JPH04175228A - Production of optics - Google Patents

Abstract

PURPOSE:To enable production of the subject thin and high-accuracy optics without changing the degree of parallelization of a thin transparent base plate or the thickness thereof by press molding the thin transparent base plate using a pair of mold units while making the temperature of one mold unit for forming fine optics higher than that of the other mold unit. CONSTITUTION:A thin transparent base plate 3 is placed on one press molding mold unit 1 for forming fine optics and a pair of press molding mold units 1 and 2 are heated to a prescribed temperatures. In this case, the temperature of the one mold unit 1 is made >=10 deg.C higher than that of the other mold unit 2 so that the temperature of the transparent base plate 3 may be a temperature where the base plate shows 10<6>-10<10> poise. A press cylinder 7 is lowered to press mold the transparent base plate 3 and the objective optics 10 are obtained. This method enables heat deformation of only a plane forming a microlens array, a diffraction grating, etc., and the objective thin and high-accuracy optics can be produced without changing the degree of parallelization of the original transparent base plate 3 and the thickness thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing thin and highly accurate optical elements such as microlens arrays and diffraction gratings.

BACKGROUND OF THE INVENTION In recent years, there has been a strong desire to develop thin, high-precision optical elements such as microlens arrays and diffraction gratings in order to make new optical devices smaller and lighter. Conventionally, in manufacturing such high-precision optical elements, Japanese Patent Application Laid-Open No. 60-2
As described in Japanese Patent No. 64334, this was done by photolithography using a photoresist.

Problems to be Solved by the Invention With conventional photolithography using photoresists, it is difficult to mass produce as it involves a number of complicated processes such as patterning and etching, and it is difficult to control the shape of optical elements with high precision. I couldn't do it.

Means for Solving the Problems In order to solve the above problems, the present invention provides a pair of press molding molds in which the temperature of one mold for forming a micro-optical element is lower than the temperature of the other mold (both are 10°C). The present invention provides a method for manufacturing an optical element in which a thin transparent substrate is heated and press-molded at a high temperature.

The molding method using a working mold is a method in which a lump of material to be molded is heated and molded using a mold that has been finished in a desired shape and surface quality in advance, and has a diameter of, for example, 10 m.

In the case of a so-called normal lens with a thickness of about 5 W, the molding was carried out under heating and pressure with a pair of molds kept at the same temperature. However, in the case of thin optical elements such as microlens arrays and diffraction gratings, when a pair of molds are heated and pressed at the same temperature, not only the surface of the transparent substrate where the microlens array or diffraction grating will be formed, but also the other side. The surfaces of the optical elements are also thermally deformed, making it difficult to maintain the parallelism of the optical element, and making the optical element thinner makes it more likely to break.

In the present invention, in a pair of press molding molds, a thin transparent substrate is heated and press-molded at a temperature where one mold for forming a micro-optical element is at least 10°C higher than the other mold temperature. , it is possible to thermally deform only the surface forming the microlens array, diffraction grating, etc., and it is possible to manufacture a thin and highly accurate optical element without changing the parallelism or thickness of the original transparent substrate.

Examples Example 1 Cemented carbide (WC-5T) was used as the base material of the press mold 1.
iC-8Co) was cut into 505w*40m5+*10w1 square plates, and then wrapped with ultra-fine diamond powder to improve the surface roughness (RMS) in about 1 hour.
It has a mirror surface of about 30A. This mirror surface was coated with a thin film of platinum-iridium-osmium alloy (Pt-1r-Os) by sputtering.

A concave lenticular lens with a sag amount of 1.5 μm was formed on the above thin film at a pitch of 50 μm using a cutting machine in which a diamond cutting tool with a radius of curvature of 200 μm was numerically controlled with high precision to form a press molding mold 1. In a similar manner, a cemented carbide (WC-57i) was used as the base material of the press mold 2.
C-8Co) was cut into a 50m*40mm*10mm square flat plate, which was further lapped with ultrafine diamond powder to give a mirror surface with a surface roughness (RMS) of about 30A. This mirror surface was coated with a thin film of platinum-iridium-osmium alloy (Pt-Ir-Os) by sputtering to obtain a press molding mold 2.

FIG. 1 is a cross-sectional view schematically showing the method for manufacturing an optical element of the present invention. As the transparent substrate 3, silica (SiO2
), 50 weight percent of barium oxide (Bad), 15 weight percent of boric acid (B 20 s ), and the balance was a barium borosilicate glass consisting of trace components. The press molding die 1 was attached to the lower heater block 4, the press molding die 2 was attached to the upper heater block 5, and further attached to the press cylinders 6 and 7. As shown in FIG. 1 (a), a transparent substrate 3 was placed on a press molding die 1, and the press molding die 1 and press molding die 2 were heated to a predetermined temperature. Figure 1 (
As shown in b), the press cylinder 7 was lowered and the transparent substrate 3 was press-molded. As shown in Table 1, the press molding conditions were as follows: the glass had a viscosity of 106 to 1010 poise, the gold was 118 degrees Celsius, and the press pressure was 3 kHz/d. Then 300℃
The optical element 10 as shown in FIG. 1(C) was obtained. The series of press forming was performed using 20 liters of nitrogen gas.
This was carried out using a molding machine (not shown) maintained in a non-oxidizing atmosphere in which hydrogen gas was mixed at a rate of 2 liters per minute and 2 liters of hydrogen gas per minute.

