US 6,188,419 B1Granted

color image-forming device

AssigneeSharp Kabushiki Kaisha

InventorsKoji Katamoto, Osamu Fujimoto, Ayumu Oda, Syoichiro Yoshiura, Yoichi Shimazawa

Life of this patent

Estimating the term…

Loading patent…

Abstract

In conventional color digital copy machines, when copying in color mode, the polygon mirror of the laser beam scanner for black, which is driven at a higher speed than those of the other colors, is switched to a slower speed in conformity with the speed of the polygon mirrors for the other colors. However, a drawback of this structure is that, especially when switching from monochrome to color mode, the time required to obtain the first copy is lengthened, and the operating efficiency of copying is poor. In the present invention, when copying in color mode, the rotation speed of the polygon mirror of the laser scanner unit for black is not changed at all, but, by skipping certain mirror surfaces of the polygon mirror, and/or by skipping certain of a plurality of laser light sources, the scanning density of the laser scanner unit for black can be brought into conformity with that of the laser scanner units for the other colors.

Claims29

Dependent claims

A color image-forming device comprising:

an image-forming section, provided with a recording section for color image formation and a recording section for monochrome image formation, each of which performs optical scanning of a photoreceptor by using a rotating polygon having a reflective mirror on at least one surface thereof to guide to said photoreceptor light modulated in accordance with image information;
said image-forming section forming an electrostatic latent image on said photoreceptor by light scanning, the electrostatic image corresponding to said image information, and forming an image from the electrostatic image;
and
process speed switching means, which switches a process speed of said image-forming section such that said process speed is faster during monochrome image formation than during color image formation;
said recording section for monochrome image formation being provided with a first scanning mode, which corresponds to a high process speed, and a second scanning mode, which corresponds to a low process speed, and which performs scanning with a scanning density equivalent to that of the said recording section for color image formation, without changing rotation speed of said rotating polygon having a reflective mirror on at least one surface thereof.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/135,473Filed 17 Aug 1998
Priority: JP 9-22182118 Aug 1997
Granted: 13 Feb 2001
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

H04N 1/233
Circuits or arrangements for the control thereof, e.g. using a programmed control device, according to a measured quantity: according to…
H04N 1/2307
Reproducing arrangements: circuits or arrangements for the control thereof, e.g. using a programmed control device, according to a measured quantity
H04N 1/2369
Circuits or arrangements for the control thereof, e.g. using a programmed control device, according to a measured quantity: selecting a particular…
H04N 1/46
Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof: colour picture communication systems