Recorders – Printing – dotting – or punching marker – Ink transfer support or moving means
Patent
1989-11-02
1991-06-04
Griffin, Donald A.
Recorders
Printing, dotting, or punching marker
Ink transfer support or moving means
358298, G01D 942, G01D 1514
Patent
active
050218077
ABSTRACT:
An electrophotographic printing apparatus capable of printing continous half-tone images comprises a photoconductive element on which a latent image is to be formed, a laser light beam light source for projecting a beam spot on the photoconductive element, and a driving circuit connected to the laser beam light source for varying the power output of the laser beam light source. The photoconductive element is a digital photoconductive member that is characterized by undergoing a transistion from a first substantially constant surface potential to a second substantially constant surface potential only in regions where it is illuminated by light above a predetermined threshold level. A density filter is interposed between the laser beam light source and the photoconductive element so that the beam spot projected onto the photoconductive element has a predetermined light intensity distribution with the light intensity being highest near the central portion of the beam spot and rapidly decreasing away from the central portion. Because of the unique properties of the photoconductive element, only those portions of the beam spot which have a light intensity above the threshold level will form a latent image spot corresponding to the beam spot. Although the beam spot may be fixed in size, the size of the latent image spot may be varied by changing the power output of the laser beam light source, which enables printing of continuous half-tones.
REFERENCES:
patent: 3982253 (1976-09-01), Goshima et al.
patent: 4251821 (1981-02-01), Kimura
patent: 4347523 (1982-08-01), Ohara
patent: 4375063 (1983-02-01), Kitamura
patent: 4768043 (1988-08-01), Saito et al.
patent: 4812861 (1989-03-01), Sasaki et al.
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