Method for increasing the signal-to-noise ratio in non-destructive testing
US6285447A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 6, 1999 |
| Grant date | Sep 4, 2001 |
| Priority date | — |
| Expiry date | Dec 6, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/16
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The signal to noise ratio in non-destructive testing or evaluation of a sample (1) by in phase stepped optical inspection systems such as the optical shearography system using a shearing interferometer involves production of correlated speckle images successively stepped in phase by illuminating with coherent radiation a sample in an unstressed state, illuminating the sample with coherent radiation, stressing it incrementally at predetermined stress increments, and generating and capturing correlated speckle images successively stepped in phase of the incrementally stressed sample at the predetermined stress increments, using the phase stepped speckle images of the unstressed and incrementally stressed sample to calculate the phase before and after stressing and differencing the images to extract the incremental phase change, inspecting the magnitude and sign of each incremental phase change and if the phase difference between successive measurements increases by more than .pi. subtracting 2 .pi. from the measurement value or if the phase difference between successive measurements decreases by more than .pi. adding 2 .pi. to the measurement value, and calculating the phase at each …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.