SIGNAL RESPONSE OF A LASER-BEAM SCANNER

A laser beam scanner, used as an angle measuring device in a particula r navigation system for mobile robots, has been developed. It measures heading angles to beacons made of vertical stripes of retroreflective tape. Expressions giving the received power and energy in the pulse, which is generated when a beacon is traversed by the laser beam, are g iven. Measurements support the derived expressions. The shape and ampl itude of the pulse are functions of the range R to the beacon, but at long range the pulse shape and width become independent of range while the dependence of the received amplitude on range becomes R-3. At lon g range the pulse shape is determined by the Gaussian irradiance distr ibution in the laser beam and the pulse width is governed by the laser beam divergence and the scanning speed. Design rules for the optimum field of view of the receiving optics and for an electrical filter, wh ich maximizes the signal-to-noise ratio, are proposed. An expression g iving a conservative estimate of the signal-to-noise ratio is derived.