JPH0729777B2 - Method for forming optical element - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an optical element, such as a glass lens used in optical equipment, which is molded by a precision glass press.

2. Description of the Related Art In recent years, many attempts have been made to form optical elements such as optical lenses by one-shot molding without a polishing step. A general method is to pre-process a glass material into a certain shape, supply it between molds, heat it, and press-mold it (for example, Japanese Patent Laid-Open No. 58-84134). According to this manufacturing method,
The use of an aspherical mold has the advantage that aspherical optical elements can be mass-produced at low cost.

At that time, in order to obtain a highly accurate glass press-molded product, the glass material to be used is pre-processed into a shape similar to the shape of the optical element, and the volume of the cavity formed by the mold and barrel and the volume of the glass material are Must be matched exactly. Since the pre-processing of such a glass material is time-consuming, measures have been taken such as providing a relief for glass in a part of the mold structure (for example, JP-A-60-118642).

Hereinafter, the conventional molding method described above will be described with reference to the drawings.

FIG. 3 is a sectional view showing a state where a lens is formed by molding a glass material by a conventional method. Reference numeral 14 is a molded lens, 11 and 12 are a pair of molding dies, and 13 is a barrel mold. After heating the glass material to a temperature near the softening point, a pair of molding dies
It is supplied between 11, 12 and pressure is applied to the molding dies 11 and 12 by the pressure mechanism 15 to perform pressure molding. As shown in the figure, a gap E is provided at a portion where the body mold 13 is in contact with the upper mold 11, so that excess glass can escape, so that there is a margin for adjusting the weight of the glass material.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above method, in order to realize precise transfer of the optical surface, the inner volume of the cavity formed by the mold and the barrel die and the volume of the pre-processed glass material are Although it is not necessary to exactly match, the glass shape of the portion other than the effective diameter of the lens is not constant, and the lens cannot be fixed with the outer circumference of the lens as a reference, which causes a problem when the lens is used. Especially, in the case of an aspherical lens, the optical axis must be precisely adjusted, and this defect is more serious. Further, there is a drawback that a portion having a non-uniform shape outside the effective diameter has an unnecessary volume as a lens.

On the other hand, for the centering of the spherical lens, an efficient centering device has been used for many years and is often used for the production of polished lenses. However, a lens manufactured by precision molding of glass has one feature in that it includes an aspherical surface, and there is no simple method for centering an aspherical lens.

In view of the above problems, the present invention provides a method capable of forming an optical element having a required high precision at a low cost by simplifying weight alignment and centering of glass materials.

Means for Solving the Problems In order to solve the above problems, the method for molding an optical element of the present invention is to place a glass material in a cavity formed by a pair of molding dies and a barrel mold, and heat the glass. The optical element by pressure molding until it contacts the barrel mold, hold the optical element with the outer circumference of the optical element taken out of the mold as a reference, and then the rotation center axis of the outer circumference rotates the optical element holding part. A method is used in which an optical surface is held so as to coincide with the central axis and the outer circumference of the optical element is centered.

Function In the present invention, when the optical element is formed by glass precision molding as described above, the optical axis of the optical element is determined by the molding die and the optical axis and the rotation center axis of the outer circumference are made to coincide with each other. Center the optical element while holding it as a reference. This method has an effect that the optical axes of both surfaces of the optical element can be aligned with each other and the centering can be easily performed even when the tolerance of the weight matching of the glass material is large, even if the optical surface is an aspherical surface.

Example A method of forming a lens according to an example of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a molding state of an embodiment of the present invention, and FIG. 2 is a sectional view showing a centering state.

FIG. 1 shows a state in which the glass has just been deformed and a lens has been formed. 1 and 2 are molding dies having an optical surface to be transferred to a lens. 4 is a molded lens. Three
Is a barrel mold having an inner diameter larger than the outer diameter of the lens, and having a gap B as shown in the figure between the molding dies 1 and 2 and the barrel mold 3. The volume of the glass material is larger than the effective volume of the lens, and the excess glass protrudes outside the effective diameter of this lens, and its outer periphery is in contact with the barrel shape. The sliding surfaces of the molding die and the barrel die are positioned with a minimum required gap, and the optical axis A of the optical surface of the molding die is the rotation center axis of the barrel die 3 at the same time.
That is, the optical axis A of the molded lens 4 is the rotation center axis with respect to the outer circumference of the lens.

FIG. 2 shows how the outer circumference of the lens 4 is centered. Second
The inner diameter of the positioning jig 5 in FIG. 3A is the same as the inner diameter of the barrel die 3 in FIG. The lens 4 molded here is inserted so that the lens outer circumference matches the inner circumference of the positioning jig 5, and is held by the holding jig 6 from above and below. At this time, the central axis C of rotation of the holder 6 and the optical axis of the lens coincide with each other. Next, as shown in FIG. 2B, the holder 6 is moved upward to push the lens out of the positioning jig 5, and the holder 6 is rotated around the rotation center axis C while the grindstone 7 is moved in the direction of the arrow. The unnecessary portion 8 is scraped off by moving it in the direction of D and applying it to the outer periphery of the lens 4. If necessary, it is possible to center the effective diameter.

Although the outer periphery of the lens 4 formed in FIG. 1 is in contact with the body in a circumferential shape, in order to exert the effect of the present invention,
It is not always necessary for the entire circumference to touch. In FIG. 2, it is sufficient that there are three or more peripheral points that serve as references so that the lens can be accurately positioned by the positioning jig 5.

In this way, accurate centering of the lens can be performed with a simple jig.

EFFECTS OF THE INVENTION As described above, the present invention, when molding a precise optical element,
The glass material processing cost is reduced by eliminating the need for strict weight adjustment of the glass material, and the optical axis of the lens is aligned by centering with a simple jig, and the volume of the invalid part of the optical element is reduced. It has the effect of reducing it as much as possible. The manufacturing method of the present invention exerts a remarkable effect particularly on a lens having an aspherical optical surface.

[Brief description of drawings]

FIG. 1 is a sectional view showing a molding state of a lens in one embodiment of the present invention, FIG. 2 is a sectional view showing a centering state in one embodiment of the present invention, and FIG. 3 is a molding method in a conventional example. It is sectional drawing shown. 1,2,11,12 …… Molding die, 3,13 …… Body mold, 4,14 …… Molded lens.

Claims (2)

[Claims] 1. An optical element is formed by placing a glass material in a cavity formed by a pair of molds and a cylinder mold, heating the glass material and heating it until the glass comes into contact with the cylinder mold, and taking out from the mold. The optical element is held on the basis of the outer circumference of the optical element, and then the optical surface is held so that the rotation center axis of the outer circumference coincides with the rotation center axis of the optical element holding section. A method for forming an optical element, which comprises rotating the optical element to center the outer circumference of the optical element. 2. The optical element according to claim 1, wherein at least one surface of the optical surfaces is an aspherical surface.
Item 5. A method for forming an optical element according to item.