JPH03219205A - Optical scanner - Google Patents

Abstract

PURPOSE:To prevent picture quality from deteriorating by providing a light beam converging means at the projection end of the light beam of an optical waveguide array where the light beam from a light source is propagated. CONSTITUTION:The light beam emitted by the light source 11 is guided by a light beam distributing means 4 to the incidence port 15a of the optical waveguide array 15 and made incident, and then propagated in the optical waveguide and projected from the projection port 15b to make a scan with the light beam. Then the light beam converging means 16 is provided at the projection end 15b of the optical waveguide array 15, and the light beam project ed from each optical waveguide is converged. Consequently, even when the interval between the optical waveguide array 15 and a photosensitive body 20 is increased, the crosstalk of the light beam, projected from the projection port 15b of the optical waveguide, on the photosensitive body 20 is precluded to prevent the optical waveguide array tip 15a from being contaminated with foreign matter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical scanning device used in optical printers and the like.

[Conventional technology]

In recent years, optical printers using optical scanning devices have been used as computer output devices in place of line printers that have been conventionally used.

Hereinafter, such an optical scanning device 40 will be explained with reference to FIG. 4.

In FIG. 4, a light beam emitted from a light source 41 is guided to a polygon mirror 44 via a collimating lens 42 and a condensing lens 43. And polygon mirror 44
Due to the rotation of the optical waveguide array 45, this light beam is sequentially incident on each optical waveguide constituting the optical waveguide array 45.

The light beam incident on the guide waveguide is propagated within the optical waveguide, and sequentially exits from the exit of the optical waveguide at a predetermined aperture angle.
A light beam is scanned on the photosensitive drum 50.

[Problem to be solved by the invention]

However, in the optical scanning device 40 as described above, the numerical aperture NA of the optical waveguide is determined by the refractive index n of the core of each optical waveguide.
1. It is given by the following formula from the refractive index n2 of the cladding.

s j n (r) =NA NA= (n 12-n 22)”2 PMMA is a typical material for resin-based optical waveguides.
When (n 1 = 1.49) is used for the core and a fluorine resin (n 2 = 1.40) is used for the cladding, NA = 0.5 from the above formula, and the angle becomes r-30°.

Therefore, the diameter of the light beam emitted from the output aperture of the optical waveguide certainly increases as it moves away from the output aperture of the optical waveguide. For this reason, the diameter of the optical waveguide was set to 85 μm.
m, the optical waveguide array 45 and the photosensitive drum 50
If the distance between the two is not set to 50 μm or less, the light beams emitted from adjacent optical waveguides will interfere with each other, resulting in so-called crosstalk, which will cause deterioration of image quality.

However, with the above-mentioned spacing of 50 μm or less, there is a problem that foreign matter such as toner and paper powder that cannot be removed in the cleaning process adheres to the tip of the optical waveguide array 45, which adversely affects the exposure of the photosensitive drum. .

The present invention has been made to solve the above-mentioned problems, and it increases the distance between the optical waveguide array and the photoreceptor, prevents the tip of the optical waveguide array from being contaminated by foreign matter, and also improves the output port of the optical waveguide. An object of the present invention is to provide an optical scanning device that can prevent deterioration of image quality due to crosstalk of a light beam emitted from a photosensitive drum on a photosensitive drum.

[Means to solve the problem]

In order to achieve this object, the present invention provides a light source that emits a light beam based on an image signal, an optical waveguide array formed by arranging a large number of optical waveguides that propagate the light beam from the light source, and a light source that emits a light beam from the light source. The optical scanning device is equipped with a light beam distribution means for sequentially inputting the beam into the plurality of optical waveguides, and the light beam focusing means is provided at the light beam output end of the optical waveguide array.

[Effect]

According to the present invention having the above configuration, the light beam emitted from the light source is sequentially guided by the light beam distribution means to the entrance of each optical waveguide of the optical waveguide array and is made incident thereon. Then, this light beam is propagated within the optical waveguide, and is sequentially emitted from the exit of the optical waveguide, thereby performing scanning of the light beam. At this time, a light beam focusing means is provided at the output end of the optical waveguide array, and the light beams emitted from each optical waveguide are focused, so even if the distance between the optical waveguide array and the photoreceptor is increased, the output of the optical waveguide It is now possible to prevent crosstalk of the light beam emitted from the mouth onto the photoconductor, allowing clear exposure on the photoconductor, and also preventing contamination by foreign objects at the tip of the optical waveguide array. Become.

〔Example〕

An embodiment embodying the present invention will be described below with reference to the drawings.

FIG. 1 shows an optical recording device according to the present invention. In FIG. 1, an optical scanning device 10 includes a light source 11 that generates a light beam based on an image signal, and a light beam from the light source 11 that is transferred to a photosensitive drum 2.
The optical waveguide array 15 includes an optical waveguide array 15 in which a large number of optical waveguides are lined up for propagation to 0, and a polygon mirror 14 for sequentially making the light beam from the light source 11 enter the entrance of each optical waveguide of the optical waveguide array 15. ing.

The light source 11 generates a light beam by blinking in response to an electric signal based on image information, and is specifically a laser diode (LD) or a light emitting diode (LED).
Semiconductor light sources such as the following are used.

A collimating lens 12 is provided downstream in the propagation direction of the light beam from the light source 11 to convert the light beam from the light source 11 into a parallel beam. A condenser lens 13 is provided further downstream of the collimator lens 12 to condense the light emitted from the collimator lens 12 onto a polygon mirror 14 .

