Abstract
The ability to find small voids in acoustically excited solid specimens using coherent optical detection methods is limited by three factors: available ultrasonic power levels; noise elements; and nonlinear properties of the working materials. Detection sensitivity constraints due to power limitations are established here. A void embedded in an elastic half-space is used as a physical model. Free surface deformations due to internal void-scattered ultrasonic waves are computed for select cases. Deformations are too small for direct optical measurement. Deflections of a liquid layer free surface above the elastic half-space represent an amplified copy of the elastic boundary deformation and improved detection sensitivity. Holographic techniques with noise reduction features to observe the liquid surface profile are discussed.
© 1974 Optical Society of America
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