Optimization of the photoelastic fringe pattern processing for the stress evaluation in scintillating anisotropic media

Scintillating media are used in numbers of fields, from the high-energy physics to the biomedical devices, like those for the cancer detection and characterization, passing through the laser technology and industry processes control. Their performances must be enhanced in order to accomplish to the more and more sophisticated needs of the applications. Residual stress conditions are crucial for the correct performance of these materials. Moreover, an accurate study of the internal stress leads to a proper setting of the production process and prevent unwanted fractures of the brittle media. Non-invasive photoelastic methods are particularly suitable for the purpose; producing fringe pattern images which are a signature of the crystal state. These methods have to be supported of algorithms dedicated to the image analysis, so to extract geometrical parameters of the fringe pattern. Here an optimized algorithm to analyze the fringe pattern acquired by a laser based polariscope is discussed. This algorithm has been optimized and automated so to reduce the measurement uncertainty, considering a time saving procedure. The implemented procedure makes the software able to recognize the ROI in the acquired image and reduces the uncertainty by a factor 3.5.