Scientists have created a flat lens that is 10 times thinner than the width of a human hair and millions of times thinner than camera lenses available today. Here, Professor Rajesh Menon holds up the prototype. Researchers from the University of Utah developed a new method of creating optics that are flat and thin, yet can still perform the focus light to a single point – the basic step in producing an image.
By doing this, they have overturned previous conceptions that flat, ultra-thin optical lenses for cameras or other devices were impossible because of the way all the colours of light must bend through them.
‘Instead of the lens having a curvature, it can be very flat so you get completely new design opportunities for imaging systems like the ones in your mobile phone,’ explained Professor Rajesh Menon, an electrical and computer engineer who led the work.
‘Our results correct a widespread misconception that flat, diffractive lenses cannot be corrected for all colours simultaneously.’
In order to capture a photographic image in a camera or for our eyes to focus on an image through gasses, different colours of light must pass through the lenses and converge to a point on the camera sensor or on the eye’s retina.
How light bends through curved lenses is based on the principal of refraction, where light travels at different speeds through materials of different density. It is this that causes a pencil to appear to ‘bend’ when it is placed into a glass of water.
But Professor Menon found a way to design an ultra-thin flat lens by using diffraction, in which light interacts with microstructures in the lens and bends.
‘In nature, we see this when you look at certain butterfly wings. The color of the wings is from diffraction. If you look at a rainbow, it’s from diffraction,’ Dr Menon said.