JPH03144503A - Optical waveguide for optical scanner - Google Patents

Abstract

PURPOSE:To prevent picture quality from deteriorating owing to crosstalk by providing lenses which converge projection light at the light projection ends of optical waveguides and preventing the projection light from causing crosstalk on a photosensitive drum. CONSTITUTION:The optical waveguides 12 and 13 of the optical scanning device which transmits light from a light source 1 are provided with the lenses 16 and 14 which converge the projection light at their light projection ends. A lens 14 which converges the projection light from the light projection end of the 2nd optical waveguide 13 is provided at the light projection end so that its vertex is on the center line of the core part 13a of the optical waveguide 13. The light from the light source 1 passes through the optical waveguides 12 and 13 and is projected from their light projection ends, but the light is converged by the lenses 16 and 14 at such a time. Consequently, crosstalk is prevented from being caused on the photosensitive drum 6 and the interval between the light projection ends of the optical waveguides and the photosensitive drum 6 is increased to make foreign matter hard to stick on an optical fiber tip.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to improvements in optical waveguides for optical scanning devices.

[Conventional technology]

2. Description of the Related Art Conventionally, an optical scanning device having a configuration as shown in FIG. 7 has been proposed, which uses, for example, an optical fiber as an optical waveguide to perform optical scanning and write signals on a photosensitive recording medium.

This optical scanning device has a point light source made of a semiconductor laser or a light emitting diode driven by an image signal, and a scanner 2 receives light from the point light source.

The scanner 2 has a disc-shaped rotating body 4 rotated by a motor 3, and a first member that receives light from the light source 1 in the rotating body 4 and emits the light in a radial direction of the rotating body 4.
It has an optical waveguide 5 of.

The optical scanning device also includes a second optical waveguide 7 made of an optical fiber array that receives light emitted from the first optical waveguide 5 of the scanner 2 and conveys it to the photosensitive drum 6. The light input end 8 of the optical waveguide 7 is arranged in an arc shape so as to surround the rotating body 4 of the scanner 2, and the light output end 9 is arranged in the generatrix direction of the photosensitive drum 6.

As a result, when the motor 3 rotates at a constant speed and the light source 1 emits light, the light is sent from the first optical waveguide 5 of the scanner 2 to each optical fiber of the second optical waveguide 7. The light entering each optical fiber from the input end 8 propagates through the fiber and heads to the output end 9, and from there the light is output toward the photosensitive drum 6 for exposure.

In addition, in FIG. 7, reference numeral 10 indicates a collimating lens that receives the light from the light source 1, and reference numeral 1 indicates a condenser lens that receives the light from the collimating lens 10, narrows it down, and guides it to the input end of the first optical waveguide 7. It shows.

[Problem to be solved by the invention]

However, the conventional optical scanning device described above has the following problems.

The numerical aperture NA at the light output end 9 of the second optical waveguide 7 is given by the following equation.

NA−=n, tin r=IXsin (r,)l
naI) However, the signs of this equation are as shown in FIG.

PMMA is a typical material for resin-based optical fibers.
(refractive index n 1 = 1.49) as the core and fluororesin (refractive index n 2 = 1.40) as the cladding, from equation (1), NA = 0.5 and angle r = 30.
degree.

Therefore, the diameter of the light beam emitted from the tip of the optical fiber reliably increases as it moves away from the end face of the optical fiber. In order to prevent such excessive spreading of the light beam, the diameter of the optical fiber of the second leading wavepath 7 is set to 8.
The gap between the optical fiber and the photosensitive drum 6 needs to be about 5 μm, but in this case, unless the gap between the optical fiber and the photosensitive drum 6 is 50 μm or less, the image written on the photosensitive drum 6 will be caused by adjacent pixels interfering with each other. This results in crosstalk, which causes deterioration in image quality.

However, such a small gap causes a problem in that foreign matter such as toner and paper powder that cannot be removed in the cleaning process adheres to the output end 9 of the optical fiber array, which adversely affects the image.

In addition, even if the gap is large to some extent, the diameter of the optical fiber may be set to 50 mm, for example, in order to reduce the loss of stalk.
Although it is conceivable to make the optical fiber smaller than μm, making the optical fiber thinner in this way reduces the mechanical strength of the optical fiber, which becomes an obstacle when manufacturing an optical fiber array.

