JP2013122494A - Focus detector and camera - Google Patents

Abstract

To appropriately increase the number of focus detection points.
A focus detection apparatus includes an image pickup and focus detection image pickup element 212 including a pixel row for focus detection, and is an output signal imaged by the image pickup element 212 through a photographing optical system 210 for focus detection. First focus detection means 108 that calculates phase difference information of a pair of images using a signal from the pixel array and detects a focus adjustment state by the photographing optical system based on the phase difference information, and first focus detection The first means is provided separately from the means 108 and detects a focus adjustment state by the photographing optical system based on phase difference information of a pair of images obtained by a pair of focus detection light beams that have passed through different regions of the photographing optical system. Two focus detection means 109, and the second focus detection means 109 acquires phase difference information based on a pair of focus detection light beams corresponding to a predetermined area in the imaging screen, and performs first focus detection. The means 108 is Located at a position corresponding to an area different from the predetermined area of the shadow in the screen, characterized by calculating the phase difference information by using the signals from the pixel rows for focus detection on the image sensor 212.
[Selection] Figure 4

Description

  The present invention relates to a focus detection apparatus and a camera.

  The position of a pair of images calculated using the signal from the focus detection pixel column among the output signals imaged by the imaging / focus detection image sensor having a plurality of focus detection pixels (pixel columns) through the photographing optical system. Separately from the first focus detection device for detecting the focus adjustment state by the photographing optical system based on the phase difference (so-called image shift) and the first focus detection device, a pair of passes through different regions of the photographing optical system There is known a camera including a second focus detection device that detects a focus adjustment state by the photographing optical system based on a phase difference between a pair of images obtained by a focus detection light beam (see Patent Document 1). .

JP 2007-233302 A

  When it is desired to perform focus detection at a larger number of positions in the shooting screen, simply increasing the focus detection position causes the following problems. That is, if a large number of focus detection points are provided in the shooting screen in the first focus detection device, interpolation processing for obtaining a shot image increases. On the other hand, if a large number of focus detection points are provided in the shooting screen in the second focus detection device, the size of the device is increased.

(1) A focus detection apparatus according to the present invention has an imaging and focus detection imaging element including a focus detection pixel array, and is an output signal captured by the imaging element through a photographing optical system, and the focus detection pixel. A first focus detection unit that calculates phase difference information of a pair of images using a signal from the column and detects a focus adjustment state by the photographing optical system based on the phase difference information; and a first focus detection unit; And a second focus that detects a focus adjustment state by the imaging optical system based on phase difference information of a pair of images obtained by a pair of focus detection light beams that have passed through different regions of the imaging optical system. And a second focus detection unit acquires phase difference information based on a pair of focus detection light beams corresponding to a predetermined area in the shooting screen, and the first focus detection unit It corresponds to the area different from the predetermined area in Present in position, and calculates the phase difference information by using the signals from the pixel rows for focus detection on the image pickup device.
(2) A camera according to a ninth aspect of the invention is a camera according to any one of the first to fifth aspects, an optical member that bends an incident light beam, and a light beam that has passed through a photographing optical system. An optical member moving mechanism for moving the optical member between a first position on the optical path and a second position outside the optical path, and the first optical focus detection unit detecting the focus adjustment state and the optical member in the first position when photographing. When the second focus detection means detects the focus adjustment state, the optical member is moved to the first position to detect the light beam as the second focus. A driving control unit that controls the optical member moving mechanism so as to lead to the unit, and a focusing optical system that focuses on the focus adjustment state detected by the first focus detection unit or the second focus detection unit. Focusing control means for emitting an optical system driving signal; Characterized in that it comprises a.
(3) A camera according to an eleventh aspect of the invention includes a focus detection apparatus according to any one of the first to fifth aspects, a semi-transmissive optical member that bends and transmits an incident light beam, and photographing. An optical member moving mechanism that moves the optical member between a first position on the optical path of the light beam that has passed through the optical system and a second position outside the optical path; and at least one of the first focus detection means and the second focus detection means When one detects the focus adjustment state, the optical member is moved to the first position to guide the light beam to both the first focus detection means and the second focus detection means, and at the time of photographing, the optical member is moved to the second position. Based on the drive control means for controlling the optical member moving mechanism so as to move the light beam only to the first focus detection means and the focus adjustment state detected by the first focus detection means or the second focus detection means. The shooting optical system. And focus control means for emitting optical system driving signal for, characterized in that it comprises a.

  ADVANTAGE OF THE INVENTION According to this invention, the focus detection point of the phase difference type focus detection apparatus can be increased appropriately.

It is a figure explaining the principal part structure of the single-lens reflex electronic camera carrying the focus detection apparatus by 1st embodiment of this invention. It is a figure explaining the principal part structure of the single-lens reflex electronic camera carrying the focus detection apparatus by 1st embodiment of this invention. It is a figure which illustrates the external appearance of an electronic camera. It is a block diagram explaining the structure of an electronic camera. It is a front view which shows the detailed structure of an image pick-up element. It is sectional drawing to which only the pixel for imaging was expanded. It is sectional drawing to which only the pixel for focus detection was expanded. It is a figure explaining the pupil division type phase difference detection method by image sensor AF. It is a figure which shows the ranging area at the time of performing focus detection using a dedicated AF element. It is a figure which shows the ranging area at the time of performing focus detection using an image sensor. It is the figure which overlapped the ranging area group by a dedicated AF element, and the ranging area group by an image sensor. It is a figure explaining the principal part structure of the single-lens reflex electronic camera carrying the focus detection apparatus by 2nd embodiment of this invention. It is a figure which shows the ranging area at the time of performing focus detection using a dedicated AF element. It is a figure which shows the ranging area at the time of performing focus detection using an image sensor. It is the figure which overlapped the ranging area group by a dedicated AF element, and the ranging area group by an image sensor. It is a figure which shows the ranging area at the time of performing focus detection using a dedicated AF element. It is a figure which shows the ranging area at the time of performing focus detection using an image sensor. It is the figure which overlapped the ranging area group by a dedicated AF element, and the ranging area group by an image sensor.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 and FIG. 2 are diagrams for explaining the main configuration of a single-lens reflex electronic camera equipped with a focus detection device according to a first embodiment of the present invention. 1 and 2, a photographic lens barrel 202 that is detachably attached to the camera body 201 is attached.

