JPS6049294B2 - light deflection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical deflection device using a rotating polygon mirror.

More specifically, the rotating polygon mirror is coupled to the rotating shaft by a flexible member, and a float member fixed to the substrate is provided opposite to the reference surface of the rotating polygon mirror.
By rotating the rotating shaft, the small distance between the reference surface of the rotating polygon mirror and the float member is kept constant by the fluid pressure, and the polarized light is the same without being affected by the whirling of the rotating shaft. This article relates to an optical deflection device configured to scan on a trajectory. Although it is widely practiced to deflect a light beam using an optical deflection device using a rotating polygon mirror, it is extremely difficult to improve the deflection accuracy.

Deflection errors in an optical deflection device using a rotating polygon mirror are caused by processing errors of the rotating polygon mirror itself, processing errors of the rotating shaft to which it is attached, errors of bearings, assembly errors, and the like. Among these errors, even if the effects of machining errors of the rotating shaft and errors of the bearings are removed, the deflection accuracy can be greatly improved. FIG. 1 shows an optical deflection device in which deflection errors are reduced as described above. A sleeve 3 is fixed to the output shaft 2 of the motor 1.

A central portion of a flexible flat plate member 5, which is a flexible plate spring with a gimbal structure, is fixed to the upper end of the sleeve 3, and a polygon mirror support ring 6 is attached to the outer edge of the flexible flat plate member 5.
The flexible flat plate member 5 allows the polygon mirror 7 to tilt freely in the vertical direction, but does not move in the radial direction due to the rigidity along the plane of the flat plate member 5. ing. A polygon mirror 1 having a plurality of mirror surfaces 7-1 on its outer periphery is fixed to a polygon mirror holding ring 6.

Therefore, the rotational force of the motor 1 rotates the polygon mirror 7 and the window 1
The light beam A entering from the window 1 is deflected by the mirror surface 7-1 of the polygon mirror 7 onto a plane that includes the light beam A and is perpendicular to the plane of the paper.
1 and then emitted. On the other hand, the lower surface of the polygon mirror 7 is the reference plane 7.
-2, it is formed into a flat surface with the upper surface serving as a second reference surface 7-3. Opposed to the reference surfaces 7-2, 7-3, the sealed case 9 sealing the stationary polygon mirror 7 has a float member 10 whose surface facing the reference surfaces is formed into a spherical surface.
are fixed at three equal intervals on the circumference with 0-' as the center axis. The fluid (air in the embodiment) near the reference surface 7-2 of the polygon mirror 7 generates a flow as the polygon mirror 7 rotates, and is formed by the reference surfaces 7-2, 7-3 and the upper surface of the float member 10. pushed into a narrow wedge-shaped gap. Due to the action of the viscosity of this fluid, the reference surface 7-2 and the float member 1
0, a fluid pressure P'' is generated in a direction to separate the two. Since the float member 10 is fixed to the sealed case 9, the polygon mirror 7 is lifted up by the fluid pressure.

Now, a machining error in the shaft 2 or an error in the bearing 12 causes the shaft 2 to wobble as it rotates, causing the polygon mirror 7 to tilt. However, since the polygon mirror 7 is firmly held by the balance between fluid pressure and weight and maintains a constant floating amount, the shaft 2
The deflection is absorbed by the bending of the flexible flat plate member 5. Therefore, the polygon mirror 7 rotates almost unaffected by errors in the shaft 2, the bearing 12, etc., and a highly accurate optical deflection device can be obtained. However, the first
As shown in the figure, when the space is sealed only by the space in which the rotating polygon mirror rotates, the pressure at the central portion where the rotating shaft is located decreases, and the pressure at the outer periphery of the rotating polygon mirror increases.

Further, since there is no passage for the fluid sent to the outer circumference to flow smoothly, the flow is disturbed at the outer circumference, which adversely affects the rotation of the rotating polygon mirror 7, and the incoming and outgoing light beams fluctuate. An object of the present invention is to provide an optical deflection device that eliminates the above-mentioned drawbacks.

The present invention will be explained in detail below using the drawings.

FIG. 2 is a side sectional view of an embodiment of the present invention, and FIG. 3 is a top view of the optical deflection device taken along the line XX'' in FIG. 2. Note that the same numbers as in FIG. 3 have the same function. In Fig. 3, the luminous flux A is
1, is reflected by the mirror surface 7-1, and is emitted from the exit window 1 in the direction of the arrow ZA.

Inside the sealed case 9, which isolates the optical deflection device from the outside air and prevents dust from entering the deflection device from the outside, there is a partition wall 8- facing the rotating polygonal mirror reference surfaces 7-2 and 7-3. 1,
8-2 is provided, and the rotating polygon mirror body 7 separates the polygon mirror rotation space from the flow passages 14 and 15, which are other spaces.

Reference surface 7 of the rotating polygon mirror 7 on the partition walls 8-1 and 8-2
A plurality of float members 10 are fixed at equal intervals concentrically with the rotating shaft 2 at positions facing the rotating shaft 2 and 7-3. Further, a plurality of first through holes 16 are formed outside the positions where the float members 10 are fixed in the partition walls 8-1 and 8-2, and a plurality of second through holes 17 are formed inside the partition walls 8-1 and 8-2. In this configuration, when the motor 1 is driven, the rotating shaft 2 rotates in the direction of arrow B, and the rotating polygon mirror body 7 rotates in the direction of arrow B via the flexible flat plate member 5.

