Researchers from Brigham Young University (BYU) have created a true 3D hologram, or "volumetric image," to use the correct term. "We can think about this image like a 3D-printed object," said BYU assistant professor and lead author Daniel Smalley. “We refer to this colloquially as the Princess Leia (in Star Wars R2D2 projects an image of Leia in distress) project.†Smalley said. "We can think about this image like a 3D-printed object,. 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.â€
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.
Smalley and his coauthors have devised a free-space volumetric display platform, based on photophoretic optical trapping, that produces full-colour, aerial volumetric images with 10-micron image points by persistence of vision.
The technique “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 co-author 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.”
So far Smalley and his student researchers have 3D-light-printed several tiny images: a butterfly, a prism, rings that wrap around an arm and an individual in a lab coat crouched in a position similar to Princess Leia as she begins her projected message.
While previous researchers outside of BYU have done related work to create volumetric imagery, the Smalley team is the first to use optical trapping and color effectively. Their method of trapping particles and illuminating it with colorful lasers you can see is novel.
“We’re providing a method to make a volumetric image that can create the images we imagine we’ll have in the future,” Smalley said.
To see the full Nature study, click here