeds to step S141. In step S141, as a result of performing the scanning operation, focus detection could not be performed by any of the phase difference detection method and the contrast detection method, and therefore the scanning operation end processing is performed. Thereafter, the process proceeds to step S142, and the scan control prohibiting process is performed by the camera control unit 21 in the same manner as in steps S136 and S137 described above. Thereafter, the process proceeds to step S400.

  In step S400, after stopping the function of contrast AF, the camera control unit 21 performs lens driving using only the phase difference AF in step S410. As a result, once focused by phase difference AF or contrast AF, the subject is kept in focus using only phase difference AF.

  Thereafter, the process proceeds to step S500, and the camera control unit 21 determines whether or not the half-press of the release button provided in the operation unit 28 is continued. If an affirmative determination is made in step S500, the process returns to step S410 to continue the phase difference AF. On the other hand, if a negative determination is made in step S500, the process returns to step S106.

According to the first embodiment described above, the following effects can be obtained.
(1) When it is difficult to detect the focus state of the photographic optical system by the phase difference detection method (for example, when photographing subjects of different colors with the same reflectance), or the focus state of the photographic optical system by the contrast detection method In any case where it is difficult to detect (for example, when photographing a subject with low brightness), the focus adjustment of the photographing optical system can be appropriately performed.

(2) Since the calculation of the defocus amount by the phase difference detection method and the detection of the in-focus position by the contrast detection method are performed simultaneously, and the focus of the photographic optical system is adjusted by the method in which the focus is detected first, The focus adjustment of the optical system can be performed in a short time.

(3) When the subject is kept in focus even after focusing, as in continuous AF, the function of the contrast AF is stopped, and then the lens is driven only by the phase difference AF. As a result, it is not necessary to perform the process for contrast AF once the focus is achieved by the phase difference AF or the contrast AF, so that the processing load can be reduced. In addition, battery consumption can be reduced.

-Second embodiment-
FIG. 14 is a flowchart showing a flow of focus adjustment processing in the second embodiment. In FIG. 14, the same processes as those shown in FIG. 12 in the first embodiment are denoted by the same step numbers and the description thereof is omitted. Hereinafter, the processes in the first embodiment are described. The difference will be mainly described. Also in FIG. 14, it is assumed that the AF mode is set to the continuous AF servo (continuous AF servo) in advance as in the process shown in FIG.

  In step S411, the camera control unit 21 determines whether or not the distance can be measured by the phase difference AF in step S110 or S120. If an affirmative determination is made in step S411, the process proceeds to step S412 to drive the lens with only the phase difference AF. On the other hand, if a negative determination is made in step S411, the process proceeds to step S413, and the lens is driven only with contrast AF. As a result, once focusing is performed by phase difference AF or contrast AF, focus adjustment is performed using the method of distance measurement, and the subject is kept in focus.

  Note that, as described above, since continuous AF is assumed to continue to focus on the subject once focused on the subject, an operation to continue focusing on the subject is also required in contrast AF. . Therefore, in this embodiment, the focus lens 32 is moved slightly back and forth (wobbling), and the in-focus position is specified while comparing the magnitude relationship of the evaluation value output. Specifically, as a result of the comparison of the evaluation value output, it is assumed that the in-focus position is in the direction where the evaluation value is large, and the lens position is slightly moved in that direction. Again, wobbling is performed with reference to the position, and the lens is driven in a small amount in the direction in which the evaluation value is large. By continuously performing this operation, the subject can follow the focus position.

  FIG. 15 is a diagram schematically showing a specific example of contrast AF by wobbling. FIG. 15 shows an example in which three sets of wobbling are performed in one set. This is because the average value of the evaluation values is calculated by performing wobbling three times in order to suppress the variation of the evaluation values, and the magnitude comparison is performed using the calculated average value. Note that the lens moving direction may be determined based on the evaluation value calculated by performing one wobbling without calculating the average value of the evaluation values by performing wobbling a plurality of times as described above. Further, FIG. 15 shows an example of performing two-point wobbling in which the lens is slightly driven between two points. However, a three-point wobbling in which the lens is minutely driven between three points is used, and a focusing position exists inside the three points. You may make it determine whether to do. When the in-focus position is found as three-point wobbling, the lens is driven to the in-focus position, and next time, three-point wobbling may be performed with reference to the in-focus position.

