What's it about?

This presentation will look at sources of lens centration manufacturing errors in singlets and cemented doublets, how manufacturing errors can be modeled in lens design software and how to specify centration tolerances on lens drawings.

1. ERROR SOURCES FOR LENS CENTRATION  

Contained in any lens, there are two primary axes, the optical axis, the axis passing through the two centers of curvature of the spherical surfaces, and the mechanical axis, the axis passing through the physical center of the lens in a direction parallel to the edge diameter. In a perfectly centered lens, these two axes are concurrent and coincidental, superimposed on each other. Centration errors arise from deviation from superposition.

Centration errors can introduce aberrations and reduce the performance of an optical system¹, and the fabricator takes steps to avoid them. Lenses are left oversized in diameter, and centration errors are allowed to accumulate to some in-process limit. After surface preparation, the lenses are edged to final diameter with a goal...