JPH10268221A - Optical scanning device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix a plastic element to an optical housing (support) without failing in manufacturing, to reliably position, and to expand and contract in a longitudinal direction due to a change in temperature and humidity. To avoid the problems described above. SOLUTION: fθ mirror 1 as a plastic element
Reference numeral 01 denotes a positioning surface 108 as a receiving surface for receiving a lateral end (positioning point 1) at a longitudinal central portion of a lower surface of the rib 103 of the fθ mirror 101 in a height direction, and a lateral surface at both longitudinal ends. The optical housing is supported at three points, namely, positioning surfaces 106 and 107 as receiving surfaces for receiving the ends (positioning points 2 and 3) on the opposite side to the above-mentioned ends, and is adhered and fixed only at the center positioning surface 108. ing. Only the upper surface corresponding to the positioning surfaces 106 and 107 is pressed and held by the leaf spring 111.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
More particularly, the present invention relates to an optical scanning device used in an optical writing system such as a laser printer, and more particularly, to a technique for supporting a plastic optical element.

[0002]

2. Description of the Related Art In recent years, plasticization of optical elements has been progressing in terms of cost reduction and weight reduction. However, plastic elements are more difficult to mold due to their resin characteristics than conventional glass optical elements such as glass lenses. Because the shape accuracy is deteriorated due to distortion, etc., and environmental and temporal fluctuations due to temperature and humidity are large, the position relatively close to the photoreceptor, which is the imaging position, so that the imaging performance can be maintained even due to these shape changes. It is configured to be arranged in. Specifically, it is often applied to a long optical element such as a toroidal lens.

As a method of fixing (supporting) such a long plastic element to an optical housing, for example, a structure as shown in FIG. 7 is conventionally known. At both ends of an fθ mirror 201 as an example of a long plastic element, ears 201a and 201b protruding in the longitudinal direction are formed, and a convex part 201c for supporting the central part is provided on the back surface of the central part in the longitudinal direction. Are formed. On the other hand, the optical housing is formed with receiving surfaces 202 and 203 for performing positioning in a direction substantially orthogonal to the scanning plane, and abutting surfaces 204 and 205 for performing positioning in the optical axis direction. Slide support 20 with central support piece 20
7 are formed. The fixing to the optical housing is performed by using screws 10 to the supports 208 and 209 fixed to the optical housing.
The pressing is performed by the pressing member 206 fixed by. That is, the first leaf spring portion 206a of the pressing member 206 presses the upper surface of the fθ mirror 201 to press the receiving surface 20a.
The lower surface of the fθ mirror 201 is brought into contact with the lower and upper surfaces 2 and 203, and the ear portions 201a and 201
b is pressed against the abutting surfaces 204 and 205 to be fixed.

[0004]

However, the receiving surfaces 202 and 203 and the abutting surface 20 in the above-mentioned prior art are used.
4 and 205 are orthogonal to each other, and if there is a squareness error between the two, any one of the elastic force of the first leaf spring portion 206a and the second leaf spring portion 206b of the pressing member 206 is reduced. A phenomenon occurs in which the surface comes into contact with the surface corresponding to the stronger one and floats from the other surface. For this reason,
If the posture of the optical element (fθ mirror 201) is tilted in the sub-scanning direction, or if there is an error in the inclination of the surface at both ends in the longitudinal direction, a stress in the direction in which the optical element is twisted acts and the optical element is deformed. There is a problem that the optical performance is deteriorated. Receiving surfaces 202, 203 and abutting surfaces 204,
The right angle of 205, the lower surface of the fθ mirror 201 and the ear 2
The above-mentioned problem can be solved by giving the squareness of the optical element 01a and 201b with high accuracy. However, it is not possible to make the dimensional accuracy in plastic molding uniform at both ends of the optical element, that is, to give out such that no twisting occurs. It is very difficult in practice.

