A novel technique, moire deflectometry, for ray deflection mapping is presented. Numerous experimental techniques for diagnostics of phase objects and specular surfaces, for shearing analysis, for microscopy, and for MTF determination, based on moire deflectometry, are described. The wide range of applications encompasses laser beam diagnostics, characterization of optical components, flow visualization in wind tunnels, temperature mapping of flames, turbulence study, and real-time tracking of transient phenomena like thermal lensing.