JPH04164828A - Method for forming optical element - Google Patents

Abstract

PURPOSE:To prevent the swell of an interface by pressing a single fiber glass material under restriction with a circumference-restriction member while forming a space for holding excess glass material. CONSTITUTION:A single fiber glass material 1 composed of a core 2 and a clad 3 surrounding the circumference of the core 2 and having flat faces on both ends is inserted into a circumference-restriction member 5 and softened with heat. Both ends of the single fiber glass material 1 are pressed with a forming mold 6 having a desired forming face 6a and a forming mold 7 having a space 7a with a volume corresponding to or larger than the volume of the forming face 6a. The end part of the side of the forming mold 7 is removed from the formed glass material 1 to obtain the objective optical element 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for molding an optical element, in which a glass material is softened by heating and then press-molded using a mold.

[Conventional technology]

Recently, as a method for manufacturing glass optical elements such as lenses and prisms, a molding method has been developed and implemented in which a glass material is softened by heating and then press-molded using a mold. Such a molding method is attracting attention as a molding method that can mass-produce aspherical optical elements, which were conventionally expensive, at low cost. As inventions of this molding method, the following inventions have been disclosed.

For example, in the invention described in JP-A No. 62-96329, the step of press forming at a forming speed set according to the viscosity of the glass material is divided into two steps: preforming and main forming. Molding methods have been proposed.

Furthermore, in the invention described in JP-A-59-141435, the upper mold for molding the functional surface of the optical element is configured to be pressed against the upper edge of the lower mold for molding the other functional surface of the optical element. A device has been proposed.

[Problem to be solved by the invention]

In recent years, the use of optical element molding technology by pressure molding has been expanding more and more, and in terms of the glass materials to be molded, it is now being applied not only to optical elements made of a single glass material, but also to optical elements made of different types of glass materials. Its range of applications is expanding.

A specific example is the application to a single fiber optical element as shown in FIGS. 6a and 6b. FIG. 6a shows a single fiber 91 before molding, and FIG. 6 shows a single fiber 93 after molding in which a curved surface 92 has been created. The single fiber 91 is composed of a core 94 and a crut 95.
Both form an interface 96. The glass material used for the core 94 and the cladding 95 is selected from a material that has a refractive index as large as possible.
A glass material used for this purpose is selected to have a refractive index as small as possible than that of the core 94, and the structure is such that the difference in refractive index between the two becomes large.

As a result, the light incident on one end face of the single fiber 91 is reflected at the interface 96 with almost no loss, and then exits from the other end face. The end face of this single fiber 91 is press-molded to create a curved surface 92, and the single fiber 93 after molding is either one that has the power of a lens.

The single fiber 93 lens described above has an extremely large effect in, for example, an illumination optical system that covers a wide angle range with a small number of lenses. single fiber 9
3 interface 96 must be in a proper state. That is, it is necessary to prevent the interface 96 from undulating in shape during molding.

However, the prior art has the following drawbacks.

Regarding the invention described in JP-A-62-96329,
In the specification, the outer circumferential portion of the glass material is deformed significantly, as shown in the description that a curved surface is formed on the outer circumferential portion of the glass material, so that the interface 96 is not in an appropriate state.

Furthermore, although it is possible to eliminate the eccentricity of the optical element in the invention described in JP-A-59-141435, in order to obtain the desired wall thickness, the glass material is Let the remainder flow in. Therefore, there is a drawback that the interface 96 is not in a proper state.

Therefore, the present invention was developed in view of the above drawbacks.
The purpose of the present invention is to provide a method for molding an optical element in which a single fiber consisting of a core and a crat is made of glass and compression molding can be performed while maintaining the interface of the single fiber in an appropriate state.

[Means and effects for solving the problem] The present invention provides a method for molding an optical element in which molding is performed by pressing molds on both ends of a single fiber glass material consisting of a flat surface at both ends. While inserting it into the outer periphery regulating member and heating it, form a shape corresponding to the desired optical element functional surface in one of the molds, and form a volume corresponding to the same or more of the shape in the other mold. This is a molding method in which the glass surface pressed by the other mold is removed after press molding.

