Machining and Metrology of a Chalcogenide Glass Freeform Lens Pair

Slow tool servo remains a preferred method for ultraprecision manufacture of freeform optics with millimeter-scale departures from an axisymmetric surface. A methodology has been developed for pre-process mapping of, and compensation for, predictable error sources such as tool waviness and machine misalignment, reducing necessity for typical post-process workpiece error correction procedures. This methodology is implemented for manufacture of a chalcogenide glass freeform lens pair for a variable-focus thermal imaging application. Process development, part metrology, and system functional testing are presented.