US 4,304,486 AGranted

Automatic bias and registration control system for electrophotographic copier

AssigneeNashua Corporation

InventorsRaymond G. Cormier, Austin E. Davis, Richard A. Bridges, John H. Williams

Life of this patent

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Abstract

In an optical imaging system for an electrophotographic copier, a photodetector intercepts a portion of unfocused light being reflected toward the photoconductive surface. An electronic circuit generates a biasing voltage for the copier development electrode which varies with the amount of light incident on the photodetector a set time after the photodetector receives a distinctively intense light pulse reflected from a high-reflectivity strip positioned ahead of the document being copied. The time delay insures that the light which determines the bias voltage has been reflected from the main body of the document. The light pulse from the high reflectivity strip can also independently actuate the copy paper feed mechanism to insure proper image registration.

Claims13

Dependent claims

In an electrophotographic copier in which the image of a document is optically produced on a photoconductive surface, said copier having

an optical imaging assembly for focusing light from a document illumination source and reflected from said document onto said photoconductive surface,
means for moving at least one of said illumination source and said document for illuminating progressively said document;
a development station wherein a development electrode is closely spaced to the photoconductive surface,
a transfer station including means for positioning a copy medium adjacent said photoconductive surface for transfer of the image thereon, and
apparatus for generating and applying an electrical potential to said electrode, said apparatus comprising:
a photoelectric detector disposed to intercept an unfocused portion of the light energy reflected from said document toward said photoconductive surface, and for generating an output signal in response thereto;
means for determining when said reflected light energy corresponds to scanning of a central portion of said document, and
a signal generating means responsive to said output of said detector and said determining means for generating an electrical potential to be applied to said development electrode,
whereby the magnitude of said potential is dependent on the light energy received by said photoelectric detector from said central portion of the document relative to a predetermined standard reflectivity value.

6 more elements

In an electrophotographic copier in which the image of a document supported on a document plate is optically produced on a photoconductive surface, said copier having

an optical imaging assembly for focusing light reflected from said document onto said photoconductive surface,
a development station wherein a development electrode is closely spaced to the photoconductive surface,
a transfer station including means for positioning a copy medium adjacent said photoconductive surface for transfer of the image thereon, and
apparatus for generating and applying an electrical potential to said electrode and for generating an electrical control signal for said copy medium positioning means, said apparatus comprising:
a reflective member, disposed adjacent a leading edge of said document plate, said member having a predetermined high reflectivity in a known spectral bandwidth;
a light source;
means for moving one of said light source and said document plate for illuminating progressively said reflective member and said document;
a photoelectric detector responsive to at least a portion of said light source output and disposed to intercept an unfocused portion of the light energy reflected by said reflective member and said document toward a focusing lens, for generating an output signal in response thereto;
and
a signal generating means
responsive to the output of said detector which exceeds a first threshold for generating a first timing signal for actuating said copy medium positioning means, and
responsive to the output of said detector at a predetermined time after generation of said first timing signal for generating said electrical potential to be applied to said development electrode,
whereby said detector output which exceeds said first threshold corresponds to light energy reflected by said reflective member.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/086,749Filed 22 Oct 1979
Granted: 8 Dec 1981
Term ends: Not estimatedThe source records don’t support an estimate.

Classification13 codes

G03G 15/6532
Apparatus which relate to the handling of copy material: removing a copy sheet form a xerographic drum, band or plate
B65H 1/04
Supports or magazines for piles from which articles are to be separated: adapted to support articles substantially horizontally, e.g. for…
B65H 1/12
With means for advancing the articles to present the articles to the separating device: comprising spring
B65H 29/56
Article strippers, e.g. for stripping from advancing elements: for stripping from elements or machines