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Method and system to avoid inter-system interference for phase-based time-of-flight systems

  • US 7,405,812 B1
  • Filed: 05/14/2007
  • Issued: 07/29/2008
  • Est. Priority Date: 05/18/2006
  • Status: Active Grant
First Claim
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1. 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 P12 between detected signals from said first TOF and said second TOF system is reduced while substantially maintaining first TOF detection accuracy.

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