In sinusoidal phase-modulating interferometry an optical path length (OPD) larger than a wavelength is measured by detection of sinusoidal phase-modulation amplitude <i>Z</i><sub><i>b</i></sub> of the interference signal that is produced by sinusoidal scanning of the wavelength of a light source. A light source with a large scanning width of wavelength is created by use of a superluminescent laser diode for the error in the measured value obtained by <i>Z</i><sub><i>b</i></sub> to be smaller than half of the central wavelength. In this situation the measured value can be combined with a fractional value of the OPD obtained from the conventional phase of the interference signal. A sinusoidal wavelength-scanning interferometer with the light source measures an OPD over a few tens of micrometers with a high accuracy of a few nanometers.
© 2000 Optical Society of America
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(120.6650) Instrumentation, measurement, and metrology : Surface measurements, figure
Osami Sasaki, Norihiko Murata, and Takamasa Suzuki, "Sinusoidal Wavelength-Scanning Interferometer with a Superluminescent Diode for Step-Profile Measurement," Appl. Opt. 39, 4589-4592 (2000)