As the rotating polygon mirror 7 rotates, the fluid in the polygon rotation space 13 moves outward from the central rotating shaft portion in the direction of arrow C along the rotating polygon reference surfaces 7-2 and 7-3. The flow spirals between the float member 10 and the rotating polygonal mirror reference surface 7-2.
, 7-3 are opposed to each other because the flow cross-sectional area is partially reduced, so the pressure of the fluid increases, pushing the rotating polygonal mirror reference surface higher than the surface of the float member 10. With the above configuration, the fluid flowing out to the outer circumference of the rotating polygon mirror smoothly flows into the low pressure flow passages 14 and 15 through the first through hole 16, and on the other hand, due to the flow of the fluid to the outer circumference, The fluid in the flow passages 14 and 15 flows through the second through hole 17 into the center rotation shaft portion of the polygon mirror rotation space 13 where the pressure has decreased, and as the polygon mirror 7 rotates, the fluid flows naturally. In addition, the fluid circulates smoothly. Therefore, stable rotation of the polygon mirror 7 can be obtained without causing any turbulence in the flow of fluid at the outer peripheral portion. FIG. 4 shows a side sectional view of another embodiment of the invention.

Components in FIG. 4 with the same numbers as in FIG. 2 have similar functions. In FIG. 4, reference numeral 18 denotes a filter having fine holes that are fitted into the second through hole 17 and allow only fluid to pass therethrough. The filter 1
Reference numeral 8 is a device for removing dust that has entered the sealed case 9 during assembly and dust generated during rotation. The dust may enter between the float member 10 and the rotating polygon mirror reference surfaces 7-2 and 7-3 and cause scratches on both surfaces, or may adhere to the polygon mirror surface 7-1 and deteriorate the reflection characteristics of the mirror surface 7-1. There are some that have a serious effect on the performance of the deflection device, such as deteriorating the performance of the deflection device. However, by constructing it as shown in FIG. 4, dust is removed and the interior of the polygon mirror rotation space 13 is cleaned, thereby eliminating the above-mentioned drawbacks. In addition, there is a second through hole 1 in the second through hole 16 portion.
It is possible to completely prevent dust that has entered the flow path from entering the polygon mirror rotation space 13 again by fitting a filter that is coarser than the filter fitted in the filter 7, but the penetration of the outer periphery This can be prevented by making a large number of sufficiently small holes. Furthermore, in this embodiment, the filter 18 is provided in the second through hole 17 portion, but the purpose can be achieved even if the filter 18 is provided anywhere within the fluid flow passages 14 and 15. Since the filter 18 is provided in the second through hole 17 through which the fluid flows into the polygon mirror rotation space 13, the dust removal effect is very large. or,
Furthermore, in this embodiment, the substrate on which the float member is attached is described as having a structure that also serves as a partition wall that separates the space in which the rotating polygon mirror rotates from other spaces and forms a fluid flow path, but this is not provided separately. The effect is no different.

Further, in this embodiment, the float members are provided on both polygon mirror reference surfaces, but they may be provided only on one side, and it is also possible to provide a fan or the like on one side to increase the pressure exerted by the fluid.

Furthermore, it is also possible to apply a pressing force from one side using an elastic member or the like instead of using a fluid. As described above, according to the device of the present invention, the fluid circulates naturally and smoothly within the deflection device as the rotating polygon mirror rotates, thereby disturbing the rotation of the rotating polygon mirror and causing fluctuations in input and output light. Moreover, by providing a filter member in the fluid circulation path, it may enter the minute gap between the float member and the reference surface of the rotating polygon mirror, damaging both surfaces and seriously affecting the performance of the deflection device. In order to remove dust from the rotating polygon mirror chamber, it is possible to use a simple structure, inexpensively, and reliably by using structural members inside the deflection device that would otherwise require an attached device, such as supplying clean fluid from outside the deflection device. It is possible to achieve this goal.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of an optical deflection device in which errors in the rotating shaft and bearings have been removed, Fig. 2 is a side sectional view of an embodiment of the present invention, and Fig. 3 is a top view of the device shown in Fig. 2; Figures 4 and 4 respectively show side sectional views of other embodiments of the present invention. In the figure, 1 is the motor, 2 is the rotating shaft, 3 is the sleeve, and 5
is a flexible flat plate member, 6 is a polygon mirror support ring, 7 is a rotating polygon mirror, 7-2 and 7-3 are reference planes, 8 is a partition wall, 9 and 9'' are a sealed case, 10 is a float member, and 12 is a 13 is a polygonal mirror rotation space; 14 and 15 are flow paths; 16 is a first through hole; 17 is a second through hole; and 18 is a filter.

Claims (1)

[Claims] 1. A polygon mirror having a reference surface and a plurality of mirror surfaces formed at a predetermined angle with respect to the reference surface is coupled to a rotating shaft by a flexible member, and A plurality of float members are fixedly provided opposite to a reference plane of the polygon mirror and apply fluid pressure to the polygon mirror when the polygon mirror is rotated, and the polygon mirror, the rotation shaft, the flexible member, and the float member are connected to each other. In addition to covering it with a sealed case to isolate it from dust in the outside air,
A partition is provided in the sealed case to separate a space in which the polygon mirror rotates from another space in order to form a flow path in which fluid generated as the polygon mirror rotates circulates in the sealed case. The optical deflection device is provided with a fluid passage portion connecting the separated spaces on the rotation axis side and the peripheral side of the polygon mirror, respectively. 2. The optical deflection device according to claim 1, wherein a filter for removing dust within the sealed case is provided in a part of the flow path.