Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1993-09-02
1996-07-30
Sugarman, Scott J.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
351177, 425808, 451 42, G02C 704, B29D 1100, B24B 100
Patent
active
055416780
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a contact lens, and more specifically to a contact lens provided with front curves formed with a plurality of distance portion curved surfaces and a plurality of near portion curved surfaces arranged alternately and repeatedly in concentric zone shape. In addition, the present invention relates to a method of manufacturing the same.
BACKGROUND OF THE ART
A multi-focal contact lens formed with a plurality of distance portions for seeing a distant place and a plurality of near portions for seeing a near place arranged alternately in concentric zone shape has been proposed in Japanese Published Unexamined (Kokai) Patent Application No. 59-146200, for instance. When the user uses the contact lens as described above, the user can select one of the distance portions and the near portions by the user' consciousness. In other words, since the user can properly use one of the distance portions and the near portions naturally and smoothly, these contact lenses are useful for the users.
In more detail with reference to FIG. 6, the contact lens 1 as described above is provided with a front curve 2 and a base curve 3 fitted to a curved surface of the user' cornea. The front curve 2 is formed with a plurality of distance portion curved surfaces F.sub.1, F.sub.2, . . . and a plurality of near portion curved surfaces N.sub.1, N.sub.2, . . . . These distance and near portion curved surfaces are arranged alternately and repeatedly in concentric zone shape.
In the conventional contact lens of this sort, a plurality of distance portion curved surfaces F.sub.1, F.sub.2, . . . and a plurality of near portion curved surfaces N.sub.1, N.sub.2, . . . are formed as follows:
Here, a radius of curvature of the distance portion curved surface is represented by r.sub.F, and a radius of curvature of the near portion curved surface is represented by r.sub.N. First, a circle with a radius r.sub.F is described with a point P on an optical axis (z axis) as its center to obtain an intersection point O.sub.F1 between the described circle and the optical axis. The obtained intersection point O.sub.F1 is determined as a center of curvature of the distance portion curved surface F.sub.1. Then, a circle with a radius r.sub.F is described with the curvature center O.sub.F1 as its center to obtain an intersection point P.sub.F1 between the described circle and a straight line l.sub.F1 parallel to the optical axis. This parallel straight line l.sub.F1 is used to determine a predetermined radial zone width of the distance portion curved surface F.sub.1. Further, a circle with a radius r.sub.N is described with a point P.sub.F1 as its center to obtain an intersection point O.sub.N1 between the described circle and the optical axis. The obtained intersection point O.sub.N1 is determined as a center of curvature of the near portion curved surface N.sub.1. Then, a circle with a radius r.sub.N is described with the curvature center O.sub.N1 as its center to obtain an intersection point P.sub.N1 between the described circle and a straight line l.sub.N1 parallel to the optical axis. This parallel straight line l.sub.N1 is used to determine a predetermined radial zone width of the near portion curved surface N.sub.1.
In the same way as above, a circle with a radius r.sub.F is described with a point P.sub.N1 as its center to obtain an intersection point with the optical axis. The obtained intersection point is determined as a center O.sub.F2 of the curvature of the distance portion curved surface F.sub.2. With this obtained curvature center O.sub.F2 as its center, a circle with a radius r.sub.F is described to obtain an intersection point P.sub.F2 between the described circle and a straight line l.sub.F2 parallel to the optical axis and thus to determine a predetermined radial zone width of the distance portion curved surface F.sub.2. Further, a circle with a radius r.sub.N is described with a point P.sub.F1 as its center to obtain an intersection point with the optical axis. The obtained intersectio
REFERENCES:
patent: 4162122 (1979-07-01), Cohen
patent: 4890913 (1990-01-01), De Carte
patent: 4898461 (1990-02-01), Portney
patent: 5106180 (1992-04-01), Marie
Awanohara Yoshinori
Kamiwaki Osamu
Shinohara Toshihide
Wada Osamu
Seiko Epson Corporation
Sugarman Scott J.
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