TABLE OF CONTENTS This term is applied to those classes of gyroscope which use the properties of electromagnetic radiation to sense rotation. Such devices often use the visible wavelengths, but it is also possible to operate in the near infrared. Some mechanical gyroscopes use optical angle pick-off sensors, but for this discussion they are not classed as optical gyroscopes. Optical gyroscopes use an interferometer or interferometric methods to sense angular motion. In effect, it is possible to consider the electromagnetic radiation as the inertial element of these sensors.
It was during the late nineteenth century that Michelson pioneered work with optical interferometers, although his goal was not to produce an optical gyroscope. In 1913, the Sagnac effect was reported [1] and this is the fundamental principle on which optical gyroscopes are based. When light travels in opposite directions (clockwise and anti-clockwise) around an enclosed ring, differences arise in the apparent optical length of the two paths when the ring is rotated about an axis orthogonal to the plane containing the ring. In 1925, this concept was applied by Michelson and Gale [2] in Chicago using a ring gyroscope with a perimeter of over one mile. By sending ordinary light through evacuated water pipes, they were able to detect the shift produced by the rotation of the Earth.
Further impetus to produce an optical sensor resulted from the demonstration of a laser by Maiman in 1960 [3]. These devices produce a well collimated and highly monochromatic source of electromagnetic...
