Absolute distance interferometer in LaserTracer geometry

An absolute distance interferometer based on a hybrid measurement technique was developed with the goal to achieve optimum performance in a LaserTracer. The challenges lie in the compact dimensions as very limited space is available and in the special design of the LaserTracer with a steel sphere as an interferometer reflector. To enable accurate absolute distance measurements three diode lasers are used, two permanently stabilized to D1 and D2 absorption lines of potassium at wavelengths of 770.1 nm and 766.7 nm. These are used for a two-colour measurement with the resulting synthetic wavelength of 174 μm. The third laser is modulated and used for variable synthetic wavelength interferometry. Its measurement is used to unwrap the more accurate two-colour measurement. First results of this set-up in the laser tracer geometry up to 2.3 m length are presented, providing insight into the performance of this measurement principle in 3 D.article based on oral presentation at the conference MacroScale 2011 "Recent developments in traceable dimensional measurements", Bern-Wabern (Switzerland), 04-06, October, 201