JPH03171010A - Production of plane optical waveguide lens - Google Patents

Abstract

PURPOSE:To relatively easily obtain the high-quality plane optical waveguide which has no discontinuous surface by approximately one-dimensionally distributing the transmittance of a photomask to adjust the exposure to a photosensitive material and approximately quadratic-functionally forming an intra-surface refractive index distribution in one direction within the plane. CONSTITUTION:The photomask 12 consists of a high transmittance region and low transmittance region, the transmittance of which attains only the two kinds of the values in the microregions divided to a prescribed size. The photomask is so formed that the transmittance has the one-dimensional distribution as a whole by adjusting the area ratio of these two regions. Namely, the exposure to the photosensitive material is adjusted by approximately one-dimensionally distributing the transmittance of the photomask 12, by which the intra-surface refractive index distribution is formed approximately quadratic-functionally in the one direction within the plane. The lens which has no discontinuous boundary surfaces and decreases the scattering loss of propagated light is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a planar optical waveguide lens.

[Conventional technology]

Conventionally, the manufacturing method of a planar optical waveguide lens includes (i) a manufacturing method in which a plurality of lens-shaped regions are discontinuously formed on the sheet surface by making the peripheral region of the sheet surface a high refractive index region, etc.; and (ii) a manufacturing method in which a continuous refractive index distribution is formed on the sheet surface to realize a lens effect. As a specific example of the latter manufacturing method, a method that utilizes thermal diffusion of impurities is common.

[Problem to be solved by the invention]

However, since all of the above-mentioned methods include an etching process for microfabrication and a thermal diffusion process, they require expensive manufacturing equipment and are difficult to reduce in price. Furthermore, in the method of forming lenticular regions, it is necessary to form discontinuous surfaces between regions with extremely high precision in order to prevent scattering of light.

The present invention has been made in order to solve the above-mentioned problems, and provides a method for manufacturing a planar optical waveguide lens that allows a high-quality planar waveguide lens without discontinuous surfaces to be obtained by a relatively easy method. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the present invention provides a method for manufacturing a planar optical waveguide lens that obtains an in-plane refractive index distribution by exposing the surface of a sheet containing a photosensitive material to a photomask, the method comprising: The present invention is configured to include a step of forming the in-plane refractive index distribution in a substantially quadratic manner with respect to one direction within the plane by adjusting the amount of exposure to the photosensitive material.

Further, in the present invention, the photomask has a high transmittance region and a low transmittance region in which the transmittance takes only two values in minute regions divided into predetermined sizes, and the area of the two regions is By adjusting the ratio, the transmittance was configured to have a one-dimensional distribution as a whole.

Further, in the present invention, the photosensitive material is a photopolymerizable monomer, and the method is configured to include a step of volatilizing and removing unreacted monomers after exposure with a photomask.

[Effect]

In the method for manufacturing a planar optical waveguide lens of the present invention having the above configuration, the intensity of the light transmitted through the photomask is weak (or strong) near the center line of the photosensitive material-containing sheet, and gradually increases (gradually decreases) toward the periphery. Forms a one-dimensional distribution. As a result, the reaction of the photosensitive material also has a distribution similar to the exposure intensity distribution. Finally, a desired in-plane refractive index distribution having a substantially quadratic pattern in one direction of the inner surface is obtained, and a lens effect can be realized.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 3 is an explanatory diagram chronologically showing the method for manufacturing a planar optical waveguide lens according to the present invention, which consists of the following four processes.

(a) Production of base film: A photosensitive material is contained in a base material (for example, polycarbonate, etc.), and a sheet of a predetermined thickness is formed by a melt extrusion method (also called casting) or the like. The photosensitive material is preferably a photopolymerizable monomer, such as methyl acrylate. As a preferred example, methyl acrylate with a refractive index of n2 = 1.48 is incorporated as a doping monomer into polycarbonate with a refractive index of nl = 1.59, and a thickness of 50 to 100 mm is formed by melt extrusion (also called casting).
A sheet 11 of μm is formed.

(b) Photopolymerization by mask exposure; Photomask 12
is placed on the sheet and exposed to ultraviolet light. The photomask 12 has a pattern with a substantially one-dimensional distribution in which the transmittance is small at the center and gradually increases toward the periphery, for example. To form such a transmittance distribution pattern,
For example, the method shown below may be adopted. That is, the photomask 12 is divided into minute areas of a predetermined size, and these divided minute areas are divided into a high transmittance area and a low transmittance area where the transmittance takes only one of two values. By adjusting the area ratio of these two regions, it is possible to obtain a photomask 12 having a continuous transmittance with a one-dimensional distribution as a whole.

