US3914647A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Light sensor for use with electronic flash units
Assignee: Rollei of America Inc
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Filing: 1974-03-29
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Granted: 1975-10-21
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Expires: 1994-03-29
Abstract
Abstract A light control system includes a first switching device, a light sensing device, and a flash device. The switching device is a selectively operable for providing a contact closure to effect the production of light from the flash device for the illumination of a scene to be photographed. A quench signal to effect the termination of the light provided by the flash device is generated by the light sensing device when sufficient light is received from the scene. The light sensing device includes circuitry which substantially precludes the generation of a false quench signal which might otherwise appear to terminate the production of light by the flash device prematurely.
Inventors
- 👤 Bert Broekstra
- 👤 Dennis J Wilwerding
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 21:41
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/30; H05B41/32; H05B41/325
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
270 words
For use with an electronic flash unit, a light sensor comprising first and second terminals for receiving a reference potential and a signal line potential, respectively, from the flash unit, said signal line potential exhibiting a flash-initiated enabling command change with respect to said reference potential when said flash unit is selectively rendered operative; light responsive integrating means and switching means connected to said terminals and rendered capable by said signal line potential of being switched from a first state to a second state by a triggering effect only after said signal line potential achieves a first predetermined level during said enabling command change; a threshold signal arrangement connected to said terminals and to said means for supplying to the latter a threshold signal derived from said signal line potential when the latter achieves a second predetermined level, which is higher than said first level, during said enabling command change; said means being operative upon receiving a predetermined quantity of light in the presence of said threshold signal to produce a triggering effect which causes said means to switch to said second state for an appropriate time period; and a reference voltage device connected to said means and responsive to the level of said signal line potential to bias said means, and to prevent said means from experiencing any triggering effect and from switching to said second state, while said signal line potential lies between said first and second levels, and responsive to the state of said means for producing a flash quench command change in said signal line potential as long as said means is in said second state.
Claim 2
Dependent Claim
270 words
For use with an electronic flash unit, a light sensor comprising first and second terminals for receiving a reference potential and a signal line potential, respectively, from the flash unit, said signal line potential exhibiting a flash-initiated enabling command change with respect to said reference potential when said flash unit is selectively rendered operative; light responsive integrating means and switching means connected to said terminals and rendered capable by said signal line potential of being switched from a first state to a second state by a triggering effect only after said signal line potential achieves a first predetermined level during said enabling command change; a threshold signal arrangement connected to said terminals and to said means for supplying to the latter a threshold signal derived from said signal line potential when the latter achieves a second predetermined level, which is higher than said first level, during said enabling command change; said means being operative upon receiving a predetermined quantity of light in the presence of said threshold signal to produce a triggering effect which causes said means to switch to said second state for an appropriate time period; and a reference voltage device connected to said means and responsive to the level of said signal line potential to bias said means, and to prevent said means from experiencing any triggering effect and from switching to said second state, while said signal line potential lies between said first and second levels, and responsive to the state of said means for producing a flash quench command change in said signal line potential as long as said means is in said second state.
Claim 3
Dependent Claim
15 words
A light sensor as specified in claim 1, wherein said device is a zener diode.
Claim 4
Dependent Claim
107 words
A light sensor as specified in claim 2, wherein said means include a silicon controlled rectifier which, in the presence of said triggering effect, becomes conductive to switch said means from said first state to said second state; said rectifier has an anode connected to said first terminal, a gate connected in a light integrating circuit to said second terminal, and a cathode connected through said zener diode to said second terminal; and wherein said zener diode is poled to reverse-bias the gate-cathode junction of said rectifier when the latter is not conductive, and to raise the potential of said second terminal while said rectifier is conductive.
Claim 5
Dependent Claim
18 words
A light sensor as specified in claim 3, wherein said rectifier is a light activated silicon controlled rectifier.
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) | 1978-10-20 | 1979-04-21 | 1979-10-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-20 | 1983-04-21 | 1983-10-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-20 | 1987-04-21 | 1987-10-21 | $7700.00 | Window Closed / Lapsed |