JP2008090020A - Focus detection device, camera and illuminating light radiating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus detection device where two or more kinds of focus detection means detecting the focus adjustment state of an image-formation optical system by different systems can operate similarly by any system even when they are used by radiating auxiliary light. <P>SOLUTION: The focus detection device includes: the two or more kinds of focus detection means 72, 21, 22, 31 and 32 detecting the focus adjustment state of the image-formation optical system 71 by the different systems; an illumination means 78 capable of radiating illuminating light including at least a pattern image; and a control part 60 changing the illuminating light radiated by the illumination means in accordance with the kind of the focus detection means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a focus detection device that performs focus detection by irradiating a subject with auxiliary light when the contrast of the subject is low or dark, a camera equipped with the focus detection device, and illumination light irradiation that irradiates the subject with illumination light Relates to the device.

As an automatic focus detection (autofocus, hereinafter abbreviated as AF) method, for example, a relative displacement position of a pair of image signals by a pair of light fluxes from a subject that has passed through different exit pupil regions of a photographing lens is obtained, thereby detecting the object defocusing. The focus amount is detected, AF based on the phase difference method for driving the photographic lens based on the defocus amount, and a focus evaluation value based on the contrast of the subject image by the photographic lens are obtained, and the focus is adjusted while moving the photographic lens in the optical axis direction. A so-called hybrid AF camera that uses a contrast AF for finding a position (focus position) where the evaluation value is highest is known. (Patent Document 1)
JP 2002-328293 A

  In a conventional hybrid AF camera, when focus detection is performed by illuminating illumination light (auxiliary light) when the subject is dark or the like, focus detection is possible with one AF, but the other In AF, there is a problem that focus detection becomes impossible, and there is a problem that the merit of hybrid AF combining phase difference type AF and contrast type AF cannot be used.

  The present invention makes it possible to operate in the same manner regardless of whether a plurality of types of focus detection means for detecting the focus adjustment state of the imaging optical system by different methods are used by irradiating illumination light. An object is to provide a focus detection device, a camera, and an illumination light irradiation device.

  The focus detection apparatus according to claim 1 of the present invention that achieves the above object irradiates a plurality of types of focus detection means for detecting the focus adjustment state of the imaging optical system by different methods and illumination light including at least a pattern image. And a control unit that changes the illumination light emitted by the illumination unit according to the type of the focus detection unit.

  Examples of the focus detection means include a phase difference method and a contrast method. As the illumination unit, for example, there is one that irradiates a pattern forming unit with illumination light and projects a pattern image onto a subject by a projection optical system.

  In a focus detection apparatus according to a second aspect of the present invention, the illumination unit includes a plurality of optical systems independent of each other, and each of the optical systems includes a light source that emits the illumination light and illumination light from the light source. A pattern forming unit that forms the pattern image, and a projection optical system that projects the pattern image of the pattern forming unit toward a subject.

  According to a third aspect of the present invention, the focus detection apparatus detects the focus adjustment state based on a signal obtained by each of the plurality of types of focus detection means receiving an image light beam from the imaging optical system. The signal reading directions are different from each other.

  According to a fourth aspect of the present invention, in the focus detection apparatus, the focus detection unit obtains the focus adjustment state based on a pair of images of the light beams that have passed through different pupil regions of the imaging optical system. And a contrast-type focus detection means for obtaining the focus adjustment state based on an image formed by the imaging optical system, and the pattern image has a striped light-dark image extending in the first direction. Including a second pattern having a first pattern and a striped bright-dark image extending in a second direction orthogonal to the first direction, and the control unit controls the illuminating unit to detect the phase difference type focus detecting unit When using either of the contrast type focus detection means, the illumination light including the first pattern is irradiated, and when using the other, the illumination light including the second pattern is irradiated. Features .

  In the focus detection apparatus according to a fifth aspect of the present invention, the first pattern is formed with the interval between the bright and dark images different from each other, and the second pattern sets the interval between the bright and dark images. The phase difference type focus detection means detects the first pattern, and the contrast type focus detection means detects the second pattern. Features.

  A camera according to a sixth aspect of the present invention includes the focus detection device according to any one of the first to fifth aspects.

  The illumination light irradiation apparatus according to claim 7 of the present invention is an illumination unit that can irradiate a plurality of types of illumination light including at least a pattern image, and illumination light that is emitted by the illumination unit according to the type of the focus detection unit. And a control unit for changing.

