JP2000247653A - Metal mold for forming optical element and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal mold for forming optical elements which is capable of absorbing the weight errors of optical element blanks and makes it possible to obtain the high-accuracy optical elements without the occurrence of cracking in a press forming method for the optical elements. SOLUTION: The metal mold 10 for forming the optical elements consisting of a pair of upper and lower molds 11 and 12 for use in press forming of the optical elements and a drum mold 13 for slidably holding the upper and lower molds is provided with a hollow groove 14 for a weight absorbing part in at least part of the sliding surface of the drum mold 13. The weight fluctuation component of the optical element blank 30 may be absorbed by the groove 14 and the lenses having desired shapes at both sides may be formed without the occurrence of cracking after forming at a good yield and low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding die and an optical element for forming high-precision optical elements such as lenses and prisms used in optical equipment at low cost by an ultra-precision molding method. is there.

[0002]

2. Description of the Related Art In recent years, optical elements such as lenses and prisms are formed by putting a material for an optical element into a mold and heating and pressing the material instead of polishing the material for the optical element such as glass. Many have been proposed.

As such a method, generally, a method of pre-processing an optical element material into a predetermined shape, supplying the pre-processed material between a pair of upper and lower dies, and performing heat-press molding (reheat press method) is generally used. When molding a precise optical element by such a method, the shape, surface smoothness and weight accuracy of the optical element material occupy very important factors, and until now, ball glass materials and cylindrical glass materials (round rods have been Or a gob material into which molten glass is dropped. The weight accuracy required when molding such an optical element material depends on the configuration of the mold.

FIG. 7 shows a schematic configuration of a molding die used for molding an optical element by a conventional reheat press method. 7, 100 and 110 are optical element molding dies, 101 and 111 are upper dies, 102 and 112 are lower dies, 1
03 and 113 are upper dies 101 and 111 and lower dies 102 and 1
The body type holding the numeral 12 and 104 and 114 are optical element materials. At least one of the upper dies 101 and 111 and the lower dies 102 and 112 can move up and down in the body dies 103 and 113.

For example, as shown in FIG. 7A, a mold (mold cavity> optical element volume) having a free-form surface other than the optical function surface of the optical element (for example, outer periphery) is used. If so, the weight accuracy required for the optical element material is not so strict, and the material itself can be processed at low cost. However, in this case, after molding the optical element, it is necessary to perform centering in order to make the outer diameter and the like uniform, and the cost is increased accordingly.

On the other hand, for example, as shown in FIG. 7 (B), if the mold is (mold cavity = volume of optical element), processing after molding is not required, and The weight accuracy required for the element material is very strict and high cost is required.

The above-mentioned problem has been solved in Japanese Patent Laid-Open No. Hei 4-16.
No. 8789. According to this publication, in molding an optical element in which an optical element material is supplied into a molding die and heated and pressurized, an upper and lower mold having different outer diameters can be formed by using a barrel mold having a stepped inner shape. There is described a technique that can be used and absorbs the weight of an optical element material.

[0008]

However, in the technique disclosed in the above publication, a stepped shape is provided inside the body mold, so that it is necessary to provide a space for absorbing the weight on one surface of the optical element. Therefore, an air heat insulating layer is formed, and the temperature is hard to rise only at that portion, the temperature distribution in the same plane is not uniform, and the performance as an optical element cannot be obtained, or cracks occur due to a temperature difference during cooling. Problem.

An object of the present invention is to provide an optical element molding die capable of absorbing a weight error of an optical element material and obtaining a high-precision optical element at low cost without causing cracks or the like. Aim. Another object of the present invention is to provide an inexpensive optical element with high precision on both sides and no cracks.

[0010]

The present invention has the following configuration to achieve the above object.

That is, a mold for molding an optical element according to the first structure of the present invention comprises a pair of upper and lower molds used for press molding of an optical element, and a cylinder for slidably holding at least one of the upper and lower molds. A mold for molding an optical element comprising a mold and
It is characterized in that at least a part of the sliding surface of the body mold has a concave groove.

