A method for extracting an illuminated zone from a matrix of photosensors may include: (a) dividing the matrix into a plurality of search zones, (b) searching for the presence of an active photosensor in the search zones, (c) stopping the search as soon as an active photosensor is found in a search zone, and (d) further subdividing the first search zone determined to have an active photosensor into a plurality of search zones. Additionally the method may include repeating steps (b) through (d) until a search zone having only active photosensors is obtained.