DSLR Photography Forum

This article in the New Scientist describes how a Professor 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.

http://www.newscientist.com/article/mg20...sight.html

Quote: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 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.

The research is mainly catered towards the field of optometry, where it could help people who wear bifocal lenses do away with the split lens system. However, he says he has also "fitted one of his lenses to a cellphone camera to confirm the extended focus effect".

One side effect is that the interference pattern cancels some of the light coming through, leading to reduced contrast.

I wonder whether photography could take advantage of this - could we have lenses that don't need to be stopped down to get a large DOF?

Reduced contrast is an issue. I had Lasik surgery on my left eye many years ago, and although I see much better, the reduced contrast in that eye makes reading difficult on pages where the ink is grey and the paper not clear white. Net gain to the operation - but it makes me leary of reduced contrast techniques.

Quote > where it could help people who wear bifocal lenses do away with the split lens system.< unquote

Like varifocal ?

NT73 Wrote:Like varifocal ?

I'm not sure - my understanding of varifocal is that there is still a graduation of the lens - i.e. one portion is used for long distances, another portion is used for close up and there may be a variation in between.

From my reading of the article, this lens creates a super-depth of field so everything is in focus all at once...

Yes, you are right ST. Bifocal have two distinct focal lengths. Varifocals have a variable lens from close to distance, but there is a portion (the close up) which is the start point and going to distance radiates from this to the edges of the lens. Up, down,or sideways. The 'close up bit' can be anywhere on the lens.
The lens starts off at around 100-125 mm diameter. :/
I will have to have a word with my spectacle man and see if I can get a discount. 3 for the price of 2.