JPS5484751A - Spectacle lens - Google Patents

Abstract

PURPOSE: To improve the imaging meridion performance, by providing a part, which is not an umbilical point, on the plane running along the principal in the near-sightedness correcting position,and providinf a curve of which vertical direction component of the prism is constant in the medium vision correcting position.

CONSTITUTION: The long-sightedness correcting position F of variable focal spectacle lens is part of aspherical face symmetrical with respect to the axis of rotation of which curvature is larger in the peripheral part. The near-sightedness correcting position N thereof is an aspherical face symmetrical with respect to the axis of non-rotation, and has a part which is not an umbilical point in at least one part on the plane running along the principal meridian M-M'. In the medium vision correcting position P, the intersecting line group Cn-Cn' formed by the plane Ln orthogonal to the principal meridian M-M' and the refracted plane contains also a circular form, and it is so constituted that the vertical component of the prism is constant along a certain intersecting line of the intersecting line group. By thus constituting, the astignatism on the side of the medium vision corrrecting position P may be reduced, so that an excellent imaging performance may be obtained.

COPYRIGHT: (C)1979,JPO&Japio