JPS54145555A - Spectacle lens - Google Patents

Abstract

PURPOSE: To obtain a comfortable field of view continuously from far vision to near vision by continuously connecting the respective boundaries of the three of far vision part, intermediate part (progressive zone) and near vision part from above along the main meridian in the central longitudinal direction and progressively changing the curvature in the progressive zone.

CONSTITUTION: If an example is taken of the lens of addition diopter 2D and far vision part diopter +1D, the lens is divided to a far vision part F, intermediate part (progressive focus part)P and near vision part N along the main meridian MM' and the circular intersecting line composed of the plane crossing the MM' at a right angle and a refracting face exists at the point A. If far vision part diopter DF, progressive part diopter DP and near vision part diopter DN, then these are DF= 1D, 1D≤DP≤3D, DN=3D. The curvature becomes smaller the further it goes from the MM' in the lower part of the P region and in the N region, and the curvature becomes larger the further it goes from the MM' in the upper part of the P region and in the F region and therefore, the lens of smaller astigmatism and distortion aberrations and of well balanced performances over the entire part of the lens may be obtained.

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