Non-destructive testing by laser scanning
US4824250A · kind A · utility
Inventor
Key dates
| Filing date | May 5, 1988 |
| Grant date | Apr 25, 1989 |
| Priority date | — |
| Expiry date | May 5, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2201/104
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The invention provides a method and apparatus for non-destructive testing of bonded structures, such as laminated or composite materials. A beam of coherent light is directed successively onto each point of the object. The reflected beam creates a speckle pattern. The pattern is observed once while the object is stationary and once while the object is mechanically excited. If the point being observed is free of defects, the speckle pattern will be substantially unaffected by the vibration of the excited object. If the point is defective, vibration will blur the speckle pattern. The entire object is scanned, point by point, and the results of the comparison of the speckle patterns obtained for each point are stored and displayed. In another embodiment, the object is made to vibrate continuously, and the apparatus determines whether the speckle pattern is sharp or blurred, for each point being scanned. The sharpness of the speckle pattern can be inferred from the measured intensity of the speckle pattern, or it can be calculated directly by a suitable algorithm. In general, if the detector has a nonlinear response characteristic, the total intensity of the speckle pattern will be low…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.