Case Study: Achieving 15x surface correction with ASI and MRF.

QED’s Aspheric Stitching Intermerometer (ASI) can extend the capture range of an asphere’s figure error beyond a traditional null setup. For example, a double-pass parabolic null setup’s measured phase is 4x the surface error, or 2x a typical surface measurement. This results in a 0.2 mrad resolvable slope before encountering the Nyquist limit (assuming a 640 x 480 camera over a 7” field of view). Because it combines locally nulled and magnified subaperture single-pass surface measurements, the ASI could acquire the 7” parabola below whose high slope zones initially exceed 0.4mrad while a null setup could not. Rather than needing to revert to a profilometry method, the ASI allowed a full surface correction using MRF. The 15x surface correction included high frequency corrections of several zones.