A dither in path length can dramatically improve the accuracy of wavelength-shift methods used for absolute distance interferometry. Here we report how a dither improves the accuracy of absolute distance measurement by two orders of magnitude, reducing errors from ~1?mm to ~10??m (1?s ). The dither is provided by modulating the position of a cube corner reflector in the reference arm of the interferometer. The modulation amplitude is on the order of 10??m, short relative to the synthetic wavelength associated with our wavelength-shift but much longer than the physical wavelength of our laser (670?nm). The effect of errors in our system that have periodicity of 1/2 wavelength can be largely eliminated by averaging results while modulating the path length.
Proceedings Title: Proceedings of American Society for Precision Engineering
Conference Location: Monterey, CA
Pub Type: Conferences
absolute interferometry, diode lasers, dither, interferometry, length measurement, wavelength-shift interferometry