JPS54118849A - Spectacle lenses - Google Patents

Abstract

PURPOSE: To obtain a comfortable field of view continuously from far vision to near vision by forming the main meridian in nearly the central longitudinal direction umbilical over the entire line and segmenting the far vision part, intermediate part and near vision part from above.

CONSTITUTION: The main meridian MM' provided nearly in 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 made respectively continuous at the boundaries. Further the curvature at the intermediate sight correcting portion P is progressively changed. As a result, the circular intersecting line that the face crossing at a right angle to the main meridain MM' and the refractive face assume comes to the lower end of the intermediate sight correcting portion P or lower than that, whereby a wide field of veiw from the progressive focus to the far vision sight correcting portion F may be obtained. In addition, the curvatures of the intersecting line groups perpendicular to the main meridina MM' in the intermediate and far vision sight correcting portions P, F become larger as they go away from the main meridian MM' and the distortions of the entire part of the lens are suppressed small at the peripheral part of the intermediate and far vision sight portions P, F.

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