Japanese Patent Application Laid-Open No. Hei 5-93831 discloses that a single band-shaped leaf spring is arranged at both ends of a long lens in a direction perpendicular to the longitudinal direction, and the urging force abuts the positioning surface of the optical housing. Although a technique for performing the positioning is disclosed, there is no change in the configuration in which the positioning is performed by pressing the positioning surface orthogonal to the optical housing with a spring member. Therefore, it can be said that the above-described problem still remains.

Accordingly, the present invention can accurately position the optical element in the optical housing without manufacturing difficulties, and even if the dimensional change of the optical element occurs due to a change in the environment, the posture change in the optical element or an unreasonable change in the position of the optical element. An object of the present invention is to provide an optical scanning device capable of preventing generation of stress and contributing to improvement of image quality.

[0007]

Means for Solving the Problems The positioning of the prior art is based on a system in which both the receiving surface 202 and the abutting surface 204 which is orthogonal to the receiving surface 202 have equivalent positioning functions when viewed from one end in the longitudinal direction. There is a configuration in which the predetermined positioning is performed only when they are brought into close contact with each other. Therefore, the above-described problem due to the bias of the pressing force of the pressing member occurs. Therefore, if the support function of both the receiving surface and the abutment surface is given a master-slave relationship to establish the positioning accuracy on one surface, and the other surface has only a position regulating function, It is expected that the problem can be solved without manufacturing difficulties. This is the purpose of the present invention. More specifically, according to the first aspect of the present invention, a laser light source, a deflector for deflecting a beam emitted from the laser light source, and a long plastic element for forming an image of the deflected beam on a surface to be scanned. In the optical scanning device provided with an imaging optical system having the following configuration, the long plastic element has a short-side end (positioning point 1) at a center in the longitudinal direction and a longitudinal direction on a lower surface side in the height direction. Ends opposite to the end in the short direction at both ends (positioning points 2,
3) is supported at the three points and is fixed only at the positioning point 1, and at the positioning points 2 and 3, it is elastically urged toward the positioning points 2 and 3 from the upper surface in the height direction and held. Is adopted. That is, the positioning of the plastic element on the receiving surface is established with high accuracy, and a three-point support system is employed to realize the high accuracy.

According to the second aspect of the present invention, in the configuration of the first aspect, the receiving portion corresponding to the positioning point 1 is:
The height position is formed so as to be adjustable. The support function of the three-point support system is intended to easily increase the support accuracy by the adjusting function of the receiving portion.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 6 is an overall schematic diagram of an example of an optical scanning device to which the present invention is applied. A laser beam emitted from the semiconductor laser 301 is converted into a parallel light beam by a collimator lens 302, applied to a polygon mirror 304 via a cylinder lens 303, reflected, and deflected. The laser beam deflected by the polygon mirror 304 is returned to the mirrors 307 and 30 by the fθ mirror 101 as a plastic element constituting the imaging optical system and the toroidal lens 306 as a plastic element.
An image is formed in the form of a spot on the photosensitive member 308, which is the surface to be scanned, via 7 'to form a latent image.

As described above, the long fθ mirror 101 and the toroidal lens 306 are both formed of plastic. The support structure of the fθ mirror 305 on the optical housing will be described below. As shown in FIG. 1, the fθ mirror 101 includes an aluminum-deposited mirror surface 102 formed of an aspherical concave curved surface, and an aluminum-deposited mirror surface 10.
2, a frame-shaped rib 103 provided so as to surround the two, ears 104 and 105 provided so as to protrude from both ends in the longitudinal direction for positioning in the optical axis direction, and a central portion in the longitudinal direction of the rib 103. It is integrally formed with a convex portion 113 provided on the back side for supporting a central portion.