Therefore, an object of the present invention is to prevent the light beams emitted from the individual optical fibers of the optical fiber array from causing crosstalk on the photosensitive drum without making the optical fibers thinner, and to prevent the deterioration of image quality due to crosstalk. shall be.

Another purpose is to provide a large gap between the optical fiber array and the photosensitive drum to prevent the tip of the optical fiber array from being contaminated by foreign matter.

[Means to solve the problem]

In order to solve the above-mentioned problems and achieve the objects of the present invention, the present invention provides an optical waveguide of an optical scanning device that conveys light from a light source, and a lens that focuses the emitted light at the light output end of the guide waveguide. The established configuration is adopted.

Note that the lens may be formed integrally with the guide waveguide at the light output end of the guide waveguide, or may be separate from the optical waveguide.

[Effect]

Light from a light source passes through an optical waveguide and exits from its light output end, where it is focused by a lens.

This prevents crosstalk from occurring on the photosensitive drum. Furthermore, by increasing the distance between the light emitting end of the leading waveguide and the photosensitive drum, it is possible to make it more difficult for foreign matter to adhere to the tip of the optical fiber.

〔Example〕

Hereinafter, embodiments of the leading waveguide of the optical scanning device according to the present invention will be described.

Embodiment 1 This optical scanning device, as shown in FIGS. 1 and 2, includes a point light source 1, a scanner 2, a photosensitive drum 6, etc., similar to those shown in FIG. 7 described above.

However, the first guide waveguide 12 and the second optical waveguide 13 have different configurations from those described above, and the second optical waveguide 12
A lens 14 for converging the light emitted therefrom is provided at the light emitting end of the optical waveguide 13 so that its apex is on the center line of the core portion 13a of the optical waveguide 13.

This lens 14 may be a hemispherical lens,
It may also be an aspherical lens. However, when the core diameter is several tens of μm, the light beam propagating within the optical waveguide 13 becomes a multimode light beam, and is propagated to the output end face at various angles. Therefore, it is difficult to focus these light beams to a relatively small diameter with a spherical lens of single curvature.

Therefore, the shape of the lens 14 depends on the diameter of the leading waveguide 13, the distance from the end of the lens 14 to the photosensitive drum 6, the lens 14,
It is preferable to use an aspherical lens in which spherical aberration is corrected by using each refractive index of the optical waveguide 13 as a parameter.

Further, in the illustrated example, the lens 14 is integrally molded at the same time as the optical waveguide 13, but it may be molded separately and then bonded to the end of the core portion 13a.

In order to prevent crosstalk from occurring when the light beam enters the light input end 15 of the second optical waveguide 13, the
A lens 16 for focusing light is also provided at the light output end of the leading waveguide 12 . This lens 16 is provided as necessary. Further, this lens 16 also has the above-mentioned lens 1.
4, it may be formed integrally with the leading waveguide 12,
It may also be formed as a separate body and bonded to the rear exit end.

Here, a method of integrally forming the lens element 4 with the main body of the second optical waveguide 13 will be explained.

First, as shown in FIG. 3 (1), a polymeric material with good moldability such as polycarbonate or PMMA is placed in two molds 17.
．． The base material 19 of the optical waveguide 13 is formed by sandwiching the optical waveguide 18 between the two. As a result, a large number of grooves 19a are formed in parallel on the upper surface of the base material 19.

Next, as shown in FIG. 3(2), on the upper surface of the base material 19,
A fluororesin diluted with a solvent and having a refractive index of about 1.4 is applied and dried to form the Clarado portion 13b.

Thereafter, as shown in FIG. 3 (3) and FIG. 4, a mold 20 having a cavity for molding the lens 14 is applied to the base material 9, and a A methacrylic resin monomer is poured into the grooves 19a in which the cladding portion 13b is formed, and a polymerization reaction is caused by exposure to ultraviolet light to form the core portion 13a.

Thereafter, as shown in FIG. 3(4), the fluorine-based resin is applied to the exposed surface of the cladding part 13b and the core part 13a in alternating stripes to complete the cladding part 13b.

