Single photon imaging for maritime night situational awareness

Modern military platforms such as armored vehicles or marine vessels rely on camera systems to observe their environment. Combined with intelligent object detection and tracking, they provide an effective way to automatically monitor the surroundings of a platform, collect information and provide early warnings in case of the appearance of a threat. In order to operate at night, most systems integrate a night vision channel, usually based on thermal infrared cameras. Those cameras allow to sense the thermal emission of objects instead of the reflected sun light and are thus able to operate at night without sun illumination. However, the thermal infrared detector complexity limits the possible sensor resolution and the imagery contrast depends on object temperature differences which is less likely to contain detailed appearance features essential for automatic object classification. This limits the general performance of a situational awareness system at night. The recent developments of arrays of single photon avalanche diodes (SPAD) have led to cameras providing single photon sensitivity. It becomes possible to implement night vision situational awareness systems that don’t rely on bodies thermal emissions but on the weak light reflections. In this paper, we assess the capability of the SPAD array camera's single-photon sensitivity for long-range observation of distant objects under low light conditions. Our experiments, conducted from the coast of the Netherlands towards objects at sea approximately 10 kilometers away, demonstrate the effectiveness of the SPAD array camera.