In this paper we show how the Fresnel transform helps to detect time-delayed short pulse signals. A short pulse disperses spatially as it propagates through free space according to the Fresnel transform. A point photodetector produces a signal whose temporal frequency is directly proportional to the time delay between the pulses. When this signal is fed to an acousto-optic spectrum analyzer, the frequency domain represents a time delay domain.
"Short-pulse detection by acousto-optic processing", Proc. SPIE 1704, Advances in Optical Information Processing V, (24 August 1992); doi: 10.1117/12.139886; https://doi.org/10.1117/12.139886