MOIRE INSPECTION SYSTEM

A moire interferometry system for detecting defects in a surface of a panel. The moire interferometry system is adapted to be used as a defect detection tool and not specifically as a surface measurement tool. The system includes a moire projection system having a light source and master grating projecting grating lines onto a surface panel to be inspected. A viewing system with a detection means records an image of the surface with the master grating lines on it as viewed through a submaster grating. The intersection of the projected lines on the panel and the lines in the submaster grating produce moire fringes. Phase shift interferometry techniques are used to produce a phase map of the surface for a plurality of phase shifted moire fringes. A derivative operation is performed on the image, and that image thresholded to identify areas of pixels having the greatest change in contour. The resulting image can then be used to locate and quantify deviations in the contour of the panel which exceed predetermined tolerances to identify defects. The system provides an unambiguous quantitative means for characterizing defects which does not require skilled operators or the application of highlighting fluid to the surface.