1. A method for monitoring a field of regard, the method comprising: imaging at least a part of the field of regard by concurrently collecting a plurality of light components propagating along different optical paths from a plurality of different zones, respectively, located within the field of regard, said plurality of light components being concurrently collected by a corresponding plurality of light collecting units having a first numerical aperture of light collection being the same for each of the plurality of light collecting units; superimposing a plurality of images of the plurality of said different zones of the field of regard, respectively, by concurrently projecting the plurality of light components collected from said plurality of different zones in an additive manner onto a common light sensitive surface of a same light detector to form a combined image that is made up of the plurality of the superimposed images of different zones, thereby obtaining flux averaging of said plurality of light components; generating image data indicative of said combined image; and processing and analyzing the image data indicative of the combined image, and upon identifying existence of a certain condition or event in the image data, generating a corresponding control signal indicative of the existence of said condition or event in at least one of said plurality of different zones, thereby enabling to further scan at least some of the zones based on analysis of the image data of the combined image with said first numerical aperture or a different second numerical aperture.