Abstract

Absolute measuring of distances larger than 10 m with an uncertainty of far less than 10^-5 by laser interferometry points to a specific problem: The short optical wavelength makes a high precision feasible, but for absolute distance information the required wavelength has to be much longer. A well-known solution of this problem is to take use of multiple optical wavelengths to generate synthetic microwaves in a heterodyne arrangement.¹ An alternative system we built in contrast is based on tunable solid-state lasers. It allows to tune one laser source against a reference laser about Δv = 0.60 GHz, generating a tunable synthetic wavelength² of many meters down to 5 mm. Assuming a phase measuring uncertainty of 10^-3 yields in a length measuring accuracy of 5 μm, which will match the requirements mentioned above.

© 1994 IEEE