Abstract
An optical method for measuring surface displacement in real time has been proposed by means of a system composed of two laser beams, and is discussed analytically using paraxial optics. The normalized light intensity defined by both the lights, I=(I1-I2) / (I1+I2), was expressed by I = -2(f1-f0)2 (1/q) Δf0, where f1 and f2 are the focal lengths of the first (objective) and second (focusing) lenses, q a distance between the pinhole and the focal point of the second lens for both laser beams, and Δf0 surface displacement. The above analytical result has been roughly verified by preliminary experiment, though there were differences in absolute intensity between the experimental and the analytical results. The spatial resolution of this method was expected to be about 2 μm from these analytical and experimental results.
