An intelligent active range sensor for vehicle guidance: system overview

The mechatronic design and the two stage calibration procedure for an eyesafe laser rangefinder, based on the lateral-effect photodiode (LEP), are presented. The sensor acquires two-dimensional range data, and is active in the sense that it can change the orientation of its field of view in order to track useful range features. An analysis of LEP operation shows that image position measurement repeatability, normalised with respect to the detector half length, is equal to the signal current to noise current ratio. This result allows accurate estimation of the variance of individual range measurements, making the sensor particularly amenable to statistically based range feature detection. Range data acquisition, range feature extraction and control of the active head behaviour are all implemented on a local network of six transputers. This parallel structure is described and it is shown how the sensor constitutes an intelligent agent in a balanced sensor suite for the guidance of close range mobile robot manoeuvres