Photocopying – Projection printing and copying cameras – Combined with or convertible to a contact printer
Patent
1977-01-27
1979-12-04
Braun, Fred L.
Photocopying
Projection printing and copying cameras
Combined with or convertible to a contact printer
118647, 355 10, G03G 1500, G03G 1510
Patent
active
041769422
ABSTRACT:
A photoconductive drum is electrostatically charged and radiated with a light image of an original document to produce an electrostatic image. A toner substance is applied to the drum to produce a toner image which is transferred and fixed to a copy sheet. A bias electrode is provided adjacent to the drum during the toner development stage to which is applied a bias voltage selected to prevent application of toner to white or background areas of the electrostatic image. The bias voltage is produced as a function of the sensed electrostatic potential of the electrostatic image and is automatically limited to prevent image degradation and loss of density. To reproduce photographs or low contrast documents such as diazo copies, the bias voltage is limited to a lower value to increase the image density and prevent dark areas from appearing washed out. The light image intensity is increased for reproduction of documents having colored backgrounds so that the backgrounds will reproduce white.
REFERENCES:
patent: 3892481 (1975-07-01), Schaefer et al.
patent: 4021111 (1977-05-01), Kuroishi et al.
patent: 4035069 (1977-07-01), Yano
patent: 4050806 (1977-09-01), Miyakawa et al.
patent: 4087171 (1978-05-01), Yano
Kuroishi Shoji
Tatsumi Susumu
Braun Fred L.
Jordan Frank J.
Ricoh & Company, Ltd.
LandOfFree
Electrophotographic copying apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrophotographic copying apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrophotographic copying apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-89302