Translator Disclaimer
Presentation + Paper
21 August 2020 Cascade optical coherence tomography (C-OCT) towards freeform metrology
Author Affiliations +
Abstract
Surface form metrology for freeform optical components is a significant challenge that impacts the entire process chain. One of the main aims is that the metrology technique provides sufficiently low measurement uncertainty within a reasonable measurement time. We developed a non-contact, non-part-specific cascade optical coherence tomography (COCT) technique within this metrology context. C-OCT utilizes a primary and a secondary interferometer in a cascade that transforms a difficult-to-measure optical path difference (OPD), which encodes the freeform sag in this case, into a more readily measured OPD in the secondary interferometer. To enable high-speed measurements, we developed the secondary interferometer based on a rotating optical cube. A custom telecentric objective lens and a custom pupil relay enable optical scanning over the sample surface. Experimental results validate the C-OCT technique with consecutive single-point measurements showing precision of ±26 nm (~λ/24 at the He-Ne wavelength) and a preliminary flat surface measurement demonstrating 22 nm RMS (~λ/28) over a central 20 mm diameter region. Developments on the system are underway towards surface measurements on freeform optical components.
Conference Presentation
© (2020) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Di Xu, Andres Garcia Coleto, Zhenkun Wen, Benjamin Moon, Jonathan C. Papa, Michael Pomerantz, John C. Lambropoulos, and Jannick P. Rolland "Cascade optical coherence tomography (C-OCT) towards freeform metrology", Proc. SPIE 11490, Interferometry XX, 114900K (21 August 2020); https://doi.org/10.1117/12.2567080
PROCEEDINGS
9 PAGES + PRESENTATION

SHARE
Advertisement
Advertisement
KEYWORDS
Interferometers

Mirrors

Optical coherence tomography

Metrology

Freeform optics

Objectives

Optical components

Back to Top