Transmission of radiation with rapid temporal modulation through optical instruments

We examine theoretically the transmission of radiation with rapid temporal modulation (short pulse or rapid statistical modulation) through a grating or focused by a concave mirror (lens). It is shown that the far-field diffraction patterns from a grating may be considerably modified because of such rapid modulation and that these patterns may be used for estimation of the coherence time or the pulse duration. In the case of focusing, the focal spot size slightly increases on decreasing the pulse duration.