Essilor International Cie Generale D'optique

Bernard Mignen

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.

Multifocal ophthalmic lenses

An ophthalmic lens made of organic material has at least one layer of photochromic mineral glass within its mass to impart photochromic properties to the lens. This layer has a fibrous structure and may comprise a piece of woven fabric produced from fibres of photochromic mineral glass possessing a refractive index and a coefficient of chromatic dispersion which are equal to those of the constituent organic material of the lens.

Photochromic ophthalmic lens of organic materials

The invention relates generally to the production of ophthalmic lenses having, on one face, an active zone of progressively variable radius of curvature. According to the invention, when the blank from which such a lens is obtained is being cast, there is formed, on the periphery of its active zone, an edge region or facet extending continuously and circularly right round the said active zone for the subsequent support of the mould which is used to enable a gripper block to be cast on the face of the blank so as to enable a second machining operation to be carried out on the opposite face of the blank.

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Saint-Maur, France

Bernard Mignen