US 7,071,957 B2Granted

Image forming apparatus and color-misregistration correcting method

AssigneeCanon Kabushiki Kaisha

InventorAkihiro Fujimoto

Life of this patent

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Abstract

To provide an image forming apparatus having a plurality of optical systems each simultaneously scanning two stations by one polygon mirror to minimize conveyance-directional color misregistration of an intermediate transferring belt. An electrophotographic color laser printer connected with a host computer is provided with a scanner unit common to first and second stations, a scanner unit common to third and fourth stations, and a registration-position detector for reading an image pattern formed on an intermediate transferring belt and detecting a registration position of an image of a laser beam. The plane phase of the polygon mirror in the first and second stations is controlled and central positions of image patterns by two laser beams are detected to correct the misregistration between these central positions.

Claims12

Dependent claims

An image forming apparatus comprising:

a first optical system comprising a first light beam generator, a second light beam generator, and a first scanner adapted to scan a first photosensitive member with a light beam from said first light beam generator to form a first color image on the first photosensitive member and to scan a second photosensitive member with a light beam from said second light beam generator to form a second color image on the second photosensitive member;
a second optical system comprising a third light beam generator, a fourth light beam generator, and a second scanner adapted to scan a third photosensitive member with a light beam from said third light beam generator to form a third color image on the third photosensitive member and to scan a fourth photosensitive member with a light beam from said fourth light beam generator to form a fourth color image on the fourth photosensitive member;
a transfer unit adapted to transfer images formed on each photosensitive member to a common transfer medium;
a control unit adapted to control each of said light beam generators to form a pattern for correcting a color mis-registration;
a position detector capable of detecting a position in a conveyance direction of patterns formed by each of the light beam generators, even where the position is less than one scan line;
and
a correcting unit adapted to correct a color mis-registration whose magnitude is less than one scan line in a conveyance direction by adjusting a relational phase of said first scanner and said second scanner according to detection results of said position detector.

4 more elements

A method for correcting a color mis-registration in an image forming apparatus that includes a first optical system comprising a first light beam generator, a second light beam generator, and a first scanner adapted to scan a first photosensitive member with a light beams from the first light beam generator to form a first color image on the first photosensitive member and to scan a second photosensitive member with a light beam from the second light beam generator to form a second color image on the second photosensitive member;

a second optical system comprising a third light beam generator, a fourth light beam generator, and a second scanner adapted to scan a third photosensitive member with a light beam from the third beam generator to form a third color image on the third photosensitive member and to scan a fourth photosensitive member with a light beam from the fourth light beam generator to form a fourth color image on the fourth photosensitive member;
and a transfer unit adapted to transfer images formed on each photosensitive member to a common transfer medium, said method comprising the steps of:
controlling each of the light beam generators to form a pattern for correcting a color mis-registration;
detecting, using a position detector, a position in a conveyance direction of patterns formed by respective ones of the light beam generators, even where the position is less than one scan line;
and
correcting a color mis-registration whose magnitude is less than one scan line in the conveyance direction by adjusting a relational phase of the first scanner and the second scanner according to detection results obtained in said detecting step.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/245,648Filed 18 Sep 2002
Priority: JP 2001-28698720 Sep 2001
Published: US 2003/0052959 A120 Mar 2003
Granted: 4 Jul 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification21 codes

H04N 1/506
Picture reproducers: reproducing the colour component signals picture-sequentially, e.g. with reproducing heads spaced apart from one another in…
G02B 26/123
Using multifaceted mirrors: multibeam scanners, e.g. using multiple light sources or beam splitters
G03G 15/011
Details of unit: for exposing
G03G 15/0194
Using more than one reusable electrographic recording member, e.g. one for every monocolour image: primary transfer to the final recording medium