| 摘要 |
A fiber optic gyro can overcome the defects encountered with conventional fiber optic gyros of phase-modulation method, closed-loop system with serrodyne modulation and digital modulation. A reference phase difference DELTA beta and a ramp phase difference sigma are generated in an interference light intensity signal I by use of a triangular waveform, i.e., delta serrodyne waveform signal. The reference phase difference DELTA beta is changed to constant values DELTA beta A and DELTA beta B whose absolute values are the same and whose signs are different at every times TA and TB. A phase x of the interference light intensity signal I becomes equal to x= DELTA theta + sigma + DELTA beta . The ramp phase difference sigma is controlled so as to satisfy DELTA theta + sigma =0. Accordingly, at the stable point of the control loop, a Sagnac phase difference DELTA theta is equal to the ramp phase difference sigma . Further, a phase x of the interference light intensity signal I does not contain the Sagnac phase difference DELTA theta , and hence x= DELTA beta . Also, a fiber optic gyro can eliminate a bias, in particular, optically-generated bias. In a fiber optic gyro of phase-modulation method or delta serrodyne system, a phase controller is supplied with a phase control voltage signal VS of period T and a square wave signal V2 of period T for correcting an optical bias caused by an amplitude modulation generated by the phase control voltage signal VS in the added form. The square wave signal V2 has a constant magnitude H and is inverted in polarity at points in which the phase control voltage signal VS is maximized or minimized. The magnitude H and the polarity of the square wave signal V2 are selected such that an optical bias is minimized.
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