Discharge bulb

摘要

A discharge bulb including an arc tube 16 having a light-emitting tube portion 20a and shroud glass 18 surrounding the arc tube 16 in a tubular form. An inert gas and metal halides are sealed in a discharge space 24 inside the light-emitting tube portion 20a, which is mercury-free. Xenon gas is filled in an annular space 34 between the arc tube 16 and the shroud glass 18. Heat is restrained from being transmitted from the light-emitting tube portion 20a to the shroud glass 18 through the annular space 34. An increase in the heat loss and the temperature rise of the shroud glass 18 are restrained.