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Volumetric display looks and feels real

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By eeNews Europe

What’s more, they were able to multiplex the ultrasound beam forming to add haptic feedback within the volumetric display so the object on display could be felt by a viewer reaching for it. Alternatively, driving the same transducers used for the haptic feedback, the researchers could encode most of the auditive spectrum to steer audible sound towards the viewer. This “ultrasound demodulation” was done through a upper-sideband amplitude modulation of the traps, to produces the audible sound.

The Multimodal Acoustic Trap Display (MATD) as they describe it in the paper “A volumetric display for visual, tactile and audio presentation using acoustic trapping” published in Nature was built using off-the-shelf components. I consists of two 16×16 arrays of ultrasound transducers, facing each other in a top and bottom configuration to define a working volume within which a lightweight expanded polystyrene particle (1mm in diameter) is driven by steering an ultrasound trap. High intensity RGB LEDs complete the volumetric display, driven synchronously with the particle’s movements to create a “volumetric pixel” whose changing colour across the volume yields a coloured objects through persistence of vision. For their demonstration, the researchers multiplexed the beam-forming capabilities of the ultrasound arrays (refreshed at 40kHz) to create on one hand the volumetric display and on the other hand the haptic effects (with duty cycles of 75% for levitation and 25% for tactile) or the audio content.

A geometrical description of the visual and tactile stimuli, along with sound, are used as input. The system multiplexes the position of levitation and tactile traps. A quick-scanning levitated particle and RGB illumination provide visual content while modulated acoustic pressure gives tactile feedback and amplitude modulation provides audible sound.

Although the objects rendered using the prototype display may look coarse in their presentation video, the authors anticipate that such a volumetric display could easily be improved by refreshing the ultrasound signals at higher frequencies while using smaller particles to increase the resolution and precision of the visual content. The higher frequencies would also allow the multiplexed control of three sound pressure traps to simultaneously generate directional audio with tactile feedback together with the volumetric display.

 


3D raster image of the Earth, 6.4cm in diameter (photo taken
with a 20s exposure to emulate the persistence of vision).

“Our new technology takes inspiration from old TVs which use a single colour beam scanning along the screen so quickly that your brain registers it as a single image. Our prototype does the same using a coloured particle that can move so quickly anywhere in 3D space that the naked eye sees a volumetric image in mid-air”, explained lead author Dr. Ryuji Hirayama, a JSPS scholar and Rutherford Fellow at the University of Sussex.

“Our MATD system revolutionizes the concept of 3D display. It is not just that the content is visible to the naked eye and in all ways perceptually similar to a real object while still allowing the viewer to reach inside and interact with the display. It is also the fact that it relies on a principle that can also stimulate other senses, putting it above any other display approaches”, added project leader Sri Subramanian, Professor of Informatics at the University of Sussex and a Royal Academy of Engineering Chair in Emerging Technologies.

Although the display is a good demonstrator for what can be done with ultrasound transceiver arrays, in the future the acoustophoretic board shown in the video may also be used to manipulate matter without contact, for example to mix chemicals without contaminating them, or to conduct ultrasound levitation inside tissues to accurately deliver life-saving drugs.

University of Sussex – www.sussex.ac.uk

Related articles:

UltraHaptics promises airborne tactile interfaces

Making volumetric displays out of glycerin-filled tanks

Holographic-like video conferencing: a killer app for AR?


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