FIGS. 1a, b, and C are conceptual diagrams showing the molding of a plano-concave lens by the optical element molding method according to the present invention. FIG. 1a is a longitudinal cross-sectional view showing the state before molding, and FIG. FIG. 1C is a cross-sectional view of the molded optical element.

1 is a single fiber glass material, and this single fiber glass material 1 is composed of a core 2 and a clad 3 surrounding the outer periphery of the core 2, and an interface 4 is formed at the boundary between the core 2 and the clad 3. In order to form a molding surface (recess) la having a desired functional surface on one end surface of the single fiber glass material 1, the single fiber glass material 1 is inserted into the outer periphery regulating member 5 and heated and softened.

Next, a mold 6 having a molding surface (convex portion) 6a formed in a shape corresponding to the desired aspherical shape, and a volume portion (concave portion) having a corresponding volume equal to or greater than the volume of the molding surface 6a.
Both end surfaces of the single fiber glass material 1 are pressed and molded using a mold 7 having a shape 7a formed therein. After molding, the molded single fiber (optical element) 8 is obtained by removing the end of the single fiber glass material 1 on the mold 7 side.

The present invention provides a volume portion 7 for accommodating an excess amount of the single fiber glass material 1 in the mold 7 when the outer periphery of the single fiber glass material 1 is restricted by the outer periphery regulating member 5 and then press-molded.
By forming a, it is possible to prevent the interface 4 from undulating in shape, and it is possible to maintain the interface 4 in an appropriate state.

Incidentally, in the above explanation, a plano-concave lens was explained, but in the case of molding a plano-convex lens, a molding surface (concavity) corresponding to the molding surface of the plano-convex lens is formed in the mold 6, and By forming a volume portion (convex portion) having a volume equal to or greater than the volume of the molding surface, molding similar to that of the plano-concave lens described above can be performed.

〔Example〕

Hereinafter, embodiments of the method for molding an optical element according to the present invention will be described in detail with reference to the drawings.

(First Embodiment) Figures 2a, b and C show a first embodiment of the present invention,
FIG. 2a is a longitudinal sectional view, FIG. 2 is a longitudinal sectional view during molding, and FIG. 2C is a sectional view of the molded optical element.

1) is a bottomed cylindrical outer circumferential regulating member made of cemented carbide with a coefficient of linear expansion of 6 A through hole 13 is bored in the center. A heater 14 is wound around the outer circumferential surface of the outer circumferential regulating member 1), and an air hole 15 is bored in the upper portion of the outer circumferential surface and penetrates through the upper inner circumferential surface.

A lower mold 16 made of a material with good air permeability such as porous ceramic is slidably fitted into the outer periphery regulating member 1), and the lower mold 16 is fitted to the stepped portion 12 of the outer periphery regulating member 1). It is locked by. Furthermore, an upper mold 17 that is vertically movable is fitted into the outer periphery regulating member 1). The upper mold 17 is formed with an aspherical convex molding surface 17a corresponding to the desired functional surface of the optical element. A concave portion 16a having a volume equal to or greater than the volume of the convex molding surface 17a of the upper mold 17 is formed on the upper surface of the lower mold 16.

In addition, a lower mold 16 is provided in the through hole 13 of the outer circumference regulating member 1).
A push rod 18 for pushing up is fitted so as to be movable up and down.

The forming method using the apparatus having the above-mentioned configuration consists of the outer circumference regulating member 1), the lower mold 16, the core 19, and the cladding 20, and a wire whose both ends have been processed into a mirror finish by grinding, polishing, etc. Expansion coefficient: 10 x 10-'
The single fiber glass material 21 at 10°C and the upper mold 17 are sequentially inserted.

Next, the outer periphery regulating member 1) is heated by the heater 14. Lower mold 1
6. The upper mold 17 and the single fiber glass material 21 are heated to a temperature at which the single fiber glass material 21 can be molded (see FIG. 2C).

