Scientists create Star Wars-style Holograms

A three-dimensional hologram-like image that users can reach out and touch have been achieved for the first time, using hundreds of silent speakers to levitate tiny particles of polystyrene. Creating an effect much like the displays seen in science-fiction movies such as Star Wars, the technology, inspired by the movies, is a step into the imagined future. Researchers at the University of Sussex, UK, built the 'hologram' producing machine from 512 speakers set into a plinth above and below where the image appears.

Ultrasound is emitted by the speakers, lifting tiny balls of polystyrene precisely into position by manipulating the sound waves - to 'trap the particles acoustically'. By controlling and shifting air pressure using the speakers the balls can be so quickly maneuvered to trace a 3D shape that they appear to be a 3D moving image - they float in pockets of low pressure created by the ultrasound. The tracing of the 3D shape desired by the polystyrene balls must be done in less than 0.1 seconds for the visual effect to materialize.

Ryuji Hirayama, who developed the technology after being inspired by the use of holograms or 'volumetric systems' in popular culture, called the levitation 'like magic'. Researchers created the 3D moving image of a butterfly fluttering its wings along with a rotating Earth. Although it is not a hologram-like the technology imagined in Star Wars when Princess Leia appeals to Obe-Wan Kenobi for help, the new levitation technique offers a wider breadth of possibilities. True holograms - a physical structure that diffracts light into an image - are created by recording scattered light with a split laser beam on to a recording medium - and then shining light through it to create what appears to be a 3D image. However, with current hologram technology, key elements of display size, viewing angle, frame rate and depth of image are restricted. The effect produced by the researchers, named acoustic levitation, has an element touch and can simulate the feel of skin, as featured in many science-fiction films.

Due to the difference in pressure created by the speakers, those who reach out to touch it will 'feel' the image - or the area of high pressure. This could not be achieved with more typical methods used to create a 3D image, including traditional holography (which is the technology imagined by the movies), optophoretics, plasmonics or lenticular lenslets. Because the particles are suspended by sound, they can then make the 'hologram' emit sound, and give tactile feedback when you touch it. Coloured images can be created by shining various beams of light onto the polystyrene. According to the team, 'The prototype demonstrated in the work brings us closer to displays that could provide a fully sensorial reproduction of virtual content.'

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