US3985440A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process and apparatus for automatic exposure time control in copying devices
Assignee: Hoechst AG
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Filing: 1976-01-07
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Granted: 1976-10-12
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Expires: 1996-01-07
Abstract
Abstract This invention relates to a process for automatic exposure time control in the exposure of light-sensitive copying material; comprising, photoelectrically measuring the illumination in the plane of the copying material, comparing the voltage produced by the photoelectric measuring means with a reference voltage, which is inversely proportional to time, during exposure, and terminating exposure when a predetermined difference between the two voltages is reached. The invention also includes an apparatus for performing the process.
Inventors
- 👤 Werner Dennhardt
- 👤 Herbert Schroter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 01:44
CPC Classifications
G; G03; G03B; G03B27/00; G03B27/72; G03B27/80
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
77 words
A process for automatic exposure time control in the exposure of light-sensitive copying material, comprising photoelectrically measuring the illumination in the plane of the copying material, generating during exposure a reference voltage U, which is inversely proportional to time T, U being equal to a constant divided by T, comparing said reference voltage during exposure with the voltage produced by the photoelectric measuring means, and terminating exposure when a predetermined difference between the two voltages is reached.
Claim 2
Dependent Claim
77 words
A process for automatic exposure time control in the exposure of light-sensitive copying material, comprising photoelectrically measuring the illumination in the plane of the copying material, generating during exposure a reference voltage U, which is inversely proportional to time T, U being equal to a constant divided by T, comparing said reference voltage during exposure with the voltage produced by the photoelectric measuring means, and terminating exposure when a predetermined difference between the two voltages is reached.
Claim 3
Dependent Claim
34 words
A process according to claim 1, wherein the variation of the reference voltage starts a predetermined interval after the beginning of exposure, which interval does not exceed the shortest exposure time occurring in practice.
Claim 4
Dependent Claim
16 words
A process according to claim 1, wherein exposure is terminated when the voltage difference is zero.
Claim 5
Dependent Claim
31 words
A process according to claim 1, wherein the variance of the reference voltage with time is delayed a predetermined period of time after the exposure of the copying material is begun.
Claim 6
Independent Claim
104 words
An apparatus for automatic time control of a unit for the exposure of light-sensitive copying material with a copying light source; comprising, a photoelectric transducer for photoelectrically measuring the illumination in the plane of the copying material, a time-controlled reference voltage unit for producing a reference voltage U inversely proportional to time T, U being equal to a constant divided by T, a comparator circuit connected to said reference voltage unit and said photoelectric transducer, and switch means for turning off said copying light source when a predetermined voltage difference between the voltage of said reference voltage unit and said photoelectric transducer is reached.
Claim 7
Independent Claim
104 words
An apparatus for automatic time control of a unit for the exposure of light-sensitive copying material with a copying light source; comprising, a photoelectric transducer for photoelectrically measuring the illumination in the plane of the copying material, a time-controlled reference voltage unit for producing a reference voltage U inversely proportional to time T, U being equal to a constant divided by T, a comparator circuit connected to said reference voltage unit and said photoelectric transducer, and switch means for turning off said copying light source when a predetermined voltage difference between the voltage of said reference voltage unit and said photoelectric transducer is reached.
Claim 8
Dependent Claim
48 words
An apparatus according to claim 5, wherein the time-controlled reference voltage unit includes a resistor having a constant resistance and a resistor having a resistance increasing linearly with time connected in series and the voltage at the ends of the constant resistor is used as the reference voltage.
Claim 9
Dependent Claim
29 words
An apparatus according to claim 5, wherein the time-controlled reference voltage unit includes time-delay means for delaying the variance of the voltage of said reference voltage unit with time.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-10-12 | 1980-04-12 | 1980-10-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-10-12 | 1984-04-12 | 1984-10-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-10-12 | 1988-04-12 | 1988-10-12 | $7700.00 | Window Closed / Lapsed |