JPH01226745A - Glass lens formation mold - Google Patents

Abstract

PURPOSE:To obtain the lens of high accurate surface by making the thermal expansion quantity of a trunk mold in the shifting direction of the formation molds consisting of a pair of molds and the trunk mold larger than that of the lens thickness in the same direction and of the formation mold parts shifting in the trunk mold. CONSTITUTION:A lens material 6 is supplied in the formation molds consisting of a pair of molds 3, 4 and the trunk mold 5 and heated to the transformable temp. to be pressed to the end position by press heads 1, 2. Then, cooling is started in the pressed state. Just after the starting of the pressed cooling, the length L1 of the trunk mold in the shifting direction of the formation molds is same as the length L2 of the lens material 7 and the received parts of formation molds 3, 4 shifted in the trunk mold, but the thermal expansion quantity of L1 is larger than that of L2 because the thermal expansion rate of the trunk 5 is larger than that of the lens material 7. Consequently, the contraction of L1 is larger than that of L2 in the pressed cooling with the result the lens material 7 is always pressed. The lens 7 is taken out after the cooling is finished.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a glass lens mold for forming high-precision optical glass elements such as lenses and prisms used in optical equipment by an ultra-precision glass molding method. .

Background of the Invention In recent years, as a manufacturing method for high-precision optical lenses, especially aspherical glass lenses, many attempts have been made to form them by one-shot molding without using an optical polishing method and without a polishing process. One of the molding methods is to heat the glass material to a temperature at which it can be deformed, for example, to a temperature near its softening point, and then mold it using means such as pressure molding.(For example,
(Japanese Unexamined Patent Publication No. 61-21927) This method requires a mold having a highly accurate surface shape and structure.

An example of a molding method using the conventional glass lens mold described above will be described below with reference to the drawings.

FIG. 3 is a cross-sectional view showing a lens formed by molding a spherical lens material using a conventional glass lens mold. 8.9 is a part of a press head having a heating and pressing mechanism, 10.11 is a pair of molds, 12 is a barrel mold, and 13 is a molded lens. Molding the lens material into a mold 10.11
It is heated and press-formed. After the deformation is completed, the mold, body mold, and molded lens are gradually cooled, and when the temperature reaches a point where the lens can be taken out, the mold is opened and the lens is taken out.

Problems to be Solved by the Invention However, with the above-mentioned molding method in which the lens thickness is regulated by the body dimensions, there is a problem in that it is not possible to obtain an ultra-high precision lens surface shape with a shape accuracy of 0.1 μm or less. Was.

Means for Solving the Problems In order to solve the above problems, the present invention calculates the amount of thermal expansion of the mold in the sliding direction of the mold by adjusting the thickness of the lens in the sliding direction of the mold and the amount of sliding storage in the mold of the mold. This method uses means to increase the amount of thermal expansion larger than the amount of thermal expansion of the parts that are in contact with each other.

Function The present invention uses the above-mentioned means so that the mold in the sliding direction of the mold is thicker than the lens thickness in the mold sliding direction and the portion of the mold that is slidably accommodated in the mold (shrinkage occurs during the cooling process after molding). Because pressure is constantly applied to the lens material even in
A glass lens with a highly accurate surface shape can be obtained.

EXAMPLE Hereinafter, a glass lens mold according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a state immediately before pressure molding of a lens material with a glass lens mold according to an embodiment of the present invention. 1 and 2 are parts of a press head having a heating and pressing mechanism, 3.4 is a pair of molds, 5 is a mold, and 6 is a lens material. FIG. 2 is a sectional view showing the state immediately after the start of pressurized cooling in the example. 7 is a molded lens.

Ll indicates the length of the mold in the sliding direction of the mold, and L
2 indicates the current length of the lens material and the portion of the mold that is slidably housed in the mold. At this time, that is, immediately after the start of pressurized cooling, L1 and L2 are processed and configured so that they have the same length and the thickness of the lens taken out after cooling has a desired dimension. The thermal expansion coefficient of the mold is larger than that of the lens material, and the amount of thermal expansion of Ll is larger than that of L2.

Molding using the glass lens mold according to the embodiment of the present invention constructed as described above will be explained with reference to FIGS. 1 and 2. The lens material 6 supplied as shown in FIG. 1 is heated by a press head 1.20 to a temperature at which it can be deformed by some kind of heating device (not shown). When the temperature reaches a point where it can be deformed, pressurize it with the press head 1 and push it out. Then, in the state shown in FIG. 2, the next pressurized cooling step is carried out.

In this process, as mentioned above, the amount of thermal expansion of Ll is larger than that of L2, so during cooling, Ll is larger than L2.
The contraction is larger than that of 2, and pressure is constantly applied to the lens material. When the cooling process is completed, the lens is taken out by some method not shown. Since the lens material was constantly pressurized during the cooling process, the surface shape of the lens taken out after cooling was obtained with the desired high precision.

Effects of the Invention As described above, the amount of thermal expansion of the mold in the sliding direction of the glass lens mold of the present invention is determined from the lens thickness in the sliding direction of the mold and the amount of thermal expansion of the portion of the mold that is slidably accommodated in the mold. By increasing the size of the lens, a lens mold with a highly accurate surface shape becomes possible.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the state immediately before pressure molding with a glass lens mold according to an embodiment of the present invention, and Fig. 2 shows the state immediately before pressurization cooling starts with a glass lens mold according to an embodiment of the present invention. FIG. 3 is a cross-sectional view showing a state in which molding is performed using a conventional glass lens mold. l, 2... Part of a press head having a heating and pressing mechanism, 3.4... A pair of molds, 5...
・・Ta type, 6・・Lens material, 7・・・・
Molded lens, 8.9... Part of head having heating and pressing mechanism, 10.11... Pair of molds, 12... Field mold, 13・・・・・・Molded lens.

Claims (1)

[Claims] In press molding, which is composed of a pair of molds and a body die, and the lens thickness is regulated by the body dimensions in the sliding direction of the mold, the amount of thermal expansion of the body mold in the sliding direction of the mold is the same as that of the body in the sliding direction of the mold. A glass lens mold characterized by having a lens thickness greater than the amount of thermal expansion of the portion of the mold that is slidably accommodated in the body of the mold.