JP2000117603A - Manufacture of optical lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deformation or breakage of a lens in a heat treatment process after the working process of the optical lens. SOLUTION: This manufacture of an optical lens has: a lens surface polishing process for polishing the lens surface 4 of a workpiece 1, an centering machining process for grinding the outer peripheral surface 2 of the workpiece 1 to a predetermined diameter with the optical axis of the polished surface 4 as the center, and an outer peripheral surface polishing process for polishing the surface 2 of the workpiece 1 after the centering machining process to reduce the surface roughness of the surface 2 than after the centering machining process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an optical lens, and more particularly to a method suitable for manufacturing an optical lens made of a single crystal material.

[0002]

2. Description of the Related Art In a method of manufacturing an optical element such as a lens used in an optical system, a finishing process such as grinding and polishing is separately performed on each side, and after a lens surface processing step of finishing both opposing surfaces as a predetermined lens surface, In order to eliminate the eccentricity of the optical axis from the outer diameter, a centering process of grinding to a desired outer diameter around the optical axis is performed. After the centering step, a step of heat-treating the lens to be processed is performed as necessary.

Further, in order to reduce the processing time during mass production, Japanese Patent Publication No. 6-35101 discloses an apparatus and a processing method for three-surface simultaneous processing. In this machining method, as shown in FIG. 4, the workpiece 1a is sandwiched between the machining tool surfaces of two machining tools 32a and 32b, and the upper surface of the workpiece 1a is polished with the tool surface of the machining tool 32a. At the same time, the lower surface of the workpiece 1a is polished with the tool surface of the processing tool 32b. Further, a roller 31 is in contact with the peripheral wall surface of the workpiece 1a, and the workpiece 1a is rotated by the rotation of the roller 31. Also, on the peripheral wall surface of the workpiece 1a,
The centering rotary grindstone 30 comes into contact with it and performs centering.

In the method described in Japanese Patent Publication No. 6-35101, for example, an electrodeposited diamond grindstone of about # 200 to # 800 is used as the rotary grindstone 30 for centering.

[0005]

The lens manufactured by the above-mentioned conventional manufacturing method may be deformed in the heat treatment step,
It was sometimes damaged. In particular, when the lens material is a crystal such as fluorite, in the heat treatment step,
A phenomenon that the lens is broken often occurs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing an optical lens capable of preventing deformation and breakage of the lens in a heat treatment step after the processing step of the optical lens.

[0007]

According to the present invention, there is provided the following method for manufacturing an optical lens.

That is, a lens surface polishing step of polishing the lens surface of the workpiece, and a centering step of grinding the outer peripheral surface of the workpiece to a predetermined diameter centered on the optical axis of the polished lens surface. And a heat treatment step of heat-treating the workpiece, after the centering step and before the heat treatment step, polishing the outer peripheral surface of the workpiece, and surface roughness of the outer peripheral surface And an outer peripheral surface polishing step of making the outer diameter smaller than after the centering step.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The inventors have noticed that cracking and deformation of an optical lens during a conventional heat treatment process are caused by stress due to roughness of the outer peripheral wall surface of the lens. That is,
While the upper and lower surfaces of the lens are mirror-finished by polishing, the lens peripheral wall surface (side surface of the outer periphery)
Is processed only with a grindstone or the like, so the surface roughness of the peripheral wall surface of the lens is large and processing distortion is present. For this reason, it is considered that cracks and deformation of the lens occur due to the temperature distribution in the heat treatment step. In particular, a lens processed from a single crystal material such as a fluorite lens has a surface that is easily cleaved along the axial direction of the crystal even if the average roughness of the peripheral wall surface 2 is about 1 μm. Depth 3 in the direction in which the cleavage plane appears
Chipping of about μm often occurs. Since processing strain is particularly concentrated on the chipped portion, the lens is broken from the chipped portion in the heat treatment step.

Therefore, in the present invention, the peripheral wall surface 2 of the optical lens is polished to remove a layer having a rough surface roughness (deformed layer) on the peripheral wall surface, and is processed into a mirror surface. As a result, processing strain can be released, and damage caused by temperature distribution of the lens in the heat treatment step can be prevented.

Hereinafter, as one embodiment of the present invention, a method of manufacturing a fluorite lens made of fluorite containing fluoride as a main component will be described.

First, as in the prior art, the lens surface 4 is ground and polished into a desired shape to finish it into a mirror surface, and the outer peripheral wall surface (peripheral wall surface 2) is ground and centered. After that, a heat treatment step is performed. In the present embodiment, after the centering process and before the heat treatment step, a step of polishing the peripheral wall surface 2 of the lens is performed. Remove and mirror.

