JPH03119310A - Rotary rolyhedral mirror - Google Patents

Abstract

PURPOSE:To eliminate the generation of the whistling sounds arising from the air resistance at angle parts, the deformation of deflection reflecting surfaces, the limitation to the high-speed rotation by motor load, etc., by forming the vertex parts where the respective sides of a regular polygonal shape intersect with each other to a straight or curved shape. CONSTITUTION:Effective ranges 8 corresponding to the required scanning regions on the surface to be scanned exist within the deflection reflecting surfaces 4 of the rotary polyhedral mirror. The angle parts which are off the above- mentioned effective ranges and do not contribute to the deflection scanning are cut in a straight line or curve to form the milder angle parts. Namely, the vertexes indicated by a symbol T are cut in a straight or curved shape. The generation of the whistling sounds arising from the air resistance at the angle parts, the deformation of the deflection reflecting surfaces, the limitation in high-speed rotation by the motor load, etc., are eliminated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rotating polygon mirror used in an optical calligraphy optical system.

(Prior Art) A rotating polygonal mirror is used as a deflecting means in an optical calligraphy optical system such as a laser copying machine, a laser printer, a laser facsimile, a laser engraving machine, and the like.

The optical calligraphy optical system is constructed as shown in FIG. 3, for example. That is, in FIG. 5, a light beam emitted from a light source 1 such as a laser is guided to a rotating polygon mirror 3 via a cylindrical lens 2, deflected according to the rotation of this rotating polygon mirror, and then transmitted via an fθ lens 5.6. It is configured so as to guide it to the surface 7 to be scanned.

Here, as shown in FIG. 4, the rotating polygon @3 has a regular polygonal shape when viewed from the direction of the rotating shaft 3A, and each side forms a part of the deflection-reflecting surface 4.

(Problem to be solved by the invention) During scanning, the rotating polygon mirror 3 is rotated at high speed.

During high-speed rotation, air resistance at the corners, which are the vertices where the sides of the regular polygon intersect, places a load on the motor that rotates the polygon mirror. For example, when supported by a rolling bearing, the rotation speed is 10,000 to 15,000.
r, p, m are upper limits. In addition, wind noise occurs and 1
The higher the rotation speed, the higher the rotation speed.

Corners and portions are prone to deformation due to air resistance, and if the deflection and reflection surface 4 is deformed, scanning accuracy will be disturbed.

In this case, one possible way to reduce the air resistance at the corner is to increase the number of deflection-reflecting surfaces 4 to increase the angle at the corner. However, the length of each side of the regular polygon is S (the 6th
When the number of surfaces is increased (see figure), the rate of increase in the radius of the inscribed circle becomes extremely large as shown in Fig. 7, and the weight also increases, resulting in an increase in the load on the motor.

Furthermore, since the effective range of the rotating polygon mirror 3 is determined by the target pixel density, reducing the length S is not realistic due to certain limitations.

The present invention solves the generation of wind noise due to air resistance at corners.

It is an object of the present invention to provide a rotating polygon mirror that can solve problems such as deformation of a deflecting reflection surface and restriction of high-speed rotation due to motor load.

(Means for Solving the Problems) In order to achieve the above object, in the rotating polygon mirror of the present invention, the apex where each side of a regular polygon intersects is formed into a straight line or a curved line.

In this case, it is preferable that the surface intersecting the rotation axis be a gently curved surface or a plane inclined with respect to a virtual plane orthogonal to the rotation axis.

(Function) The corners in the rotation direction have a smooth shape that allows air to flow easily.

(Embodiment) Generally, as shown in FIG. 4, there is an effective range 8 within the deflection/reflection surface 4 of a rotating polygon mirror, which corresponds to a required scanning area on one surface to be scanned. In this example, corners that are outside this effective range and are not involved in deflection scanning are shaved into straight lines or curves to soften them.

That is, the apex portion indicated by the symbol T in FIG. 4 is cut off in a straight line as shown in FIG. 1 or in a curved shape as shown in FIG. 2.

By doing this, the area subject to air resistance is reduced and the air flow is improved, which reduces the motor load due to air resistance, and the air flow is also improved, which reduces wind noise.

Note that the optical system is shown assuming that the light flux incident on the polarizing reflective surface is parallel light in the main scanning direction and linear in the sub-scanning direction, but is not limited to this. There is no particular problem as long as it is within the effective range 8 when doing so.

When it comes to machining, you can achieve great accuracy by first carving out the part to be scraped, and then machining the deflection-reflecting surface while correcting the distortion during cutting.

When the corners are made smooth as shown in Figures 1 and 2, the corners are smoothed as shown in Figure 3 (a) for boat fishing, but in order to improve the strength against deformation, As shown in c), the surface intersecting the axis of rotation is shaped into a gently curved surface or a third shape.
As shown in figure (b), it is formed into a plane that is inclined with respect to the virtual plane perpendicular to the rotation axis! Ru.

(Effects of the Invention) According to the present invention, the generation of wind noise due to air resistance at corners,
Problems such as deformation of the deflection-reflecting surface and restriction of high-speed rotation due to motor load are resolved.

[Brief explanation of drawings]

FIGS. 1 and 2 are front views showing a part of a rotating polygon mirror illustrating an embodiment of the present invention, FIG. 3 is a side view of the rotating polygon mirror illustrating an embodiment of the present invention, and FIG. 5 is a perspective view of an optical writing optical system suitable for carrying out the present invention, FIG. 6 is a view of a rotating polygon mirror viewed from the rotation axis direction, and FIG. 7 is a rotating polygon mirror. It is a graph explaining the relationship between the radius of the inscribed circle and the number of surfaces of a mirror. 3A...Rotation axis, T...Vertex. Side ( Figure 1 (a)

Claims (1)

[Claims] 1. In a rotating polygon mirror whose shape is a regular polygon when viewed from the direction of the rotation axis, the apex where each side of the regular polygon intersects is linear or curved. Features a rotating polygon mirror. 2. The rotating polygon mirror according to claim 1, wherein the surface intersecting the rotation axis has a planar shape orthogonal to the rotation axis. 3. The rotating polygon mirror according to claim 1, wherein the surface intersecting the rotation axis has a gently curved surface or a plane inclined with respect to a virtual plane orthogonal to the rotation axis.