Novel design of ball-lens-based laser tracker using pulsed interferometer

Abstract

A new laser tracker using an optical frequency comb with ball lenses as a reference and targets is proposed. In this system, high-accuracy absolute length measurement based on pulsed interferometry of an optical comb is utilized. By using a ball lens with a refractive index of 2.0 as a reference, it can avoid the error caused by reference point displacement. As targets, ball lenses have a wider acceptance angle than a conventional retroreflector. In this work, two new designs of the laser tracker are proposed. The simulation and experimental investigation of the refractive index characteristics of a ball lens were examined to obtain the optimal parameters for each design. Using these designs, the one-axis absolute length measurement of as much as 10 m was performed, and its combined uncertainty was evaluated to be [(0.145 µm)2 + (3.05 × 10−7 l)2]1/2, where l is measured length.