JPH07306348A - Optical scanning device - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the number of assembling parts of the optical system of the optical scanning device and simplify the assembling. A laser beam generated from a semiconductor laser 1a is collimated by a glass collimator lens 2a,
The light is linearly focused on the reflecting surface of a rotating polygon mirror (not shown) by the plastic cylinder lens 2b. The cylinder lens 2b is integrated with the plastic lens holder 3 that holds the collimator lens 2a, and the optical alignment of the cylinder lens 2b is performed together with the collimator lens 2a. Therefore, the assembly process of the optical system is simple, The number of parts is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used in an image forming apparatus such as a laser printer or a laser facsimile.

[0002]

2. Description of the Related Art An optical scanning device used in an image forming apparatus such as a laser printer or a laser facsimile has a laser beam L emitted from a semiconductor laser 101 as shown in FIG.
After collimating ₀ by the collimator lens 103, it is condensed into a linear light beam by the cylinder lens 102, and a direction along the rotation axis (hereinafter, “z-axis direction”) is obtained by the rotating polygon mirror P that rotates in the direction of arrow A. And the optical axis direction of the laser light (hereinafter, referred to as “x-axis direction”) and a direction (hereinafter, referred to as “y-axis direction”) that is deflected and scanned to form an imaging lens including a spherical lens 104 and a toric lens 105. An image is formed on the photoconductor on the rotary drum D through the system F.
The light flux that forms an image on the photoconductor is y due to the rotation of the rotary polygon mirror P.
An electrostatic latent image is formed by main scanning in the axial direction and sub-scanning in the z-axis direction by rotation of the rotary drum D.

In the assembly and manufacture of such an optical scanning device, as shown in FIG. 6, first, the semiconductor laser 101 is assembled to the lens barrel of the collimator lens 103 to manufacture an integrated light source unit E ₀ , It was general that the light source unit E ₀ and the cylinder lens 102 were individually attached to the housing H of the optical scanning device. The cylinder lens 102 condenses the laser light in the z-axis direction into a substantially linear parallel light beam, thereby causing distortion of the point image due to surface tilt of the reflecting surface when the rotation axis of the rotary polygon mirror P is tilted. It is an anamorphic lens for preventing the toric lens 105 of the imaging lens system F.
Similarly, it also functions as an anamorphic lens that prevents the image forming position of the point image from shifting in the z-axis direction due to the surface tilt of the rotary polygon mirror P.

[0004]

However, according to the above conventional technique, since the collimator lens and the cylinder lens are individually attached to the housing of the optical scanning device as described above, the collimator with respect to the housing is assembled. It is necessary to position the cylinder lens with respect to the collimator lens every time the lens mounting position is changed, and therefore, the mounting portion of the cylinder lens with respect to the housing must be finished with high accuracy. As a result, many costly parts are required, and a lot of labor and time are required for assembly, which is a major obstacle to reducing the manufacturing cost of the optical scanning device.

Further, it has been proposed to integrally mold the collimator lens and the cylinder lens with a glass mold, but the integral molding with glass requires a large capital investment, is technically difficult, and is rather expensive. It is also considered to integrally mold the collimator lens and the cylinder lens with plastic, but the plastic lens tends to have a large change in optical performance due to temperature changes, and is not suitable for a collimator lens having high light converging property. is there.

The present invention has been made in view of the above problems of the prior art, and simplifies the assembly of an optical system including a collimator lens and an anamorphic lens, reduces the cost of parts, and reduces the number of parts to be assembled. An object of the present invention is to provide an optical scanning device that can be greatly promoted.

[0007]

In order to achieve the above object, the optical scanning device of the present invention is such that the illumination light generated from a light source is collimated by a collimator lens, and then is rotated through at least one anamorphic lens. An optical scanning device for irradiating a mirror and forming an image of the reflected light on a photoconductor by an imaging lens system, wherein the collimator lens is held by a lens holding unit that is integral with the anamorphic lens. And

It is preferable that the anamorphic lens and the lens holding means are integrally molded of a transparent plastic material.

Further, it is preferable that the collimator lens is integrally embedded in the lens holding means.

