360-Degree Hologram Displays

360° holograms can be used for directly viewable image display both in information retrieval systems and in static displays. Images can be displayed with modest sized viewers that use a small section of the hologram for individual observers and with the capability for rapid interchange of holograms. Static displays that use the entire hologram are also realized in this concept. Holographic projector systems are also possible which can form two-dimensional images on a flat screen with parallax change along two dimensions. The design of viewers and projectors involves consideration of many parameters and tradeoffs that involve image quality, design complexity, appearance, and cost. Virtual image display units can use either laser or arc lamp light sources, while a laser beam is needed for projectors. Projectors require special design considerations related to the fact that the hologram con-tains the images in their original size and depth. Coherent speckle of projected images can be eliminated by use of fluorescent paints on the pro-jection screen. Several design examples of display units are described and shown.