Phase-multiplication holography
This disclosure relates generally to nondestructive testing for identifying structural characteristics of an object by scanned holographic techniques using a known source of radiation, such as electromagnetic or acoustical radiation. It is an object of this invention to provide an apparatus and method for synthetic aperture expansion in holographic imaging applications to construct fringe patterns capable of holographic reproduction where aperture restrictions in nondestructive testing applications would conventionally make such imaging techniques impossible. The apparatus and method result in the production of a sharply defined frontal image of structural characteristics which could not otherwise be imaged because they occur either near the surface of the object or are confined by geometry restricting aperture dimensions available for scanning purposes. The depth of the structural characteristic below the surface of the object can also be determined by the reconstruction parameters which produce the sharpest focus. Lateral resolution is established by simulated reduction in the radiation wavelength and may easily be an order of magnitude less than the electromagnetic wavelength in the material or 2 times the standard depth of penetration. Since the phase multiplication technique is performed on the detected data, the penetration depth available due to the longer wavelength signals applied to the test object remains unchanged. The phase multiplication technique can also be applied to low frequency acoustic holography, resulting in a test which combines excellent penetration of difficult materials with high resolution images.
- DOE Contract Number:
- AC06-76RL01830
- Assignee:
- Dept. of Energy
- Patent Number(s):
- PATENTS-US-A342431
- Application Number:
- ON: DE83002364
- OSTI ID:
- 6717339
- Country of Publication:
- United States
- Language:
- English
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