Thereafter, the upper mold 17 is lowered to perform press molding (see Figure 2). At this time, the single fiber glass material 21 is prevented from deforming in the lateral direction by the outer periphery regulating member 1) that adjusts the upper mold 17 and the single fiber glass material 21 coaxially. Further, the air between the single fiber glass material 21 and the upper mold 17 is discharged from the air hole 15 of the outer periphery regulating member 1), and the air between the single fiber glass material 21 and the lower mold 1 is exhausted.
The air between the concave portion 16a of the mold 6 is discharged to the outside from the lower mold 16 made of a material with good air permeability, and after the press molding is completed, the heater 14 is stopped and the molded single fiber glass material 21 is deformed. Cool to a temperature that will not warm up. Thereafter, the push rod 18 is raised to push up the lower mold 16 and the molded single fiber glass material 21 is taken out. When taking out the single fiber glass material 21, the formed single fiber glass material 21 can be easily taken out by forming the outer periphery regulating member 1) of a material with a linear expansion coefficient smaller than that of the single fiber glass material 21.

Next, a part of the end surface of the molded single fiber glass material 21 on the lower mold 16 side is removed by grinding, polishing, etc., and is finished to a flat surface to obtain the desired optical element (plano-concave lens) 22 (second (See Figure C).

According to this embodiment, the outer circumference regulating member 1) and the upper and lower molds 17
．． 16 presses the single fiber glass material 21 without any gaps, so that the load is evenly applied to the entire single fiber glass material 21.

Therefore, it is easy to ensure the functional accuracy of the optical element 22.

(Second Embodiment) Figures 3a, b, and C show a second embodiment of the present invention, in which Figure 3a is a longitudinal sectional view, Figure 3 is a longitudinal sectional view during molding,
FIG. 3C is a cross-sectional view of the molded optical element.

In this embodiment, the step 12 in the first embodiment is abolished to form a step 23 that holds the single fiber glass material 21, and a plate-shaped lower mold 24 is used instead of the lower mold 16. The only difference is that the two components are constructed in the same way, and the other components are the same, so the same components are given the same numbers and their explanations will be omitted.

In this embodiment, a stepped portion 23 for holding the single fiber glass material 21 is formed on the inner peripheral surface of the outer periphery regulating member 25. In addition, a plate-shaped lower mold 2 is provided on the upper end surface of the push rod 18.
4 or fixed. The volume of the gap 26 formed by the single fiber glass material 21 and the lower mold 24 is larger than the volume formed in the single fiber glass material 21 by the upper mold 17.

The molding method using the apparatus having the above configuration is the same as that of the first embodiment, and the explanation of the operation will be omitted.

According to this embodiment, there is no need to pay particular attention to the shape and material of the lower mold 24, and the lower mold 24 can be made inexpensive. Therefore, the production cost of the optical element (plano-concave lens) 22 can be reduced.

(Third Embodiment) Figures 4a, b and C show a third embodiment of the present invention,
FIG. 4a is a longitudinal sectional view, FIG. 4 is a longitudinal sectional view during molding, and FIG. 4C is a sectional view of the molded optical element.

In this embodiment, an air hole 27 is further formed below the air hole 15 in the first embodiment, and an upper and lower mold 17 is formed.
．． The difference is that the upper and lower molding molds 29 and 28 are different from those of 16, and the other configurations are the same.
Identical components are given the same numbers and their explanations will be omitted.

In this embodiment, an aspherical concave expansion surface 28a corresponding to the desired functional surface of the optical element is formed on the upper surface of the lower mold 28 inserted into the outer periphery regulating member 30. Also,
A convex portion 29a having a volume larger than that formed on the single fiber glass material 21 by the lower mold 28 is formed on the lower surface of the upper mold 29.

