JPH0943526A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent rapid contamination of the reflection surface of a rotary polygonal mirror with dust by providing a dustproof means, for preventing the dust from entering into a prescribed air space section of an optical box between an image forming lens and a cover. SOLUTION: This device is provided with an optical source unit, a rotary polygonal mirror 1 which deflection-scanns a laser beam L1 and an image forming lens 2 which forms the deflection-scaned laser light L1 on a photoreceptor provided on the surface of a rotating drum. The mirror 1 and the lens 2 are housed in an optical box 3 and the optical source unit is assembled to the side wall of the box 3. Moreover, the upper opening of the box 3 is closed by a cover 4 after all necessary parts are assembled into the box 3. A packing material 5, which is dustproof means, is filled in a gap S between the upper end of the lens 2 and the cover 4 so as to prevent the dust from entering into the atmosphere surrounding the mirror 1. The material 5 is made of an elastic material and is held in a holding groove 21 provided on the upper end of the lens 2.

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 used in an image forming apparatus such as a laser beam printer or a laser facsimile.

[0002]

2. Description of the Related Art A scanning optical device used in an image forming apparatus such as a laser beam printer or a laser facsimile generally has a light source unit E having a semiconductor laser and a collimator lens as a unit, as shown in FIG. A rotary polygon mirror R for deflecting and scanning the laser beam L ₀ of the parallel light flux thus formed, an imaging lens F for focusing the deflected and scanned laser light on a photoconductor on the surface of a rotating drum (not shown), and the like,
The rotating polygon mirror R and the imaging lens F are housed in the optical box H, and the light source unit E is mounted on the side wall of the optical box H or the like.

The upper opening of the optical box H has a lid P as shown in FIG.
Is blocked by. The side wall of the optical box H is provided with a window M for taking out the laser beam deflected and scanned by the rotary polygon mirror R toward an external rotary drum.

The laser light L ₀ generated from the semiconductor laser of the light source unit E is collimated by the collimator lens inside the light source unit E, is linearly focused on the reflecting surface of the rotary polygon mirror R by the cylindrical lens C, and forms an image forming lens. After passing through F, it is taken out from the window M of the optical box H toward the rotary drum. In this way, the laser light imaged on the photoconductor on the rotating drum forms an electrostatic latent image by the main scanning by the rotating polygon mirror and the sub-scanning by the rotation of the rotating drum.

[0005]

However, according to the above-mentioned conventional technique, as described above, the upper opening of the optical box is closed by the lid, and the rotary polygon mirror and the imaging lens are prevented from being contaminated by dust or the like. Although it is designed to prevent this, outside air flows into the optical box through a window for extracting laser light from the optical box toward the rotating drum, and passes through the gap formed between the imaging lens and the lid. It is unavoidable that the rotary polygon mirror is contaminated by mixing with the atmosphere around the rotary polygon mirror. In particular, the reflecting surface of the rotating polygon mirror that rotates at high speed is in a state where dust is extremely likely to adhere due to friction with the surrounding air, and when the reflecting surface of the rotating polygon mirror is contaminated and its reflectance decreases, scanning The performance of the optical device is greatly impaired.

The present invention has been made in view of the above-mentioned problems of the prior art, in which the reflecting surface of the rotary polygon mirror is abruptly changed due to dust entering through between the imaging lens and the lid. It is an object of the present invention to provide a scanning optical device which prevents contamination and has a low maintenance cost of a rotary polygon mirror and which is suitable for high speed operation.

[0007]

To achieve the above object, a scanning optical apparatus according to the present invention comprises a rotating polygon mirror and at least one image forming means for forming an image of a light beam deflected and scanned by the rotating polygon mirror on a photosensitive member. A lens, an optical box for accommodating the rotary polygon mirror in a predetermined space, and a lid for closing the opening thereof, and between the imaging lens and the lid, in the predetermined space of the optical box. It is characterized in that a dustproof means is provided to prevent dust from entering.

The image forming lens may be provided with a holding groove for holding the dustproof means.

It is preferable that the image forming lens is provided with a recess opposite to the holding groove.

The imaging lens is preferably a plastic lens.

