Short-pulsed terahertz imaging techniques have found application in recent years especially in the areas of nondestructive evaluation, homeland security and biomedical imaging. One such application involves the inspection of bonding between spray on foam insulation (SOFI) and the external tank in the NASA space shuttle. Results validating the model were presented using experimental measurements from two kinds of defects each with two types of imaging feature. A number of imaging features for converting the 3D terahertz data to a 2D image were explored in this work and it is observed that windowed fourier transform (WFT) imaging using high frequency data of the spectrum provides optimal and informative images in comparison to their time domain counterparts. Physics based insight was also discussed in order to explain the improved performance of WFT imaging. Automatic defect detection algorithms were developed based on adaptive threshold and iterative processing techniques in order to enable overall automated analysis. Defect profiling algorithms have been developed using WFT and TOF images. In the case of TOF image data, a method was described for estimating and subtracting slow varying background trends present the in the image. It is important to note that although above techniques have been developed and evaluated based on data from NASA-SOFI inspection they can be extended to other applications.
Imaging and modeling techniques for terahertz inspection of NASA-SOFI
Abbildungs- und Modellierungstechnik für Terahertzprüfungen von NASA-SOFI
2007
7 Seiten, 8 Bilder, 11 Quellen
Conference paper
Storage medium
English
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