JPH09236771A - Optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the adverse effect out of designing calculation to the optical characteristic by continuing to pressurize a reflection optical element on a reference mounting surface without disturbing the isotropic change in shape of the reflection optical element even when the reflection optical element is deformed due to temp. fluctuation and to prevent the deviation of the reflection optical element from a prescribed mounting position even when force with large acceleration such as the impact is exerted on an optical scanning device. SOLUTION: This device comprises a light source transmitting a light beam, a deflector deflecting/scanning the light beam from the light source, an optical element group forming the image of a reflected light beam from the deflector on the surface of a photosensitive body and houses the light source, the deflector and the optical element group in a housing 1 and a reflection optical element 5 having an image forming characteristic is used as one of the optical element group. In this case, impact absorbent materials having impact resistance are arranged on the upper surface of the reflection optical element arranged along the reference mounting surface in the housing 1 and in a clearance between the reflection optical element and the housing 1, the upper surface of the impact absorbent material is pressurized by a pressing plate 11 and the pressing plate is fixed to the housing 1 in the compressed state of the material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to an optical scanning device used in an image forming apparatus such as a laser printer or a laser facsimile, and more particularly to improvement of a support structure of a reflective optical element having an image forming characteristic.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a laser printer, a laser facsimile, etc., a laser beam emitted from an optical scanning device is radiated onto a photosensitive member which is uniformly charged in advance to be statically charged. An image is formed by forming an electrostatic latent image and transferring and fixing a toner image obtained by supplying toner to the electrostatic latent image from a developing device onto a transfer paper. The reflective optical element having an image forming characteristic such as an fθ mirror as a concave mirror achieves the optical characteristic only by the precision of the mirror surface, without being affected by the internal distortion of the element, foreign matter, etc., as compared with the transmissive optical element such as the fθ lens. Therefore, it is advantageous from the viewpoint of beam diameter, magnification error (linearity), and light utilization efficiency, and is suitable for high-density optical scanning, which has been increasingly demanded in recent years. However, on the contrary, since the optical characteristics are achieved only by the accuracy of the mirror surface, a slight change in the shape of the mirror surface has a great influence on the optical characteristics. For example, the reflective optical element may change its shape due to the temperature fluctuation of the installation environment of the device, the mirror surface of the reflective optical element may partially change due to the temperature distribution difference in the unit, or the optical characteristics (beam diameter, There is a problem that it adversely affects the magnification error). This tendency is particularly large when the material of the reflective optical element is resin.

By the way, since the design calculation of the optical characteristics is based on the hypothesis that the shape change of the reflective optical element due to the fluctuation of the environmental temperature is isotropic, a specific portion of the reflective optical element is a leaf spring or a coil spring. In the fixing method of pressing with, the reflection optical element becomes unsupported when the shape is deformed by temperature and the pressed portion serves as a fulcrum (for example, when the temperature rises, the reflection The radius R of the mirror surface of the element increases, but when both ends serve as fulcrums, R decreases, which may adversely affect the optical characteristics. Further, when the optical element is fixed to the housing with an adhesive, the central portion of the reflective optical element is adhesively fixed in consideration of the difference in linear expansion coefficient due to the difference in the materials of the reflective optical element and the housing. It is difficult to fix the long reflective optical element to the housing without tilting with respect to the horizontal direction.

[0004]

[Problems to be Solved by the Invention]
Japanese Unexamined Patent Publication No. 1 discloses a technique of pressing both longitudinal ends of an optical element with a coil spring. However, there is a concern that the above-mentioned shape deformation of the optical element when the environmental temperature changes may adversely affect the optical characteristics. It Japanese Unexamined Patent Application Publication No. 4-265919 discloses a technique for bonding and fixing the central portion of an optical element, but in the case of a long optical element, it is difficult to mount the optical element on the housing without tilting horizontally. The present invention has been made in view of the above, and even when the reflective optical element undergoes shape deformation (contraction, expansion) due to temperature fluctuation,
The reflective optical element is continuously pressed against the reference mounting surface without disturbing the isotropic shape change of the reflective optical element, and the optical characteristics are not adversely affected outside the design calculation. It is an object of the present invention to provide an optical scanning device in which a reflective optical element does not move out of a predetermined mounting position even when a large force is applied.

[0005]

