JPH0710555A - Method for molding optical element - Google Patents

Abstract

PURPOSE:To provide the method for molding the optical element capable of molding an irregular shaped lens, such as square lens, with which centering accuracy is hardly obtainable, by using molds which are extremely simple in structure and are easily producible with a high accuracy at a low cost. CONSTITUTION:The molds having an initial preform placing step part 3 and a heated preform placing step part 4 formed to the outside shape of the lens on the inner flank 2 of a barrel type carrier 1 are used. An optical glass blank material 6 is placed on the initial preform placing step part 3 and an optical glass blank material 6' softened by heating is dropped from the initial preform placing step part 3 to the heated preform placing step part 4 and thereafter, the blank materials are pressed by the upper and lower molds 7, 8.

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 in which a material for an optical element in a moldable state is pressure-molded in a molding die.

[0002]

2. Description of the Related Art Conventionally, a square lens has been used as a finder lens of a camera. According to the prismatic lens,
Less space is wasted than a round lens,
This is because it is often advantageous in terms of downsizing.

However, a square lens is manufactured by a conventional general optical element molding method, that is, a method in which a molding material such as glass is ground with a diamond grindstone or the like, and then polished with cerium oxide or the like to perform centering. Requires a very advanced technology, unlike a round lens,
It was very difficult to obtain high centering accuracy.

Therefore, a molding method has been attracting attention, in which a prismatic lens is simply and productively produced by inserting and arranging an optical element molding material in a pair of molding dies and pressing the material. In this method, as disclosed in, for example, Japanese Patent Laid-Open No. 60-235728, an optical element is pressure-molded using a rectangular lower die. In this way, if molding is performed using a square-shaped centering mold that has been centered in advance, there is no need to perform the centering process again after molding, and the centering accuracy of the rectangular lens to be molded is high according to the mold. Is obtained.

[0005]

However, in the molding method of the above publication, since the processing of the molding die is extremely difficult, the manufacturing cost of the molding die becomes very high, and the manufacturing cost of the rectangular lens increases. There was a point.

Further, even if such an expensive molding die is manufactured, only one type of lens can be molded from a pair of molds, which is not suitable for small-lot production of various types.

The present invention has been made in view of the above problems, and by using a molding die having an extremely simple structure and easy to manufacture, it is possible to obtain a highly accurate shape lens such as a prismatic lens with high accuracy. It is an object of the present invention to provide a method of molding an optical element that can be molded at low cost.

[0008]

In order to achieve the above object, in the method of molding an optical element according to the present invention, a heating mold formed on the inner side surface of the barrel-shaped carrier has an initial preform mounting step and a lens outer shape. Using a mold having a reform mounting step, the optical glass material is placed on the initial preform mounting step, the optical glass material is heated and softened, from the initial preform mounting step The heating preform was dropped on the stepped portion and then pressed by the upper and lower molding dies.

[0009]

In the optical element molding method of the present invention having the above-mentioned structure, the optical glass element mounted on the initial preform mounting step portion becomes spherical due to surface tension when heated and softened, and the outer diameter becomes small. It drops by its own weight onto the preform mounting step. After that, when the upper and lower molds are pressed, the shapes of the upper and lower molds are transferred to the optical surfaces on both surfaces of the lens, and the shape of the inner side surface of the heating preform mounting step portion becomes the outer shape of the molded lens as it is.

An embodiment of a method for molding an optical element according to the present invention will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

[0011]

First Embodiment First, a first embodiment of the present invention will be described. Figure 1
FIG. 3A is a vertical sectional view (a) and a plan view (b) showing a barrel-shaped carrier used in a method for molding an optical element according to the present invention,
2A to 2D are process drawings for explaining a method of molding an optical element. As shown in the drawing, an initial preform mounting step 3 for mounting a preform (optical glass material) before heating is formed on the inner side surface 2 of the barrel-shaped carrier 1, and the initial preform mounting step 3 is formed. Immediately below the mounting step portion 3, a heating preform mounting step portion 4 having the same shape as the outer shape of the molded product (square lens) is formed.

