Focus detection device
First Claim
1. In an optical instrument having an image forming optical system which is movable along an optical axis to form an image of an object on a predetermined imaging plane, a system for detecting the focusing condition of said optical system with respect to said object, comprising:
- (A) radiation generating means for generating radiation;
(B) first optical means for projecting the radiation generated by said radiation generating means toward said object through a portion of an effective aperture of said image forming optical system, wherein the center of gravity of distribution, on a plane including said effective aperture, of the projected radiation is remote from the optical axis of said optical system;
said radiation generating means being disposed substantially in coincidence with a plane optically equivalent to said predetermined imaging plane which is set by said first optical means;
(C) radiation sensing means capable of responding to the radiation generated by said radiation generating means;
(D) second optical means for causing at least a part of the radiation reflected by said object and then entering through another portion of the effective aperture of said image forming optical system to be directed to said radiation sensing means, wherein the center of gravity of distribution on the plane including the effective aperture, of the radiation directed to said radiation sensing means is remote from the optical axis of said optical system;
said radiation sensing means being disposed substantially in coincidence with a position optically equivalent to the location of said radiation generating means which is set by said first and second optical means so that the position of the center of gravity of the radiation distribution on an effective radiation surface of said radiation sensing means varies in accordance with the focus adjusted condition of said image forming optical system with respect to said object.
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Abstract
A so-called active-type focus detection device applicable to optical instruments such as camera is provided with light emitting means and photoelectric detector means disposed at two positions conjugate with the pre-arranged focal plane of an image-forming optical system whose focus adjusted condition is to be detected or two positions optically equivalent to the two conjugate positions, and the light emitted from the light emitting means is projected toward an object to which the camera is to be focused, through the image-forming optical system. The light then reflected by the object is received by the photoelectric detector means through the image-forming optical system and the focused condition of the image-forming optical system with respect to the object is detected in accordance with the electrical output of the photoelectric detector means.
According to a preferred embodiment of the present invention, the light emitted from the light-emitting means is projected upon the object by utilization of the maximum half area of the effective aperture of the image-forming optical system while, of the light that is reflected into the image-forming optical system by the object, the light passing through the maximum other half area of the effective aperture of the image-forming optical system is directed to the photoelectric detector means, whereby the position of incidence of the light flux on the light-receiving surface of the photoelectric detector means is varied correspondingly to the focus adjusted condition of the image-forming optical system with respect to the object and the variation in position of incidence of the light flux on the light-receiving surface of the photoelectric detector means is detected in accordance with the electrical output of the photoelectric detector means, thereby detecting the focus adjusted condition of the image-forming optical system with respect to the object.
30 Citations
52 Claims
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1. In an optical instrument having an image forming optical system which is movable along an optical axis to form an image of an object on a predetermined imaging plane, a system for detecting the focusing condition of said optical system with respect to said object, comprising:
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(A) radiation generating means for generating radiation; (B) first optical means for projecting the radiation generated by said radiation generating means toward said object through a portion of an effective aperture of said image forming optical system, wherein the center of gravity of distribution, on a plane including said effective aperture, of the projected radiation is remote from the optical axis of said optical system; said radiation generating means being disposed substantially in coincidence with a plane optically equivalent to said predetermined imaging plane which is set by said first optical means; (C) radiation sensing means capable of responding to the radiation generated by said radiation generating means; (D) second optical means for causing at least a part of the radiation reflected by said object and then entering through another portion of the effective aperture of said image forming optical system to be directed to said radiation sensing means, wherein the center of gravity of distribution on the plane including the effective aperture, of the radiation directed to said radiation sensing means is remote from the optical axis of said optical system; said radiation sensing means being disposed substantially in coincidence with a position optically equivalent to the location of said radiation generating means which is set by said first and second optical means so that the position of the center of gravity of the radiation distribution on an effective radiation surface of said radiation sensing means varies in accordance with the focus adjusted condition of said image forming optical system with respect to said object. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A zoom lens assembly comprising:
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(A) a focusing lens group having an optical axis and movable along the axis so as to form an image of an object on a predetermined imaging plane; (B) a zooming lens group positioned behind said focusing lens group and movable along said axis so as to effect zooming; (C) radiation generating means for generating radiation; (D) first optical means for projecting the radiation generated from said radiation generating means toward said object through said focusing lens group; said radiation generating means being disposed substantially in coincidence with a plane optically equivalent to said predetermined imaging plane which is set by said first optical means; (E) radiation sensing means capable of responding to the radiation generated from said radiation generating means; and (F) second optical means for causing at least part of the radiation reflected by said object and then entering through said focusing lens group to be directed to said radiation sensing means; said radiation sensing means being disposed substantially in coincidence with a position optically equivalent to the location of said radiation generating means which is set by said first and second optical means so that an electrical output of said radiation sensing means is variable in accordance with the focus adjusted condition of said image forming optical system with respect to said object. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. In an optical instrument having an objective lens which is movable along an optical axis so as to form an image of an object on a predetermined focal plane, a system for detecting the focusing condition of said objective lens to said object, comprising:
