High-resolution displacement measurement using mode interference in the optical waveguide

Using an optical waveguide, high-resolution displacement measurement is achieved for the first time. The measurement principle is based on the interference between the two (even and odd) modes in the double-mode waveguide. After the light from a laser diode is focused onto the object to be measured, the wavefront gradient of the reflected light is detected using a Ti-indiffused LiNbO/sub 3/ channel waveguide. Although this optical measurement system is very simple, very high resolution (of less than 1 mn) is obtained. Besides, the characteristics of the measurement system do not depend on the surface condition of the object.