JPH0882758A - Optical scanner - Google Patents

Abstract

PURPOSE: To make light beam to be made incident on a deflection surface campact by skew incidence and to relatively easily realize the skew incidence with high precision. CONSTITUTION: A semiconductor laser device 32, a collimate lens 33, a cylindrical lens 34, and aperture 35, a flat convex lens 36 and a bent mirror 37 are integrated with each other as an optical block 40, and the optical block 40 is fixed to a base of a housing 31 by matching the attaching reference surface of the optical block 40 with the attaching reference surface formed on the base of the housing 31, thereby a skew incident angle of a laser beam incident on a deflection surface of a polygon mirror 38 from the bent mirror 37 is matched with a prescribed incident angle.

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 applicable to a laser printer or the like.

[0002]

2. Description of the Related Art The electrophotographic printing method has been applied to copying machines, printers, facsimiles and the like, and has become an important printing technology. In this printing method, in order to form an electrostatic latent image, exposure is performed after charging the photoconductor, and there are various methods in this exposure method.

An analog exposure system is adopted in the case of a copying machine, while a digital exposure system is adopted in a printer and a facsimile. The digital exposure method uses a solid-state device such as LED (light emitting diode), LCD (liquid crystal device), EEH (edge emitter head), or rotates a polygon mirror or hologram disk. There is a method of deflecting and scanning a laser beam. Recently, a method of deflecting and scanning a laser beam using a polygon mirror has become mainstream.

The method using a polygon mirror is a pre-objective type in which a so-called fθ lens is used to convert a light beam into a convergent light after being deflected by the polygon mirror, and a post which converts a light beam into a convergent light before being deflected in a polygon mirror. The objective type is known.

As a post-objective type optical scanning device, for example, Japanese Patent Laid-Open No. 1-177512 is known. As shown in FIG. 4, the light beam from the light source 1 passes through the collimator lens 2, the cylinder lens 3 and the plano-convex lens 4 in this order, and is applied to the reflecting surface of the polygon mirror 5. The polygon mirror 5 is rotated at a constant speed by a scanner motor 6 and deflects and scans an incident light beam. The deflected and scanned light beam is corrected by the aspherical surface correction lens 7 for converging the light beam, and the photosensitive surface of the photosensitive drum 8 is scanned and exposed. In the polygon mirror 5 used here, each reflecting surface is an elliptical surface having power in the main scanning direction.

In this device, the light source 1,
The optical system of the collimator lens 2, the cylinder lens 3 and the plano-convex lens 4 is arranged on the same side as the aspherical surface correction lens 7 for compactness.

In this case, in order to maintain left-right symmetry with respect to the entire scanning width of the deflected light beam, the light beam is made to enter from the plane located at the center of the scanning width toward the rotation axis of the polygon mirror 5. And in order to prevent the deflected light beam from hitting the optical system, the polygon mirror 5
The light beam is made incident at an angle inclined by a predetermined angle downward with respect to a plane perpendicular to the rotation axis of the. That is, the incidence of the light beam from the optical system of the light source 1, the collimator lens 2, the cylinder lens 3, and the plano-convex lens 4 on the polygon mirror 5 is skewed.

On the other hand, with the progress of computers, the demand for colorization of printers is increasing. In a full-color printer, it is known that the electrophotographic method is superior to other methods in terms of print quality.

Among electrophotographic color printers, there are 1 developing system, 1 exposing system, 4 developing system, 4 exposing system, etc. The 4 developing system, 4 exposing system is called a tandem system. Since it only needs to pass the paper once, it has an advantage that it can cope with high speed. On the other hand, in the tandem system, since the scanning position accuracy of the exposure system appears as a color shift as it is, a high scanning position accuracy is required for the optical scanning device used.

Therefore, in addition to the positional accuracy of the optical system after deflection such as the aspherical surface correction lens 7, high positional accuracy is required for the optical system for generating the light beam skew-incident on the polygon mirror 5.

In such an optical scanning device, as a method for obtaining a predetermined skew incident angle, for example, Japanese Unexamined Patent Publication No. Hei 4-
A method of using a mirror as in Japanese Patent No. 317022,
There is known a method of using a lens as disclosed in JP-A-62-30214.