[0011]

When dust or the like of the outside air enters the atmosphere around the rotary polygon mirror through the gap between the imaging lens and the lid, the reflecting surface of the rotary polygon mirror is contaminated and the optical characteristics of the scanning optical device deteriorate. Therefore, a dustproof means such as a filler is provided between the imaging lens and the lid to prevent the reflection surface of the rotary polygon mirror from being contaminated. If the holding groove for holding the dustproof means is provided at one end of the imaging lens, the dustproof means can be easily assembled. Further, by providing a recess opposite to the holding groove at the other end of the imaging lens to prevent the cross section of the imaging lens from becoming asymmetric, deterioration of the optical characteristics of the imaging lens due to internal distortion can be avoided. In this case, the optical characteristics of the scanning optical device can be greatly improved. In particular, if the imaging lens is a plastic lens, the holding groove can be formed in the step of integrally molding the plastic lens, so the manufacturing process is simple, but if the holding groove makes the cross section of the imaging lens asymmetrical, Internal strain at the time of molding is remarkably increased, and optical characteristics are significantly impaired. Therefore, it is extremely important to provide a concave portion opposite to the holding groove to prevent the cross section of the imaging lens from becoming asymmetrical in order to secure the optical characteristics required for the plastic imaging lens.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

1A and 1B show a scanning optical device according to one embodiment, FIG. 1A is a schematic sectional view thereof, and FIG. 1B is an enlarged partial schematic sectional view showing a part of FIG.

This scanning optical device includes a light source unit (not shown) in which a semiconductor laser and a collimator lens are unitized, a rotary polygon mirror 1 for deflecting and scanning a laser beam L ₁ which is a light beam of a parallel light beam generated from the unit, and a deflecting unit. It has an image forming lens 2 for forming an image of the scanned laser beam L ₁ on a photoconductor on the surface of a rotating drum (not shown), and the rotary polygon mirror 1 and the coupling lens 2 are housed in an optical box 3, and the light source unit is also provided. Is attached to the side wall of the optical box 3 or the like.

The upper opening of the optical box 3 is closed by a lid 4 after incorporating all the necessary parts in the optical box 3. Note that window 4a for extracting toward the laser light L ₁ that has been deflected and scanned by the rotary polygon mirror 1 to the outside of the rotary drum is provided on the side wall of the optical box 3.

A laser beam L ₁ generated from a semiconductor laser of a light source unit is collimated by a collimator lens therein, and is linearly condensed on a reflecting surface 1a of a rotary polygon mirror 1 by a cylindrical lens (not shown) to form an image. It is taken out from the window 4a of the optical box 3 through the lens 2 toward the rotary drum. In this way, the laser light imaged on the photoconductor on the rotary drum forms an electrostatic latent image by main scanning by the rotary polygon mirror 1 and sub-scanning by rotation of the rotary drum.

The imaging lens 2 is a scanning light L of the rotary polygon mirror 1.
₁ is a plastic lens having a so-called fθ function for correcting the distortion of the point image formed on the photoconductor, and by the reference surface 31a of the pedestal 31 provided integrally with the bottom wall 3a of the optical box 3, The rotary polygon mirror 1 is positioned in the height direction (Z-axis direction) of the reflecting surface 1a. Also, the imaging lens 2
Is positioned in the optical axis direction (X-axis direction) by bringing the reference surface 2a of the imaging lens 2 in the X-axis direction into contact with the first positioning pin 32 protruding from the bottom wall 3a of the optical box 3. Further, as shown in FIG. 2, the positioning of the imaging lens 2 in the width direction (Y-axis direction) is performed with the Y of the imaging lens 2 on the second positioning pin 33 protruding from the bottom wall 3a of the optical box 3.
This is performed by abutting the reference surface 2b in the axial direction.

When assembling the imaging lens 2, an ultraviolet curing adhesive is applied to the bottom surface of the imaging lens 2, the imaging lens 2 is placed on the reference surface 31a of the pedestal 31 of the optical box 3, and the By bringing the reference surfaces 2a and 2b into contact with the first and second positioning pins 32 and 33, respectively, the optical axis alignment and focus adjustment of the imaging lens 2 with respect to the rotary polygon mirror 1 and the photoconductor are completed, and The adhesive is irradiated with ultraviolet rays to cure it. In addition, it is possible to use an adhesive other than the ultraviolet curing type, and it is also possible to fix the imaging lens 2 to the pedestal 31 using a leaf spring or the like without being limited to the adhesive.

A gap S between the upper end of the imaging lens 2 and the lid 4 is filled with a filler 5 which is a dustproof means in order to prevent dust or the like from entering the atmosphere around the rotary polygon mirror 1. . The filler 5 is, for example, an elastic member commercially available under the trade name Moltoprene or an elastic member made of known soft rubber, and is held in a holding groove 21 provided at the upper end of the imaging lens 2. As shown in FIG. 2, the holding groove 21 includes both end portions 21a having a width X ₂ smaller than the width X ₁ of the filling material 5,
The holding groove 21 has a central portion 21b wider than this.
By pushing both ends of the filling material 5 into both ends 21a of
The filler 5 can be stably fixed to the imaging lens 2. Further, the wall thickness Z ₁ of the filling material 5 is larger than the width Z ₂ of the gap S between the imaging lens 2 and the lid 4, and after the filling material 5 is attached to the upper end of the imaging lens 2, Box 3
When the lid 4 is fixed with screws, the filler 5
Is elastically compressed and the gap S is sealed.

