Closed loop fiber optic rotation sensor

US4662751A · kind A · utility

Assignee

• The United States of America as represented by the Administrator of the National Aeronautics and Space Administration · US

Inventors

• Willis C. Goss · Altadena, US
• Bruce Youmans · Sierra Vista, US
• Noble M. Nerheim · Arcadia, US
• Randall K. Bartman · Altadena, US

Key dates

• Filing date: Sep 24, 1985
• Grant date: May 5, 1987
• Expiry date: Sep 24, 2005

Classification

• Technology area (CPC G): Physics
• CPC primary: G01C19/726
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

An improved optical gyroscope is provided, of the type that passes two light components in opposite directions through an optic fiber coil, and which adds a small variable frequency to one of the light components to cancel the phase shift due to rotation of the coil. The amount of coil rotation from an initial orientation, is accurately determined by combining the two light components, one of which has a slightly increased frequency, to develop beats that each represent a predetermined angle of rotation. The direction of rotation is obtained by combining the two light components on a photodetector, intermittently phase shifting a single light component by 90.degree., and comparing the direction of change of photodetector output (+ or -) caused by the 90.degree. shift, with the slope (+ or -) of the photodetector output at about the same time, when there is a 90.degree. shift.