In the optical waveguide 13 thus obtained, the base material 19 may be thin enough to form the core portion 13a, and may have a thickness of about 0.1 to 1.0 ribs. can. Therefore, the optical waveguide 13 can also be used by being bent in a direction perpendicular to the optical path.

Note that the first optical waveguide 12 can also be manufactured using the manufacturing method described above.

Next, the operation of the optical scanning device will be explained.

The point light source 1 is blinked based on an image signal by a drive circuit (not shown). Light incidence end 21 of first guide wavepath 12
is on the rotation axis of the rotating body 4, so the light from the light source 1 is always incident on the first optical waveguide 12. In addition, the light source light is passed through the condensing lens 0 to the incident end 21 of the first leading waveguide 12.
The beam diameter is controlled to be the minimum. Therefore, even if there is some deviation in the positional relationship between the light source 1 and the first optical waveguide 12, the light will not deviate from the input end 21 of the first optical waveguide 12.

In the first guiding waveguide 12, light is substantially totally reflected at the interface between the core portion 12a and the cladding portion 12b and propagates within the core portion 2a due to the relationship between the refractive indexes of the core portion 12a and the cladding portion 12b. Then, at the terminal end of the optical waveguide 12, the lens 16 narrows down the beam to a diameter smaller than the diameter of the input end 15 of the second optical waveguide 13.

The light source 1 includes a lens 1 at the output end of the first optical waveguide 12.
6 faces each opposing end 15 of the array of second optical waveguides 13, so that the optical signal of each pixel from the light source 1 sequentially enters each of the arrays of second optical waveguides 3. .

In the second optical waveguide 13, as in the first optical waveguide 12, the light beam propagates through the core parts 1 and 3a while being totally reflected due to the difference in refractive index between the core part 13a and the cladding part 13b. I'll do it. Then, at the output end, the lens 1-4
The light is focused and hits the surface of the photosensitive drum 6 without causing crosstalk.

Embodiment 2 In this case, the point light source 1 is provided on the circumferential surface of a rotating body 4 rotated by a motor 3. A lens element 6 is installed near the point light source and rotates together with the rotating body 4.

As a result, the light from the point light source 1 that blinks based on the image signal is focused by the lens 16 and enters the optical waveguide 13 from its entrance end 15 . This incident light is then passed through the optical waveguide 13.
The light passes through the inside and is focused by the lens 14 at the end and exits.
The first side of the photosensitive drum 6 will be exposed.

〔Effect of the invention〕

Since the present invention has the above-described configuration, the light emitted from the output end of the optical waveguide can be focused upon output. Therefore, it is possible to suitably prevent the emitted light from causing crosstalk. Also,
By making the distance between the output end of the leading waveguide and the photosensitive drum as large as possible, it is possible to make it more difficult for foreign matter such as toner to adhere to the tip of the optical fiber. Therefore, together with the prevention of the crosstalk, it is possible to suitably prevent deterioration of image quality.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view showing an embodiment of the optical scanning device according to the present invention, FIG. 2 is a cross-sectional view taken along the line ■■ in FIG. Figure 3 (1)
3(2) is a sectional view showing the forming process of the base material, FIG. 3(2) is a sectional view showing the forming process of the clad part, FIG. 3(3) is a sectional view showing the forming process of the core part, FIG. 4) is a sectional view showing the final process, FIG. 4 is a sectional view taken along the rV-IV line in FIG. 3 (3), FIG. 5 is a sectional view similar to FIG. 1 showing another embodiment, and FIG. 7 is an explanatory diagram showing the state of propagation of light within an optical waveguide, and FIG. 7 is a perspective view of a conventional optical scanning device. 1...Point light source, 2...Scanner, 3...Motor,
4... Rotating body, 6... Photosensitive drum, 12... First
Leading wavepath, 13...Second leading waveway, 1,3a...
・Core part, 13b...Clad part, ↓4...Lens, 15...Light incidence end, 16...Lens, 19...
Base material, 20...lens mold.

Claims (1)

[Claims] 1. An optical scanning device characterized in that an optical waveguide of an optical scanning device that conveys light from a light source is provided with a lens that focuses the emitted light at a light output end of the optical waveguide. optical waveguide. 2. The optical waveguide for an optical scanning device according to claim 1, wherein the lens is formed integrally with the optical waveguide at the light output end of the optical waveguide.