  Light from the subject enters the camera body 201 through the photographing optical system 210 and the diaphragm 211 of the photographing lens barrel 202. The subject light incident on the camera body 201 is bent toward the upper finder by a transflective quick return mirror (hereinafter referred to as a main mirror) 203 in the mirror-down state illustrated in FIG. An image is formed on 206. Part of the subject light transmitted through the main mirror 203 is reflected downward by the sub mirror 204 and is incident on a dedicated AF (autofocus) element 207 as a focus detection light beam. The dedicated AF element 207 is used in focus detection processing (known pupil division AF processing) for detecting the focus adjustment state by the photographing optical system 210.

  The subject light imaged on the diffusing screen 206 is further incident on the pentaprism 208. The pentaprism 208 guides incident subject light to the eyepiece optical system 209. The photographer observes the subject image through the viewfinder through the eyepiece optical system 209 from the viewfinder eyepiece window 41 (FIG. 3).

  After the release, the main mirror 203 is rotated to the mirror-up position illustrated in FIG. 2, and the subject light is guided to the image sensor 212 via the mechanical shutter 205 to form a subject image on the imaging surface. The image sensor 212 is configured by a CMOS image sensor or the like provided with a plurality of photoelectric conversion elements corresponding to pixels. The image sensor 212 captures a subject image formed on the imaging surface, and outputs a photoelectric conversion signal corresponding to the brightness of the subject image. An optical low-pass filter 213 is provided on the imaging surface side of the imaging element 212.

  The lens driving mechanism 214 drives the focus adjustment lens constituting the photographing optical system 210 to advance and retract in the optical axis direction. The drive direction and drive amount of the focus adjustment lens are instructed from the camera body 201 side. In order to simplify the drawing, the photographing optical system 210 is represented as a single lens.

  The mirror-down state in FIG. 1 is a shooting preparation state in which the photographer can observe the subject image via the eyepiece optical system 209. When focus detection is performed in this state, the electronic camera performs focus detection using a dedicated AF element 207 (referred to as dedicated element AF).

  In the mirror-up state of FIG. 2, all the subject light is guided to the image sensor 212 as in the case of shooting. When focus detection is performed in this state, the electronic camera performs focus detection based on an output signal from the image sensor 212 (referred to as image sensor AF).

  FIG. 3 is a diagram illustrating an appearance of the electronic camera. In FIG. 3, a main switch SW1, a release button SW2, and a monochrome liquid crystal monitor 31 are provided on the upper surface of the electronic camera. On the back of the electronic camera, a left selection switch SW6, a right selection switch SW7, an upper selection switch SW8, a lower selection switch SW9, a confirmation switch SW10, a command dial 45, a switching lever 51, and a color liquid crystal monitor 61 And a viewfinder eyepiece window 41.

  The electronic camera determines whether to perform the dedicated element AF or the image sensor AF according to the setting state of the switching lever 51. For example, when the switching lever 51 is switched to the left position, the dedicated element AF is performed when the mirror is down. The photographer performs framing while observing the subject image through the optical viewfinder.

  On the other hand, when the switching lever 51 is switched to the right position, the electronic camera performs the image sensor AF when the mirror is raised. The photographer performs framing while observing a live view image displayed on the color liquid crystal monitor 61 instead of the optical viewfinder.

  FIG. 4 is a block diagram illustrating the configuration of the electronic camera described above. The electronic camera is controlled by the microcomputer 101. The main switch SW1 outputs an operation signal for instructing power on / off of the electronic camera. The release switch (SW2) outputs a signal instructing to start photographing in conjunction with the pressing operation of the release button SW2.

  The cancel switch SW3 outputs an operation signal indicating operation cancellation. The mode switch SW4 outputs an operation signal for switching the operation mode of the electronic camera, that is, the photographing mode and the reproduction mode.

  The left selection switch SW6, right selection switch SW7, upper selection switch SW8, and lower selection switch SW9 each output an operation signal indicating the selection direction. The confirmation switch SW10 outputs an operation signal indicating operation confirmation. The switch SW13 and the switch SW14 output an operation signal according to the rotation operation of the command dial 45.

  The lens barrel 202 includes a CPU in the lens barrel, and communicates with the microcomputer 101. The CPU in the lens barrel drives and controls the lens driving mechanism 214 (FIGS. 1 and 2) in accordance with an instruction from the microcomputer 101, and moves the focus adjustment lens (210) forward and backward.

  The imaging processing circuit 107 performs predetermined image processing on the image data output from the imaging element 212. Image processing includes γ conversion processing and white balance adjustment processing.

