Interferometry makes use of the principle of superposition to combine separate waves together in a way that will cause the result of their combination to have some meaningful property that is diagnostic of the original state of the waves. This book presents current research in the principles and applications of interferometry. Topics discussed include speckle methods for material analysis; using White Light Interferometry for accurate topographic measurements of surfaces; cyclic path interferometric configuration applications; phase-stepping algorithms; periodic error measurement for heterodyne interferometry and high contrast Schlieren diffraction interferometry..