1. An optronic passive surveillance device, comprising: a front optic having a useful instantaneous fields; a scanning device to observe a scene with a given total field of observations; means for forming the image of the scene; a two-dimensional matrix detector for detecting said imaged; and counterscanning means in which the field of the detector along each of the dimensions being greater than or equal to said useful instantaneous field of the front optic along said dimension, and allows the acquisition, for each elementary area of the scene corresponding to the useful instantaneous field of the front optic, of N subimages formed on said detector N&gE;1, with a given integration time for each subimage, and in which the counterscanning means to make it possible to compensate for the movements of the image that are due to the scanning of the scene during the acquisition of the N subimages.