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Freeform optical components enable dramatic advances for optical systems in both performance and packaging. Surface form metrology of manufactured freeform optics remains a challenge and an active area of research. Towards addressing this challenge, we previously reported on a novel architecture, cascade optical coherence tomography (C-OCT), which was validated for its ability of high-precision sag measurement at a given point. Here, we demonstrate freeform surface measurements, enabled by the development of a custom optical-relay-based scanning mechanism and a unique high-speed rotation mechanism. Experimental results on a flat mirror demonstrate an RMS flatness of 14 nm (∼λ/44 at the He-Ne wavelength). Measurement on a freeform mirror is achieved with an RMS residual of 69 nm (∼λ/9). The system-level investigations and validation provide the groundwork for advancing C-OCT as a viable freeform metrology technique.
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Reconfigurable interferometry for freeform optics using a spatial light modulator
A spatial light modulator is deployed as the nulling element in the interferometric measurement of a freeform optic. Form measurement of a 65 mm aperture concave freeform with 91 μm peak-valley freeform sag is reported.
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- PAR ID:
- 10517934
- Publisher / Repository:
- Advanced Metrology Systems III: Interferometry at Optica Design and Fabrication
- Date Published:
- Journal Name:
- Advanced Metrology Systems III: Interferometry at Optica Design and Fabrication
- ISBN:
- 978-1-957171-22-7
- Format(s):
- Medium: X
- Location:
- Québec City, Québec Canada
- Sponsoring Org:
- National Science Foundation
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