Patent ID: 7405812

Claim:
In a first time-of-flight (TOF) detection system that emits time modulated optical energy and examines phase shift in a fraction of said optical energy reflected by a target object to determine distance Z therebetween, a method of reducing potential interference from an adjacent second TOF system also emitting optical energy, the method comprising: generating for said first TOF system a clock signal having long term frequency stability while exhibiting at least one characteristic selected from a group consisting of (a) a signal having a temporally imperfect waveform, (b) a signal having a substantially imperfect periodicity, (c) a signal including at least pseudo-random clock noise, (d) a signal including random clock noise, (d) a signal whose frequency hops between at least two discrete frequencies, (e) a signal whose frequency hops randomly between at least two discrete frequencies, and (f) a clock whose frequencies are characterized by a spread spectrum; wherein a cross-correlation product P 12 between detected signals from said first TOF and said second TOF system is reduced while substantially maintaining first TOF detection accuracy.