Spectrum and time modulation in measurements of optical signals and transfer functions varying in time

A solution of the phase problem in optics is considered as applied to the analysis of time-dependent signals and transfer functions describing optical features of the object under study. In particular, we analyze signals and processes of extremely short duration. A simulataneous analysis of the structure of the initial optical signal and of the amplitude and phase action of the object on the signal is performed. The modulation-spectrum approach is used to obtain the required information on the time behavior of the amplitude and phase of the optical testing signal before and after its interaction with the object. The object's influence is characterized by an additional modulation of the radiation. In order to obaain the information, the intensity distribution of the spectra of the testing signal passed through the object, of the signal subjected to an additional spectrum modulation and then passed through the object, and of the corresponding signals additionally modulated in time is detected. The modulation should provide, to a certain degree, a visualization of the phase information. The intensity distributions obtained in this way make it possible to calculate the structure of the signal under study and that of the time-dependent function that describes the object influence on the radiation.