公开(公告)号：JPS6432227A

公开(公告)日：1989-02-02

申请号：JP16864988

申请日：1988-07-06

Applicant: ESSILOR INT

Inventor： MOORISU DOUFUURU

IPC: G02C7/06 ,  G02C7/02

Abstract: PURPOSE: To obtain excellent visual comfortableness whatever the diopter entry value of a lens is by constituting the surface of the lens of an area for far sight, an area for middle sight, and an area for near sight and determining the curvature of the principal meridian by a specific variance rule. CONSTITUTION: A surface S of a lens L consists of a visual field area VL for far sight, a visual field area VI for middle sight, and a visual field area VP for near sight. The curvature of the area VI is increased upward along a principal meridional curve MP. A curve C1 as the boundary between areas VI and VP crosses the curve MP at a point A2. Similarly, a curve C2 as the boundary between areas VI and VP crosses the curve MP at a point A2. The curvature of the curve MP starts changing at a point A3, which is a distance d1=f(A) off the point A2, in the area VI and is changed in the same direction up to a point A4, which is a distance d2=h(A) off the point A2, also in the area VP. The difference between curvatures at points A2 and A4 is denoted as ▵C=g(A). These functions f(A), h(A), and g(A) are reduction functions of a diopter entry value A of the lens between points A1 and A2.