JPS60215552A - Production of plate microlens - Google Patents

Abstract

PURPOSE:To make it possible to mass-produce the titled lens having accuracy required for various uses in a relatively simple step, by subjecting a substrate having a mask even on a surface except a surface having a pattern mask to ionic thermomigration. CONSTITUTION:Plate microlenses are produced by the ionic thermomigration method. In the method, substrates with a pattern mask down have been dipped in a molten salt in the past, but measures for preventing penetration of a dopant into a surface except the surface having the pattern mask, e.g. sides or rear of the substrate, are not taken. The dopant diffuses from the sides, etc. of the substrate, and therefore phenomena, e.g. warpage, torsion, stain, etc. are observed. Thus, a substrate 1 having the mask 7 on surfaces except the surfaces having the pattern mask 2 is used to eliminate the conventional defects, and the aimed plate microlenses 5 of high accuracy can be produced.

Description

Detailed Description of the Invention [Technical Field] The present invention is a method for manufacturing a flat plate microlens using an ion thermal diffusion method. This relates to a method of manufacturing a flat microlens in which a mask is formed on a surface other than the curved surface on which a pattern mask for selective diffusion is formed, and ion thermal diffusion is performed while preventing unnecessary dopants from penetrating into the substrate.

[Prior art]

In recent years, a planar microlens formed by selective diffusion of a dopant into a planar substrate has been reported by Iga et al. and has attracted attention. (Al)1) 1.0pt. 2
2, 441 (1983)) This flat plate microlens has the feature that a large number of microlenses can be monolithically integrated in a desired positional relationship, and by stacking it with other arrayed optical elements, it is possible to form an optical circuit into an array. It is expected that it will become a basic element in future optics-related fields, as it can be manufactured in bulk. Also a copier,
It is thought that it will become a fundamental element in the field of image transmission, such as printer image sensors.

Sarago will also be applied to optical disc pickups, etc. In this way, flat microlenses can be expected to become a fundamental element in many optical-related fields.

However, the conventional manufacturing method for flat plate microlenses uses an ion thermal diffusion process that selectively diffuses dopants into the substrate.
Due to drawbacks such as the substrate being slightly warped or twisted, and the side and back surfaces of the substrate being contaminated with dopants, it was not possible to obtain flat microlenses with the precision required in various fields with good reproducibility. . The ion thermal diffusion process of a conventional flat microlens manufacturing method will be explained with reference to FIG. 1, and various defects in flat microlenses obtained by the conventional manufacturing method will be explained with reference to FIG.

In conventional ion thermal diffusion methods, ion thermal diffusion is performed by immersing the substrate in molten salt with the patterned mask facing down. However, as shown in FIG. 1, no measures are taken to prevent the dopant from penetrating into the substrate on surfaces other than the curved surface where the pattern mask is formed (the side surface of the substrate and the back surface of the substrate in FIG. 1). The dopant diffused from the side surfaces of the substrate, causing phenomena such as warping, twisting, and staining of the substrate. As shown in FIG. 2, these phenomena degrade the precision of flat microlenses and flat microlens arrays. ((α)~Cd)).

(α) Inclination of the optical axis (b) Variation in individual lens characteristics (lens diameter, focal length, NA-, aberration, etc.) (C) Decrease in precision of positional relationship between lenses Cd) Inconsistency in the refractive index of the substrate Uniformity [Purpose] In order to solve the above-mentioned drawbacks, the present invention provides a flat microlens manufacturing method using the ion thermal diffusion method. The purpose was achieved by using ion thermal diffusion.

〔overview〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 6 shows a schematic diagram of the ion thermal diffusion step in the method for manufacturing a flat microlens of the present invention. The substrate used in the present invention has a mask formed on a surface other than the curved surface on which the pattern mask of the substrate used in the conventional ion thermal diffusion method explained in FIG. Infiltrate the substrate only from Therefore, the warpage, twisting, staining, etc. of the substrate, which were disadvantages of the conventional method, are almost completely eliminated, and flat microlenses having the accuracy required as elements of various optical devices can be obtained. Examples of the present invention will be described below.

