JPH04265919A - Positioning and fixing device for lens - Google Patents

Abstract

PURPOSE:To offer a means which positions and fixes a resin-made image forming lens formed as the meniscus lens in the laser write optical system of a laser printer, etc., to an optical system housing with simple constitution without generating any strain due to thermal stress. CONSTITUTION:A housing is provided with projections 10a-10c which support the image forming lens 4 at a specific position by holding both two end parts of one of the incidence and projection surfaces of the image forming lens therebetween and the part of the center part 1 of the other surface and the positioned lens 4 is fixed by adhesion to the housing at one point of the center part of the plane part of the lens 4. Even when resin is used for the lens and expands or shrinks thermally, the lens 4 is not stressed in a longitudinal direction and prevented from degradation in image formation characteristics and peeling off the housing owing to the straining.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning and fixing device for a meniscus lens used as a scanning lens in a laser writing optical system of a laser printer or the like.

0002

2. Description of the Related Art As shown in FIG. 3, a writing optical system of an image forming apparatus such as a laser printer or a digital copying machine that writes an image on a photoreceptor using a laser beam uses an image signal from a semiconductor laser unit 1. After the modulated output beam is shaped by the aperture 2, it is repeatedly deflected within a predetermined angular range by the rotating polygon mirror 3, passes through the imaging lens 4, the reflecting mirror 5, and the cylindrical lens 6, and then forms a spot on the photoreceptor 7. image and perform main scanning in the axial direction of the photoreceptor 7,
A device in which sub-scanning is performed by moving the photoreceptor 7 is widely used.

[0003] The above-mentioned imaging lens 4 normally spreads over the deflection range of the laser beam and scans the entire width of the photoreceptor by passing the laser beam deflected within a predetermined angular range. The surface is concave and the second surface is convex, parallel to the optical axis,
It is formed as a rectangular meniscus lens having two planes parallel to the deflection plane.

Conventionally, as a method for positioning and fixing an imaging lens having such a shape to an optical system housing, as shown in FIGS. Positioning is performed in the longitudinal direction by abutting against mutually opposing surfaces of positioning ribs 8 with an L-shaped cross section protruding from the surface of the lens. The flat surface facing the surface of the housing was brought into contact with the reference surface of the upper surface of the protrusion 9 provided at two locations on the housing surface and fixed by adhesion.

However, due to changes in the environment in which the equipment is used, temperature rises inside the equipment in which the optical system is mounted, etc., temperatures in the operating state range from 10 to 60°C, and when transport environments are included, the temperature ranges from -40° to +7°C.
It may be subject to temperature changes of 0°C. On the contrary,
If the thermal expansion coefficients of the lens and optical system housing are the same, there will be no problem, but the functional materials required for each member are different, and the housing is reinforced with glass fiber or carbon fiber due to the requirements for optical element placement accuracy and strength. Polycarbonate, acrylic, etc. are used without reinforcing fibers to increase light transmittance when resin molded lenses are used. If the coefficient of thermal expansion is larger than that of the housing and the above lens positioning and fixing method is adopted, the edges at both ends of the lens will be pushed by the positioning ribs and the arc-shaped lens will be distorted, resulting in distortion of the entrance and exit surfaces. This impairs surface precision, causing problems in imaging characteristics.

[0006] As a countermeasure against this problem, for example, Japanese Patent Laid-Open No. 58-15
As disclosed in Japanese Patent No. 3907, a gate is provided in the positioning part where the edge of the resin lens comes into contact, and when the lens thermally expands, the edge of the lens is inserted into the gate to prevent excessive force from being applied to the lens. Although it has been proposed to prevent the gate from working, it has the disadvantage that it takes time and effort to install the gate.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the conventional method of positioning and fixing a meniscus lens of a laser-written optical type such as a laser printer with respect to a housing, the present invention has been made to solve It is an object of the present invention to provide a lens positioning and fixing device with a simple configuration that does not cause the lens to be distorted due to changes and cause deterioration of imaging characteristics.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the lens positioning device of the present invention provides two positions at both ends of one surface of the lens entrance/exit surface having the above-mentioned shape and one position at the center of the opposite surface. The lens is characterized in that the optical system housing is provided with a portion that abuts at a predetermined lens installation position.

