Multifocal ophthalmic lenses

Details Multifocal ophthalmic lenses Multifocal ophthalmic lenses

1981-06-30

1984-11-27

Corbin, John K.

Optics: eye examining, vision testing and correcting

Spectacles and eyeglasses

Ophthalmic lenses or blanks

351171, G02C 706

Patent

active

044848048

ABSTRACT:
Multifocal ophthalmic lenses are disclosed such as a bifocal lens in which the convex front surface includes an upper part for distant vision having a first spherical surface and a lower part for reading having a second spherical surface, the radius of the first spherical surface being greater than the radius of the second spherical surface. A zone of curvature continuity connects the first and second spherical surfaces along at least one meridian, e.g. a central meridian, of the ophthalmic lens, and the second spherical surface extends away from the zone of surface continuity into a surface of revolution which may be spherical or toroidal. Junctions between the surfaces are defined by ledgeless intersections which are lines of curvature discontinuity extending away from the zone of surface continuity. In case of trifocal lenses, a third crescent-shaped spherical surface, having a radius of length intermediate the radii of the first and second spherical surfaces, is interposed between the first and second spherical surfaces.

REFERENCES:
patent: 2405989 (1946-08-01), Beach
patent: 3010366 (1961-11-01), Crawford
patent: 4274717 (1981-06-01), Davenport

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