JPH06123849A - Scanning optical device - Google Patents

Abstract

PURPOSE:To prevent the distortion in the pedestal of a scanning optical device. CONSTITUTION:The pedestal 11 is not moved in the direction of Z but moved only in the direction of X, by supporting the pedestal 11 on the supporting part 18a of a supporting member 18, housing a spring 23 and a ball 24 into the holder part 21b of a fixing member 21 successively and fixing the fixing part 21a of the fixing member 21 to the supporting member 18 so that the ball 24 is confronted with the supporting part 18a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a laser beam printer or the like for deflecting laser light with a rotating polygon mirror,
The present invention relates to a scanning optical device that scans a surface of a photoconductor through a scanning lens.

[0002]

2. Description of the Related Art Conventionally, a scanning optical device of this type is designed to obtain a desired image by modulating the intensity of the laser light into an image signal while scanning the laser light within a predetermined range of the surface of the photoreceptor at a high speed. It has become.

For example, as shown in FIG. 6, a laser beam emitted from a light source 1 is deflected at a constant angular velocity by a rotary polygon mirror 3 mounted on a motor 2, and a lens group 4a composed of an f-θ lens system, The scanning surface 5 is scanned at a constant speed while being focused by 4b. In addition, the lens groups 4a and 4
b is fixed to the pedestal 6 made of the same rigid body with an adhesive, or is clamped by a pressure contact member fixed to the pedestal 6 with screws or the like. The pedestal 6 is manufactured from various materials such as synthetic resin, aluminum, iron-based, zinc-based, etc., and is fixed to the support member 8 by screws 7 at three positions.

The lens groups 4a and 4b are required to have different refracting power in the direction parallel to the scanning surface 5 and different refracting power in the direction perpendicular to the scanning surface 5 depending on the incident angle of laser light. Are manufactured with extremely high precision and are arranged with extremely high precision optically.

[0005]

However, although the above-mentioned conventional example is suitable for a small printer or the like, in a large printer for the purpose of high image quality and high speed, the rotary polygon mirror 3 becomes large. There is a drawback in that the power consumption of the motor 2 for rotating the rotary polygon mirror 3 increases, and the amount of heat generated also increases accordingly, and the pedestal 6 is easily distorted.

For example, the pedestal 6 has a linear expansion coefficient of 6.6 × 10.
Fabricated from ^-5 / ° C. of polycarbonate, when the pitch between the screws 7 is 200mm, the Atsushi Nobori is 20 ° C. in the vicinity of the motor 2, the Atsushi Nobori of the outer peripheral portion away from the motor 2 to 3 ° C., The average temperature rise is (20 + 3) /2=11.5° C., and the expansion amount of the pedestal 6 due to this temperature rise is (6.6 × 10
^{−5 /} ° C.) × 200 mm × 11.5 ° C. = 0.152 mm. Here, since the temperature rise of the support member 8 is approximately 0 ° C.,
Only the pedestal 6 will expand by 0.152 mm.

When the pedestal 6 expands in this manner, the fixing portions 6a, 6a of the pedestal 6 are fixed by the screws 7, 7 as shown in FIG. Will be distorted. When the pedestal 6 is distorted, the reflection position 3a of the laser light on the rotary polygon mirror 3 changes to the reflection position 3b, and the scanning position 5a of the laser light on the scanning surface 5 changes to the scanning position 5b as shown in FIG. Will be lost.

Generally, the amount of strain of the pedestal 6 is proportional to the amount of temperature rise of the motor 2, and the temperature rise of the motor 2 starts about immediately after energization and is about 3
When it is saturated after the elapse of time, the scanning position 5a gradually moves in the direction of the scanning position 5b, and after about 3 hours, moves to the scanning position 5b with the maximum distortion amount. When the scanning position changes with time in this way, the writing position of the image and the color shift change with time, and the image is significantly deteriorated. Further, when the scanning position changes, the writing position of the image also changes, which deteriorates the quality of the image and increases the scan line curve. Further, in a color printer that obtains a color image by superimposing a plurality of laser beams, color misregistration occurs.

An object of the present invention is to solve the above-mentioned problems and to provide a scanning optical device in which the optical axis does not shift even when the temperature rises.

[0010]

A scanning optical device according to the present invention for achieving the above object comprises a light source for generating a laser beam, a rotary polygon mirror for deflecting the laser beam, and a deflected laser beam for exposure. In a scanning optical device including an optical system for forming an image on a body surface, a positioning member that positions the scanning optical device in a plane parallel to a scanning plane of laser light, and a movement of the scanning optical device parallel to the plane. And a fixing member that allows the direction and blocks in the direction perpendicular to the plane.

[0011]

In the scanning optical device having the above-mentioned structure, the positioning member for positioning the scanning optical device in the plane parallel to the scanning plane of the laser beam and the movement of the scanning optical device in the direction parallel to the plane, Since the fixing member for blocking in the direction perpendicular to the plane is provided, the scanning optical device moves only in the direction parallel to the plane and does not move in the direction perpendicular to the plane.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a block diagram of a scanning optical device according to the first embodiment, for example, a pedestal 11 made of a synthetic resin material.
A laser light source 12 is fixed on the optical axis L1 in the traveling direction of the laser light emitted from the laser light source 12, and a motor 14 having a rotary polygon mirror 13 is fixed on the optical axis L1. The lens groups 15a and 15b forming the f-θ optical system are arranged in the. As shown in the sectional view of FIG. 2, two positioning pins 16 and 17 are attached to the lower surface of the pedestal 11 in a direction perpendicular to the optical axis L2 of the scanning center, and the positioning pin 16 is formed on the support member 18. The positioning pin 17 is fitted in the fitted fitting hole 19 so as to be movable in the longitudinal direction in the fitting elongated hole 20.

