US3609038A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electronic control apparatus
Assignee: Unisys Corp
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Filing: 1970-03-09
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Granted: 1971-09-28
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Expires: 1990-03-09
Abstract
Abstract An electronic system for controlling light source intensity in document copying apparatus. Illumination for a photographic process is automatically varied in accordance with relative reflectivity characteristics of documents being advanced through the apparatus. A photoelectric device senses the amount of light energy reflected from such documents and this information is coupled to a circuit adapted to control energization of the illuminating lamps. The coupling circuitry includes an electronic switching device operatively connected to the output of a square wave generator having a duty cycle dynamically adjusted for modulating power to the lamps.
Inventors
- 👤 Hajo A Kolshorn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:39
CPC Classifications
H; H05; H05B; H05B39/00; H05B39/04; H05B39/041; H05B39/042; G; G03; G03B; G03B27/00; G03B27/32; G03B27/50; G03B27/72; G03B27/80; Y; Y02; Y02B; Y02B20/00
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
174 words
A photographic reproducing device comprising A. transport means for sequentially feeding documents along a predetermined path to a photograph station. B. camera means associated with said photograph station for photograpHing said documents upon arrival at said photograph station, C. a light source for illuminating said documents prior to arrival at and during travel through said photograph station, D. means for energizing said light source, E. Means for controlling said energizing means in accordance with the intensity of light energy reflected from said documents, said control means comprising, a. a photoelectric cell for sensing light reflected from said documents prior to travel through said photograph station, b. electronic switching means connected in circuit with said energizing means and said light source for selectively permitting appropriate current flow through said source, c. oscillator means connected to said switching means for alternately biasing said switching means to on and off conditions, and d. means coupling said cell to said oscillator for varying the duty cycle of said oscillator in response to the light sensed by said cell.
Claim 2
Dependent Claim
174 words
A photographic reproducing device comprising A. transport means for sequentially feeding documents along a predetermined path to a photograph station. B. camera means associated with said photograph station for photograpHing said documents upon arrival at said photograph station, C. a light source for illuminating said documents prior to arrival at and during travel through said photograph station, D. means for energizing said light source, E. Means for controlling said energizing means in accordance with the intensity of light energy reflected from said documents, said control means comprising, a. a photoelectric cell for sensing light reflected from said documents prior to travel through said photograph station, b. electronic switching means connected in circuit with said energizing means and said light source for selectively permitting appropriate current flow through said source, c. oscillator means connected to said switching means for alternately biasing said switching means to on and off conditions, and d. means coupling said cell to said oscillator for varying the duty cycle of said oscillator in response to the light sensed by said cell.
Claim 3
Dependent Claim
88 words
A photographic reproducing device as set forth in claim 1 wherein said oscillator means comprise an electronic circuit having input and output terminals, said input terminals coupled to said photoelectric cell, said output terminals connected to said switching means, and said circuit adapted to develop potential at said output terminals in the form of a square wave for which the duty cycle varies in accordance with the signal at said input terminals, which signal varies in response to the intensity of the light impinging on said photoelectric cell.
Claim 4
Dependent Claim
20 words
A photographic reproducing device as set forth in claim 2 wherein said oscillator operates at a frequency of 1,000 Hertz.
Claim 5
Dependent Claim
77 words
A photographic reproducing device as set forth in claim 2 wherein said electronic switching means comprise at least one transistor having base, collector and emitter terminals, said base and collector terminals connected in series with said light source and said energizing means, and means for coupling said base terminal to said oscillator output to effect switching of said one transistor from off to saturation in response to the high and low portions of said square wave output.
Claim 6
Dependent Claim
35 words
A photographic reproducing device as set forth in claim 2 wherein said photoelectric cell comprises one leg of an impedance bridge circuit, the output of which is coupled to said input terminals of said oscillator.
Claim 7
Dependent Claim
77 words
A photographic reproducing device as set forth in claim 5 wherein said electronic switching means comprise at least one transistor having base, collector and emitter terminals, said base and collector terminals connected in series with said light source and said energizing means, and means for coupling said base terminal to said oscillator output to effect switching of said one transistor from off to saturation in response to the high and low portions of said square wave output.
Claim 8
Dependent Claim
41 words
A photographic reproducing device as set forth in claim 2 wherein said electronic circuit comprises a multivibrator, and a differential amplifier operatively connected between the multivibrator and said input terminals to regulate said multivibrator in accordance with the relative potential thereat.
Claim 9
Dependent Claim
78 words
A photographic reproducing device as set forth in claim 7 wherein said photoelectric cell comprises one leg of an impedance bridge circuit having output terminals connected to said differential amplifier via said oscillator input terminals for varying the input to said multivibrator to effectively change the duty cycle of the oscillator in response to the variation of sensed light, whereby the duty cycle is dynamically adjusted until an equilibrium condition exists as a function of relative document reflectivity.
Claim 10
Dependent Claim
49 words
A photographic reproducing device as set forth in claim 5 and wherein said bridge circuit includes two output terminals, one of which is connected to a corresponding input terminal of said oscillator, the other of which is connected to its corresponding input terminal of said oscillator by gating means.
Claim 11
Dependent Claim
82 words
A photographic reproducing device as set forth in claim 9 and further including a time delay circuit and an electronic document switch for sensing the leading and trailing edge of said documents being fed to said photographic station, and wherein said gating means comprise a switch responsive to a signal originating at said electronic document switch and delayed by said time delay for a predetermined time interval corresponding to a known excursion of document travel prior to entry into said photograph station.
References Cited (Backward Citations)
US3279312A
Cited
US3492071A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-09-27 | 1975-03-29 | 1975-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-09-27 | 1979-03-29 | 1979-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-09-27 | 1983-03-29 | 1983-09-28 | $7700.00 | Window Closed / Lapsed |