Tunable, double-wavelength heterodyne detection interferometer for absolute-distance measurements

We present a novel absolute-distance meter based on double heterodyne interferometry. The synthetic wavelength is obtained with a pair of tunable Nd:YAG lasers operating at 1.064 mum. The nonambiguity range of the measurement can be arbitrarily extended by subsequent measurements with different synthetic wavelengths. Experimental results from a prototype breadboard prove the feasibility of a large-nonambiguity-range, high-resolution absolute-distance meter.