In order to achieve the above object, the invention of claim 1 comprises a light source for emitting an optical beam, a deflector for deflecting and scanning a light beam from the light source, and a deflector. An optical scanning device in which an optical element group for forming an image of the reflected light flux on the photoconductor surface, the light source, the deflector, and the optical element group are housed in a housing. A shock absorbing material having repulsive elasticity in the upper surface of the reflective optical element arranged along the mounting reference plane in the housing and in the gap between the reflective optical element and the housing. And the upper surface of the shock absorber is fixed to the housing while the upper surface of the shock absorber is pressed and compressed by the pressing flat plate. According to a second aspect of the present invention, a light source that emits a light beam, a deflector that deflects and scans a light beam from the light source, and an optical element group that forms an image of a reflected light beam from the deflector on a photosensitive member surface are provided.
An optical scanning device in which the light source, the deflector, and the optical element group are housed in a housing, wherein a reflective optical element having an image forming characteristic is used as one of the optical element groups, and an upper opening of the housing is covered by a cover. In the closed structure, a shock absorbing material having impact resilience is arranged in the gap between the cover and the upper surface of the reflective optical element and the gap between the housing and the reflective optical element, and the cover is attached to the housing. The reflective optical element is fixed to the mounting reference surface in the housing while the impact absorbing material is compressed by the cover when it is fixed. According to a third aspect of the present invention, the shock absorbing material having the repulsive elasticity is previously integrated with a specific portion of the reflective optical element having the image forming characteristic.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. 1 (a) and 1 (b) show an optical scanning device using a general reflective optical element. In this optical scanning device, a light beam emitted from the light source unit 3 enters a deflector 4 (rotary polygonal mirror) and is deflected within a predetermined angle range, and a reflection optical element 5 (fθ mirror) having an image forming characteristic is formed. , The first folding mirror 6, the long cylindrical lens 7, and the second folding mirror 8 to form an image on the photoconductor 9. These optical elements are housed inside the housing 1 and the dustproof cover 2. 2, 3 (a) and (b) and FIGS. 4 (a) and (b) show the configuration of the embodiment of the optical scanning device corresponding to the first aspect. As shown in FIG. 3, in the present invention, when the reflective optical element 5 is placed on the mounting reference surfaces 12 and 13 on the bottom surface of the housing 1, a gap is formed between the reflective optical element 5 and the housing 1, and A shock absorber 1 made of a material having repulsive elasticity extending from the upper surface, the side end surface, and the back surface of both ends of the reflective optical element 5 in the longitudinal direction.
0 is placed. On the upper surface of the reflective optical element 5, a holding plate 11 having a composition is additionally attached and fixed from above the reflective optical element 5, and the shock absorbing material 10 is pressed and deformed by a predetermined force (see FIG. b)). Even if the reflective optical element 5 contracts due to a decrease in environmental temperature, the pressing force applied by the pressing plate 11 causes the pressing plate 11 and the upper surface of the reflective optical element 5 to expand by the contraction of the shock absorbing material 10. The gap between the reflective optical element and the housing is set so as not to expand. Reference numeral 12 is a Z-direction mounting reference surface of the reflective optical element on the optical housing 1, and 13 is an X-direction mounting reference surface of the reflective optical element on the optical housing 1.

The portion shown by the mesh in FIG. 4 (b) shows the range before the shock absorbing material 10 is compressed by the pressing flat plate 11 and shrinks. By arranging them, as described above, even if the reflective optical element contracts, it can be surely pressed. Although FIG. 4 (b) shows that the thickness of the bottom of the housing 1 is not uniform, it is clear that the present invention can be applied to a housing having a uniform thickness.
The impact absorbing material having impact resilience is a material that is not deformed by a large acceleration force but is deformed by a gentle force. As a method of fixing the pressing plate 11 while pressing it onto the shock absorbing material 10, the pressing plate 11 may be fixed to the upper end surface of the reference surface 13, fixed while being pressed by the dustproof cover 2, or fixed by another fixing tool. It is possible to do it.

As described above, in the optical scanning device of this embodiment, the reflection optical element 5 having the image forming characteristic is pressed from above by the impact absorbing material 10 having repulsion elasticity and fixed to the inner bottom surface of the housing 1. Therefore, even if the reflective optical element 5 undergoes shape deformation (contraction or expansion) due to environmental temperature fluctuations, the shock absorbing material 10 itself deforms in shape, so that the reflective optical element isotropic. The reflective optical element can be continuously pressed against the reference mounting surface without disturbing the physical shape change, and the optical characteristics are not adversely affected outside the design calculation. For example, even if the reflective optical element 5 contracts due to a decrease in temperature, the volume of the shock absorbing material 10 expands by that amount, so that there is no backlash formed between the reflective optical element 5 and the housing 1. Even if the volume of the reflective optical element expands due to the temperature rise, the shock absorbing material can absorb the volume change reasonably. Further, when a large acceleration force such as a shock is applied to the optical scanning device, the shock absorbing material is not deformed by the repulsive elasticity, so that the reflective optical element does not come off from the predetermined mounting position. FIG.
As shown by the mesh in (b), the shock absorber 10 is compressed not only on the upper surface in contact with the pressing plate 11, but also on the side surface in contact with the reference surface 13 of the housing. Also,
In the above embodiment, the impact absorbing material 10 is arranged only at both ends in the longitudinal direction of the reflective optical element, but this is an example, and it may be attached to the entire upper surface of the element including both ends in the longitudinal direction. This point can be similarly applied to all the following embodiments.

Next, FIG. 5 and FIGS. 6A and 6B show the structure of the optical scanning device according to the second aspect. This form example is characterized in that the holding flat plate 11 is omitted and the dust absorbing cover 2 performs the holding function of the shock absorbing material 10 by the holding flat plate 11. According to this embodiment, since the shock absorbing material 10 is pressed by the dustproof cover 2, the number of parts can be reduced, the number of assembly steps can be reduced, and the cost can be reduced. FIG.
The mesh part in (b) shows the amount of contraction caused by the impact absorbing material being pressed by the dustproof cover 2.

