Nanocrystal-based solar cell technologies currently have two materials competing for the highest performances: PbS and perovskites. These latter benefit from a defect-tolerant electronic structure, while PbS benefits from a mature diode fabrication technique and from its near-infrared absorption. Here we choose to revisit the potential of these PbS photodiodes for near-infrared detection and more precisely for active imaging. This mode of detection combines an eye invisible source with a detector. Such detection mode is used for surveillance, industrial sorting, LIDAR, etc. Here we use a state-of-the-art photodiode geometry and we reveal its potential for near-IR active detection at 940 nm. The diode can achieve a high photoresponse of 0.5 A.W-1, corresponding to an external quantum efficiency of 66% and a detectivity above 1012 Jones at room temperature. The time response which is often neglected for solar cells is found to be 10 ns for rise time and 1 µs for decay time. We demonstrate that long-distance (over 150 m) and time-gated active imaging can be conducted using this device.