The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 23, 1999
Filed:
Jun. 06, 1996
Tadashi Kaga, Suwa, JP;
Kazutoshi Kato, Suwa, JP;
Seiko Epson Corporation, Tokyo, JP;
Abstract
In a process of determining the surface shape of each of progressive multifocal lenses for use as lenses in eyeglasses, radii of curvature at main points are calculated, and then the surface is divided into a plurality of lattice sections, and then a curved-surface equation in the form of a bicubic expression is used for each section to determine the surface shape of the lens. A coefficient of each of the bicubic expressions is determined under a condition that continuation is established to curved-surface equations of sections adjacent at a boundary line between the sections to the derivatives of second order. Therefore, the surface shape of the lens obtained by the curved-surface equation for each section can be formed into a continuous and smooth surface. Since the curved surface can be determined for each section, a partial correction can easily be performed, if necessary. As a result, a progressive multifocal lens can be provided which exhibits smooth astigmatism curves and a large clear field of vision to meet a variety of specifications. Thus, lenses for eyeglasses each having a clear field of vision can be provided.