Anybody who has ever seen the movie Star Wars remembers the scene in which the robot R2-D2 projects a 3D movie of Princess Leia imploring Obi-Wan Kenobi for help. Now, a new technique can conjure similar rudimentary 3D images out of thin air, a team of engineers reports today in Nature. Although far from as refined as the fictional Princess Leia projection, the new technique might one day help guide surgeons in delicate procedures.
Scientists have tried to create 3D projections, or volumetric displays, for more than a century with varying degrees of success. Some displays work by rapidly projecting a sequence of sliced-up images onto a rotating piece of glass, giving the impression of a complete 3D object. Others beam images onto clouds of fog or dust. However, very few displays can be precisely controlled while still floating freely in the air. “It is easy to make a volumetric display that works, [but] it’s very difficult to make a volumetric display that works well—hence 100 years of research,” says Barry Blundell, a physicist and engineer at the University of Derby in the United Kingdom who was not involved in the new work.
Now, a team of engineers has come one step closer to the ideal by exploiting the phenomenon of photophoresis, in which small, airborne particles can be manipulated with an intense beam of light. Daniel Smalley, an electrical engineer at Brigham Young University in Provo, Utah, and colleagues used a special combination of lenses to create a laser beam with both bright and dark regions. The dark areas trap the tiny particles, because heat from the surrounding light pushes them back in if they try to escape.
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