LASER SCANNING OPTICAL SYSTEM AND IMAGE FORMING APPARATUS

Abstract

A laser scanning optical system converts a plurality of beams emitted from the laser diode (LD) into parallel light using a collimator lens, shapes the parallel light using an aperture, and executes exposure of a plurality of lines simultaneously on a photoreceptor drum. To cause a necessary emitting point interval d determined uniquely from the magnification of the optical system to coincide with an emitting point interval of the LD used, the LD is rotated by an angle θ against the main optical axis plane thereof. In this case, a converting device that converts the aspect ratio of a profile of the light beam emitted from the LD is provided. A conversion characteristic of the converting device is adjusted such that the characteristic is matched with a condition within a predetermined region following a characteristic of the optical system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an embodiment of an image forming apparatus of the present invention;

FIGS. 2A and 2B are explanatory views of states of a light beam of each color in a primary optical system and a secondary optical system;

FIG. 3 is an explanatory view of an optical system configured by two lenses;

FIG. 4 is an explanatory view of a cross-sectional profile of a laser beam of an edge emitting laser diode;

FIGS. 5A and 5B are explanatory views of a configuration example and functions of a converting device;

FIG. 6 is an explanatory schematic view of a configuration example of a laser light source using a plurality of laser diodes each having a single emitting point;

FIG. 7 depicts an example of the simulation result in an optical system that converts a light beam emitted from a multi-emission LD into parallel light using a collimator lens and shapes the parallel light using an aperture;

FIG. 8 depicts a table that lists the calculation result of a focal length of a collimator lens necessary in the optical system for which simulation of FIG. 7 is executed;

FIG. 9 graphically depicts the relation between a conversion coefficient Δν and the focal length of the collimator lens obtained when the conversion coefficient Δ⊥ of FIG. 8 is fixed at one and a conversion coefficient Δ∥ is varied;

FIG. 10 diagrammatically depicts the emission profile of a laser light beam emitted from an edge emitting laser diode having one emission point;

FIG. 11 diagrammatically depicts the emission profile of a laser light beam emitted from an edge emitting laser diode having two emission points;

FIG. 12 diagrammatically depicts the relation between an aperture and an emission profile; and

FIG. 13 diagrammatically depicts the relation between one laser light beam and an aperture obtained when the laser diode is rotated.

Claims

1. A laser scanning optical system having a semiconductor laser, a collimator lens that converts a plurality of light beams emitted from the semiconductor laser into parallel light, and an aperture that defines a diameter of a spot of the light beam on an image carrier, and the system scanning the light beams emitted from the collimator lens and exposing simultaneously a plurality of lines on the image carrier, wherein the laser scanning optical system has a converting device that converts an aspect ratio of a profile of the light beam exited from the semiconductor laser, whereinthe converting device converts the plurality of light beams, and whereinwhen it is assumed that a main scanning direction is a beam scanning direction in the laser scanning optical system and a sub-scanning direction is a direction perpendicular to the main scanning direction,

2. The laser scanning optical system of claim 1, wherein the collimator lens functions as the converting device by having an anamorphic shape, converts the aspect ratio of the profile of the light beam emitted from the semiconductor laser, and converts the light beam into parallel light.

3. The laser scanning optical system of claim 2, wherein the collimator lens is adjusted to be at an inclination angle equal to an inclination angle θ of the semiconductor laser to adjust the pitch in the sub-scanning direction on the image carrier.

4. The laser scanning optical system of claim 1, wherein the converting device is provided on an optical path between the collimator lens and the semiconductor laser.

5. The laser scanning optical system of claim 1, wherein the converting device is provided on an optical path between the collimator lens and the aperture.

6. The laser scanning optical system of claim 4, wherein the converting device is adjusted to be at an inclination angle equal to an inclination angle of the semiconductor laser to adjust the pitch in the sub-scanning direction on the image carrier.

7. The laser scanning optical system of claim 5, wherein the converting device is adjusted to be at an inclination angle equal to an inclination angle of the semiconductor laser to adjust the pitch in the sub-scanning direction on the image carrier.

8. The laser scanning optical system of claim 1, wherein the plurality of light beams are emitted light beams by one semiconductor laser having a plurality of emitting points or by a plurality of semiconductor lasers each having one emitting point.

9. An image forming apparatus comprising: the laser scanning optical system of claim 1; anda photoreceptor, whereinthe laser scanning optical system forms a latent image on the photoreceptor, the latent image is visualized, and, thereby, image forming is executed.

10. An image forming apparatus comprising: the laser scanning optical system of claim 2; anda photoreceptor, whereinthe laser scanning optical system forms a latent image on the photoreceptor, the latent image is visualized, and, thereby, image forming is executed.

11. An image forming apparatus comprising: the laser scanning optical system of claim 3; anda photoreceptor, whereinthe laser scanning optical system forms a latent image on the photoreceptor, the latent image is visualized, and, thereby, image forming is executed.

12. An image forming apparatus comprising: the laser scanning optical system of claim 4; anda photoreceptor, whereinthe laser scanning optical system forms a latent image on the photoreceptor, the latent image is visualized, and, thereby, image forming is executed.

13. An image forming apparatus comprising: the laser scanning optical system of claim 5; anda photoreceptor, whereinthe laser scanning optical system forms a latent image on the photoreceptor, the latent image is visualized, and, thereby, image forming is executed.

14. An image forming apparatus comprising: the laser scanning optical system of claim 6; anda photoreceptor, whereinthe laser scanning optical system forms a latent image on the photoreceptor, the latent image is visualized, and, thereby, image forming is executed.

15. An image forming apparatus comprising: the laser scanning optical system of claim 7; anda photoreceptor, whereinthe laser scanning optical system forms a latent image on the photoreceptor, the latent image is visualized, and, thereby, image forming is executed.

16. An image forming apparatus comprising: the laser scanning optical system of claim 8; anda photoreceptor, whereinthe laser scanning optical system forms a latent image on the photoreceptor, the latent image is visualized, and, thereby, image forming is executed.