Chirped synthetic-wavelength interferometry

Abstract
We demonstrate distance measurement by varying, or chirping, the synthetic wavelength in a two-color laser diode interferometer. An absolute accuracy of 3 μm is achieved over a 200-mm range, without the phase ambiguities or optical complexities normally associated with synthetic-wavelength interferometry. The fiber-coupled experimental system uses a 25-μW, 0.25-mm-diameter collimated object beam and can be used for dimensional gauging and rough-surface profiling.