JPH0446021A - Press lenses and their molding methods - Google Patents

Abstract

PURPOSE:To reduce the inner strain of a lens and to obtain uniform refractive index by specifying the outer diameter and circumferential thickness of the lens after press-formation. CONSTITUTION:A molding die comprising a first recessed die 1 having the first optical surface, a second recessed die 2 having the second optical surface and a cylinder die 3 is charged with glass material 4 and heated till the viscosity of the glass material becomes 10<8> - 10<18> poise. Then the glass material is press- formed into a lens having the outer diameter smaller than the diameter of curvature parts in the dies 1 and 2 and the circumferential thickness of 0.3 - 1.1mm. Then the lens is cooled to the glass transition point, released from the die and subjected to centering and edging.

Description

[Detailed Description of the Invention] Industrial Application Field of the Invention This invention relates to a press lens produced by reheat press molding of a high-precision optical glass element (for example, a prism, etc.) and its molding method. For example, as described in Japanese Unexamined Patent Publication No. 57-76512, optical elements are moving toward aspherical surfaces, which can simultaneously simplify the lens structure of optical equipment and reduce the weight of the lens part. Among these, as a method of manufacturing high-precision glass products at a lower cost, Japanese Patent Application Laid-Open No. 58-84134 proposes a method of obtaining high-precision optical glass elements by shortening the time required for the pressurization cycle. The gist of this is to use a glass preform with a shape similar to the final product, heat the mold and the glass preform, and heat the glass and mold to 101 poise or higher.

Although it has been proposed to start pressing at a temperature corresponding to a glass viscosity of 1012 poise or less, and to finish pressing at a temperature corresponding to a glass viscosity lower than 10" poise, and then take out the glass, the invention does not solve the problem. Problems to be solved In manufacturing the above-mentioned optical element, the optical performance of the optical element must be superior to that of a glass lens produced by conventional polishing methods, and very high surface accuracy and surface roughness are required.

For example, in the case of a high-precision camera lens, the surface roughness of each Newton ring must be within 0.03 μm. However, in the conventional method of molding optical elements, the molding die is Lens outer diameter DI larger than the diameter of the curvature of
For example, the corner 10 of the intersection line of the curved part 6b and the flat part 6a is transferred to the press lens 9, and this corner part transferred to the press lens 9. This tends to cause stress concentration, which causes problems such as glass cracking and internal distortion remaining in this area of the glass lens after cooling, resulting in uneven refractive index, making it impossible to obtain the desired lens performance. 9) Furthermore, the corner of the intersection line between the curved part and the flat part comes into close contact with the glass material from an early stage. Means To solve the above problems, the press lens and the molding method thereof of the present invention include: a first mold having a first optical surface; a second mold having a second optical surface; Second
The outer diameter of the lens after press molding is smaller than the diameter of the curvature portion having the first and second optical surfaces, and the lens thickness at the peripheral portion of the lens is 0.3 to 0.3.
A pressed lens that is centered after being set to 1.1 mm and its molding method.The pressed lens made in the present invention does not always have a flat part at the lens edge before and after centering, and has no curvature. have.

Function The press lens of the present invention is press-molded because the outer diameter of the lens after press molding is smaller than the diameter of the curved part of the first mold having the first optical surface and the second mold having the second optical surface. The corner of the intersection line between the first curvature part and the flat part is not transferred to the subsequent lens, and internal distortion can be made very small, even if the refractive index is kept uniform. The lens does not require annealing.On the other hand, if the lens thickness after press molding is 0.3 nm or less, it is very easy to break when taking the lens out of the mold, making it difficult to mass-produce. t,
If it exceeds tmm, it will take too much time during centering in the post-process, and it will be difficult to match the machine tact with the press molding machine, making it impossible to provide inexpensive press lenses (
However, as mentioned above, the lens thickness at the lens periphery is set to 0.
3 to 1.1 mm solves this problem, but the press lens molding method of the present invention requires a first mold having a first optical surface and a second mold having a second optical surface. 2 molds, and a barrel mold for guiding the first and second molds. This is a press lens molding method in which centering is performed after the lens thickness is set to 0.3 to 1.1 mm.It is possible to stably produce press lenses with high precision optical performance. The optical surface of the mold is heated to a glass viscosity of 10'' to 1011 poise, then pressed, cooled to the glass transition point, and then taken out. In this press lens molding method, the lens molding machine does not have a special space for exchanging air and inert gas, and it is a simplified lens molding method that does not perform vacuum evacuation. It is a machine.

Therefore, by performing the press lens molding method described above, it is possible to obtain a press lens at a very low cost.

EXAMPLE Hereinafter, an example of the press lens molding method of the present invention will be described with reference to the drawings.

