Full Field Visualization of Propagating Surface Acoustic Waves

摘要

The objective of this research effort is to apply optical holographic techniques coupled with electronic processing techniques for providing a several orders of magnitude more sensitive method for full field visualization of low amplitude (order of Angstroms) acoustic waves propagating along the surface of a solid body. A third generation heterodyne system has been constructed with a demonstrated temporal capability for measuring out of plane displacements with a resolution of better than 1/1500 of a fringe (Previous configurations provided resolutions to 1/900 of a fringe or about 3 Angstroms). Pulsed heterodyne holographic interferometry of large amplitude acoustic waves propagating over an aluminum test specimen and interacting with a machined slot defect was successfully demonstrated. This new readout system is extremely flexible in that it incorporates two acoustooptic (Bragg) cells with electronics to permit either frequency shifting for true heterodyning or phase shifting for phasestepped, quasi-heterodyne holographic interferometry.