A method to determine the amplitude and phase fluctuations in each point of a wavefront is presented. The basic idea of the method is the possibility of investigating the amplitude and phase at each point of a wavefront by superposing a spherical reference wavefront that has its origin in the point under investigation. The information on the fluctuations is extracted in the form of an electrical signal. Application to the study of phase fluctuations produced by atmospheric turbulence is considered.
M. Bertolotti, "Electrical Recording of the Amplitude and Phase Fluctuations of a Wave Front," Appl. Opt. 10, 42-42 (1971)