# US 5,347,360 A · Ring laser gyro > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,347,360 A - Document ID: US5347360A - Status: Granted - Kind: A - Application number: 07/415,924 - Filed: 1989-09-13 - Granted: 1994-09-13 - Earliest claimed: 1982-08-27 - Assignees: Ratheon Company - Inventors: Michael Holz - Web page: https://patentgrep.com/patent/US5347360A ## CPC - G01C 19/661: {details} - 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 ring laser gyro uses means for shaping the gas flow, which inevitably develops as a result of a DC discharge, to optimize the effect of the Fresnel-Fizeau drag on the output signal of the gyro. In one embodiment, a sufficient component of the gain medium flow is provided to produce a substantially constant Fresnel-Fizeau component of the output signal even in the presence of variations of the discharge current. In another embodiment, a sufficient component of gain medium flow is provided to substantially eliminate the Fresnel-Fizeau component of the output signal at a predetermined level of discharge current. ## Claims ### Claim 1 A method of operating a ring laser gyro, wherein a discharge current is used in a gain medium to produce a beam of electromagnetic energy and an output signal is produced in response to rotation of the ring, the interaction of the beam with said discharge producing a bias component in said output signal, comprising the steps of: providing a bypass path in said ring; and controlling the flow of the gain medium through said ring and said bypass path to substantially eliminate said bias component due to the interaction of said beam with a predetermined level of said discharge current. ### Claim 2 A method of operating a ring laser gyro, wherein a discharge current is used in a gain medium to produce a beam of electromagnetic energy and an output signal is produced in response to rotation of the ring, the interaction of the beam with said discharge current producing a bias component in said output signal, such bias component nominally varying with variations in said discharge current, comprising the steps of: providing a bypass path in said ring; and controlling the flow of the gain medium through said ring and said bypass path to produce a bias component substantially invariant with respect to variations in the discharge current. ### Claim 3 In combination: means for providing a resonator, said resonator comprising a ring path and a bypass path in said ring path; means for providing a beam of electromagnetic energy comprising a gain medium in said resonator and means for providing a discharge current in said gain medium, the interaction of said beam with said discharge producing a frequency difference between counter-propagating beam components; and means for producing a gain medium flow through said ring path and said bypass path which substantially eliminates said frequency difference for a predetermined discharge current. ### Claim 4 In combination: means for providing a resonator, said resonator comprising a ring path and a bypass path in said ring path; means for producing a beam of electromagnetic energy comprising a gain medium in said resonator and means for providing a discharge current in said gain medium, the interaction of said beam with said discharge producing a frequency difference between counter-propagating beam components, the amount of such produced frequency difference nominally being a function of the discharge current; and means for producing a predetermined gain medium flow through said ring path and said bypass path selected to maintain the amount of said frequency difference substantially constant over a predetermined range of the discharge current. ### Claim 5 A ring laser gyro comprising: means for producing a predetermined ring path having a bypass path; means for producing counter-propagating beams in said path, such beam producing means comprising: a gain medium; and, means for generating a predetermined electrical current in said medium producing a gain medium flow; means, responsive to rotation of the ring path, for producing an output signal having a bias component, interaction between the counter-propagating beams and the electrical current producing said bias component in said output signal; and means for controlling the gain medium flow in said path and said bypass path substantially eliminating said bias component for said predetermined electrical current in said gain medium. ### Claim 6 (depends on 5) The ring laser gyro of claim 5 wherein said current generating means produces a predetermined level of current distribution. ### Claim 7 (depends on 5) The ring laser gyro of claim 5 wherein said current generating means produces a balanced current distribution in said path. ### Claim 8 A ring laser gyro comprising: means for producing a predetermined ring path having a bypass path; means for producing counter-propagating beams in said path comprising a gain medium and means for generating a predetermined electrical current in said medium; means for producing an output signal indicative of rotation of said ring path, said output signal having a bias component due to the interaction of said beam with said discharge current, said bias component nominally varying with variations in said predetermined electrical current; and means for providing a gain medium flow in said path and said bypass path, said flow being controlled to maintain said bias component substantially constant substantially independent of variations of said current. ### Claim 9 A ring laser gyro comprising: means for producing a predetermined ring path having a bypass path; means for producing counter-propagating beams in said path comprising a gain medium and means for generating an electrical current in said path; means for producing an output signal in response to rotation of said ring path, the interaction of said beams with said current producing a bias component in said output signal; and means for providing a gain medium flow in said path and said bypass path, said flow being controlled to substantially eliminate said bias component at a predetermined level of said electrical current.