In this paper we study specifics of an ultrashort pulse transformation with a device similar to the Michelson reflective echelon. The initial impulse transformation process is treated using the conception of pulse response of the optical system, in particular, of the dynamics of scattering of a δ(t - z/c) wave by the echelon. The advantage of this method is the possibility to calculate the response of any optical system to a signal of an arbitrary amplitude dependence on time by calculation of convolution of the function describing the signal with the pulse response, whether the pulse response exists. The urgency of the problem is due to the prospects of the echelon application to the solution of numerous modern problems of optics and optical informatics, such as modulation of the THz radiation spectrum, interferometry of ultrashort laser pulses and problems of absorption spectroscopy with high resolution in time.