JPS54107747A - Spectacle lens - Google Patents

Abstract

PURPOSE: To give a comfortable field of view continuously from far vision up to near vision to presbyopes by so forming the lens that curvatures become smaller in lower region and larger in upper region as the group of intersecting lines that the plane perpendicular to the main meridian assumes goes away from the main meridian.

CONSTITUTION: A far vision part F, progressive focus part P and near vision part N are provided along the main meridian MM' of the progressive degree spectacle lens. At the point A, the circular intersecting line consisting of the plane intersecting at a right angle to the main meridian MM' and a refracting face exists. In the F region, the curvature becomes larger as it goes away from the line MM' and in the N region the curvature becomes smaller as it goes away from the MM' and therefore the curvature of the entire part of the lens may be kept minimum. When necessary, it is possible to add an umbilical curve parallel to the main meridian MM' or the circular intersecting line, thus a comfortable field of view may be given along the main meridian MM'.

COPYRIGHT: (C)1979,JPO&Japio