Patent ID: 7239397

Claim:
Device for high-accuracy measurement of dimensional changes in a test material comprising: a source for producing a measuring beam; a main beam router that divides the measuring beam into test and reference beams; a measuring loop that includes an optical pathway to the test material; a test beam router that directs both a test material-measuring portion of the test beam and an instrument-measuring portion of the test beam along a common path of the measuring loop that includes the optical pathway to the test material; the main beam router providing for recombining the test material-measuring portion of the test beam with a first portion of the reference beam and for recombining the instrument-measuring portion of the test beam with a second portion of the reference beam; a data acquisition system that converts optical path length differences between the recombined test and reference beams into processable displacement measurements relating to length variations of both the test material and the measuring loop; and a data processor that manipulates the displacement measurements to separate length variations of the measuring loop from length variations of the test material to produce a more accurate measure of the length variation of the test material.