Applications of high resolution and accuracy frequency modulated continuous wave LADAR

Abstract

The high resolution frequency modulated continuous wave (FMCW) laser and detection ranging (LADAR) system developed by Spectrum Lab and Bridger Photonics Inc. could be potentially used for volume metrology purposes. However, comparisons with other length metrology methods would help to determine its actual precision and accuracy. An ultra-low phase noise and narrow bandwidth laser centered at 1536nm is used to build a displacement tracking interferometer for comparisons. Lock-in detection based on phase modulation is used to reduce sensitivity to amplitude noise. The data is processed to obtain an accurate displacement measurement with a novel fringe counting technique that provides resolution higher than lambda/4. After calibrating and figuring out the stability of the FMCW LADAR, its ranging capability is determined by comparison with these results along different wavelength regions. Furthermore, we propose a combination of the trilateration techniques with the FMCW LADAR system for accurate 2D metrology. This idea is developed from design to implementation stages. Surface profiles of non-cooperative diffuse targets using lasers sources with different optical bandwidths are presented. A photon budget and an error analysis of the experimental results are also included.