EP0089804A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Focus state detector
Assignee: Olympus Corp
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Filing: 1983-03-16
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Granted: —
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Expires: 2003-03-16
Abstract
Abstract A focus state detector has light receiving transducers (6A, 6B) formed so that the light levels received on the respective light receiving surfaces (5A, 5B) differ depending on the distance from an object that is to be viewed or photographed. In conventional focus state detectors for detecting whether an optical image of an object is in a correct focusing state with the image clearly formed at a predetermined image forming surface, if the object to be photographed is dark, or if a dark-ground optical system is used, the detector output of the or each light receiving transducer element will generally be so small that focus state detection is virtually impossible, or at best the precision of the focus state detection will be relatively low. To overcome this problem means project a light onto an object (9) through a small aperture (4) to provide a spot illumination for focus state detection, and the light receiving transducer means (6A, 6B) are so formed that the light levels reaching the respective light receiving surfaces (5A, 5B) differ depending on distance from the object (9).
Inventors
- 👤 Shinichi Olympus Optical Co. Ltd. Nishigaki
- 👤 Kazumasa Olympus Optical Co. Ltd. Matsuo
- 👤 Atsushi Olympus Optical Co. Ltd. Miyazaki
- 👤 Yoshio Olympus Optical Co. Ltd. Shishido
- 👤 Shinichi Olympus Optical Co. Ltd. Kato
- 👤 Susumu Olympus Optical Co. Ltd. Takahashi
- 👤 Takeaki Olympus Optical Co. Ltd. Nakamura
- 👤 Akibumi Olympus Optical Co. Ltd. Ishikawa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 16:40
CPC Classifications
G; G02; G02B; G02B7/00; G02B7/28; G02B7/30; G02B7/32
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
129 words
A focus state detector in which an objective lens is provided to form an image of an object to be viewed or photographed in a predetermined image plane, a light source is provided to project a light spot onto said object via said objective lens, a plurality of photoelectric transducers is arranged at a position nearly optically corresponding to said image plane, and the arrangement of the individual transducers being such that a minimum level of light is incident when said objective lens is in the correct focus state, and such that mutually different levels of light are incident on respective transducers in dependence upon the magnitude and direction of any focussing error, whereby a comparison of the transducer outputs indicates the type of re-adjustment needed for correct focus.
Claim 2
Dependent Claim
129 words
A focus state detector in which an objective lens is provided to form an image of an object to be viewed or photographed in a predetermined image plane, a light source is provided to project a light spot onto said object via said objective lens, a plurality of photoelectric transducers is arranged at a position nearly optically corresponding to said image plane, and the arrangement of the individual transducers being such that a minimum level of light is incident when said objective lens is in the correct focus state, and such that mutually different levels of light are incident on respective transducers in dependence upon the magnitude and direction of any focussing error, whereby a comparison of the transducer outputs indicates the type of re-adjustment needed for correct focus.
Claim 3
Dependent Claim
36 words
A focus detector as claimed in Claim 1, in which said transducers are themselves so arranged that the light path lengths to the respective light receiving surfaces from the object to be photographed are substantially different.
Claim 4
Dependent Claim
43 words
A focus state detector as claimed in Claim 1, in which said transducers are at the same distance from the object to be photographed, but a transparent member is positioned in front of at least one transducer to vary. the light path length.
Claim 5
Dependent Claim
53 words
A focus state detector as claimed in Claim 1, in which said transducers are at the same distance from the object to be photographed, but a filter member is arranged in front of at least one transducer, which filter has a transmission characteristic dependent upon the magnitude and direction of any focussing error.
Claim 6
Dependent Claim
33 words
A focus state detector as claimed in Claim 2, in which said transducers are arranged with their respective light receiving surfaces at stepped positions in the optical axial direction of the objective lens.
Claim 7
Dependent Claim
31 words
A focus state detector as claimed in Claim 2, in which said transducers are arranged with their respective light receiving surfaces inclined to the optical axial direction of the subjective lens.
Claim 8
Dependent Claim
21 words
A focus state detector as claimed in Claim 3, in which said transparent member is a plate-shaped member having parallel faces.
Claim 9
Dependent Claim
18 words
A focus state detector as claimed in Claim 3, in which said transparent member is a wedge-shaped prism.
Claim 10
Dependent Claim
35 words
A focus state detector as claimed in Claim 4, in which said filter member is a plate formed by a cutting from an optical fibre bunch made at an angle inclined to the fibre direction.
Claim 11
Dependent Claim
40 words
A focus state detector as claimed in Claim 4, in which said filter member is a plate formed by a cutting from a member made of overlapping transparent laminar members in layers at an angle inclined to the cutting direction.
Claim 12
Dependent Claim
39 words
A focus state detector as claimed in Claim 4, in which said filter member is a plate formed by a cutting from a member made of overlapping transparent films in layers at an angle inclined to the cutting direction.
Claim 13
Dependent Claim
24 words
A focus state detector as claimed in any preceding Claim, in which said light source projects light of a wavelength in the visible range.
Claim 14
Dependent Claim
28 words
A focus state detector as claimed in any one of Claims 1 to 11, in which said light source projects light of a wavelength in an infrared range.
Claim 15
Dependent Claim
37 words
A focus state detector as claimed in any preceding Claim, in which automatic setting means are provided to adjust the objective lens under the control of output signals from said transducers to achieve a correct focus state.
References Cited (Backward Citations)
US3356854A
Cited
FR1528189A
Cited
US3975631A
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GB1477625A
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FR2344046A1
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DE2923573A1
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EP0010241A2
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US4314150A
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DE2946185A1
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FR2459991A1
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