Viewing conditions of multiplexed holographic images

• The terms describing the viewing condition of a holographic display built with a display chip, such as viewing zone, viewing zone angle and viewing angle is redefined.
• Several basic viewing geometries for spatial and time multiplexing schemes covering those from previous articles are given to show that the viewing conditions of the schemes are not better than that of a facet of the multiplexed image.
• 2×10 DMD images which are formed both by time and spatial multiplexing are introduced as examples of demonstrating the viewing condition.

The time and spatial multiplexing which are frequently employed in holographic displays based on display chips of the same characteristics, to increase reconstructed image size and resolution can hardly improve the viewing condition such as viewing zone and viewing angles more than what a chip can offer. This is demonstrated optically and experimentally with the holographic displays built with an array of 2×10 DMDs which is formed both by time and spatial multiplexing. It is considered that the viewing condition of the spatial multiplexing is somewhat worse than that obtained by time multiplexing because the reconstructed image size of each chip cannot be smaller than the hologram size. Furthermore, the spatially multiplexed image can be noisier than that obtained from time multiplexing but it shows better light efficiency. Added on this, it does not introduce a distortion in the image as in the time multiplexing.