A technique is described for determining absolute lengths up to 3 m from measurement of the interference fringe fractions for multiple wavelengths. The required accuracies of the wavelength ratio and fringe fraction reading are analyzed. To satisfy the accuracies, a low-cost simply stabilized He—Xe laser, operating simultaneously at two wavelengths, 3.51 and 3.37 µm, was developed. Using this laser the preliminary measurement of the wavelength ratio was made interferometrically with the length standard of a gauge block.
© 1981 Optical Society of America
Hirokazu Matsumoto, "Infrared He—Xe laser interferometry for measuring length," Appl. Opt. 20, 231-234 (1981)