US3790789A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Circuit for controlling exposure
Assignee: Individual
•
Filing: 1972-09-22
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Granted: 1974-02-05
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Expires: 1992-09-22
Abstract
Abstract A circuit for controlling exposure which has a Miller integrator for integrating a photocurrent from a photoelectric converting light acceptor, a circuit for generating a predetermined set level, and a level comparator for generating an exposure finishing signal when the output of the integrator arrives at the predetermined level set by the level generating circuit. Thus, a great deal of electric current can be obtained without using a photoelectric tube or thyratron. A low impedance circuit may be used which is not affected by leaking current or dark current so as not to deteriorate the elements and thereby improve circuit reliability.
Inventors
- 👤 I Takahashi
- 👤 T Kimura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 10:45
CPC Classifications
G; G03; G03B; G03B27/00; G03B27/72; G03B27/80; G01; G01J; G01J1/00; G01J1/42
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
218 words
A circuit for controlling the exposure of a photographic print through a negative comprising: a. first and second photoelectric converting light acceptor means for generating first and second photocurrents, respectively, in accordance with the light passing through said negative; b. first and second resistor means respectively connected in series with said first and second photoelectric converting light acceptor means, the series connection of said second resistor means and said second photoelectric converting light acceptor means being connected to the junction of said first resistor means and said first photoelectric converting light acceptor means; c. Miller integrator means including an operational amplifier, capacitor means connected between the input and output of said operational amplifier, and switch means in parallel with said capacitor means whereby upon the opening of said switch means said capacitor is charged, said series connection of said second resistor means and said second photoelectric converting light acceptor means being connected as the input resistance of said operational amplifier thereby determining the integrating time constant of said Miller integrator; d. level generator means for generating a signal having a predetermined level; and e. level comparator means for comparing the output of said Miller integrator means to said predetermined level and for generating an exposure finishing signal when the output of said Miller integrator reaches said predetErmined level.
Claim 2
Dependent Claim
218 words
A circuit for controlling the exposure of a photographic print through a negative comprising: a. first and second photoelectric converting light acceptor means for generating first and second photocurrents, respectively, in accordance with the light passing through said negative; b. first and second resistor means respectively connected in series with said first and second photoelectric converting light acceptor means, the series connection of said second resistor means and said second photoelectric converting light acceptor means being connected to the junction of said first resistor means and said first photoelectric converting light acceptor means; c. Miller integrator means including an operational amplifier, capacitor means connected between the input and output of said operational amplifier, and switch means in parallel with said capacitor means whereby upon the opening of said switch means said capacitor is charged, said series connection of said second resistor means and said second photoelectric converting light acceptor means being connected as the input resistance of said operational amplifier thereby determining the integrating time constant of said Miller integrator; d. level generator means for generating a signal having a predetermined level; and e. level comparator means for comparing the output of said Miller integrator means to said predetermined level and for generating an exposure finishing signal when the output of said Miller integrator reaches said predetErmined level.
Claim 3
Dependent Claim
18 words
The circuit as set forth in claim 1 wherein said first and second resistor means are variable resistances.
References Cited (Backward Citations)
US3504603A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-04 | 1977-08-06 | 1978-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-04 | 1981-08-06 | 1982-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-04 | 1985-08-06 | 1986-02-05 | $7700.00 | Window Closed / Lapsed |