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(A) a radiation source for generating a radiation ray; (B) a radiation sensor responsive to the radiation ray generated by said radiation source; and (C) an optical system positioned behind said objective lens for projecting the radiation ray generated by said radiation source toward said object through a portion of an effective aperture of the objective lens to cause at least a part of the radiation ray which is reflected by the object and then enters through another portion of the effective aperture of the objective lens, to be directed to said radiation sensor, wherein the center of gravity of distribution on a plane including said effective aperture, of the projected radiation and of the radiation ray directed to said radiation sensor are respectively remote from the optical axis of the objective lens; said radiation source being disposed substantially in coincidence with a plane optically equivalent to said predetermined focal plane with respect to said optical system, said radiation sensor being disposed substantially in coincidence with a position optically equivalent to the location of the radiation source with respect to the optical system so that the position of the center of gravity of distribution of the reflected part of the radiation ray on an effective radiation-receiving surface of the radiation sensor varies in accordance with the focusing condition of the objective lens to the object. - View Dependent Claims (37, 38, 39, 40, 41)
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42. A system for detecting focusing condition of an objective lens to an object, comprising:
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(A) a radiation projector for projecting a radiation ray through a portion of an effective aperture of said objective lens toward said object; (B) a radiation detector for detecting the radiation ray reflected by the object and then entering through the other portion of the effective aperture of the objective lens, said radiation detector being disposed so that the position of the center of gravity of distribution of the reflected ray on an effective radiation detecting surface of the radiation detector varies in accordance with the focusing condition of the objective lens to the object, said effective radiation detecting surface of the radiation detector being divided into two regions of almost the same size by a boundary which traverses the direction of the variation of the position of the center of gravity of the distribution of the reflected ray on the surface in accordance with change in the focusing condition of the objective lens; (C) a projection control circuit for causing said radiation projector to intermittently project the radiation ray; and (D) a focus detecting circuit for detecting the focusing condition of said objective lens to the object on the basis of an electrical output of said radiation detector, said focus detecting circuit being arranged to detect a relative positional relationship of the position of the center of gravity of the distribution of the radiation ray on the detecting surface of the radiation detector with respect to said boundary of said two regions by comparing a difference signal between a response output of the radiation detector corresponding to a first one of said two regions when said radiation projector is projecting the radiation ray and a response output corresponding to said first region when the projector is not projecting the radiation ray, with a difference signal between a response output of the radiation detector corresponding to the second one of said two regions when the radiation projector is projecting the radiation ray and a response output corresponding to said second region when the projector is not projecting the radiation ray.
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43. A zoom lens assembly comprising:
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(A) a lens system including a zooming lens group operable for effecting zooming and a focusing lens group operable for effecting focusing of the whole lens system onto an object; (B) a radiation source for generating a radiation ray; (C) a radiation sensor responsive to the radiation ray generated by said radiation source; and (D) an optical system positioned between said focusing lens group and said zooming lens group of said lens system, and arranged for projecting the radiation ray generated by said radiation source toward said object through the focusing lens group to cause at least a portion of the radiation ray which is reflected by the object and then enters through the focusing lens group, to be directed to said radiation sensor; said radiation sensor being disposed at a predetermined position with respect to said optical system so that the incident condition of the reflected portion of the ray on the sensor varies in accordance with the focusing condition of the whole lens system effected by the focusing lens group. - View Dependent Claims (44, 45, 46, 47, 48, 49)
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50. A zoom lens assembly comprising:
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(A) a lens system including a zooming lens group operable for effecting zooming and a focusing lens group operable for effecting focusing of the whole lens system onto an object; (B) a lens housing for housing therein said lens system; (C) a radiation projector disposed within said housing for projecting a radiation ray through a portion of said lens system toward said object; and (D) a radiation detector disposed within said housing for detecting the radiation ray reflected by said object through a portion of said lens system, said detector being arranged so that the incident condition of the reflected ray on the detector varies in accordance with focusing condition of the whole lens system effected by said focusing lens group. - View Dependent Claims (51)
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52. A system for detecting focusing condition of an objective lens to an object, comprising:
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(A) a radiation projector for projecting a radiation ray through a portion of an effective aperture of said objective lens toward said object; (B) a radiation detector for detecting the radiation ray reflected by the object and then entering through another portion of the effective aperture of the objective lens, said radiation detector being disposed so that the position of the center of gravity of distribution of the reflected ray on an effective radiation-detecting surface of the radiation detector varies in accordance with focusing condition of the objective lens to the object, said radiation detector being a self-scanning type radiation detector which has an array of a plurality of detecting elements and produces a time-seriated scanning output indicative of the distribution of the radiation ray on the detecting surface thereof; and (C) a focus detecting circuit coupled to said radiation detector to detect focus-adjusted condition of said objective lens with respect to said object on the basis of the time-seriated output of said radiation detector, said detecting circuit being designed to detect the deviation of the position of the center of gravity of the distribution of said radiation ray from the center of the effective radiation-receiving surface of said radiation detector, on the basis of the time-seriated output of said radiation detector.
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Specification