IDENTIFICATION OF ANTINODES AND ZERO-SURFACE-STRAIN CONTOURS OF FLEXURAL VIBRATION WITH TIME-AVERAGED SPECKLE PATTERN SHEARING INTERFEROMETRY

A new time-averaged frame subtraction technique is introduced for vibr ation analysis by digital speckle shearing interferometry. The techniq ue permits the enhancement of fringes by subtracting two Bessel fringe patterns at different forcing levels. Compared with the phase-shift m ethod, this method is more efficient and easier to implement for quali tative vibration measurement, providing a means for fast inspection of plate vibration behavior. It is also capable of tracing contours of z ero strain and locating antinodes on vibrating plates. (C) 1997 Optica l Society of America.