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Processing arrangement for optical rate sensor

  • US 5,262,843 A
  • Filed: 04/28/1992
  • Issued: 11/16/1993
  • Est. Priority Date: 04/21/1986
  • Status: Expired due to Term
First Claim
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1. An optical rate sensor for use in inertial reference systems to detect angular rotation and measure magnitude and directional sense of the rate of angular rotation, said rate sensor comprising:

  • a passive ring Sagnac interferometer wherein a pair of counter-propagating optical waves are transmitted in opposite directions through a ring path and emerge therefrom with a relative Sagnac phase shift indicative of said rate of angular rotation, said interferometer comprising combining means for recombining said counter-propagating waves wherein the resultant low order fringe pattern is representative of the relative phases of said counter-propagating waves;

    phase modulation means connected to said interferometer for externally applying to said counter-propagating waves a non-reciprocal phase shift;

    circuit means connected to said interferometer for generating an intensity signal indicative of said resultant low order fringe pattern; and

    measuring means connected to said circuit means for measuring said intensity signal and generating an output signal corresponding to said rate of angular rotation;

    characterized in that;

    said measuring means comprises;

    demodulation means responsive to said intensity signal for demodulating said intensity signal and for generating a phase error signal;

    integration means connected to said demodulation means for integrating said phase error signal and for generating a corresponding integrated phase error signal;

    analog-to-digital converter means for converting said integrated error signal into a digital error signal corresponding thereto;

    central processing means responsive to said digital error signal and to clock signal to estimate the true value of said integrated phase error signals by combining past and present measurements of said signals, such that mean square errors between true and expected values thereof are minimized, and for generating a control signal representative thereof;

    modulation means for modulating said control signal so as to apply a level adjusted AC signal to said phase modulation means, and for generating a modulated reference signal;

    adder means for summing a period time-variant AC bias signal with said modulated reference signal, and for generating a modulator control signal, said control signal representative of the relative Sagnac phase shift of said pair of counter-propagating waves.

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