1. Head up display (HUD) for displaying a combined image of, a scene image of a scene and an informative image, for an observer, the HUD comprising: an image source for producing a substantially small narrow angle informative image, said informative image including information for presentation to said observer; an optical relay for producing a substantially large narrow angle informative image, by enlarging said substantially small narrow angle informative image, received from said image source; a horizontally expanding optical assembly for producing a horizontally magnified image, by horizontally magnifying said substantially large narrow angle informative image, received from said optical relay, said horizontally expanding optical assembly being of low physical height; and a planar optical module including: a planar light guide; a reflector for directing said horizontally expanded image into said planar light guide as a reflected light beam; and a plurality of beam splitters, each of said beam splitters directing a respective portion of said reflected light beam toward said observer in a direction substantially normal to said planar optical module, wherein each of said respective portion of said reflected light beam including all said information of said informative image to be presented to said observer, each of said beam splitters directing another respective portion of said reflected light beam toward a consecutive one of said beam splitters, each of said beam splitters producing said combined image by combining said scene image with said respective portion of said reflected light beam.