#lightfield
"Inspired by the optical structure of a Cambrian-era sea creature, the Dalmanitina socialis trilobite, researchers have developed a camera that can focus on the near and the far at the same time. The nanophotonic light-field camera relies on a bifocal metalens array that can capture high-resolution light-field images with a depth of field from the centimeter to the kilometer scale."
"Among the various trilobite groups, one trilobite, Dalmanitina socialis, possessed a unique visual system with compound eyes composed of two optically homogeneous lens units of different refractive indices -- an upper lens unit with a central bulge made of calcite and a lower lens unit made of an organic compound. As a result, each compound eye of Dalmanitina socialis is able to simultaneously focus incident light to a near and a far point, analogous to a coaxial bifocal lens, which may enable them to be sensitive to light-field information with large depth-of-field, and clearly see both close (e.g., floating preys) and distant (e.g., approaching enemies) objects in the environment."
"The researchers used a metalens, a flat lens technology, that focuses light by means of what are called metasurfaces. Optical metasurfaces work on the sub-wavelength level, employing small nanostructures to scatter light instead of the conventional refraction and propagation of light seen with glass optics. These nanostructures capture and re-emit light with unheard-of accuracy because they are able to define the phase, spectrum, polarization, and modality of light."
Polarization is key to how the camera works. They key thing is the manufacturing technique, which enables making the nanoscale grid with the nanopillars which are arranged diagonally within the cells of the nanoarray. Their orientation determines the polarization of the light that passes through. How exactly this is used later to create the image isn't clear to me. The system also requires a neural network, which is a convolutional neural network. It corrects for nonuniform optical aberrations, mainly chromatic and comatic aberrations (aberrations analogous to lens dispersion aberrations), introduced by the metalens.
"In nature, optical aberrations also commonly exist in the optics of biological visual systems, including human beings. The perceived appearance, however, does not display such aberrations due to the neural adaptation/processing-induced aberration tolerance of the visual system."
New light field camera can focus up-close and far away simultaneously
