We describe a method that combines phase-shifting and coherence-peak-sensing techniques to permit measurements with the height resolution of phase-shifting interferometry without the interval-slope limitation of λ/4 per data sample of phase-shifting interferometry. A five-frame algorithm is used to determine both the best-focus frame position and the fractional phase from the best-focus frame of the correlogram acquired through vertical scanning. The two surface profiles retrieved from the phase and the modulation contrast of the correlograms are compared in the phase-unwrapping process to remove fringe-order ambiguity.
© 2000 Optical Society of America
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
(120.6660) Instrumentation, measurement, and metrology : Surface measurements, roughness
(180.3170) Microscopy : Interference microscopy
Akiko Harasaki, Joanna Schmit, and James C. Wyant, "Improved Vertical-Scanning Interferometry," Appl. Opt. 39, 2107-2115 (2000)