A team of researchers from the University of Utah has designed an ultra-thin flat lens with a remarkable depth of focus spanning several metres.
In a paper titled “Extreme-depth-of-focus imaging with a flat lens” published and available online in the Optical Society of America’s journal Optica, the researchers describe a very thin lens that does not require refocusing to sharply capture images of objects separated by large distances, removing the need for refocusing mechanisms and drastically simplifying imaging systems.
The MDL (multilevel diffractive lens) described in their paper enhances the depth of focus by over 4 orders of magnitude compared to traditional fixed lenses.
In experiments, the researchers were able to maintain focus for objects separated by as large a distance as 6 metres. When illuminated by collimated light at 0.85m, a ø1.8-mm MDL shaped with a distribution of concentric rings of varying thickness up to 2.6 µm, produced a beam which remained in focus from 5 mm to 1.2 m.