Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1994-07-29
1997-06-03
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
G01B 1972
Patent
active
056360223
ABSTRACT:
Signals indicative of the Sagnac phase shift between counterpropagating waves in a sensing loop are combined to produce an error signal. A phase modulator is arranged to modulate the phase of optical signals that pass through the sensing loop. A phase modulator driver apparatus responsive to the error signal produces a ramp signal to drive the phase modulator to null the error signal. A reset apparatus is arranged for resetting the ramp signal to when the phase reaches a predetermined limit. The reset apparatus preferably includes a reset integrator circuit arranged to produce an output that is a ramp signal whose slope is proportional to the rotation rate of the sensing loop. A pair of comparators is arranged to determine when the reset integrator reaches one of two rollover limits. Rollover logic circuitry is connected to the pair of comparators and arranged such that when the reset integrator reaches one of the rollover limits, the integrator is forced to the other integration limit. Gating apparatus zeros the phase modulator driver during rollover transients. Rollover logic creates pulses that increment or decrement an up/down counter to provide a digital rollover count that is processed to determine the rotation rate. Scale factor circuitry corrects the rollover limits of the reset integrator if the output of the fiber optic rotation sensor is non-zero immediately following rollover.
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Litton Systems Inc.
Turner Samuel A.
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