Lenses are used in many optical devices from eyeglasses to cameras and telescopes. Lenses are typically made from glass, plastic or other clear materials that are ground to control how light passes though them.
Engineers at Duke University have created a new generation of lenses that is expected to improve the capability of telecommunications gear and radar systems that doesn't use traditional construction methods. The new lens isn’t made from a clear material, it is constructed of a metamaterials arranged in a method similar to Venetian blinds.
The exotic metamaterial construction allows the team to engineer a lens that has properties not readily found in natural materials. The prototype lens is 4" x 5" and less than an inch high. The construction of the prototype consists of over 1,000 pieces of the same fiberglass material that is used to make circuit boards, then it's etched with copper. The fiberglass pieces are then arranged in parallel rows capable of directing rays as they pass through.
Researcher Nathan Kundtz said, "For hundreds of years, lens makers have ground the surfaces of a uniform material in such a way as to sculpt the rays as they pass through the surfaces While these lenses can focus rays extremely efficiently, they have limitations based on what happens to the rays as they pass through the volume of the lens." He continued saying, "Instead of using the surfaces of the lens to control rays, we studied altering the material between the surfaces. If you can control the volume, or bulk, of the lens, you gain much more freedom and control to design a lens to meet specific needs."
The new lens has a view of about 180 degrees making it wide angle and with its flat focal point it can be used with standard imaging technologies. Researchers have previously worked on other lens options like those known as gradient index (GRIN) lenses. This type of lens is spherical and is difficult to work with because a spherical image doesn’t translate to a flat surface well. The new lens developed at Duke may eventually be used for 3D images as well.
The researchers believe that the metamaterial lenses could one day replace traditional optical systems that need large lens arrays to provide clear images. The new lens can also be used to direct beams inside a radar array, something lenses today can’t do within practical size limitations.
Professor David R. Smith from Duke University said, "We've come up with what is in essence GRIN on steroids. This first in a new class of lenses offers tantalizing possibilities and opens a whole new application for metamaterials." He continued, "While these experiments were conducted in two dimensions, the design should provide a good initial step in developing a three-dimensional lens. The properties of the metamaterials we used should also make it possible to use infrared and optical frequencies."