  According to the present invention, even when a plurality of types of focus detection means for detecting the focus adjustment state of the imaging optical system by different methods are used using illumination light, the same operation is performed in any focus detection method. Can be possible.

  An embodiment of a focus detection apparatus of the present invention, a camera including the focus detection apparatus, and an illumination light irradiation apparatus used for the focus detection apparatus will be described below with reference to FIGS.

  FIG. 1 is a schematic external view of a camera provided with a focus detection apparatus according to an embodiment of the present invention. An illumination light irradiation device 79 including a flash light emitting unit 77 and an auxiliary light projection unit 78 is provided on the upper body of the camera 70.

  FIG. 2 is a block diagram of a camera equipped with a focus detection apparatus according to an embodiment of the present invention.

  The subject luminous flux incident through the photographing optical system 71 is reflected upward by the quick return mirror 73 disposed obliquely on the optical axis, and photographed as shown in FIGS. The screen IF is configured to be observable, and a part of the light beam enters the photometric device 80. The photometric device 80 detects the luminance of the subject based on the received subject luminous flux.

  Further, part of the subject luminous flux passes through the quick return mirror 73 and is incident on a pair of line sensors 21 (to be described later) through a focus detection optical system 72 positioned at the bottom of the camera body by the sub mirror 74.

  On the other hand, when the quick return mirror 73 is rotated to a position retracted from the optical axis (position indicated by a two-dot chain line in the figure) by operating a release button (not shown) of the camera or the like, the subject luminous flux is a CCD or CMOS. An image of the subject is formed on the image sensor 31.

  The focus detection apparatus 10 is a so-called hybrid system including two types of focus detection (adjustment) devices of a phase difference detection method (pupil division method) and a contrast detection method.

  The phase difference detection type focus detection apparatus includes the above-described focus detection optical system 72, a pair of line sensors 21, and a defocus amount detection unit 22 described later.

  The pair of line sensors 21 is composed of a CCD, a CMOS, or the like, and receives light beams that have passed through a pair of different regions (referred to as distance measuring pupils) on the exit pupil plane of the photographing optical system 71 via the focus detection optical system 72. It is configured to When an image (sensor image) optically equivalent to the pair of line sensors 21 is shown superimposed on a shooting screen observed through the finder optical system 76, for example, a rectangular frame is shown in FIG.

  FIG. 5 shows an example in which a pair of line sensors 21 are arranged so that the sensor image 21a extends in the vertical direction (Y direction in FIG. 5) of the camera shooting screen IF. A position corresponding to the pair of line sensors 21 on the IF is displayed in the focus detection area 100.

  Returning to FIG. 2, the defocus amount detection unit 22 obtains a shift amount (phase difference) between the waveforms of the pair of signals output from the pair of sensors 21 by a known correlation calculation, and determines the defocus amount of the photographing optical system 71. To detect.

  The control unit 60 instructs the lens driving unit 75 on the lens driving amount based on the detected defocus amount, and the lens driving unit 75 adjusts the focus of the photographing optical system 71.

  On the other hand, the arithmetic unit 32 constituting the contrast detection type focus adjustment device obtains a focus evaluation value based on contrast information of an image signal of a subject light beam photoelectrically converted by the image sensor 31.

  Then, the control unit 60 positions (focus adjusts) the photographing optical system 71 at a position (focus position) where the focus evaluation value obtained by the calculation unit 32 reaches a peak while moving the photographing optical system 71.

  Note that the line sensor 21 and the image sensor 31 have different readout directions of signals obtained by photoelectrically converting the formed image on the imaging screen IF. That is, the line sensor 21 reads a signal obtained by photoelectrically converting the formed image in the direction indicated by the arrow Y in FIG. 5 (the vertical direction of the shooting screen IF), whereas the image sensor 31 photoelectrically converts the formed image. The read signal is read out in the direction of the arrow X in FIG. 9 (the horizontal direction of the imaging screen IF).