  The image sensor AF circuit 108 performs an image shift detection calculation process (correlation process, phase difference detection process) based on an output signal from a predetermined pixel of the image sensor 212, so-called pupil division type phase difference detection method (micro lens). Method) to detect an image shift amount of a pair of images. Further, the deviation (defocus amount) of the current image plane with respect to the planned focal plane is calculated by multiplying the image shift amount by a predetermined conversion coefficient. Then, the movement direction and movement amount of the focus adjustment lens are calculated according to the defocus amount. Details of the image shift detection calculation process will be described later.

  The dedicated element AF circuit 109 performs image shift detection calculation processing (correlation processing and phase difference detection processing) based on an output signal from the dedicated AF element 207, thereby allowing a pair of focal points that have passed through different areas of the photographing optical system 210. An image shift amount between a pair of images obtained by the detection light beam is detected. Further, the deviation (defocus amount) of the current image plane with respect to the planned focal plane is calculated by multiplying the image shift amount by a predetermined conversion coefficient. Then, the movement direction and movement amount of the focus adjustment lens are calculated according to the defocus amount. Details of the image shift detection calculation process will be described later.

  The photometric device 102 receives subject light that has passed through the photographing optical system 210 and performs photometric calculation. The driver circuit 103 drives the mechanical shutter 205 in response to a command from the microcomputer 101. The driver circuit 104 drives the aperture mechanism 214 in response to a command from the microcomputer 101. When the diaphragm mechanism 214 moves a diaphragm drive lever (not shown), the aperture of the diaphragm 211 on the lens barrel 202 side changes. The driver circuit 105 drives the mirror mechanism 215 in response to a command from the microcomputer 101. The mirror mechanism 215 drives the main mirror 203 and the sub mirror 204 up or down.

  The external interface 113 is an interface circuit that outputs (transmits) data in the electronic camera to an external device such as a personal computer or another electronic camera, and inputs (receives) data from the external device. Examples of the external interface 113 include RS232C, USB, and IEEE1394.

  The display control unit 110 generates a drive signal for the color liquid crystal monitor 61 according to a command from the microcomputer 101. The color liquid crystal monitor 61 displays images and operation menus. The display control unit 111 generates a drive signal for the monochrome liquid crystal monitor 31 according to a command from the microcomputer 101. The monochrome liquid crystal monitor 31 displays shooting information such as the number of frames and shooting conditions.

  The memory card 119 is a recording medium that can be attached to and detached from the electronic camera via the card connector 117. Image data and audio data are recorded in the memory card 119. The driver circuit 106 drives and controls the ranging area irradiation device 115 in accordance with a command from the microcomputer 101. The distance measurement area irradiation device 115 illuminates the subject by emitting distance measurement auxiliary light when necessary during the dedicated element AF and the image sensor AF.

  The image storage memory 121 temporarily stores image data during the above-described image processing, compression processing and decompression processing described later. The compression / decompression circuit 123 compresses the image data by a predetermined method such as JPEG, or decompresses the compressed image data. The memory 125 is used as a work area for the microcomputer 101. The timer 127 measures the time designated by the microcomputer 101 and outputs a time-up signal. The battery 129 supplies power to each unit in the electronic camera.

<Image sensor AF processing>
An AF (automatic focus adjustment) process performed by the image sensor AF circuit 108 will be described in detail. The image sensor 212 of the present embodiment has focus detection pixels (referred to as focus detection pixels). The image sensor 212 is the same as the image sensor described in Japanese Patent Application Laid-Open No. 2007-279312. The image sensor AF circuit 108 performs focus detection processing by performing phase difference detection calculation using pixel output data from the focus detection pixels.

  FIG. 5 is a front view showing a detailed configuration of the image sensor 212. In the imaging element 212, imaging pixels 310 are two-dimensionally arranged. In addition, focus detection pixels 311 are arranged in a portion corresponding to a distance measurement area described later. In the example of FIG. 5, focus detection pixel rows are arranged in the horizontal direction substantially at the center of the imaging surface. FIG. 6 is an enlarged cross-sectional view of only the imaging pixels, and FIG. 7 is an enlarged cross-sectional view of only the focus detection pixels.

  In FIG. 6, the imaging pixel 310 includes a microlens 10 and an imaging photoelectric conversion unit 11. The microlens 10 is disposed in front of the photoelectric conversion unit 11 (on the left side in FIG. 6), and the photoelectric conversion unit 11 is formed on a semiconductor circuit substrate (not shown) in the image sensor 212.

  In FIG. 7, the focus detection pixel 311 includes a microlens 10 and a pair of photoelectric conversion units 12 and photoelectric conversion units 13 for focus detection. The photoelectric conversion units 12 and 13 are arranged symmetrically with respect to the center of the microlens 10. The microlens 10 is disposed in front of the photoelectric conversion units 12 and 13 (on the left side in FIG. 7), and the photoelectric conversion units 12 and 13 are formed on the same semiconductor circuit substrate as the photoelectric conversion unit 11 of the imaging pixel 310. The microlens 10 is disposed in the vicinity of the focal plane of the photographic optical system 210.

  FIG. 8 is a diagram for explaining a pupil division type phase difference detection method using the image sensor AF. A part of the focus detection pixel 311 (microlenses 50 and 60 and two pairs of photoelectric conversion units 52, 53, 62, and 63). ). The exit pupil 90 is an exit pupil that is projected at a distance d4 forward (left side in FIG. 8) from the microlenses 50 and 60 disposed at the focal plane position of the photographing optical system 210. The distance d4 is a distance determined according to the curvature and refractive index of the microlens 10 (50, 60), the distance between the microlens 10 (50, 60) and the photoelectric conversion units 12, 13, and the like. Called pupil distance.