A single fiber glass material 2 is attached to the side surface of the outer circumference regulating member 30.
An air hole 15 is formed for discharging the air between the opening between the single fiber glass material 21 and the lower mold 29, and furthermore, the air hole 15 is formed on the lower side surface of the opening for discharging the air between the single fiber glass material 21 and the concave expansion surface 28a of the lower mold 28. Air holes 27 are formed.

The molding method using the apparatus having the above configuration is to perform molding in the same manner as in the first embodiment, and then grind and polish a part of the end surface of the single fiber glass material 21 on the upper mold 29 side. The desired optical element (plano-convex lens) 31 is obtained by removing it by processing and finishing it into a flat surface.

According to this embodiment, a plano-convex lens can be processed.

(Fourth Embodiment) FIGS. 5a and 5b show a fourth embodiment of the present invention, in which FIG. 5a is a longitudinal sectional view and FIG. 5 is a sectional view of a molded optical element.

In this embodiment, instead of the lower mold 16 in the first embodiment, a lower mold 33 has a notch 32 formed at the upper part of the outer periphery to correspond to the cladding 20 of the single fiber glass material 21.
The only difference is that it is configured with , and the other configurations are the same, so the same components are given the same numbers and the explanation of the configuration will be omitted.

The molding method using the apparatus having the above configuration is similar to that of the first embodiment. At this time, since the cutout portion 32 is provided in the lower mold 33, no load is applied to the crut 20 of the single fiber glass material 21.

According to this embodiment, waviness of the interface 34 formed between the core 19 and the cladding 20 of the single fiber glass material 21 can be reliably prevented.

〔Effect of the invention〕

As explained above, according to the method for molding an optical element according to the present invention, when molding an optical element using a single fiber glass material consisting of a core and a cladding, the interface can be maintained in an appropriate state without waviness or the like. Pressure molding can be performed. Therefore, especially in the production of optical elements whose functional surfaces are aspherical, they can be manufactured at low cost and can be mass-produced.

[Brief explanation of the drawing]

FIGS. 1a, b, and C are conceptual diagrams showing the molding of a plano-concave lens by the optical element molding method according to the present invention. FIG. 1a is a longitudinal cross-sectional view showing the state before molding, and FIG. FIG. 1C is a sectional view of the molded optical element; FIGS. 2a, b, and C show the first embodiment; FIG. 2a is a longitudinal sectional view; Figure 2 is a longitudinal sectional view during molding, Figure 2C is a sectional view of the molded optical element, Figure 3a,
b and C show the second embodiment, FIG. 3a is a longitudinal sectional view, FIG. 3 is a longitudinal sectional view during molding, FIG. 3C is a sectional view of the molded optical element, and FIG. 4 a, b and C show the third embodiment, FIG. 4a is a longitudinal sectional view, FIG. 4C is a longitudinal sectional view, FIG. 4C is a sectional view of the molded optical element, and FIG. and b show the fourth embodiment, FIG. 5 a is a longitudinal sectional view, FIG. 5 is a sectional view of a molded optical element, and FIGS. 6 a and b are sectional views showing a conventional example. ■, 21...Single fiber glass material 2.19...
Core 3.20...Crat 4.34...Interface 5.1), 25.30...Outer circumference regulating member 6.7...
Molding die 8...Single fiber 12.23...Step part 13...Through hole 14...Heater 15.27...Air holes 16.24, 28.33...Lower mold 17. 29・-
・Lower mold 18...Push rod 22.31...Optical element 26...Gap 32...Notch portion Patent applicant: Olympus Optical Industry Co., Ltd. No. 1
Figure (a) (b) (c) 8・Single Phihar O ■Go to (/ Figure 5 (a) Figure 6 (a) (b)

Claims (1)

[Claims] (1) In a method for molding an optical element in which molding is performed by pressing molds on both ends of a single fiber glass material having flat ends, the single fiber glass material is inserted into an outer periphery regulating member and heated; A shape corresponding to the desired optical element functional surface is formed in one of the molds, a volume corresponding to the same or more of the shape is formed in the other mold, and the other mold is press-molded. A method for molding an optical element, characterized by removing a glass surface pressed by.