Further, the lens fixing device of the present invention is provided with a part on the optical system housing that abuts against the flat surface of the lens at one place near the center of the lens positioned by the positioning device and fixes the lens by bonding it. Features.

0010

[Function] With the configuration of the lens positioning device described above, when a temperature change occurs, both ends of the lens slide against the positioning surface due to the difference in coefficient of thermal expansion between the lens and the housing, and the edges of both ends of the lens slide. Since the lens will not be distorted by pressure, the imaging characteristics will not deteriorate.

Furthermore, according to the above-mentioned lens fixing device, since it is fixed to the housing only at one location in the center, even when plastic with a high coefficient of thermal expansion is used as the material for the lens, the lens remains fixed in the longitudinal direction. It is held in a flexible manner by sliding on the positioning parts at both ends without being constrained by the material, and will not be distorted or the adhesive will peel off. In addition, since there is no need to form a gate, the configuration is simple and the manufacturing and assembly process requires no effort.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings.

FIGS. 1 and 2 are an exploded perspective view and a plan view showing the structure of an embodiment of the present invention.

In this embodiment, as a positioning device for the lens 4, with the lens 4 installed at a predetermined position in the housing, a protrusion is provided on the lens mounting surface of the housing at a position where both ends of the entrance surface of the lens should abut. The provided positioning protrusion 10a,
10b and a positioning protrusion 10c that protrudes from the housing surface is provided at a position that abuts near the center of the exit surface of the lens 4. The height of the protrusion 10c is set so as not to interfere with the transmission of the laser beam. Also, the protrusions 10a, 10b
Aligning the matching marks provided as necessary on the top surface of the lens 4 and the top surface of the lens, place the lens 4 on the protrusions 10a, 10b, 10c.
By clamping the lens with the housing, the lens is positioned at a predetermined position with respect to the housing.

[0015] At the position where the central part of the lower surface of the lens 4 positioned in this way should come into contact, a protrusion 11 is provided on the upper surface of the housing for determining the position of the lens in the height direction and for gluing and fixing the lower surface of the lens. It is provided.

[0016] Therefore, the protrusions 10a, 10b, 10c
The lens 4, which is positioned by being sandwiched between the
By contacting and gluing the upper surface of 1, the central position 1
Fixed at a predetermined height.

With this configuration, when the lens 4 expands and contracts with respect to the housing due to thermal changes, the entrance surface of the lens slides on the protrusions 10a and 10b, and the lens does not become distorted or image formed without stress. Does not cause deterioration of characteristics.

[0018]

As described above, according to the present invention, even when a resin whose coefficient of thermal expansion is larger than that of the housing is used as the material for the lens, distortion due to temperature changes does not occur in the longitudinal direction of the lens. It is possible to prevent deterioration of imaging characteristics due to deformation of the lens surface, peeling of lens adhesive due to stress, etc., and is effective in improving image quality. or,
Even when using resin-molded lenses, there is no need to perform gate treatment on the edges, which is effective in reducing the number of steps required for manufacturing and assembly.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the configuration of an embodiment of the present invention.

FIG. 2 is a plan view thereof.

FIG. 3 is a perspective view showing an example of a general configuration of a laser writing optical system.

FIG. 4 is an exploded perspective view showing an example of a conventional imaging lens positioning and fixing device.

FIG. 5 is a plan view thereof.

[Explanation of symbols]

4 Imaging lens (meniscus lens) 10a, 10b
, 10c Positioning protrusion 11 Adhesive protrusion

Claims (2)

[Claims] 1. A device for positioning a rectangular lens with respect to an optical system housing, which focuses a light beam deflected in one plane on a straight line on an imaging plane and has a plane parallel to the deflection plane. A lens positioning device characterized in that an optical system housing is provided with a portion where two ends of one side of the light emitting surface and one center portion of the opposite side abut at a predetermined installation position. 2. The optical system housing is provided with a portion that abuts the flat surface of the lens at one location near the center of the lens positioned by the positioning device according to claim 1, and adheres and fixes the lens. The fixed position of the lens is a feature.