Abstract

At tripod-mounted system for making multibeam laser Doppler measurements has been constructed and is currently undergoing further development and testing. Such a system holds great promise in applications ranging from the evaluation of rock structures (a purpose for which it was originally intended) to the inspection of modern aerospace composite materials. The system has a number of unique features. It employs separate send and receive telescopes (Maksutov Cassegrain design) and an optical fiber grating (25 μm or larger optical fibers arranged in a grating or crossed gratings) located in the send scope for producing the sampling laser beams on a distant target (5–30 m or greater). The associated electronics currently processes four channels corresponding to four laser spots on the surface of interest. Measurements of the relative arrival times of an elastic wave disturbance, the peak particle velocity, and the average frequency of motion of the surface are displayed in numerical format. Experimental results on a range of targets are presented. Plans for an eight-beam, tripodmounted system, and systems with square arrays, are also described.

© 1986 Optical Society of America