JPH04134315A - Scanning optical device - Google Patents

Abstract

PURPOSE:To obtain high accuracy at low cost by providing a disuse part which is not used for optical deflection on the peripheral surface of a rotary mirror and providing an energizing means which presses the rotary shaft of the rotary driving motor for the rotary mirror and the internal surface of the rotary mirror against the disuse part and fits them. CONSTITUTION:The rotary mirror 101 is constituted by grinding the part which faces a cylindrical metallic member into a parallel plane, using the two surfaces as reflecting surfaces 101a for deflecting a light beam for scanning, and using the cylinder part as the disuse part 101b which is not used for the deflection scanning. This disuse part 101b is thread-cut and the inner peripheral surface of the rotary mirror 101 is pressed against the outer peripheral surface of the rotary shaft 2 and fixed with a screw 102. Thus, the rotary shaft 22 of the rotary driving motor 2 and the internal surface of the rotary mirror 101 are pressed against the disuse part 101b and fitted, so the high accuracy is obtained at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning optical device for optically scanning a scanned part used in a laser beam printer or a bar code reading device.

[Prior Art] Conventionally, in a scanning optical device that scans a light beam, a rotating polygon mirror that rotates in one direction has been widely used in terms of rotational speed stability and scanning speed.

However, such a rotating polygon mirror has a problem in that its deflection scanning surface or reflection surface is tilted from a plane perpendicular to the ideal main scanning surface on which the deflected scanning beam is to be formed. As a means to solve such problems, for example,
The following is disclosed in No. 3-188112.

That is, opposing portions of a cylindrical metal member are cut into parallel planes, and these two surfaces are used as reflective surfaces for deflecting and scanning the light beam. The rotating mirror can be mounted so that the two parallel reflecting surfaces are parallel to the direction of inclination of the flange surface. This prevents tilting and minimizes the pitch unevenness of the scanning line on the surface to be scanned by the scanning beam. This method eliminates the need to use an expensive and special optical system (so-called tilt correction optical system) for correcting the above-mentioned tilt, which was conventionally required.

Furthermore, as a method of mounting this rotating mirror so that the two parallel reflecting surfaces are parallel to the direction of inclination of the flange surface, for example, as shown in FIG. There is one disclosed in No. 30234. In Fig. 5, l is a rotating mirror whose two opposing surfaces are cut flat and mirror-finished to serve as reflective surfaces for deflecting and scanning the laser beam. The mirror 1 is attached to the central part of the rotor 20 of the drive motor 2 on a part 21 (attached to a flange), and the flange 21 is fixed to the rotating shaft 22 by shrink fit or adhesive, and the rotor 20 is crimped and fixed. Inside this rotor 20 is a drive magnet 2.
The rotor 20 is rotationally driven in accordance with the force generated between the magnet 23 and the coil 24 by energizing the drive coil 24 mounted on the main body of the motor 2 at a position opposite to the magnet 3 . The rotational drive of this rotating mirror is controlled with high precision by a Hall element (not shown) or the like. Further, the drive motor 2 includes a bearing 25 and a motor case 26 having the bearing 25 and the like therein. The rotating mirror 1 is regulated from above by an elastic member 11 (biasing means) such as a star-shaped spring, and is pressed and fixed against a flange 21.
Rotor 20 flange 21. The rotating shaft 221, rotating mirror 1, etc. rotate together. A fixing member 12 such as a tension washer is fixed to the rotating shaft 22 above the elastic member 11 and presses the elastic member 11 against the top of the rotating mirror 1.

Then, the rotating mirror 1 is adjusted and fixed so that the reflective surface provided on the side surface thereof is parallel to the direction of inclination of the surface of the flange.

[Problems to be Solved by the Invention] However, in the above conventional example, since the rotating mirror l is attached to the rotating shaft 22 via the flange 21, (1) the reflection surface of the rotating mirror 1 and the flange 21 are When mounting, the surface and perpendicularity must be highly accurate.

(2) Since a large gap is provided between the inner peripheral surface of the rotating mirror 1 and the rotating shaft 22 in order to adjust the mounting position, the distance between the central axis of the rotating shaft 22 and each reflective surface of the rotating mirror 1 is Due to the difference, the scanning time for each surface is different.

