[Mitch]

Scientists have known since the 1940s that some people can see near-infrared light as if it were visible light. But the mechanism of IR vision has remained uncertain. Now, Krzysztof Palczewski of Case Western Reserve University and an international team report that human IR vision probably works via a mechanism in which two-photon absorption activates the light-sensitive protein rhodopsin within the eye (Proc. Natl. Acad. Sci. USA 2014, DOI: 10.1073/pnas.1410162111).

Read full story here: Humans See IR Light When Photons Double Up