JPH07138035A - Forming equipment of optical element - Google Patents

Abstract

PURPOSE:To obtain an optical element without forming a crack, etc., by forming a surplus portion not used for the optical element to concentrate a stress into the surplus portion, in a press forming of a heated glass raw material. CONSTITUTION:In surfaces of a dies 21a and 22a of the upper die 21 and the lower die 22 respectively in the die 20, effective diameter forming parts 21aE and 22aE, and flange forming parts 21aF and 22aF together with surplus forming parts 21aB and 21aB located at the outside of the flange forming parts 21aF and 22aF, are continuously constructed, and protrusions 25 comprising stress concentrating parts are formed in the surplus forming parts 21aB and 22aB. With the above construction, a surplus area 24c is formed in addition to a effective diameter are 24a and a flange area 24b in a lens forming body 24 formed by the die 20, and in the surplus area 24c concave parts 26 with a shape corresponding to the protrusions 25 are formed. In a cooling process after the forming, a residual stress concentrates most at the concave parts 26 in the surplus area 24c, which have larger shape change than that of a shape changing portion from effective are 24a to the flange area 24b. The surplus area 24c is cut off to produce a lens 30.

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 apparatus for press-molding an optical element such as a lens under heating with a pressing means.

[0002]

2. Description of the Related Art In recent years, as an optical element, for example, a method has been used in which a lens is manufactured by press molding using a pressing means. FIG. 4 shows a schematic configuration of this type of lens forming apparatus. In the figure, reference numeral 1 denotes a molding die, and this molding die 1 is composed of an upper die 2, a lower die 3 and a body die 4. The upper mold 2 and the lower mold 3 each have a curved mold surface 2 corresponding to the shape of the lens to be molded.
The barrel mold 4 is provided with a and 3a and is for guiding the upper and lower molds 2 and 3 during press molding. Mold surface 3 of lower mold 3
The glass material is set on a, the body mold 4 and the upper mold 2 are incorporated, and the entire molding die 1 is heated so that the glass material is heated to be melted or softened. The lower mold 3 is placed on the die 5, and the upper mold 2
Pressing is performed by the pressing member 6 to perform press molding.

The lens is molded as described above,
As shown by reference numeral 10 in FIG. 5, a positioning ring 12 screwed to the inner surface of the lens barrel 11 on which the lens 10 is mounted, is provided on the outer peripheral portion of the effective diameter region 10a that exhibits the lens function.
And a flange region 10b for fixing the lens 10 to the lens barrel 11 is formed. To mold the lens 10 having such a shape,
As shown in FIG. 6, the mold surfaces 2a and 3a of the upper and lower molds 2 and 3 are formed.
By including the effective diameter forming portions 2aE and 3aE and the flange area forming portions 2aF and 3aF, the effective diameter area 10a and the flange area 10b are integrally formed.

[0004]

By the way, the lens 10
In the case of press-molding with a pressing means, a step of cooling after the molding is necessary because the glass material is heated to melt or soften. When the glass material is heated, it thermally expands, and when it cools, it contracts, causing thermal stress. Of course, by gradually cooling, residual stress is prevented as much as possible, but from the viewpoint of production efficiency and the like, it is not possible to cool over a very long time.

Regardless of when the molded lens has a substantially continuous surface, the lens 10 in which the flange region 10b is connected to the effective diameter region 10a has the effective diameter region 1
Since 0a has a curved surface shape and the flange portion 10b has a substantially flat shape, the transition portion from the effective diameter region 10a to the flange portion 10b is a shape change portion. For this reason, the residual stress during cooling is concentrated on this shape change portion, and there is a possibility that a crack C is generated at this portion as shown in FIG. If the crack C enters the effective diameter region 10a, it cannot be used as a lens product. When the crack C faces the flange portion 10b side,
The function as a lens does not cause a big problem, but the strength of the lens is lowered and the lens cannot be used as a product. Therefore, in press-molding the lens by the pressing means, there is a problem that it takes a lot of time for cooling due to the problem that cracks are generated at the time of cooling, and when the cooling time is shortened, a product due to cracks is generated. However, there is a drawback in that the yield of

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and its purpose is to:
The purpose of the present invention is to reliably prevent a crack from being generated in a portion used as an optical element constituent portion.

[0007]

In order to achieve the above-mentioned object, the present invention provides an element forming portion for forming an element constituting area including at least an effective diameter area on the mold surfaces of upper and lower molds. A margin forming portion for forming a margin area to be cut and removed after molding is provided outside the element forming portion, and a stress concentration portion for forming a portion for concentrating residual stress acting on cooling at the position of the margin forming portion. The feature is that the structure is provided.

