US3761176A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic exposure control for copy machine
Assignee: 3M Co
•
Filing: 1971-07-27
•
Granted: 1973-09-25
•
Expires: 1991-07-27
Abstract
Abstract An automatic exposure control apparatus and method for a reflex photocopier including a light source and a diffuse reflector for reflecting light from the source uniformly onto a lighttransmissive photosensitive film in intimate contact with an original document. A sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document back through the film is continuously collected during each exposure cycle and each exposure cycle is controlled to maintain the integral of the intensity of the sample of light as a function of time constant over successive exposure cycles. The apparatus and method produce proper differential desensitization of the photosensitive film according to the differential reflectivity of the original document copied.
Inventors
- 👤 G Lewer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 08:42
CPC Classifications
G; G03; G03B; G03B27/00; G03B27/72; G03B27/80
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
134 words
In a photocopier including a light source and a diffuse reflector for reflecting light during an exposure cycle from the source uniformly onto a light-transmissive photosensitive film in intimate contact with an original document having image and nonimage areas providing a differential reflectivity to differentially desensitize the photosensitive film according to the differential reflectivity of the original document, an automatic exposure control comprising: means for collecting continuously during the exposure cycle a sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document, and means response to said means for collecting for controlling the exposure cycle to maintain the integral of the intensity of said sample of light as a function of time constant over successive exposure cycles.
Claim 2
Dependent Claim
134 words
In a photocopier including a light source and a diffuse reflector for reflecting light during an exposure cycle from the source uniformly onto a light-transmissive photosensitive film in intimate contact with an original document having image and nonimage areas providing a differential reflectivity to differentially desensitize the photosensitive film according to the differential reflectivity of the original document, an automatic exposure control comprising: means for collecting continuously during the exposure cycle a sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document, and means response to said means for collecting for controlling the exposure cycle to maintain the integral of the intensity of said sample of light as a function of time constant over successive exposure cycles.
Claim 3
Dependent Claim
153 words
In a photocopier including a light source and a diffuse reflector for reflecting light during an exposure cycle from the source uniformly onto a light-transmissive photosensitive film in contact with an original document having image and nonimage areas providing a differential reflectivity to differentially desensitize the photosensitive film according to the differential reflectivity of the original document, an automatic exposure control comprising: means for collecting continuously during the exposure cycle a sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document, means for integrating the intensity of said sample of light as a function of time, and means responsive to said means for integrating for controlling the exposure cycle to discontinue desensitization of the photosensitive film when the integral of the intensity of said sample of light as a function of time equals a predetermined value.
Claim 4
Dependent Claim
153 words
In a photocopier including a light source and a diffuse reflector for reflecting light during an exposure cycle from the source uniformly onto a light-transmissive photosensitive film in contact with an original document having image and nonimage areas providing a differential reflectivity to differentially desensitize the photosensitive film according to the differential reflectivity of the original document, an automatic exposure control comprising: means for collecting continuously during the exposure cycle a sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document, means for integrating the intensity of said sample of light as a function of time, and means responsive to said means for integrating for controlling the exposure cycle to discontinue desensitization of the photosensitive film when the integral of the intensity of said sample of light as a function of time equals a predetermined value.
Claim 5
Dependent Claim
77 words
A photocopier as defined in claim 2 wherein said collecting means comprises: a sensor chamber having an end surface and a tubular member extending from the end surface to an aperture in a portion of said reflector permitting passage of light from said reflector into said sensor chamber; and a photoelectric device positioned within said sensor chamber for producing an output signal the amplitude of which is directly proportional to the intensity of said sample of light.
Claim 6
Dependent Claim
57 words
A photocopier as defined in claim 3 wherein said integrating means and said controlling means comprise: integrating circuit means for providing an integration signal having an amplitude proportional to the integral of said photoelectric device output signal; and voltage sensing circuit means for providing a control signal in response to said integration signal reaching a predetermined level.
Claim 7
Dependent Claim
156 words
A photocopier as defined in claim 4 wherein: said photoelectric device is a phototransistor positioned within said sensor chamber in non-alignment with said light source and said aperture; said integrating circuit means comprises a capacitor and switch means, said switch means being adapted to enable a charge buildup on one plate of said capacitor only during exposure intervals to provide said integration signal at said one plate of said capacitor; and said voltage sensing circuit means is a programmable unijunction transistor having its anode lead connected to said one plate of said capacitor, having its gate lead connected to a source of positive potential of a predetermined reference level and having its cathode lead connected to an output resistor, said programmable unijunction transistor discharging said capacitor through said output resistor to produce said control signal when the charge buildup on said one plate of said capacitor causes said integration signal to exceed said predetermined reference level.
Claim 8
Dependent Claim
38 words
A photocopier as defined in claim 5 further comprising: means for varying said predetermined reference level of said source of positive potential to permit selection of said reference level according to the film speed of said photosensitive film.
Claim 9
Independent Claim
137 words
A method for controlling the exposure cycle time in a photocopier having a light source and a diffuse reflector for reflecting light during an exposure cycle from the source uniformly onto a light-transmissive photosensitive film in intimate contact with an original document having image and nonimage areas providing a differential reflectivity to differentially desensitize the photosensitize film according to the differential reflectivity of the original document, said method comprising the steps of: initiating the exposure cycle; collecting continuously during the exposure cycle a sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document; and controlling the exposure cycle to maintain the integral of the intensity of said sample of light as a function of time constant over successive exposure cycles.
Claim 10
Independent Claim
137 words
A method for controlling the exposure cycle time in a photocopier having a light source and a diffuse reflector for reflecting light during an exposure cycle from the source uniformly onto a light-transmissive photosensitive film in intimate contact with an original document having image and nonimage areas providing a differential reflectivity to differentially desensitize the photosensitize film according to the differential reflectivity of the original document, said method comprising the steps of: initiating the exposure cycle; collecting continuously during the exposure cycle a sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document; and controlling the exposure cycle to maintain the integral of the intensity of said sample of light as a function of time constant over successive exposure cycles.
Claim 11
Independent Claim
157 words
A method for controlling the exposure cycle time in a photocopier having a light source and an open reflector for reflecting light during an exposure cycle from the source uniformly onto a light-transmissive photosensitive film in intimate contact with an original document having image and nonimage areas providing a differential reflectivity to differentially desensitize the photosensitive film according to the differential reflectivity of the original document, said method comprising the steps of: initiating the exposure cycle; collecting continuously during the exposure cycle a sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document; integrating the intensity of said sample of light as a function of time; and interrupting reflection of light onto the photosensitive film to terminate the exposure cycle when the integral of the intensity of said sample of light as a function of time equals a predetermined value.
Claim 12
Independent Claim
157 words
A method for controlling the exposure cycle time in a photocopier having a light source and an open reflector for reflecting light during an exposure cycle from the source uniformly onto a light-transmissive photosensitive film in intimate contact with an original document having image and nonimage areas providing a differential reflectivity to differentially desensitize the photosensitive film according to the differential reflectivity of the original document, said method comprising the steps of: initiating the exposure cycle; collecting continuously during the exposure cycle a sample of light representative of the sum of the intensity of the light from the source and the intensity of the light reflected from the original document; integrating the intensity of said sample of light as a function of time; and interrupting reflection of light onto the photosensitive film to terminate the exposure cycle when the integral of the intensity of said sample of light as a function of time equals a predetermined value.
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) | 1976-09-24 | 1977-03-26 | 1977-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-24 | 1981-03-26 | 1981-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-24 | 1985-03-26 | 1985-09-25 | $7700.00 | Window Closed / Lapsed |