Optical device for measuring small deformations - uses birefringent phase difference measurements to detect movement

摘要

A low power laser (1) generates a monochromatic light which passes through optical lenses (2, 3) to a separator (5) consisting of semi transparent (5) and reflecting (5') mirrors. Two parallel light beams are obtained for directing towards a transparent sample (6) on which is fixed a gauge (7) and two slits (8). The narrow beams pass to a measuring system comprising a polariser (9) and a linear birefringent system (10). It also includes an analyser of elliptical vibrations (11). The optical signals are directed to two photocells (16) for application to the input of a differential amplifier (17). Movement causes a different signal which is recorded (18). Measurements are independent of the movement of the support assembly.