  The optical axis 91 is the optical axis of the photographing optical system 210. The distance measurement pupil 92 is a distance measurement pupil corresponding to the microlenses 50 and 60 and the photoelectric conversion units 52 and 62, and the distance measurement pupil 93 is a distance measurement pupil corresponding to the microlenses 50 and 60 and the photoelectric conversion units 53 and 63. It is a pupil. The two pairs of focus detection subject light beams 72, 73, 82, 83 that have passed through the pair of distance measuring pupil regions 92, 93 pass through the microlenses 50, 60, respectively, and two pairs of photoelectric conversion units 52, 53, 62,. 63 is reached. In FIG. 8, a focus detection pixel 311 (microlens 50 and a pair of photoelectric conversion units 52 and 53) on the optical axis 91 and a focus detection pixel 311 (microlens 60 and a pair of photoelectric conversions) outside the optical axis 91 are shown. The conversion units 62 and 63) are schematically illustrated, but also in the other focus detection pixels 311, the focus detection light beams coming from the pair of distance measurement pupils to the micro lenses are received by the pair of photoelectric conversion units, respectively. To do. Note that the arrangement direction (horizontal direction in FIG. 5) of the focus detection pixels 311 is made to coincide with the division direction (vertical direction in FIG. 8) of the pair of distance measurement pupils.

  By having the above-described configuration, the focus detection pixels are each incident with a pupil-divided light beam as described in Japanese Patent Application Laid-Open No. 2007-279312. Specifically, the photoelectric conversion units 12 and 13 receive only light beams that have passed through one half of the microlens 10. For example, only the light flux (referred to as the A component) from the distance measuring pupil 92 enters the photoelectric conversion units 52 and 62. On the other hand, only the luminous flux (referred to as B component) from the distance measuring pupil 93 is incident on the photoelectric conversion units 53 and 63.

  As a result, the pixel output (A component data string) obtained from the photoelectric conversion units 52, 62,... Where the A component light beam is incident is an image of the light beam incident from the distance measuring pupil 92 of the photographing optical system 210. The pixel output (B component data string) obtained from the photoelectric conversion units 53, 63,... Into which the B component light beam is incident represents an image of the light beam incident from the distance measuring pupil 93.

  A pair of subject images composed of a subject image by the A component and a subject image by the B component approach each other in the so-called front pin state in which the photographing optical system 210 forms a sharp image of the subject before the planned focal plane, and conversely the planned focus. In a so-called rear pin state in which a sharp image of the subject is connected behind the surface, they move away from each other. The pair of images relatively coincide with each other in a focused state that connects a sharp image of the subject on the planned focal plane. Therefore, the focus adjustment state of the photographing optical system 210, that is, the defocus amount can be obtained by obtaining the relative positional deviation amount of the pair of images.

  The image sensor AF circuit 108 shifts the relative positional relationship between the A component data string and the B component data string, and an image shift amount (referred to as a shift amount) between the two data strings and the A component data string. And the B component data string are calculated. The calculation for obtaining the shift amount that minimizes the correlation value (the smaller the correlation value, the higher the correlation between the two data strings) is by a known phase difference detection calculation.

  The image sensor AF circuit 108 obtains the defocus amount by multiplying the shift amount that minimizes the correlation value by a predetermined coefficient. Note that the defocus amount differs for each distance measurement area. The defocus amount detection accuracy depends on the image shift amount detection pitch and the arrangement pitch of the microlenses 10. The image sensor AF circuit 108 calculates the moving direction and moving amount of the focus adjustment lens (210) based on the defocus amount.

<Dedicated element AF processing>
An AF (automatic focus adjustment) process performed by the dedicated element AF circuit 109 will be described. The dedicated AF element 207 of the present embodiment is the same as the image sensor described in Japanese Patent Application Laid-Open No. 2007-233302. The dedicated AF element 207 has an image sensor (CCD or CMOS sensor) dedicated to focus detection, unlike the image sensor 212 in which imaging pixels and focus detection pixels are mixed. The dedicated AF element 207 captures the subject image formed on the image sensor and outputs a photoelectric conversion signal corresponding to the brightness of the subject image to the dedicated element AF circuit 109.

  In the dedicated AF element 207, for example, a known aperture opening is provided so as to guide the light beam from the distance measuring pupil corresponding to the distance measuring pupil 92 to the A-row sensor array, and the measurement corresponding to the distance measuring pupil 93 is performed. A known aperture is provided to guide the light beam from the distance pupil to the B-row sensor row.

  As a result, images of a pair of defocus amount detection light beams incident through different areas of the photographing optical system 210 through the respective aperture openings are picked up at different positions on the focus detection-dedicated image sensor. Become.

  The dedicated element AF circuit 109 shifts the relative positional relationship between the output signal of the A component and the output signal of the B component, and shifts the image shift amount between the two output signals (referred to as a shift amount) and the output signal of the A component. And the B component output signal are calculated. The shift amount that minimizes the correlation value is obtained as in the case of the image sensor AF circuit 108.

  The dedicated element AF circuit 109 obtains the defocus amount by multiplying the shift amount that minimizes the correlation value by a predetermined coefficient. Similar to the case of the image sensor AF, the defocus amount differs for each distance measurement area, and the defocus amount detection accuracy depends on the detection pitch by the image sensor dedicated to focus detection. The dedicated element AF circuit 109 calculates the movement direction and movement amount of the focus adjustment lens (210) based on the defocus amount.

