marți, octombrie 05, 2010

Scratched glasses give perfect vision for any eyesight

Zeev Zalevsky at Bar-Ilan University in Ramat Gan, Israel, has developed a technique to turn a standard lens into one that perfectly focuses light from anything between 33 centimetres away and the horizon.

It involves engraving the surface of a standard lens with a grid of 25 near-circular structures each 2 millimetres across and containing two concentric rings. The engraved rings are just a few hundred micrometres wide and a micrometre deep. "The exact number and size of the sets will change from one lens to another," depending on its size and shape, says Zalevsky.

The rings shift the phase of the light waves passing through the lens, leading to patterns of both constructive and destructive interference. Using a computer model to calculate how changes in the diameter and position of the rings alter the pattern, Zalevsky came up with a design that creates a channel of constructive interference perpendicular to the lens through each of the 25 structures. Within these channels, light from both near and distant objects is in perfect focus.

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