Precise pulsed time-of-flight laser range finder for industrial distance measurements

Abstract

A pulsed time-of-flight laser range finder with a 1 GHz avalanche photo diode (APD) receiver and a laser pulser with ∼35 ps pulse width has been developed and tested. The receiver channel is constructed using a silicon ASIC chip and a commercially available silicon APD placed on a hybrid ceramic susbstrate. The laser pulser utilizes a single heterostructure laser operating in Q-switching mode. It is shown that the single-shot precision of the complete laser range finder is ∼2.1 mm (σ value) at best. The nonaccuracy in the distance range of 0.5–34.5 m was ∼±2 mm excluding errors caused by the statistical variations and long-term instability. The single-shot precision is clearly better than the single-shot precision of the earlier laser range finders with ∼100–200 MHz bandwidths. Also, two types of optics, coaxial and paraxial, were tested. The linearity of the coaxial optics was better, especially with a long (4 m) receiver fiber. Some possible applications of the laser range finder utilizing ps level pulses are, for example, fast three-dimensional vision in industrial environments and structure analysis of materials.