Strainoptic Technologies Inc. manufactures the Distortiometer SD-1900 digital image analysis system (DIAS) for measuring optical distortions. The system produces Moire fringes by projecting a master grating onto a reference grating pitch through an inspected item. The reference grating pitch is 20 lines/inch (1.25mm). In perfect glass, a set of parallel or carrier fringes is observed. Any distortion in the inspected item deforms the fringes. These two images are captured by a CCD camera. The differences between the two patterns are automatically analysed by the DIAS, yielding a quantitative full field map of distortion. Results are reported for line-of-sight (angular) deviation in milliradians or arc-minutes. Distortion is reported in milliradians or arc-minutes/mm.
