Polariscope is an optical device and used for the defect identification in PET preforms. Preforms develop internal defects due to external strain. These defects might create weak points when blown moulded into bottle. To avoid this, the preforms are tested prior mass production. The device has an incident light and polaroid lenses. The incident light passes completely through the test medium without any refraction. As a light encounter a defect, it changes its path doubly and create different patterns of light.
Due to polaroid nature of lenses, the birefringence of light forms. This birefringence creates different patterns depending upon the type of the defect. The pattern can be matched with the defect chart to identify the defect. The sample is tested at two different angles, 45° and 90°. The strain viewer can be used for PET preforms and glasses also. It is equipped with two types of incident light Monochromatic and Sodium. The device can be connected with the computer for defect identification and report generation.