Moire interferometry for out-of-plane displacement measurement

A high sensitivity technique for out-of-plane displacement is demonstrated. A 600 lines mm phase grating is used in conjunction with a specularly reflecting (in some cases mirrored) object, to obtain contours of out-of-plane displacement. Initial patterns due to low quality optics are eliminated by a double exposure technique employing carrier (or mismatch) fringes. Beams with cracks are used to experimentally demonstrate this technique.