JPH05178631A - Method for forming optical element - Google Patents

Abstract

PURPOSE:To control the thickness of an optical element to be formed with high precision and reduced variance. CONSTITUTION:An annular barrel die 4 carrying an optical glass material 6 is inserted and disposed between a couple of the upper and lower dies 1 and 2, and an opening 16 from which the material 6 is protruded out onto the periphery of the die in press forming is formed between the inner diameter 11 of the upper surface of the barrel die 4 and the outer diameter of the upper die 1. An annular presser member 5 capable of being freely moved up and down along the periphery of the upper die 1 is provided to the opening 16. The member 5 is operated when the material 6 is formed to a desired thickness by the dies 1 and 2 to press the protruded material 6. Meanwhile, a large-diameter step 10 is formed at the base of the lower die 2, and a stopper 3 is disposed on the step to stop the lower die 2 when the lower die is raised and the material 6 is formed to a desired thickness between the lower die and the lower end face of the barrel die 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding an optical element such as glass.

[0002]

2. Description of the Related Art Optical elements such as glass lenses used in optical devices such as cameras, microscopes and telescopes must be molded so that the center thickness of the lenses is constant. As a document describing the technique of forming the lens thickness constant, there is, for example, Japanese Patent Laid-Open No. 61-205630. The technique disclosed in this publication is a molding method in which the pressing of the press is stopped by a position variable stopper, and the optical element is pressed in conjunction with the cooling and solidification shrinkage of the optical element. ..

However, in the technique disclosed in the above publication,
In order to obtain the accurate wall thickness of the molded optical element,
There are two problems. One is that when the die is stopped by a stopper during pressing, the optical glass material shrinks without applying pressure. Therefore, the thickness dimension of the optical element after pressing depends on the shrinkage amount. That is, there is a problem that the thickness of the optical element varies due to the temperature conditions. In addition, depending on the shape, the amount of shrinkage is uneven, so that the surface shape called a sink mark is distorted and the surface accuracy is extremely deteriorated. Another problem is that the die is stopped by a stopper at the time of pressing, and the stopper is operated in conjunction with the contraction of the optical glass material to pressurize. However, since it is formed depending on the shrinkage amount, there is a problem that the thickness dimension varies. As described above, it has been difficult to obtain a correct thickness dimension based on the molding method having two problems and further to reduce the variation.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and makes it possible to form an optical element with a high accuracy and a small variation by a simple method. Another object of the present invention is to provide a high-quality and cost-effective optical element molding method.

[0005]

According to the present invention, an optical glass material placed on a barrel mold is heated to a predetermined temperature and conveyed between an upper mold and a lower mold for pressure molding. In the method of molding an optical element in which the pressurization is stopped at a position where the optical element to be press-molded has a desired wall thickness dimension, by the pressure provided between the barrel mold and the mold. This is a method for molding an optical element in which the protruding optical glass material is pressed against the protruding portion of the optical glass material at the same time when the mold is stopped.

[0006]

Example 1 A specific example of the method for molding an optical element of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view from the front showing the main part of a molding apparatus of Example 1 relating to the method for molding an optical element of the present invention. As shown in the figure, a pair of upper and lower molding dies 1 and 2 are arranged coaxially, and the lower mold 2 is vertically moved (arrow) to be press-molded. A step portion 10 having a large diameter is formed at the lower end portion of the lower mold 2, and a stopper 3 is arranged on the upper surface of the lower die 2 so that the thickness of the molded optical element can be regulated so as to have a desired dimension value. It is set up.
The ring-shaped member disposed between the upper mold 1 and the lower mold 2 shown in the figure and having the recess 11 formed on the upper surface thereof is not shown, but is made of an optical glass material from the outside by a transfer arm. A preform 6 is placed on the body mold 4 which is conveyed and mounted between the pair of molding dies 1 and 2.
The concave portion 1 on the upper surface on which the optical glass material 6 of the barrel die 4 is placed
The inner diameter of 1 is larger than the outer diameter of the upper die 1, and the hole 12 formed in the center of the bottom surface of the recess 11 is
The molding part at the tip of the lower mold 2 is formed so that it can be inserted.