  As shown in FIG. 3, the auxiliary light projection unit 78 of FIG. 2 emits light sources 41 and 51 such as LEDs, which are light sources, and light beams from the light emitting elements 41 and 51 through lenses 43 and 53, respectively. Pattern forming portions 42 and 52 that make a light beam including the pattern image and a drive circuit 61 that selectively drives the light emitting elements 41 and 51. Further, the pattern forming unit 42 forms a striped contrast pattern (bright and dark image) intersecting with the extending direction of the focus detection region 100 as shown in FIG. 5 as a pattern image, for example, as shown in FIG. A prism is arranged on the back surface of the light projection window 42a.

  On the other hand, the pattern forming unit 52 forms, for example, a stripe-shaped contrast pattern that intersects the signal reading direction (X direction) as shown in FIG. 9 as a pattern image, and the auxiliary light projection window 52a shown in FIG. It is configured by arranging a prism on the back surface.

  The camera control unit 60 shown in FIG. 2 performs focus detection (focus adjustment) control according to each detection method in which the focus detection apparatus 10 selectively operates as described above, and controls the light emitting elements 41 and 51. A control signal is output to a drive circuit 61 (see FIG. 3) that is selectively driven. The drive circuit 61 supplies current to the light emitting element 41 or 51 (see FIG. 3) by this control signal to drive it.

  5 and 6 are diagrams showing the pattern image projected onto the subject from the auxiliary light projection device superimposed on the photographing screen observed through the finder optical system 76. FIG.

  In FIG. 5, the pair of line sensors 21 of the focus detection device using the phase difference detection method is set so that the sensor image 21a equivalent thereto extends in the vertical direction (Y direction) with respect to the imaging screen IF as described above. The pattern image 42b projected from the auxiliary light projection window 42a is shown superimposed. This pattern image 42b is a non-periodic pattern of horizontal stripes in which a plurality of bright and dark images extending in the horizontal direction (X direction) in the figure are arranged at random intervals in the Y direction. The image 21a is projected onto a subject area that can sufficiently cover the image 21a.

  FIG. 6 shows an example in which a pair of line sensors of a focus detection apparatus using a phase difference detection method is set so that a sensor image 21b equivalent to the line sensor extends in the horizontal direction of the imaging screen IF. In this case, unlike the case of FIG. 5, the line sensor 21 shown in FIG. 2 has a plurality of photoelectric conversion elements constituting each line sensor along a direction corresponding to the horizontal direction (X direction) of the imaging screen IF. The division direction of the distance measuring pupil on the exit pupil plane by the focus detection optical system 72 is orthogonal to the case of FIG. Then, when the pattern image 42c projected from the auxiliary light projection device 78 is superimposed on the photographing screen IF, a plurality of bright and dark images extending in the vertical direction (Y direction) in FIG. Is a vertical stripe aperiodic pattern, and is projected onto the area of the subject that can sufficiently cover the sensor image 21b on the photographing screen IF.

  FIGS. 7 and 8 show the projection from the auxiliary light projection device when a pair of line sensors corresponding to the focus detection region of the focus detection device based on the phase difference detection method are set in the vertical direction and the horizontal direction of the shooting screen. It is a figure which shows the example of the pattern performed.

  The line sensor 21 is configured so that a sensor image 21a extending in the vertical direction and a sensor image 21b extending in the horizontal direction form a cross at the center of the photographing screen IF, and sensor images 21a extending in the vertical direction are set on the left and right sides of the line sensor 21, respectively. To do. In this case, when focus detection is performed using a line sensor corresponding to the sensor image 21a extending in the vertical direction, the auxiliary light projection device 78 has a plurality of bright and dark images extending in the X direction and having different widths as shown in FIG. Are projected on the range of the subject covering the three sensor images.

  When focus detection is performed using a line sensor corresponding to the sensor image 21b extending in the horizontal direction, as shown in FIG. 8, a plurality of bright and dark images extending in the Y direction and having different widths are spaced at random intervals in the X direction. The arranged vertical stripe aperiodic pattern 42e is projected from the auxiliary light projection device 78.

  FIG. 9 is a diagram showing a pattern image obtained by projecting the light beam emitted from the auxiliary light projection window 52 of FIG. 1 onto the subject, superimposed on a photographing screen observed through the finder optical system 76.

  A focus detection area 102 set on the photographing screen IF indicates a focus detection area of a contrast detection type focus detection apparatus. 2 is based on the contrast information of the image signal corresponding to the range (calculation area) 101 indicated by the rectangular frame including the focus detection area 102 among the image signals obtained corresponding to the photographing screen IF. Thus, the focus evaluation value is obtained. A pattern image 52b projected from the auxiliary light projection window 52a is a periodic pattern of vertical stripes in which a plurality of equal-width bright and dark images extending in the Y direction are arranged at equal intervals in the X direction, and can sufficiently cover the calculation area 101. Projected onto the subject area. It should be noted that the interval between the bright and dark images is made denser than in the case shown in FIG. 5 or the like, and the position (focus position) where the focus evaluation value peaks can be detected with high accuracy by obtaining more contrast information. It is for doing so.

  The camera 70 shown in FIG. 2 receives a control signal from the control unit 60 to the drive circuit 61 when the contrast of the image signal obtained by the image sensor 31 is low or the photometric device 80 determines that the subject has low brightness. Is output, and the light emitting element 41 or 51 corresponding to the operating focus detection method is turned on to irradiate the subject with auxiliary light.

  FIG. 4 is a flowchart showing the operation of the camera provided with the focus detection apparatus 10 according to the embodiment of the present invention. This flowchart starts when the release button of the camera is pressed halfway as an operation controlled by the control unit 60. In particular, it is determined that the subject is low in brightness by the above-described photometric device, or the subject is The operation when it is determined that the contrast is low is shown.

  In step S100, the control unit 60 turns on the light emitting element 41 and projects auxiliary light from the auxiliary light projection window 42a as auxiliary light for phase difference AF. As a result, a pattern image composed of bright and dark images of horizontal stripes is projected on the subject.

  In step S101, the light beam from the subject irradiated with the auxiliary light is received by the pair of line sensors 21 via the photographing lens 71, the focus detection optical system 72, and the like, and the defocus amount detection unit 22 detects the defocus amount. . Further, a driving signal is output to the lens driving unit 75 based on the detected defocus amount, and the photographing lens 71 is driven in the optical axis direction.

  In step S102, it is determined whether or not the phase difference AF is completed, and the phase difference AF is continued until the phase difference AF is completed. Note that the completion of the phase difference AF means a case where the detected defocus amount is in a focus determination range where it can be considered that the phase difference AF is in focus. When the phase difference AF is completed, the process proceeds to step S103, and when it is not completed, the process returns to S101 and the phase difference AF is repeated.

  In step S103, the light emitting element 41 is turned off and the auxiliary light for phase difference AF is turned off.

  In step S104, the light emitting element 51 is turned on, and auxiliary light is projected from the auxiliary light projection window 52a as auxiliary light for contrast AF. That is, the auxiliary light for phase difference AF is switched to the auxiliary light for contrast AF, whereby a pattern image composed of bright and dark images of vertical stripes is projected on the subject.

  In step S <b> 105, the quick return mirror 73 is retracted from the optical axis of the photographic lens, and a light flux from the subject irradiated with the auxiliary light is received by the image sensor 31 through the photographic lens 71. Based on the contrast information of the image signal in the range corresponding to the focus detection area among the image signals obtained by the image sensor 31, the calculation unit 32 obtains the focus evaluation value. Then, focus adjustment is performed so that the focus evaluation value obtained while driving the photographing lens 71 is maximized.

  In step S106, it is determined whether or not contrast AF is completed, and contrast AF is continued until completion. Note that the completion of contrast AF refers to the case where the photographing lens is focused at a position where the focus evaluation value is maximized. When contrast AF is completed, the process proceeds to step S107.

  In step S107, the light emitting element 51 is turned off, and the auxiliary light for contrast AF is turned off.

  According to the focus detection apparatus 10 of this embodiment, when the subject has low contrast or low brightness, focus detection (focus adjustment) is possible by irradiating auxiliary light regardless of the AF method used. Thus, it can be used without impairing the function as the hybrid AF.

  The focus detection method used in the focus detection apparatus of the present embodiment is not limited to the above embodiment. Further, the arrangement of the focus detection areas and the arrangement of the phase difference type line sensors (that is, the extending direction of the sensor image) in the photographing screen are not limited to the above embodiment.

  In the above embodiment, the auxiliary light is projected through the dedicated auxiliary light projection window according to the focus detection method, but the light beam including a plurality of types of pattern images is emitted from the common auxiliary light projection window. You may do it.

