Method of manufacturing a composite optical element

Details Method of manufacturing a composite optical element Method of manufacturing a composite optical element

1999-09-23

2001-05-29

Vargot, Mathieu D. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Optical article shaping or treating

Composite or multiple layer

C264S002500, C425S808000

Reexamination Certificate

active

06238600

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 88114083, filed Aug. 18, 1999, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of manufacturing an optical element. More particularly, the present invention relates to a method for manufacturing a composite optical element.
2. Description of the Related Art
A composite optical element can constitute a transparent plastic material molded on a transparent optical element (such as glass or quartz). In general, from the optical point of view, aberrations exist on spherical lenses. If the surface of a lens is manufactured into a non-spherical shape, the formation of the spherical aberration will be reduced.
From the viewpoint of manufacturing process, the processing time and cost for non-spherical glass lenses are much higher than those for spherical glass lenses. Nevertheless, as molding technique further develops, plastic materials are more and more often being employed in the production of optical lenses. Workability of plastic is much better than that of glass, and it is cheaper to form a non-spherical lens from plastic than from glass. Moreover, plastic is lighter, has better tintability and shock resistance, and has a lower processing temperature than that of glass. But glass has better radiation resistance, durability and scratch resistance, and surface treatment is easier for glass than for plastic. Therefore, a composite lens that combines both glass and plastic materials will possess characteristics of both.
However, such a composite lens has two main problems. One is the big difference between the coefficients of thermal expansion of plastic and glass. The second one is that the binding between plastic and glass is not good enough. In general, delamination or cracking of the composite lens can occur under variation of temperature if the difference in the coefficients of thermal expansion of materials is too large. Moreover, molecular structures and functional groups cannot provide effective chemical bonds or physical entanglements between plastic and glass. Hence, the interface between glass and plastic lacks a strong binding.
In order to cope with the weaknesses described above, a layer of adhesive or coupling agent is coated between the plastic layer and the glass layer in the prior art such as the one disclosed in the U.S. Pat. No. 4,793,703. Alternatively, a coupling agent is added into the plastic layer such as the one disclosed in the Japanese Patent JP07306305. A holding force due to the encapsulation of the glass in the plastic may even be employed, such as those disclosed in the Japanese Patents JP59046601, JP01221701 and JP08190004. Addition of an adhesive or a coupling agent eventually increases the costs of material and equipment because an additional material is used. The environmental effect needs to be considered as well. The efficiency of composite lens production is low due to the many steps in the manufacturing process. Furthermore, the encapsulation method, which requires a plastic layer be extended from an optical surface of a glass lens over a lateral edge to the periphery of another optical surface, makes the structure of the molding apparatus more complicated.
SUMMARY OF THE INVENTION
In the light of the foregoing, the present invention provides a method of manufacturing a composite lens. In this method, only simple manufacturing process is required to produce a composite lens with good binding and optical quality.
The present invention provides a method of manufacturing a composite lens, wherein an adhesive or a coupling agent is not required to combine two lenses of different materials together, and hence, the manufacturing process can be simplified.
The present invention provides a method of manufacturing a composite lens, wherein the lateral edge of the lens is tilted at an angle &thgr; relative to the perpendicular center line of the lens. Thus, the formed plastic lens can hold the lens tightly, without separation. This is unlike the prior art in which the lens is tightly encapsulated, and hence, the structure is more complicated.
The method of manufacturing a composite lens disclosed in the present invention is described as follows.
A positioning ring is placed in a molding apparatus, or the positioning ring and the molding apparatus can be formed as a whole. The positioning ring has an inner edge, and the inner edge is tilted relative to the geometric center line of the positioning ring. A lens is placed inside the positioning ring with the inner edge of the positioning ring jammed against a lateral edge of the lens. The tilt angle of the inner edge of the positioning ring is designed to match the lateral edge of the lens. In addition, the thickness of the positioning ring is less than the thickness of the lens. A lens material is placed in the molding apparatus and covers the lens and the positioning ring. An upper mold is then placed on top of the lens material and the position of the upper mold is adjusted. A high temperature process is performed during which the lens material is hardened, and a composite lens is formed. The lens material can be a plastic material.
The lens described above has a first optical surface and second optical surface, and a lateral edge tilted at an angle relative to the perpendicular center line of the lens, which gives an outer edge diameter of the second optical surface smaller than the diameter of outer edge of the first optical surface. Moreover, a chamfer can be made at the junction between the first optical surface and the lateral edge of the lens, in accordance with the perpendicular center line of the lens. Thus, the breakage and cracking of the lens is prevented.
A positioning ring is placed in a molding apparatus, or the positioning ring and the molding apparatus can be formed as a whole. The positioning ring has an inner edge, and the inner edge is tilted relative to the geometric center line of the positioning ring. A lens is placed inside the positioning ring with the inner edge of the positioning ring jammed against a lateral edge of the lens. The tilt angle of the inner edge of the positioning ring is designed to match the lateral edge of the lens. In addition, the thickness of the positioning ring is less than the thickness of the lens. An upper mold is placed above the lens and the position of the upper mold is adjusted. An injection molding process is then performed during which a lens material is injected between the positioning ring, the lens and the upper mold, and hence, a composite lens is formed.
When a thickness of the lens is greater than a predetermined value, a plurality of guide rods can be placed on the positioning ring. Each of the guide rods is in contact with a portion of the lateral edge of the lens in order to secure the lens. The guide rods are placed equidistant from each other around the lens.
As the lateral edge of the lens is tilted at an angle relative to the perpendicular center line of the lens, the formed plastic lens can hold the glass lens tightly, without separation, and results in a good binding. The manufacturing steps are simple so that the cost of composite lens production can be reduced and the optical quality is maintained.


REFERENCES:
patent: 3903218 (1975-09-01), Humphrey
patent: 4179484 (1979-12-01), Neefe
patent: 4543146 (1985-09-01), Petcen
patent: 4921205 (1990-05-01), Drew, Jr. et al.
patent: 60-205401 (1985-10-01), None

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