JPH10232361A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the rigidity and dustproof property of an optical box and to prevent its optical performance from being deteriorated by the vibration of a lens by providing the optical box with a first rib surrounding the periphery of the lower part of the lens, covering the lower part of the lens and preventing dust and a second rib along the outside of the first rib. SOLUTION: The first rib 20a is provided on the optical box along a lower end periphery of an fθ lens, and further, the second rib 20b is provided on the outside of the first rib 20a, and the intrusion of the dust is prevented further by these ribs 20a, 20b. A beam L scanned by a polygon mirror 24 is converged by the lens, and since a plane tilt shown by beams L', L" caused by the polygon mirror 24 are corrected, and since its width X is reduced to the width X' on the position of the second rib 20b of the outside, the height of the second rib 20b is heightened to h2. Thus, the dust D hardly become close to the fθ lens, and the intrusion of the dust D is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device having a rotary driving means such as a rotary polygon mirror in a laser beam printer or the like.

[0002]

2. Description of the Related Art FIG. 7 shows a configuration of an optical system of a conventional scanning optical device, and shows a single point light source 1 which is a semiconductor laser light source.
A collimator lens 2, an aperture stop 3, a cylindrical lens 4, and a polygon mirror 5 are sequentially arranged in front of the polygon mirror 5. The polygon mirror 5 is fixed to a scanner motor and rotates at a high speed in the direction of arrow a. .

An fθ lens composed of a spherical lens 7 and a toric lens 8 and a photosensitive drum 9 are arranged in the reflection direction of the polygon mirror 5, and an image between the toric lens 8 and the photosensitive drum 9 is not effective. A fixed mirror 10 is arranged on the irradiation optical path of the light beam of the section, and a condenser lens 11 and a timing detection sensor 12 are arranged in the reflection direction of the fixed mirror 10.

The laser light from the light source 1 is emitted while diverging, passes through a collimator lens 2, is converted from a divergent light beam into a parallel light beam, passes through an aperture stop 3, and a beam shape is determined according to the stop shape. This light beam is transmitted through the cylindrical lens 4 and converged only in one direction, and is condensed linearly on the polygon mirror 5. The light beam reflected by the deflecting / reflecting surface 5a of the polygon mirror 5 is deflected and scanned at high speed with the rotation of the scanner motor 6, passes through the spherical lens 7 and the toric lens 8, and becomes minute on the photosensitive drum 9. Form an image on a spot.

The light beam deflected and scanned at a constant angular speed by the polygon mirror 5 is converted into a light spot scanned at a constant speed on the photosensitive drum 9 by passing through an fθ lens, and is converted into an arrow b direction. Is repeatedly scanned. At this time, if there is a division error in the deflecting / reflecting surface 5a of the polygon mirror 5, the timing at which the scanning information is repeatedly written is shifted, so that the leading light beam deflected and scanned by each deflecting / reflecting surface 5a is detected. . The light beam in the image non-effective portion is reflected by the fixed mirror 10 and guided to the timing detection sensor 12 via the condenser lens 11.

[0008] As shown in FIG. 8, these components of the scanning optical device are housed in an optical box 13, and a lid 14 is attached to the optical box 13. At this time, an elastic member 15 such as maltprene is placed on the spherical lens 7 or the toric lens 8 in order to prevent dust from entering from outside, and the elastic member 15 is sandwiched by the lid 14. .

[0007]

However, in the above-mentioned conventional example, it is necessary to rotate the polygon mirror 5 at a higher speed in order to meet the demand for a printer with higher definition and higher speed. Dust that has entered from the outside adheres to the effective deflection reflection surface 5a, and the reflectance is reduced, and image defects are likely to occur. For this reason, it is necessary to completely seal the optical box 13, and measures have been taken for a portion with a large gap in the path of dust entering the polygon mirror 5 from the outside. Sufficient attention has not been paid to the part of the optical box 13 where the gap is extremely small.

Further, there is a problem that the optical box 13 is vibrated by rotating the polygon mirror 5 at a higher speed, and image vibration is caused by the vibration of the fθ lens.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a scanning optical device in which dust resistance is improved, rigidity of an optical box is improved, and deterioration of optical performance due to vibration of a lens is prevented.

[0010]

A scanning optical apparatus according to the present invention for achieving the above object comprises a light source unit, a deflector for deflecting a light beam from the light source unit, and a light beam deflected by the deflector. In a scanning optical device having a lens that condenses light on a predetermined surface, and an optical box for attaching the light source unit, the deflector, and the lens, the optical box is provided with a first rib that surrounds a lower part of the lens, The first rib is provided outside the first rib.
A second rib is provided along the rib.

[0011]

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 plan view of a scanning optical device according to a first embodiment, and an optical box 20 is provided similarly to the conventional example.
Inside, a collimator lens 22 that converts a light beam into a parallel light beam, and a cylindrical lens 23 that condenses the parallel light beam into a linear shape are arranged on an optical path in front of the semiconductor laser light source 21, and a light beam that is formed by being condensed is formed. In the vicinity of the line image, a polygon mirror 24 having a deflecting / reflecting surface 24a;
A scanner motor 25 for rotating the polygon mirror 24 is provided.

An fθ lens 26 and a reflection mirror 27 are arranged in the reflection direction of the polygon mirror 24. f
The θ lens 26 has a spherical lens 26a and a toric lens 2
6b, and a polygon mirror 24
The light beam reflected by the deflecting / reflecting surface 24a is condensed so as to form a spot on the photosensitive member, and the scanning speed of the spot is kept constant. In addition,
Recently, a lens in which these two lenses 26a and 26b are made into one using plastic is also used.

