JPH07199106A - Deflecting scanner - Google Patents

Abstract

PURPOSE:To avoid the use of the clouded area of a polygon mirror and to attenuate the reflection factor of the clouded area to keep the picture quality well. CONSTITUTION:A revolving shaft 12 is freely rotatably fitted to a sleeve 14 fitted and fixed to a housing 13. The revolving shaft 12 is supported by a dynamic pressure fluid bearing and is rotated and driven by a driving motor. A polygon mirror 11 is fixed to this revolving shaft 12 to constitute a deflector 23, and this deflector 23 is fixed to an optical box 25 to constitute a deflecting scanner. When the polygon mirror 11 is left rotated in a plane view, a laser unit is so adjusted that a light beam is not made incident on clouded parts 11b because corner parts in the direction opposite to the rotating direction of respective mirror faces 11a form the clouded parts 11b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection scanning device for deflecting and scanning a light beam by rotating a polygon mirror by a drive motor.

[0002]

2. Description of the Related Art Conventionally, a deflection scanning device of this type is shown in FIG.
A hexagonal prism-shaped polygon mirror 1 as shown in FIG. The polygon mirror 1 is rotatably driven by fitting and fixing a rotary shaft of a drive motor (not shown) into its shaft hole 2.

[0003]

However, when the polygon mirror 1 in the shape of a polygonal column rotates in the direction of the arrow around the shaft hole 2, for example, the air Z near one mirror surface 3, as shown in FIG. After flowing along the mirror surface 3, the corner 4
Past the next mirror surface 5 and the distance Y from the corner 4
It reattaches to the mirror surface 5 which is separated by a distance and flows toward the corner 6. Here, the size of the distance Y is uniquely determined from the shape and the number of rotations of the polygon mirror 1, and a negative pressure is generated inside the air Z where the air Z separates within the distance Y, and the air exists there. A vortex region X in which Z flows backward is formed.

In this vortex region X, air Z and air Z
Dust and the like in the inside is caught up, these dusts adhere to the respective mirror surfaces 3, 5, 7 and a clouded area 8 is formed at one corner of these mirror surfaces 3, 5, 7 as shown in FIG. It Therefore, the reflectance of the light beam is reduced in the cloudy region 8, and the light beam reflected in the cloudy region 8 has a problem that the image quality is deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a deflection scanning device which maintains a good image quality by avoiding the use of a clouding area on the mirror surface.

[0006]

A deflection scanning device according to the present invention for achieving the above object is a deflection scanning device for rotationally driving a polygon mirror to deflect and scan a light beam. Is provided with an unused region which is not used for deflecting and scanning the light beam.

[0007]

In the deflection scanning apparatus according to the present invention, since the unused area which is not used for deflecting and scanning the light beam is provided in a part of each mirror surface of the polygon mirror, the light beam is incident on the unused area. Without doing so, the polygon mirror deflects and scans the light beam outside the unused area.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a sectional view of the first embodiment, in which a polygon mirror 11 is fixed to a rotary shaft 12 supported by a dynamic pressure bearing of a drive motor. A sleeve 14 is fitted and fixed to the housing 13, and a rotary shaft 12 is rotatably fitted to the sleeve 14. Herringbone-shaped shallow grooves 12a and 12b are engraved on the outer peripheral surface of the rotary shaft 12 to form a dynamic pressure radial bearing. Housing 1
A fixed plate 16 having a thrust plate 15 disposed below the fixed shaft 12 is fixed to the lower end portions of the sleeve 3 and the sleeve 14, and a spiral shallow groove (not shown) is formed on the upper surface of the thrust plate 15 to form a dynamic thrust bearing. Is configured.

On the other hand, a flange 17 is fitted and fixed to the rotary shaft 12, and a rotor 18 is fixed to the lower portion of the flange 17. A drive magnet 19 is fixed to the inner surface of the rotor 18, and an FG magnet 20 is fixed to the outer peripheral end of the rotor 18. A stator coil 22 is arranged on a printed circuit board 21 fixed to the housing 13 below the magnet 19 to form a drive motor.

