Asymmetrical dual reference beam method for contactless measurement of speed of materials using hand-held sensor, by determining difference between signals from two reference beam interferometers

摘要

A sensor consists of two asymmetrically arranged reference beam interferometers. The two reference beam interferometers illuminate the material to be measured at an oblique angle to the surface and with a constant intermediate angle of less than 90 deg . By determining the difference between the two signals generated, the dependence of the speed measurement on the illumination angle is eliminated.