Further, both side walls of the optical box 3 and the imaging lens 2
The space is closed by a partition wall (not shown) that is integral with the side wall of the optical box 3. That is, the internal space of the optical box 3 is
The rotating lens 1 and its drive unit 1b are formed by the imaging lens 2.
And a second space facing the window 4a.
Even if outside air flows into the optical box 3 through the window 4a, it is not divided into the first space 10a that houses the rotary polygon mirror 1. Therefore, there is no possibility that the reflecting surface 1a of the rotary polygon mirror 1 is contaminated by dust or the like in the outside air.

According to the present embodiment, the frequency of exchanging the rotating polygon mirror or cleaning the reflecting surface due to the contamination of the reflecting surface of the rotating polygon mirror can be reduced, and the maintenance cost can be greatly reduced. Particularly, when the rotary polygon mirror is rotated at a high speed, the suction force of the outside air is increased accordingly, and there is a tendency that the outside air invades even a small gap to rapidly contaminate the reflecting surface of the rotary polygon mirror. Therefore, completely preventing the atmosphere around the rotary polygon mirror from the outside air to prevent the rotary polygon mirror from being contaminated as in the present embodiment is very useful for accelerating the speedup of the scanning optical device.

Further, when the plastic lens is used as in this embodiment, the holding groove at the upper end can be formed in the step of integrally molding the plastic lens, so that it is not necessary to provide a processing step such as groove processing. Therefore, the material cost and the manufacturing cost of the imaging lens are low, which can greatly contribute to the cost reduction of the scanning optical device.

If the image forming lens is a plastic lens, it is preferable that the image forming lens has a vertically symmetrical shape when integrally molded so that the internal distortion is small and the shape accuracy is high, and the optical performance is stable. It is convenient to obtain the image forming lens. Therefore, as shown in FIG. 3, a recess 22 that is a recess opposite to the holding groove 21 is provided at the lower end of the imaging lens 2, and the bottom surface 22 a of the recess 22 is the reference surface 31 of the pedestal 31 of the optical box 3.
If it is configured to contact a, the cross-sectional shape of the imaging lens 2 becomes vertically symmetrical, which is very useful for improving the optical characteristics of the scanning optical device. When the pedestal 31 of the optical box 3 is composed of a plurality of columns, it is necessary to take measures against dust or the like that bypasses the lower end of the imaging lens 2 and enters the atmosphere around the rotary polygon mirror 1. However, if the pedestal 31 is inserted into the depressed portion 22 of the imaging lens 2 as in this modification, there is an advantage that the dust and the like can be prevented from entering due to the labyrinth effect.

[0024]

Since the present invention is configured as described above, it has the following effects.

It is possible to prevent the reflective surface of the rotary polygon mirror from being rapidly contaminated due to dust or the like that penetrates through between the imaging lens and the lid, and the maintenance cost of the rotary polygon mirror is low and the speed is high. A suitable scanning optical device can be obtained.

[Brief description of drawings]

FIG. 1 shows a scanning optical device according to one embodiment,
(A) is the schematic cross section, and (b) is an expanded partial schematic cross section which expands and shows a part of (a).

FIG. 2 is a perspective view showing only an imaging lens and a filler of the apparatus of FIG.

FIG. 3 is a partial schematic cross-sectional view showing a modified example.

FIG. 4 is a perspective view showing a conventional example.

5 is a schematic cross-sectional view showing the device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating polygon mirror 2 imaging lens 3 optical box 4 lid 4a window 5 filling material 21 holding groove 22 recessed portion

Claims (4)

[Claims] 1. A rotary polygon mirror, at least one imaging lens for forming an image of a light beam deflected and scanned by the rotary polygon mirror on a photoconductor, and an optical box for housing the rotary polygon mirror in a predetermined space. It has a lid for closing the opening, and dust-proof means for preventing dust from entering the predetermined space of the optical box is provided between the imaging lens and the lid. Scanning optical device. 2. The scanning optical device according to claim 1, wherein the imaging lens is provided with a holding groove for holding the dustproof means. 3. The scanning optical device according to claim 2, wherein the image forming lens is provided with a recess opposite to the holding groove. 4. The scanning optical device according to claim 1, wherein the imaging lens is a plastic lens.