In fixing to the optical housing H (FIGS. 2 and 5), first, the convex portion 1 is inserted into the concave portion 115 on the optical housing H side.
13 is engaged and the center position of the fθ mirror 101 in the main scanning direction is adjusted, and the lower surface in the height direction is
The ears 104, 1 are aligned with a surface 114 (FIG. 2) substantially parallel to the scanning plane protruding from the bottom surface of the optical housing H and positioned on the optical housing H for positioning in the optical axis direction.
05, and the positioning of the fθ mirror 101 is performed. Thereafter, fixing is performed on a positioning surface 108 described later, and further, the upper surface of the rib 103 corresponding to the positioning surfaces 106 and 107 described later is placed on the support 11 on the optical housing H side.
3, 114 are pressed and held by a convex portion 111a of a leaf spring 111 as a pressing member fixed by a screw 112. The alignment with the surface 114 substantially parallel to the scanning plane is performed by positioning the positioning surface 108 as a receiving surface for receiving a lateral end (positioning point 1) at the longitudinal center of the lower surface of the rib 103 of the fθ mirror 101 in the height direction. And an end opposite to the end in the short direction at both ends in the longitudinal direction (positioning points 2,
3) Positioning surfaces 106, 107 as receiving surfaces for receiving
This is achieved by three-point support. As shown in FIG. 2, an angle α between the scanning plane and the surface 114 in the present embodiment.
Is set to 3 °.

Fθ mirror 10 as a plastic element
In order to surely receive the positioning surface 1 on the three positioning surfaces 106, 107, and 108, as shown in FIG.
6 (corresponding to positioning point 2 (P2)), 107 (corresponding to positioning point 3 (P3)), 108 (positioning point 1 (P1)
Is preferably as small as possible with respect to the distance e between the positioning points in the short direction (optical axis direction). In this embodiment, d = 3 mm and e = 15 mm. The distance L between the positioning points in the longitudinal direction was 220 mm. If d, which is the length of one side of each of the positioning surfaces 106, 107, and 108, is large, if the height of each of the positioning surfaces 106, 107, and 108 is uneven, the positioning surfaces 106, 107, and 108 become higher and become lower. The problem of floating from the surface occurs. The object (here, the fθ mirror 101) received there due to the variation in the height of each of the positioning surfaces 106, 107, and 108 is inclined by θ ° as shown in FIG. d must be set according to the allowable inclination. Since the variation in height of each positioning surface 106, 107, 108 is assumed to be about 0.05 mm,
In order to set the inclination of the fθ mirror 101 in the direction corresponding to the sub-scanning direction to 15 minutes or less, which has little effect on the performance, ed> 1
1.5 mm is desirable. From this point of view, real values such as d are set.

The fixing of the positioning surface 108 at the center in the longitudinal direction is performed by applying an ultraviolet-curable adhesive, irradiating ultraviolet rays after the positioning, and curing the adhesive. Instead of applying the adhesive directly on the positioning surface 108,
As shown in FIG. 1 and FIG.
mm) is lowered to form the stepped surface 116, and the stepped surface 11
6 is coated with an adhesive 117. Since the area of the positioning surface 108 is small as described above, forming the bonding surface around the positioning surface 108 increases the bonding area to secure the bonding strength.
Since the adhesive 117 does not exist between the bottom surface and the bottom surface, there is an advantage that the surface alignment can be performed accurately.

FIG. 5 shows an embodiment corresponding to claim 2, wherein the inclination of the fθ mirror 101 in the sub-scanning direction can be adjusted. In the present embodiment, the positioning surface 118 as the receiving portion at the center in the longitudinal direction is formed in a spherical shape, and the screw hole 11 formed in the optical housing H is formed.
9 and is integrally formed on the upper end of a screw 120 that can be displaced in the vertical direction. In general, an inclination error in the sub-scanning direction of an optical element means eccentricity with another optical element, which causes bending of a scanning line and deterioration of image forming performance. By letting
The inclination in the sub-scanning direction of the fθ mirror 101 determined by the positioning surfaces 106 and 107 can be adjusted.
For this reason, the tolerance of the manufacturing accuracy of the positioning surfaces 106 and 107 can be increased as compared with the above embodiment, and the manufacturing can be facilitated. Further, since the inclination adjustment of the fθ mirror 101 in the sub-scanning direction can be performed steplessly, the inclination of the fθ mirror 101 can be set with high accuracy. Since the positioning surface 118 is formed in a spherical shape, it comes into contact with the bottom surface of the fθ mirror 101 in a substantially point contact state. Therefore, even if the adjustment is made by the rotation of the screw 120 and the vertical position of the positioning surface 118 is displaced, the state of contact with the fθ mirror 101 does not change.

