a three - dimensional image display system , based on a novel depth concept referred to as double - d - depth , includes a first display device and at least a second display device which , viewed along the system axis , are offset with respect to each other and are each intended to partially display the same two - dimensional image of a scene , while parameters which are relevant to depth representation are included in the form of an additional dedicated intensity gradation in at least one of the displayed images , and all images , together with the axial distance in between , evoke a depth effect with a viewer .