US 2008/0166140 A1Published application

Image forming apparatus and control method thereof having main scan length correcting feature

AssigneeCanon Kabushiki Kaisha

InventorJunichi NOGUCHI

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Abstract

To detect differences in the main-scanning length of each beam on a photosensitive member, patterns for correction are formed on the photosensitive member using only beams (L1, LN) at both ends among a plurality of beams aligned in a sub-scanning direction. The patterns are transferred onto an intermediate transfer belt and detected with photosensors, a difference ΔLN of scanning length between a 1-st line and a N-th line is calculated, and a difference ΔLi of scanning length of a i-th line is calculated by ΔLi=ΔLN×(i/N−1) so as to proportionally distribute ΔLN to the i-th line. The scanning lengths of lines are respectively corrected to be equal each other using the obtained differences ΔLi of scanning length. Thus, an image forming apparatus and a control method that reduce a decline in image quality, even when scanning incident angles of laser beams onto a photosensitive member differ for each of beams on forming images by scanning a multiple lines with a multiple beams, can be provided.

Claims4

Dependent claims

An image forming apparatus for forming an image by scanning on a photosensitive member in a main-scanning direction with a plurality of beams aligned in a sub-scanning direction, comprising:

an emitting unit adapted to emit the plurality of beams including a first beam from a first light source, a second beam from a second light source and a third beam from a third light source arranged between the first and second light sources;
a detection unit adapted to detect a first location in which a first test pattern is formed by the first beam emitted from the first light source and a second location in which a second test pattern is formed by the second beam emitted from the second light source;
a determination unit adapted to, based on a detection result by said detection unit, determine positions of a first pixel and a last pixel in the main scanning direction on the photosensitive member to be formed by the second beam, and positions of a first pixel and a last pixel in the main scanning direction on the photosensitive member to be formed by the third beam,
wherein said determination unit determines the positions of a first pixel and a last pixel in the main scanning direction on the photosensitive member to be formed by the second beam based on the first and second locations detected by said detection unit, and the positions of a first pixel and a last pixel in the main scanning direction on the photosensitive member to be formed by the third beam based on the first and second locations detected by said detection unit without forming a third test pattern by the third beam emitted from the third light source.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 12/047,965Filed 13 Mar 2008
Priority: JP 2005-26769414 Sep 2005
Published: 10 Jul 2008
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

B41J 29/393
Drives, motors, controls or automatic cut-off devices for the entire printing mechanism: devices for controlling or analysing the entire machine ;…
G03G 15/04
Apparatus for electrographic processes using a charge pattern: for exposing, i.e. imagewise exposure by optically projecting the original image on…
G03G 15/0435
With means for controlling illumination or exposure: by introducing an optical element in the optical path, e.g. a filter
B41J
Typewriters

Family

Application11/531,731Continuation · filed 14 Sep 2006
Application12/047,965Continuation
US 2007/0057989 A1Published application
US 7,382,390 B2Related patent
US 7,652,684 B2Related patent
US 2008/0166140 A1This patent

From the US filing history. Foreign family members aren’t listed.