Shearography is an approved and powerful tool for the nondestructive investigation of technical components with respect to material faults and technical imperfections. Current applications are for instance the in-service inspection of aircraft components and the tire testing. Possible imperfections can be recognized as typical fringe patterns such as the well-known butterfly type. However, a reliable flaw recognition requires a sufficient clarity of the local fault indicating pattern in contrast to the global image content. Since shearography is based on the digital correlation of speckle patterns, the image quality and consequently the flaw visibility can be very poor if some essential prerequisites aren't fulfilled. Especially for the testing of large scale components the following factors should be carefully taken into account before the experiment is started: the type of the object (relevant area, surface, fixing, ...), the type of the sensor (aperture, resolution, sensitivity, ...), the way of object illumination (wavelength, illumination profile, ...) and the way of loading (mechanical, pressure, temperature, ...). With respect to an optimal adjustment of these factors this article investigates their influence on the image quality and their mutual dependency. The derived functional dependencies are verified on example of some relevant applications for aircraft and artwork inspection.
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