Patent ID: 7712897

Claim:
A method for creating a progressive varifocal lens having a far vision area, a near vision area and an intermediate progression area, comprising the steps of: a) determining the x and y coordinates of a first point in the closed interval between a far vision reference point of the far vision area and a center point; b) determining the x and y coordinates of a second point as the near vision reference point of the near vision area; c) determining of a mathematical function D(y) obeying the following conditions: I) it contains the first point as local extremum; II) it contains the second point as local extremum; and III) in the open interval between the first and second points, it contains precisely one point of inflection; d) distributing the addition according to the function D(y) along a principal meridian of progression connecting the first and second points; and e) forming the varifocal lens, wherein the function D(y) between the first point and the second point substantially obeys an even power of a trigonometric function, especially a Sin 2 function of the interval [0, π/2].