Optical Measuring Technique

Moiré Interferometry

Moiré interferometry is a whole field optical method to measure In-plane deformation. It has a high in-plane displacement measurement sensitivity of 0.417 µm per fringe order. High spatial resolution, high signal-to-noise ratio and wide dynamic range make it ideal for measuring deformations of complex geometry like those encountered in electronic packaging. In this method, a high frequency (1200 lines/mm) crossed-line diffraction grating is applied to the specimen surface that reveals the deformation of the specimen with high fidelity. The interaction of the deformed specimen grating with the virtual reference grating of the interferometer creates the moiré fringe pattern, which is viewed by the imaging system. The fringes obtained are contours of in plane U and V displacement. The contour interval between fringes is 0.417 μm per fringe order. Displacement and strain information are extracted from these fringe patterns by using mathematical relations.