Five hundred million years ago, the oceans teemed with trillions of trilobites – an extinct group of marine arthropods ruling the seas for more than 270 million years. Over 20,000 species having been described to this day.
All trilobites had a wide range of vision, thanks to compound eyes — single eyes composed of tens to thousands of tiny independent units, each with their 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 calcite lenses that bent light at different angles, enabled these sea creatures to simultaneously view prey floating nearby as well as distant enemies approaching from far away.
Inspired by the eyes of D. socialis, researchers at the National Institute of Standards and Technology (NIST) have developed a miniature camera featuring a bifocal lens with a record-setting depth of field — the distance over which the camera can produce sharp images in a single photo. The camera can simultaneously image objects as close as 3 centimeters and as far away as 1.7 kilometers.
The researchers fabricated an array of tiny lenses known as metalenses specifically designed to manipulate light in specific ways. Like the crystalline structure of the trilobite lenses, the researchers designed the metalenses to be made of millions of tiny, rectangular nanometer-scale titanium-oxide pillars. The shape and orientation of the nanopillars focus light in such a way that they simultaneously act as a macro-lens (for close-up objects) and a telephoto-lens (for distant ones).
A special software is used to generate a final image and to correct for defects such as blurriness and color aberration.
The metalenses and software can be used to develop new high-tech camera systems. Such lightweight, large-depth-of-field cameras promise to revolutionize future high-resolution imaging systems. In particular, the cameras would greatly boost the capacity to produce highly detailed images of landscapes and to capture in a single shoot objects of various colors, shapes and sizes.
NIST researchers Amit Agrawal and Henri Lezec, along with their colleagues from the University of Maryland in College Park and Nanjing University, describe their work online in the April issue of Nature Communications.