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Multi-beam scanning optical apparatus and image forming apparatus using it

Imported: 23 Feb '17 | Published: 22 Oct '02

Manabu Kato

USPTO - Utility Patents

Abstract

Provided are a multi-beam scanning optical apparatus capable of realizing compactification of a synchronism-detecting optical system and high-accuracy synchronism detection based on prevention of spatial overlap between spots, and an image forming apparatus using it. The multi-beam scanning optical apparatus is constructed in such structure that a plurality of beams independently optically modulated and emitted from a light source having a plurality of light emission points placed with a spacing in the main scanning direction are focused in a spot shape on a surface to be scanned, via a deflecting element by a scanning optical element, the plurality of beams scan an area on the surface to be scanned, part of the plurality of beams via the deflecting element are converged in a spot shape at a synchronism detection position and thereafter guided onto a surface of a synchronism detecting element, and timing of scan start position on the surface to be scanned is controlled for each of the plurality of beams by use of a signal from the synchronism detecting element; wherein a spot spacing in the main scanning direction between adjacent beams at the synchronism detection position is smaller than a spot spacing in the main scanning direction between adjacent beams on the surface to be scanned.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of Embodiment 1, of the present invention in the main scanning direction;

FIG. 1B is a depiction of the positioning of light emission points on a light source according to one embodiment of the invention;

FIG. 2 is a cross-sectional view of Embodiment 2 of the present invention in the main scanning direction;

FIG. 3 is a cross-sectional view of Embodiment 3 of the present invention in the main scanning direction;

FIG. 4 is a diagram to show an intensity distribution of a Fraunhofer diffraction image of a circular aperture;

FIG. 5A is a diagram to show separation of spots at the synchronism detection position in Embodiment 3 of the present invention, and FIG. 5B is an enlarged view thereof;

FIG. 6 is a cross-sectional view of the optical system of the conventional scanning optical apparatus in the main scanning direction;

FIG. 7 is a diagram to show separation of spots at the synchronism detection position; and

FIG. 8 is a schematic diagram of an image forming apparatus of the present invention.

Claims

1. A multi-beam scanning optical apparatus comprising:

2. A multi-beam scanning optical apparatus comprising:

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SC<1.0,

3. The multi-beam scanning optical apparatus according to claim 2, wherein said synchronism detector controls the timing of the scan start position on the surface to be scanned for each of the plurality of beams emitted from said light source.

4. The multi-beam scanning optical apparatus according to claim 2, wherein the synchronism-detecting optical element is an anamorphic lens.

5. The multi-beam scanning optical apparatus according to claim 2, wherein the synchronism-detecting optical element is made of a plastic material.

6. The multi-beam scanning optical apparatus according to claim 2, wherein said scanning optical element is made of a plastic material.

7. The multi-beam scanning optical apparatus according to claim 2, wherein the synchronism-detecting optical element and at least one optical element forming said scanning optical element are integrally molded by plastic injection molding.

8. The multi-beam scanning optical apparatus according to claim 2, further comprising a second optical element for guiding the plurality of beams emitted from said light source toward said deflecting element, wherein the synchronism-detecting optical element and said second optical element are integrally molded by plastic injection molding.

9. The multi-beam scanning optical apparatus according to claim 2, wherein said scanning optical element comprises a refracting optical element and a diffracting optical element.

10. The multi-beam scanning optical apparatus according to claim 2, wherein said synchronism detector is constructed in a plane of reflective deflection effected by said deflecting element.

11. An image forming apparatus comprising:

12. A multi-beam scanning optical apparatus comprising:

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BD

/f

SC<1.0,

Fmi<L/(6.656×)×

f

BD

/f

SC,

13. The multi-beam scanning optical apparatus according to claim 12, wherein said synchronism detector controls the timing of the scan start position on the surface to be scanned for each of the plurality of beams emitted from said light source.

14. The multi-beam scanning optical apparatus according to claim 12, wherein the synchronism-detecting optical element is an anamorphic lens.

15. The multi-beam scanning optical apparatus according to claim 12, wherein the synchronism-detecting optical element is made of a plastic material.

16. The multi-beam scanning optical apparatus according to claim 12, wherein said scanning optical element is made of a plastic material.

17. The multi-beam scanning optical apparatus according to claim 12, wherein the sychronism-detecting optical element and at least one optical element forming said scanning optical element are integrally molded by plastic injection molding.

18. The multi-beam scanning optical apparatus according to claim 12, further comprising:

19. The multi-beam scanning optical apparatus according to claim 12, wherein said scanning optical element comprises a refracting optical element and a diffracting optical element.

20. The multi-beam scanning optical apparatus according to claim 12, wherein said synchronism detector is constructed in a plane of reflective deflection effected by said deflecting element.

21. An image forming apparatus comprising: