By Robert F. Service
Forget light sabers. Researchers on Earth have invented something far flashier: a Star Wars-like 3D display that simultaneously projects video, sound, and even the sensation of touch. The new displays can’t create holograms as complex as Princess Leia’s famous distress call. But with further improvements, they could transform virtual reality, providing users a multisensory experience without headsets or other cumbersome gear.
“They did an amazing job with this,” says Asier Marzo, a computer scientist at the University of Navarra in Pamplona, Spain, who was not involved with the work. Future versions, he says, could give doctors 3D views of tumors inside the body or provide soldiers with an accurate depiction of what lies ahead. “It has the potential to revolutionize the display ecosystem,” Marzo says.
There are already many ways to create 3D movies, including headsets that project a sequence of slightly different images to our two eyes to fool us into experiencing the sensation of depth. A newer, less-cumbersome alternative projects laser light on a vibrating screen, giving viewers the impression of seeing a moving 3D image. But it can’t project sound. And if viewers try to touch the images, they could wind up with nasty burns from the laser light.
To add sound and touch, scientists put their own spin on a technique first reported this year by Marzo and his colleagues. It projects light onto a tiny plastic bead moving rapidly through a space the size of a coffee cup. Scientists move the bead using ultrasound waves; like sound waves, we can hear, the ultrasound waves compress and decompress the air as they travel, creating regions of low and high pressure. Where several ultrasound waves converge on a single point, they can create a low-pressure spot that traps the bead, suspending it in midair. And by using an array of computer-controlled speakers surrounding the bead, researchers can move it continuously at nearly 9 meters per second.
Marzo’s team steer its bead repeatedly throughout the space and project red, green, and blue light onto it from nearby LEDs. The light becomes visible only when it bounces off of the bead. And because this occurs faster than the eye can see, it gives viewers the impression that they are seeing moving 3D pictures, Marzo and colleagues reported in August in Applied Physics Letters.
Now, researchers led by display expert Sriram Subramanian at the University of Sussex in the United Kingdom have upped the complexity of the ultrasound display creating larger, more complex images. They have also added sound—and touch.
They started with 512 ultrasound speakers (compared with Marzo’s 60) arranged above and below a space about the size of a toaster oven. The speakers could propel the particle through the volume 100 times per second, 10 times faster than in Marzo’s display, which produces a more-rapid image refresh. That allowed them to create complex moving images—such as a rotating depiction of Earth and butterflies flying through space (above).
To add sound, the researchers tweaked the ultrasound coming from their speakers so the emanating sound waves interacted and produced audible frequencies. To add touch, they used a similar approach. An infrared sensor on the display spots a person’s hand reaching forward and triggers sound waves to converge at the spot, creating pressure that can be felt by the skin, they report today in Nature. “People describe it like blowing on your skin or a tickling sensation,” says co-author Diego Martinez Plasencia, a computer scientist at Sussex.
Marzo is impressed: “Their results are 10 times better than ours.” And that progress is likely to be repeated, he says. More powerful ultrasound speakers, more complex arrays, and improved software algorithms could combine for rapidly improved 3D displays. Fear not Leia, the Rebel Alliance is on its way.
Source: Science Mag