Open AccessΓ-profilometry: a new paradigm for precise optical metrology
Author(s) -
Claas Falldorf,
Mostafa Agour,
André F. Müller,
Ralf B. Bergmann
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.434510
Subject(s) - metrology , optics , coherence (philosophical gambling strategy) , interferometry , profilometer , sampling (signal processing) , surface metrology , physics , ptychography , degree of coherence , wavefront , computer science , detector , diffraction , surface roughness , beam (structure) , quantum mechanics
We show that the shape of a surface can be unambiguously determined from investigating the coherence function of a wave-field reflected by the surface and without the requirement of a reference wave. Spatio-temporal sampling facilitates the identification of temporal shifts of the coherence function that correspond to finite height differences of the surface. Evaluating these finite differences allows for the reconstruction of the surface using a numerical integration procedure. Spatial sampling of the coherence function is provided by a shear interferometer whereas temporal sampling is achieved by means of a Soleil-Babinet compensator. This low coherence profiling method allows to determine the shape of an object with sub-micrometer resolution and over a large unambiguity range, although it does not require any isolation against mechanical vibration. The approach therefore opens up a new avenue for precise, rugged optical metrology suitable for industrial in-line applications.