By fixing the above-mentioned polygon mirror 11 on the flange 17, the deflector 23 is formed.
The deflector 23 is attached to the optical box 25 of the deflection scanning device by screws 24. The optical box 25 includes a laser unit (not shown) that emits a light beam toward the polygon mirror 11, and the polygon mirror 11
And an optical system (not shown) that forms an image of the deflected and scanned light beam, and a photoconductor (not shown) is arranged outside the optical box 25.

Here, as shown in FIG. 2, when the polygon mirror 11 rotates in the direction of the arrow, a clouding portion 11b is formed at one corner of each mirror surface 11a due to adhesion of dust or the like.
In the polygon mirror 11, only the reflection area B excluding the cloudy area A which is the maximum range of the cloudy portion 11b is used for deflection scanning of the light beam. Therefore, the laser unit is adjusted so that the light beam does not enter the cloudy area A of the polygon mirror 11. Therefore, when the polygon mirror 11 rotates, the light beam does not enter the cloudy area A but is reflected only in the reflective area B.

FIG. 3 shows a polygon mirror 31 of the second embodiment.
FIG. The polygon mirror 31 has a cloudy area A
Paint with extremely low reflectance in area C, which is slightly larger than
2 is applied, and the other mirror surface 31a is used as the reflection area D. The reflection area D is predetermined as a predetermined deflection scanning range of the light beam.

As described above, in this embodiment, the light beam is not deflected and scanned in the paint region C, but is deflected and scanned only in the reflection region D, so that the polygon mirror 11 rotates in the direction of the arrow and dust in the cloudy region A. Even if adheres, since the area A is smaller than the coating area C coated with the low-reflectance coating, the reflective area D for deflecting and scanning the light beam does not cloud, and the light beam reflected there weakens. There is no such thing.

Further, in the present embodiment, the light beam reflected in the cloudy area A is not reflected in the optical box 25 and does not enter the beam detector (not shown), so that the image forming apparatus may malfunction. Absent.

FIG. 4 shows a polygon mirror 41 of the third embodiment.
6 is a perspective view of the polygon mirror 41. In the same area C as in the second embodiment, a coating 42 such as a film having a very small reflectance is attached to the polygon mirror 41 instead of the paint.

In the third embodiment, the same effect as the second embodiment is obtained, but the labor and time for drying the paint in the second embodiment are unnecessary, and attention must be paid to paint dripping. Disappear.

FIG. 5 shows a polygon mirror 51 of the fourth embodiment.
2 is a perspective view of the polygon mirror 51.
In the same region C as in the third embodiment, a non-machined surface 52 that is ground lower than the mirror surface 51a is provided.

In the fourth embodiment, since the reflectance of the non-machined surface 52 is extremely small, the same operational effects as those of the first to third embodiments can be obtained.

[0019]

As described above, in the deflection scanning device according to the present invention, an unused area which is not used for the deflection scanning of the light beam is provided in a part of the mirror surface, and the light beam is prevented from entering this unused area. Therefore, even if the polygon mirror rotates and the unused area becomes cloudy, the light beam can be deflected and scanned in an area other than the unused area, and the image can be held well.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment.

FIG. 2 is a perspective view of the polygon mirror.

FIG. 3 is a perspective view of a polygon mirror according to a second embodiment.

FIG. 4 is a perspective view of a polygon mirror according to a third embodiment.

FIG. 5 is a perspective view of a polygon mirror according to a fourth embodiment.

FIG. 6 is a perspective view of a conventional polygon mirror.

FIG. 7 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 11, 31, 41, 51 Polygon mirror 11a, 31a, 41a, 51a Mirror surface 11b Cloudy part 32 Paint 42 Coating 52 Non-processed surface A Cloudy area B, D Reflective area C Non-reflective area

Claims (4)

[Claims] 1. A deflection scanning device for rotating a polygon mirror to deflect and scan a light beam, wherein a part of each mirror surface of the polygon mirror is provided with an unused area which is not used for deflecting and scanning the light beam. A deflection scanning device characterized by the above. 2. The deflection scanning device according to claim 1, wherein a coating material having a low reflectance is applied to the unused area. 3. The deflection scanning device according to claim 1, wherein a film having a small reflectance is attached to the unused area. 4. The deflection scanning device according to claim 1, wherein a mirror surface is not processed in the unused area to reduce the reflectance.