Abstract: A portable device providing visual images of infra-red sources by means of I.R. detectors/electric signals/light emitting diodes. Scanning is employed to reduce the numbers of I.R. detector elements and L.E.D.'s, the scanning being effected by a rotating polygon having mirror facets tilted at slightly different angles to scan the object and image fields simultaneously in strips which cover the respective fields in a cycle.One aspect of the invention consists in tilting the I.R. and visual facets oppositely to transfer a low I.R. strip position to a correspondingly high visual strip position and vice versa.A second aspect consists in using a polygon with 45.degree. facets and I.R. detectors and L.E.D.'s on optical paths parallel to the axis of rotation. The scanned strips are then symmetrical about their field center lines.