New technology creates “Star Trek” -like holograms with sound and tactile feedback
“Hologram” technology becomes real: Researchers have developed holograms that combine moving 3D images with sound and tactile feedback. When you reach into such a hologram, you feel a resistance and tingling, as the scientists report in the journal “Nature”. This is made possible by acoustic levitation: Ultrasonic waves move tiny illuminated particles and at the same time generate sounds and key impressions.
Whether the holodeck of the “Star Trek” spaceships or the projection of Princess Leia in the first “Star Wars” film: holograms are almost commonplace in science fiction, but so far the reality lagged behind. Although there are already laser technologies that can produce holographic videos and holograms with amazingly large depth of field . Also free-floating projections as in the “Star Wars” movie researchers have already developed.
Hologram becomes multimodal
But one crucial component was missing so far: The holograms were not tactile. While you can interact with the projections in the “holodeck” of science fiction spaceships and feel them, holograms lacked this tactile feedback. Even the combination with a three-dimensional, emanating from the hologram sound was not readily possible.
Now, however, Ryuji Hirayama of the University of Sussex and his colleagues have addressed this shortcoming. They developed a hologram that produces both 3D sound and tactile feedback. The basis of their “Multimodal Acoustic Trap Display” (MATD) is the method that enabled the free-floating projections in 2018. In this tiny particles are moved by laser beams and illuminated – thus creating the hologram.
Acoustic “tractor beam” for the 3D image
However, Hirayama and his team have modified this technique: instead of using laser beams, they control the tiny hologram particles by means of acoustic levitation – a kind of tractor beam made of ultrasonic waves. The sound pressure of an acoustic field keeps the particle in suspension and moves it. Up to 100 times a second, the particle changes its position and is illuminated by LED light – the result is the three-dimensional image.
The prototype of this holography system is about the size of a microwave and consists of 512 ultrasound speakers arranged around a free space. In the first tests, the researchers generated moving and colored holograms of letters, tangled rings, a magic cube and a rotating globe. Although the resolution is still rather crude, but designed Hirayama and his team their prototype only from cheap, freely available on the market components – it is therefore still air up, as they emphasize.
Sound and taste impression through sound manipulation
The decisive advantage, however: since the hologram is generated by means of sound, it can also be used for non-visual effects – sound and tactility. “Ultrasound is not audible, but it transports energy through the air. Our prototype controls and focuses this energy and can thus create sound or irritate our skin so that we touch something, explains Hirayama’s colleague Diego Martinez Plasencia.
For tactile feedback, Hirayama and his team focus on ultrasonic waves: an infrared sensor detects when, for example, a finger approaches the hologram and adjusts the speakers so that the sound pressure concentrates on the fingertip. At a – inaudible – sound pressure of over 150 decibels, this creates a slightly tingling feeling of pressure – one has the feeling of feeling the hologram.
For the 3D sound, the researchers adjust the ultrasound waves in such a way that resonance effects are created in the hologram. These produce an audible sound – in the first test, these were still rather simple sounds.
On the way to the ultimate hologram
“Our MATD system is revolutionizing the concept of 3D imaging,” says project leader Sri Subramanian from the University of Sussex. Because it does not allow only holograms that are moving and visible to the naked eye. “It also uses a principle that can also stimulate other senses. This is ahead of all previous holographic approaches, bringing us closer to the vision of the ultimate 3D display. “
As the researchers emphasize, their technique is still much better. Higher frequencies, stronger ultrasound speakers, and optimized control software will allow for more complex, higher-resolution renderings, as well as stronger sounds and key impressions. “Although we are not quite up to the technical abilities of the Star Wars rebels, our prototype is pretty close,” notes Hirayama.
Source: University of Sussex, Nature