Time-of-flight delay-line laser telemeter

Abstract We propose a new telemeter scheme for absolute distance measurements, based on the optoelectronic emulation of a semiconductor ring laser working in a suitable bistable regime. The feedback provided by a moveable external reflector (defining the measuring arm) and by a short electronic delay line, generates electrical switching in the circuit, the period of which is linearly related to the distance of the measuring arm reflector. This telemeter is not affected by the ambiguity problem. It requires only a single laser diode and a photodiode, in a simple optical arrangement, and low-cost electronic circuitry. Experiments have been performed both on a fiber path and in the air.