US3753387A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bridge type exposure meter
Assignee: Nikon Corp
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Filing: 1972-08-22
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Granted: 1973-08-21
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Expires: 1992-08-22
Abstract
Abstract An exposure determining device comprises a bridge circuit which includes a photoelectric element for receiving light from an object, and first, second and third resistors. The first resistor is variable for controlling the balance of the bridge circuit and for introducing an exposure factor. One end of the first resistor is connected to one end of the photoelectric element, and one end of the second resistor is connected to the other end of the photoelectric element. One end of the third resistor is connected to the other end of the first resistor. Means for detecting the balance of the bridge circuit is provided and includes npn and pnp transistors. The npn transistor has its base connected to the junction between the photoelectric element and the first resistor and has its emitter connected to the other end of the third resistor. The pnp transistor has its base connected to that junction and has its emitter connected to the other end of the second resistor. The detecting means may produce a first and a second signal representing the balance and unbalance of the bridge circuit. A voltage divider is connected between the other ends of the second and third resistors. A third transistor is provided and has its base connected to the voltage divider. Control circuit means is connected to the collectors of the npn and pnp transistors to receive the first and second signals from the detecting means for determining a proper exposure.
Inventors
- 👤 O Maida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 07:25
CPC Classifications
G; G03; G03B; G03B17/00; G03B17/18
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
285 words
An exposure determining device comprising: a bridge circuit including a photoelectric element adapted to receive light from an object to be photographed, a first resistance element having one end connected to one end of said photoelectric element, said first resistance element being variable for controlling the balance of said bridge circuit and for introducing an exposure factor, a second resistance element having one end connected to the other end of said photoelectric element, and a third resistance element having one end connected to the other end of said first resistance element; means for detecting the balance of the bridge circuit, said detecting means including an npn transistor whose base terminal is connected to the junction between said photoelectric element and said first resistance element and whose emitter terminal is connected to the other end of said third resistance element, and a pnp transistor whose base terminal is connected to said junction and whose emitter terminal is connected to the other end of said second resistance element, said detecting means producing a first signal upon balancing of said bridge circuit and a second signal upon unbalancing of said bridge circuit; a voltage divider connected between the other ends of said second and third resistance elements; a third transistor whose base terminal is connected to said voltage divider so that the voltage divided by said voltage divider is applied to said base terminal of said third transistor and whose emitter and collector terminals are connected between the other ends of said second and third resistance elements; and control circuit means connected to said collector terminals of said npn and pnp transistors to receive said first and second signals from said detecting means for determining a proper exposure.
Claim 2
Dependent Claim
285 words
An exposure determining device comprising: a bridge circuit including a photoelectric element adapted to receive light from an object to be photographed, a first resistance element having one end connected to one end of said photoelectric element, said first resistance element being variable for controlling the balance of said bridge circuit and for introducing an exposure factor, a second resistance element having one end connected to the other end of said photoelectric element, and a third resistance element having one end connected to the other end of said first resistance element; means for detecting the balance of the bridge circuit, said detecting means including an npn transistor whose base terminal is connected to the junction between said photoelectric element and said first resistance element and whose emitter terminal is connected to the other end of said third resistance element, and a pnp transistor whose base terminal is connected to said junction and whose emitter terminal is connected to the other end of said second resistance element, said detecting means producing a first signal upon balancing of said bridge circuit and a second signal upon unbalancing of said bridge circuit; a voltage divider connected between the other ends of said second and third resistance elements; a third transistor whose base terminal is connected to said voltage divider so that the voltage divided by said voltage divider is applied to said base terminal of said third transistor and whose emitter and collector terminals are connected between the other ends of said second and third resistance elements; and control circuit means connected to said collector terminals of said npn and pnp transistors to receive said first and second signals from said detecting means for determining a proper exposure.
Claim 3
Dependent Claim
68 words
An exposure determining device according to claim 1, wherein said control circuit means includes first and second indicating means actuated in response to the first and second signals, said first indicating means being actuated to indicate a proper exposure when said control circuit means receives said frist signal, said second indicating means being actuated to indicate an improper exposure when said control circuit means receives said second signal.
Claim 4
Dependent Claim
29 words
An exposure determining device according to claim 1, wherein said control circuit means include means for controlling a diaphragm aperture opening in response to said first and second signals.
Claim 5
Dependent Claim
37 words
An exposure determining device according to claim 1, further comprising a source of potential connected between the junction between said photoelectric element and said second resistance element and the junction between said first and third resistance elements.
Claim 6
Dependent Claim
37 words
An exposure determining device according to claim 1, wherein said voltage divider includes two resistors connected in series with each other, said base terminal of said third transistor being connected to the junction between said two resistors.
Claim 7
Dependent Claim
21 words
An exposure determining device according to claim 1, wherein said bridge circuit is in balance when the proper exposure is obtained.
Claim 8
Dependent Claim
69 words
An exposure determining device according to claim 6, wherein both of said npn and pnp transistors become non-conductive upon balancinG of said bridge circuit and one of said npn and pnp transistors becomes conductive upon unbalancing of said bridge circuit, said non-conductivity of both said npn and pnp transistors serving as said first signal, said conductivity of one of said npn and pnp transistors serving as said second signal.
Claim 9
Dependent Claim
91 words
An exposure determining device according to claim 7, wherein said control circuit means include first and second indicating means actuated in response to said first and second signals, said first indicating means being actuated to indicate an under-exposure when one of said pnp and npn transistors is non-conductive, said second indicating means being actuated to indicate an over-exposure when the other of said pnp and npn transistors is non-conductive, said first and second indicating means being actuated to indicate a proper exposure when both said pnp and npn transistors are non-conductive.
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) | 1976-08-20 | 1977-02-19 | 1977-08-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-20 | 1981-02-19 | 1981-08-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-20 | 1985-02-19 | 1985-08-21 | $7700.00 | Window Closed / Lapsed |