Lamp cooling device and projection display apparatus

A projection display apparatus comprising:

• a lamp including a light emission source for emitting light, a front transparent plate, a reflector for reflecting light emitted by the light emission source toward the front transparent plate, the light emission source being disposed in an intralamp space surrounded by the front transparent plate and the reflector, said lamp having a gas inlet and a gas outlet which communicate with said intralamp space;
• and
• a lamp cooling device for cooling said lamp;
• wherein said lamp cooling device including
• a duct having joint ports defined in respective opposite ends thereof and communicating with said gas inlet and said gas outlet, respectively, said duct having a continuously extending portion between said opposite ends which is disposed in a space outside of said intralamp space, for circulating a gas through said duct and said intralamp space in isolated relation to the space outside of said intralamp space.