https://news.wisc.edu/new-imaging-syste ... taneously/
"In the new system, a nanocrystal “down-converts” ultraviolet light to the longer wavelengths of the visible green spectrum while the optics surrounding it ensure that each incoming UV ray becomes a single visible ray. This conversion of one ray into one ray is crucial — without it, you would just see a big green blur. Visible light passes through the optical system largely unaltered, enabling simultaneous vision in the UV and in the visible."