What's it about?
This paper is an introduction to specifications and tolerances intended to more thoroughly define figure and form of precision optical elements. Specifications that will be outlined here include Mid-Spatial Frequency Wavefront Error, Slope, and PVr.
1. MID-SPATIAL FREQUENCY ERROR
Most models of optical systems presume ideal surfaces however; surface preparation and metrology methods lead to non ideal surfaces. Such departures from ideal form can be characterized as undulations across the surface. Sub-aperture and deterministic polishing techniques are more prone to periodic surface undulations commonly referred to as ripple or mid spatial frequency (MSF) error.
Figure 1-1 depicts one surface fabricated using sub-aperture deterministic polishing techniques. The path taken by the sub-aperture polisher is clearly...