JPH0675181A - Scanning optical device and optical member used for this scanning optical device - Google Patents

Abstract

(57) [Abstract] [Purpose] When a plastic lens is attached to a scanning optical device, the position of the lens can be easily adjusted. A light source device for generating a laser beam, a collimator lens for making the laser beam a substantially parallel beam, a scanning device for scanning the parallel beam on a photoconductor, and a scanning device for scanning the photobeam at a constant speed. In the scanning optical device, the optical member has at least one plastic lens, and the plastic lens itself has means for indicating information when the plastic lens is molded. A scanning optical device having.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an image on a recording medium using a laser beam such as a laser beam printer and a laser facsimile, and more particularly to a scanning optical system for scanning the recording medium with the laser beam. The present invention relates to a device and an optical member used in the scanning optical device.

[0002]

2. Description of the Related Art An outline of a scanning optical device used in a laser beam printer, a laser facsimile, etc. will be described with reference to FIG.

The light beam whose emission is controlled by image information has a semiconductor laser for emitting the light beam and a light source unit 20 having a collimator lens for making the divergent light beam from the semiconductor laser substantially parallel light. More parallel light is emitted and is linearly condensed on the deflecting / reflecting surface of the rotary polygon mirror 30 by the cylindrical lens 12 having a curvature only in the direction perpendicular to the scanning direction. The body drum 60 is scanned.

Here, the scanning light L scanned on the photosensitive drum 60 needs to be light that moves on the surface of the photosensitive drum 60 at a constant speed, and a desired beam diameter is applied to the surface of the photosensitive drum 60. It has to form. The imaging lenses 10 and 11 having such a function are referred to as fθ lenses, and are arranged inside the optical frame 40.

In the figure, reference numeral 50 indicates that the scanning light L is the photosensitive drum 6
Reference numeral 70 is an adjustment spacer for scanning to a desired position on 0, and 70 is a photodetector for horizontally synchronizing an image, which is a light beam on the image writing side. Is folded back and detected by the mirror 71.

[0006]

By the way, in recent years, in laser beam printers and laser facsimiles, it is desired that printed images have higher quality and lower price. To this end, the fθ lens included in the scanning optical device is required. Also, it is desired to reduce the manufacturing cost, and further, it is desired to make the diameter of the light beam condensed on the photosensitive drum smaller and more accurate.

Therefore, as the fθ lens, a plastic lens capable of easily forming a complicated aspherical shape has been used.

However, in the case of a plastic lens, it is usually manufactured by injection molding. However, due to variations in shrinkage due to heat, even if the mold has the same mold structure or molds of the same size, the curvature has a peculiar habit. May become the lens of.

This causes a problem that the light beam cannot be converged on the photosensitive drum with high accuracy.

[0010]

Therefore, in the present invention, in order to solve the above-mentioned problems, the plastic lens is provided with information at the time of molding, and the adjustment can be made in accordance with the information to suit the individual lens. This is a structure for irradiating the photosensitive drum with a light beam with high accuracy by providing the means in the scanning optical device.

[0011]

EXAMPLE An example of the present invention will be described with reference to FIG.

Reference numeral 1 shown in FIG. 1 denotes a plastic fθ lens in a scanning optical device, which is made of PMMA resin, polycarbonate (PC), polystyrene (PS) or the like because of its optical characteristics such as transmittance, refractive index and birefringence. Is used as.

This single-lens fθ lens 1 is used in place of the double-lens fθ lens (imaging lenses 10 and 11) in the scanning optical device shown in FIG.

An edge is provided around the lens effective portion of the fθ lens 1 in order to improve the moldability, and in particular, the bottom has a reference surface that can be stably and accurately fixed to the optical frame 40 or the like. In addition, a bonding seat surface for bonding and fixing to the optical frame 40 as described in 3 is also provided.

Further, a protrusion such as 2 is provided on the edge provided on the upper end side of the lens so that the model number and date information at the time of molding can be read.

Next, a method for obtaining a desired light beam diameter by correcting the variation in the optical characteristics by using the molding information of this lens will be described.

The optical characteristics required for the scanning optical device are, as described above, the fθ characteristic that the light beam moves at a constant speed on the surface of the photosensitive drum, and the beam diameter is almost the same at any position on the surface of the photosensitive drum. There are other characteristics such as the image forming characteristics that can obtain the same, and the characteristics that almost the same light intensity can be obtained at any position on the surface of the photoconductor drum. In addition to these, another important characteristic is the tilting of the rotating polygon mirror. A tilt correction characteristic for correcting the positional deviation of the scanning light due to is also required.

For this reason, the above-mentioned cylindrical lens 12 in FIG. 7 is used to converge the light beam linearly only in the direction perpendicular to the scanning direction on the deflecting / reflecting surface of the rotating polygonal mirror. The fθ lens of 1 has the characteristic that the light beam deflected and scanned by the mirror is again focused on the surface of the photosensitive drum.

Therefore, the curvature of the fθ lens is required in the direction perpendicular to the scanning direction (direction of arrow A: meridional direction) rather than in the scanning direction (direction in which the rotary polygon mirror deflects and scans the light beam). The variation in curvature is also small. In the case of this curvature variation, the converging position of the light beam in the meridional direction varies before and after the surface of the photosensitive drum, as shown in FIG. Further, if the curvature in the meridional direction varies in the longitudinal direction of the fθ lens, as shown by the broken line in FIG. 3, the focus position of the light beam differs depending on the position of the surface of the photosensitive drum.

