Vibration analysis using shadow speckle metrology and line broadening techniques.

This paper describes the application of two different computer- based optical methods for locating the positions and amplitudes of nodes and antinodes in vibrating members, In a technique called "shallow speckle metrology," artificial speckles are projected at an angle onto a vibrating surface using a 35 mm slide projector and a spedkled slide. In the second technique, called "line broadening, "line broadening, "a single line is projected onto the vibrating test surface. In both techniques the vibrating surface and the projected images are captured either directly using a vidicon camera/digitizer system, or indirectly using an ordinary camera to record a time-average photo-graph which are subsequently digitized. Computer programs compare these images with images recorded prior to excitation in order to determine the mode shape and the amplitude of vibration.