Apparatus and method for enhancing the quality of a video signal produced by electronic shearography
US5091776A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 8, 1990 |
| Grant date | Feb 25, 1992 |
| Priority date | — |
| Expiry date | Nov 8, 2010 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01L1/24
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The purpose of the present invention is to improve the quality of a video signal generated by the method of nondestructive testing known as electronic shearography. In electronic shearography, two laterally-displaced images of a test object are made to interfere, and the interference pattern is stored. Another such interference pattern is obtained while the object is stressed. The two patterns are compared by computer, such as by subtracting one pattern from the other, and the resulting composite pattern is displayed on a video monitor or equivalent. According to the present invention, the subtracted signal is connected to a rectifier circuit which causes both positive-going and negative-going variations in the video signal to become positive-going variations. Thus, any changes in the intensity of the signal, due to phase changes resulting from deformation of the object, are displayed as increases in brightness of a pixel on the final display. If a point on the object has not moved due to the applied stress, the pixels representing that point remain dark. The present invention therefore produces an image having a greater resolution than is possible using the methods of the prior ar…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.