JPH0439053B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating polygon mirror used in an optical deflection device, and more particularly to a rotating polygon mirror having a structure that will not be damaged during assembly.

FIG. 1 is a diagram showing an embodiment of a light deflection device using a rotating polygon mirror. As shown in FIG. 1, an optical deflection device using a rotating polygon mirror generally has a rotating polygon mirror 1
and a motor 2, which is a driving source, to which a rotating polygon mirror 1 is attached, and rotates a beam 4 emitted from a light source 3 such as a laser in the direction of the arrow from point A to point B on the surface to be scanned. It scans.

FIG. 2 is a perspective view of a conventional rotating polygon mirror. The rotating polygon mirror 5 is an integral body made of copper, aluminum, etc., and has a plurality of mirror surfaces 5a formed on its outer periphery.
The ends of the mirror surface 5a in the directions of the rotation axes C and D extend upward to the upper end surface 5b and downward to the position of the lower end surface (not shown). Each mirror surface is cut using a highly accurate processing machine using a diamond cutting tool.

The hole 5c provided in the center is a hole for positioning and fitting the rotating polygon mirror 5 to a shaft to which the rotating polygon mirror is attached, such as the output shaft of a motor.

Such a rotating polygon mirror is processed with great care to avoid scratches, dents, etc. on the mirror surface, and is then attached to a motor. If a rotating polygon mirror made of brittle materials such as quartz glass is scratched or dented by hitting something during processing or assembly, only the reflective film in that area may peel off or the base material may be damaged. If it is missing, the damage will be limited to a very narrow area and will not affect the surrounding area. However, for rotating polygon mirrors made of ductile materials such as copper and aluminum, the effects of scratches, dents, etc. are not limited to that area, but are distorted and spread over a wide area. Now suppose that something collides with point P on the ridge of one of the mirror surfaces 5a of the rotating polygon mirror 5 shown in FIG. 2, and a small dent is created there. FIG. 3 is an enlarged view of the flat prototype placed on the mirror surface 5a and viewed from the front. When looking at the mirror surface 5a through the prototype, minute changes in the surface shape appear over a wide range around point P on the mirror surface 5a, and this deformation reaches into the effective part 5d of the mirror surface surrounded by the two-dot chain line. There is. Generally mirror effective part 5d
The flatness of the mirror is determined so that the light beam reflected by the mirror surface maintains a specified spot shape on the scanned surface, and so that the rotation angle of the rotating polygon mirror and the deflection angle of the light beam are correctly proportional. The accuracy has been kept to a fraction of a micrometer or less. Therefore, even if a very small dent is made at point P, the effective area 5 is formed around it.
Even if the surface shape changes by about 1 to 2 μm within the range d, the rotating polygon mirror can no longer be used.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rotating polygon mirror in which even if the rotating polygon mirror accidentally hits something during processing or assembly, the deformation will not extend to the effective portion of the mirror surface.

In the rotating polygon mirror according to the present invention, two grooves are provided on the upper and lower end surfaces of each mirror surface over the entire circumference of the rotating polygon mirror in order to prevent the effective portion of the mirror surface from being deformed by impact. By doing so, we aim to achieve the above objectives.

The present invention will be explained in detail below.

FIG. 4 is a perspective view showing an embodiment of the rotating polygon mirror of the present invention, and FIG. 5 is a plan view thereof. A feature of the rotating polygon mirror 6 shown in FIG. 4 is that two grooves 6d and 6e are provided on the mirror surface over the entire circumference of the rotating polygon mirror.
Each groove is located near the upper end surface 6b of the mirror surface 6a,
It is provided near the lower end surface (the surface opposite the upper end surface 6b).

This groove is formed, for example, by lathe machining while rotating the rotating polygon mirror 6 about its rotation axis, and the bottom of the groove is as indicated by the broken line in FIG. Fifth
FIG. 6 shows a cross-sectional view of the mirror surface 6a taken along the arrow in the figure.

Now something collides with point P' on the ridge of mirror surface 6a,
Suppose there is a small dent there. Figure 7 is the third
This is an enlarged view of the flat prototype placed on the mirror surface 6a and viewed from the front as in the figure. When looking at the mirror surface 6a through the prototype, there is a slight change in the surface shape of the mirror surface 6a centered on P', but this is at a portion 6f of the mirror surface 6a surrounded by the groove 6d and the upper end surface 6b. The effective part 6 of the mirror surface
It has not reached c. This is because the groove 6d has a kind of buffering effect, and the strain is not transmitted to the mirror surface side where the effective portion 6c is located.

Among the ridges of the rotating polygon mirror 6 in Fig. 4, the one with the highest probability of collision is the ridge with point P' and the ridge on the opposite surface, and the second most likely to collide is the one where the mirror surfaces collide. This is the ridge formed by the area. Therefore, if the structure is as shown in FIG. 4, a considerable portion of possible accidents can be prevented. Protective parts 6f, 6g
The shape may be a disc-shaped configuration different from that of the effective portion.

Width of grooves 6d and 6e and rotation axis of protection parts 6f and 6g
It is desirable that the widths in the C' and D' directions be as narrow as possible, since the width of the portion other than the effective portion of the rotating polygon mirror will be smaller, both from the standpoint of cost and miniaturization of the optical deflection device. However, if these values are too small, the impact applied to point P' may be a little strong,
The protective portion 6f may be greatly deformed and hit the mirror surface side of the effective portion 6c, causing deformation of the surface shape within the effective portion 6c. The widths of the grooves 6d and 6e, the width of the protective parts 6f and 6g, and the depth of the grooves must be set to the minimum necessary and sufficient values, taking into account the material of the rotating polygon mirror and the possible impact strength. .