According to the second embodiment described above, the following effects can be obtained.
In the case where the subject is kept in focus even after focusing, as in continuous AF, the method of measuring the distance between phase difference AF and contrast AF is adopted. As a result, it is possible to adopt an optimum method according to the shooting environment, out of the phase difference AF and the contrast AF.

-Third embodiment-
FIG. 16 is a flowchart showing the flow of the focus adjustment process in the third embodiment. In FIG. 16, the same processes as those shown in FIG. 12 in the first embodiment are denoted by the same step numbers and the description thereof is omitted. Hereinafter, the processes in the first embodiment are described. The difference will be mainly described. Also in FIG. 16, it is assumed that the AF mode is set to the continuous AF servo (continuous AF servo) in advance as in the process shown in FIG.

  In step S400, the camera control unit 21 stops the phase difference AF function, and then proceeds to step S414. In step S414, the camera control unit 21 drives the lens with only the contrast AF using the method shown in FIG. As a result, once focusing is performed by phase difference AF or contrast AF, the subject is continuously focused using only contrast AF.

According to the third embodiment described above, the following effects can be obtained.
When the subject is kept in focus even after focusing, as in continuous AF, the phase difference AF function is stopped, and then the lens is driven only with contrast AF. As a result, once the phase difference AF or the contrast AF is in focus, it is not necessary to perform the process for the phase difference AF, so that the processing load can be reduced. In addition, battery consumption can be reduced.

-Modification-
Note that the present invention is not limited to the configurations in the above-described embodiments as long as the characteristic functions of the present invention are not impaired. Moreover, it is good also as a structure which combined the above-mentioned embodiment and a some modification.

DESCRIPTION OF SYMBOLS 1 Camera system, 2 Camera body, 21 Camera control part, 22 Image sensor, 23 Shutter, 24 Memory, 25 Liquid crystal drive circuit, 26 Electronic viewfinder, 27 Eyepiece lens, 28 Operation part, 3 Lens barrel, 31 Shooting optical system , 32 Focus lens, 35 Encoder, 36 Lens drive motor, 37 Lens control part, 4 Mount part, 41 Electrical signal contact part

The focus detection apparatus according to the present invention captures an image of a subject formed by an optical system having a focus adjustment optical system and outputs a signal, and the imaging based on a pair of light beams passing through the optical system A first detection unit that detects a focus position of the focus adjustment optical system that focuses the image of the subject on the imaging unit using a phase difference between a pair of signals output from the unit; and an output from the imaging unit A second detection unit that detects the in-focus position of the focus adjustment optical system using the contrast of an image generated from the generated signal, and the first detection unit detected by the first detection unit or the second detection unit. A controller that detects the in-focus position by the first detector without detecting the in-focus position by the second detector after the focus adjustment optical system has been moved to the in-focus position. .

Claims (3)

A first focus detection unit that detects a focus adjustment state using a phase difference;
A second focus detection unit for detecting a focus adjustment state based on contrast;
A determination unit that determines which of the first focus detection unit and the second focus detection unit is used to detect a focus adjustment state;
A focus adjustment unit that performs focus adjustment based on the detection result of the focus adjustment state by the focus detection unit determined by the determination unit;
A focus detection apparatus using the first focus detection unit when the focus adjustment is continued after the focus adjustment is performed by the focus adjustment unit. A first focus detection unit that detects a focus adjustment state using a phase difference;
A second focus detection unit for detecting a focus adjustment state based on contrast;
A determination unit that determines which of the first focus detection unit and the second focus detection unit is used to detect a focus adjustment state;
A focus adjustment unit that performs focus adjustment based on the detection result of the focus adjustment state by the focus detection unit determined by the determination unit;
A focus detection apparatus using the first focus detection unit and the second focus detection unit when the focus adjustment is continued after the focus adjustment is performed by the focus adjustment unit. A first focus detection unit that detects a focus adjustment state using a phase difference;
A second focus detection unit for detecting a focus adjustment state based on contrast;
A determination unit that determines which of the first focus detection unit and the second focus detection unit is used to detect a focus adjustment state;
A focus adjustment unit that performs focus adjustment based on the detection result of the focus adjustment state by the focus detection unit determined by the determination unit;
A focus detection apparatus using the second focus detection unit when the focus adjustment is continued after the focus adjustment is performed by the focus adjustment unit.

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