On the outside of the box frame of the optical box 20, positioning pins 28a and 28b for adjusting a light beam irradiation position of the scanning optical device, and respective guide holes 29a and 29b.
Is provided.

A light beam from the semiconductor laser light source 11 is deflected and reflected by a deflecting / reflecting surface 24a of a polygon mirror 24, enters a reflecting mirror 27 via an fθ lens 26, is reflected by the reflecting mirror 27, and is reflected on a photosensitive member (not shown). Irradiated.
At this time, the main scanning by the light beam is performed on the photoreceptor by the rotation of the polygon mirror 24, and the sub-scanning is performed by rotating the photoreceptor around the axis of the cylinder. Thus, an electrostatic latent image is formed on the surface of the photoconductor.

Although not shown, a corona discharger which uniformly charges the surface of the photoreceptor is provided around the photoreceptor,
A visualization device that visualizes the electrostatic latent image formed on the surface of the photoconductor into a toner image, a transfer corona discharger that transfers the toner image to recording paper, and the like are arranged. Recording information corresponding to the light beam generated by the semiconductor laser light source 21 is printed on recording paper.

Further, the adjustment of the irradiation position of the scanning optical device is as follows.
The positioning is performed by the positioning pins 28a and 28b. The adjustment of the irradiation position in the X direction of the scanning optical device is performed by moving the positioning pins 28a and 28b in the same direction along the X direction, and the adjustment of the scanning optical device in the θ direction is performed by adjusting the positioning pins 28a and 28b respectively. The rotation is performed by moving in opposite directions along the X direction.

FIG. 2 is a plan view showing the vicinity of the fθ lens 26. The optical box 20 is provided with a first rib 20a along the periphery 26a of the lower end of the fθ lens 26, and further provided outside the first rib 20a. A second rib 20b is provided,
These ribs 20a and 20b further prevent dust from entering.

FIG. 3 is a sectional view showing the polygon mirror 24.
The beam L scanned by has the width X in the vicinity of the fθ lens 26, so that the inner first rib 20a
Is limited to height h1. However, the beam L is fθ
The light is condensed by a lens 26 and further
Is corrected at the position of the outer second rib 20b, the width X is reduced to the width X 'at the position of the outer second rib 20b, and the height of the second rib 20b is reduced. In this manner, by making the height of the second rib 20b higher than that of the first rib 20a, the dust D becomes difficult to approach the fθ lens 26, and f
Intrusion of dust D into the gap G between the θ lens 26 and the optical box 20 can be reduced.

FIG. 4 is a plan view of the second embodiment, and FIG.
FIG. 4 shows a cross-sectional view of the vicinity of the lens 26. The fθ lens 26 is supported at both ends by fixed springs 30, and the fixed spring 30 is a third rib 20c protruding from the optical box 20.
Lens 26 is pressed between fθ lens 26 and fθ lens 26, and one end of the fixed spring is connected to convex portion 2 of third rib 20c.
It is fixed by hooking on 0d.

Although such a fixed spring 30 is effective in terms of cost and space, the first rib 20a is cut off at both ends as shown in FIG.
The first rib 20a needs to be provided continuously and fully to the wall surfaces 20e to 20f of the optical box 20 so as to compensate for the cut portion of the first rib 20a.

As described above, the wall surfaces 20 e to 2 e of the optical box 20 are
By providing the second rib 20b continuously up to 0f, the rigidity near the fθ lens 26 can be improved. Further, the second rib 20b is made higher than the first rib 20a, and the fθ lens 26 Optical performance can be improved by suppressing nearby vibrations.

When space is allowed in the optical box 20, as shown in the sectional view of the third embodiment in FIG.
The fifth ribs 20g, 20h are replaced with the first and second ribs 20a,
By providing the optical box 20 substantially in parallel, the dustproof property and the rigidity of the optical box 20 can be further improved.

[0023]

As described above, the scanning optical apparatus according to the present invention has the first rib surrounding the lower part of the lens and covering the lower part of the lens to prevent dust, and extends along the outside of the first rib. By providing the second rib in the optical box, the rigidity and dustproofness of the optical box can be improved, and the optical performance can be prevented from deteriorating due to vibration of the lens.

[Brief description of the drawings]

FIG. 1 is a plan view of a scanning optical device according to a first embodiment.

FIG. 2 is a plan view near an fθ lens.

FIG. 3 is a sectional view.

FIG. 4 is a plan view of a second embodiment.

FIG. 5 is a sectional view.

FIG. 6 is a sectional view of a third embodiment.

FIG. 7 is a perspective view of a conventional scanning optical device.

FIG. 8 is a cross-sectional view around the fθ lens.

[Explanation of symbols]

 Reference Signs List 20 optical box 20a, 20b, 20c, 20g, 20h rib 21 semiconductor laser light source 24 polygon mirror 26 fθ lens 27 reflecting mirror 28a, 28b positioning pin 30 fixing spring

Claims (4)

[Claims] 1. A light source unit, a deflector for deflecting a light beam from the light source unit, a lens for condensing the light beam deflected by the deflector on a predetermined surface, and mounting the light source unit, the deflector, and the lens A scanning optical device having an optical box, wherein the optical box is provided with a first rib surrounding a lower portion of the lens, and a second rib is provided outside the first rib along the first rib. A scanning optical device, comprising: 2. The scanning optical device according to claim 1, wherein the height of the second rib is larger than that of the first rib. 3. The optical box according to claim 1, wherein at least one of the first and second ribs is continuous at substantially the same height from one wall to the other wall of the optical box. Scanning optics. 4. The scanning optical device according to claim 1, wherein a plurality of ribs are provided along the second rib outside the second rib.