An observation and designation apparatus includes a first image sensor and a second image sensor that are connected to an electronic image processor circuit connected to a display. The first image sensor and the second image sensor provide fields that are superposed to supply respectively at least a first image and a second image of the same scene. The appliance further includes a laser emitter for emitting a laser beam lying in a predetermined range of wavelengths into a predetermined zone of the field of the second sensor; a region-of-interest filter extending in front of the second sensor. The electronic processor circuit superposes the two images by using the zone of the second image that corresponds to the third region of the filter to register the second image spatially relative to the first image. An observation and designation method makes use of such filtering.