Simple interferometer for monitoring Rayleigh waves

An improved interferometer for monitoring Rayleigh waves is described. Consisting of a light source, reflective grating, lens, and detector, the design is simple and inexpensive. It can be employed with specular as well as diffuse reflecting surfaces to monitor surface deformations with the sensitivity of a Michelson interferometer. By spinning the grating element, sensitivity variations with grating position are removed, resulting in stable operation. The interferometer response does vary with acoustic wavelength; a discussion of acoustic bandwidth shows that proper design can result in either a wider or narrow bandwidth response.