As a result, the methyl acrylate monomer in each part is irradiated with ultraviolet light whose exposure amount is adjusted according to the photomask 12 having the transmittance of the photomask 12,
Causes a photopolymerization reaction.

(c) Removal of unreacted monomers: When unreacted monomers are removed by vacuum drying, the remaining amount of photopolymerized polymer is smaller in the center and larger in the periphery, resulting in a nearly quadratic shape in one direction within the plane. A core 2 having a desired in-plane refractive index distribution with a pattern that changes functionally is obtained.

(d) Surface cladding: A low refractive index acrylic resin is coated as the cladding layer 3 in the vertical direction of the sheet.

Next, the operation of the planar optical waveguide lens 1 manufactured by the above manufacturing method will be explained with reference to FIGS. 1 and 2.

In FIG. 1, the wedge-shaped input light 4 is focused on one end surface of the core 2. As shown in FIG. That is, the input light 4 is y in the figure.
In terms of direction, the light is approximately parallel.

The refractive index distribution in the X direction is as shown in FIG. 2(a), and light is retained in the core 2, which is a high refractive index portion. On the other hand, as shown in FIG. 2(b), the refractive index distribution in the y direction is approximately quadratic, for example n refractive index difference, Y: y-direction waveguide width.

Since the input light has a relatively small refractive index in the peripheral portion in the y direction, the phase velocity increases and it gradually converges. If the planar waveguide lens 1 is cut at a length that minimizes the width of the light, the output light 5 will have a cone-shaped beam shape, as shown in FIG.

The planar optical waveguide lens 1 of the present invention is applied, for example, to an optical transmission system between a deflector and a photosensitive drum for a laser printer, as shown in FIG.

In other words, the optical transmission system includes a rotating mirror 2 on the tip inclined surface.
1a, a planar optical waveguide lens 1 of the present invention, and a photosensitive drum 22.

Then, the incident laser beam 41 directed toward the rotating mirror 21a is reflected by the rotating mirror 21a, passes through the planar optical waveguide lens 1 as a scanning light beam 42, and finally becomes a cone-shaped beam 51 and exits. ,
A recording spot is formed on the photosensitive drum 22.

Such an optical transmission system is excellent in that its configuration and structure are simple, low cost, and can be made smaller and lighter. Furthermore, it can be used in place of conventional expensive f/theta lenses without special consideration.

〔Effect of the invention〕

As is clear from the detailed description above, according to the present invention, it is possible to relatively easily manufacture a high-performance planar optical waveguide lens that has no discontinuous boundary surfaces and has little scattering loss of propagating light. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of the planar optical waveguide lens obtained by the manufacturing method of the present invention, and FIGS. 2(a) and (b) show the refractive index of the planar optical waveguide lens in the X direction and the y direction, respectively. It is a diagram showing the distribution shape, and FIGS. 3(a) to 3(d)
) is an explanatory diagram showing the manufacturing process of the planar optical waveguide lens according to the present invention, and FIG. 4(a). (b) is a plan view and a front view, respectively, showing a specific example of an optical transmission system to which the planar optical waveguide lens of the present invention is applied. DESCRIPTION OF SYMBOLS 1... Planar waveguide lens, 2... Core, 3... Clad layer, 11... Photosensitive material containing sheet, ■2...
・Photomask.

Claims (1)

[Claims] 1. A method for manufacturing a planar optical waveguide lens that obtains an in-plane refractive index distribution by exposing the surface of a sheet containing a photosensitive material to a photomask, wherein the transmittance of the photomask has a substantially one-dimensional distribution. The method further comprises a step of forming the in-plane refractive index distribution in a substantially quadratic manner with respect to one direction within the plane by adjusting the amount of exposure to the photosensitive material. A method for manufacturing a planar optical waveguide lens. 2. The photomask consists of a high transmittance region and a low transmittance region in which the transmittance takes only two values in minute regions divided into predetermined sizes, and the area ratio of the two regions is adjusted. 2. The method of manufacturing a planar optical waveguide lens according to claim 1, wherein the transmittance as a whole is made to have a substantially one-dimensional distribution. 3. The method for manufacturing a planar optical waveguide lens according to claim 1 or 2, wherein the photosensitive material is a photopolymerizable monomer, and the method includes a step of volatilizing and removing unreacted monomers after photomask exposure. .