Optical scientists have long been fascinated by the visual system of the mantis shrimp, a marine crustacean whose eyes process information about both the color and the polarization of light. Those capabilities have served as inspiration for a number of optical devices designed extract both 3-D spatial and polarization information simultaneously. But it’s been tough to wedge both features into a compact optical package.
A research team in China now proposes a novel approach to capturing both types of image data in a single shot (ACS Nano, doi: 10.1021/acsnano.9b07104). The team’s “4-D” approach relies on a clever, concentric configuration of liquid-crystal (LC) microlenses that allows information on depth and polarization to be determined based on which microlens within the array provides the sharpest image of the target. While at present the design constitutes only a proof of principle, the researchers believe it could ultimately prove useful in applications ranging from medical imaging and remote sensing to information encryption.
One reason it’s been difficult to get to a lens that can process both 3-D depth and polarization information is that the sensing of the two relies on different properties—the spatial refractive-index distribution in the case of depth focusing, and characteristics such a birefringence in the case of polarization.