JPS60118821A - Optical scanner - Google Patents

Abstract

PURPOSE:To make scanning light exact and stable without using optical members having high accuracy by providing a right-angled reflection mirror on the front face of a rotary polyhedral mirror to which the ray from a light source is made incident thereto in parallel with the axial center. CONSTITUTION:The laser beam projected from a laser light source 5 is first reflected by reflecting face 1 of a rotary polyhedral mirror 2 and is then successively reflected by the reflecting faces 6, 7 of a right-angled reflection mirror 8. The beam is further reflected again by the same face 1 and is then condensed by a condenser lens 9 so that a spot 11 scans a surface 10 to be irradiated. When the revolving shaft 3 of the mirror 2 inclines, the laser beam from the source 5 changes in the reflecting direction. The incident light and the reflected light are parallel on the mirror 8 in this stage and therefore the laser light reflected again by the face 1 is made incident in the parallel state with the light projected from the source 5 to the lens 9. The spot 11 is therefore focused at the same point on the surface 10. The scanning light is thus made exact and stable without using optical members having high accuracy.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to optical scanning devices used in laser printers and the like.

Technical background of the invention and its problems Conventionally, polygons and hologons have been generally used in optical scanning devices used in laser printers and the like.

In particular, polygons are often used, but the polygons and other optical parts that make up the optical scanning device are required to be highly accurate and require advanced technology. In addition, when the polygon has a small diameter and a small number of reflective surfaces, the laser scanning angle becomes wider, and the number of accompanying adaptive optical members increases.
Moreover, it requires members that are optically difficult to manufacture.

In order to avoid such problems, the polygons can be made into large-diameter polyhedrons, but manufacturing such large-diameter polyhedrons is difficult and expensive.

OBJECTS OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide an optical scanning device that can obtain stable scanning light without using high-precision optical members.

Summary of the Invention The present invention provides a rotating body that rotates about its axis and has a large number of reflective surfaces arranged in an annular shape with a predetermined inclination. A right-angle reflector is provided, and the light rays emitted from the light source are reflected toward the right-angle reflector by the reflective surface of the rotating body.
The light rays incident on this right-angle reflector are reflected toward the same reflective surface of the rotating body, and the light rays reflected again on the reflective surface of the rotating body are focused by a condensing lens to scan the irradiated surface, and the light source The reflected light of the light incident on the reflective surface of the rotating body scans in an arc shape due to the rotation of the rotating body, but this reflected light is reflected again in the opposite direction by the same reflective surface to scan the irradiated surface. The scanning light is linear scanning light, and if there is an error in the inclination of the reflective surface of the rotating body, or if the rotation axis of the rotating body is tilted due to wear of the bearing, etc., the light will be focused by the action of the right angle reflector. The light beam incident on the lens is always parallel, and the scanning light that scans the irradiated surface can be linear scanning light.

Embodiment of the Invention A first embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. A rotating polygon mirror (2), which is a rotating body having six reflective surfaces (1) arranged annularly with a predetermined inclination, is provided, and a rotation axis (2) is provided at the center of the rotating polygon mirror (2).
3) is formed into a shaft hole (4) into which the shaft hole (4) is fitted.

A laser light source (5), which is a light source that emits a laser beam parallel to the axis of the rotating shaft (3), is installed in front of the rotating polygon mirror (2). A right-angled dihedral reflector (8), which is a right-angled reflector, has two reflecting surfaces (6) and (7) orthogonal to each other at a position opposite to the reflecting surface (1) onto which the laser beam is projected. In addition, as shown in Figures 2 and 3, the laser beam reflected by the reflective surface (1) is reflected by the reflective surface (61 (7), and then reflected by the same reflective surface (1) again. A condensing lens (9) for condensing the reflected laser beam is installed in front of the rotating polygon mirror (2), and an irradiated surface 00 is further installed in front of the condensing lens (9).

In such a configuration, the laser beam projected from the laser light source (5) first hits the reflective surface (2) of the rotating polygon mirror (2).
1), and then reflected by the reflecting surface (6) of the right-angle reflector (8).
) (7), and then the same reflecting surface (1)
After being reflected again at , the light is condensed by a condenser lens (9), and the spot α force hits the irradiated turning head.

