A 3D Outdoor Scene Scanner Based on a Night-Vision Range-Gated Active Imaging System

We present a 3D outdoor scene scanner for the acquisition of kilometers-deep scenes in night conditions. Its imaging system is based on a compact and low-cost pulsed laser illuminator and a light-intensifier equipped CCD camera. By precisely synchronizing both the illuminator and the camera shutter, it is possible to acquire "slices" of the scene at specific known distances. We show that even with large laser pulses and without megahertz-capable electronics, the third dimension can be recovered for the whole range of the scene by processing only two images acquired in specific conditions. As the pixel intensities of the images produced by active imaging systems vary with the square of the range, and due to the limited dynamics of image sensors, scanning long-range scenes with shorter "slices" allows the camera gain to be adjusted with respect to the range and the accuracy to be enhanced. The imaging system as well as the different image processing steps are detailed in this paper and an example of typical results is given.