[0010]

According to the above apparatus, since the collimator lens is held by the lens holding means which is integral with the anamorphic lens, the position of the anamorphic lens is changed when the mounting position of the collimator lens is changed to align the optical axis of the collimator lens. No alignment is required. The rotation angle of the anamorphic lens about the optical axis is adjusted by rotating the lens holding unit together with the collimator lens. Assembling work is easy because there is no need to adjust the mounting positions of the collimator lens and anamorphic lens individually, and the cost of parts is low because it is not necessary to provide a highly accurate mounting part for the anamorphic lens. Can be greatly promoted. In addition, by integrally molding the anamorphic lens and the lens holding means, the number of assembly parts can be significantly reduced. Further, if the collimator lens is integrally embedded in the lens holding means, the number of assembling parts can be further reduced and the assembling process can be simplified.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partial schematic sectional view showing only a light source unit E ₁ of an optical scanning device according to an embodiment, which is a lens barrel 1 in which a semiconductor laser 1a as a light source is integrally assembled.
And a glass collimator lens 2a and a transparent plastic anamorphic cylinder lens 2b. The collimator lens 2a is a cylindrical lens holder integrally formed of the same transparent plastic as the cylinder lens 2b. It is held by the lens holder 3 which is a means. That is, the lens holder 3 has a main body 3a that is integral with the cylinder lens 2b, and a tubular portion 3b that fits into the tubular portion 1b of the lens barrel 1 and is bonded to the lens barrel 1 with an adhesive 1c. Before the lens holder 3 is assembled to the lens barrel 1, the reference numeral 2a is inserted into the main body 3a of the lens holder 3 and abuts on a step 3c provided on the inner surface of the main body 3a. It is fixed in place. A pair of grips 3e is integrally provided on the outer surface of the lens holder 3. In addition,
The collimator lens 2a may be brought into contact with the step 3c of the lens holder 3 and then adhered to the lens holder 3 with an adhesive.

At the time of assembling the light source unit E ₁ , the lens holder 3 having the collimator lens 2a assembled therein is fitted into the cylindrical portion 1b of the lens barrel 1, and the semiconductor laser 1a and a rotary polygon mirror (not shown) are fitted by a method described later. After performing optical alignment, an adhesive is injected between the tubular portion 1b of the lens barrel 1 and the tubular portion 3b of the lens holder 3 to integrate the two, and the integrated light source unit E Screw ₁ to the case not shown.

The collimator lens 2a is the semiconductor laser 1
The laser light, which is the illumination light generated from a, is expanded into parallel light of a predetermined cross section, and the cylinder lens 2b converts the expanded parallel light flux L ₁ into a rotating polyhedral surface (not shown) as shown in FIG. The light is condensed linearly on the reflecting surface of the mirror. That is, the cylinder lens 2b has a function of converging the parallel light flux L ₁ in the sub-scanning direction (z-axis direction) perpendicular to the optical axis and linearly condensing it at the focus position S on the reflecting surface of the rotary polygon mirror. To do. Therefore, when assembling the light source unit E ₁ , the cylindrical portion 3b of the lens holder 3 is replaced by the cylindrical portion 1 of the lens barrel 1.
Before adhering to b, the lens holder 3 is first moved in the x-axis direction (optical axis direction) by grasping the grip portion 3e to adjust the parallelism by the collimator lens 2a. Depending on the scanning system, the light beam from the collimator lens in the main scanning direction may be slightly shifted from parallel and used as divergent or convergent light. In this case, if the desired value is set by adjusting the lens holder 3 in the x-axis direction. Good. Similarly, the deviation angle of the parallel light flux L _{1 in} the z-axis direction is adjusted by moving the lens holder 3 in the z-axis direction, and the deviation angle of the parallel light flux L _{1 in} the y-axis direction moves the lens holder 3 in the y-axis direction. To adjust. Next, the lens holder 3 is rotated to adjust the rotation angle θ around the optical axis, adjust the inclination angle of the linear focal point position S on the reflecting surface of the rotary polygon mirror, and adjust this to the main scanning direction (y-axis direction). To match. After the optical alignment is completed in this way, the lens holder 3 is attached to the lens barrel 1 as described above.
Glue to.

In the past, the lens holder for holding the collimator lens and the cylinder lens were separately provided and separately mounted on the housing. Therefore, the mounting position of the lens holder on the housing was changed to align the optical axis of the collimator lens. It is necessary to position the cylinder lens with respect to the collimator lens each time it is performed, and it takes a lot of labor and time to assemble the cylinder lens, and in addition, it is necessary to finish the mounting portion of the cylinder lens with high accuracy. In this embodiment, the lens holder for holding the collimator lens and the cylinder lens are integrated, and it is not necessary to align the cylinder lens each time the optical axis of the collimator lens is aligned, and the cylinder lens itself and the housing are positioned. Does not require high-precision finishing for matching.

Therefore, according to this embodiment, it is possible to greatly reduce the cost of the optical system of the light source part of the optical scanning device, simplify the assembling work, and reduce the number of assembling parts.

