The holo man

An American rapper ‘performs’ at a music festival 16 years after his death, thanks to technology. But holography has a wide range of applications besides resurrecting artists. Here’s how it works. Your monthly dose of technology

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Music festivals are known to leave indelible memories in the minds of fans. But the audience of this year's Coachella Valley Music and Arts festival, which took place last week in California, will remember it as more than a musical extravaganza. The festival will go down in history for making Tupac Shakur, an American rapper par excellence from a bygone era, return to stage after almost two decades. To be precise, it will be remembered for bringing him back to life 16 years after his murder.

Coachella wasn't the first time we saw a hologram. In fact, we see them everyday — on our credit cards, voter identity cards etc. But these holograms are static and their colour schemes are restricted to different shades of red and green. Creating life-size holograms, like that of Princess Leia from Star Wars, is a totally different ball game. It involves multiple high-definition cameras taking pictures of a real scene simultaneously, every second. These pictures are wadded into data packages, which are transmitted to a holographic system through internet. Each data package, which refreshes every two seconds, is encoded into lasers, which are beamed onto a special polymer sheet. This creates a live 3D projection — a hologram — of a real time scene in a different location.

The holo-Tupac was made possible by using a modern, 3D version of the Pepper's Ghost technology, which was used by magicians during the Victorian age to create optical illusions. The Tupac 'deleb' (digital celeb) took many months to develop and, as its creators state, the process doesn't use the artist's archival footage. It is completely digital. Your monthly dose of technology

But holography is not just about bringing artists back from the grave. Today, holograms can be applied in various sectors. They can be used by countries to negotiate with terrorists or as tax stamps to prevent tax evasion; doctors can use them to perform surgeries across the globe; professors can teach in more than one class at the same time; and scientists from various countries can conduct research sitting in their own labs. In fact, some airports in France and Britain are already carrying out an experiment where 3D projections of the staff guide travellers.