The one disclosed in JP-A-4-317022 is
As shown in FIG. 5, the laser generator 12, the cylinder lens 13, the reflection mirror 14, the polygon mirror 15, the reflection mirrors 16 and 17 are housed in the housing 11, and the laser light from the laser generator 12 is transferred to the cylinder lens 13. Through the reflecting mirror 14 to be skew-incident on the deflecting surface of the polygon mirror 15, and the light beam deflected and scanned by the polygon mirror 15 is reflected by the reflecting mirrors 16 and 17, and further, via the elongated lens 18, the photosensitive drum ( (Not shown) is configured to be incident and image-formed. In this case, the reflection mirror 14 is arranged so that the light beam from the cylinder lens 13 is tilted by a predetermined angle in the horizontal direction so that the light beam from the cylinder lens 13 is skew-injected toward the rotation axis of the polygon mirror 15, and also has an inclination angle β in the upward direction. are doing. Reflection mirror 14
The angle is obtained by providing a mirror-attached contact surface on the housing 11 formed by a method such as molding and pressing it with a leaf spring.

The one disclosed in JP-A-62-30214 is
As shown in FIG. 6, the divergent light beam from the semiconductor laser 21 is made into a parallel light beam by the collimator lens 22, is bent by the scanning lens 23, and is skew-injected into the polygon mirror 24, so that the deflection scanning light from the polygon mirror 24 is exposed. A scanning image is formed on the drum 25. That is, the scanning lens 3 is formed by a part of a spherical lens, the optical axis is perpendicular to the rotation axis of the polygon mirror 24, and the incident height of the light beam is h.

[0014]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
When a skew angle is obtained with a reflection mirror as in Japanese Patent Publication No. 2), the optical path is bent in a plane by 90 degrees (planar projection angle),
At the same time, when an attempt is made to obtain a skew angle θz degree, the arrangement angle of the reflection mirror is obtained as shown in FIG.

That is, when the x, y, z coordinate system is taken as shown in the figure, the beam Li incident on the reflection mirror S and the beam Lo emitted therefrom are expressed in vector as Li = [1, 0, 0] Lo = [0, cos (θz), sin (θz)]. At this time, the direction cosine vector Vs of the normal line of the reflecting mirror S is Vs = Li + Lo, and the standardized vector Vs 'is Vs' = Vs / | Vs |.

For example, if the skew angle θz is 5 degrees, then Vs' = [0.707107,0.704416,0.061628].

The method disclosed in Japanese Patent Laid-Open No. 4-317022 is
The accuracy of the mirror surface is determined by the accuracy of the housing 11, but this mirror-equipped contact surface having a three-dimensional inclination becomes extremely difficult when manufacturing a mold and when measuring the accuracy of a molded product. . Further, the cylinder lens 13 also needs to be mounted parallel to the skew angle, but this also depends on the housing precision. Furthermore, the relative positional relationship between the reflection mirror 14 and the other lenses is also determined by the accuracy of the housing.

Therefore, the method disclosed in Japanese Patent Laid-Open No. 4-317022 cannot obtain high accuracy and is difficult to apply to a tandem type color printer.

Further, as in Japanese Patent Laid-Open No. 62-30214, in order to obtain a highly accurate incident beam to a polygon mirror by a method of performing skew incidence with an off-axis lens, the eccentricity of the optical axis of the lens and the outer shape tolerance are required. It is necessary to raise it sufficiently, which leads to an increase in cost. In addition, there is a problem that a beam having a small diameter cannot be obtained because the aberration increases by passing the light beam off the axis of the lens.

Therefore, the present invention provides an optical scanning device which can realize compactness by making the light beam incident on the deflecting surface of the polygon mirror skew-incident, and can realize skew incidence relatively easily with high accuracy.

