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This photo provided by the Dan Smalley Lab at Brigham Young University in January 2018 shows a projected image of researcher Erich Nygaard in Provo, Utah. Scientists have figured out how to manipulate tiny nearly unseen specks in the air and use them to produce images more realistic than most holograms, according to a study published on Wednesday, Jan. 23, 2018, in the journal Nature. (Dan Smalley Lab, Brigham Young University via AP)
One of the enduring sci-fi moments of the big screen—R2-D2 beaming a 3-D image of Princess Leia into thin air in “Star Wars”—is closer to reality thanks to the smallest of screens: dust-like particles.
Scientists have figured out how to manipulate nearly unseen specks in the air and use them to create 3-D images that are more realistic and clearer than holograms, according to a study in Wednesday’s journal Nature . The study’s lead author, Daniel Smalley, said the new technology is “printing something in space, just erasing it very quickly.”
In this case, scientists created a small butterfly appearing to dance above a finger and an image of a graduate student imitating Leia in the Star Wars scene.
Even with all sorts of holograms already in use, this new technique is the closest to replicating that Star Wars scene.
“The way they do it is really cool,” said Curtis Broadbent, of the University of Rochester, who wasn’t part of the study but works on a competing technology. “You can have a circle of people stand around it and each person would be able to see it from their own perspective. And that’s not possible with a hologram.”
The tiny specks are controlled with laser light, like the fictional tractor beam from “Star Trek,” said Smalley, an electrical engineering professor at Brigham Young University. Yet it was a different science fiction movie that gave him the idea: The scene in the movie “Iron Man” when the Tony Stark character dons a holographic glove. That couldn’t happen in real life because Stark’s arm would disrupt the image.
Going from holograms to this type of technology—technically called volumetric display—is like shifting from a two-dimensional printer to a three-dimensional printer, Smalley said. Holograms appear to the eye to be three-dimensional, but “all of the magic is happening on a 2-D surface,” Smalley said.
The key is trapping and moving the particles around potential disruptions—like Tony Stark’s arm—so the “arm is no longer in the way,” Smalley said.
Initially, Smalley thought gravity would make the particles fall and make it impossible to sustain an image, but the laser light energy changes air pressure in a way to keep them aloft, he said.
This photo provided by the Dan Smalley Lab at Brigham Young University in January 2018 shows a projected three-dimensional triangular prism in Provo, Utah. A study on this volumetric display was published in the journal Nature on Wednesday, Jan. 23, 2018. By shining light on specks in the air and then having the particles beam light back out, study lead author Smalley said the new technology is like “you really are printing something in space, just erasing it very quickly.” (Dan Smalley Lab, Brigham Young University via AP)
Other versions of volumetric display use larger “screens” and “you can’t poke your finger into it because your fingers would get chopped off,” said Massachusetts Institute of Technology professor V. Michael Bove, who wasn’t part of the study team but was Smalley’s mentor.
The device Smalley uses is about one-and-a-half times the size of a children’s lunchbox, he said.
So far the projections have been tiny, but with more work and multiple beams, Smalley hopes to have bigger projections.
This method could one day be used to help guide medical procedures—as well as for entertainment, Smalley said. It’s still years away from daily use.
This photo provided by the Dan Smalley Lab at Brigham Young University in January 2018 shows a projected image of the earth above a finger tip in Provo, Utah. Scientists have figured out how to manipulate tiny nearly unseen specks in the air and use them to produce images more realistic than most holograms, according to a study published on Wednesday, Jan. 23, 2018, in the journal Nature. (Dan Smalley Lab, Brigham Young University via AP)
A new metasurface composed of silicon nanodisks integrated into a liquid crystal can be electrically tuned by turning a voltage “on” and “off.” The change in voltage changes the orientation of the liquid crystal molecules, which in turn changes the optical transmission of the metasurface. Credit: Komar et al. Published by AIP Publishing
(Phys.org)—Dynamic holograms allow three-dimensional images to change over time like a movie, but so far these holograms are still being developed. The development of dynamic holograms may now get a boost from recent research on optical metasurfaces, a type of photonic surface with tunable optical properties.
