Panoramic single‑photon counting 3D lidar

Abstract

In defense and security applications it is often of interest to find out if something is hidden inside the forest edge on the other side of an open field. High resolution 3D data has a possibility to allow segmentation of hidden objects from branches and leaves and to provide data for object identification. Multiple measurements with single photon counting lidar can provide very high range resolution to separate reflections from objects at different distances inside the system instantaneous field of view. Geiger mode avalanche photo diode (GmAPD) arrays provide high frame rate lidar data collection, but with array sizes that are in most cases smaller than the scenes that should be imaged. The high frame rate of GmAPD arrays and the low laser pulse energy necessary, however, make panoramic single photon counting 3D lidar of large scenes by sweeping the array field of view practically applicable. Indoor and outdoor measurements at up to 350 m range have been performed at FOI using single pixel and GmAPD array single photon counting 3D lidar systems. Panoramic imaging with a 128×32 GmAPD array 3D camera has been performed over an angle of 20° using 4 s total collection time in daylight conditions, resulting in 128×1400 panorama pixels where every pixel contains a histogram representing the laser radar response in that direction. A flat surface at ca 235 m distance had a standard deviation of point to plane distances of 10.6 mm. The laser excitation was far from the optimal that allows for over 0.5 photon detections per pixel and laser pulse. With a higher power laser the accuracy can hence be further improved or alternatively the necessary collection time can be reduced. A single panorama provides rapid high resolution 3D data for target detection. Continuous surveillance from a fixed sensor position allows change detection to provide segmentation of interesting activity in the large data volume.