METHOD FOR DESIGNING GROUP OF BI-ASPHERICAL TYPE PROGRESSIVE POWER LENSES, AND GROUP OF BI-ASPHERICAL TYPE PROGRESSIVE-POWER LENSES

摘要

There is provided a group of bi-aspherical type progressive-"power lenses for which the processing costs are reduced. In a bi-aspherical type progressive-power lens(es), the relationships DHf + DHn DVf + DVn and DHn DVn or further, DVn - DVf ADD/2 and DHn - DHf ADD/2 are satisfied; DHf and DVf are designated respectively as a surface refractive power in a horizontal direction and a surface refractive power in a vertical direction at a far vision power measurement position Fl on a first refractive surface that acts as an object-side surface; with DHn and DVn are designated respectively as a surface refractive power in a horizontal direction and a surface refractive power in a vertical direction at a near vision power measurement position Nl on the first refractive surface; a surface astigmatism component at Fl and Nl of the first refractive surface is canceled by a second refractive surface of the eye-side surface; and the first and second refractive surfaces are combined to provide a far vision power (Df) and an addition (ADD) on the basis of a prescription; wherein the same first refractive surface is used for at least two or more kinds of different addition power.