High-precision, high-accuracy, single-hub laser scanner

Abstract

A laser scanner determines the direction and distance of one or more targets by emitting two substantially parallel beams and receiving respective return beams. Components for handling the received beams are affixed to a monolithic block to ensure fixed relative placement. The direction of the target is determined using an optical encoder to reduce the timing window for interpolation to a fraction of the time it takes for the scanner to make a full revolution. A PLL trained by recent segment timing further improves accuracy and precision. A detection algorithm adapts detection thresholds for the different signatures of return signals depending on the distance to the target. Distance calculations are also adjusted for thermal expansion of the scanner components by including a temperature-variant thermometer output signal in the distance calculation algorithm.