  Alternatively, even if the focus detection method is the same as in the case shown in FIG. 5 and the case shown in FIG. 6, a light beam including a different pattern image is irradiated from a different auxiliary light projection window depending on the extending direction of the sensor image. Anyway.

  Furthermore, although the case of the vertical stripe and the horizontal stripe was shown as a pattern image, it is not limited to this, For example, a radial thing may be sufficient. When the sensor is radial, it can be used regardless of whether the sensor signal readout direction is vertical or horizontal.

1 is a schematic external view of a camera including a focus detection device according to an embodiment of the present invention. It is a block diagram of the camera provided with the focus detection apparatus by embodiment of this invention. It is a block diagram which shows the schematic structure of an auxiliary light projection part. It is a flowchart which shows operation | movement of the camera provided with the focus detection apparatus by embodiment of this invention. It is a figure which superimposes and shows the pattern image projected on the to-be-photographed object from the auxiliary light projection apparatus on the imaging | photography screen observed through a finder optical system. It is a figure which superimposes and shows the pattern image projected on the to-be-photographed object from the auxiliary light projection apparatus on the imaging | photography screen observed through a finder optical system. An example of a pattern projected from the auxiliary light projection device when a pair of line sensors corresponding to the focus detection area of the focus detection device using the phase difference detection method is set in the vertical direction and the horizontal direction of the shooting screen is shown. FIG. An example of a pattern projected from the auxiliary light projection device when a pair of line sensors corresponding to the focus detection area of the focus detection device using the phase difference detection method is set in the vertical direction and the horizontal direction of the shooting screen is shown. FIG. It is a figure which superimposes and shows the pattern image projected on the to-be-photographed object from the auxiliary light projection apparatus on the imaging | photography screen observed through a finder optical system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Focus detection apparatus 21 Line sensor 22 Defocus amount detection part 31 Image pick-up element 32 Calculation part 41, 51 Light emitting element 42, 52 Pattern formation part 42b-42e, 52b Pattern image 43, 53 Lens 60 Control part 61 Drive circuit 70 Camera 71 Shooting lens 72 Focus detection optical system 78 Auxiliary light projection device 79 Illumination light irradiation device

Claims (7)

A plurality of types of focus detection means for detecting the focus adjustment state of the imaging optical system by different methods;
Illuminating means capable of irradiating illumination light including at least a pattern image;
A focus detection apparatus comprising: a control unit that changes illumination light emitted by the illumination unit according to a type of the focus detection unit. The focus detection apparatus according to claim 1,
The illumination means includes a plurality of optical systems independent from each other, and each optical system includes a light source that irradiates the illumination light, a pattern formation unit that forms the pattern image by illumination light from the light source, and the pattern formation A focus detection apparatus comprising: a projection optical system that projects the pattern image of a portion toward a subject. In the focus detection apparatus according to claim 1 or 2,
Each of the plurality of types of focus detection means detects the focus adjustment state based on a signal obtained by receiving an image light beam by the imaging optical system, and the readout directions of the signals are different from each other. Focus detection device. In the focus detection apparatus according to any one of claims 1 to 3,
The focus detection means includes a phase difference type focus detection means for obtaining the focus adjustment state based on a pair of images of the light fluxes that have passed through different pupil regions of the imaging optical system, and an image obtained by the imaging optical system. And a contrast type focus detection means for obtaining the focus adjustment state based on
The pattern image includes a first pattern having a striped light-dark image extending in a first direction and a second pattern having a striped light-dark image extending in a second direction orthogonal to the first direction,
The control unit controls the illumination unit to irradiate illumination light including the first pattern when using one of the phase difference type focus detection unit and the contrast type focus detection unit, When using the other, the focus detection apparatus irradiates illumination light including the second pattern. The focus detection apparatus according to any one of claims 1 to 4,
The first pattern is formed with different intervals between the bright and dark images,
The second pattern is formed such that the interval between the bright and dark images is narrower than the interval between the bright and dark images of the first pattern image,
The phase difference type focus detection means detects the first pattern,
The contrast type focus detection means detects a second pattern, and a focus detection apparatus.   A camera comprising the focus detection device according to any one of claims 1 to 5. Illumination means capable of irradiating a plurality of types of illumination light including at least a pattern image;
An illumination light irradiation apparatus comprising: a control unit that changes illumination light emitted by the illumination unit according to a type of the focus detection unit.

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