In this work, we propose the development of an Advanced Nanometer Coordinate Measuring Machine (ANCMM; pronounced ’aŋ-kem) to complement the metrology probe and complete the metrology solution. The ANCMM will enable larger, lower cost, and higher quality freeform and aspheric optics, bridging the present gap between commercial coordinate measuring machines (CMMs) and interferometry, and for many applications, replacing areal interferometry as the primary means of feedback to optical fabrication and requirements verification. This work will push CMM technology into the realm currently dominated by expensive, complex and error-prone optical testing.
ANCMM will have the capability to measure the prescription and mid- and low-order surface error for meter-class segments for large astronomical telescopes. Accurate metrology of the prescription (i.e., radius of curvature, conic constant, and off-axis distances) will speed the fabrication, hence reducing costs, of primary mirror segments, because ANCMM metrology will have greater dynamic range than current CMM technology, allowing ANCMM to be used “deeper” into the fabrication process (i.e., from rough machining and grinding of blanks though the fine stages of optical polishing) before transitioning to an interferometric test, if that is even required for the final stages of polishing and verification.
Both cylindrical mirrors and freeform surfaces require stringent surface requirements and plan to be implemented in future NASA missions like LISA and LUVOIR. OptiPro Systems and the UNC Charlotte Center for Precision Metrology have built and tested contact and non-contact multi axis measurement platforms and will be utilized during this project. Theoretical and laboratory experimental data analysis of prospective instruments and measurement techniques will guide the development of the design constraints and provide valuable data to verify the ANCMM system uncertainty budget.
NASA projects can utilize optical test solutions that do not need a custom null lens or at least could use a CMM to cross check results from a traditional optical test. Current and future applications:
-Lynx X-Ray Surveyor optics; Prescription test & system alignment
-LISA; system alignment
-LUVOIR; improve cost/schedule on primary mirror segment fabrication; improve quality and cross check optical results on secondary mirror (figure error and prescription)
-Freeform optics of all sizes; as-built prescription; figure error (low order form error)
The ANCMM platform would reduce the reliance on custom null lens techniques (e.g., computer generated holograms, reflective/refractive nulls). Applications include:
Freeform Mirrors,Aspheres & ACylinders,Single Point Diamond Turned Surfaces,Diffractive Optics,Freeform Illumination Lenses,Corrector Optics