JPS54118852A - Spectacle lens - Google Patents

Abstract

PURPOSE: To obtain a comfortable field of view continuously from far vision to near vision by providing the three portions of far vision, intermediate and near vision being continuously connected at the boundaries along the umbilical main meridian in nearly the central longitudinal direction.

CONSTITUTION: The main meridian MM' provided in nearly the central longitudinal direction is made umbilical over the entire line and is segmented to a far vision sight correcting portion F, intermediate sight correcting portion P and near vision sight correcting portion N from above, these being respectively continuously connected at the boundaries. Further, the curvature at the intermediate sight correcting portion P is progressively changed. Then, the circular intersecting line that the face crossing at a right angle to the main meridian MM' and the refractive face assume comes to the intermediate part of the intermediate sight correcting portion P, thus enabling the field of view of good total balance from the far vision part to the near vision part. In addition, the curvatures of the intersecting line group perpendicular to the main meridian MM' in the lower part of the intermediate sight correcting portion P and the near vision sight correcting portion N become smaller as they go away from the main meridian MM' and the curvatures of the intersecting line group perpendicular to the main meridian MM' in the upper part of the intermediate sight correcting part P and the far vision sight correcting portion N become larger as they go away from the main meridian MM', thus the astigmatisms and the distortion abetrations in the entire part of the lens are reduced.

COPYRIGHT: (C)1979,JPO&Japio