DIFFERENTIAL LASER GYRO DEVELOPMENT

J. Bresman, H. Cook and D. Lysobey

Peer Reviewed

Abstract:	The Differential Laser Gyro (DILAG) is a significant advancement in strapdown inertial guidance. Its four simultaneously oscillating modes allow it to retain the advantages inherent in a laser gyro without many of the drawbacks found in present two mode units. The DILAG concept employs two complete laser gyros operating in the same optical cavity. The gyros are distinguished from each other by their polarization state; one is right circularly polarized (RCP), while the other is left circularly polarized (LCP). Both gyros are biased out of their respective dead-band regions by the same Faraday cell. Because of their opposite polarization states, the gyros respond with equal but opposite frequency shifts to a given rotational input rate. When one gyro output is subtracted from the other, the result is a doubling of rate sensitivity combined with a cancellation of the common Faraday bias. Operated in this manner, the DILAG becomes insensitive to variations in the Faraday bias and thereby eliminates the usual requirements for Faraday cell stability. In addition the DILAG requires no dithering, either mechanical or electrical. This paper considers these points as well as a number of other special characteristics of the DILAG which offer significant improvements in gyro performance. Among those areas discussed are the reduction in shielding requirements, the elimination of all moving parts including those associated with cavity length control, and the advantages occurring in data collection and self check capability.
Published in:	NAVIGATION: Journal of the Institute of Navigation, Volume 24, Number 2
Pages:	153 - 159
Cite this article:	Bresman, J., Cook, H., Lysobey, D., "DIFFERENTIAL LASER GYRO DEVELOPMENT", NAVIGATION: Journal of The Institute of Navigation, Vol. 24, No. 2, Summer 1977, pp. 153-159.
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