Daniel Smalley has always dreamed of creating 3D holograms like those in science fiction movies. But after watching Tony Stark reach into a kind of ghostly 3D full-body armor in Iron Man, Smalley realized he would never be able to achieve that with holographic technology and current standards geared toward high-tech 3D displays. a little. Because Stark’s hand will block the light source of the hologram. “It bothers me,” Smally said. The physicist at Brigham Young University in the United States has since started thinking about how to get around this.
With the help of so-called volumetric display technology, the system can create the floating butterfly in the above image through an example
Smalley’s team took a different approach, using so-called volumetric display technology to create moving 3D images that users can perceive from any angle. Some physicists say the technique is closer to the 3D projection of Princess Leia in the “Star Wars” movies. “This can do something that a hologram can’t, which is give you a full view, a Princess Leia-like display, because it’s Not a hologram at all.”
The principle of this technology is like a high-level version of Etch a Sketch application: through a set of forces presented by a nearly invisible laser beam, individual particles of plant fibers called cellulose are captured and unevenly distributed. heating. In this way, the researchers can push and pull the cellulose. A second set of lasers projects visible light (red, green and blue) onto the particles, illuminating them as they move through space. Humans can’t discern images faster than 10 times per second, so if a particle moves fast enough, its trajectory will appear as a solid line, like a firework moving in the dark. If the image changes fast enough, it will appear to be moving. The displayed image can be superimposed on the real object so that the user can walk around it in real space.
Currently the images created are so small that they can only be measured in millimeters. And at the speed needed to create the illusion of a moving image, the system can only draw a simple line. The team managed to depict a moving, spiraling line, as well as a static silhouette of a butterfly
William Wilson, a nanotechnology researcher at Harvard University, pointed out that the technology still needs a lot of research and development efforts, but this simple design has huge room for improvement.
This approach has a number of advantages over existing 3D display technologies. Holography essentially sends light through a 2D screen containing a diffraction grating to create a 3D image. Gratings are able to manipulate the path of light, interfering with it to create an image perception that includes depth. Advanced holograms can achieve full color and true size, but because the light must always appear on the 2D surface, the viewing angle is very limited. Also, because it is difficult to change the diffraction grating at high speed, holograms are usually static images.
In contrast, volumetric 3D display technology can reconstruct images in 3D space. Most existing systems project images onto rapidly rotating 2D screens. More complex displays, including a research project at Keio University in Tokyo that inspired Smalley, use spheres of superhot plasma in 3D space, but they currently only work in one color. Other approaches use augmented reality hardware such as Microsoft HoloLens to create the illusion that a 3D image appears in the real world, but they all require dedicated headsets and are computationally demanding.
The latest systems can already create images at higher resolutions than conventional computer screens (up to 1600DPI). But in order to create realistic images that include complex moving images and larger visualizations, physicists need to find ways to accelerate the motion of particles and control several of them at the same time.
Smalley said he already has an idea of how to solve these two problems, saying: “If we make as much progress in the next four years as we have in the past, I believe we will succeed in achieving a reasonable size wall display screen image. ”
One drawback of the technique is that it is difficult to get rid of the ghostly see-through quality of the projection, says Nasser Peyghambarian, an optical physicist at the University of Arizona. The reason for this is that the eye receives light from particles on the “front” of the image and particles on the “back”.
The final problem is that the system can easily lose balance because the forces used to control the particles are too small. This could hamper military applications, such as simulating 3D combat scenarios to train soldiers, because any strong winds would affect the particles in orbit. To get around this problem, Smalley points out, the system can scatter light from a fog of particles that appears only temporarily. “You’d never use it in a hurricane, but it’s not beyond reason to use it outdoors,” he said.