In a new study published in Applied Physics Letters, a team of scientists at The Australian National University in Canberra, Australia; Friedrich Schiller University Jena in Jena, Germany; and Sandia National Laboratories in Albuquerque, New Mexico, US, has demonstrated a new way to tune optical metasurfaces.
A metasurface is a thin sheet consisting of a periodic array of nanoscale elements. The exact dimensions of these elements is critical, since they are specifically designed to manipulate certain wavelengths of light in particular ways that enhance their electric and magnetic properties.
Here, the scientists demonstrated how to manipulate a metasurface by applying an electrical voltage. By switching the control voltage “on” and “off,” the researchers could change the optical transmission of the metasurface. For instance, they could tune the transmission from opaque to the transparent regime for certain wavelengths, achieving a transmittance change of up to 75%. The voltage switch could also change the phase of certain wavelengths by up to 180°.
“We demonstrate a new technology platform that enables tuning of optical metasurfaces with large contrast by simple application of a voltage,” Dragomir Neshev, a physics professor at The Australian National University, told Phys.org. “From an application perspective, it adds to the significance that our tuning concept is based on a similar technology as used in commercial liquid crystal displays, which would largely facilitate the translation of our concept to real-world applications of tunable metasurfaces.”
The way this tuning works is that the voltage physically changes the elements of the metasurface. The metasurface is made of a square lattice of 600-nm-diameter silicon nanodisks embedded into a liquid crystal. When the voltage is “off,” the elongated molecules of the liquid crystal lie parallel to the metasurface. Turning the voltage “on” reorients the liquid crystal molecules so that they stand up perpendicular to the metasurface. Light waves interact with the metasurface differently depending on the orientation of the liquid crystal.
While other methods of metasurface tuning have been suggested, these have various drawbacks, such as that they work slowly and require assistance that makes them impractical for immediate applications. Since the new electrically tunable metasurface works quickly and simply, the researchers expect that the method could have a wide variety of applications, including dynamic holograms, tunable imaging, and active beam steering.
“Regarding a long-term vision or inspiration for the development of dynamic holographic devices, we can watch almost any science fiction movie,” Neshev said. “Most of them feature holographic man-machine interaction devices for visualization and communication purposes, where the hologram moves and changes in time based on user input.
“While we are still far from this goal, a realistic medium-term application of our metasurfaces are tunable lenses for laser microscopy applications and beam shapers with enhanced functionalities, such as polarization selective response. Active beam steering or beam shaping could be applied in communications or as components in optical laboratory setups.”
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This article and images was originally posted on phys.org
The world seems to be full of illusions—and we’re not talking about fake news from Macedonia.
Holograms appear to be all around us now. Long-dead rapper Tupac Shakur showed up at the 2012 edition of the Coachella music festival. Microsoft’s HoloLens seems akin to a wearables version of Star Trek’s holodeck, allowing its user to interact with 3D objects in an augmented reality. Startups like Edinburgh-based Holoxica can create digital 3D holograms of human organs for medical visualization purposes.
While some of these light shows are far from mere parlor tricks, none of these efforts are holograms in the sense depicted most famously in movies like Star Wars. True hologram technology is mostly still a science fiction fantasy, but earlier this year scientists revealed innovations to move the technology forward a few light years.
Holography is a broad field, but at its most basic, it is a photographic technique that records the light scattered from an object. The light is then reproduced in a 3D format. Holography was first developed in the 1940s by the Hungarian-British physicist Dennis Gabor, who won the 1971 Nobel Prize in physics for his invention and development of the holographic method.
Most holograms are static images, but scientists are working on more dynamic systems to reproduce the huge amount of information embedded in a 3D image.
The difference is in diffusion
Take the work being done by researchers at the Korea Advanced Institute of Science and Technology (KAIST).
Our ability to produce dynamic, high-resolution holograms—think Princess Leia pleading with Obi-Wan Kenobi for the Jedi’s help—is currently limited by what’s called wavefront modulators. These devices, such as spatial light modulators or digital micromirror devices, can control the direction of light propagation.