Between the outer periphery of the upper mold 1 and the inner periphery of the recess 11 of the body mold 4, when the optical glass material 6 is press-molded, the protrusion opening of the protrusion portion 7 of the optical glass material 6 is formed. It constitutes part 16. In order to press-mold the protruding opening 16, the upper mold 1 is provided on the outer periphery of the upper mold 1 as shown in the figure.
A ring-shaped pressing member 5 having a hole 13 is arranged so as to slide in the axial direction. The outer diameter of the pressing member 5 is formed so as to fit with the inner diameter of the recess 11 of the body mold 4. A ring-shaped tip end surface (lower end surface shown in the figure) of the pressing member 5 is formed in a taper shape inwardly so as to press the protruding portion 7 of the optical glass material 6. Further, a driving means (not shown) for slidingly moving the pressing member 5 in the vertical direction (arrow direction) and a connecting member 14 configured to be connected are provided on the outer peripheral wall of the upper end portion of the pressing member 5.
Further, as shown in the figure, the heater 8 is provided on the outer peripheral surface of the pressing member 5 so as to keep the optical glass material 6 at a high temperature at all times so that the optical glass material 6 is not rapidly cooled during the press molding of the pressing member 5.
Is provided.

A molding method of this embodiment having the above-mentioned structure will be described. The optical glass material (preform) 6 whose both surfaces are formed flat is placed in the recess 11 of the barrel die 4, and the barrel die 4 is placed on a transport arm (not shown) to bring the optical glass material 6 to a desired softening temperature. After heating, it is conveyed between the upper mold 1 and the lower mold 2. When the lower die 2 is moved upward from below the conveyed body die 4, the molding surface of the tip of the lower die 2 projects above the hole 12 provided in the step portion of the body die 4, and the optical glass While coming into contact with the material 6, the step portion 15 provided at the tip of the lower mold 2 comes into contact with the lower surface edge of the hole 12 of the body mold 4,
The body mold 4 is lifted and raised. As the lower mold 2 rises, the optical glass material 6 is press-molded by the upper mold 1. The ascent of the lower mold 2 ascends until the stopper 3 comes into contact with the upper surface of the step portion 10 at the base end of the lower mold 2, and the ascending operation is stopped by coming into contact with the stopper 3. Simultaneously with the stop of the lower mold 2, the pressing member 5 moves downward along the outer peripheral surface of the upper mold 1 to form an optical structure between the outer periphery of the upper mold 1 and the recess 11 of the body mold 4. The glass material 6 is pressed against the upper surface of the protruding portion 7 by pressing.

After the molding of the protruding portion 7 is completed, the optical glass material 6 is cooled, the pressing member 5 is moved upward and slidably, and the lower die 2 is moved downward to be molded. The optical element is transferred to the next process together with the barrel die 4, and the molding is completed.

When the optical element is molded by the above-described molding method, the standard of the desired thickness dimension is 2.00 to 2.00.
While it was in the range of 2.02, it was a value that cleared it sufficiently. Moreover, there was almost no variation in the thickness of the optical element. Further, the transfer accuracy was good, and the phenomenon of sink marks did not occur, and a highly accurate and high quality optical element could be molded.

[0011]

[Embodiment 2] FIG. 2 is a sectional view from the front, showing the essential parts of a molding apparatus according to Embodiment 2 of the method for molding an optical element of the present invention. As shown in the figure, a pair of upper and lower molding dies 21 and 22 each formed in a columnar shape are coaxially arranged, and are configured to be press-molded by the vertical movement (arrow) of the lower mold 22. .. Further, a step portion 23 having a large diameter is formed at a lower end portion of the lower die 22, and the upper surface of the step portion 23 has a body die 2
The cylindrical stopper 24 whose axial direction is regulated and formed corresponding to the thickness dimension value of the optical element mounted and molded on the upper surface of the roller 5 is brought into contact with the outer peripheral edge portion of the lower end surface of the barrel die 25. Is attached to. That is, when the lower die 22 rises, the stopper 24 also rises, and the tip of the stopper 24 abuts the lower surface of the barrel die 25 to raise the barrel die 25. Further, the upper end surface of the barrel die 25 is configured to come into contact with the step portion of the upper die 21 to stop the lifting of the lower die 22. A cylindrical mold 25 having a ring shape arranged between the upper mold 21 and the lower mold 22 and having a step portion 27 for mounting the optical glass material 26 on the lower end of the inner diameter is arranged. There is. Although not shown, the body mold 25 has an optical glass material 26, which is a molding material, placed from the outside by a transfer arm, and the pair of upper and lower molds 21 and 2 are formed.
It is configured to be conveyed to and molded between the two.