<Range of ranging area>
A ranging area (focus detection position) set on the focal plane of the photographing optical system 210 will be described with reference to FIGS. FIG. 9 is a diagram showing a distance measurement area (area where the image sensor included in the dedicated AF element 207 samples an image) when focus detection is performed using the dedicated AF element 207, and positions corresponding to the distance measurement area are shown. This is shown on the shooting screen 100.

  FIG. 9 shows a ranging area group 71 composed of 15 ranging areas. The dedicated element AF circuit 109 can calculate the defocus amount for each of the 15 distance measurement areas. The length, width, and sampling pitch of each ranging area are the size, arrangement length, and arrangement pitch of the photoelectric conversion units that constitute the image sensor, and a re-imaging lens (not shown) (the aperture opening in the dedicated AF element 207). It is determined by the projection magnification of the optical system that projects the light beam that has passed through onto the image sensor.

  FIG. 10 is a diagram illustrating a distance measurement area (a region in which the focus detection pixel 311 samples an image in the imaging surface) when focus detection is performed using the image sensor 212. In FIG. 10, distance measuring area groups 81 and 82 each consisting of 10 distance measuring areas are shown on the left and right sides of the center of the imaging surface. The image sensor AF circuit 108 can calculate the defocus amount for each of 10 + 10 = 20 distance measurement areas. The length / width and sampling pitch of each ranging area are determined by the size / arrangement length / arrangement pitch of the microlenses 10.

  FIG. 11 is a diagram in which the ranging area group 71 by the dedicated AF element 207 and the ranging area groups 81 and 82 by the imaging element 212 are overlapped. In the present embodiment, the distance measurement area group 71 by the dedicated AF element 207 is arranged closer to the center of the shooting screen, and the distance measurement area groups 81 and 82 by the image pickup element 212 are arranged away from the center of the shooting screen, thereby providing a distance measurement area. The group 71 and the distance measurement area groups 81 and 82 do not overlap.

  To bring the distance measuring area group 71 by the dedicated AF element 207 closer to the center of the shooting screen (closer to the optical axis of the shooting optical system 210), the dedicated AF element 207 and the sub mirror 204 that guides the subject luminous flux to the dedicated AF element 207 are arranged. This is suitable for downsizing. In addition, since the distance measuring area groups 81 and 82 are provided on the left and right sides of the center of the image pickup surface of the image pickup element 212, a defocus amount can be obtained at the periphery of the shooting screen, which is difficult to detect with the dedicated AF element 207.

According to the first embodiment described above, the following operational effects can be obtained.
(1) The focus detection apparatus of an electronic camera has an imaging and focus detection imaging element 212 including a pixel row for focus detection, and is an output signal captured by the imaging element 212 through the imaging optical system 210, and detects the focus. An image sensor AF circuit 108 that calculates phase difference information of a pair of images using a signal from a pixel row for detection, and detects a focus adjustment state by the imaging optical system 210 based on the phase difference information, and an image sensor AF circuit 108, and detects the focus adjustment state by the photographing optical system 210 based on phase difference information of a pair of images obtained by a pair of focus detection light beams that have passed through different regions of the photographing optical system 210. A dedicated element AF circuit 109. The dedicated element AF circuit 109 acquires phase difference information based on a pair of focus detection light beams corresponding to a predetermined area in the imaging screen, and the image sensor AF. Road 108, located at a position corresponding to an area different from the predetermined area within the photographing screen, and so calculates the phase difference information by using the signals from the pixel rows for focus detection on the image sensor 212. Thereby, the focus detection points of the phase difference type focus detection device can be appropriately increased. Further, it is advantageous for miniaturization as compared with the case where all the focus detection points are detected by the dedicated element AF circuit 109. On the other hand, the interpolation processing can be reduced as compared with the case where all the focus detection points are detected by the image sensor AF circuit 108. Here, the interpolation processing means that image information from the imaging pixel 310 cannot be obtained at the position of the focus detection pixel 311 on the image sensor 212, and therefore, the interpolation processing from the imaging pixels 310 around the focus detection pixel 311. This is an interpolation process for calculating image information at the pixel position using an output signal.

(2) The predetermined area, which is the detection target area of the dedicated element AF circuit 109, is an area that includes the approximate center of the shooting screen, so that the sub-mirror 204 and the peripheral area on the shooting screen are set as detection targets. This is advantageous for downsizing the dedicated AF element 207 and the like.

(3) The image sensor AF circuit 108 in the case of (2) calculates the phase difference information using the signal from the focus detection pixel column of the image sensor 212 corresponding to the outside of the predetermined area on the shooting screen. As a result, phase difference information can be obtained for the peripheral portion that the dedicated element AF circuit 109 does not detect. Specifically, since the distance measuring area groups 81 and 82 are provided on the left and right sides of the approximate center of the shooting screen, phase difference information can be obtained from the periphery of the shooting screen, which is difficult to detect with the dedicated element AF circuit 209. It becomes like this.

(4) Since the microcomputer 101 selects the imaging element AF circuit 108 or the dedicated element AF circuit 109 in accordance with the operation signal from the switching lever 51, the microcomputer 101 obtains phase difference information in an area intended by the user. Can do.

(Modification 1)
In the above description, the microcomputer 101 determines whether to perform the dedicated element AF or the imaging element AF according to the setting state of the switching lever 51. When the dedicated element AF is performed, focus detection is performed using at least one of the 15 ranging areas included in the ranging area group 71. When the image sensor AF is performed, focus detection is performed using at least one of the 20 ranging areas included in the ranging area groups 81 and 82. Instead of this, it may be configured to determine whether to perform the dedicated element AF or the image sensor AF in accordance with the designated ranging area.

  The microcomputer 101 according to the first modification includes, for example, a distance measurement area (15 locations) of the dedicated AF element 207 and an imaging element 212 by a transmission type liquid crystal display device (not shown) arranged on the diffusion screen 206. A distance measuring area (20 locations) is displayed. When the photographer looks into the viewfinder eyepiece window 41 in the mirror-down state (FIG. 1), he can check the positions of the 35 ranging areas in the same manner as in FIG.

  When the photographer operates the up / down / left / right switches SW6 to SW9, the microcomputer 101 sends an instruction to the display control unit 110 to select and highlight one distance measuring area corresponding to the input operation signal. The microcomputer 101 sets the highlighted distance measurement area as the distance measurement area selected by the photographer.

  When the selected distance measurement area is included in the distance measurement area group 71 by the dedicated AF element 207, the microcomputer 101 maintains the mirror-down state and causes the dedicated element AF circuit 109 to perform AF processing. On the other hand, when the selected distance measurement area is included in the distance measurement area group 81 or 82 by the image sensor 212, the image sensor AF circuit 108 performs AF processing after automatically mirroring up.

  According to the first modification, automatic switching between the dedicated element AF and the imaging element AF can be appropriately performed in accordance with the designated ranging area.

(Modification 2)
<Tracking operation during continuous shooting>
In continuous shooting where the shooting operation is repeated continuously, the focus adjustment target is tracked in conjunction with the movement of the subject (including movement in the optical axis direction and movement in the left / right / up / down directions), and AF processing is continuously performed. Well-known tracking control is performed. The microcomputer 101 for tracking control causes the dedicated element AF circuit 109 to perform AF processing when the mirror is down during continuous shooting, and causes the image sensor AF circuit 108 to perform AF processing when the mirror is up during continuous shooting.

  According to the second modification, the distance measurement information obtained by the dedicated AF element 207 is obtained in the mirror-down state during continuous shooting, and the distance measurement information obtained by the image sensor 212 is obtained in the mirror-up state during continuous shooting. By combining the two and performing tracking control, ranging information can be obtained without a break regardless of the mirror up / down state. Accordingly, it is possible to appropriately focus on the moving subject.

(Second embodiment)
FIG. 12 is a diagram for explaining a main configuration of a single-lens reflex electronic camera equipped with a focus detection apparatus according to the second embodiment of the present invention. The first embodiment includes a point having a dedicated AF element 207A, a point where the sub-mirror 204A is constituted by a semi-transmissive mirror, and a position of a focus detection pixel formed on the image sensor 212A (ie, a measurement by the image sensor 212A). (Distance area) is different.

  In FIG. 12, of the subject light incident on the camera body 201, the components transmitted through the semi-transmissive main mirror 203 and the sub mirror 204A that are in the mirror-down state before the release are guided to the image sensor 212A via the mechanical shutter 205. . Further, the component transmitted through the main mirror 203 and reflected by the sub mirror 204A is guided to the dedicated AF element 207A. Thereby, both the image sensor AF and the dedicated element AF can be performed in the mirror-down state.

<Range of ranging area>
The ranging area set in the second embodiment will be described with reference to FIGS. FIG. 13 is a diagram showing a distance measurement area (area in which the image sensor included in the dedicated AF element 207A samples an image) when focus detection is performed using the dedicated AF element 207A, and positions corresponding to the distance measurement area are shown. This is shown on the shooting screen 100A.

  In FIG. 13, a distance measuring area group 71A composed of 13 distance measuring areas is shown. The dedicated element AF circuit 109 can calculate the defocus amount for each of the 13 distance measuring areas.

  FIG. 14 is a diagram illustrating a distance measurement area (a region where the focus detection pixel 311 samples an image in the imaging surface) when focus detection is performed using the imaging device 212A. In FIG. 14, a distance measuring area group 81A composed of eight distance measuring areas is shown near the center of the imaging surface. The image sensor AF circuit 108 can calculate the defocus amount for each of the eight distance measuring areas.

  FIG. 15 is a diagram in which the ranging area group 71A by the dedicated AF element 207A and the ranging area group 81A by the imaging element 212A are overlapped. In the present embodiment, the distance measuring area group 71A by the dedicated AF element 207A and the distance measuring area group 81A by the image sensor 212A are close to the center of the shooting screen, and the distance measuring area groups 71A and 81A do not overlap. Arranged in density.

  Setting the distance measuring area group 81A by the image pickup element AF performed in the mirror-down state closer to the center of the shooting screen (closer to the optical axis of the shooting optical system 210) causes the main mirror 203 and the sub mirror to transmit the subject luminous flux to the image pickup element 212A. This is suitable for reducing the size of 204A.

  When the image sensor AF is performed in the mirror-down state, the light flux that has been semi-transmitted through the main mirror 203 and the sub mirror 104A is captured by the image sensor 212A. On the other hand, since actual photographing is performed in the mirror-up state, a light beam that does not pass through both mirrors is incident on the image sensor 212A. For this reason, a difference occurs in the optical path length to the image sensor 212A between distance measurement and shooting.

  In the present embodiment, in order to suppress the error due to the optical path difference, offset information is prepared based on the optical path difference calculated in advance using the thicknesses and refractive indexes of the mirrors 203 and 204A, and the imaging element AF circuit is prepared. When 108 calculates the defocus amount, correction is performed using the offset information.

