The need to refocus a camera when zeroing in on multiple objects at different distances may be eliminated with a new flat lens designed by researchers from the University of Utah and San Diego-based Oblate Optics Inc. The lens uses nanostructures patterned on a flat surface instead of conventional bulky glass or plastic to achieve the important optical properties that control the way light travels.

The thin lens is marked with concentric rings filling an aperture 1.8 mm in diameter, and a photoresist procedure was used to inscribe the design onto a glass substrate 0.6 mm thick. The nanofabricated flat multilevel diffractive lens (MDL) was demonstrated in tests conducted with infrared light and relatively low numerical aperture to enhance the depth of focus by over four orders of magnitude relative to that achieved with an equivalent conventional lens. The flat lens was shown to maintain focus for objects that are about 6 m apart from each other.

The design approach described in Optica could be applied to the realization of optical components with extreme bandwidth or lower cost. Reduced weight and complexity of the lens might also translate into thinner smartphone cameras, smaller cameras for biomedical applications and more compact cameras for automobiles.

The MDL will next be extended to larger numerical apertures and tested with the full visible light spectrum.