What's it about?

Optical designers assume a mathematically derived statistical distribution of the relevant design parameters for their Monte Carlo tolerancing simulations. However, there may be significant differences between the assumed distributions and the likely outcomes from manufacturing. Of particular interest for this study are the data analysis techniques and how they may be applied to optical and mechanical tolerance decisions. The effect of geometric factors and mechanical glass properties on lens manufacturability will be also be presented. Although the present work concerns lens grinding and polishing, some of the concepts and analysis techniques could also be applied to other processes such molding and singlepoint diamond turning.

1. INTRODUCTION

Lens design software generate optical tolerances by modeling a perturbed optical system to capture the effect of simultaneous changes in lens radius, center thickness, and other critical parameters in amounts matching the lens
manufacturer’s stated capabilities. One step in the tolerancing process involves assumptions^† concerning the statistical distribution of the relevant parameters for a Monte Carlo simulation. In some cases, the presumed distributions do not resemble the actual lens manufacturing distributions. For example, optical designers assume a center thickness tolerance that is symmetric about the nominal value, but lens manufacturing brings parts to tolerance, not nominal values. The best option would use actual manufacturing data to build a statistical distribution for the Monte Carlo simulation. Understanding true manufacturing distributions will have other beneficial consequences...