The UltraHaptics system provides multi-point haptic feedback in mid-air above an interactive screen

Ultrasound system provides contactless tactile feedback

A system that allows people to experience multi-point tactile feedback without having to touch any device will be unveiled on Friday.

A team from the University of Bristol’s Interaction and Graphics (BIG) research group have created a system that provides tactile, or haptic, feedback in mid-air above an interactive touch surface using an array of ultrasonic transducers.

Multi-touch surfaces offer easy interaction in public spaces, with people being able to walk-up and use them, but presently people cannot feel what they have touched. The Bristol team’s UltraHaptics system will allow people to not only feel what is on the screen, but also receive invisible information before they touch it.

Tom Carter, PhD student in the Department of Computer Science’s BIG research group, said: “Current systems with integrated interactive surfaces allow users to walk up and use them with bare hands. Our goal was to integrate haptic feedback into these systems without sacrificing their simplicity and accessibility.”

In the research paper, to be presented at the ACM Symposium on User Interface Software and Technology (UIST) 2013, the team explain how the system relies on the principle of acoustic radiation force.

The new technique relies on a phased array of ultrasonic transducers, which are used to exert forces through ultrasonic vibrations on a target in mid-air, projecting haptic sensations through a screen and directly onto the user’s hands.

The transducers emit very high frequency sound waves and when all of the sound waves meet at the same location at the same time, they create sensations on the user’s skin.

By carrying out technical evaluations, the team have shown that the system is capable of creating individual points of feedback that are far beyond the perception threshold of the human hand. The researchers have also established the necessary properties of a display surface that is transparent to 40kHz ultrasound.

Carter said: “We have designed a system with an ultrasound transducer array positioned beneath an acoustically transparent display.

“This arrangement allows the projection of focused ultrasound through the interactive surface and directly onto the users’ bare hands. By creating multiple simultaneous feedback points, and giving them individual tactile properties, users can receive localised feedback associated to their actions.”

The results from two user studies have demonstrated that feedback points with different tactile properties can be distinguished at smaller separations. The researchers also found that users are able to identify different tactile properties with training.

The research team explored three new areas of interaction possibilities that UltraHaptics can provide: mid-air gestures, tactile information layers and visually restricted displays, and created an application for each.

For a video demonstrating UltraHaptics, visit the E&T Magazine Facebook page.

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