Further, a mold for molding an optical element according to a second configuration of the present invention comprises a pair of upper and lower molds used for press molding of an optical element, and a cylinder for slidably holding at least one of the upper and lower molds. A mold for molding an optical element comprising a mold and
At least one of the upper and lower molds has a concave groove on a surface facing the sliding surface of the body mold.

According to the first or second configuration, the weight error of the optical element material can be absorbed by the concave groove, so that the allowable range of the weight error of the optical element material is widened. Further, since the groove is formed on the sliding surface or the opposing surface thereof, it does not adversely affect the molding accuracy of a portion that functions as an optical element, and it is possible to obtain a high-precision optical element without cracking. it can. Further, there is no need to perform centering after molding, and a low-cost optical element can be obtained.

In the above configuration, it is preferable that the concave groove is arranged so as to affect the outer diameter of the optical element. According to this preferred configuration, the weight error of the optical element material can be easily absorbed by the groove.

Further, the optical element of the present invention is characterized in that it is molded using the optical element molding die according to the first or second configuration. According to this configuration, the weight error of the optical element material at the time of molding can be absorbed by the concave groove, and it is not necessary to perform centering processing after molding, so that an optical element with high precision and low cost can be obtained.

[0016]

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of an optical element molding apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram of a barrel of the optical element molding die according to the first embodiment;
(A) is a plan view, and (B) is a cross-sectional view as seen from the direction of the arrow along the line II in (A). 3A and 3B are schematic diagrams of the optical element according to Embodiment 1, wherein FIG. 3A is a plan view and FIG. 3B is a side view.

As shown in FIGS. 1 and 2, an optical element molding die 10 of the present embodiment includes an upper mold 11 having a molding surface for obtaining an optical element 1 having a desired shape, and an upper mold 11. It comprises a lower mold 12 provided coaxially opposite to 11 and having a molding surface for obtaining a desired optical element 1, and a body mold 13 for holding the upper mold 11 and the lower mold 12 coaxially. The upper die 11 is slidably held by using the inner peripheral surface 13a of the body die 13 as a sliding surface. The body mold 13 has a concave groove 14 in a part of the sliding surface 13a.

Each member of the optical element molding die 10 is formed of a cemented carbide mainly composed of tungsten carbide (WC), and the molding surfaces of the upper and lower dies 11, 12 are mirror-finished to a desired shape. And is covered with a platinum (Pt) -based alloy protective film.

The glass type of the optical element 1 is, for example, barium borosilicate glass VC79 (glass transition temperature Tg).
= 516 ° C and a coefficient of linear expansion α = 93 × 10 ^-7 (100-300 ° C).

As shown in FIG. 1, a mold 10 for molding an optical element is vertically held by press heads 31 and 32 and a heater 3 embedded in the press heads 31 and 32.
Heated at 3,34. The optical element material 30 is placed between the upper and lower dies 11 and 12, and is pressed into a desired shape by a press cylinder 36 in a direction indicated by an arrow in the drawing.

Next, a molding method will be described.

First, a ball-shaped optical element material 30 is placed on the lower mold 12. Then, the concave groove 14 is
Then, the upper mold 11 is slid and inserted. Thereafter, the optical element molding die 10 is placed on the optical element molding apparatus shown in FIG. Next, the press head 31 is slowly lowered to make contact with the upper mold 11 of the optical element molding die 10. Thereafter, the press heads 31 and 32 are heated to predetermined temperatures by the heaters 33 and 34, and the optical element material 30 in the optical element molding die 10 is heated to a temperature at which pressure molding can be performed. Thereafter, when the temperature of the optical element material 30 reaches a temperature at which pressure can be applied, a high load is applied to the press cylinder 36 to apply pressure until the gap 35 disappears, and the deformation is completed.

At this time, even if the weight variation of the optical element material 30 is large, the excess weight is absorbed by the concave groove 14 provided on the inner surface of the barrel 13 and the optical element can obtain a desired shape on both upper and lower surfaces. It becomes possible. That is, the weight tolerance becomes wide.

