Holograms are a mainstay of almost any science fiction film set in the not-too-distant future and beyond. But the capabilities of our real-life versions fall drastically short so far. They generally require an extensive set-up, can only be seen correctly from certain angles, and often require special viewing headgear (the famous posthumous performances of Tupac Shakur, Elvis Presley and Michael Jackson seen in recent years weren't really holograms, just projections or stage magic). But new research published today in Nature might represent one of the greater leaps forward to date: A way to create a three-dimensional, solid- and clean-looking image that can exist in the same space as other objects and even move.
Researchers at Brigham Young University in Utah made something they're calling an Optical Trap Display (OTD). The device traps a tiny opaque particle in mid-air using an invisible laser beam, then moves the beam around a preset path in free space. At the same time, it illuminates the particle with red, green or blue lights. When the particle moves fast enough, it creates a solid holographic image in the air. Move it even faster, and you can create the illusion of movement.
A mock-up of how the OTD device works, as well as two early images generated by it. Image: Smalley et al/Nature
"We can think about this image like a 3D-printed object," lead author Daniel Smalley, an assistant professor in electroholography at Brigham Young University, explained in a Nature video. "A single point was dragged sequentially through all these image points, and as it did, it scattered light. And the accumulated effect of all that scattering and moving was to create this 3D image in space that is visible from all angles."
Scientifically, what Smalley and his team are creating are known as volumetric images, which differentiates them from 2D-hologram technologies. Other companies and scientists have made devices that create volumetric images, but the researchers say theirs is the first to generate free-floating images that can occupy the same space as other objects, as opposed to volumetric images that need to be contained inside a specially designed field. Other devices often require a much more elaborate set-up as well, while the OTD is relatively cheap, made with commercially available parts and low-cost lasers.
There's been seemingly no end to the variety of images possible with the OTD; the Nature paper notes the team has created everything from butterflies to the Earth from afar to actual people. And the images are especially crisp, with resolutions as high as 1600 DPI (your average printed photo hovers around 300 DPI).
That said, the device does have its limitations. Namely, that the images produced right now are quite tiny: Smaller than a fingernail. Making the images bigger will require the researchers learn how to manipulate more than one particle at a time. And it's unlikely the device will be usable outdoors for the foreseeable future, since fast moving air particles can muck up the process. Video cameras also have a problem capturing the images the way our eyes or still cameras do - a video's frame rate makes the image look as though it's flickering, while our eyes only see a solid image.
Still, the researchers are optimistic about the future of their project.
"We anticipate that the device can readily be scaled using parallelism and consider this platform to be a viable method for creating 3D images that share the same space as the user, as physical objects would," they wrote in the paper.