Polarization optics design for a laser tracking triangulation instrument based on dual-axis scanning and a retroreflective target

Abstract

The design of the polarizing optics of an instrument that uses laser tracking triangulation for the dynamic measurement of the 3-D coordinates of a retroreflective target is presented. The system, which uses dual-axis scanning mirrors, has applications in the performance testing and calibration of industrial robots. Analytical and experimental results are provided for the design of the polarizing scheme to maximize beam-energy usage for a given safety classification while minimizing any unwanted laser feedback and secondary beams that can affect measurement precision. Finally, a study of the depolarizing effects of air-path retroreflectors shows how severe degradation of measurement accuracy can result from their use in this context, which thus supports the alternative use of a cat's-eye type target.