8. Orthoscopy

The distortion of vertical and horizontal lines has a strong influence on the adaptation of progressive lenses. B. Maitenaz describes in US 3 687 528 and US 3 910 691 quantitatively the phenomenon of static and dynamic distortion. A mathematical model for the the prismatic deformation of a rectangular grid by a progressive surface is defined. The characteristics of non-orthoscopic designs of lenses of the first generation are presented.

Based on results of chapter 7 the distortion of horizontal and vertical object lines by the Varilux 2 geometry is calculated and represented graphically. The isoprismatic lines of the design characterize the structure of the grid image. By the concept of Orthoscopy the Varilux 2 design maintains largely the orientation of vertical and horizontal lines.

Contents

8.1 Distortion, definition and calculation model
8.2 Non orthoscopic designs
8.3 Distortion of the Varilux 2 design

> 8. Orthoscopy