JPH05319836A - Method for forming optical element - Google Patents

Abstract

PURPOSE:To form an optical element without leaving gas between a forming die and a preform. CONSTITUTION:A plurally split dish 2 is arranged inside a dish 1 through a spring 3 and a preform 4 is pressed and held by the dish 2. The preform 4 is heated in a heating furnace and softened. When the preform 4 is softened, the dish 2 is pressed inwardly by the spring 3 until the gap is eliminated between the dishes. At this time, the outer diameter of the preform 4 is decreased, the preform is laterally swollen, the surface to be formed is convexed, the convex surfaces are then pressed by the dies 5 and 6, and the desired optical element is obtained.

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 method.

[0002]

2. Description of the Related Art When an optical element such as a glass lens used in an optical device such as a camera or a microscope is molded by a mold, if residual gas exists between the mold and the preform, residual gas is left on the molded lens surface. Since a hollow is caused by this, a technique for removing this residual gas is known, for example, in Japanese Patent Laid-Open No. 3-131537. The technique disclosed in this publication is a molding method in which a gas vent is provided on the surface of a mold and residual gas is discharged to the outside through the gas vent.

[0003]

However, the above-mentioned conventional technique has the following problems. That is, since the gas vent is provided on the optical function surface of the mold, the glass softened by heating during the press molding enters the gas vent, and small protrusions are formed on the optical function surface of the optical element. In most cases, these small protrusions should not be present in appearance.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a molding method using a molding die in which gas does not remain between the die and the preform.

[0005]

According to the optical element molding method of the present invention, when a preform having flat surfaces on both sides is heated and softened, a pressure capable of deforming the preform is applied from the outer periphery to give a predetermined deformation amount. After being given, it was decided to press by molding with an optical element molding die.

[0006]

According to the above-described optical element molding method, since the preform whose both surfaces are flat is heated and softened, a deformable pressure is applied from the outer periphery, so that the volume is reduced in the radial direction and the flat surface is reduced. The surface to be molded, which was, becomes the convex surface of the volume bulge. When molding an optical element having a convex surface with a preform having such a shape, the shape is close to the shape of the molding surface of the molding die, and the air layer between the preform and the molding surface is Less. Further, when the preform having a convex surface contacts from the axial center of the molding surface, the glass flows from the center toward the outer periphery, so that air does not remain. Therefore, an air layer does not remain between the molding die and the preform, and the transfer failure can be eliminated.

[0007]

Embodiment 1 FIGS. 1 to 3 show an optical element molding method of this embodiment. FIG. 1 is a sectional view of a molding process, and FIGS. 2 and 3 are plan views and sectional views of a holding mold. Show. In the figure, a preform 4 is held by a dish 2, and the dish 2 is held inside the dish 1 via a spring 3 in a state in which a zirconia ceramic spring having a spring constant of 59 gf / mm is contracted by 2 mm. Further, the plate 2 is divided into four and a gap is provided between each. Reference numerals 5 and 6 are an upper mold and a lower mold of a molding die, and press-mold the preform 4 into a desired optical element shape.

The preform 4 is held by the dishes 1 and 2 and heated in a heating furnace until the preform 4 is softened.
When the preform 4 is softened, the plate 2 is pushed inward by the spring 3 until there is no gap between the plates. At this time, the outer diameter of the preform 4 becomes smaller, and the preform 4 bulges in the axial direction and the molding surface becomes a convex surface. When the molding surfaces of the molding dies (5, 6) are concave surfaces, the molding surface of the preform 4 is a convex surface, so that they come into contact with each other from the center, and the molding surface and the mold molding surface are pressed at the time of pressing. No air remains between them, and good transferability can be obtained.

Next, referring to specific examples, the outer diameter 5
SK11 is used as a glass material having a thickness of 3 mm and a thickness of 3 mm and having both surfaces flattened, and is first held in dishes 1 and 2 and heated in a furnace at 850 ° C. for 60 seconds. When this was cooled without pressing and the shape was measured, the outer diameter was 4.0 mm and the inner thickness was 6.2 mm. The shape of the preform 4 is as shown in FIG. 1, and the preform 4 comes into contact with the molding surfaces of the upper mold 5 and the lower mold 6 from the center toward the outer periphery. Therefore, no air remained between the molding die and the preform, and good transfer accuracy could be obtained.

