Harry Potter’s invisibility cloak was magic, but scientists have recently developed several ways to make objects invisible.

Most of those methods use expensive technology, but researchers at the University of Rochester (USA) have come up with a better way that uses only four lenses.

Lenses are transparent and shaped so that they change the direction of light, which travels in a straight line.  `The basic idea is to take light and have it pass around something as if it isn’t there,’ said John Howell, a professor of physics.

With graduate student Joseph Choi, Professor Howell developed a combination of four standard lenses that keeps an object hidden.

`Many cloaking designs work fine when you look at an object straight on, but if you move your viewpoint even a little, the object becomes visible,’ he said. Their setup works so long as the viewer stands in the right place, or close by.

They calculated carefully the lenses needed and the necessary distance between them. To test their device, they placed the object in front of a grid background.

As they looked through the lenses and changed their viewing angle by moving from side to side, they could see just the grid as if the object wasn’t there.  Previous devices also caused the background to shift, giving the game away, Choi explained.