[0008]

In the first place, if the glass material is heated and pressure-molded and then cooled in the molding die, residual stress is generated, so that the generation of cracks cannot be completely prevented. Such cracks are generated in the shape change portion, and as described above, in the lens as one of the optical elements, when the flange area is formed outside the effective diameter area, the flange is removed from the effective diameter area. The stress concentrates on the shape-changed portion to the region, and cracks occur at the relevant portion. However, even if a crack is generated during cooling, it does not cause any particular problem unless the crack is generated in the lens as the final product. Further, after the lens is press-molded by the pressing means, the surface is polished and finished, and the outer peripheral edge portion is subjected to the end treatment, so that the final product as a lens is obtained.

In consideration of the above points, in the present invention,
A blank portion having a predetermined width is formed outside an optical element constituting portion of an optical element such as a lens which is a final product, and a crack generated during cooling is formed in this blank portion. Thus, for example, even if there is a shape change portion from the effective diameter area toward the flange area, if a further shape change portion is formed in the blank portion, residual stress concentrates on this larger shape change portion. Thus, cracks may occur in this portion, but cracks will not occur in the shape changing portion in the optical element constituting portion. Moreover, this blank portion is cut and removed when the optical element is formed as the final product. Therefore, even if a crack is generated in this portion, no problem will occur.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a main configuration of a lens molding apparatus as an optical element. This molding device, like the above-mentioned conventional one, by heating the glass material,
The lens is melted or softened, and the lens is press-molded by pressing. In the figure, 20 is a forming die, 21 is an upper die, 22 is a lower die, and 23 is a body die. The upper die 21 and the lower die 22 are incorporated in the body die 23, and the upper die 2
A glass material is set between the mold surface 21a of No. 1 and the mold surface 22a of the lower mold 22, and pressure is applied from above and below to mold surface 2
The point that a lens having a shape along 1a and 22a is molded is the same as that of the above-described conventional art. Further, the effective diameter forming portions 21aE and 22aE and the flange forming portions 21aF and 2a are formed on the mold surfaces 21a and 22a.
A lens forming portion forming a lens forming portion composed of 2aF is formed, and as a result, the lens forming body 24 molded by the molding die 20 has a shape having an effective diameter region 24a and a flange region 24b.

By the way, in this molding die 20, the die surface 21
a, 22a flange forming portions 21aF, 22aF
Margin forming portions 21aB and 22aB are continuously provided on the outer side of. The margin forming portions 21aB and 22aB are obtained by extending the flange forming portions 21aF and 22aF as they are in the outer peripheral direction. Therefore, in addition to the effective diameter area 24a and the flange area 24b, which are lens components, the lens forming body 24 actually formed by the molding die 20 has a blank area 24.
c is formed. However, this blank area 24c is outside the flange area 24b and is cut and removed after molding.

The mold surfaces 21a and 22a are provided with protrusions 25 which form stress concentration portions on the margin forming portions 21aB and 22aB. The protrusions 25 are formed in an annular shape, or a large number of protrusions 25 are formed in the circumferential direction. In any case, the projection 25 has an acute angle as shown by the angle θ ₁ , and at least the effective diameter forming portions 21aE, 22 are formed.
It has an angle larger than the angle θ ₂ of the shape changing portion from the aE to the flange forming portions 21aF and 22aF, and thus the projection 25 is formed so as to be the largest shape changing portion in the entire mold surfaces 21a and 22a. This way the protrusion 2
By providing 5, the concave portion 26 having a shape corresponding to the protrusion 25 is formed in the blank area 24c of the lens forming body 24.

This embodiment is constructed as described above. Next, a method of molding a lens using this molding die 20 will be described. First, a glass material is set on the mold surface 22a of the lower mold 22 without assembling the upper mold 21 of the molding mold 20, and the molding mold 20 including the lower mold 22, the body mold 23, and the upper mold 21 is assembled. By heating the entire molding die 20 by the heating unit, the glass material is heated to the molding temperature and a predetermined pressing force is applied between the upper die 21 and the lower die 22 to perform press molding. This press-molded state is shown in FIG. Molded in this way, the lens forming body 24
When the lens is formed, the lens forming body 24 is gradually cooled while being incorporated in the molding die 20. Then, when the lens forming body 24 is solidified and is lowered to a temperature at which it can be taken out from the molding die 20, the molding die 20 is disassembled and the lens forming body 24 is taken out.

