| abstract |
A thermoformed plastic laminar light-polarizing composite lens blank is produced from a laminate including light-polarizing layer between polymeric layers. At least one of the polymeric layers is an optically isotropic sheet, i.e., a sheet having an optical retardance of 20 nanometers in order to minimize retardation effects of the birefringent material on plane polarized light. The isotropic layer or subsequent thermoforming of unitary portions cut from the laminate provides the convex lens surface of the lens blank. The polymeric layer which forms the concave surface of the lens blank is substantially thicker than the opposed polymeric layer in order to accommodate grinding of the surface thereof to an ophthalmic prescription. Lens blanks are prepared from unitary portions which are cut from a supply of the laminate, placed between thermoforming platens and formed under heat and pressure. By using a series of platens of different radius of curvature, for the forming of the convex surface of the lens blanks, a series or family of lens blanks can be provided to accommodate the grinding of lens to a variety of ophthalmic prescriptions. |