2 Breakthrough by Bernard Maitenaz

2.1 Focus on the manufacturing process

In a first patent filed in 1932 (US 2 001 952) Henry James Birchall briefly described (not part of the claims) a manufacturing method for a progressive lens with circles as orthogonal sections. In a second patent filed in 1945 (US 2 475 275) he describes qualitatively how the curvature of the orthogonal sections has to evolve from the main meridian to the edge of the surface in order to reduce the lateral distortion. This is also the goal of Kanolt who in his patent US 2 878 721 (application 1954) gives a mathematical description of special surfaces which are calculated to respect certain thresholds of the peripheral astigmatism.

So up to the fifties certain basic elements characterizing the structure and the performance of progressives were known, but the patents describe almost exclusively the geometry of the surfaces and do not address the problem of how to realize the lens. Bernard Maitenaz supposes [2] that the optical industry was rather satisfied with the bifocal correction and the research efforts were moreover concentrated on the minimization of aberrations instead of creating new designs which inevitably have surface astigmatism in the periphery.

Bernard Maitenaz (middle), Dominique Meslin (left), 2009

When Bernard Maitenaz started his career with the Société des Lunetiers (SL) his mission was not to develop a progressive lens but to improve the manufacturing process for mineral lenses. The Essilor history and the development of Varilux and Varilux 2 are presented in [3]. In the beginning it was his personal project to develop a new lens correcting presbyopia in a more natural way than a bifocal does. But as a consequence of his education as an engineer the theoretical concept of a lens providing a continuous vision in all distances made only sense for him, when there were the technical means to produce it. This was the decisive difference between him and the scientists and inventors having previously worked on the concept of a progressive lens.

The first patent by Bernard Maitenaz, application date France, November 25, 1953 (here the US version US 2 869 422)

So already in his first patent, filed November 25, 1953 in France he defined a progressive lens together with two proposals for manufacturing methods. The progressive design was characterized by an umbilical line and a circle as the generatrix curve. The different stages of the development of the lens design and the manufacturing method are described by Bernard Maitenaz in “Four steps that led to Varilux “ [4]. In the following years between 1955 and 1959 Bernard Maitenaz filed four patents US 2 915 856, US 3 021 647, US 2 982 058, and US 3 041 789. In the first patent “Machine for Grinding an Optical Surface in a Piece of Refractive Material” the generating surfaces are more complex than the circle generatrix in the first patent, resulting in orthogonal sections as for example parabolas, ellipses or hyperbolas. The second patent protects a machine for honing, the manufacturing stage between grinding and polishing of the progressive surface. The third and fourth patents are the basis for manufacturing progressive lenses by a copy process using a point to point machined steel alloy model.

In 1959 the Société des Lunetiers successfully launched Varilux - the first commercial progressive lens