'Princess Leia Project' Images That Float In The Air
BYU electrical and computer engineering professor and holography expert Daniel Smalley has long had a goal to project 3D images.
His inspiration? In the Star Wars, feisty robotic companion R2D2 projects an image of Princess Leia in distress. The iconic scene includes the line still famous 40 years later: “Help me Obi Wan Kenobi, you’re my only hope.” The 3D chessboard from the same movie is equally recognizable to fans.
In a paper published this week in Nature, Smalley details the method he has developed to do so.
(BYU images float in thin air)
“We refer to this colloquially as the Princess Leia project,” Smalley said. “Our group has a mission to take the 3D displays of science fiction and make them real. We have created a display that can do that.”
First things, first, Smalley says. The image of Princess Leia is not what people think it is: It’s not a hologram. A 3D image that floats in air, that you can walk all around and see from every angle, is actually called a volumetric image. Examples of volumetric images include the 3D displays Tony Stark interacts with in "Iron Man" or the massive image-projecting table in "Avatar."
Smalley and his coauthors have devised a free-space volumetric display platform, based on photophoretic optical trapping, that produces full-color, aerial volumetric images with 10-micron image points by persistence of vision.
The technique, as described by Nature, “uses forces conveyed by a set of near-invisible laser beams to trap a single particle — of a plant fiber called cellulose — and heat it evenly. That allows researchers to push and pull the cellulose around. A second set of lasers projects visible light (red, green and blue) onto the particle, illuminating it as it moves through space. Humans cannot discern images at rates faster than 10 per second, so if the particle is moved fast enough, its trajectory appeas as a solid line — like a sparkler in the dark.”
“In simple terms, we’re using a laser beam to trap a particle, and then we can steer the laser beam around to move the particle and create the image,” said undergrad coauthor Erich Nygaard.
Smalley said the easiest way to understand what they are doing is to think about the images they create like 3D-printed objects.
“This display is like a 3D printer for light,” Smalley said. “You’re actually printing an object in space with these little particles.”