US3944370A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Exposure time indication apparatus
Assignee: Pentax Corp
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Filing: 1974-09-06
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Granted: 1976-03-16
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Expires: 1994-09-06
Abstract
Abstract A voltage proportional to the APEX indication quantity for exposure time is coupled to one terminal of a meter through a buffer stage transistor. Circuit means produce a reference potential which is applied to the other terminal of the meter. The buffer stage transistor is biased by circuitry including a feedback stage transistor with the biasing being such that substantially constant collector current operation is ensured.
Inventors
- 👤 Masahiro Kawasaki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 08:04
CPC Classifications
G; G01; G01J; G01J1/00; G01J1/42; G01J1/44; G01R; G01R17/00; G01R17/02; G01R19/00; G01R19/10; G03; G03B; G03B17/00; G03B17/18
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
151 words
Exposure time indication apparatus comprising: circuit means for producing a reference potential; a two-terminal meter having one terminal connected to receive the reference potential; an exposure time measurement section including an output stage transistor having base and emitter electrodes between which there is developed a voltage porportional to the APEX indication quantity for exposure time; a buffer stage junction transistor having its base-emitter junction connected in series between the base electrode of the output stage transistor and the other terminal of the meter; biasing means for causing the buffer stage transistor to operate with a substantially constant collector current, the biasing means including a feedback stage junction transistor having its collector and base electrode respectively connected to the emitter and collector electrodes of the buffer stage transistor; and wherein one of the buffer stage and feedback stage transistors is of the p-n-p type and the other is of the n-p-n type.
Claim 2
Dependent Claim
151 words
Exposure time indication apparatus comprising: circuit means for producing a reference potential; a two-terminal meter having one terminal connected to receive the reference potential; an exposure time measurement section including an output stage transistor having base and emitter electrodes between which there is developed a voltage porportional to the APEX indication quantity for exposure time; a buffer stage junction transistor having its base-emitter junction connected in series between the base electrode of the output stage transistor and the other terminal of the meter; biasing means for causing the buffer stage transistor to operate with a substantially constant collector current, the biasing means including a feedback stage junction transistor having its collector and base electrode respectively connected to the emitter and collector electrodes of the buffer stage transistor; and wherein one of the buffer stage and feedback stage transistors is of the p-n-p type and the other is of the n-p-n type.
Claim 3
Dependent Claim
18 words
The apparatus of claim 1 wherein the output stage and feedback stage transistors are of the same type.
Claim 4
Dependent Claim
30 words
The apparatus of claim 1 wherein the biasing means further includes two constant current sources connected in series with the collector and emitter electrodes respectively of the buffer stage transistor.
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) | 1979-03-16 | 1979-09-15 | 1980-03-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-16 | 1983-09-15 | 1984-03-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-16 | 1987-09-15 | 1988-03-16 | $7700.00 | Window Closed / Lapsed |