Defense company Qinetiq is working in a targeting system that won't use any optics whatsoever. Based on the technology used to capture gamma bursts in space, the Lacoste- Large Area Coverage Optical Search While Track and Engage-project will use multiple sensors arranged behind a randomly-punctured mask and signal processing software, which will make it shock-resistant and very light. The imaging system is used by NASA on board their Swift satellite , which is dedicated to spot gamma bursts. They got rid of the optics to make it lighter and more durable, thanks to the lack of optics and mirrors. The sensor redundancy also makes it error-proof: there are thousands of them, so if one gets damaged, the image will maintain its quality. Other than its durability, the system can track thousands of vehicles at any time, and even has a "super resolution" mode that allows to produce a very detailed image of any sector in its field of view. [BBC News]
It detects light, it just doesn't use a lens to focus it. The mask keeps the CCD from being overloaded and the software interpolates an image from a sequence of exposures. Sounds like it's data-stream light, but computationally expensive on the back end...which is why they want to put it on long-duration UAVs.