2 and 3 are views showing the focus position in the meridional direction of the light beam focused on the photosensitive drum used in the embodiment of the present invention.

Therefore, if the curvature of the f.theta. Lens and the distribution characteristic of the curvature are inspected in advance and are managed as molding lot data of the f.theta. Lens, the desired beam can be adjusted by the following adjustment of the scanning optical device. The diameter is obtained.

The light beam is linearly focused on the deflecting and reflecting surface of the rotary polygon mirror 30 by the cylindrical lens 12; however, when the cylindrical lens 12 is moved in the optical axis direction, the beam on the surface of the photosensitive drum 60 is formed. The diameter can be changed. Therefore, by reading the molding information of the lens that allows the curvature of the fθ lens to be grasped by the two protrusions, the cylindrical lens 12 may be arranged at a position corresponding to each.

This is the same even when the fθ lens has a curvature distribution in the longitudinal direction. For example, in the case of having a light-collection distribution characteristic as shown by the broken line in FIG. 3, the light beam is most condensed on the surface of the photoconductor drum at the position of point B (see (2) If the cylindrical lens is adjusted, the light beam is most focused on the surface of the photoconductor drum when considering the entire area.

As described above, if the fθ lens has information that clearly indicates the molding time of this lens, this can be read by a detection sensor or the like, and the curvature characteristics of the lens can be inspected in advance for each molding lot. For example, it is much more troublesome than inspecting all the fθ lenses and disposing the cylindrical lenses at predetermined positions.

FIG. 4 is a diagram showing a scanning optical device for correcting variations in the curvature of the fθ lens in the longitudinal direction. The basic structure of the device is the same as that of the device described above with reference to FIG.

Reference numeral 5 denotes a lens holder for the fθ lens 1, and the fθ lens 1 is positioned on the lens holder 5 and fixed with an adhesive or the like. Further, the lens holder 5 is positioned with respect to the optical frame 40 by a pin 6 in the optical axis direction. However, there is no restriction in the facing direction of the pin 6 and it can rotate in the direction of arrow C. In this way, the fθ lens 1 is configured to rotate within the deflecting surface (the light beam plane that is formed by the deflecting and reflecting surface of the rotating polygonal mirror and is formed with time).

By configuring the device as described above,
By rotating the lens holder with respect to the fθ lens having the light-collecting characteristic as shown by the broken line in FIG. 5, it becomes possible to correct the light-collecting characteristic as shown by the solid line. That is, in the fθ lens having the condensing characteristics as shown in FIG. 5, if the lens holder 5 is moved slightly clockwise and the cylindrical lens 12 is adjusted, a desired beam diameter can be obtained over the entire area of the photosensitive drum. Like

FIG. 5 is a diagram showing the focus position in the meridional direction of the light beam focused on the photosensitive drum used in the embodiment of the present invention.

In the scanning optical device of the present invention,
As a means to obtain the molding information of the fθ lens, the method of providing a projection on the edge of the lens has been described. The same effect can be obtained by the method as described above, and the same effect can be obtained by a method of sticking a label such as the bar code label 4 on the fθ lens as shown in FIG.

[0030]

As described above, by clearly indicating the lens molding information on the fθ lens molded from plastic, the position of the cylindrical lens can be set based on this information. A high-precision light beam can always be obtained, and a high-quality printed image can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an fθ lens showing an embodiment of the present invention.

FIG. 2 is a diagram showing the focus position in the meridional direction of the light beam focused on the photosensitive drum used in the embodiment of the present invention.

FIG. 3 is a diagram showing the focus position in the meridional direction of the light beam focused on the photosensitive drum used in the embodiment of the present invention.

FIG. 4 is a configuration diagram of a scanning optical device showing an embodiment of the present invention.

FIG. 5 is a diagram showing the focus position in the meridional direction of the light beam focused on the photosensitive drum used in the embodiment of the present invention.

FIG. 6 is a configuration diagram of an fθ lens showing an embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional scanning optical device.

[Explanation of symbols]

 1 Plastic fθ lens 2 Protrusion for layering by molding lot 4 Label for layering by molding lot 5 Lens holder 12 Cylindrical lens 60 Photoreceptor drum

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kimiko Aoyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A light source device for generating a laser beam, a collimator lens for making the laser beam a substantially parallel beam, a scanning device for scanning the parallel beam on a photoconductor, and a constant velocity of the scanning light on the photoconductor. And a scanning optical device including an optical member having a function capable of scanning with at least one optical member.
A scanning optical device having two plastic lenses, and the plastic lens itself has means for clearly indicating information when the plastic lens is molded. 2. The scanning optical device according to claim 1, further comprising means for moving the position of the plastic lens in the scanning optical device. 3. An optical member used in a scanning optical device, wherein the optical member has at least one plastic lens, and the plastic lens itself has means for indicating information when the plastic lens is molded. An optical member used in a scanning optical device characterized in that: 4. A scanning optical device comprising a light source unit, a deflector for deflecting a light beam from the light source unit, and an optical member for forming an image of a light beam deflected and scanned by the deflector on a surface to be scanned. The scanning optical device is characterized in that the optical member has at least one plastic lens, and the plastic lens itself has means for clearly indicating information when the plastic lens is molded.