US4035069A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Exposure and development system for electrophotography
Assignee: Ricoh Co Ltd
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Filing: 1975-07-08
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Granted: 1977-07-12
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Expires: 1995-07-08
Abstract
Abstract In order to improve the reproduction of low contrast originals, the exposure intensity is reduced to a value at which the difference in brightness of the light and dark areas of the original will produce a maximum difference in electric potential on a photoconductive drum. The voltage applied to a developing electrode is increased to prevent darkening of the light areas of the copy.
Inventors
- 👤 Takashi Yano
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:42
CPC Classifications
G; G03; G03G; G03G15/00; G03G15/04; G03G15/043; G03G15/06; G03G15/065
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
161 words
A method of electrophotographically duplicating an original document having either normal or low contrast including the steps of radiating a light image of an original document of normal contrast with a first predetermined intensity onto a photoconductive member to form an electrostatic image, developing the electrostatic image using a developing electrode disposed adjacent to the photoconductive member, and a first predetermined voltage being applied to the developing electrode when duplicating an original document having normal contrast, the improvement comprising the steps, when duplicating an original document having low contrast, of: (a) adjusting the light image to have a second predetermined intensity which is lower than the first predetermined intensity, the second predetermined intensity being that at which the rate of change of photoconductivity of the photoconductive member with respect to a change in the intensity of the light image is substantially maximum; and (b) applying a second predetermined voltage which is higher than the first predetermined voltage to the developing electrode.
Claim 2
Independent Claim
161 words
A method of electrophotographically duplicating an original document having either normal or low contrast including the steps of radiating a light image of an original document of normal contrast with a first predetermined intensity onto a photoconductive member to form an electrostatic image, developing the electrostatic image using a developing electrode disposed adjacent to the photoconductive member, and a first predetermined voltage being applied to the developing electrode when duplicating an original document having normal contrast, the improvement comprising the steps, when duplicating an original document having low contrast, of: (a) adjusting the light image to have a second predetermined intensity which is lower than the first predetermined intensity, the second predetermined intensity being that at which the rate of change of photoconductivity of the photoconductive member with respect to a change in the intensity of the light image is substantially maximum; and (b) applying a second predetermined voltage which is higher than the first predetermined voltage to the developing electrode.
Claim 3
Dependent Claim
28 words
The method according to claim 1, in which the light image has dark areas and light areas, the second predetermined intensity being the intensity of the dark areas.
Claim 4
Dependent Claim
29 words
The method according to claim 1, in which the second predetermined voltage is a predetermined function of the second predetermined intensity and the photoconductivity characteristic of the photoconductive member.
Claim 5
Dependent Claim
26 words
The method according to claim 2, in which the second predetermined voltage is substantially equal to a voltage corresponding to the intensity of the light areas.
Claim 6
Dependent Claim
151 words
Electrophotographic apparatus comprising: a photoconductive member; a developing electrode disposed adjacent to the photoconductive member; imaging means for radiating a light image of a document onto the photoconductive member; electric source means for applying an electric voltage to the developing electrode; and control means operative to control the imaging means to adjust the light image to a first predetermined intensity when duplicating documents of normal contrast and to adjust the light image to a second predetermined intensity which is lower than the first predetermined intensity when duplicating documents of low contrast and to control the electric source means to apply a first predetermined voltage to the developing electrode when duplicating documents of normal contrast and to apply a second predetermined voltage to the developing electrode which is higher than the first predetermined voltage when duplicating documents of low contrast, said control means comprising switch means for controlling the electric source means.
Claim 7
Dependent Claim
151 words
Electrophotographic apparatus comprising: a photoconductive member; a developing electrode disposed adjacent to the photoconductive member; imaging means for radiating a light image of a document onto the photoconductive member; electric source means for applying an electric voltage to the developing electrode; and control means operative to control the imaging means to adjust the light image to a first predetermined intensity when duplicating documents of normal contrast and to adjust the light image to a second predetermined intensity which is lower than the first predetermined intensity when duplicating documents of low contrast and to control the electric source means to apply a first predetermined voltage to the developing electrode when duplicating documents of normal contrast and to apply a second predetermined voltage to the developing electrode which is higher than the first predetermined voltage when duplicating documents of low contrast, said control means comprising switch means for controlling the electric source means.
Claim 8
Dependent Claim
20 words
The apparatus according to claim 5, in which the control means comprises light value means for controlling the imaging means.
Claim 9
Dependent Claim
24 words
The apparatus according to claim 5, in which the control means comprises means for controlling the imaging means independently of the electric source means.
Claim 10
Dependent Claim
24 words
The apparatus according to claim 5, in which the control meams comprises means for controlling the electric source means independently of the imaging means.
Claim 11
Dependent Claim
23 words
The apparatus according to claim 5, in which the control means comprises means for integrally controlling the imaging means and electric source means.
Claim 12
Dependent Claim
34 words
The apparatus according to claim 5, in which the control means comprises a light valve for controlling the imaging means, and a control member for integrally controlling the light valve and the switch means.
Claim 13
Dependent Claim
31 words
The apparatus according to claim 5, in which the electric source means is constituted by the photoconductive member, a self-bias voltage being induced on the developing electrode by the photoconductive member.
Claim 14
Dependent Claim
29 words
The apparatus according to claim 5, in which the second predetermined voltage is a predetermined function of the second predetermined intensity and the photoconductivity characteristic of the photoconductive member.
Claim 15
Dependent Claim
35 words
The apparatus according to claim 12, in which the light image has light areas and dark areas, the second predetermined voltage being substantially equal to a voltage corresponding to the intensity of the light areas.
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) | 1980-07-11 | 1981-01-10 | 1981-07-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-07-11 | 1985-01-10 | 1985-07-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-07-11 | 1989-01-10 | 1989-07-12 | $7700.00 | Window Closed / Lapsed |