Abstract: The apparatus comprises an object for display, a retro-reflector receiving light from the object, a beam-splitter in a path for light from the object to the retro-reflector, and a Fresnel lens (having no point of central symmetry) between the beam-splitter and the retro-reflector. The beam-splitter makes an oblique angle to the direction of propagation of the light, such that it transmits some light and reflects the rest. Light from the beam-splitter passes through the lens to the retro-reflector, which reflects it back through the lens to the beam-splitter. This retro-reflected light is reflected and/or transmitted by the beam-splitter to form a real image suspended in space. The type of Fresnel lens used in the apparatus improves viewability because unwanted reflections from the surfaces of the lens are shifted such that they are no longer visible when viewing the suspended image.

Abstract: Apparatus for displaying an image suspended in space comprises an object (1) for display, a retroreflector (2) receiving light from the object, a beamsplitter (3) in a path for light from the object to the retroreflector, and a concave mirror (4) between the beamsplitter and the retroreflector. The beamsplitter makes an oblique angle to the direction (6) of propagation of the light such that it transmits some light. Light from the beamsplitter is reflected by the mirror to the retroreflector which reflects it back via the mirror to the beamsplitter. This retroreflected light is reflected by the beamsplitter to form a real image (5) suspended in space. The use of a concave mirror improves viewability over apparatus including a converging lens because unwanted reflections from the surfaces of the lens are eliminated.