Through these steps, the optical element 10 was manufactured under various conditions shown in Table 1. As is clear from Table 1, no defects such as cracks or bubbles were observed in any of the optical elements 10, the parallelism of the transparent substrate 3 was maintained, and the surface accuracy was within 2 Newton rings, 5 min. The optical performance was extremely excellent.

(Margins below) Example 2 Silicone was used as the base material of press mold 1 50-*4
After cutting into a flat plate with a 0*10-angle, it was further lapped with ultra-fine diamond powder to give a mirror surface with a surface roughness (RMS) of about 20A in about 1 hour. A rhodium-gold-tungsten alloy (Rh) was applied to this mirror surface by sputtering.
-Au-W) was coated with a thin film. The radius of curvature is 0.
A concave diffraction grating with a sag of 0.5 μm is cut into a 3μ
The above thin film was formed at a pitch of m to form a press molding mold 1. Using the same method, silicon was cut into 50wa*40wn*10m+square flat plates as the base material for the press mold 2, and then wrapped with ultra-fine diamond powder to achieve a surface roughness (RMS) of approximately 20A. I made it a mirror surface. This mirror surface was coated with a thin film of rhodium-gold-tungsten alloy (Rh-Au-W) by sputtering to form a press molding mold 2.

As the transparent substrate 3, 52% by weight of silica (Si02), 6% by weight of potassium oxide (K20), 35% by weight of lead oxide (PbO), and 35% by weight of sodium oxide (
A heavy flint glass containing 5% by weight of Na20) and the remainder consisting of trace components was used.

The press mold 1 was attached to the lower heater block 4, and the press mold 2 was attached to the upper heater block 5, and then to the press cylinders 6 and 7. As shown in FIG. 1(a), a transparent substrate 3 was placed on a press molding die 1, and the press molding die 1 and the press molding die 2 were heated to a predetermined temperature. As shown in FIG. 1(b), the press cylinder 7 was lowered and the transparent substrate 3 was press-molded. As shown in Table 1, the press forming conditions are as follows:
The mold temperature was such that the viscosity was 1010 poise, and the pressing time was 1 minute. Thereafter, it was slowly cooled to 200° C. to obtain an optical element 10 as shown in FIG. 1(C). The series of press moldings was carried out using a molding machine (not shown) maintained in a non-oxidizing atmosphere containing 20 liters/minute of helium gas and 2 liters/minute of carbon dioxide gas.

Through such steps, optical elements 10 were manufactured under various conditions shown in Table 2. As is clear from Table 2, no defects such as cracks or bubbles were observed in any of the optical elements 10, the parallelism of the transparent substrate 3 was maintained, and the surface accuracy was within 2 Newton rings and 5 min. The optical performance was extremely excellent.

(Left below) In addition, in the method for manufacturing an optical element of the present invention, in a pair of press molding molds, the temperature of one mold for forming a micro optical element is lower than the temperature of the other mold (both are 10°C or higher). It is characterized by heating and pressure molding a thin transparent substrate at high temperatures, and the thickness of the transparent substrate, the type of substrate material (glass or plastic), the mold material for press molding, and the temperature of heating and pressure molding. Conditions such as time, atmosphere, and the shape of the optical element are not limited to those in this example.

As described in detail, the method for manufacturing an optical element of the present invention is characterized in that in a pair of press-molding molds, the temperature of one of the molds for forming the microscopic optical cord is at least 10% lower than the temperature of the other mold.
By heating and press-molding a thin transparent substrate at a temperature higher than ℃, it is possible to thermally deform only the surface that forms the microlens array, diffraction grating, etc., changing the parallelism and thickness of the original transparent substrate. It is possible to manufacture thin, high-precision optical elements without any problems. That is, the present invention makes it possible to mass-produce highly accurate optical elements, and has a significant effect on improving productivity and reducing manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the method for manufacturing an optical element of the present invention. 1.2...Mold for press molding, 3...
Transparent substrate, 4, 5... Heater block, 6, 7
...Press cylinder, lO...Optical element.

Claims (2)

[Claims] (1) In a pair of press molding molds, the temperature of one of the molds forming the micro-optical element is at least 10°C higher than the temperature of the other mold, and a thin transparent substrate is heated and press-molded. Production method. (2) The method for manufacturing an optical element according to claim 1, wherein one of the molds for forming the micro optical element has a temperature at which the transparent substrate exhibits a viscosity of 10^6 to 10^1^0 poise.