| 摘要 |
A light source device comprises an aperture mechanism having a pair of aperture blades in an optical path formed between a light source and an incident end surface of a light guide on which an illuminating light is made incident. The first and second aperture blades are rotated, in a plane perpendicular to the optical axis of the optical path, about a movable shaft, which is parallel to the optical axis. The first and second aperture blades shade the luminous flux of the illuminating light, to adjust the amount of illuminating light, from the outer peripheries of the section of the luminous flux. A protruding plate is formed on an inside periphery of the first aperture blade. When the first aperture blade closes a half of the section, the protruding plate shades a swinging region above the center of the section of the luminous flux.
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