〔Example〕

A large surface of KF2 glass with a thickness of 1.30 mm x 50 rrrm x 5 ylB was polished.

2. A T1 film of 1 μm each was formed on the large surface of the above substrate using an RF sputtering device.

Two circular openings with a diameter of 500μ are created using a five-photo process.
144 pieces (12 x 12) were provided in a grid pattern with a mm pitch.

4. The substrate was floated on a molten salt consisting of thallium sulfate and zinc sulfate (5:5 molar ratio) with the pattern mask facing down.

(Figure 3) 5. Ion thermal diffusion was performed at 500°C for 96 hours in a N2 atmosphere.

6. The substrate was taken out from the molten salt and slowly cooled.

After cleaning the Z substrate, the Ti film was removed by etching with hot phosphoric acid.

a The glass surface was polished.

Through the above operations, a flat microlens array having the following characteristics was obtained. (Figure 4) ■ Lens diameter 1.5
2mm ■ Focal length A3.12mm (in air) ■ Focal length B 5.0OrrrIn (in glass) ■
Pitch between lenses 2.00 order ■ Number of lenses 144 ■ When parallel light was incident on this flat microlens array G as shown in Figure 5, all 144 flat microlenses showed a good light focusing effect, and the glass substrate G machining 50 on the end face
It was possible to guide light into a fiber.

[Effects] As described above, according to the method for manufacturing flat microlenses of the present invention, flat microlenses with the precision required for various uses can be mass-produced through a relatively simple process, and therefore can become basic optical elements in the future. We are confident that the present invention will have a great impact on the field of optoelectronics, as it will be possible to provide a flat microlens at a low cost. Note that the method for manufacturing a flat microlens of the present invention can be similarly applied to the manufacturing of other microscopic optical devices (for example, thin film waveguides, branching elements, thin film switching elements, etc.) other than flat microlenses.

[Brief explanation of the drawing]

Figure 1 shows a method for manufacturing a flat microlens using the conventional ion thermal diffusion method, in which 1 is a glass substrate, 2 is a pattern mask, 3 is a ceramic container, 4 is a molten salt, 5 is a flat microlens, and 6 is a pattern. This is a region where the dopant is diffused from other than the opening of the mask. FIG. 2 shows examples of various drawbacks of a flat microlens array obtained by a conventional method for manufacturing flat microlenses using the ion thermal diffusion method. (α) is the tilt of the optical axis, (b, ,) is the variation in individual lens characteristics, (C) is the poor precision of the positional relationship between lenses, and (d) is the non-uniformity of the refractive index of the substrate. It's a hailstorm. FIG. 3 schematically shows the method for manufacturing a flat plate microlens according to the present invention, and compared to the conventional method, masks other than pattern mask 7 are newly formed. FIG. 4 (fZ), Cb) and FIG. 5 are diagrams showing the characteristics of the flat microlens and flat microlens array obtained in the examples of the present invention. FIG. 4 is a diagram showing the light condensing characteristics, and FIG. 5 is a diagram showing the coupling characteristics with an optical fiber. 8 is a flat microlens substrate, 9 is a flat microlens, 10 is a condensing spot, 11 is a focal length (A),
In FIG. 5, 12 is a focal length (B), 13 is a flat microlens array substrate, 14 is a flat microlens, and 15 is an optical fiber. Applicant Suwa Seikosha Co., Ltd. Agent Patent Attorney Mogami Figure 1 (C) (Figure 20, Figure 5)

Claims (1)

[Claims] A flat plate microlens manufacturing method using an ion thermal diffusion method, characterized in that ion thermal diffusion is performed using a substrate on which a mask is formed on a surface other than the curved surface on which a pattern mask is formed. How to manufacture lenses.