(3) Since the rotating mirror 1 is pressed against the flange 21,
Unless the mounting surface is maintained with high precision, the surface precision of each reflective surface of the rotating mirror l will also deteriorate.

In addition, it has been difficult to reduce the cost.

[Means for Solving the Problems] According to the present invention, the rotating mirror has a used part used for light deflection and an unused part not used for light deflection on the peripheral surface of the rotating mirror, and the rotating mirror is provided in the unused part. By providing a biasing means for attaching the rotary shaft of the rotary drive motor and the inner surface of the rotary mirror against each other, an inexpensive and highly accurate scanning optical device is made possible.

[Embodiment] FIGS. 1 and 2 are diagrams showing an embodiment of the scanning optical device of the present invention. In the figure, the same members and the same functions as those in FIG. 5 are designated by the same numerals and their explanations will be omitted. rotating mirror 1
In 01, opposing parts of a cylindrical metal member are cut into parallel planes, and these two surfaces are used as reflective surfaces 101a for deflecting and scanning the light beam, and the cylindrical part is used as an unused part 101b that is not used for deflecting and scanning. are doing. This unused part 101
b is threaded and fixed to the rotating shaft 22 with a screw 102. In other words, the inner peripheral surface of the rotating mirror 101 is pressed against and fixed to the outer peripheral surface of the rotating shaft 22.

In FIG. 2, which shows a schematic configuration, laser light emitted from a laser light source unit 3 including a semiconductor laser and a collimator lens enters a rotating mirror 101, where it is deflected and scanned. f and beam incidence angle θ
After passing through an imaging lens system 4 equipped with an image (given by the product of Further, around the photosensitive drum 5, there are process equipment (not shown), such as a secondary charger and a photosensitive drum 5.
A developing device, a transfer charger, a cleaner, etc., are provided to apply a developer to the exposed portion of the image and perform reversal development, and the image is printed on paper or the like using a known electrophotographic process. Here, a reflective surface 1 is provided on the outer peripheral surface of the rotating shaft 22 of the motor 2.
Since the inner circumferential surface of the rotating mirror 101 having 01a is pressed and fixed, the reflecting surface 101a of the rotating mirror 101
If the inner circumferential surface and the rotating mirror 101 are configured with high precision, the rotating mirror 101
If the accuracy of the mounting surface (bottom surface) with the flange 21 is poor, or if there is an inclination angle between the flange 21 and the rotating shaft 22,
Furthermore, even if these mounting surfaces are distorted, it is not related to their accuracy (a rotating mirror can be attached to the rotating shaft 22. Therefore, it is possible to attach a rotating mirror to the rotating shaft 22. It is possible to prevent scanning line pitch unevenness in the sub-scanning direction, which is a direction perpendicular to the main scanning plane (the ray bundle surface formed by the deflected and scanned beam over time). The rotating mirror 101 is not pressed, but is merely used as a height reference.In Fig. 1, a circumferential groove 103 is provided in the threaded portion of the inner peripheral surface of the rotating mirror 101. When the rotating mirror 101 is pressed against the rotating shaft 22 by the screw 102, it is accurately stabilized with respect to the rotating shaft 22 because it is fixed in contact with two surfaces: the outer circumferential surface of the rotating shaft and the inner circumferential surface of the rotating mirror. In addition, when the rotating shaft 22 rotates with a wobbling motion (angle wobbling) due to dynamic imbalance, etc., it is adjusted so that it is parallel to the direction of inclination, but the groove 10
3 is provided, the rotating shaft 2 is connected by the screw 102.
There is also the advantage that even if there is a scratch or the like on 2, the mounting accuracy will not be affected.

Furthermore, since the rotary mirror is not fixed and adjusted by pressing it against the seat surface of the flange, there is no need to make the gap between the inner circumferential surface of the rotary mirror 101 and the rotary shaft 22 larger than necessary, and the gap between the central axis of the rotary shaft 22 and the rotary mirror Since the distance between each reflective surface 101 is stable, there is little difference in scanning time depending on each reflective surface.

