JPS5484750A - Spectacle lens - Google Patents

Abstract

PURPOSE: To eliminate fluctuations of an image in the medium vision position, by providing a part, which is not an umbilical point, in the plane running along the principal meridian in the near -sightedness correcting position, and providing an umbilical point curve in the horizontal direction of the medium vision correcting position so as to remove astigmatism in the near-sightedness correcting position.

CONSTITUTION: In the long-sightedness correcting position F, the intersecting line group formed by the plane orthogonal to the principal meridian M-M' and the refracted plane is not circular, and the curvature increases as going away from the meridian M-M'. The near-sightedness correcting position N is a part of aspherical face symmetrical with respect to the axis of rotation, and the curvature decreases in the peripheral region, and a part not an umbilical point is provided 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 a curve which is not circular. And the plane running along a certain intersecting line Cn-Cn' is made in an umbilical point. By thus constituting, the visions for both near-and long-sightedness may by clear, and the image fluctuations in the medium vision are eliminated, so that an excellent imaging performance may be obtained.

COPYRIGHT: (C)1979,JPO&Japio