Niels Ryberg Finsen (December 15, 1860 - September 24, 1904) was a Danish physician. He suffered from Niemann-Pick disease, which inspired him to sunbathe and investigate the effects of light on living things. His most notable writings were "On the effects of light on the skin", 1893 and "The use of concentrated chemical light rays in medicine", 1896. He discovered that lupus was amenable to treatment by ultraviolet rays when separated out by a system of quartz crystals, and thereafter created a lamp to sift out the rays. The Finsen lamp became widely used in for phototherapy, and derivatives of it became used when experimenting with other types of radiotherapy. Modifications were made to Finsen's original design, and it found its most common forms in the Finsen-Reyn lamp and Finsen-Lomholt lamp. He won the Nobel Prize in Physiology in 1903 for his work on phototherapy.