  In the second embodiment, as in the first embodiment, whether to perform the dedicated element AF or the image sensor AF is determined according to the setting state of the switching lever 51. Further, as in the first modification, it may be determined whether to perform the dedicated element AF or the image sensor AF according to the designated distance measuring area.

According to the second embodiment described above, the following operational effects can be obtained.
(1) The image sensor AF circuit 108 of the focus detection apparatus calculates the phase difference information using a signal from the pixel row for focus detection of the image sensor 212 corresponding to the inside of the predetermined area on the shooting screen. The phase difference information is obtained further inside the region to be detected by the dedicated element AF circuit 109. Specifically, the distance measuring area group 71A by the dedicated AF element 207A and the distance measuring area group 81A by the image sensor 212A are close to the center of the shooting screen, and the distance measuring area groups 71A and 81A do not overlap. By arranging with density, phase difference information can be appropriately obtained at multiple points.

(2) The electronic camera bends and transmits the incident light beam, and transmits semi-transparent mirrors 203 and 204A, the first position (mirror down state) on the optical path of the light beam that has passed through the photographing optical system 210, and the outside of the optical path. At least one of the mirror mechanism 215 that moves the mirrors 203 and 204A between the second position (mirror-up state), the image sensor AF circuit 108, the image sensor 212, the dedicated element AF circuit 209, and the dedicated AF element 207 is focused. When the state is detected, the mirrors 203 and 204A are moved to the first position to guide the light beam to both the image sensor AF circuit 108, the image sensor 212, the dedicated element AF circuit 209, and the dedicated AF element 207. , 204A is moved to the second position so that the light flux is guided only to the image sensor AF circuit 108 and the image sensor 212. Based on the focus adjustment state detected by the microcomputer 101 that controls the mechanism 215, the image sensor AF circuit 108, the image sensor 212 or the dedicated element AF circuit 209, and the dedicated AF element 207, the photographing optical system 210 is focused. And a microcomputer 101 that emits an optical system drive signal for the purpose. Thereby, since both the imaging element AF and the dedicated element AF can be performed in the state where the mirrors 203 and 204A are in the first position, distance measurement can be performed at many detection points in the imaging standby state. In addition, the detection points can be arranged at a higher density than when the dedicated element AF circuit 209 and the dedicated AF element 207 are used for all the detection points.

(Modification 3)
Performing both the image sensor AF and the dedicated element AF in the shooting preparation state, that is, the mirror-down state is also suitable for so-called dynamic AF control. In the dynamic AF control, focus adjustment is performed based on the defocus amount calculated for the distance measurement area instructed by the photographer. This AF control method performs focus adjustment based on the defocus amount calculated for the new distance measurement area.

  In this case, when the imaging element AF circuit 108 or the dedicated element AF circuit 109 determines that the subject of interest has deviated from the distance measurement area, the microcomputer 101 moves around the original distance measurement area. The defocus amount is calculated for a plurality of other ranging areas that are positioned. In this case, the distance measurement area group 71A by the dedicated AF element 207A shown in FIG. 15 and the distance measurement area group 81A by the image sensor 212A are used, respectively, and based on the respective defocus amounts calculated for the plurality of distance measurement areas, A range-finding area in which the subject of interest is estimated to have moved is determined from the plurality of range-finding areas, and the control is switched to the range-finding control there.

  That is, when the AF area is determined by the dedicated AF element 207A, the AF process is performed by the dedicated element AF circuit 109. When the AF area is determined by the image sensor 212A, the AF process is performed by the image sensor AF circuit 108. . According to the third modification, dynamic AF control can be performed by combining the image sensor AF and the dedicated element AF, so that the moving subject can be properly focused.

(Modification 4)
You may increase the number of ranging areas used for the detection of the defocus amount at the time of mirror up. FIG. 16 to FIG. 18 are diagrams for explaining the distance measuring area in the fourth modification. FIG. 16 is a diagram showing a distance measurement area (area where the image sensor included in the dedicated AF element 207A samples an image) when focus detection is performed using the dedicated AF element 207A, and the position corresponding to the distance measurement area is shown. This is shown on the shooting screen 100A.

  In FIG. 16, a distance measuring area group 71A composed of 13 distance measuring areas is shown. The dedicated element AF circuit 109 can calculate the defocus amount for each of the 13 distance measuring areas.

  FIG. 17 is a diagram illustrating a distance measurement area (a region where the focus detection pixel 311 samples an image in the imaging surface) when focus detection is performed using the imaging device 212B. In FIG. 17, a distance measuring area group 81A composed of eight distance measuring areas is shown near the center of the imaging surface. In addition, distance measuring area groups 81 and 82 each including ten distance measuring areas are shown on the left and right sides of the distance measuring area group 81A. The image sensor AF circuit 108 can calculate the defocus amount for each of 8 + 10 + 10 = 28 distance measurement areas. The length / width and sampling pitch of each ranging area are determined by the size / arrangement length / arrangement pitch of the microlenses 10.

  FIG. 18 is a diagram in which the ranging area group 71A by the dedicated AF element 207A and the ranging area groups 81A, 81, and 82 by the imaging element 212B are overlapped. In the fourth modification, the distance measurement area group 71A by the dedicated AF element 207A and the distance measurement area groups 81A, 81, and 82 by the image sensor 212B are arranged at high density so as not to overlap.

  Setting the distance measuring area group 81A by the image pickup element AF performed in the mirror-down state closer to the center of the shooting screen (closer to the optical axis of the shooting optical system 210) causes the main mirror 203 and the sub mirror 204A to transmit the subject light flux to the image pickup element 212A. This is suitable for downsizing.

