Apparatus and method for shearographic inspection and non-destructive testing of articles in a vacuum chamber
US6246483A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 2, 1999 |
| Grant date | Jun 12, 2001 |
| Priority date | — |
| Expiry date | Dec 2, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B11/162
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Disclosed is an apparatus and method for inspecting or testing a sample using shearography techniques. A laser shearing interferometer includes: a source of coherent radiation, a line generator producing a line of coherent radiation from said source, a line scanner scans the line of coherent radiation over the sample, a shearing element generates two laterally displaced images of the sample, and phase stepper or ramper steps or ramps the phase of one of the two images. A video camera views images of the sample and provides corresponding video output signals. An image processor receives the video output signals and extracts therefrom the frame rate of the camera in substantially realtime. A signal generator provides the stepper and the line scanner, a signal substantially in phase with the frame rate of the camera, a decoder is used for phase extraction and a vacuum chamber contains the laser shearing interferometer and the sample under test. A pressure control varies the pressure within the vacuum chamber between several predetermined pressure values and a control unit interfaces and synchronizes the processor, the signal generator, the decoder and the pressure control.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.