FIG. 8 is a perspective view of a rotating polygon mirror showing another embodiment of the present invention, and FIG. 9 is a plan view thereof. In the rotating polygon mirror shown in FIG. 8, ridges 7d and 7e are provided on the outside of the mirror surface 7a, on the upper end surface 7b side and on the lower end surface side of the mirror surface 7a, and serve as protection sections. FIG. 10 is a view of the mirror surface 7a cut along the arrow part in FIG.
Even if something hits the ridge P'' of the protective portion 7d and a small dent is made there, the deformation caused by this will be limited to the protective portion 7d thanks to the stepped portion and will not extend to the mirror surface 7a. In this embodiment, the protection part is retracted from the mirror surface, so the effect of preventing deformation of the mirror surface is slightly less than that of the embodiment shown in FIG.
This has the advantage that the process for creating the protective part is simple.

FIG. 11 is a partial sectional view of a mirror surface of a rotating polygon mirror in another embodiment of the present invention. In the rotating polygon mirror 8 shown in FIG. 11, protective portions 8f and 8g are provided in the vicinity of the upper end surface 8b and the lower end surface of the outer peripheral surface of the rotating polygon mirror 8, and are protruded in front of the mirror surface 8a. Small grooves 8d and 8e are provided between the protective parts 8f and 8g and the mirror surface 8a, respectively, to enhance the effect of preventing deformation of the mirror surface. In this embodiment, since the protective portion protrudes in front of the mirror surface, it is highly effective in protecting the mirror surface, but it has the disadvantage that the production process is somewhat difficult.

FIGS. 12 and 13 are diagrams showing an embodiment of a rotating polygon mirror having a different shape from the above-mentioned rotating polygon mirror. The rotating polygon mirror 9 has a polygonal pyramid shape as shown in the figure. The structure of the protection section in this embodiment is basically the same as that in the embodiment shown in FIG. 4 described above. The protective parts 9f and 9g of the rotating polygon mirror 9 are grooves 9 provided near the upper end surface 9b of the mirror surface 9a, respectively.
d and the upper end surface 9b, and between the groove 9e provided near the lower end surface of the mirror surface 9a and the lower end surface. Similar to the example in FIG. 4, the Q point of the ridge or
The range of deformation around point Q or Q' due to the dent made at point Q' is limited to the protective portion 9f or 9g and does not extend to the mirror surface 9a. In the case of a rotating polygon mirror having the shape shown in Fig. 12, the possibility of hitting something is higher at the edge where point Q' is located than at the edge where point Q is located. The smaller the angle between the two surfaces forming the ridge (the more acute the angle), the higher the probability that the ridge will collide.

There are a wide variety of shapes of rotating polygon mirrors in addition to the shapes described in the examples above. The present invention can be applied to any shape of rotating polygon mirror depending on the shape. In other words, the point of the configuration is to intentionally create a part that is more likely to collide with the ridge that you want to protect, and before it hits the ridge that is more likely to collide, the part that was created to protect the latter collides with the former ridge. It is important to protect the parts of the mirror, and to adopt a structure that prevents this impact from being transmitted to the effective part of the mirror surface.

In the above explanation, the effects of the present invention on a rotating polygon mirror made of a ductile material have been described, but the present invention can also be applied to a rotating polygon mirror made of a brittle material, such as peeling off of the reflective film on the effective mirror surface area and It is effective in the sense that it prevents the omission of information.

As explained above, according to the present invention, by adding some ingenuity to the shape of the rotating polygon mirror, it is possible to reduce the occurrence of defects in the rotating polygon mirror during processing or assembly, and to make assembly work easier. This greatly contributes to improving productivity.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the use of a general optical deflection device, Fig. 2 is a perspective view showing a conventional rotating polygon mirror, and Fig. 3 is an enlarged view of the mirror surface 5a of the rotating polygon mirror shown in Fig. 2. , FIG. 4 is a perspective view showing an embodiment of the rotating polygon mirror of the present invention, FIG. 5 is a plan view of the rotating polygon mirror shown in FIG. 4, and FIG. 6 is a mirror surface of the rotating polygon mirror shown in FIG. 5. 6
7 is an enlarged view of the mirror surface 6a of the rotating polygon mirror shown in FIG. 4, FIG. 8 is a perspective view showing another embodiment of the rotating polygon mirror of the present invention, and FIG. 10 is a sectional view of the mirror surface 7a of the rotating polygon mirror shown in FIG. 9, FIG. 11 is a sectional view of the mirror surface in a further embodiment of the rotating polygon mirror of the present invention, FIG. 12 is a perspective view of a different embodiment of the rotating polygon mirror of the present invention, and FIG. 13 is a sectional view of the mirror surface of the rotating polygon mirror shown in FIG. 12. In the figure, 1, 5, 6, 7, 8, 9... Rotating polygon mirror, 5a, 6a, 7a, 8a, 9a... Mirror surface, 5
c, 6c... mirror effective part, 6f, 6g, 7d,
7e, 8f, 8g, 9f, 9g...protection section.

Claims (1)

[Claims] 1. In a rotating polygon mirror having a plurality of mirror surfaces, in order to prevent the effective part of the mirror surface from being deformed by impact, two wires are provided on the upper and lower end surfaces of the mirror surface over the entire circumference of the rotating polygon mirror, in order to prevent the effective part of the mirror surface from being deformed by impact. A rotating polygon mirror characterized by grooves.