  On the other hand, distance measuring area groups 81 and 82 are provided on the left and right sides of the center of the imaging surface as the distance measuring area by the image sensor 212. Focus amount can be obtained. For this reason, it is possible to focus on a subject located around the photographing screen.

  The above description is merely an example, and is not limited to the configuration of the above embodiment.

DESCRIPTION OF SYMBOLS 51 ... Switching lever 101 ... Microcomputer 108 ... Imaging element AF circuit 109 ... Dedicated element AF circuit 201 ... Camera body 202 ... Lens barrel 203 ... Main mirror 204 ... Sub mirror 205 ... Mechanical shutter 207 ... Dedicated AF element 210 ... Shooting optical system 212 ... Image sensor

Claims (12)

A pair of images having an image pickup and focus detection image sensor including a focus detection pixel array, and output signals picked up by the image sensor through a photographing optical system and using signals from the focus detection pixel array First focus detection means for calculating the phase difference information of the first optical system and detecting a focus adjustment state by the photographing optical system based on the phase difference information;
Based on phase difference information of a pair of images obtained by a pair of focus detection light beams that are provided separately from the first focus detection unit and that have passed through different regions of the shooting optical system, Second focus detection means for detecting a focus adjustment state,
The second focus detection unit obtains phase difference information based on a pair of focus detection light beams corresponding to a predetermined region in the photographing screen;
The first focus detection unit uses the signal from the focus detection pixel array on the image sensor, which is present at a position corresponding to an area different from the predetermined area in the imaging screen, to detect the phase difference. A focus detection apparatus characterized by calculating information. The focus detection apparatus according to claim 1,
The focus detection apparatus according to claim 1, wherein the predetermined area which is a detection target area of the second focus detection unit is an area including a substantial center of the photographing screen. The focus detection apparatus according to claim 2,
The first focus detection unit calculates the phase difference information using a signal from the focus detection pixel column of the image sensor corresponding to the outside of the predetermined region on the photographing screen. Focus detection device. The focus detection apparatus according to claim 2,
The first focus detection means calculates the phase difference information using a signal from the focus detection pixel column of the image sensor corresponding to the inside of the predetermined area on the imaging screen. Focus detection device. The focus detection apparatus according to claim 2,
The first focus detection unit calculates the phase difference information using a signal from the focus detection pixel column of the imaging element corresponding to the inside and the outside of the predetermined area on the imaging screen. Focus detection device. In the focus detection apparatus according to any one of claims 1 to 5,
The focus detection apparatus further comprising selection means for selecting the first focus detection means or the second focus detection means in response to an operation signal from an operation member. The focus detection apparatus according to claim 6,
The operation member emits an operation signal for selectively switching the first focus detection means or the second focus detection means;
The focus detection apparatus, wherein the selection means selects a focus detection means indicated by the operation signal. The focus detection apparatus according to claim 6,
The second focus detection means has a plurality of second focus detection areas from which the phase difference information can be acquired on the shooting screen,
The first focus detection unit is a focus detection area in which the position of the focus detection pixel column of the image sensor is made to correspond to the shooting screen, and the first focus detection area can acquire the phase difference information. A plurality of
The operation member emits an operation signal for selectively switching one focus detection area among the plurality of first focus detection areas or the plurality of second focus detection areas,
The focus detection apparatus characterized in that the selection means selects a focus detection means corresponding to the selected focus detection area. The focus detection apparatus according to any one of claims 1 to 5,
An optical member that bends the incident light beam;
An optical member moving mechanism that moves the optical member between a first position on the optical path of a light beam that has passed through the photographing optical system and a second position outside the optical path;
When the first focus detection unit detects the focus adjustment state and during photographing, the optical member is moved out of the second position to guide the light beam to the first focus detection unit, and the second focus. Drive control means for controlling the optical member moving mechanism to move the optical member to the first position and to guide the light beam to the second focus detection means when the detection means detects the focus adjustment state;
Focusing control means for generating an optical system drive signal for focusing the photographing optical system based on a focus adjustment state detected by the first focus detection means or the second focus detection means;
A camera comprising: The camera according to claim 9,
The drive control means is configured to move the optical member alternately between the first position and the second position when performing continuous shooting in which the image sensor acquires continuous shot images.
The camera according to claim 1, wherein the focusing control unit controls the focusing of the photographing optical system based on a focus adjustment state detected alternately by the first focus detection unit and the second focus detection unit. The focus detection apparatus according to any one of claims 1 to 5,
A translucent optical member that bends and transmits the incident light beam; and
An optical member moving mechanism that moves the optical member between a first position on the optical path of a light beam that has passed through the photographing optical system and a second position outside the optical path;
When at least one of the first focus detection means and the second focus detection means detects a focus adjustment state, the optical member is moved to the first position, and the light beam is moved to the first focus detection means and The optical member moving mechanism is controlled such that the optical member is guided to both of the second focus detection means and the optical member is moved to the second position to guide the light beam only to the first focus detection means during photographing. Drive control means;
Focusing control means for generating an optical system drive signal for focusing the photographing optical system based on a focus adjustment state detected by the first focus detection means or the second focus detection means;
A camera comprising: The camera according to claim 11,
The drive control means moves the optical member to the first position when a focus detection mode for continuously tracking a subject in the shooting screen is selected,
The camera according to claim 1, wherein the focus control unit controls the focus of the photographing optical system based on a focus adjustment state obtained from both the first focus detection unit and the second focus detection unit.

Images