Here, when the rotating polygon mirror (2) rotates around the axis of rotation (3), the laser beam is projected into the vicinity of the center of the reflective surface (1) and the boundary (near 1j) of the reflective surface (1). The angle of the reflecting surface (1) with respect to the laser beam is different in the case where the laser beam is Reflected by the surface reflecting mirror (8), then reflected again by the reflecting surface (1)
By being reflected by the beam, the arcuate scanning is canceled out, and when the beam is incident on the condenser lens (9), it becomes a linear scanning beam. Therefore, on the irradiated surface αQ, there is one reflective surface (1
), the spot α force will scan on a straight line from point A to point B.

Next, the compensation function in cases where there is an error in the inclination of the reflecting surface (1) or in cases where the axial center of the rotating shaft (3) is inclined will be explained based on FIG. FIG. 5 shows a state in which the axis of the rotating shaft (3) is normal and a state in which it is tilted upward and downward by 3o. The laser beam projected from the laser light source (5) is reflected on the reflecting surface (1) according to the inclination of the axis of the rotation axis (3).
The reflection direction at changes. However, in the right-angled dihedral reflector (8), the incident ray and the reflected ray are parallel, so in both cases the laser beam reflected again on the reflecting surface (1) is emitted from the laser light source (5). The laser beam enters the condenser lens (9) in parallel with the actual laser beam. Therefore, the spot αD is connected to the same point on the irradiated surface QO, and even if there is wear of the bearing or an error in the reflective surface (1) during the manufacture of the rotating polygon mirror (2), the spot αD will be connected to the same point on the irradiated surface α1. Linear scanning light is obtained.

Next, a second embodiment of the present invention will be explained based on FIG. 6. Note that the same parts as those explained in FIGS. 1 to 5 are designated by the same reference numerals, and explanations thereof will be omitted. In the present invention, a laser light source (5) is installed below a rotating polygon mirror (2), and a right-angle prism αj is used as a right-angle reflector.

In such a configuration, a laser beam projected from a laser light source (5) is reflected at right angles from a reflecting mirror α installed in front of a rotating polygon mirror (2), and is incident on a reflecting surface (1). The laser beam reflected by the reflective surface (1) is then reflected by the right angle prism (to), and then reflected again by the same reflective surface (
1) is reflected. The light is then condensed by a condenser lens (9), and a spot α9 hits the irradiated surface 00. Here, in the laser beam facing the condensing lens (9) K, the arc-shaped scanning beam is canceled out and becomes a linear scanning beam as explained in the first embodiment, and there is also an error in the inclination of the reflecting surface (1). Even in cases where there is
Ql) scans on a straight line within a predetermined range.

Effects of the Invention Since the present invention is configured as described above, it is possible to obtain a spot that accurately scans in a straight line on the irradiated surface with a simple structure and without increasing the machining accuracy of the rotating body to a great extent. Even if the axis of the rotating body is tilted due to wear of the bearing, etc., the spot on the irradiated surface can be accurately scanned in a straight line.

[Brief explanation of the drawing]

Fig. 1 is a front view of a rotating polygon mirror in the first embodiment of the present invention, Fig. 2 is a side view showing the scanning state of the laser beam, Fig. 3 is a plan view thereof, and Fig. 4 is a diagram of the rotating polygon mirror. FIG. 5 is an explanatory diagram showing the compensation function for the tilt of the rotating polygon mirror, and FIG. 6 is a side view showing a second embodiment of the present invention. . 1...Reflecting surface, 2...Rotating polygon mirror (rotating body), 5...
... Laser light source (light source), 6-7... Reflective surface, 8.
...Right-angle dihedral reflector (right-angle reflector), 9... Condensing lens, 10... Irradiated surface, 13... Right-angle prism (right-angle reflector) Applicant: Tokyo Electric Co., Ltd.

Claims (1)

[Claims] A light source that includes a rotating body that rotates about its axis and has a large number of reflective surfaces arranged in an annular shape with a predetermined inclination of 1°, and emits a light beam toward the reflective surfaces. In addition, an irradiated surface is provided on which the light beam reflected by the reflective surface scans, and a right-angle reflector is provided that has two reflective surfaces orthogonal to each other and the incident light beam and the reflected light beam are parallel to each other. installed at a position where the reflected light from the reflective surface of the rotating body is incident and the reflected light from the right angle reflector is reflected toward the same reflective surface of the rotating body; An optical scanning device characterized in that a condenser lens is provided between the rotary body and the irradiated surface to condense reflected light beams that are reflected again onto the irradiated surface. 2. The optical scanning device according to claim 1, wherein a right-angle reflector is installed in front of the reflecting surface of the rotating body onto which the light beam from the light source is incident.