Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1988-05-05
1989-04-25
LaRoche, Eugene R.
Optics: measuring and testing
By particle light scattering
With photocell detection
73588, 73657, G01N 2904
Patent
active
048242500
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 lower when the pattern is blurred, and higher when the pattern is sharp. A low intensity therefore indicates that the point on the object is defective. As in the first embodiment, the results of the analysis are stored in a computer memory and displayed on a video monitor.
REFERENCES:
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Eilberg William H.
LaRoche Eugene R.
Pascal Robert J.
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