Patent ID: 7972013

Claim:
A light source, comprising: an arc tube which emits light; a reflector which reflects the light emitted from the arc tube; and a holding unit which holds the reflector, wherein: the holding unit has plural air supply ports through which cooling air is introduced into the light source on the light emitting side of the arc tube, and a first rectifying portion which guides cooling air having been supplied from an air supply port of the plural air supply ports and passed through the light emitting side of the arc tube toward an area above the arc tube, the holding unit has a switching unit which changes the flow of cooling air by opening or closing the plural air supply ports, the switching unit has a shutter ring for opening and closing the plural air supply ports, the shutter ring having plural openings disposed at positions corresponding to the plural air supply ports located below the arc tube and an air hole through which cooling air is exhausted, the switching unit changes the flow of cooling air by rotation of the shutter ring which locates an opening of the plural openings of the shutter ring at a position corresponding to the air supply port of the plural air supply ports disposed below the arc tube.