Multi-Dimensional, Non-Contact Metrology using Trilateration and High Resolution FMCW Ladar

TL;DR

This paper introduces a novel multi-dimensional, non-contact metrology system using high-resolution FMCW ladar and trilateration, demonstrating 3D measurements with sub-200 micron accuracy independent of distance.

Contribution

It presents a new design combining FMCW ladar and trilateration for flexible, self-calibrating 3D metrology with experimental validation.

Findings

Achieved < 200 micron coordinate precision

Demonstrated 2D surface profiling of diffuse targets

System performance limited by laser speckle

Abstract

Here we propose, describe, and provide experimental proof-of-concept demonstrations of a multi-dimensional, non-contact length metrology system design based on high resolution (millimeter to sub-100 micron) frequency modulated continuous wave (FMCW) ladar and trilateration based on length measurements from multiple, optical fiber-connected transmitters. With an accurate FMCW ladar source, the trilateration based design provides 3D resolution inherently independent of stand-off range and allows self-calibration to provide flexible setup of a field system. A proof-of-concept experimental demonstration was performed using a highly-stabilized, 2 THz bandwidth chirped laser source, two emitters, and one scanning emitter/receiver providing 1D surface profiles (2D metrology) of diffuse targets. The measured coordinate precision of < 200 microns was determined to be limited by laser speckle issues caused by diffuse scattering of the targets.