The innovation could one day lead to 3-D holographic movies, enabling cinema-goers to feel they are "inside" a movie yet not have to wear cumbersome, headache-inducing spectacles with polarizing or colored lenses, the inventors hope.
Other beneficiaries include military commanders, who could gain a three-dimensional picture of a battlefield, and surgeons performing complex micro-surgery inside a patient.
In a paper released by the British journal Nature, Nasser Peyghambarian of the University of Arizona and colleagues reported how they recorded, displayed and updated images on a palm-sized screen measuring just four inches by four inches.
Holograms are created by shining a laser on an object, whose image falls onto a photosensitive screen. At the same time, a second laser beam falls on the screen, creating an "interference pattern" -- in essence, the condensed contours of the object, which are embedded in the film.
It takes a third laser, called the reading beam, to be directed onto the screen for the interference pattern to be resurrected. To a person in front of the screen, this creates an image in three dimensions that appears in mid-air behind the screen.
The secret lies in films called photorefractive polymers which contain molecules of dye that respond to light and rotate and line up in response to an applied electrical field.
On their small display, Peyghambarian's team were able to update the image in about three minutes and hold it there for up to three hours.
Anyone hoping for a zappy "Star Wars"-style hologram that can be viewed from any point in the room would be disappointed, though.
The parallax, or 3D effect, still can only be seen within a given angle by a person in front of the screen. Move too far to the right or left or up or down, and the effect is lost.
Joseph Perry of the Georgia Institute of Technology in Atlanta, in a commentary published by Nature, said the innovation was extraordinarily promising, not least because the polymers were potentially cheap and easy to produce.
It was only a matter of time before higher-powered lasers and more sensitive photorefractive polymers ushered in larger and faster 3-D displays, he predicted.Technorati Tags: hologram, holodeck, Star Trek, 3-D, laser, imaging,