The inner diameter of the stepped portion 27 formed to mount the optical glass material 26 on the upper surface of the barrel die 25 is
The diameter is larger than the outer diameter of the tip of the lower die 22. That is, in the middle of the axis of the cylindrical lower mold 22, a step portion 2 having a small diameter is formed.
9 is formed, and around the axis on the step surface of the step portion 29, for example, a wire diameter of 1.5 mm, an inner diameter of 11 mm, a total number of turns 4, and a material SU.
The optical glass material 2 fitted with the spring-shaped spring 30 wound in S304 and mounted on the barrel die 25 on the upper surface thereof
A ring-shaped pressing member 31 is stacked so as to lift upward the protruding portion 33 due to the pressing force at the time of molding 6, and the bias of the spring 30 forms a gap into which the tip portion can be inserted. ..

A step portion 32 having a small diameter is formed at a tip portion (a lower end portion shown in the figure) of the upper die 21 above the body die 25, and the tip portion is inserted into the body die 25 to form a body. It is formed so as to mold the upper surface of the optical glass material 26 placed in the mold 25. The surface of the step 32 of the upper die 25 is the body die 2
The edge portion of the upper surface of 5 abuts and constitutes a regulation surface of the thickness dimension of the optical element to be molded.

The molding method of this embodiment having the above-mentioned structure will be described. First, the optical glass material (preform) 26 formed on both sides of the flat surface is placed in the recess 28 of the body mold 25,
After heating to a temperature at which the optical glass material 26 is softened by the heating means, the upper mold 21 and the lower mold 2 are moved by the transfer arm.
When the upper die of the upper die 21 is brought into contact with the step portion 32 of the upper die 21, the lower die 22 is moved up and the lower die 22 is moved upward to raise the barrel die 25 through the stopper 24. Lower mold 22
Will stop operating. Optical glass material 2 by pressing at this time
The protruding portion 33 of No. 6 is pressed via the pressing member 31 by the bias of the spring 30.

When the optical element is molded by the above-mentioned molding method, the wall thickness of the optical element matches the variation in the height of the barrel die 25, and if this height is within the standard of the wall thickness of the optical element. , The variations in the thickness of the optical element were all within the standard. Also, no sink mark was generated and the transferability was good.

[0016]

According to the present invention having the above structure and method,
Since a gap is provided between the die and the body die, the die is stopped by the stopper at a position where the optical element has a desired thickness, and the material leached at the time of pressing is pressed into the gap. In addition, it is possible to reliably prevent the shrinkage of the optical glass material and the occurrence of sink marks, and it is possible to obtain an accurate thickness of the optical element and a high transfer accuracy, and a simple configuration and method. Since the cost is good and the precision is always constant, the optical element with good quality can be manufactured with high productivity.

[Brief description of drawings]

FIG. 1 is a first example of a method for molding an optical element according to the present invention.
FIG. 6 is a cross-sectional view from the front showing the main part of the molding apparatus used for the above.

FIG. 2 is a second example relating to the method for molding an optical element of the present invention.
FIG. 6 is a cross-sectional view from the front showing the main part of the molding apparatus used for the above.

[Explanation of symbols]

 1, 21 Upper mold 2,22 Lower mold 3,24 Stopper 4,25 Body 5,31 Pressing member 6,26 Optical glass material 7,33 Extrusion part 8 Heater 10,15,23,27,29 , 32 Steps 11, 28 Recesses 12, 13 Holes 14 Connection member 16 Overhanging opening 30 Spring

Claims (1)

[Claims] 1. An optical glass material placed on a barrel die is heated to a predetermined temperature and conveyed between an upper die and a lower die for press molding. In a method for forming an optical element in which the pressurization is stopped at a position having a desired thickness dimension, in the protruding portion of the optical glass material by pressing provided between the barrel mold and the mold, A method for molding an optical element, characterized in that the optical glass material that has leached out is pressed at the same time when the mold is stopped.