US3842424A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Exposure control device in single-lens reflex camera
Assignee: Canon Inc
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Filing: 1973-04-11
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Granted: 1974-10-15
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Expires: 1993-04-11
Abstract
Abstract This invention relates to an exposure control device for automatically controlling the shutter speed in a camera, especially a single-lens reflex camera. It utilizes the reset time characteristic of a light receiving element such as photoconductive cell or the like having a slow response characteristic to control the camera shutter to a high shutter speed, and utilizes light reflected from the surface of a film to control the shutter to an intermediate or a lower shutter speed.
Inventors
- 👤 T Tsunekawa
- 👤 S Nakamoto
- 👤 G Hasegawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:35
CPC Classifications
G; G03; G03B; G03B19/00; G03B19/02; G03B19/12; G03B7/00; G03B7/08; G03B7/081; G03B7/083; G03B7/099; G03B7/0993; G03B7/0997; G03B7/09971; G03B7/09974; G03B7/09976
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
240 words
An exposure control device in a singlelens reflex camera for metering light which has passed through the picture-taking lens of the camera to automatically effect a shutter speed control, said device comprising: light receiving means disposed so as to receive, before release of the shutter, at least part of the light which has passed through the picture-taking lens and also to receive, after the release of the shutter, light reflected by a film surface, said means having a relatively slow response characteristic to permit high speed shutter control by utilizing said characteristic of said means, while also enabling low speed shutter control by the light reflected by the film surface; optical means for directing at least part of the light which has passed through said picture-taking lens to said light receiving means, said optical means being movable out of the picturetaking optical path to interrupt, during picture-taking, the direction by said optical means to said light receiving means of said light which has passed through said picture-taking lens; control means connected to said light receiving means to control the opening and closing of the shutter of the camera, said control means including: a time limit circuit electrically connected with said light receiving means; a switching circuit connected with said time limit circuit; and actuator means for closing the shutter connected with said switching circuit and adapted to actuate the shutter to close in response to reversal of said switching circuit.
Claim 2
Dependent Claim
240 words
An exposure control device in a singlelens reflex camera for metering light which has passed through the picture-taking lens of the camera to automatically effect a shutter speed control, said device comprising: light receiving means disposed so as to receive, before release of the shutter, at least part of the light which has passed through the picture-taking lens and also to receive, after the release of the shutter, light reflected by a film surface, said means having a relatively slow response characteristic to permit high speed shutter control by utilizing said characteristic of said means, while also enabling low speed shutter control by the light reflected by the film surface; optical means for directing at least part of the light which has passed through said picture-taking lens to said light receiving means, said optical means being movable out of the picturetaking optical path to interrupt, during picture-taking, the direction by said optical means to said light receiving means of said light which has passed through said picture-taking lens; control means connected to said light receiving means to control the opening and closing of the shutter of the camera, said control means including: a time limit circuit electrically connected with said light receiving means; a switching circuit connected with said time limit circuit; and actuator means for closing the shutter connected with said switching circuit and adapted to actuate the shutter to close in response to reversal of said switching circuit.
Claim 3
Dependent Claim
18 words
An exposure control device according to claim 1, wherein said light receiving means is of the photoconductive type.
Claim 4
Dependent Claim
46 words
An exposure control device according to claim 1, wherein said optical means is a quick return mirror comprising a half-mirror portion and a total reflection mirror, and said light receiving means has the light receiving surface thereof disposed on the optical axes of said two mirrors.
Claim 5
Dependent Claim
54 words
An exposure control device according to claim 1, wherein said picture-taking lens has a preset aperture device therein, and said light receiving means comprises a light receiving element and light beam restricting means which is operatively associated with said preset aperture device of said picture-taking lens to restrict the quantity of light passed therethrough.
Claim 6
Dependent Claim
23 words
An exposure control device according to claim 1 wherein said light receiving element is used for indicating information on exposure prior to phototaking.
Claim 7
Dependent Claim
44 words
An exposure control device according to claim 1 further comprising: electric means for indicating information on exposure prior to phototaking, and switching means for electrically connecting said light receiving element with said indicating means, said light receiving means being utilized also for the indication.
Claim 8
Dependent Claim
194 words
An exposure control device in a singlelens reflex camera for metering light which has passed through the picture-taking lens of the camera to automatically effect a shutter speed control, said device comprising: first light receiving means for receiving light reflected by the surface of a film; second light receiving means for receiving at least part of the light which has passed through the picturetaking lens, said second light receiving means having a slow response characteristic; said first light receiving means being used mainly for low speed shutter control and said second light receiving means being used mainly for high speed shutter control; optical means movable to prevent light from passing to said second light receiving means during picturetaking, said optical means being moved to its lightintercepting position in response to a shutter release operation prior to the opening of the shutter and returned to its non-intercepting position after the closing of the shutter; control means connected to said first and second light receiving means to control the opening and the closing of the shutter, said control means being operated by the output of one of said two light receiving means to close the shutter.
Claim 9
Dependent Claim
194 words
An exposure control device in a singlelens reflex camera for metering light which has passed through the picture-taking lens of the camera to automatically effect a shutter speed control, said device comprising: first light receiving means for receiving light reflected by the surface of a film; second light receiving means for receiving at least part of the light which has passed through the picturetaking lens, said second light receiving means having a slow response characteristic; said first light receiving means being used mainly for low speed shutter control and said second light receiving means being used mainly for high speed shutter control; optical means movable to prevent light from passing to said second light receiving means during picturetaking, said optical means being moved to its lightintercepting position in response to a shutter release operation prior to the opening of the shutter and returned to its non-intercepting position after the closing of the shutter; control means connected to said first and second light receiving means to control the opening and the closing of the shutter, said control means being operated by the output of one of said two light receiving means to close the shutter.
Claim 10
Dependent Claim
38 words
An exposure control device according to claim 7, wherein said first light receiving means is a light receiving element of the photoelectromotive type and said second light receiving means is a light receiving element of the photoconductive type.
Claim 11
Dependent Claim
50 words
An exposure control device according to claim 8 wherein said control means comprises capacitors respectively arranged to be charged by the outputs of said two light receiving means and is so constituted as to control the closing time of the shutter by whichever of said capacitors charges the more rapidly.
Claim 12
Dependent Claim
67 words
An exposure control device according to claim 9, wherein said control means includes first and second switching circuit means and electromagnetic means connected so as to be responsive to the switching circuit means, said electromagnetic means being arranged to be actuated after operation of the shutter to control the closing operation of the shutter, and said switching circuit means having their inputs respectively connected to said capacitors.
Claim 13
Dependent Claim
17 words
An exposure control device according to claim 7, wherein said optical means is a quick return mirror.
Claim 14
Dependent Claim
31 words
An exposure control device according to claim 2, wherein said second light receiving means is disposed at a position adjacent a focusing screen and conjugate with the surface of the film.
Claim 15
Dependent Claim
43 words
An exposure control device according to claim 7, further comprising exposure value indicating means electrically connected to said second light receiving means, said indicating means including indicator means and amplifier means the input of which is connected to said second light receiving means.
Claim 16
Dependent Claim
18 words
An exposure control device according to claim 13, wherein said amplifier means comprises a field effect transistor (FET).
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-10-14 | 1978-04-15 | 1978-10-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-14 | 1982-04-15 | 1982-10-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-14 | 1986-04-15 | 1986-10-15 | $7700.00 | Window Closed / Lapsed |