JP3082405B2 - Laser beam scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam scanning device having a folding mirror for reflecting a laser beam.

[0002]

2. Description of the Related Art Generally, a laser beam scanning device used for a laser beam printer, a facsimile or the like has a folding mirror for guiding a laser beam to a photosensitive surface. FIG. 4 is a diagram showing a configuration of a holding portion of a folding mirror in such a laser beam scanning device. The folding mirror 24 is installed on the base plate 21 of the laser beam scanning device via mirror blocks 22a and 22b. The folding mirror 24 installed on the mirror blocks 22a and 22b is fixed by pressing springs 23a and 23b.

[0003]

The laser beam scanning device having such a folding mirror is vibrated by a motor for rotating the polygon mirror and other external factors. As a result, the base plate 21 vibrates, and the vibration of the base plate 21
4 is transmitted. At this time, when the base plate 21 vibrates in the direction of arrow a in the figure, as shown in FIG. 5, the folding mirror 24 has a longer length in a direction parallel to the reflection surface than in a direction perpendicular to the reflection surface. It vibrates in a direction perpendicular to the reflection surface (the direction of arrow b in the figure). Due to this vibration, the position of the laser beam B reflected by the folding mirror 24 is changed. When the position of the laser beam B is changed, pitch unevenness occurs in an image formed on the photosensitive surface. In order to prevent the vibration of the folding mirror 24, it is conceivable to provide a highly rigid reinforcing member on the back surface of the folding mirror 24, but the number of parts increases,
Also, the number of assembling steps increases.

Accordingly, an object of the present invention is to provide a laser beam scanning device having a simple configuration and in which the position of a laser beam does not change even when subjected to vibration.

[0005]

According to the present invention, there is provided a laser beam scanning apparatus having a folding mirror for reflecting a laser beam, wherein the length of the first surface parallel to the reflection surface of the folding mirror is increased . When L1 is L1 and the length of the second surface perpendicular to the reflection surface of the folding mirror is L2, L1 ≦ L2 is satisfied , and the first surface and the second surface are satisfied.
Are held by a holding member .

[0006]

In the above construction, since the length of the second surface perpendicular to the reflecting surface of the reflecting mirror is equal to or longer than the length of the first surface parallel to the reflecting surface, the reflecting mirror is subject to vibration. Vibrates in the direction parallel to the reflecting surface when it is touched, but does not vibrate in the direction perpendicular to the reflecting surface.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 and FIG. 2 are diagrams showing a schematic configuration of a laser beam scanning device of the present embodiment. This laser beam scanning device is integrally unitized, and includes a semiconductor laser 11, a collimator lens 12, a cylindrical lens 13, a polygon mirror 15, a toric fθ lens 1
6. Folding mirrors 17, 18, 19 are provided. These folding mirrors 17, 18, and 19 are made of glass, and are held on the base plate of the unit via aluminum holding members 41, 42, and 43 in the same configuration as in FIG.

A laser beam B generated from a semiconductor laser 11 is collimated by a collimator lens 12. The collimated laser beam B is condensed in the sub-scanning direction near the deflection surface of the polygon mirror 15 by the cylindrical lens 13 having power in the sub-scanning direction. The laser beam B condensed near the deflection surface of the polygon mirror 15 is deflected by the polygon mirror 15 and travels to the toric fθ lens 16. The toric fθ lens 16 has different powers in the main scanning direction and the sub-scanning direction, and applies the laser beam B to the photosensitive drum 3.
Scan at a constant speed on zero. The laser beam B that has passed through the toric fθ lens 16 reaches the photosensitive drum 30 via folding mirrors 17, 18, and 19.

FIG. 3 is a diagram showing the configuration of the folding mirror in the present embodiment. Folding mirrors 17, 18, 1
9 has the same configuration, so here the folding mirror 1 is used.
Only 7 will be described. The folding mirror 17 has a length (hereinafter, referred to as a vertical thickness) of a second surface 17b perpendicular to the reflection surface.
L2 is formed so as to be longer than the length (hereinafter, referred to as surface thickness) L1 of the first surface 17a parallel to the reflection surface .
First, the first surface 17a and the second surface 17b
It is held on holding surfaces 41a and 41b. This wrap
When the holding member 41 vibrates in the direction of arrow a due to the vibration of the base plate of the unit, the mirror 17 vibrates in a direction parallel to the reflection surface (direction of arrow c in the figure). Accordingly, since the position of the laser beam B is not moved, pitch unevenness does not occur in the image formed on the photoconductor 30.

Table 1 shows the result of an experiment on the direction of vibration of the folding mirror 17 when the surface thickness L1 is 14 mm (constant) and the vertical thickness L2 is changed from 2 to 98 mm. According to this result, when the vertical thickness L2 is less than 14 mm, the turning mirror 17 vibrates in a direction perpendicular to the reflection surface (the direction of the arrow b). On the other hand, the vertical thickness L2
Is 14 mm or more, the turning mirror 17
Vibrates in a direction parallel to the reflection surface (the direction of arrow c). Therefore, if the vertical thickness L2 is equal to or longer than the surface thickness L1, the position of the laser beam B is not moved, and the pitch formed on the image formed on the photoconductor 30 does not occur.

[0012]

[Table 1]

In this embodiment, the folding mirrors 17 and 1
8 and 19 are both installed on the base plate of the unit and similarly receive vibrations, so they have the same configuration. For example, when there is a folding mirror that is fixed to a member different from the base plate of the unit and is less likely to receive vibrations The folding mirror may have a conventional configuration.

[0014]

As described above, according to the present invention, the length L2 of the second surface perpendicular to the reflection surface of the folding mirror is the same as that of the second surface parallel to the reflection surface .
Since the length of the mirror is equal to or longer than the length L1 of one surface, the folding mirror vibrates in a direction parallel to the reflection surface when receiving the vibration, but does not vibrate in a direction perpendicular to the reflection surface. Therefore, the position of the laser beam reflected by the folding mirror does not change even when it is subjected to vibration.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a laser beam scanning optical device according to an embodiment.

FIG. 2 is a front view of the laser beam scanning optical device according to the embodiment.

FIG. 3 is a diagram illustrating a state of vibration of a folding mirror in the present embodiment.

FIG. 4 is a diagram illustrating a holding unit of a folding mirror in the laser beam scanning device.

FIG. 5 is a diagram showing a state of vibration of a conventional folding mirror.

[Explanation of symbols]

 Reference Signs List 11 semiconductor laser 12 collimator lens 13 cylindrical lens 15 polygon mirror 16 toric fθ lens 17, 18, 19 folding mirror 41, 42, 43 holding member 30 photoconductor drum B laser beam L1 length in direction parallel to reflection surface of folding mirror L2 Length in the direction perpendicular to the reflecting surface of the folding mirror

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinya Sakanashi 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-5-196884 (JP, A ) Hira 5-6415 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 26/10

Claims (1)

(57) [Claims] 1. A laser beam scanning device having a return mirror for reflecting a laser beam, wherein a length of a first surface parallel to a reflection surface of the return mirror is L1, and a length of a first surface parallel to the reflection surface of the return mirror is L1 . When the length of the two surfaces is L2, L1 ≦ L2 is satisfied , and the first surface and the second surface are held by a holding member.
And that it, the laser beam scanning apparatus according to claim.