Next, FIG. 7 is a configuration diagram of a reflective optical element corresponding to claim 3. In this embodiment, the reflective optical element 5 is provided at appropriate positions at both ends in the longitudinal direction, that is, in this example, the reference surface 12,
It is characterized in that the shock absorbing material 10 is previously integrated on a portion of the reflective optical element facing the reference surface and a portion of the housing 1 where the gap with the housing 1 is filled. The fixing method is adhesion or the like. In this embodiment, since the shock absorbing material 10 having repulsion elasticity is fixed to the reflective optical element itself having the image forming characteristic, the assembly process can be simplified and the cost can be reduced. Next, in the one in which the reflective optical element is integrated with the shock absorbing material, the pressing flat plate 11 may be used as a means for bringing the shock absorbing material 10 into a compressed state. This form example has the same effect as the form example corresponding to claim 1 in addition to the effect of the form example corresponding to claim 3. Further, in the case where the reflective optical element is integrated with the shock absorbing material, the dustproof cover 2 may be used as a means for bringing the shock absorbing material 10 into a compressed state. This form example
In addition to the effect of the form example corresponding to claim 3, the same effect as the form example corresponding to claim 2 is achieved.

[0011]

As described above, in the optical scanning device according to the first aspect, the reflective optical element having the image forming characteristic is fixed to the housing by being pressed by the impact absorbing material having the impact resilience. When the shape of the reflective optical element is deformed (contracted or expanded) due to temperature change, the shape of the shock absorbing material itself is deformed according to the deformation, and the reflective optical element is not hindered from changing the isotropic shape of the reflective optical element. Keep pressing on the reference mounting surface,
The optical characteristics are not adversely affected outside the design calculation. Further, even when a high acceleration force such as a shock is applied to the optical scanning device, the shock absorber does not deform due to the impact resilience.
The reflective optical element does not come off from the predetermined mounting position.
In the optical scanning device according to the second aspect, since the impact absorbing material is pressed by the cover, the number of parts can be reduced, so that the number of assembling steps can be reduced and the cost can be reduced. In the third aspect, since the shock absorbing material having repulsive elasticity is attached to the reflective optical element itself having the image forming characteristic, the assembly process can be simplified and the cost can be reduced.

[Brief description of drawings]

1A and 1B are perspective views of a general optical scanning device,
And a cross-sectional view.

FIG. 2 is an exploded perspective view of an example of an optical scanning device of the present invention.

3A and 3B are exploded perspective views of a main part of the optical scanning device of FIG.

4 (a) and 4 (b) are an explanatory view and a sectional view of a mounting state of a main part of the optical scanning device of FIG.

FIG. 5 is an exploded perspective view of another example of the present invention.

6 (a) and 6 (b) are explanatory views of the assembling procedure of the embodiment example of FIG.

FIG. 7 is an explanatory diagram of a main part configuration of another example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical housing, 2 ... Dust-proof cover of optical housing, 3 ... Light source section, 4 Deflector, 5 ... Reflective optical element having imaging characteristics , 6 ...
・ First folding mirror, 7 ... Cylindrical lens, 8 ... Second folding mirror, 9 ... Photoconductor, 10 ... Impact absorbing material having impact resilience, 11 ...
.A plate for pressing and fixing the shock absorbing material, 12 ...
Z-direction mounting reference surface of the reflective optical element on the optical housing, 13 ... X-direction mounting reference surface of the reflective optical element on the optical housing

Claims (3)

[Claims] 1. A light source that emits a light beam, a deflector that deflects and scans a light beam from the light source, an optical element group that forms an image of a reflected light beam from the deflector on a photoconductor surface, and the light source. An optical scanning device in which the deflector and the optical element group are housed in a housing, in which a reflective optical element having an image forming characteristic is used as one of the optical element groups, the mounting reference surface in the housing is A shock absorbing material having repulsive elasticity is arranged in the upper surface of the reflective optical element and the gap between the reflective optical element and the housing, and the upper surface of the shock absorbing material is pressed by a flat plate. An optical scanning device characterized in that the pressing plate is fixed to a housing in a compressed state. 2. A light source that emits a light beam, a deflector that deflects and scans a light beam from the light source, an optical element group that forms an image of a reflected light beam from the deflector on a photosensitive member surface, and the light source. An optical scanning device in which the deflector and the optical element group are housed in a housing, wherein a reflective optical element having an image forming characteristic is used as one of the optical element groups, and an upper opening of the housing is closed by a cover. In such a structure, a shock absorbing material having repulsive elasticity is arranged in the gap between the cover and the upper surface of the reflective optical element and the gap between the housing and the reflective optical element to fix the cover to the housing. The optical scanning device is characterized in that, when doing so, the shock absorbing material is compressed by a cover and the reflective optical element is fixed to a mounting reference surface in the housing. 3. The optical scanning device according to claim 1, wherein the shock absorbing material having the repulsive elasticity is previously integrated with a specific portion of the reflective optical element having the image forming characteristic. .