A Multiple Target High Precision Laser Range Measurement System Based on the FMCW Concept

Optical distance measurement systems are well suited for achieving very high measurement accuracies due to the small measurement spot. Unfortunately most of the existing commercial measurement systems suffer from their limitation to one target only. In this article an optical measurement system is described that is able to work even in complex multi target environments like in closed vessels where the measurement signal has to pass through a process window. The system is based on the FMCW concept allowing large bandwidths of more than 2 GHz. Another feature is a baseband phase-locked-loop (PLL) linearization of the frequency ramp generated inside a broadband high frequency oscillator. This PLL guarantees for a highly linear and reproducible frequency generation and thus is the basis for stable and precise measurement results. Measurements on a prototype system underline the good functionality of the concept.