[0021]

The invention according to claim 1 is
A light source, first optical means for converting the light beam from the light source into a light beam forming a line image, a folding mirror for reflecting the light beam from the first optical means and bending it at a right angle, The light beam from the optical means is reflected by a bending mirror and has a deflecting surface near the line image, and a polygon mirror for deflecting and scanning the light beam, a motor for holding and rotating the polygon mirror, and a polygon mirror are used. Second optical means for correcting the light beam of the first image to be formed on the scanning surface and performing the desired scanning, and is housed in the housing.
The optical means and the bending mirror are integrated as an optical block, and a mounting reference surface for mounting the optical block is formed on the base of the housing. The mounting reference surface is such that the light beam from the optical block is against the deflection surface of the polygon mirror. The skew incidence is set at an angle inclined by a predetermined angle with respect to a direction perpendicular to the rotation axis of the lever polygon mirror.

[0022]

According to the present invention, the light source, the first optical means and the bending mirror are integrated as an optical block, and the mounting reference surface for mounting the optical block is formed on the base of the housing to form the first optical means. Also, it is possible to make the desired skew incidence of the light beam on the deflection surface of the polygon mirror by mounting the optical block on the mounting reference surface without requiring high precision individually on the surface on which the bending mirror is mounted.

[0023]

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

As shown in FIGS. 1 and 2, a semiconductor laser device 32 is arranged as a light source on one end side of a base of a rectangular housing 31, and a laser beam as a light beam is emitted from the semiconductor laser device 32 as a first light beam. It is incident on the optical means.

The first optical means comprises a collimator lens 33, a cylinder lens 34, an aperture 35 and a plano-convex lens 36. After converting the laser from the semiconductor laser device 32 into parallel light by the collimator lens 33, the cylinder lens is formed. 34, the aperture 35 and the plano-convex lens 36 convert to a desired converged laser beam.

The convergent laser light is bent by a bending mirror 37 by approximately 90 °, and at the same time, it is deflected upward so as to be skew-injected at a predetermined angle, and is then polygon mirror 38.
Is incident on the deflecting surface and is formed as a line image on the deflecting surface.

As shown in FIG. 3, the semiconductor laser device 32, the collimator lens 33, the cylinder lens 34, the aperture 35, the plano-convex lens 36, and the bending mirror 37 are fixed to the base member 39 with a predetermined space therebetween, It is integrated as an optical block 40. In addition, (b) of FIG.
The folding mirror 37 is omitted.

The bottom of the base member 39 is shown in FIG.
As shown in, the mounting reference plane H and the mounting reference boss 41 are formed. Then, the mounting reference plane H of the optical block 40 is aligned with the mounting reference plane I formed on the base of the housing 31, and the optical block 40 is fixed to the base of the housing 31 by screws 42.

The polygon mirror 38 is integrally attached to the scanner motor 43, and is rotated at a constant speed by the motor 43.

The polygon mirror 38 is rotated to deflect and scan the incident convergent laser beam, and the deflected and scanned laser beam is reflected by the M mirror 44 and the L mirror 45.
An image is formed on the photosensitive surface of the photosensitive drum 47 through the aspherical correction lens 46 that constitutes the second optical means.

When the scanning laser light from the polygon mirror 38 deviates to one side from the effective scanning range on the photosensitive drum 47, the scanning laser light is reflected by the reflection mirror 48 arranged in front of the aspherical correction lens 46. The position detecting element 49 reflects and receives the light. The position detection element 49 serves as a reference for determining the scanning start position, and the exposure operation for the photosensitive drum 47 is started at a predetermined timing after the position detection element 49 detects the laser beam.

This optical scanning device is a post-objective type optical scanning device, and correction of field curvature, fθ error, etc.
The deflecting surface of the polygon mirror 38 is formed into an elliptic cylindrical shape, and this deflecting surface is combined with the aspherical correction lens 46.

In this embodiment, the semiconductor laser device 32, the collimator lens 33, the cylinder lens 34, the aperture 35, and the plano-convex lens 36 are arranged perpendicular to the mounting reference plane H of the base member 39. In addition, the bending mirror 37 is placed in a plane perpendicular to and parallel to the mounting reference plane H.
Place it at an angle of 5 degrees. Therefore, the laser light reflected by the bending mirror 37 is 90 degrees in a plane parallel to the mounting reference plane H.
It will be bent once.

