Transportable Distance Measurement System for Long-Range Applications

This paper describes a transportable distance measurement system based on synthetic wavelength interferometry using two frequency-doubled Nd:YAG lasers. To eliminate polarization crosstalk issue, a different system has been set up from those usually described in the literature. Indeed, we propose a system where the different beams are spatially separated instead of being polarization-separated. Furthermore, the superheterodyne detection is partly software-implemented to measure the synthetic phase, enabling an angular resolution of ~ 2π/5600 in the fringe pattern. A first assessment of the system has consisted in an indoor comparison on a 3-m-long displacement bench, successfully resulting in ~ 4 μm accuracy. Then, the system has been further modified for an indoor comparison over 25 m. Recent measurements are given, limited by now by the pitch angle of the displacement bench used for the comparison.