Phase shifting interferometry and white light interferometry are accurate techniques for surface analysis. These methods require an accurate scanning of the optical path difference for evaluating the phase at each surface point. Alternative techniques, avoiding the z surface scanning were recently proposed. They are based on a spectroscopic analysis of white light interferograms and were called Double Spectral Modulation (DSM). The interferometric set-up is associated to a diffraction grating and an image compression is performed. Thus absolute and unambiguous phase values are obtained along the spectral axis. This procedure allows nanometric resolution using two (or four) interferograms. In this paper we present a better approach to DSM which reduces by a factor of two the number of interferograms which must be analyzed. After data processing, a 3D image of the surface is reconstructed and any longitudinal or lateral scanning is avoided. This paper presents the principle and the data processing of the proposed method and experimental results as well.

Date Published: 18 September 1996
PDF: 9 pages
Proc. SPIE 2782, Optical Inspection and Micromeasurements, (18 September 1996); doi: 10.1117/12.250765

Published in SPIE Proceedings Vol. 2782:
Optical Inspection and Micromeasurements
Christophe Gorecki, Editor(s)