The focus position of the cylinder lens changes by adjusting the parallelism of the parallel light beam in the main scanning direction, but the change in the focus position has an influence on the point image on the rotating drum as compared with the parallelism of the parallel light beam. It is small and can be ignored. For example, the imaging magnification in the sub-scanning direction of the imaging lens system for imaging the parallel light beam deflected and scanned by the rotary polygon mirror on the rotating drum is usually about 2 times, and the movement amount of the lens holder is Δx. When the focal position S of the cylinder lens moves by Δx, the maximum amount of movement of the point image on the rotating drum in the sub-scanning direction (y-axis direction) is 4 × Δx.
However, the amount of movement of the point image due to the deviation of the parallelism of the parallel light flux is usually 100 × Δx or more.

If the change in the focal position of the cylinder lens cannot be ignored, the cylinder lens and the collimator lens may be configured to be movable in the optical axis direction together with the lens barrel.

FIG. 3 shows a first modified example of the present embodiment, in which, instead of coupling the collimator lens 2a to the lens holder 3 by heat caulking or bonding, a similar glass collimator lens 22a is transparent. The lens holder 23 made of plastic is mounted as an insert in a mold and molded integrally with the lens holder 23. According to this modification, the manufacturing cost of the optical scanning device can be further reduced by omitting the step of fixing the collimator lens to the lens holder. The lens holder 23 has a cylinder lens 22b made of the same transparent plastic therein and is integrated with the surface of the collimator lens 22a.

FIG. 4 shows a second modification of this embodiment, which is similar to the first modification in that the collimator lens 32 is used.
The cylindrical portion 33b of the lens holder 33, in which a and the cylinder lens 32b are integrally molded, is inserted into the sub-lens barrel 34, which is a light-shielding means made of an opaque material, and is attached thereto. 34 is attached to the lens barrel 1. The sub-lens barrel 34 is attached to the lens holder 33 by snap-fitting a claw 33a provided on the inner end of the lens holder 33 into a groove 34a provided on the inner surface of the sub-lens barrel 34. An opening member 34b is provided inside the sub barrel 34. According to this modification, by covering the outer side of the transparent lens holder 33 with the sub barrel 34, it is possible to supplement the light blocking effect and prevent disturbance due to scattered light.

In order to maintain good lens aberration,
As in the first and second modifications, it is desirable to integrate a cylinder lens on the surface of the collimator lens having a smaller curvature and arrange the cylinder lens on the upstream side of the optical path of the laser beam.

[0022]

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

The cost of optical system parts including anamorphic lenses such as collimator lenses and cylinder lenses can be reduced, and the number of parts to be assembled and the assembling process can be greatly promoted. As a result, the manufacturing cost of the optical scanning device can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a partial schematic cross-sectional view showing only a light source portion of an optical scanning device according to an embodiment.

FIG. 2 is a perspective view showing a relationship between the apparatus of FIG. 1 and a parallel light beam condensed by the apparatus.

FIG. 3 is an enlarged partial sectional view showing an enlarged main part of a light source portion according to a first modification.

FIG. 4 is an enlarged partial sectional view showing an enlarged main part of a light source portion according to a second modification.

FIG. 5 is an explanatory diagram illustrating a general optical scanning device.

FIG. 6 is a partial schematic cross-sectional view showing a conventional example.

[Explanation of symbols]

 1 lens barrel 1a semiconductor lasers 2a, 22a, 32a collimator lenses 2b, 22b, 32b cylinder lenses 3, 23, 33 lens holder 34 sub lens barrel

Claims (7)

[Claims] 1. Illumination light generated from a light source is collimated by a collimator lens, irradiates a rotary polygon mirror through at least one anamorphic lens, and the reflected light is imaged on a photoconductor by an imaging lens system. The optical scanning device, wherein the collimator lens is held by a lens holding unit that is integral with the anamorphic lens. 2. The optical scanning device according to claim 1, wherein the anamorphic lens and the lens holding means are integrally molded of a transparent plastic material. 3. The optical scanning device according to claim 1, wherein the collimator lens is made of glass. 4. The optical scanning device according to claim 1, wherein the collimator lens is integrally embedded in the lens holding means. 5. The optical scanning device according to claim 1, wherein the surface of the lens holding means is covered with a light shielding means. 6. The optical scanning device according to claim 1, wherein the anamorphic lens is a cylinder lens. 7. The lens holding means is fixed to a lens barrel which is integral with the light source.
The optical scanning device according to claim 1.