The ‘fringe method’ and its application to the measurement of deformations, vibrations, contour lines and differences of objects

A variable sensitivity technique using the projection of a fringe pattern is demonstrated for mapping deformations, vibrations, contour lines and differences between two objects. The method does not require laser illumination and gives an opportunity for studying large objects with incoherent light, and is compared with other techniques such as holography or speckle. The limitations likely to be encountered in industrial environments are discussed. The realization and incoherent projection of gratings is also discussed.