Polarization image sensors: Learning from biology to make the invisible visible

Some animals, such as crustaceans, arthropods, insects and aquatic creatures can detect a characteristic of light - polarization, that is invisible to humans. Different approaches of polarization imaging in the visual region have been proposed in the literature that employ precise but bulky optical devices. In recent years, taking advantage of nano-fabrication, researchers began integrating polarization films at the focal plane of standard image sensors. In addition, the development of nano-scale CMOS technology enables the integration of a standard pixel array with metallic wire-grid at the scale of the wavelength of visible light. Monolithic wire-grid polarization image sensor designs have been reported in the last few years, which is promising to be employed as a compact, portable, smart polarization detection device to extend the human visual ability.