Multioscillator ring laser gyroscope adaptive digitally controlled cavity length control system
AssigneeLitton Systems, Inc.
InventorsJohn G. Mark, Daniel A. Tazartes, Tae W. Hahn
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Abstract
Disclosed herein is a Digitally Controlled Cavity Length Control System comprising, in a preferred embodiment, an adaptive servo-loop for cavity length, modulation depth and amplitude control, and of the multioscillator ring laser gyroscope; thereby, permitting the simultaneous control of these elements. The cavity length control of the multioscillator, by including a variable RF detector gain, allows the operation of the gyroscope in a slightly detuned fashion to minimize magnetic sensitivity. In this manner, the multioscillator gyroscope may be maintained at a stable operating point suitable for modeling.
Claims9
A ring laser gyroscope cavity length control system, comprising, in combination:
- a ring laser gyroscope defining an optical pathway having electromagnetic propagating waves circulating among at least three corner mirrors comprising said optical pathway, at least one of which is partly transmissive, and at least one of which is movable inwardly and outwardly;
- driver means for moving said at least one corner mirror inwardly and outwardly for purposes of cavity length control;
- means for providing a controlled activation of said driver means, including:
- transducer means for measuring the intensity of electromagnetic propagating waves circulating within said gyroscope;
- servo-loop control means for controlling the movement of said at least one mirror which produces a servo-loop control signal that is a function of mirror driver voltage and the change in said electromagnetic propagating wave intensity as such intensity relates to said driver voltage;
- modulation control means for controlling the amplitude of the modulation of the servo-loop control signal of said servo-loop control means, said modulation control means additionally producing a gain control signal that is a function of said mirror driver voltage and having sensitivity to the change in said wave intensity as such intensity relates to said driver voltage;
- and,
- radio-frequency (RF) gain control means for adjusting the amplitude of a detected signal representing gyroscope intensity;
- whereby, a stable servo-loop gain is achieved for controlling said at least one mirror.
An apparatus for controlling the cavity length of a multioscillator ring laser gyroscope, comprising, in combination:
- a multioscillator ring laser gyroscope cavity defining an optical pathway sustaining at least left circularly polarized and right circularly polarized pairs of counterpropagating electromagnetic waves circulating among at least four corner mirrors comprising said optical pathway, at least one of which is partly transmissive, and at least one of which is movable inwardly and outwardly;
- means for mixing the circulating electromagnetic waves propagating in a first rotational direction, one of said waves being substantially left circularly polarized and the other being substantially right circularly polarized;
- means for sinusoidally modulating the amplitudes of said beams at a modulating frequency;
- means for detecting the amplitude modulation of said mixed beam pair;
- means for detecting the amplitude component of said amplitude modulation at said modulation frequency;
- servo-loop control means for controlling the length of said cavity in response to said amplitude modulation component at said modulation frequency;
- said servo-loop control means controlling means for adjusting the length of said cavity;
- modulation control means for controlling the amplitude of the modulation of servo-control signals produced by the servo-loop control means, said modulation control means additionally producing a gain control signal that is a second harmonic function of said mirror driver voltage and is sensitive to the change in said wave intensity as such intensity relates to said driver voltage;
- and,
- radio-frequency (RF) gain control means for adjusting the amplitude of a detected signal representing gyroscope intensity;
- whereby, a stable servo-loop gain is achieved for controlling said at least one mirror of a multioscillator ring laser gyroscope.
Dependencies are inferred from the claim text.