IMAGE FORMING APPARATUS AND CONTROL METHOD THEREOF

• US 20070242315A1
• Filed: 04/03/2007
• Published: 10/18/2007
• Est. Priority Date: 04/12/2006
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: SOBUE, Fumitaka
• Granted Patent: US 7,688,342 B2
• Time in Patent Office: Days
• US Class Current: 358/474
• CPC Class Codes: H04N 1/0473 in subscanning direction, e.g. picture start or line-to-line synchronisation
• CPC Class Codes: H04N 1/1135 for the main-scan only
• CPC Class Codes: H04N 1/12 using the sheet-feed movement or the medium-advance or the drum-rotation movement as the slow scanning component, e.g. arrangements for the main-scanningsheet-feed movement by translatory movement of a flat picture-bearing surface H04N1/1008; main-scanning using oscillating or rotating mirrors H04N1/113; using multi-element arrays H04N1/19
• CPC Class Codes: H04N 2201/0082 Image hardcopy reproducer H04N2201/0091 - H04N2201/0094 take precedence
• CPC Class Codes: H04N 2201/04713 Details of the detector arrangement, e.g. non-standard position, optical details H04N2201/04712 takes precedence
• CPC Class Codes: H04N 2201/04744 by detecting the scanned beam or a reference beam
• CPC Class Codes: H04N 2201/04787 by changing or controlling the addresses or values of pixels, e.g. in an array, in a memory, by interpolation
• CPC Class Codes: H04N 2201/04793 using stored control or compensation data, e.g. previously measured data

Abstract

An image forming apparatus includes a photosensitive member, a light source for which intervals between spots formed on the photosensitive member by respective beams emitted from a plurality of light-emitting portions are narrower than a predetermined resolution, and a rotating polygonal mirror having a plurality of mirror plane each of which deflects beams emitted from the light source while rotating. In particular, the image forming apparatus includes a selection unit which selects a light-emitting portion corresponding to a mirror plane used to deflect a beam from the light source, and a driving unit which drives the light source to emit a beam from the selected light-emitting portion.

Claims

1. An image forming apparatus, comprising

a photosensitive member;

a light source having a plurality of light-emitting portions, in which an interval between spots that are formed on said photosensitive member by respective beams emitted from a plurality of said light-emitting portions is narrower than a resolution of the image forming apparatus;

a rotating polygonal mirror having a plurality of mirror plane each of which deflects beams that are emitted from said light source while rotating;

a selection unit that selects said light-emitting portion corresponding to a mirror plane that is used to deflect a beam from said light source; and

a driving unit which drives said light source so as to emit a beam from said light-emitting portion that is selected.

2. The image forming apparatus according to claim 1, wherein said selection unit is adapted to select said light-emitting portion which is suitable for reducing position errors of the spots that are ascribable to an amount of plane tilt of the mirror plane.

3. The image forming apparatus according to claim 2, having:

a storage unit which stores an amount of plane tilt of each mirror plane of said rotating polygonal mirror; and

a mirror plane specifying unit which specifies the current mirror plane;

wherein said selection unit is adapted to read out from said storage unit an amount of plane tilt which corresponds to the current mirror plane that is specified, and select said light-emitting portion that is suitable for the amount of plane tilt that is read out.

4. The image forming apparatus according to claim 2, further having:

an amount of plane tilt detection unit which detects an amount of plane tilt of each mirror plane of said rotating polygonal mirror,

wherein said selection unit is adapted to select said light-emitting portion in accordance with the amount of plane tilt that is detected.

5. The image forming apparatus according to claim 4, wherein said amount of plane tilt detection unit includes:

a detection unit which outputs a detection signal when a beam that is emitted from said light source and deflected by the mirror plane is incident thereon; and

a determining unit which determines the amount of plane tilt in accordance with a pulse width of the detection signal.

6. The image forming apparatus according to claim 4,

wherein said driving unit is adapted to cause a beam to be emitted from only a single light-emitting portion among a plurality of said light-emitting portions when detecting the amount of plane tilt.

7. The image forming apparatus according to claim 6,

wherein said driving unit is adapted to cause a beam to be emitted from only a light-emitting portion that is positioned at the center among a plurality of said light-emitting portions when detecting the amount of plane tilt.

8. A method of controlling an image forming apparatus which comprises a photosensitive member which is photosensitive, a light source having a plurality of light-emitting portions in which an interval between spots that are formed on said photosensitive member by respective beams emitted from a plurality of said light-emitting portions is narrower than a resolution of the image forming apparatus, and a rotating polygonal mirror which deflects beams that are emitted from said light source while rotating;

the method comprising;

a step of selecting said light-emitting portion that is suitable for a current mirror plane that is used to deflect a beam from said light source among a plurality of mirror planes of said rotating polygonal mirror; and

a step of driving said light source so as to emit a beam from said light-emitting portion that is selected.

9. An exposure apparatus, comprising:

a light source having a plurality of light-emitting portions, in which an interval between spots that are formed on an exposure plane by respective beams emitted from a plurality of said light-emitting portions is narrower than a resolution of the exposure apparatus;

a rotating polygonal mirror having a plurality of mirror plane each of which deflects beams that are emitted from said light source while rotating;

a selection unit that selects said light-emitting portion corresponding to a mirror plane that is used to deflect a beam from said light source; and

a driving unit which drives said light source so as to emit a beam from said light-emitting portion that is selected.

10. A method of controlling an exposure apparatus which includes a light source having a plurality of light-emitting portions, in which an interval between spots-that are formed on an exposure plane by respective beams emitted from a plurality of said light-emitting portions is narrower than a resolution, and

a rotating polygonal mirror having a plurality of mirror plane each of which deflects beams that are emitted from said light source while rotating;

the method comprising;

a step of selecting said light-emitting portion corresponding to a mirror plane that is used to deflect a beam from said light source; and

a step of driving said light source so as to emit a beam from said light-emitting portion that is selected.