After completion of the deformation, the temperature is lowered to the glass transition point or lower and the pressure is applied for a predetermined time in order to keep the shape of the molding surface good. Thereafter, the optical element molding die 10 is removed from the optical element molding apparatus, the upper mold 11 is removed, the body mold 13 is removed, and the optical element 1 is removed.

The optical element 1 made by such a method
Has a shape as shown in FIG. 3, and it is possible to form a desired shape on both surfaces without cracking. Further, a convex weight absorbing portion 1 a is present on the end face of the optical element 1. Weight absorber 1a
The shape accuracy in the in-plane direction perpendicular to the optical axis of the
4, the weight absorbing portion 1a can be effectively used for positioning the optical element when mounting the optical device, and there is no need for centering. Further, the optical element material 30
The optical element material 30 can be obtained at a low cost because the weight tolerance of the optical element 30 is wide, and as a result, the obtained optical element is also low.

In the above description, an example in which the optical element 1 is a convex lens has been described. However, a concave lens or a meniscus lens may be used, and the same effect can be obtained.

(Embodiment 2) Hereinafter, Embodiment 2 of the present invention will be described with reference to the drawings.

FIG. 4 is a schematic sectional view of an optical element molding apparatus according to Embodiment 2 of the present invention. FIG. 5 is a schematic diagram of a lower mold of the optical element molding die according to the second embodiment.
2A is a plan view, and FIG. 2B is a cross-sectional view taken along the line II-II in FIG. FIGS. 6A and 6B are schematic diagrams of an optical element according to Embodiment 2, in which FIG. 6A is a front view and FIG. 6B is a side view.

As shown in FIGS. 4 and 5, an optical element molding die 20 according to the present embodiment includes an upper mold 21 having a molding surface for obtaining an optical element 2 having a desired shape, and an upper mold 21. A lower mold 22 having a molding surface for obtaining a desired optical element 2 is provided coaxially with and opposed to 21, and a body mold 23 for holding the upper mold 21 and the lower mold 22 coaxially. The upper die 21 is slidably held by using the inner peripheral surface of the body die 23 as a sliding surface. The lower mold 22 has a surface 2 facing the inner peripheral surface of the body mold 23.
2a has a concave groove 24 in a part thereof.

Each member of the optical element molding die 20 is formed of a cemented carbide mainly composed of tungsten carbide (WC), and the molding surfaces of the upper and lower dies 21, 22 are mirror-finished to a desired shape. And is covered with a platinum (Pt) -based alloy protective film.

The glass type of the optical element 2 is, for example, barium borosilicate glass VC79 (glass transition temperature Tg).
= 516 ° C and a coefficient of linear expansion α = 93 × 10 ^-7 (100-300 ° C).

As shown in FIG. 4, a mold 20 for molding an optical element is vertically held by press heads 31 and 32 and a heater 3 embedded in the press heads 31 and 32.
Heated at 3,34. The optical element material 30 is placed between the upper and lower molds 21 and 22 and is pressed into a desired shape by a press cylinder 36 in the direction of the arrow in the drawing.

Next, the molding method will be described.

First, the lower mold 2 provided with the concave groove 24 in the sliding direction.
The ball-shaped optical element material 30 is placed on the substrate 2. Thereafter, the body mold 23 is fitted, and finally the upper mold 21 is slid and inserted. Thereafter, the optical element molding die 20 is placed on the optical element molding apparatus shown in FIG. Next, the press head 31 is slowly lowered to make contact with the upper die 21 of the optical element molding die 20. Then, the press heads 31 and 32 are
The temperature is raised to a predetermined temperature at 3, 34, and the optical element material 30 in the optical element molding die 20 is heated to a temperature at which pressure molding is possible. Thereafter, when the temperature of the optical element material 30 reaches a temperature at which pressure can be applied, a high load is applied to the press cylinder 36 to apply pressure until the gap 35 disappears, and the deformation is completed.

At this time, even if the weight variation of the optical element material 30 is large, the excess weight is absorbed by the concave groove 24 provided in the lower mold 22 so that the optical element can obtain a desired shape on both upper and lower surfaces. Become. That is, the weight tolerance becomes wide.

