Infinite deflectometry enabling 2π-steradian measurement range

L. R. Graves, H. Quach, H. Choi, D. W. Kim

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


We present a novel deflectometry implementation termed Infinite Deflectometry. The technique provides a full aperture surface reconstruction sag map of freeform surfaces, including previously challenging to measure optics such as highly convex surfaces. The method relies on the creation of a virtual source enclosure around the tested optic, which creates a virtual 2π-steradian measurement range. To demonstrate the performance, a fast f/1.26 convex optical surface was measured with a commercial interferometer and with the Infinite Deflectometry system. After removing Zernike terms 1 through 37, the metrology tests resulted in absolute RMS surface values of 18.48 nm and 16.26 nm, respectively. Additionally, a freeform Alvarez lens was measured with the new technique and measured 22.34 m of surface sag RMS after piston, tip/tilt, and defocus had been removed. The result deviated by 488 nm RMS from a profilometer measurement while standard interferometry failed to measure the Alvarez lens due to its non-nulled wavefront dynamic range limitation.

Original languageEnglish (US)
Pages (from-to)7602-7615
Number of pages14
JournalOptics Express
Issue number5
StatePublished - 2019

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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