The authors' studies on the development and practical use in practice of new methods for visualizing currents based on the use of speckle technologies are summarized and systematized. The book outlines the theoretical and experimental foundations of diagnostic methods such as speckle technologies. Diffraction theory of speckle photography, speckle interferometry, PIV, BOS, Talbot interferometry, etc. The foundations of a new scientific direction are outlined, combining classical interferometry, speckle interferometry and digital image processing.