OPTICAL SCANNING APPARATUS AND COLOR IMAGE FORMING APPARATUS USING THE SAME

Abstract

An optical scanning apparatus and a color image forming apparatus using the same, in which streak-shaped density unevenness is reduced to prevent image deterioration: each of scanning surfaces is simultaneously scanned with light beams emitted from light source units and scanning lines are simultaneously drawn on the scanning surfaces; the light beams emitted from at least four light emitting portions of the corresponding light source unit are simultaneously deflected for scanning by a deflecting unit; and image data corresponding to a first scanning line, i.e. a scanning line located on an uppermost stream side in a direction in which the scanning surfaces move among scanning lines, on at least one of the scanning surfaces in a k-th scanning by the deflecting unit is displaced by at least one line space from image data corresponding to a first scanning line on another scanning surface in the k-th scanning.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a relationship between image data and a laser beam in Embodiment 1 of the present invention.

FIG. 2 illustrates monolithic multi-beam semiconductor lasers.

FIG. 3 is a principal-part cross sectional diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention.

FIG. 4 illustrates a relationship between the image data and the laser beam in Embodiment 1 of the present invention.

FIG. 5 illustrates a vertical-cavity surface-emitting laser.

FIG. 6 is a principal-part perspective view illustrating the vertical-cavity surface-emitting laser.

FIG. 7 illustrates a galvano mirror.

FIG. 8 is a sub-scanning cross sectional diagram illustrating an optical scanning apparatus according to Embodiment 2 of the present invention.

FIG. 9 is a main scanning cross sectional diagram illustrating the optical scanning apparatus according to Embodiment 2 of the present invention.

FIG. 10 is a main scanning cross sectional diagram illustrating a comparative example of the optical scanning apparatus.

FIG. 11 is a sub-scanning cross sectional diagram illustrating another example of the optical scanning apparatus according to Embodiment 2 of the present invention.

FIG. 12 is a sub-scanning cross sectional diagram illustrating another example of the optical scanning apparatus according to Embodiment 2 of the present invention.

FIG. 13 is a sub-scanning cross sectional diagram illustrating an optical scanning apparatus according to Embodiment 3 of the present invention.

FIG. 14 is a sub-scanning cross sectional diagram illustrating an image forming apparatus according to Embodiment 4 of the present invention.

FIG. 15 is a schematic diagram illustrating an electric potential of an electrostatic latent image;

FIG. 16 illustrates registration marks.

FIG. 17 is a schematic diagram illustrating densities.

FIG. 18 is a principal-part schematic view illustrating a conventional optical scanning apparatus.

FIG. 19 illustrates an image outputted from a conventional image forming apparatus.

FIG. 20 illustrates another example of an image outputted from the conventional image-forming apparatus.

FIG. 21 illustrates a monolithic multi-beam semiconductor laser.

FIG. 22 illustrates another example of the monolithic multi-beam semiconductor laser.

Claims

1. An optical scanning apparatus, comprising: a plurality of light source unit, each of which includes four or more light source portions for radiating light beams which are optically modulated based on image data;a deflecting unit for deflecting the plurality of light beams emitted from each of the plurality of light source unit for scanning; andan imaging optical system for imaging the plurality of light beams which are deflected for scanning by a deflecting surface of the deflecting unit onto a plurality of surfaces to be scanned which are provided for the respective light source unit, in which each of the plurality of surfaces to be scanned is simultaneously scanned with the plurality of light beams emitted from corresponding one of the light source unit and a plurality of scanning lines are simultaneously drawn on each of the plurality of surfaces to be scanned,

2. An optical scanning apparatus according to claim 1, wherein in the k-th scanning operation of the deflecting unit, pieces of image data corresponding to first scanning lines on the surfaces to be scanned are displaced by at least one line space from one another.

3. An optical scanning apparatus according to claim 1, wherein a number of light emitting portions n1 of a light source unit which is provided corresponding to at least one of the plurality of surfaces to be scanned is different from the number of light emitting portions n2, where n1=n2×a and a is a positive integer, of at least another one of the light source unit which is provided corresponding to another one of the plurality of surfaces to be scanned.

4. An optical scanning apparatus according to claim 1, wherein the following equation is satisfied, D=(n×m+L)×p

5. An optical scanning apparatus according to claim 1, wherein the optical scanning apparatus comprises a plurality of the deflecting units andwherein the plurality of deflecting units is different from one another in deflection phases in the k-th scanning operation of the deflecting unit.

6. An optical scanning apparatus according to claim 4, wherein the optical scanning apparatus comprises a plurality of the imaging optical systems,wherein each of the plurality of imaging optical systems includes an imaging optical element, andwherein the imaging optical elements included in the plurality of imaging optical systems are different from one another in shift amounts in a sub-scanning direction relative to optical axes of the imaging optical systems.

7. An optical scanning apparatus according to claim 4, further comprising a plurality of optical systems, wherein each of the plurality of imaging optical systems includes an optical element, andwherein the imaging optical elements included in the plurality of imaging optical systems are different from one another in tilt amounts having a rotating axis parallel to a main scanning direction.

8. An optical scanning apparatus according to claim 1, wherein the light source unit comprises a vertical-cavity surface-emitting laser including a plurality of light emitting portions.

9. An optical scanning apparatus according to claim 8, wherein the light source unit comprises the vertical-cavity surface-emitting laser including the plurality of light emitting portions which are two-dimensionally arranged.

10. A color image forming apparatus, comprising: the optical scanning apparatus according to claim 1;a plurality of photosensitive members located on the surfaces to be scanned;a plurality of developing devices for developing, as toner images, electrostatic latent images formed on the photosensitive members scanned with the light beams by the optical scanning apparatus;a transferring device for transferring the developed toner images to a material onto which an image is to be transferred; anda fixing device for fixing the transferred toner images to the material onto which an image is to be transferred.

11. A color image forming apparatus, comprising: the optical scanning apparatus according to claim 1; anda printer controller for converting code data input from an external device into an image signal, and inputting the image signal to the optical scanning apparatus.

12. A color image forming apparatus according to claim 10, further comprising an electric potential sensor for measuring electric potentials of the electrostatic latent images formed on the photosensitive members, wherein information of the electrostatic latent images corresponding to the plurality of scanning lines is read by the electric potential sensor and a displacement amount of image data in the optical scanning apparatus is determined based on a result obtained by the reading.

13. A color image forming apparatus according to claim 10, further comprising a position sensor for measuring positions of the developed toner images, wherein positional information of the plurality of scanning lines is read by the position sensor and a displacement amount of image data in the optical scanning apparatus is determined based on a result obtained by the reading.

14. A color image forming apparatus according to claim 10, further comprising a density sensor for measuring densities of the developed toner images corresponding to the plurality of scanning lines, wherein densities of the toner images are read by the density sensor and a displacement amount of image data in the optical scanning apparatus is determined based on a result obtained by the reading.