Here, the fitting hole 19 is provided near the optical center when the rotary polygon mirror 13 deflects and scans the laser light, and the fitting long hole 20 is parallel to the scanning plane of the deflected and scanned laser light. It is provided on the center optical axis L2 in a plane.
By fitting the positioning pins 16 and 17 into the fitting hole 19 and the fitting long hole 20 positioned in this way, the pedestal 1
1 is positioned with respect to the support member 18.

On the other hand, the pedestal 11 positioned on the support member 18 is fixed to the support member 18 at three points via a fixing member 21. As shown in FIG. 3, the fixing member 21 has a fixing portion 21 a fixed to the supporting member 18 with screws 22.
And a cylindrical holder portion 21b for accommodating the spring 23 and the ball 24. In addition, the support member 18 is provided with hemispherical support portions 18a that bulge upward at three locations. The pedestal 11 is supported on such a supporting portion 18a, and the balls 24 sandwich the pedestal 11 to support the supporting portion 1a.
A fixing member 21 is fixed to the supporting member 18 so as to face the 8a.

In such a structure, when the temperature in the vicinity of the motor 14 rises, the pedestal 11 thermally expands around the fitting hole 19 toward the peripheral portion. At this time, the ball 24
Is urged in the direction of the pedestal 11 by the spring 23, the pedestal 11 is not pushed by the balls 24 and does not float in the Z direction. At the same time, the pedestal 11 has a ball 24
By rolling, it is free to move in the X direction and is not distorted. Further, since the fixing member 21 is also arranged in the vicinity of the laser light source 12, the laser light source 12 does not float in the Z direction, and the expansion direction of the pedestal 11 is the optical axis.
Since it coincides with the direction of L2, the optical performance such as fθ characteristic and single magnification does not deteriorate.

FIG. 4 is a sectional view of the second embodiment, in which the spring 2 is provided in the holder portion 25b of the fixing member 25.
6 and the slider 27 are accommodated. Also in this embodiment, since the slider 27 is biased by the spring 26, the pedestal 11 does not float in the Z direction. Also,
The pedestal 11 slides on the tip of the slider 27 to freely move in the X direction and is not distorted.

FIG. 5 is a sectional view of the third embodiment. Here, a threaded portion 28a is provided at the tip of a rod-shaped holder portion 28b of the fixing member 28. Further, the screw portion 28a is fitted on the holder portion 28b with the spring 29 and the slider 30, and then penetrates through the hole 11a formed in the pedestal 11 and is screwed into the support member 18. Here, the diameter φD of the hole 11a
Is larger than the diameter φd of the holder portion 28b and is a value that takes into account the amount of movement of the pedestal 11 due to thermal expansion. Therefore, the hole 11a cannot be used for positioning the pedestal 11, but can sufficiently absorb the amount of expansion.

Also in this embodiment, since the slider 30 is biased by the spring 29, the pedestal 11 is attached to the slider 3.
It is not pressed by 0 and does not float in the Z direction. Further, the pedestal 11 slides on the surface of the slider 30,
There is no distortion by moving freely in the X direction.

[0019]

As described above, since the scanning optical device according to the present invention moves only in the direction parallel to the scanning plane of the laser light and does not move in the direction perpendicular to the plane, it may be distorted due to temperature rise. There is no deviation of the optical axis of the laser light.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment.

FIG. 2 is a partial cross-sectional view.

FIG. 3 is a sectional view of a fixed portion.

FIG. 4 is a sectional view of a fixing portion according to a second embodiment.

FIG. 5 is a sectional view of a fixing portion according to a third embodiment.

FIG. 6 is a plan view of a conventional example.

FIG. 7 is a sectional view of a conventional example.

FIG. 8 is a sectional view of a conventional example.

[Explanation of symbols]

 11 pedestal 13 rotating polygon mirror 16, 17 positioning pin 18 support member 19 fitting hole 20 fitting long hole 21, 25, 28 fixing member 23, 26, 29 spring 24 ball 27, 30 slider

Claims (3)

[Claims] 1. A scanning optical device comprising a light source for generating a laser beam, a rotary polygon mirror for deflecting the laser beam, and an optical system for forming an image of the deflected laser beam on a surface of a photoconductor, the position of the scanning optical device. And a fixing member for allowing the movement of the scanning optical device in a direction parallel to the plane and preventing the movement of the scanning optical device in a direction perpendicular to the plane. Characteristic scanning optical device. 2. The scanning optical device according to claim 1, wherein the fixing member is provided near the light source. 3. The positioning member is provided at two locations, one of which is provided near the optical center of the laser light reflection position of the rotary polygon mirror, and the other of which is provided to scan the optical axis of the laser light deflected from the optical center. The scanning optical device according to claim 1, wherein the scanning optical device is provided so as to move in a direction parallel to the optical axis and not in a direction perpendicular to the optical axis on the center.