The polygon mirror 14 is arranged to be rotatable at high speed by a motor (not shown). By the rotation of the polygon mirror 14, the light beam focused by the condenser lens 13 is sequentially guided to the entrance of each optical waveguide constituting the optical waveguide array 15. The input end 15a of the optical waveguide array 15 is formed in an arc shape surrounding the polygon mirror 14. In addition, the output end 15b
is formed in a straight line parallel to the central axis of the photosensitive drum 20, and is configured to perform circular-linear conversion of the light beam. Similar to known optical waveguides, this optical waveguide is made of two types of materials with different refractive indexes, and has a refractive index n
The cladding 18 (FIG. 2) of No. 1 has a core 17 (
(Fig. 2), and has a relationship of nl<n2. The cladding 18 has a refractive index of 1.4.
The core 17 is made of a fluorine-based resin with a refractive index of 1.49.
Polymethyl methacrylic resin (PMMA) and the like are used.

In the present invention, the output end 15b of the optical waveguide array 15 is provided with a light beam focusing lens 16 for focusing the light beam emitted from the optical waveguide, as shown in the figure. This light beam focusing lens 16 has a refractive index distribution such that the refractive index of the peripheral portion of the core 17 is gradually lower than the refractive index of the portion corresponding to the center of the core 17, and due to this refractive index distribution, It has a focusing effect on the light beam.

Hereinafter, a method for forming such a light beam focusing lens will be explained with reference to FIG.

First, the entire output end 15b of the optical waveguide array 15 is uniformly coated with the photopolymerizable material 19 to a thickness of approximately 50 μm to 100 μm.

This photopolymerizable material 19 is made by incorporating methyl acrylate (refractive index 1.49), which is a photosensitizer, into a fluorine-based resin (refractive index 1.40) as a doping monomer.

Next, ultraviolet light from an ultraviolet light source 21 provided to face the input end 15a of the optical waveguide array 15 is made to uniformly enter the input ports of all the optical waveguides at once. This ultraviolet light is propagated within the optical waveguide and is emitted from the exit. At this time, the optical power density distribution in the plane perpendicular to the optical axis at the exit port exhibits a Gaussian distribution with the center of the core 17 as the apex. As a result, the methyl acrylate undergoes a photopolymerization reaction to be polymerized, and the ratio thereof conforms to the above-mentioned optical power density distribution.

After this photopolymerization reaction using ultraviolet rays is performed, residual monomers that have not been polymerized are removed by vacuum drying. As a result, a refractive index distribution is formed due to the difference in content between the fluorine-based resin of the base material and the polymerized methyl acrylate.

That is, the content of polymerized methyl acrylate is high in the portion corresponding to the center of the core 17, and the content of polymerized methyl acrylate decreases toward the portion corresponding to the periphery of the core 17. do. For this reason,
A light beam converging lens 16 having a light condensing function is formed, in which the refractive index of the portion corresponding to the peripheral portion is lower than that of the central portion of the core 17 .

Next, the operation of such an optical recording device 10 will be explained.

A light source 11 blinks and emits a light beam based on an image signal, and this light beam is guided to a polygon mirror 14 via a collimating lens 12 and a condensing lens 13. Then, as the polygon mirror 14 rotates, the light beam from the light source 11 is sequentially incident on each optical waveguide forming the optical waveguide array 15.

The light beam incident on the optical waveguide array 15 is propagated within the core 17 by being totally reflected at the interface between the core 17 and the cladding 18 due to the relationship between the refractive indexes of the core 17 and the cladding 18 of the optical waveguide array 15.

Then, this light beam is sequentially emitted from the exit of the optical waveguide at an aperture angle determined by the refractive index of the core 17 and the cladding 18. At this time, since the light beam focusing lens 16 is formed at the exit of the optical waveguide, the light beam emitted from the light source 11 based on the image information is directed to the light beam focusing lens 16.
6, the diameter is narrowed and the light is emitted, reaching the photosensitive drum 20. Therefore, even if the distance between the photosensitive drum 20 and the output end 15b of the optical waveguide array 15 is widened, good exposure can be performed without causing crosstalk.

Through the above-described operation, the light beam from the light source 11 that blinks in response to the image signal is scanned at a constant speed in the direction of the central axis of the photosensitive drum 20, and an image is recorded.

Then, each time one line of light scanning is completed, the photosensitive drum 2
0 is intermittently rotated by a drive source (not shown) and image recording is performed by repeating optical line scanning.

Note that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit thereof.

〔Effect of the invention〕

As is clear from the detailed description above, according to the present invention, it is possible to prevent crosstalk of the light beam emitted from the exit port of the optical waveguide on the photoreceptor, and to achieve clear exposure on the photoreceptor. In addition, by increasing the distance between the optical waveguide array and the photoreceptor, it is possible to prevent the emission end of the optical waveguide array from being contaminated by foreign matter.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing an optical scanning device according to the present invention;
FIG. 2 is a cross-sectional view schematically showing an optical waveguide array used in an optical scanning device according to the present invention, and FIG. 3 is a diagram for explaining a method for manufacturing an optical waveguide array used in an optical scanning device according to the present invention. , FIG. 4 is a perspective view schematically showing a conventional optical scanning device. 10... Optical scanning device, 11... Light source, 14... Polygon mirror 15... Optical waveguide array, 15b...
- Output end, 16... light beam focusing lens.

Claims (1)

[Scope of Claims] 1. A light source that emits a light beam based on an image signal, an optical waveguide array formed by arranging a large number of optical waveguides that propagate the light beam from the light source, and an optical waveguide array that propagates the light beam from the light source. An optical scanning device comprising a light beam distributing means for sequentially inputting the light beam into the plurality of optical waveguides, characterized in that a light beam focusing means is provided at the output end of the light beam of the optical waveguide array. . 2. The light beam focusing means is a light beam focusing lens having a refractive index distribution formed by a photopolymerization reaction of a photopolymerizable material applied to the light beam output end of the optical waveguide array. The optical scanning device according to claim 1.