A display device comprising means (2) for generating one or more viewable images; means (9) for generating one or more viewing zones for viewing the viewable images; and an optical element (1) with positive optical power. The elements are arranged and constructed such that the optical element forms a real image of the or each viewing zone and a virtual image of the or each viewable image whereby the or each virtual image is visible to a viewer only when a light ray can b e traced from the viewer's eye through the real image of an associated viewing zone, the optical element and the viewable image. The display may be an autostereoscopic display.
