# US 8,570,526 B2 · Device for digitally processing information obtained from a gyrolaser and associated gyrolaser > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,570,526 B2 - Document ID: US8570526B2 - Status: Granted - Kind: B2 - Application number: 13/085,339 - Filed: 2011-04-12 - Published: 2011-10-13 - Granted: 2013-10-29 - Earliest claimed: 2010-04-13 - Assignees: Thales - Applicants: Stéphane Bouyat - Inventors: Stéphane Bouyat - Web page: https://patentgrep.com/patent/US8570526B2 ## CPC - G01C 19/66: Ring laser gyrometers - G01C 19/70: by mechanical means - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) ## Abstract A gyrolaser with optical cavity includes a plurality of mirrors, at least one photo-detector delivering two optical signals in phase quadrature, said signals being digitized. The position of one of said mirrors is controlled by conversion of an electrical signal into a mechanical force. The gyrolaser is activated in an oscillatory movement by conversion of an oscillation electrical signal into a mechanical force. The angular velocity of said gyrolaser is measured, and the phase α and the modulus ρ or the square of the modulus ρ are extracted from said optical signals. ## Claims ### Claim 1 A gyrolaser with optical cavity, comprising: a plurality of mirrors, at least one photo-detector delivering two optical signals in phase quadrature, said signals being digitized, means for controlling a position of one of said mirrors by conversion of an electrical signal into a mechanical force, means for activating said gyrolaser in an oscillatory movement by conversion of an oscillation electrical signal into the mechanical force, means for measuring an angular velocity of said gyrolaser, means for extracting a phase α and a modulus ρ or a square of the modulus ρ of a vector whose real part is formed by one of the two digitized signals and an imaginary part is formed by the other digitized signal, said modulus ρ representing an amplitude of said optical signals and its square representing their power, means for locking a length of the optical cavity onto a multiple of a wavelength of said optical signals by an estimation of a slope of a curve of variation of the amplitude or of the power as a function of time, said means producing a correction signal determined as a function of said slope and applied to said control means, a derivator applied to the phase a over a given period of time in order to produce a signal comprising an overall movement information, including an oscillatory movement, for said gyrolaser, and means for locking an activation of said gyrolaser onto said oscillatory movement, receiving said signal, extracting from which an estimation of the oscillatory movement imparted on said gyrolaser by said activation means and producing said oscillation signal whose amplitude is locked onto a given amplitude setpoint. ### Claim 2 (depends on 1) The gyrolaser according to claim 1, wherein the extraction of an estimation of the oscillatory movement is performed by a filtering eliminating, from said signal, the low frequencies below a given threshold. ### Claim 3 (depends on 2) The gyrolaser according to claim 2, wherein said activation locking means further comprise: means for rectifying said estimation of the oscillatory movement, means for subtracting the result of the rectification from an oscillation amplitude setpoint, means for integrating the result of the subtraction over a given time period, and means for multiplying the result of the integration with said estimation phase-shifted by a given phase θ to obtain said oscillation signal. ### Claim 4 (depends on 3) The gyrolaser according to claim 3, wherein the phase shifting is performed by a phase-shifting filter or a phase-locked loop. ### Claim 5 (depends on 4) The gyrolaser according to claim 4, wherein said phase θ has a value of 180° or 90°. ### Claim 6 (depends on 5) The gyrolaser according to claim 5, wherein said means for locking the length of the optical cavity carry out at least the following steps: addition of a reference sinusoidal signal of given frequency and amplitude to the correction signal for said means for controlling the position of a mirror of said cavity, and coherent demodulation of the amplitude or of the power of said signals. ### Claim 7 (depends on 6) The gyrolaser according to claim 6, wherein the coherent demodulation is performed by the following steps: multiplication of the amplitude or of the power of said signals by said sinusoidal signal of given frequency and amplitude, integration of the result of the multiplication over a given time period, and addition of the result of the integration and of said sinusoidal signal to produce said correction signal. ### Claim 8 (depends on 7) The gyrolaser according to claim 7, wherein said extraction means execute a Cordic algorithm in a Y-reduction mode. ### Claim 9 (depends on 8) The gyrolaser according to claim 8, wherein said square of the modulus p is filtered by a low-frequency filter. ### Claim 10 (depends on 9) The gyrolaser according to claim 9, further comprising automatic gain control means for locking the amplitude or the power of said signals onto a reference gain value. ### Claim 11 (depends on 10) The gyrolaser according to claim 10, wherein said control means comprise a piezo-transducer. ### Claim 12 (depends on 11) The gyrolaser according to one claim 11, wherein said activation means comprise a mechanical activation wheel and a piezoelectric motor. ### Claim 13 (depends on 12) The gyrolaser according to claim 12, wherein said measurement means carry out a counting/downcounting of the pulses of said signals. ### Claim 14 (depends on 13) The gyrolaser according to claim 13, wherein it performs a measurement of the angular velocity according to the three axes of a trihedron and the means for locking the length of the optical cavity further comprise a matrix-producing operation making it possible to transpose the reflection axes of the mirrors of the optical cavity towards the optical axes of the photo-detectors. ### Claim 15 (depends on 14) The gyrolaser according to claim 14, wherein the extraction of an estimation of the oscillatory movement is determined from the intercorrelation matrix of the three signals obtained by derivation of the phase a of said optical signals obtained for each of the three axes.