Patent ID: 6842254
Filing Date: 2005-01-11
Classification: G01B

Abstract:
1. A system for measuring an optical path difference in a sensing interferometer, comprising: at least one light source connectable to the sensing interferometer; a splitting means connectable to the sensing interferometer for splitting light reflected from the sensing interferometer into first and second beams; a first reference interferometer connected to the splitting means for receiving the first beam, the first reference interferometer having a predetermined optical path difference; a first detector connected to the first reference interferometer for producing a signal indicative of an intensity of light transmitted by the first reference interferometer; a second reference interferometer connected to the splitting means for receiving the second beam, the second reference interferometer having a predetermined optical path difference; a second detector connected to the second reference interferometer for producing a signal indicative of an intensity of light transmitted by the second reference interferometer; a recombining means connected to the first and second reference interferometers, for recombining light reflected from the first and second reference interferometers; and a third detector connected to the recombining means for producing a signal indicative of an addition of light recombined by the recombining means; said at least one light source having a coherence length substantially smaller than the optical path differences of the sensing and reference interferometers, and the optical path differences of the reference interferometers being different so that the signals produced by the detectors connected to the reference interferometers are substantially in quadrature, whereby the signals produced by the detectors are indicative of the optical path difference in the sensing interferometer.