The book gives theoretical and experimental results in the field of interferential selectors for lasers with controllable parameters of radiation, diffraction optics, digital holography, digital signal processing and error analysis in optical metrology. Ray-tracing and plane-wave expansion methods are applied to build a generalized theory of a Fizeau wedge in reflection and transmission at illumination with typical intra-cavity laser beams. The newly established wedge properties are used for laser solutions, in which it acts as a spectrally selective tunable reflector, filter and optical coupler. Based on Fresnel diffraction integral, a theory of sinusoidal phase grating is proposed as an element for phase-shifting pattern projection profilometry of large-scale objects. Design, analysis and realization of two phase-shifting holographic systems for microscopic observations and for evaluation of plane mechanical stresses are included. The book provides theoretical description and uncertainty analysis of two systems based on a Michelson interferometer: a white light source Fourier spectrometer and a system for spectral fixation of laser diode emission to an atomic absorption line.