Illustration of how the metallens modeled on the compound lens of a trilobite simultaneously focuses the object both near (rabbit) and far (tree).Inspired by the eyes of trilobites 500 million years ago, researchers have developed a miniature camera with a bifocal lens with unprecedented depth of field.The camera can simultaneously take images of objects as close as 3 centimeters and as far away as 1.7 kilometers.The team at the US National Institute of Standards and Technology (NIST) devised a computer algorithm to correct for aberrations, sharpen objects at intermediate distances between these near and far focal lengths, and generate a final focused image that covered this enormous depth of field.Integrating nanometer-scale photonics technology with software-based photography, these lightweight, deep-depth-of-field cameras promise to revolutionize future high-resolution imaging systems.In particular, the cameras would greatly increase the ability to produce highly detailed images of urban landscapes, groups of organisms that occupy a large field of view, and other photographic applications where near and far objects must be in sharp focus.All trilobites had a wide range of vision, thanks to compound eyes: single eyes made up of tens to thousands of small, independent units, each with its own cornea, lens, and light-sensitive cells.But one group, Dalmanitina socialis, was exceptionally farsighted.Their bifocal eyes, each mounted on stalks and composed of two lenses that bend light at different angles, allowed these sea creatures to simultaneously see prey hovering nearby and distant enemies approaching from more than a kilometer away.Based on this example from nature, the new lenses have been developed, which are presented in Nature Communications.The researchers made a series of tiny lenses known as metalenses.These are ultrathin films etched or printed with clusters of nanoscale pillars designed to manipulate light in specific ways.To design their Metalans, Agrawal and his colleagues studded a flat glass surface with millions of tiny, nanometer-scale rectangular pillars.The shape and orientation of the constituent nanopillars focused light in such a way that the metasurface simultaneously acted as a macro lens (for close objects) and a telephoto lens (for distant objects).Specifically, the nanopillars captured light from a scene of interest, which can be divided into two equal parts: left-circularly polarized and right-circularly polarized light.(Polarization refers to the direction of a light wave's electric field; left circularly polarized light has an electric field that rotates counterclockwise, while right circularly polarized light has a electric field rotating clockwise).The nanopillars bent left and right circularly polarized light by different amounts, depending on the orientation of the nanopillars.The team arranged the nanopillars, which were rectangular, so that some of the incoming light had to travel through the longest part of the rectangle and some through the shortest part.On the longest path, the light had to pass through more material and thus experienced more bending.For the shortest path, light had less material to travel, and therefore less curvature.Light that is bent by different amounts is brought to a different focus.The greater the flex, the closer the light is focused.In this way, depending on whether the light travels through the longest or shortest part of the rectangular nanopillars, the metallens produces images of both distant (1.7 kilometers) and close (a few centimeters) objects.However, without further processing, that would leave objects at intermediate distances (several meters from the camera) out of focus.Agrawal and his colleagues used a neural network, a computer algorithm that mimics the human nervous system, to teach software to recognize and correct defects such as blurriness and color aberration in objects that resided midway between near and far focus. of the metalenses.The team tested their camera by placing objects of various colours, shapes and sizes at different distances in a scene of interest and applying software correction to generate a final image that was in focus and free of aberrations over the full kilometer range of depth of field.The team's developed metalens increase light-gathering ability without sacrificing image resolution.Also, because the system automatically corrects for aberrations, it has a high tolerance for error, allowing researchers to use simple, easy-to-fabricate designs for the miniature lenses, Amit Agrawal, one of the authors of the study, said in a statement. the investigation.