After the deformation, the temperature is lowered to the glass transition point or lower and the pressure is applied for a predetermined time in order to keep the shape of the molding surface good. Thereafter, the optical element molding die 20 is removed from the optical element molding apparatus, the upper mold 21 is removed, the body mold 23 is removed, and the optical element 2 is removed.

Optical element 2 made by such a method
Has a shape as shown in FIG. 6, and it is possible to form a desired shape on both surfaces without cracking. Further, a convex weight absorbing portion 2 a exists on the end face of the optical element 2. Weight absorber 2a
Since the shape accuracy in the in-plane direction perpendicular to the optical axis is ensured by the inner peripheral surface of the barrel mold 23, the weight absorbing portion 2a can be effectively used also as a positioning when the optical element is mounted on the device, and There is no need for machining. Further, the optical element material 30
The optical element material 30 can be obtained at a low cost because the weight tolerance of the optical element 30 is wide, and as a result, the obtained optical element is also low.

In the above description, an example has been described in which the optical element 2 is a convex lens. However, a similar effect can be obtained with a concave lens or a meniscus lens.

The concave groove 24 may be formed in the upper mold 21 instead of the lower mold 22, or may be formed in both.

[0041]

As described above, according to the present invention, since a concave groove is provided on the sliding surface of the body mold or the sliding surface of the mold, the concave groove absorbs the weight error of the optical element material, The allowable range of the weight error of the optical element material is widened. Further, it is possible to obtain a high-precision optical element without cracking without adversely affecting the molding accuracy of a portion exhibiting a function as an optical element. Further, there is no need to perform centering after molding, and a low-cost optical element can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an optical element molding apparatus according to Embodiment 1 of the present invention.

2A and 2B are schematic views of a barrel of an optical element molding die used in the apparatus of FIG. 1, wherein FIG. 2A is a plan view and FIG. 2B is a direction of an arrow along a line II in FIG. It is sectional drawing seen from.

3A and 3B are schematic diagrams of the optical element according to the first embodiment, wherein FIG. 3A is a plan view and FIG. 3B is a side view.

FIG. 4 is a schematic sectional view of an optical element molding apparatus according to a second embodiment of the present invention.

5A and 5B are schematic views of a lower mold of an optical element molding die used in the apparatus of FIG. 4, wherein FIG. 5A is a plan view and FIG. 5B is an arrow direction along line II-II in FIG. It is sectional drawing seen from.

FIG. 6 is a schematic view of an optical element according to a second embodiment, where (A) is a front view and (B) is a side view.

FIG. 7 is a cross-sectional view schematically illustrating an optical element molded using a conventional optical element molding die.

[Explanation of symbols]

 Reference numerals 1, 2 Optical elements 1a, 2a Weight absorbing part 10 Optical element molding die 11 Upper die 12 Lower die 13 Trunk die 13a Inner peripheral surface of trunk die 14 Concave groove 20 Optical die molding die 21 Upper die 22 Lower Mold 22a Opposite surface with inner peripheral surface of body mold 23 Body mold 24 Concave groove 30 Optical element material 31, 32 Press head 33, 34 Heater 35 Gap 36 Press cylinder 100, 110 Mold for optical element molding 101, 111 Mold 102,112 Lower mold 103,113 Body mold 104,114 Optical element material

Claims (6)

[Claims] 1. An optical element molding die comprising: a pair of upper and lower molds used for press molding of an optical element; and a body mold slidably holding at least one of the upper and lower molds, wherein the body mold is used. Characterized in that at least a part of the sliding surface of (1) has a concave groove. 2. The optical element molding die according to claim 1, wherein the concave groove is arranged so as to affect the outer diameter shape of the optical element. 3. An optical element molded using the optical element molding die according to claim 1. 4. An optical element molding die comprising: a pair of upper and lower molds used for press molding of an optical element; and a body mold for slidably holding at least one of the upper and lower molds, wherein the upper and lower molds are provided. Characterized by having a concave groove on at least one of the surfaces facing the sliding surface of the body die. 5. The optical element molding die according to claim 4, wherein the concave groove is arranged so as to affect the outer diameter shape of the optical element. 6. An optical element molded using the optical element molding die according to claim 4. Description: