Method and apparatus for measuring angular rate with a passive optical resonator

Claim 3

A method as defined in claim 1 further including the step of calculating the optical length of said resonator, temperature and scale factor of the angular rate measurement as the sum of said weighted frequency differentials.

Claim 4

Apparatus for reading out angular rates with a passive optical ring resonator, said apparatus comprising, in combination: (a) means for generating a beam of coherent light whose frequency is a first resonant mode of said ring resonator; (b) means for dividing said beam into first, second and third component beams; (c) a first frequency shifting device responsive to a first control signal for tuning the frequency of said second beam to a lower distinct resonant mode of said resonator; (d) a second frequency shifting device responsive to a second control signal for tuning the frequency of said third beam to a higher distinct resonant mode of said resonator; (e) a coupler for radiating said first beam into said ring resonator whereby said first beam alternately counterrotates simultaneously with said second and third beams; (f) a first photodetector arranged to detect said first component beam after it is radiated out of said resonator and to form an output electrical signal responsive thereto; (g) a second photodetector arranged to detect said second and third component beams after they are radiated out of said resonator and to form output electrical signals responsive thereto; (h) a control circuit responsive to said output signals for forming said first and second control signals; and (i) an evaluation circuit responsive to said first and second control signals, said evaluation circuit being arranged to determine angular rate as the weighted difference of the frequency differentials between said first and second counterrotating beams and between said third and first counterrotating beams.

Claim 5

Apparatus for reading out angular rates with a passive optical ring resonator, said apparatus comprising, in combination: (a) means for generating a beam of coherent light whose frequency is a first resonant mode of said ring resonator; (b) means for dividing said beam into first, second and third component beams; (c) a first frequency shifting device responsive to a first control signal for tuning the frequency of said second beam to a lower distinct resonant mode of said resonator; (d) a second frequency shifting device responsive to a second control signal for tuning the frequency of said third beam to a higher distinct resonant mode of said resonator; (e) a coupler for radiating said first beam into said ring resonator whereby said first beam alternately counterrotates simultaneously with said second and third beams; (f) a first photodetector arranged to detect said first component beam after it is radiated out of said resonator and to form an output electrical signal responsive thereto; (g) a second photodetector arranged to detect said second and third component beams after they are radiated out of said resonator and to form output electrical signals responsive thereto; (h) a control circuit responsive to said output signals for forming said first and second control signals; and (i) an evaluation circuit responsive to said first and second control signals, said evaluation circuit being arranged to determine angular rate as the weighted difference of the frequency differentials between said first and second counterrotating beams and between said third and first counterrotating beams.

Claim 6

Apparatus as defined in claim 3 further characterized in that said ring resonator comprises a fiber ring of strongly birefringent, polarization-maintaining monomode fiber.

Claim 7

Apparatus as defined in claim 3 further characterized in that said ring resonator comprises a fiber ring of strongly polarizing light conducting fiber.

Claim 8

Apparatus as defined in claim 3 further characterized in that said ring resonator includes a polarizer.

Claim 9

Apparatus as defined in claim 3 wherein said ring resonator comprises a resonant cavity.

Claim 10

Apparatus as defined in claim 7 wherein said resonator further includes three mirrors.

Claim 11

Apparatus as defined in claim 7 wherein said resonator further includes four mirrors.

Claim 12

Apparatus as defined in claim 3 wherein said ring resonator, coupler and frequency shifting devices are fabricated in integrated optics.

Claim 13

Apparatus as defined in claim 3 wherein said first and second frequency shifting devices comprise Bragg cells.

Claim 14

Apparatus as defined in claim 3 wherein said first and second frequency shifting devices comprise an acousto-optical modulator including two acoustical exciters.

Claim 15

Apparatus as defined in claim 3 wherein said first and second frequency shifting devices comprise a Bragg cell having a plurality of frequency-drive arrangements associated therewith.

Claim 16

Apparatus as defined in claim 3 wherein said means for dividing and said frequency shifting devices consist of an acousto-optical modulator operating in the Raman-Nath region.

Claim 17

Apparatus as defined in claim 3 further including means engaged to said first and second frequency shifting devices for alternately radiating said second and third beam into said ring resonator at a preselected frequency.

Claim 18

Apparatus as defined in claim 15 wherein said last-named means comprises a pair of diaphragms.

Claim 19

Apparatus as defined in claim 16 wherein said diaphragms are electromagnetically controlled.

Claim 20

Apparatus as defined in claim 17 wherein said diaphragms are piezoelectrically controlled.

Claim 21

Apparatus as defined in claim 3 including means for modulating said second and third beams so that said beams can be separated by appropriate filtering of said output electrical signals.