Polarization is the direction in which light vibrates. It provides a lot of information about the objects with which it interacts. This includes aerosols in the atmosphere to the magnetic field of stars. Because this quality of light is invisible to human eyes, engineers have relied on specialized, expensive and bulky cameras to capture it.
Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a metasurface attachment. This can just about any camera or imaging system into polarization cameras. The attachment uses a metasurface of subwavelength nanopillars to direct light based on its polarization. It compiles an image that captures polarization at every pixel.
Scientists developed a compact, portable camera that used a metasurface to image polarization in a single shot, in 2019. In the new study, scientists explored how to generalize the concept of a polarization camera.
They attached the polarization metasurface to an off-the-shelf machine vision camera, to demonstrate those design rules. They simply screwed it on in front of the objective lens in a small tube that also housed a color filter and field stop. They needed to point and click to get polarization information.
The nanopillars direct light based on polarization and it formed four images. Each showed a different aspect of the polarization. The images are then put together. They gave a full snapshot of polarization at every pixel. The attachment could be used to improve machine vision in vehicles or in biometric sensors for security applications.