Apparatus and method for performing electronic shearography
US5094528A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 25, 1990 |
| Grant date | Mar 10, 1992 |
| Priority date | — |
| Expiry date | May 25, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01L1/24
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Two laterally-displaced images of a test object interfere with each other to form a shearogram. Two shearograms, taken while the object is unstressed and stressed, respectively, are compared electronically to yield a composite interference pattern. According to the invention, each shearogram is formed by the interference of pairs of distinct rays of coherent light, reflected from different points on the object. The first ray of each pair is reflected from the object, strikes a mirror spaced from the object, and is reflected from the mirror. At the same time, the second ray of each pair is reflected from the object and strikes a beam splitter positioned beside the mirror. The beam splitter directs a portion of the second ray in the same direction as the reflected first ray, and a portion of the first ray passes through the beam splitter without being reflected. Since the two rays have the same polarization angle, and are mutually parallel, the rays interfere. A detector is positioned to receive light from the beam splitter. The detector observes the interference between pairs of rays over the entire field of view, and the result is an interference pattern, i.e. a shearogram, formed …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.