An imaging system with a short focal length lens can only create a tiny image that has a wide viewing range. Conversely, a system with a long focal length can generate a larger image but with a very narrow viewing range. The best wavefront modulator technology has only been able to create an image that is one centimeter in size with a viewing angle of three degrees.
It’s possible to do better by creating a complex and unwieldy system using multiple spatial light modulators, for example. But the team at KAIST came up with a simpler solution.
“This problem… can be solved by simply inserting a diffuser,” explains YongKeun Park, a professor in the Physics Department at KAIST. Because a diffuser diffuses light, both the image size and viewing angle can be dramatically increased by a factor of a few thousands, according to Park.
But there’s still one more problem to overcome: a diffuser scrambles light.
“Thus, in order to utilize a diffuser as ‘a holographic lens,’ one needs to calibrate the optical characteristics of each diffusor carefully,” Park says by email. “For this purpose, we use ‘wavefront-shaping technique,’ which provides information about the relationship between impinging light onto a diffuser and outgoing light.”
Park’s team succeeded in producing an enhanced 3D holographic image with a viewing angle of 35 degrees in a volume of two centimeters in length, width, and height.
“The enhancement of the scale, resolution, and viewing angles using our method is readily scalable,” he notes. “Since this method can be applicable to any existing wavefront modulator, it can further increase the image quality as a better wavefront modulator comes out in [the] market.”
Near-term applications for the technology once it matures include head-up displays for an automobile or holographic projections of a smart phone’s user interface, Park says. “[Holograms] will bring new experiences for us to get information from electronics devices, and they can be realized with a fewer number of pixels than 3D holographic display.”
Meanwhile, physicists from the Australian National University unveiled a device consisting of millions of tiny silicon pillars, each up to 500 times thinner than a human hair. The transparent material is capable of complex manipulations of light, they write.
“Our ability to structure materials at the nanoscale level allows the device to achieve new optical properties that go beyond the properties of natural materials,” says Sergey Kruk, co-lead on the research, in a press release from the university. “The holograms that we made demonstrate the strong potential of this technology to be used in a range of applications.”
The researchers say they were inspired by films such as Star Wars. “We are working under the same physical principles that once inspired science fiction writers,” Kruk says in a video interview.
Kruk says the new material could someday replace bulkier and heavier lenses and prisms used in other applications.
“With our new material, we can create components with the same functionality but that would be essentially flat and lightweight,” he says. “This brings so many applications, starting from further shrinking down cameras in consumer smart phones, all the way up to space technologies by reducing the size and weight of complex optical systems of satellites.”
And now for something completely different
Speaking of space exploration: What if the entire universe is a hologram? What does that mean for pseudo-holograms of Tupac Shakur? Not to mention the rest of us still-living 3D beings?
Theoretical physicists believe they have observed evidence supporting a relatively new theory in cosmology that says the known universe is the projection of a 2D reality. First floated in the 1990s, the idea is similar to that of ordinary holograms in which a 3D image is encoded in a 2D surface, such as in the hologram on a credit card.
Supporters of the theory argue that it can reconcile the two big theories in cosmology. Einstein’s theory of general relativity explains almost everything large scale in the universe. Quantum physics is better at explaining the small stuff: atoms and subatomic particles. The findings for a holographic universe were published in the journal Physical Review Letters.
The team used data gleaned from instruments capable of studying the cosmic microwave background. The CMB, as it’s known, is the afterglow of the Big Bang from nearly 14 billion years ago. You’ve seen evidence of the CMB if you’ve ever noticed the white noise created on an un-tuned television.
The study found that some of the simplest quantum field theories could explain nearly all cosmological observations of the early universe. The work could reportedly lead to a functioning theory of quantum gravity, merging quantum mechanics with Einstein’s theory of gravity.
“The key to understanding quantum gravity is understanding field theory in one lower dimension,” says lead author Niayesh Afshordi, professor of physics and astronomy at the University of Waterloo, in a press release. “Holography is like a Rosetta Stone, translating between known theories of quantum fields without gravity and the uncharted territory of quantum gravity itself.”
Heavy stuff no matter what dimension you come from.
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