Ultrasonic waves focus to form a 'shape' in air The power of ultrasonic waves has been harnessed to produce "virtual" objects in mid-air. The field of haptics - integrating computing and the sense of touch - has been around for some time but has required gloves or mechanical devices to impart a sense of feeling. Now, a team of Japanese researchers has developed a system that uses focused ultrasound to do the job. Its inventors may soon commercialise the approach. Sense and sensibility With the expansion in multimedia on the web, our eyes and ears are flooded with sensory information, but the sense of touch has been largely left behind. The popularity of vibrating gaming handsets has proven that it is a rich but untapped way to increase interaction. Takayuki Iwamoto and colleagues from the University of Tokyo have now demonstrated a simple haptic device that employs a number of ultrasonic transducers, which emit ultrasound. Sound is a pressure wave, meaning that as the inaudible sound waves from each of the transducers interfere, they can create a focal point that is perceived as a solid object. The team's prototype system includes a camera which tracks the position of a user's hand and shifts the output from the transducers to move the focus around with the hand. The result is a feeling of tracing the edge or surface of the virtual object. At the moment, the system provides a small force only in the vertical dimension, but the team is improving the geometry of the array and the amount of power it can produce so that future devices will provide a stiffer feel and more contoured objects. It's great to have something that you can just walk up and use

Stephen Brewster Prof Iwamoto envisions marrying the approach with 3-D modelling software and video games, and says that the team "received several proposals from industrial companies" when the prototype was demonstrated at a conference in California last month. The system is "the first of its kind", according to haptics researcher Stephen Brewster of the University of Glasgow. "You can feel it with both hands, rather than having just a single point of contact, and multiple people can use it at the same time," Prof Brewster says. "The kinds of things we use are connected through mechanical arms or you're wearing some kind of exoskeleton. "It's great to have something that you can just walk up and use and not need any other kind of hardware you have to hold or wear." The team is working to adjust how the transducers are driven in order to produce realistic textures as well as shapes. However, the approach is limited in how much force it can produce, which in turn limits how hard or stiff the virtual objects can be. Beyond a certain amount of force, the device could scatter enough ultrasound to risk ear damage.



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