Hereinafter, a method of polishing the peripheral wall will be specifically described in detail with reference to the drawings.

FIG. 1 shows a polishing method when the peripheral wall surface 2 of the lens (workpiece 1) is a cylinder centered on the optical axis of the lens.
This will be described with reference to FIG. The workpiece 1 is mounted on an attachment plate 3 having the same diameter as or less than the same diameter as the workpiece 1. As a mounting method, a method such as an adhesive method or a suction method is used. The pasting plate 3
Is mounted on the work shaft 5 having the height adjusting mechanism 7.
The work shaft 5 transmits the rotation driving force of the rotation drive unit 6 to the sticking plate 3. Thereby, the pasting plate 3 rotates, and the workpiece 1 rotates. In the present embodiment, the rotation speed of the workpiece 1 is set to about 1 to 100 rpm.

A polishing liquid 18 is supplied to the peripheral wall surface 2 of the workpiece 1 which rotates, and the polishing polisher 10 is pressed while rotating. The rotation speed of the polishing polisher 10 is 1 to 100 r.
pm. As a result, the peripheral wall surface 2 is polished, and a roughened layer on the surface of the peripheral wall surface 2 is removed. As the material of the polishing polisher 10, if the workpiece 1 is a fluorite lens, first, a hard polisher whose main component is an epoxy resin is used. After rough polishing with the polishing polisher 10 made of epoxy resin to process the surface roughness of the peripheral wall surface 2 to about 2 nm, the polishing polisher 10 is replaced with a foamed polyurethane or a soft suede-like polisher, and finish polishing is performed. If the surface roughness of the peripheral wall surface 2 is smoother than that after the centering process by the final polishing, the effect of reducing the processing distortion can be obtained. However, it is preferable that the polishing is performed until the surface roughness becomes a mirror surface of 1 nm or less. It is desirable to do. It is also desirable to remove scratches such as polishing scratches as much as possible.

In the rough polishing step using the hard polishing polisher 10, as the polishing liquid 18, a mixed liquid obtained by mixing diamond abrasive grains (particle diameter: about 2 μm to 0.5 μm) with water or the like, or cerium oxide abrasive grains ( Slurry-like polishing liquid mainly composed of particles having a particle diameter of about 1.5 μm to 0.1 μm, and particles mainly composed of zirconium oxide (particle diameter of 1.0 μm to 0.1 μm)
m) is mixed with water or the like. In the final polishing step, colloidal silica (particle size: 150 nm to 5 nm)
Degree).

The thickness (machining allowance) to be removed by this polishing varies depending on the material of the workpiece 1, but in the case of fluorite, it is necessary to be about 100 μm to 300 μm on one side. The thickness of the formed work-affected layer is greatly affected by the setting of the roughness of the diamond grindstone in the centering step, but the normal work-affected layer can be removed by removing the machining allowance of about 100 μm to 300 μm.

When the peripheral wall surface 2 of the lens is stepped or curved, the affected layer may reach a deeper portion. for that reason,
Increase the polishing allowance to remove all the affected layers. In particular, when the workpiece 1 is made of a single crystal material such as a fluorite lens, since there is a surface that is easily cleaved, a deeply altered layer depending on the crystal direction is confirmed. Therefore, it is necessary to determine the thickness to be removed in consideration of the specific properties of the material.

The configuration of the polishing tool 15 to which the polishing polisher 10 is attached will be briefly described. In the polishing tool 15 shown in FIG. 1, the polishing polisher 10 is mounted on the attaching tool 12. A pressure cylinder 11 having a pressure mechanism 13 is attached to the attaching tool 12. Pressure mechanism 13
Uses a voice coil motor that is electrically controlled with spring pressure and air pressure. The axial direction of the pressure cylinder 11 is
It is arranged so as to coincide with the normal direction of the peripheral wall surface 2 (the direction orthogonal to the central axis of the machining axis 5). The attaching tool 12 is driven to rotate by a rotation power unit 14. The pressure cylinder 11 is mounted on a tilt adjusting mechanism 16, and the tilt adjusting mechanism 16 is mounted on a Z axis 9 whose height can be adjusted. The Z axis 9 is attached to the slide mechanism 17 and slides along the slide axis 8. The axial direction of the slide shaft 8 is parallel to the normal direction of the peripheral wall surface 2 (the direction orthogonal to the center axis of the machining shaft 5). The slide mechanism 17 is
It is slidable by about 50 to 200 mm, so that it is possible to cope with workpieces 1 having different diameters.

In the polishing apparatus shown in FIG.
Although the polishing polisher 10 and its rotation pressing mechanism are arranged only at the locations, the polishing efficiency of the peripheral wall surface 2 can be improved by arranging these at a plurality of locations and simultaneously polishing at the plurality of locations. is there.

