JP2008107460A - Optical deflector and optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical deflector and an optical scanner which can reduce the number of machining processes and cost, can reduce the height and weigh, and can shorten the starting time. <P>SOLUTION: The typical composition of the optical deflector 81 includes: a plurality of polygon mirrors 42a and 42b which are turnably laminated on one and the same rotation shaft 83; light beams L emitted form a plurality of semiconductor lasers 51 are deflected and scanned with the plurality of polygon mirrors 42a and 42b, wherein the plurality of polygon mirrors 42a and 42b are characterized in being respectively different members and one of them, the first polygon mirror 42a, includes a magnet 84 for driving the optical deflector 81 and functions as a rotor frame. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical scanning device used for a laser beam printer, a digital copying machine, and the like, and an optical deflection device used therefor.

  2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic method forms a latent image by scanning a photosensitive drum having a charged surface with a light beam corresponding to image information by an optical scanning device. Then, the latent image is developed into a visible image, and the visible image is transferred to a sheet to form an image.

  As such an optical scanning device, for example, as shown in Patent Document 1, there is a configuration in which rotating polygon mirrors (hereinafter referred to as polygon mirrors) are stacked in two stages. In the optical deflecting device described in Patent Document 1, a rotor yoke (rotor frame) and two polygon mirrors are integrated, and a fitting portion and a tapered abutting portion are provided when assembled with a rotating sleeve. Thus, a device for reducing the balance fluctuation of the rotating body has been devised.

  For example, as shown in Patent Document 2, there is a configuration in which a polygon mirror and a rotor can be separated separately in a configuration in which polygon mirrors are stacked in two stages.

JP 2004-333657 A Japanese Patent Application Laid-Open No. 64-66615

  However, the optical deflection apparatus described in Patent Document 1 has the following problems.

  Since the two polygon mirrors and the rotor yoke are formed by one-piece machining, the cost increases due to a longer processing man-hour. Since two polygon mirrors whose positions are different from each other in the height direction are integrated, the workpiece must be sent to a thickness equivalent to or more than the thickness of two polygon mirrors when machining the mirror surface. For this reason, the more the optical systems in which the heights of the light beams incident on the mirror surface of the polygon mirror are separated from each other in the vertical direction, the more processing man-hours are required and the cost is increased.

  For example, when mirroring one polygon mirror at a time, if the upper and lower polygon mirrors are 3mm thick and the difference in light beam height is 7mm, the mirror finish is completed unless the workpiece is moved approximately 10mm. do not do. Since the total thickness of the polygon mirror is 6 mm, the calculation will increase by about 40%. The effect of the man-hour is more conspicuous as the number of polygon mirrors is larger, and the effect on the cost is also greater.

  Also, there is a method in which a large number of polygon mirrors are overlapped and the mirror surface is cut at a time, but the number of overlaps at a time is reduced, so that the man-hour per one is also increased. For example, it is assumed that there is a processing machine that can process 30 pieces of polygon mirrors with a thickness of 3 mm at the same time (half of the 15 optical scanning devices). As in the above example, if the upper and lower polygon mirrors are each 3 mm thick and the difference in light beam height is 7 mm, the total polygon thickness will be 10 mm, so the number of layers will be 3 mm x 30 ÷ 10 mm = 9. Since the number of optical scanning devices that can be processed in one operation is reduced from 15 to 9, it takes approximately 1.66 times more man-hours.

  There is also a method of shortening the time between the upper and lower mirror surfaces by increasing the work feed speed until one of the upper and lower mirror surfaces is finished and before moving to the other mirror surface. In that case, if the processing machine is not configured to have two feeding speeds, it is necessary to remodel the processing machine, which contributes to a cost increase due to amortization of additional investment.

  In the optical deflecting device described in Patent Document 2, the polygon mirror and the rotor yoke are separated, the number of parts increases, the height of the optical deflecting device increases, the weight increases, and the rise time of the optical deflecting device increases. There is a problem.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical deflecting device and an optical scanning device that can reduce the number of processing steps and suppress the cost increase, reduce the height and weight of the optical deflecting device, and shorten the rise time. .

  In order to solve the above problems, a typical configuration of an optical deflecting device according to the present invention has a plurality of rotating polygon mirrors that are rotatable about the same rotation axis, and are emitted from a plurality of light emitting sources. In the optical deflection apparatus that deflects and scans a light beam with the plurality of rotary polygon mirrors, the plurality of rotary polygon mirrors are different members, and one of the first rotary polygon mirrors is for driving the optical deflection apparatus. The magnet is housed inside and functions as a rotor frame.

  In order to solve the above-described problems, a typical method for manufacturing an optical scanning device according to the present invention includes a plurality of light sources, the light deflection device, and a light beam deflected and scanned by the light deflection device on an image carrier. And a lens for scanning.

  According to the present invention, the number of processing steps can be reduced and the cost can be increased, and the height and weight of the optical deflecting device can be suppressed, and the rise time can be shortened.

[First embodiment]
A first embodiment of an optical deflection apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view and a perspective view of an optical deflecting device 81 according to this embodiment. FIG. 2 is an exploded view of a rotating body used in the light deflection apparatus 81 according to the present embodiment.

  As shown in FIG. 1, the light deflection apparatus 81 includes polygon mirrors 42 a and 42 b that are rotary polygon mirrors, a drive motor 82, a rotation shaft 83, a magnet 84, a coil 85, and a bearing 86.

  Each of the polygon mirrors 42a and 42b is divided into two stages, a lower stage and an upper stage, and is overlapped so as to be rotatable about the same rotation shaft 83, and has light beam reflecting surfaces 41a and 41b. Both the polygon mirrors 42a and 42b are made of aluminum. In the present embodiment, six reflecting surfaces 41a and 41b are provided, but are not particularly limited in the present invention, and may be any number as long as they are normally used for a polygon mirror.

  The lower polygon mirror 42a (first rotary polygon mirror) is press-fitted with a rotary shaft 83 at the center, and also has a function as a rotor frame. The rotation shaft 83 is coaxial with the circumscribed circle of the polygon mirror 42a.

  On the upper surface (the upper surface in the axial direction) of the polygon mirror 42a, a reference surface 92a (a contact surface that holds the polygon mirror 42b) and a fitting protrusion 93a are provided. The fitting protrusion 93 a is coaxial with the rotation shaft 83.

  The polygon mirror 42a accommodates a cylindrical magnet 84 therein. Specifically, the polygon mirror 42a has a non-mirror surface portion P between the reflection surface 41a and the reference surface 92a, and is provided with a step corresponding to the height of the non-mirror surface portion P. Unlike the reflecting surface 41a, the non-mirror surface portion P does not require surface accuracy.

  The polygon mirror 42 a has an accommodating portion 91 inside, and a magnet 84 is bonded and fixed to the accommodating portion 91. The height of the upper surface of the accommodated magnet 84 is higher than the height of the lower surface of the polygon mirror 42a.

  The upper polygon mirror 42b (another rotating polygon mirror) is a substantially flat hexagonal prism, and is provided with a reference surface 92b and a fitting hole 93b. The fitting hole 93b is provided at the center of the polygon mirror 42b and is coaxial with the circumscribed circle of the polygon mirror 42b.

  The fitting projection 93a of the polygon mirror 42a is press-fitted into the fitting hole 93b of the polygon mirror 42b, and the polygon mirrors 42a and 42b are fixed. The coaxiality and parallelism of the two polygon mirrors 42a and 42b are satisfied by the fitting of the fitting protrusion 93a and the fitting hole 93b.

  The polygon mirrors 42a and 42b are assembled so that the reflecting surfaces 41a and 41b are parallel to each other. This is because the angles of the light beams incident on the polygon mirrors 42a and 42b are the same. When the incident angles of the light beams are different between the polygon mirrors 42a and 42b, they may be assembled so that the reflecting surfaces thereof have a predetermined angle.

  When the polygon mirrors 42a and 42b are fixed, the reference surface 92a of the polygon mirror 42a and the reference surface 92b of the polygon mirror 42b come into contact with each other, and the polygon mirror 42b is positioned in the height direction.

  The rotating shaft 83 is supported by a bearing 86, and the polygon mirrors 42a and 42b can rotate integrally around the bearing 86. The drive motor 82 is configured by assembling the coil 85 to the control board 87 and rotationally drives the polygon mirrors 42a and 42b. The control board 87 is an iron plate on which a drive circuit is formed.

(effect)
By configuring as described above, portions other than the reflection surface 41a (mirror surface) of the polygon mirror 42a can be processed by turning because they are cylindrical surfaces. When turning, the surface accuracy is not required except for the fitting protrusion 93a and the reference surface 92a with the polygon mirror 42b. Therefore, it is possible to increase the processing speed, and as a result, even if the surface accuracy is deteriorated, there is no problem.

  On the other hand, since the shape of the polygon mirror 42b is substantially flat, it is possible to improve the processing efficiency by superposing a plurality of polygon mirrors to mirror the mirror surface. At the time of processing, the number of polygon mirrors to be taken is determined only by the thickness of the polygon mirror. Although the polygon mirror 42b of the present embodiment has a substantially flat plate shape, even if there are irregularities, it is sufficient that the irregularities correspond to each other when the polygon mirrors are overlapped and do not become thicker in the thickness direction.

  Since the polygon mirrors 42a and 42b are separate bodies, the phase of each polygon can be shifted.

