To solve such problems that, when directly looking a light source with high luminance by an optical system, the focused luminous flux is once focused near an aperture, the temperature of lightweight resin aperture blades increases to cause deformation and dissolution of the blade surfaces and the aperture blades become inoperative.

A second aperture blade having higher heat resistance than that of a first aperture blade is disposed in front of the first aperture blade. The aperture of the second aperture blade is controlled to protect the first aperture blade from light with high luminance, thereby blocking the application of light to the first aperture blade.