When the workpiece 1 has a flat pressing portion 19 as shown in FIG. 2, the polishing polisher 110 having the same diameter as or larger than the workpiece 1 is pressed against the flat pressing portion 19. Swinging and rotating movements. Therefore, the polishing tool to which the polishing polisher 110 is attached is provided with the swing mechanism 20, the rotation mechanism 21, and the pressure mechanism 22. As the pressure mechanism 22, a voice coil motor or the like that electrically controls spring pressure, air pressure, weight pressure, and the like is used.

When there is a portion 120 having an irregular angle on the peripheral wall surface of the workpiece 1, the attaching tool 12 is formed into a shape along the portion 120 having the irregular angle, or the inclination mechanism 16 is adjusted by adjusting the tilt mechanism 16. Polishing is performed by adjusting the polisher 10 along the irregular shape angle.

For the processing of the chamfered portion 28 as shown in FIG. 3, an abrasion tool 12 and a polishing polisher 10 of FIG.
The universal joint 26 is inserted between the attaching tool 12 and the pressure cylinder 11 and pressed. At the same time, the tilting mechanism 16 can be electrically controlled to cause the sticking tool 12 to swing.

As described above, in the present embodiment, after polishing and centering of the lens surface in the optical lens manufacturing process, the peripheral wall surface 2 is polished to reduce the surface roughness. Therefore, the processing distortion of the peripheral wall surface 2 is reduced. Therefore, in the heat treatment process after the polishing process of the peripheral wall surface 2, even if a temperature distribution occurs in the fluorite lens as the workpiece 1, the peripheral wall surface 2 has no stress concentration portion due to processing strain. Can uniformly transmit the thermal stress applied to the inside of the lens. Thereby, damage due to temperature distribution can be prevented, and heat treatment can be easily performed. Therefore, the fluorite lens which is the workpiece 1 can significantly reduce the time required for adjusting the temperature difference after the heat treatment to room temperature,
The overall work time in the production line process can be reduced. Moreover, since the workpiece 1 can be prevented from being cracked or deformed, the yield can be improved and the manufacturing cost can be reduced.

[0025]

According to the present invention, it is possible to provide a method of manufacturing an optical lens capable of preventing deformation and breakage of the lens in a heat treatment step after the processing step of the optical lens.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a method of polishing a peripheral wall surface in a method of manufacturing a fluorite lens according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a polishing method of a peripheral wall surface when there is a flat pressing portion in the method of manufacturing a fluorite lens according to one embodiment of the present invention.

FIG. 3 is an enlarged explanatory view showing a method of polishing a chamfered portion of the lens in the method of manufacturing a fluorite lens according to one embodiment of the present invention.

FIG. 4 is an explanatory view showing a conventional method of manufacturing a lens, in which both-side polishing and centering of a lens surface are simultaneously performed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Workpiece, 1a ... Workpiece, 2 ... Peripheral wall surface, 3 ... Pasting plate, 4 ... Workpiece surface, 5 ...
Work axis, 6 ... Rotation drive unit, 7 ... Height adjustment mechanism unit, 8 ... Slide axis, 9 ... Z axis, 10 ... Polishing polisher, 11 ... Pressure cylinder, 12 ...
Sticking tool, 13 ... pressure mechanism part, 14 ... rotating power part, 15 ... polishing tool, 16 ... tilt mechanism, 17
..Slide mechanism part, 18 polishing liquid, 19 flat pressing part, 20 swing mechanism, 21 rotation mechanism,
22 ... pressure mechanism, 23 ... swing shaft, 24 ... swing tool, 26 ... universal joint, 28 ...
-Chamfering part, 30 ... rotating whetstone, 31 ... roller, 32a, 32b ... processing tool.

Claims (4)

[Claims] 1. A lens surface polishing step of polishing a lens surface of a workpiece, and a centering step of grinding an outer peripheral surface of the workpiece to a predetermined diameter centered on an optical axis of the polished lens surface. And a heat treatment step of heat treating the workpiece, after the centering step and before the heat treatment step,
Polishing the outer peripheral surface of the workpiece to reduce the surface roughness of the outer peripheral surface after the centering step. 2. The method of manufacturing an optical lens according to claim 1, wherein said workpiece is made of a crystal. 3. The method of manufacturing an optical lens according to claim 2, wherein the workpiece is made of fluorite, and in the outer peripheral surface polishing step, the outer peripheral surface has a surface roughness of 1 nm or less. A method for producing an optical lens, comprising: 4. The method of manufacturing an optical lens according to claim 1, wherein in the outer peripheral surface polishing step, polishing is also performed on a boundary portion between the lens surface and the outer peripheral surface.