As described above, the optical block 40 is mounted on the mounting reference plane H by the semiconductor laser device 32 and the collimator lens 3.
3, the cylinder lens 34, the aperture 35, and the plano-convex lens 36 are arranged vertically, and the folding mirror 37 is arranged vertically and in a plane parallel to each other at an angle of 45 degrees.
Whether the base member 39 is formed by injection molding of resin or die-casting of aluminum or zinc, for example, it is possible to manufacture a highly accurate optical block 40 that is easy to process the mold and evaluate after molding.

Further, even when the precision higher than the molding precision is required and the angle of the bending mirror 37 needs to be adjusted, it becomes easy to evaluate the parallelism or perpendicularity of the laser beam with respect to the reference mounting surface. The adjustment work itself becomes easy, and highly accurate adjustment is possible.

Thus, the semiconductor laser device 32 and the collimator lens 3 are attached to the mounting reference plane H of the optical block 40.
An optical block 40 in which each optical system is accurately arranged by aligning the optical axis with the optical axis 3 and adjusting the optical axes of the cylinder lens 34, the aperture 35, and the plano-convex lens 36 and adjusting the focus.
Is positioned by the boss 41 of the optical block 40 on the mounting reference plane I formed on the base of the housing 31, and the mounting reference plane H of the optical block 40 is aligned with the optical block 40.
Is fixed to the base of the housing 31 with a screw 42, the laser light from the optical block 40, that is, the laser light reflected by the bending mirror 37 enters the deflecting surface of the polygon mirror 38 at a predetermined skew incident angle. Like

That is, if the mounting reference plane I formed on the base of the housing 31 is set at an angle that coincides with the skew incident angle of the laser light incident on the deflection surface of the polygon mirror 38, the mounting reference plane I is optically aligned. The laser light from the optical block 40 is incident on the deflection surface of the polygon mirror 38 at a predetermined skew incident angle only by adjusting the attachment reference surface H of the block 40.

As described above, the three-dimensional arrangement of the bending mirror 37 for the skew incidence of the laser light is the optical block 4.
It can be easily and accurately realized by a simple work of arranging 0 on the base of the housing 31.

Moreover, since the laser beam is skew-incident on the polygon mirror 38, the optical block 40 can be arranged on the same side as the M mirror 44 and the L mirror 45, and the apparatus can be made compact.

In the above-mentioned embodiment, the present invention is applied to the post-objective type optical scanning device, but the present invention is not necessarily limited to this, and it can be applied to the pre-objective type optical scanning device. Of course.

[0041]

As described above, according to the present invention, the light beam incident on the deflecting surface of the polygon mirror can be skewed to realize compactness, and the skew incidence can be realized with high accuracy and relatively easily.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

3A and 3B show a configuration of an optical block of the same embodiment, FIG. 3A is a plan view, and FIG. 3B is a sectional view taken along line BB in FIG. 3A.

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

FIG. 5 is a perspective view showing another conventional example.

FIG. 6 is a configuration diagram showing another conventional example.

FIG. 7 is a schematic diagram for obtaining a mirror surface normal of a bending mirror.

[Explanation of symbols]

 31 ... Housing 32 ... Semiconductor laser device (light source) 33 ... Collimator lens 34 ... Cylinder lens 36 ... Plano-convex lens 37 ... Bending mirror 38 ... Polygon mirror 40 ... Optical block 43 ... Scanner motor 46 ... Aspherical correction lens 47 ... Photosensitive drum H, I ... Standard mounting surface

Claims (1)

[Claims] 1. A light source, first optical means for converting a light beam from the light source into a light beam forming a line image, and bending for reflecting the light beam from the first optical means and bending the light beam at a right angle. A mirror, a polygon mirror for reflecting the light beam from the first optical means by the bending mirror and having a deflecting surface near the line image, for deflecting and scanning the light beam, and holding and rotating the polygon mirror. A drive motor and second optical means for correcting the light beam from the polygon mirror to form an image on a scanning surface and perform desired scanning are housed in a housing. The optical means and the bending mirror are integrated as an optical block, and a mounting reference surface for mounting the optical block is formed on the base of the housing, and the mounting reference surface is a light beam from the optical block. The optical scanning device is set so that the skew incidence is performed on the deflection surface of the polygon mirror at an angle inclined by a predetermined angle with respect to the direction perpendicular to the rotation axis of the polygon mirror.