PRESENT EVERYWHERE

In the first original Star Wars film, princess Leia famously appealed for help to Obiwan Kenobi by appearing in front of the Jedi Knight as a small, see-through projected form of her physical self. Meanwhile, elsewhere, R2D2 and Chewbacca were shown playing chess with artificially imaged pieces floating in front of them. In the last Episode III movie too, absent members take part in meetings by having their facsimiles broadcast directly among the real people in attendance, much like an enhanced version of present-day videoconferencing. Even though it's tacitly assumed all these are three-dimensional holographic representations of reality, such stuff is still way in the future- in a galaxy far, far away-because right now all we have is a method of producing a partial 3D image of an object which, in any case, needs a solid backing medium to be expressed on such as paper, plastic or metal. Producing lifelike holograms which could be free floated into mid-air to form a hovering image visible from all sides remains for the time being at least in the realm of science fiction. But perhaps not for long.

A technique for projecting holographic images to make both still and moving three-dimensional displays is currently undergoing development in the United States at NASA's Jet Propulsion Laboratory. This technique, unlike older ones based on stereoscopy, would not involve the use of polarising goggles, specialised eyewear or other visual aids. Also, unlike in holographic displays as practised until now, visibility of the image would not be restricted to a narrow range of directions;instead, it would be observable from any side. In other words, the display could be viewed as though it were an ordinary three-dimensional object. The technique has obvious potential value for the entertainment industry as in video games and home theatre, and for military uses like displaying battlefield scenes overlaid on terrain maps. It could also be used as store displays, for exhibiting rare museum artefacts and in operating theatres where a patient's vital signs could hover above the chest during open heart surgery. As for princess Leia, she could be projected straight to our living rooms in future.