In order to mold a prismatic lens according to this embodiment, first, as shown in FIG. 2A, the preform 6 before heating is placed on the initial preform placing step 3. This preform 6 is weighed in the same volume as the finished product of the rectangular lens. Next, the barrel type carrier 1 is heated in a heating furnace (not shown). When the preform 6 is heated above the transition point, it is softened, and the preform 6 becomes spherical due to the surface tension and the sag of its own weight, and the outer shape becomes smaller. The preform 6'having a smaller outer shape as described above falls from the initial preform mounting step portion 3 and is received by the heating preform mounting step portion 4 immediately thereunder (see FIG. 2B). After that, Figure 2
As shown in (c), when the upper mold 7 and the lower mold 8 are press-molded, the surface shapes of the upper and lower molds 7 and 8 are transferred as the optical surfaces of both sides of the square lens 9, and the heating preform mounting step portion 4 is formed. The prismatic shape of the inner surface 2 becomes the outer shape of the lens 9 as it is. Reference numeral 5 is a through hole opened on the bottom surface of the barrel carrier 1 so that the lower mold 8 can pass through.

As described above, according to the present embodiment, the optical surfaces are formed by the upper and lower molding dies and the lens outer shape is formed by the heating preform mounting step independently. It is possible to use upper and lower molds, and it suffices to replace the barrel carrier according to the outer shape of the lens.

[0014]

Second Embodiment Next, a second embodiment of the present invention will be described. Figure 3
3A is a vertical sectional view (a) and a plan view (b) showing a barrel type carrier used in Example 2. FIG. As shown, in this embodiment, the inclined portion 10 is provided between the initial preform mounting step 3 and the heating preform mounting step 4 of the barrel type carrier 1. By doing so, the heated preform 6'slowly drops onto the heated preform mounting step portion 4, so that the volume of the preform protruding from the through hole 5 of the barrel carrier 1 can be reduced. Therefore, when molding a concave lens as shown in FIG. 2C, the deformation amount of the preform can be small.

[0015]

Third Embodiment Next, a third embodiment of the present invention will be described. Figure 4
(A) is a vertical cross-sectional view showing a barrel-shaped carrier used in Example 3. As shown, in this embodiment, the barrel-shaped carrier 1 has a two-part structure. That is, the outer mold 11
Since the inner mold 12 and the inner mold 12 are detachable from each other, the dimensions other than the connecting portion between the two can be freely changed in design.
Therefore, the inner mold 12 having various shapes, dimensions, and materials can be prepared in advance according to the shape, thickness, optical surface diameter, and glass material of the lens to be molded (FIGS. 4B and 4C). reference). Further, the outer mold 11 and the inner mold 12 may be made of different materials. As described above, in this embodiment, since the barrel-shaped carrier 1 can be used properly only by changing the inner mold 12, it is possible to cope with small-lot production of various types at low cost.

The present invention is not limited to the above embodiment, but can be applied to lenses having a desired shape such as an ellipse and a triangle, in addition to the prismatic lens.

[0017]

As described above, according to the present invention, the heating preform placing step portion is used by using the barrel type carrier having the initial preform placing step portion and the heating preform placing step portion. Since the outer shape of the lens is molded in the shape of, and the optical surface of the lens is molded by the upper and lower molding dies, it is a molding die with an extremely simple structure, but a square lens accurately centered at low cost. It can be molded. Further, even for lenses having different outer shapes, the same upper and lower molding dies can be used as long as the optical surface shapes are the same, and only the barrel-shaped carrier needs to be exchanged, which is particularly suitable for small-lot production of various types. .

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a barrel-shaped carrier used in a method of molding an optical element according to the present invention.

FIG. 2 is a process diagram illustrating a method for molding an optical element of the present invention.

FIG. 3 is a vertical sectional view showing a barrel type carrier used in Example 2;

FIG. 4 is a vertical sectional view showing a barrel type carrier used in Example 3;

[Explanation of symbols]

 1 Body Carrier 2 Inner Side Surface 3 Initial Preform Placement Step 4 Heating Preform Placement Step 5 Through Hole 6 Preform (Before Heating) 6'Preform (After Heating) 7 Upper Mold 8 Lower Mold 9 Square Lens 10 inclined part 11 outer mold 12 inner mold

Claims (1)

[Claims] 1. A molding die having an initial preform mounting step and a heating preform mounting step formed in an outer shape of a lens on an inner surface of a barrel-shaped carrier is used to form an optical glass material into the initial preform. The optical glass material is placed on a reform mounting step, softened by heating, dropped from the initial preform mounting step to the heating preform mounting step, and then pressed by an upper and lower molding die. A method for molding an optical element, comprising: