Calibration method for initial position of miss distance in femtosecond laser tracker

A femtosecond laser tracker achieves target tracking through detection of miss distance via a PSD. The location of reflected laser spot on PSD when tracking laser exactly points to center of the retro-reflector, named initial position of miss distance, was the benchmark of miss distance calculation. So it was important to precisely calibrate initial position of miss distance in order to achieve high accurate measurement. A calibration method for initial position of PSD based on the retro-reflector feature analysis was presented in this paper. First, the error factors that may impact miss distance calibration were analyzed, and the mathematic model was established. Then, according to the laser tracker's structure design and the geometric errors of axes, the calibration method for the initial position was simulated. Results show that the calibration error was limited below 17.8 m, which means when the retro-reflector was placed at a distance of 10 m from the tracker, the laser tracker's pointing error was limited below 1.1. These results can be helpful in further error compensation model. At last the proposed calibration method of initial position of miss distance was applied to the self-developed femtosecond laser tracker, and provides the benchmark for further dynamic measurement.