The Investigation of the Fundamental Limits of Heterodyne Holographic Interferometry with the Application of Imaging Laser Generated Lamb Waves
Abstract
Currently, the field of ultrasonic nondestructive testing uses primarily piezoelectric transducers for both the generation and detection of acoustic waves. However, contact transducers have several shortcomings that have inhibited their use in some applications. The major weakness of piezoelectric transducers is that they must be in physical contact with the specimen. There are many situations where direct contact is not desirable, and in some cases, not possible. An alternate technique which has been explored and developed in his manuscript is the application of holographic interferometry to imaging acoustic waves. Past acoustic studies, involving holographic interferometry as the inspection tool, have been restricted to large amplitude waves with displacements on the order of the wavelength of light. In this treatise, heterodyne and quasi-heterodyne phase measurement techniques were employed to achieve the necessary resolution in order to image sub-fringe events. As previous researchers have shown, heterodyne holographic interferometry (HHI) can be a powerful technique in the accurate measurement of imaging full field object displacements. However, previous experimental obstacles have made HHI an impractical method for ultrasonic measurement on a diffusely reflecting surface, a requirement to make HHI a practical method in ultrasonic nondestructive testing.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1989
- Accession Number
- ADA211048
Entities
People
- James C. Wagner
- Louis C. Phillips
Organizations
- Johns Hopkins University