A Wide-field Scanning Triangulation Rangefinder for Machine Vision

Abstract

This paper describes the design, construction, and measured performance of an experimental scanning laser rangefinder. The instrument uses active triangulation and employs an optical bandpass filter to minimize the effects of ambient illumination. Its use of a single photodetecting element, a photomultiplier, is a unique feature among scanning triangulation rangefinders. A novel scanning configuration based on spherical coordinates is employed, resulting in an extremely large field of view. Nearly 75% of the surrounding solid angle is accessible. Reasonably high speed and accuracy are obtained. The typical error in range at a range of 50 in. is .12 in. The typical error in either of the two angular coordinates is .03°. The maximum instantaneous rate of acquisition of range samples is 500 Hz. Much higher speed and accuracy appear achievable with various modifications and improvements. This type of rangefinder appears most useful in automatic surveillance and robot navigation applications, because of its large field of view.