7. Varilux 2, the physiological design
Varilux 1 was a design trying to optimize the conditions for the static, foveal vision. The Varilux 2 concept takes into account the global vision process including peripheral and dynamic visual perception. The consequence was a totally aspherical surface with an umbilical meridian and orthogonal sections, which in a first approximation, are conic sections with varying parameters. The calculations of the designs are based on the examples given in US 3 687 528 and US 3 910 691.The meridian shows a sinus-like shape, which is reflected in a periodic pattern of the isolines- plots. The design includes two horizontal umbilical lines and two vertical isoprismatic lines in order to reduce the lateral astigmatism and to achieve orthoscopy, which means minimum distortion of a rectangular grid.
The deviation of the orthogonal sections' geometry from evolutive conic sections is illustrated. The difference between the Varilux 2 launched on the market and the "patent design" is briefly discussed.
7.1 The coordinate system
7.2 The principal meridian
7.3 The characteristical data of the conic sections
7.4 Geometry and equations of the progressive surface
7.5 Calculation of the half-axis h(z0) of the conic sections
7.6 Analysis of design and calculations