1. An electronic imaging device, comprising: an optical objective for collecting optical radiation from an object, the objective having an optical axis; an image sensor, comprising a planar matrix of optical detectors arranged in a plane that is substantially parallel to the optical axis, the image sensor having an active area, which has a lateral dimension in the plane; a prism, having an exit face adjacent to the image sensor and an entrance face adjacent to the objective, and an optical surface comprising a reflective face of the prism, wherein the optical surface is positioned so as to reflect the radiation collected by the objective in order to form a focused image in the plane of the image sensor, while a maximum distance among distances from points on the optical surface to the plane of the image sensor is substantially less than the lateral dimension of the active area of the image sensor; an aperture stop placed in front of the entrance face; and wherein a surface of the prism opposite the exit face is flattened parallel to the exit face so as to reduce a height of the entrance face of the prism, and the aperture stop is placed close to the entrance face so that the height is substantially less than the lateral dimension of the active area of the image sensor.