  Further, since the polygon mirror 42a is integrated with the rotor frame, the non-specular surface portion P can absorb the difference in the height direction compared to the configuration in which the polygon mirror is mounted on the upper surface of the rotor frame, and the height of the reflecting surface 41a is increased. Lower. As a result, the height of the center of gravity of the rotating body (polygon mirrors 42a and 42b) of the light deflector 81 can be lowered.

  In addition, since the polygon mirror 42a is integrated with the rotor frame, the mass of the rotating body can be reduced as compared with the configuration in which the polygon mirror is mounted on the upper surface of the rotor frame. As a result, the inertia during the rotation of the rotating body is reduced, the rise time until the light deflecting device 81 reaches the specified rotational speed is shortened, and the power required during the rotation is also reduced.

  Further, since the polygon mirror 42a and the rotor frame are integrally processed, the initial balance is good and the balance correction tact is shortened.

[Second Embodiment]
Next, a second embodiment of the optical deflection apparatus according to the present invention will be described with reference to the drawings. FIG. 3 is a cross-sectional view showing an optical deflecting device 181 according to this embodiment. About the part which overlaps with said 1st embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 3, the optical deflecting device 181 is configured such that the height of the accommodating portion 91 is higher than the reference mounting surface 92a of the polygon mirror 42b in the optical deflecting device 81 of the first embodiment. It is.

  By adopting the above configuration, the accommodating portion 91 can be provided with a larger magnet 84 and a coil 85. As a result, it is possible to improve the driving force of the motor without changing the height of the optical deflector and to shorten the rise time of the motor.

(Optical scanning device)
FIG. 4 is a perspective view showing the optical scanning device 50 according to this embodiment. As shown in FIG. 4, the optical scanning device 50 includes the light deflection devices 81 and 181 of the first or second embodiment. The optical scanning device 50 includes a semiconductor laser 51, a collimating lens 54, a cylindrical lens 47, an fθ lens 43, and folding mirrors 70, 71 and 72.

  Light beams Lc to Lk emitted from the semiconductor lasers 51c to 51k, which are light emission sources, are converted into substantially parallel light by the collimating lenses 54c to 54k, are incident on the polygon mirrors 42a and 42b by the cylindrical lenses 47c to 47k, and are reflected on the reflecting surface. A line image is formed on 41a and 41b. The light beams Lc to Lk incident on the polygon mirrors 42a and 42b are reflected, deflected and scanned in two different directions.

  The deflected and scanned light beams Lc to Lk are transmitted through the fθ lenses 43c to 43k, reflected by the folding mirrors 70m, 71m, 72c, 70y, 71y, and 72k, and incident on the photosensitive drums (image carriers) 32c to 32k. To do.

  At that time, in order to determine the drawing positions of the light beams Lc to Lk, a part of the light beam Ly is turned back by the BD mirror 45 and incident on the BD sensor 46 to determine the drawing reference.

  By adopting the configuration as described above, it is possible to reduce the height of the optical scanning device 50 and shorten the rise time of the optical deflection devices 81 and 181.

2A and 2B are a cross-sectional view and a perspective view illustrating the configuration of the optical deflection apparatus according to the first embodiment of the present invention. It is the exploded view explaining the structure of the rotary body used for the optical deflection apparatus in the 1st Embodiment of this invention. It is sectional drawing explaining the structure of the optical deflection apparatus in the 2nd Embodiment of this invention. 1 is a perspective view of an optical scanning device equipped with an optical deflecting device according to a first embodiment of the present invention.

Explanation of symbols

L ... Light beams 42a, 42b ... Polygon mirror (rotating polygon mirror)
43 ... fθ lens, 47 ... cylindrical lens 50 ... optical scanning device 81, 181 ... light deflection device 83 ... rotating shaft 84 ... magnet

Claims (5)

In a light deflection apparatus that has a plurality of rotary polygon mirrors that are rotatably stacked around the same rotation axis, and deflects and scans light beams emitted from a plurality of light emission sources with the plurality of rotary polygon mirrors,
The plurality of rotary polygon mirrors are different members, and one of the first rotary polygon mirrors houses a magnet for driving the optical deflection device and functions as a rotor frame. apparatus.   2. The optical deflecting device according to claim 1, wherein, among the plurality of rotary polygon mirrors, another rotary polygon mirror that does not function as the rotor frame has a substantially flat plate shape.   2. The optical deflecting device according to claim 1, wherein the first rotary polygon mirror is provided with a contact surface for holding the other rotary polygon mirror on the upper side in the axial direction.   2. The optical deflecting device according to claim 1, wherein the height of the upper surface of the magnet is higher than the height of the lower surface of the first rotary polygon mirror. Multiple light sources;
An optical deflecting device according to any one of claims 1 to 3,
An optical scanning device comprising: a lens for scanning a light beam deflected and scanned by the light deflection device onto an image carrier.

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