As explained above, by fixing the rotating mirror 101 by pressing the inner circumferential surface and the rotating shaft 22, only the inner circumferential surface of the rotating mirror 101 can be machined with high precision, and the cost can be reduced. In addition, it becomes possible to provide a highly accurate scanning optical device.

[Embodiment 2] FIG. 3 is a diagram showing a second embodiment of a rotating mirror drive mechanism used in the scanning optical device of the present invention. The rotating shaft 222 has two herringbone-shaped shallow grooves 231, and inside the motor case 226, a sleeve 225 that rotatably fits on the rotating shaft 222 is formed in the herringbone-shaped shallow grooves 231. The inner circumferential surfaces of the sleeve 225 and the sleeve 225 are arranged at opposing positions, forming a dynamic pressure radial bearing. Also,
At a position facing the lower end surface of the rotating shaft 222, a thrust member 227 having a spiral shallow groove 232 is disposed at the lower end of the sleeve 225, forming a hydrodynamic thrust bearing. The rotating shaft 222 is rotatably supported without contact. Here, the inner circumferential surface of the rotary mirror 101 is pressed and fixed to the outer circumferential surface of the rotating shaft 222 by screws 102, as in [Embodiment 1].

With this configuration, the rotating mirror 101 can be rotated with high precision, so that a scanning optical device with higher precision can be realized.

Incidentally, instead of the above-mentioned dynamic pressure thrust bearing, a sliding bearing such as a pivot bearing can be used as the thrust bearing, and the cost can be reduced.

[Embodiment 3] FIG. 4 is a diagram showing a third embodiment of a rotating mirror drive mechanism used in the scanning optical device of the present invention. A hole 302 is provided in an unused portion 301b of the rotating mirror 301 that does not perform deflection scanning, and a portion 303 with a larger diameter than the hole 302 is provided in the unused portion 301b of the rotating mirror 301, which is not used for deflection scanning.
is provided. Here, an elastic member 304 such as a spring is inserted into the hole 302, and a locking member 305 that locks with a portion 303 having a larger diameter than the hole 302 is inserted, whereby the inner circumferential surface of the rotating mirror 301 is rotated. It is pressed against and fixed to the outer peripheral surface of the shaft 22. The effects of the present invention can also be achieved by such a simple method. Alternatively, adhesive may be inserted into the joint surfaces to ensure fixation.

[Effects of the Invention] As explained above, the rotating mirror has a used part used for optical deflection and an unused part not used for optical deflection on the circumferential surface, and the unused part has a rotation drive motor for the rotating mirror. By providing a biasing means to which the rotating shaft of the rotating mirror and the inner surface of the rotating mirror are pressed against each other, an inexpensive and highly accurate scanning optical device can be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, FIG. 2 is a schematic configuration diagram thereof, FIG. 3 is a cross-sectional view of the second embodiment, FIG. 4 is a cross-sectional view of the third embodiment, FIG. 5 is a cross-sectional view for explaining a conventional scanning optical device. 1.101,301...Rotating mirror 102.304,305...Biasing means 103...
...Circumferential groove 2 ...Motor 22.222 ...Rotating shaft 25 ...Bearing 225 ...Bearing sleeve 231 ... Herringbone-shaped shallow groove 232...
・・・・Spiral-shaped shallow groove Figure 3 Figure 4 Figure 5

Claims (5)

[Claims] (1) In a scanning optical device in which a light beam emitted from a light beam generating means is deflected by a rotating mirror, the rotating mirror has a used part used for light deflection and an unused part not used for light deflection on its peripheral surface. What is claimed is: 1. A scanning optical device, comprising: a biasing means attached to an unused portion of the rotating mirror by pressing the rotating shaft of the rotating mirror drive motor against the inner surface of the rotating mirror. (2) The scanning optical device according to claim 1, wherein the biasing means comprises a screw member. (3) The scanning optical device according to claim 1, wherein the biasing means includes an elastic member and a locking member. (4) an inner circumferential groove is provided on the inner surface of the rotating mirror;
2. The scanning optical device according to claim 1, wherein a biasing means is located in the groove so that the rotating shaft of the rotating mirror drive motor and the inner surface of the rotating mirror are pressed against each other. (5) The scanning optical device according to claim 1, wherein the rotating shaft to which the rotating mirror is attached is supported by a dynamic pressure bearing.