Editorial: Digital holography: Applications and emerging technologies

A lot of researchers in optics have mentioned that holography, pioneered by Gabor in the late 40s could be a major, and possibly the ultimate solution towards threedimensional (3-D) display. This may not be an overstatement, for as early as 1962, Yuri Denisyuk and his peers have realized optical holograms for recording 3-D images of real-world objects. When lit with a coherent light source, a hologram reconstructs a realistic visual image of the 3-D objects it records. Being different from another effective and widely adopted 3-D technology based on the lenticular lens, observing a hologram does not lead to accommodation-vergence conflict, which could induce visual fatigue or headaches to some people. Despite all its advantages, optical holography does not gain equal acceptance in the consumers market as compared with traditional photography. The discrepancy is mainly due to the need of expensive and delicate optical setups, mounted in a practically vibration-free optical table in a dark room, in capturing a hologram. These kind of stringent requirements basically limit the production of holograms to a laboratory environment that is generally unavailable to consumers at large. Similar to photography, optical holograms records magnitude of light waves encapsulating both amplitude and phase information on photographic films, and the contents cannot be changed afterwards. To produce a hologram with animated content, multiple frames of object images are sequentially recorded onto a multiplexed hologram. In this approach, the optical waves of each object image is mixed with a unique off-axis reference beam, and exposed onto the photographic film. The number of frames is rather limited and only a short video clip can be recorded onto a multiplexed hologram. Insofar, what the holography technology can be provided to the community is perhaps the 3-D holograms that we can purchase from the specialty stores. OPEN ACCESS