JP3220515B2 - Optical element molding method - Google Patents

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 for an optical apparatus such as a camera or a microscope is conventionally molded by a mold, if there is residual gas between the mold and the preform, the residual gas is formed on the surface of the molded lens. Therefore, a technique for removing the residual gas is known, for example, from Japanese Patent Application Laid-Open No. HEI 3-13137. 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 prior art 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 at the time of press molding enters the gas vent, and small projections are generated on the optical function surface of the optical element. In most cases, these small projections should not be present in appearance.

[0004] The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to provide a molding method using a molding die in which no gas remains between the die and the preform.

[0005]

SUMMARY OF THE INVENTION An optical element molding method according to the present invention is characterized in that a preform, for example, a preform having both flat surfaces, is heated and softened to apply a pressure capable of deforming the preform from the outer peripheral side. After giving a predetermined amount of deformation, the optical element is pressed by being molded using an optical element molding die.

[0006]

According to the above-described optical element molding method, the preform is heated and softened, and the deformable pressure is applied from the outer peripheral side, so that the volume is reduced in the radial direction.
The surface to be molded becomes this volume swelling convex surface. For example, when both surfaces of the molding surface of the preform are flat, the molding surface has a bulging convex surface. When trying to mold 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 mold molding surface is Less. In addition, when the convex preform comes in contact with the center of the axis of the molding surface, the glass flows from the center to the outer periphery, so that air does not remain. Therefore, an air layer does not remain between the molding die and the preform, and transfer defects can be eliminated.

[0007]

1 to 3 show an optical element molding method according to the present embodiment. FIG. 1 is a sectional view of a molding step, and FIGS. 2 and 3 are a plan view and a sectional view of a holding mold. Show. In the figure, a preform 4 is held by a plate 2, and the plate 2 is held inside a plate 1 via a spring 3 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 denote an upper mold and a lower mold, respectively, and press-mold the preform 4 into a desired optical element shape while holding the preform 4 on the plates 1 and 2.

The preform 4 is held by the above-mentioned 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 preform 4 is pushed from the outer peripheral side to reduce the outer diameter,
The molding surface bulges in the axial direction by that amount, and the molding surface becomes convex. When the molding surface of the molding die (5, 6) is concave, the molding surface of the preform 4 is convex, so that the preform 4 comes into contact from the center, and the molding surface and the molding surface are pressed during pressing. Good transferability can be obtained without air remaining in between.

Next, a description will be given based on a specific example.
SK11 is used as a glass material having a thickness of 3 mm and a flat surface on both sides, and is heated in an oven at 850 ° C. for 60 seconds while being held in dishes 1 and 2. This was cooled without being pressed, and the shape was measured. As a result, 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 molding surfaces of the upper die 5 and the lower die 6 of the molding die come into contact 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 an optical element molding method according to the present embodiment, in which two end arms 12 rotatable around the end are provided at the end of a transfer arm 11. These can be stopped by the gap 16 due to the action of the spring 15. Further, a holding portion 13 is fixed to the distal end arm 12, thereby holding the preform 4. The gap 17 is made larger than the gap 16 to prevent the protruding glass from being broken by pressure.

The transfer member including the transfer arm 11 and the like having the above-described structure applies a pressure from the outer diameter (outer side) to the preform 4 by a spring 15 in which a zirconia ceramic spring having a spring constant of 300 gf / mm is extended by 3 mm. Therefore, when the entire transfer arm 11 is heated, the preform 4
Is softened, the outer diameter becomes smaller, and the molding surface of the preform 4 has a convex surface by that much, and when molding is performed by a molding die (not shown) while being held in the holding portion 13,
The same result as in the first embodiment can be obtained.

Next, a description will be given based on a specific example.
BK7 is used for a glass material having a thickness of 4 mm and a thickness of 4 mm, and both surfaces of which are polished flat, and heated in a furnace at 890 ° C. for 60 seconds. This was cooled without pressing, and the shape was observed. As a result, 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]

Third Embodiment FIGS. 5 and 6 show an optical element molding method according to the present embodiment. A plate 23 is placed inside a plate 24, and a release portion (partially cut off) is placed on the plate 23. A portion 26 is provided, the fastening band 22 is placed inside the plate 23, and the projection 27 of the fastening band 22 is pressed by the cylinder device 25. This cylinder device 25 is composed of cylinders 25a and 25b as shown in FIG. 6, and seals air inside. When the temperature is increased together with the heating of the preform 4, the sealed air expands, and the cylinders 25 a and 25 b extend to press the projection 27. Therefore, unlike the first and second embodiments, the pressure is applied from the substantially uniform outer peripheral side.

Next, a description will be given based on a specific example.
Glass material SF6 having a thickness of 0 mm and a wall thickness of 3 mm, both surfaces of which are mirror-finished, is placed on plates 23 and 24, and heated in a furnace at 750 ° C. for 6 hours.
After heating for 0 seconds, the glass material is deformed into a convex shape.
It was molded with a molding die having a concave molding surface while being placed on the substrates 3 and 24. Good transfer accuracy was obtained on the optical element after molding without air residue.

In the case of a dish which does not apply pressure from the outer periphery of the preform 4 instead of the dish having the above-described structure, undulations generated due to remaining air are generated on the surface of the optical element, and sufficient transfer accuracy can be obtained. I couldn't get it.

In each of the embodiments described above, the case where the outer periphery of the preform is cylindrical has been described. However, the present invention is not limited to the columnar shape, and the same effect can be obtained if the preform is columnar.

[0017]

As described above, according to the optical element molding method of the present invention, the surface to be molded of the preform is made convex before pressing by applying pressure from the outer peripheral side during heating of the preform. Therefore, when pressed with a molding die having a concave molding surface, the molding surface of the preform comes in contact with the molding surface of the mold from the center, so that no air remains, and good transfer accuracy can be obtained. Thus, the quality of the optical element could be improved.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a holding die in the optical element molding method of the embodiment.

FIG. 3 is a cross-sectional view of the holding die of the embodiment.

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

FIG. 5 is a plan view of a holding die in an optical element molding method according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a cylinder used for a holding mold in the optical element molding method of the embodiment.

[Explanation of symbols]

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

Continuation of the front page (72) Inventor Tetsuo Izawa 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Industrial Co., Ltd. (56) References JP-A-63-176319 (JP, A) JP-A-1-119536 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C03B 11/00-11/16

Claims (2)

(57) [Claims] In a method of heating and softening a preform and molding an optical element having a convex surface by an optical element molding die, the preform is deformed when the preform is softened from the outer peripheral side of the preform during heating. After the surface to be molded is inflated by heating to a moldable temperature while applying a pressure capable of being applied, an optical element having a convex surface is obtained by molding this surface with an optical element molding die. Optical element molding method. 2. A method for heating and softening a preform and molding an optical element having a convex surface by an optical element molding die, wherein the preform is softened from the outer peripheral side of the preform during heating of the preform having both flat surfaces. After heating to a moldable temperature while applying a pressure capable of being deformed when the surface is inflated to inflate the plane, an optical element having a convex surface is obtained by molding the inflated surface with an optical element molding die. An optical element molding method, characterized in that: