JPS6055316A - Optical deflector - Google Patents

Abstract

PURPOSE:To improve the precision of relative positions of a polygon mirror and a spindle and to simplify the structure of an optical deflector which rotating the polygon mirror around the spindle and deflects reflected light in a different direction by forming the spindle and polygon mirror in one structure. CONSTITUTION:A motor 2 and the spindle 3 are incorporated in a cylindrical housing 1. The spindle 3 is provided with rotors (not shown in a figure) in the motor 2, which drive them directly. The polygon mirror 40 is provided integrally with the spindle 3 where the spindle 3 faces a light source passage 12. This polygon mirror 40 is made of a regularly octagonal flat plate, and its flanks are reflecting surfaces 41. The center axis of the polygonal mirror 40 is aligned with the spindle 30, and the mirror surface 41 is parallel to the axis of rotation of the spindle 3. Thus, the spindle 3 and polygon mirror 40 are formed in one body, so the spindle 3 is rotated with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical deflector in which a polyhedral mirror mechanically rotates to deflect light.

[Technical background of the invention and its problems]

Recently, laser printers using semiconductor lasers have been developed. In this laser printer, an optical deflector using a polyhedral mirror is used to convert information such as a document into an electrical signal. This polyhedral mirror generally has the shape of a thin regular polygon, and each side surface thereof has a mirror surface. here.

The polyhedral mirror is coaxially mounted on a rotatable spindle and is rotated by the spindle to reflect incident light in different directions. At this time, in order to obtain high resolution in the above-mentioned electrical signal conversion, it is necessary to increase the rotation speed of the spindle (1Q'rpm or more) and increase the light deflection speed. Furthermore, since an optical system is used as the conversion means, it is necessary to maintain the positional accuracy of the polygon mirror with very high precision, and for this purpose, the rotational precision of the spindle must be made highly precise. In other words, the spindle is required to rotate at high speed and with high rotation accuracy. For this reason, a herringbone type or tilting pad type hydrodynamic gas journal bearing and a repulsion type magnetic thrust bearing are used as spindle bearings. By using these two bearings, in addition to satisfying the above conditions, advantages such as low frictional torque loss and no need for lubricating oil can be obtained.

As described above, the optical deflector requires high rotation accuracy of the polygon mirror. For this reason, high accuracy is also required for the relative positional accuracy between the polyhedron's sharp reflecting surface and the rotation axis of the spindle. Conventionally, when assembling such a polyhedral mirror and a spindle, the polyhedral mirror was inserted into a predetermined position of the spindle, adjusted so that their axes matched, and then fixed by tightening screws with nuts or the like. However, in this case, it is very difficult to adjust the positions of the polygon mirror and the spindle, and careless adjustment easily causes axis misalignment, making it impractical. Unfortunately, even if you spend a lot of time adjusting the position as described above, it is difficult to maintain an accuracy of several seconds or less in terms of the inclination between the reflecting surface of the polygon mirror and the spindle rotation axis. In addition, it is extremely difficult to adjust the misalignment of the rotation axes of the polygon mirror and spindle, that is, the concentricity, to within a few microns, and this kind of precision is not sufficient to provide a higher-performance optical deflector. It can not be said.

In addition to the method described above, the following method is also available for assembling the polyhedral mirror and spindle. That is, the polyhedral mirror and the spindle are rough-machined separately in advance, and then assembled by tightening screws, press-fitting, etc. After this, the integrated polyhedral mirror and spindle are finished at the same time. With this method, the relative positions of the polyhedral mirror and the spindle can be taken into consideration during the finishing stage, so that positional adjustment of each is unnecessary. However, in Jin's method, stress is generated between the polygon mirror and the spindle during assembly after rough machining, and it is thought that residual strain may occur. As a result, this residual strain affects the finishing process, and it is often not possible to achieve sufficient accuracy.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical deflector that allows the relative position of a polyhedral mirror and a spindle to be highly accurate and has a simple structure.

[Summary of the invention]

The present invention is an optical deflector that reflects incident light by a polygonal mirror provided on a rotatable spindle, and deflects the reflected light in different directions by rotating the polygonal mirror with the spindle. It is characterized by having an integrated structure.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view showing this embodiment. Cylindrical know-how sink (
1) has a built-in motor (2) and a spindle (3). The spindle (3) is provided with a rotor (not shown) inside the motor (2).
) is rotated directly by Further, a bearing mounting base (4) forming a cylindrical lid body is attached to the upper end of the housing (1), and a disc-shaped end plate (5) with a concave center portion is fitted to the lower end. . Furthermore, a light source entrance part (1o) for guiding the light source inside is provided on the side of the housing (1). This light source entrance part (101 is an entrance opening αD into which the light source enters,
It has a light source path (12) that guides the incident light source inside, and an optical system (12) consisting of an fθ lens group for organizing the light sources according to predetermined specifications is installed between this entrance port (lυ) and the light source path (12).
(not shown) is provided.

On the other hand, on the inner circumferential wall (l!19) of the housing (1) is a cylindrical first dynamic pressure gas journal bearing σ.
Q is held between the same cylindrical spacer (mark) and the bearing pusher plate (181) so that its upper end surface and the upper end surface of the inner circumferential wall (iω) are flush with each other. teeth,
Cylindrical magnetic bearing housing (20+ is the housing (1
), and is held between the end plate (5) and the spacer (1'0).A concentric cylindrical magnetic bearing stator 1211 is fixed to the inner peripheral surface of this magnetic bearing housing (with adhesive). Note that the inner diameter of the magnetic bearing stator (20) is smaller than the inner diameter of the first hydrodynamic gas journal bearing (1). (15) Is 2 dynamic pressure gas journal bearings (2 bearings) are provided.The first and second dynamic pressure gas journal 41j1 bearings (HS, (2
Z has the same specifications.