[0010]

[Embodiment 2] FIG. 4 shows a method of molding an optical element according to the present embodiment, in which two end arms 12 capable of rotating around the front end are provided at the front end of a transfer arm 11. The spring 15 acts on these, and they can be stopped by the gap 16. A holding portion 13 is fixed to the tip arm 12, and holds the preform 4. The gap 17 is larger than the gap 16 and prevents pressure from acting on the protruding glass and cracking.

The transfer member including the transfer arm 11 having the above-described structure transfers the zirconia ceramic spring having a spring constant of 300 gf / mm by 3 mm from the outer diameter of the zirconia ceramic spring. When the arm 11 is heated together, the outer diameter becomes smaller when the preform 4 is softened, and the surface to be molded of the preform 4 has a convex surface correspondingly, and the same result as in the above-described Example 1 is obtained.

Next, a description will be given based on a concrete example.
BK7 is used as a glass material having a thickness of 4 mm and a thickness of 4 mm and having both surfaces flattened, and heated in a furnace at 890 ° C. for 60 seconds. When this was cooled without pressing and the shape was observed, the shape was similar to the shape of the preform 4 in FIG. 3 described above. When molding was performed using a mold having a concave surface in the same manner as in Example 1 described above, no air remained and good transfer accuracy could be obtained.

[0013]

[Embodiment 3] FIGS. 5 and 6 show an optical element molding method according to the present embodiment, in which a tray 23 is placed inside a tray 24, and the tray 23 has an open portion (partially cut off). Portion 26 is provided, the tightening band 22 is placed inside the dish 23, and the protrusion 27 of the tightening band 22 is pressed by the cylinder device 25. The cylinder device 25 is composed of cylinders 25a and 25b as shown in FIG. 6, and hermetically seals air inside. When the temperature of the preform 4 is raised as the preform 4 is heated, the sealed air expands and the cylinders 25a and 25b extend to press the protrusion 27. Therefore, unlike the above-described first and second embodiments, the pressure is applied from the substantially uniform outer circumference.

Next, referring to specific examples, the outer diameter 1
SF6 is placed on a dish 23, 24 on a glass material having a flat surface of 0 mm and a thickness of 3 mm and having flat surfaces on both sides, heated in a furnace at 750 ° C. for 60 seconds, and molded by a molding die having a concave molding surface. did. It was possible to obtain good transfer accuracy without residual air in the molded optical element.

In the case of a dish having a structure in which pressure is not applied from the outer periphery of the preform 4 instead of the dish having the above-mentioned structure, undulations caused by residual air are generated on the surface of the optical element and sufficient transfer accuracy is obtained. I couldn't get it.

In each of the above-mentioned embodiments, the case where the outer circumference of the preform has a cylindrical shape has been described, but the preform is not limited to a cylindrical shape and can be similarly implemented and the same effect can be obtained.

[0017]

As described above, according to the optical element molding method of the present invention, the surface to be molded of the flat preform is made to be a convex surface before pressing by applying pressure from the outer periphery during heating of the preform. Therefore, when pressed with a molding die having a concave molding surface, the molding surface of the preform contacts the molding surface of the mold from the center, so no air residue occurs and good transfer accuracy can be obtained. , It was possible to improve the quality of the optical element.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a preform pressure molding step in an optical element molding method according to a first embodiment of the present invention.

FIG. 2 is a plan view of a holding mold in the optical element molding method of the example.

FIG. 3 is a cross section of the holding mold of the same embodiment.

FIG. 4 is a plan view of a holding mold in an optical element molding method according to a second embodiment of the present invention.

FIG. 5 is a plan view of a holding mold in an optical element molding method of Example 3 of the present invention.

FIG. 6 is a cross-sectional view of a cylinder used as a holding mold in the optical element molding method of the example.

[Explanation of symbols]

 1 plate 2 plate 3 spring 4 preform 5 upper mold 6 lower mold

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tetsuo Izawa 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd.

Claims (1)

[Claims] 1. A method of softening a preform having a flat surface on both sides by heating to mold an optical element having a convex surface with an optical element molding die, when the preform is softened from the outer periphery of the preform during heating of the preform. An optical element molding method, characterized in that an optical element having a convex surface is obtained by heating to a moldable temperature while applying a deformable pressure, and then molding by an optical element molding die.