Integrated optical sensor measuring distance to object - has polariser and quarter lambda plate passing reference and measuring beams

摘要

An integrated opto-electrical sensor for measuring a clearance distance between itself and an object (30) has a lithium niobate crystal substrate (2) on whose upper surface are formed three optical waveguides (6, 7, 8) by titanium diffusion. The central waveguide (6) receives light from a laser diode (31) and is branched (6' 6") to effect a coupling with the two outer waveguides (7,8). The combination thus forms the measurement and reference paths of a double Michelson interferometer having a polariser (27), the electro-optical phase modulators (20, 21) and the reflectors (25, 26). The interference signals resulting from dissimilar optical path lengths are converted by the photodetectors (36, 37) for electronic evaluation (38). USE/ADVANTAGE - Provides accurate measurements at moderate expense. Operates within power limitations of normal semiconductor laser diode.