A light source comprises a lamp such as an ultra-high pressure mercury lamp or a metal halide lamp and its irradiated light is emitted after being parallelized by a parabolic reflector. The parabolic reflector is made by pressing metal such as stainless and its light exit side aperture is covered with a transparent plate made of glass, etc. The transparent plate prevents fragments of glass of the lamp and the like from scattering when the lamp bursts. The parabolic reflector does not have an aperture (cut-out) for ventilation, but heat radiation fins are formed on the outer surface of it.