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CMOS-compatible three-dimensional image sensing using reduced peak energy

  • US 6,587,186 B2
  • Filed: 06/06/2001
  • Issued: 07/01/2003
  • Est. Priority Date: 06/06/2000
  • Status: Expired due to Term
First Claim
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1. A method to determine distance z between a pixel detector and a target, the method comprising the following steps:

  • (a) illuminating said target with optical energy having a periodic waveform that includes a high frequency component S1

    ·

    t);

    (b) disposing said pixel detector so as to detect an optical energy signal having a high frequency component S2

    ·

    t)=A·

    S1

    ·

    t−

    Φ

    ) reflected from said target, where A is a coefficient proportional to brightness of said target, and Φ

    is phase shift proportional to time-of-flight of light over said distance z; and

    (c) homodyne signal-processing said signal S2

    ·

    t) to generate a phase signal Φ

    proportional to said distance z and to preserve said coefficient A;

    wherein homodyne signal-processing at step (c) is carried out using an internally generated signal whose frequency is derived from said S1

    ·

    t) and whose phase is dynamically forced by closed loop feedback to track said high frequency component S2

    ·

    t).

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