JPH02273712A - Rotary polygon mirror - Google Patents

Abstract

PURPOSE:To prevent printing quality from deteriorating owing to ghost light by forming connecting surfaces which are at <90 deg. to the axis of rotation between adjacent mirror surfaces of plane mirrors arranged around the axis of rotation. CONSTITUTION:A connecting surface 7 is provided between a mirror surface 5 and an adjacent mirror surface 6 of the rotary polygon mirror 4 and the surface of the connecting surface 7 is at an angle theta3 which is less than 90 deg. to the axis 8 of rotation of the rotary mirror 4. In this case, light which is incident on the connecting surface 7 becomes scanning light 16 having an angle 2theta3 to a surface 9 and the angle theta3 is selected properly to prevent the light from reaching a photosensitive body. Consequently, the photosensitive body is not exposed to the light scanning on the connecting surface 7 as ghost light and the printing quantity is not caused to deteriorate.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a rotating polygon mirror, and in particular, a rotating polygon mirror suitable for reducing noise and saving power without deteriorating print quality used in laser printers, etc. It concerns polygon mirrors.

[Conventional technology]

2. Description of the Related Art In an electrophotographic printing apparatus such as a laser printer that uses a laser as a light source to form a latent image on a photoreceptor, a rotating polygon mirror is used. Laser printers are required to have faster printing speeds, wider printing widths, and higher printing densities.

These specifications, which require smaller size, lower power consumption, lower noise, etc., determine the size, number of surfaces, and rotation speed of the rotating polygon mirror, but there are also conflicting issues and each has its limits. Therefore, a normal rotating polygon mirror has an inscribed circle diameter of 60 mm, a number of surfaces of 8 to 12, and a rotation speed of several thousand to several hundred rpm.

In the rotating polygon mirror determined in this way, ridge lines are generated between adjacent mirror surfaces, noise is generated due to air resistance during rotation, and it is also necessary to increase the vibration voltage. This problem tends to increase as the diameter of the inscribed circle increases, as the number of surfaces decreases, and as the rotation speed increases.

In order to solve this problem, conventionally 1, for example, JP-A-62
As described in Japanese Patent No. 49317, a method has been proposed in which a connecting surface is provided between adjacent mirror surfaces, the connecting surface being located inward from the extended surfaces of both mirror surfaces. As shown in FIG. 2, in this prior art, a connecting surface 3 is provided parallel to the rotation axis 8 between the mirror surface 1 and an adjacent mirror surface 2 that intersects at an angle θ1.
By making 2 larger than θ□, air resistance during rotation is reduced.

[Problem to be solved by the invention]

In the above conventional technology, the reflected light 13 on the connection surface 3 is mirror surface 1.2.
Similarly to the reflected light 14, it reaches the photoreceptor surface 15 and reaches the ji surface 1.
．． In addition to the original latent image formed by the reflected light of No. 2, the latent image is exposed as ghost light, which has a problem of seriously affecting print quality. Even if the connection surface 3 is made cylindrical or spherical, the laser power reaching the photoreceptor surface 15 will only decrease, and there is still a risk of degrading the printing quality, and the object of the present invention is not fundamentally solved. The object of the present invention is to provide a low-noise, power-saving rotating polygon mirror that reduces air resistance during nine rotations while preventing the deterioration in printing quality of the prior art described above.

[Means to solve the problem]

The above object is achieved by forming connecting surfaces having an angle of less than 90'' with respect to the rotation axis between adjacent mirror surfaces of a plurality of plane mirrors around the rotation axis.

[Effect]

The connecting surface between the mirror surfaces of the rotating polygon mirror is 90″ with respect to the rotation axis.
Since the angle is smaller, the light incident on the connection surface becomes scanning light with an angle twice the above angle,
By appropriately selecting the angle, it is possible to prevent the light from reaching the photoreceptor, thereby reducing the noise and power consumption of the rotating polygon mirror without degrading print quality.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to FIG.

FIG. 1 is a perspective view showing an embodiment of a rotating polygon mirror of the present invention. In FIG. 1, there is a connecting surface 7 between the mirror surface 5 of the 9-turn polygon mirror 4 and the adjacent mirror surface 6, and the surface of this connecting surface 7 is at an angle smaller than 90' with the rotation axis 8 of the 1-turn polygon mirror 4. θ
.

According to this configuration, the rotating polygon j! A light ray 10 incident from within a plane 9 perpendicular to the rotation axis 8 passing through the rotary polygon 4 is reflected by the R surface 5 or 6, and is scanned into the plane 9 by the rotation of the rotating polygon flt4. This scanning light 11 reaches a photoreceptor (not shown) through a lens and mirror system (not shown), and forms a predetermined electrostatic latent image. On the other hand, the light incident on the connection surface 7 becomes a scanning light 16 making an angle of 2θ3 with respect to the first surface 9, and the angle θ3
By selecting an appropriate value, it is possible to prevent the light from reaching the photoreceptor. Therefore, the light scanned by the connection surface 7 is
The photoreceptor is not exposed to ghost light, and printing quality is not degraded. Further, since the connecting surface 7 is provided between the mirror surfaces of adjacent polygon mirrors, it is possible to reduce noise and power consumption of the rotating polygon mirror 4.

Furthermore, by mirror-finishing the surface of the connecting surface 7, it is possible to prevent random diffused reflection on the connecting surface 7.
Further deterioration in print quality can be prevented.

Note that the connecting surface 7 does not necessarily have to be a flat surface, and the same effect can be obtained even if it is formed from a part of a conical surface and its generating line forms an angle θ with the rotation axis 8.

(Effects of the Invention) As explained above, according to the present invention, it is possible to prevent the reflected light from the connecting surface provided between adjacent mirror surfaces from reaching the photoreceptor, thereby preventing deterioration in printing quality due to ghost light. This has the effect of providing a rotating polygon mirror that prevents noise and reduces noise and saves power.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the rotating polygon mirror of the present invention;
FIG. 2 is a perspective view of a conventional rotating polygon mirror. 4 is a rotating polygon mirror, 5.6 is a mirror surface, 7 is a connection surface, 8 is a rotation axis, 9 is a surface, 1o is an incident light, 11 is a scanning light, 13.14
is reflected light. Name of patent applicant Hitachi Koki Co., Ltd. t Mouth 4...Rotated i surname! ;,6. ．． ．． Control surface 7... Rinzoku life 13, 74... Reflection tip bud 20

Claims (1)

[Claims] 1. A rotating polygon mirror in which a plurality of plane mirrors are arranged around a rotation axis and connecting surfaces are provided between adjacent mirror surfaces, wherein the connection surfaces are at an angle of 90° with respect to the rotation axis. A rotating polygon mirror characterized by being configured to have a small angle. 2. The rotating polygon mirror according to claim 1, wherein the connecting surface is a mirror surface.