As mentioned above, the spindle (3) is provided with a motor rotor (not shown) inside the motor (2), as well as a first glaze and a second dynamic pressure gas journal receiver (151, +22).
The sliding shaft part (2) has semicircular cross-sectional grooves carved in the direction of the rotation axis at equal intervals at a location facing the sliding shaft part (2), 0θ. This sliding shaft part (2G), CI! ? ) and the first
and a second hydrodynamic gas journal bearing (151, Inc.)
The bearing clearance with the bearing is formed to be several micrometers to several tens of micrometers. Further, at the lower end of the spindle (3), there is a one-step circular small diameter part (end) at the location facing the magnetic bearing stator (21), and this small diameter part 0 (J) has a %N
A cylindrical magnetic bearing rotor (GJ) is compressed and fixed by a nut via a washer (c). The bearing clearance between the magnetic bearing stator 01) and the rotor 01) is several hundred μm, and the two form a pair to form a magnetic thrust bearing C3. Here, the magnetic bearing stator (21
) and rotor t31), as shown in FIG. 2, each have a pair of radially magnetized permanent magnets made of, for example, ferrite, in a cylindrical shape, with eight poles and an N pole.

Two sets (the number of sets is appropriately selected depending on the weight of the spindle (3)) are integrally laminated with an adhesive so that the S poles and the N poles alternate. Then, insert the spindle (3) and insert the magnetic bearing stator at+ and the magnetic bearing rotor 01.
) are set so that when they face each other, the two opposing magnetic poles become different polarities.

Moreover, a polyhedral sharp (vertical side) is provided integrally with the spindle [3] at a location facing the light source passage 0 of the spindle (3). This polyhedral mirror (49) is a flat regular octagon, and each side is a reflecting surface (41). , mirror surface (41) and spindle (
3) is set to be parallel to the rotation axis.

The processing of the spindle (3) and polyhedral mirror (40) at this time is as follows:
For example, a single bar is subjected to rough machining by forging, cutting, etc., then finishing is performed on the sliding shaft part (a) and the isometry part, and finally, using the rotation axis of the spindle (3) as a reference. Reflective surface (gives a mirror finish to the surface).

The upper end of the spindle (3), that is, the upper part of the second sliding shaft (2η) has a small diameter and protrudes from the bearing mounting base (4). The dust cover (4th floor) is attached from the top of the bearing mounting base (4).

Next, the operation of this embodiment will be explained. spindo 7+
1/(3) is a magnetic thrust bearing (: floating in the axial direction due to the roughness. That is, the % magnetic thrust bearing 62 is.

The rotor 01) and the spindle (3) can be held in a non-contact manner by forming a loop of magnetic lines of force as shown by the broken line in FIG. 2 and by a horizontal attraction force. Here, motor (2)
When the spindle (3) is started to rotate by It only needs to be larger than the sliding friction force of 2'IJ, and it will be a very small value.Therefore, the rotation start of the spindle (3) is very smooth, and even when rotating at high speed, there is no solid friction, and it is also very smooth. The polyhedral mirror (41m) is precisely machined and integrally formed with the spindle (3).For this reason, the polyhedral mirror (40m)
The parallelism between the reflecting surface (41) and the axis of the spindle (3) can be maintained with extremely high precision, and the relative position error is almost zero, both at the initial stage of use and during long-term use.
Close to. Therefore, the spindle (3) has very high precision from a dynamic viewpoint.

Therefore, the whirling of the rotating polyhedron (41), that is, the five-sided wobbling, becomes extremely small. As a result, the rotation accuracy of the spindle (3) is maintained within 0.1 μm when whirling at 1.5 x 10' rpm. At the same time, it was possible to maintain the inclination angle of the rotation axis within θ=1" when rotating in conical mode.

In this way, in this embodiment, the spindle (3) and the polyhedral mirror (40) are integrally formed, so that the inclination of the spindle (3) is within 3, and the polyhedral ffl (4 (1) and the polyhedral mirror (40) are The polyhedral mirror (40) could be provided on the spindle (3) with a relative error of 1 to 3 μm in misalignment of the rotation axis, that is, concentricity.

FIG. 3 shows an outer rotor type embodiment in which a fixed shaft (50) is inserted into a hollow spindle (3).

In this case, the spindle (3) on the fixed shaft (5) is supported by sliding bearings (51) provided at the upper and lower ends.

In this example as well, the polyhedral mirror (decoy) has an integral structure with the spindle (3), and the spindle (3) and the polyhedral mirror (decoy)
The relative position with respect to 40 is maintained with high accuracy. For this reason,
The motor (2) allows the spindle (3) to rotate around the fixed shaft (50) with highly accurate wobbling.

〔Effect of the invention〕

As explained above, since the optical deflector of the present invention has an integral structure of the spindle and the polygon mirror, the relative position 14 between the spindle and the polygon mirror can be maintained with high precision. As a result, the wobbling of the polyhedral mirror during rotation of the spindle, that is, the surface wobbling, has become extremely small.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing an embodiment of the present invention, FIG. 2 is a partially enlarged view of the embodiment, and FIG. 3 is a partial sectional view showing a main part of the embodiment of FIG. 3...Spindle, 40...Polyhedral sharp agent Patent attorney Isuke Norichika (and 1 other person) Figure 1 1F Figure 2 2 Figure 3

Claims (1)

[Claims] In an optical deflector that reflects incident light by a polygon mirror provided on a rotatable spindle, and deflects the reflected light in different directions by rotating the polygon mirror by the spindle, the spindle and the polygon mirror are connected to each other. An optical deflector characterized by having an integrated structure.