FIG. 1 shows a mold for molding a press lens used in this example. 1 is a first concave mold having a first optical surface, and 2 is a second concave mold. Even if the second concave mold is equipped with an optical surface, and even if the optical surface is processed into a spherical or aspherical surface, this mold has a body mold 3 for guiding these first and second molds. The length is determined by the force determined by the lens dimensions (lens dimensions may be determined by a press cylinder (not shown). % 4 is the glass material used in this example. The shape of this glass material is particularly The shape of the mold (the radius of curvature of the first concave mold is 45 mm) is used in this example.
rL, the radius of curvature of the second concave mold is 32 mm,
The diameter of the curvature of the mold is 31°5 mm.A The shape of the pressed lens obtained using this mold as shown in Figure 2 has a radius of curvature of 45 mm on both convex surfaces.
, 32mm, diameter 30mrrK center wall thickness 7
．． The lens diameter is 1mm, and the peripheral wall thickness is 0.8mm.After centering the outer periphery, the lens diameter becomes 29mm.
The optical effective diameter of this press lens is 25.5 mm, and as shown in Figure 2, the outer diameter of the lens obtained by circle pressing is smaller than the outer diameter of the curvature. Xo If the lens outer diameter is molded larger than the above, the curved part and flat part 1
The corner of the intersection line with i 2a will be transferred and formed on the press lens, so there is a force (as mentioned above, stress concentration, stress distortion, etc. are likely to occur at this corner, causing various problems). In this example, such corners do not occur, and the conventional problems can be sufficiently solved. Inside the chamber is a press
Even though each cooling stage is arranged, the glass supply/mold assembly stage is arranged before the heating stage.
A mold disassembly/lens extraction stage is placed after the cooling stage. At the mold disassembly/lens removal stage, after removing the lens, the mold is transferred to the mold assembly stage, and the lens is further transferred to the centering stage.After centering, a press lens with the desired lens shape is removed from the lens removal port. compare A method of molding by transferring the molding die shown in FIG. 1 to each stage shown in FIG. 3 will be described below.

The pressed glass material is made of SF3. First, the glass material is preheated to 200℃, fed into a mold at room temperature, transferred to a heating stage, and heated to 480℃ (10" poise). Next, the mold was transferred to a press stage kept at a constant temperature of 480°C, and a press cylinder (not shown) was lowered to press for 60 seconds.9 The press pressure at that time was 500 kg/cm'. After opening, the glass was transferred to a cooling stage kept at a constant 400°C, and press pressure was applied again.9 The press pressure at this time was 200 kg/cm. ℃(
IQ! 3 poise), then the mold is disassembled and transferred to the lens extraction stage to take out the lens.
The lens is taken out by vacuum suction, but if the lens thickness around the lens is less than 0.2 mm, there is a problem that the lens tends to chip, so the thickness around the lens needs to be 0.3 mm or more.Then, press the lens. The lens is transferred to the centering stage and the press lens with a diameter of 30 mm is centered to a diameter of 29 mm.The centering time at this time is 50 seconds.9 Normal centering time varies depending on the centering width. If the lens thickness at the part is thicker than 1.1mm, the centering time will exceed 60 seconds.
Because the machine tact with the press molding equipment does not match, the centering cost increases, and we are unable to supply inexpensive press lenses. This is very important in the present invention.By using the above press lens molding method, we were able to obtain an extremely good press lens with a wavefront aberration RMS = 0.028λ.Furthermore, the residual distortion was also 10 nm.
/cm, there is no need for annealing at all.9 Effects of the InventionAs is clear from the above explanation, the press lens of the present invention and its molding method (the first mold having the first optical surface and the first mold having the first optical surface) , a second mold having a second optical surface; and a second mold having a second optical surface;
and a mold for guiding a second mold, the outer diameter of the lens after press molding is smaller than the diameter of the curved part having the first and second optical surfaces, and the lens thickness at the peripheral part of the lens is 0. 3 to 1.1 mm and then centering the press lens and its molding method. Therefore, the pressed lens manufactured according to the present invention does not require annealing (°C) even if the refractive index is kept uniform. Therefore, the industrial value of the present invention is extremely large.4

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the main parts of a molding die in an embodiment of the present invention. Figure 2 is a diagram showing the state of press molding using the molding die in Figure 1. Figure 3 is a press lens molding used in an embodiment of the present invention. Block Doctor Figure 4, which shows the configuration of the device, is a cross-sectional view of a conventional press lens and its molding die.
・Gourd body 4...Glass punch 5, 9...Press lens. Name of agent: Patent attorney Shigetaka Awano Figure 2 Bottom ■ 3i Figure JIJA placement mold 1 Figure Bushings removal O Figure

Claims (4)

[Claims] (1) In a press lens produced by press molding, the outer diameter of the lens after press molding is the diameter of a curvature portion of a first mold having a first optical surface and a second mold having a second optical surface. A pressed lens characterized by being smaller and having a lens thickness of 0.3 to 1.1 mm at the lens periphery. (2) The press lens according to claim (1), wherein centering is performed after press molding. (3) Press molding comprising a first mold having a first optical surface, a second mold having a second optical surface, and a body mold for guiding the first and second molds. In the method of A press lens molding method characterized by performing the following steps. (4) Claim (3) characterized in that the diameter of the curvature portion having the first and second optical surfaces is larger than the outer diameter of the desired lens.
The method for forming the press lens described.