By the way, in the cooling step, the glass in a molten state is solidified while being heat-contracted so as to flow from the end side toward the center, as shown by the arrow in FIG. If there is no shape change portion, the residual stress generated at this time is dispersed over almost the entire area, but if there is a shape change portion, the residual stress is concentrated on that portion. Therefore, in the lens forming body 24, the shape change portion cannot be eliminated because the flat flange region 24b is formed on the outer peripheral side of the curved effective diameter region 24a. However, the protrusion 25 having a shape change larger than that of the shape change portion of this portion is
It is formed in the margin forming portions 21aB and 22aB of a.
Therefore, in the blank area 24c of the lens forming body 24, the concave portion 26 having a shape change larger than that of the shape changing portion from the effective area 24a to the flange area 24b is formed. 26, even if the crack C occurs during cooling as shown in FIG. 2, the crack C occurs in the blank area 24c in which the recess 26 is formed.

On the other hand, from the effective area 24a to the flange area 2
Almost no stress concentrates on the shape change part to 4b,
At least stress concentration to the extent that cracks occur will not occur. Therefore, a lens having an excellent surface shape is formed. Further, the prevention of the stress concentration at this portion also prevents the distortion of the internal tissue, and the dispersion of the stress particularly in the peripheral portion of the effective region 24a is effective for suppressing the aberration and the like for the lens. The performance of is also improved.

As described above, depending on the molding die 20, the effective area 24a, the flange area 24b, and the blank area 24c.
Although the lens forming body 24 is formed, the lens forming body 24 is not the final product as it is. Of course, the final polishing finish of the effective area 24a is performed, but at the same time, the end portion treatment of the flange area 24b is also performed. At that time, as shown by a dotted line in FIG. 2, the blank area 24c is cut and removed to leave the effective area 24a and the flange area 24b, which are lens components, to form a lens as a final product. . Therefore, even if the crack C is generated in the molding step, the lens 30 as the final product has an excellent surface shape without cracks as shown in FIG. 3, and the product yield is improved. .

In the above-mentioned embodiment, the optical element is configured to mold a lens, but other than this, the invention is also applied to molding an optical element such as a prism or a spherical mirror. it can. Further, when it is not necessary to form the flange region 24b outside the effective region 24a as the lens component, the blank region may be formed directly outside the effective region. Further, although the protrusion 25 is used as the stress concentration portion, the point is that the maximum shape change portion may be formed in the blank area, and it is possible to form the shape change portion on both the upper and lower molds 21 and 22. It is also possible to provide only on one side.

[0018]

As described above, according to the present invention, in molding an optical element, a molding die is provided on the outside of an element forming portion for forming an element constituting area including an effective diameter area of the optical element. Since a margin forming portion for forming a margin area to be cut and removed after molding is provided, and a stress concentration portion for forming a portion for concentrating residual stress acting at the time of cooling is provided at the position of the margin forming portion. Even if cracks due to residual stress occur in the cooling step after molding, since the cracks occur in the marginal area to be finally cut and removed, it is possible to manufacture an optical element having an excellent surface shape with high yield. Produce the effect of.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a state in which a lens is press-molded by a lens molding device according to an embodiment of the present invention.

FIG. 2 is an external view of the lens taken out from the molding die.

FIG. 3 is an external view of a lens product.

FIG. 4 is a schematic configuration diagram of a lens molding device in the related art.

5 is a cross-sectional view showing a state in which a lens molded by the lens molding device of FIG. 4 is mounted on a lens barrel.

FIG. 6 is a cross-sectional view of essential parts showing a state where a lens is press-molded by the lens molding device of FIG.

FIG. 7 is an external view of a lens taken out from the lens molding device.

[Explanation of symbols]

 20 Mold 21 Upper mold 22 Lower mold 21a, 22a Mold surface 21aE, 22aE Effective diameter forming part 21aF, 22aF Flange forming part 21aB, 22aB Margin forming part 23 Body mold 24 Lens forming body 24a Effective diameter area 24b Flange area 24b Blank area 25 protrusion 26 recess 30 lens

Claims (2)

[Claims] 1. A combination of an upper die, a lower die, and a body die for press-molding a glass material in a heated state,
On the mold surfaces of the upper and lower molds, an element forming portion for forming an element constituting area including at least an effective diameter area, and a margin forming outside the element forming portion, a margin area to be cut and removed after molding is formed. An apparatus for molding an optical element, characterized in that a stress concentrating portion for forming a portion for concentrating residual stress acting at the time of cooling is provided at a position of the margin forming portion. 2. The apparatus for molding an optical element according to claim 1, wherein the stress concentrating portion is an acute-angled protrusion provided on the margin forming portion.