Wood's lamp.

Wood’s lamp was invented in 1903 by a Baltimore physicist, Robert W. Wood. It was first used in dermatology practice for the detection of fungal infection of hair by Margarot and Deveze in 1925. Wood’s lamps are small, durable, inexpensive, safe and very easy to use. Although mainly used in the diagnosis of some infective and pigmentary dermatoses, they have recently been used as a diagnostic tool for certain skin cancers.