After the three-point support by the positioning surfaces 106, 107 and 118 and the adjustment by the positioning surface 118 are performed and the positioning is completed, the ultraviolet curing adhesive 117 is irradiated with ultraviolet rays to be cured similarly to the above embodiment. Thus, the fixing at the positioning surface 118 is performed. Leaf spring 11
The pressing support at the upper surface position corresponding to the positioning surfaces 106 and 107 by 1 is the same as in the above embodiment.

In each of the above embodiments, the method of fixing (supporting) the fθ mirror 101 to the optical housing H has been described.
The toroidal lens 306 as a plastic element can be implemented in the same manner as described above.

[0017]

According to the first aspect of the present invention, since the positioning accuracy is established by receiving the plastic element at three points in a direction substantially perpendicular to the scanning surface, there is no difficulty in manufacturing. It is possible to avoid lifting and twisting due to the elasticity of the holding member as in the conventional case, and it is possible to prevent deterioration of the imaging performance due to plasticization of the optical element. Further, since only the central portion in the longitudinal direction is fixed, it is possible to prevent bending in the sub-scanning direction due to dimensional change in the longitudinal direction, and to provide an optical scanning device that is resistant to temperature and humidity changes.

According to the second aspect of the present invention, the height of the receiving portion at the central portion in the longitudinal direction can be changed.
In addition to the effect of the first aspect, it is possible to perform adjustment for minimizing the inclination error of the plastic element in the sub-scanning direction, and thus it is possible to perform high-quality image formation.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a configuration for supporting an fθ mirror as a plastic element on an optical housing in an optical scanning device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a support structure at a center in a longitudinal direction among three points support of an fθ mirror.

FIG. 3 is a plan view for explaining dimensional conditions of three-point support.

FIG. 4 is a side view for explaining a tilt error in the sub-scanning direction.

FIG. 5 is an enlarged cross-sectional view showing a support structure at a center in a longitudinal direction among three-point support of an fθ mirror in another embodiment.

FIG. 6 is a schematic diagram showing the overall configuration of the optical scanning device.

FIG. 7 is an exploded perspective view showing a configuration for supporting an fθ mirror as a plastic element on an optical housing in a conventional optical scanning device.

[Explanation of symbols]

 301 Laser light source 304 Deflector 101 fθ mirror as a plastic element 306 Toroidal lens as a plastic element 108, 118 Positioning surface as positioning point 1 106 Positioning surface as positioning point 2 107 Positioning surface as positioning point 3

Claims (2)

[Claims] A laser light source, a deflector for deflecting a beam emitted from the laser light source, and an imaging optical system having a long plastic element for imaging the deflected beam on a surface to be scanned. In the optical scanning device provided, the long plastic element has, on the lower surface side in the height direction, a lateral end (positioning point 1) at a longitudinal central portion, and the lateral end at both longitudinal ends. Are supported at three points on the opposite end (positioning points 2 and 3) and are fixed only at positioning point 1 and at positioning points 2 and 3 from the upper surface in the height direction to positioning points 2 and 3 An optical scanning device, wherein the optical scanning device is elastically urged toward and held. 2. The optical scanning device according to claim 1, wherein a height of the receiving portion corresponding to the positioning point 1 is adjustable.