Optical interference measurement using multiple mode wave-guide - has conductive and dielectric layers with two laser beams fed in to produce interference energy pattern to activate photodiode array

摘要

The multiple mode wave guide comprises a carrier (1), a wave conductor (2) and dielectric film top coating (3), the reflective index of which is less than that of the wave conductor. At one end of the wave-guide is fitted a coupling grid (4). A first laser beam (5), operating in the TE(O) mode is fed into the wave conductor. A second laser beam , (6), is introduced and develops a wave operating in the TE(1) mode. The wave conductor required to have characteristics such that the effective refractive indices in the TE(O) and TE(1) modes have a very small difference, and thus the two waves interfere and produce energy peaks which may be detected by an array of photodiodes (9-16). The device may be used for small angle or displacement measurements.