On the real performance of SWIR range-gated active imaging in scattering media

Range-gated active imaging is a well-known technique used for night vision or for vision enhancement in scattering environments. The elimination of the backscattering effects leads to a significant increase in the vision range in scattering environments. Surprisingly, even if a lot of authors estimate that active imaging brings a gain in range when used in scattering environments, there are no studies which systematically investigate and quantify the real gain provided by range gating in comparison with classical imaging systems and in different controlled obscurant densities. In this paper, we thoroughly examined the performance enhancement of laser range gating in comparison with a color camera representing the human vision. On the one hand, we studied the influence of different types of obscurants and showed that the type of obscurant leads to very different results. On the other hand, we examined the influence of different technical parameters on the laser side and on the camera side. The influence of range gating and of the gate shape was studied. These experiments led us to conclude that it is necessary to combine a short laser pulse with a short camera integration time to acquire contrasted images in dense scattering media.