Patent ID: 8167796

Claim:
An endoscope light source unit for making illumination light from a main light source incident on an incident end face of a light guide connected to said endoscope light source unit, said endoscope light source unit comprising: a rotary aperture plate provided between said incident end face and said main light source at a position to intercept a light-source optical path, a plurality of aperture openings of different opening ratios and an auxiliary-light aperture opening of a maximum opening ratio being formed in said rotary aperture plate at predetermined intervals circumferentially about a center of rotation of said rotary aperture plate to regulate a light quantity of an incident light on said incident end face by selectively positioning one of said plurality of aperture openings in said light-source optical path; a rotating device for rotating said rotary aperture plate; an auxiliary light, freely movable between an inserted position, in which said auxiliary light is positioned in said light-source optical path between said rotary aperture plate and said main light source, and a retracted position, in which said auxiliary light is positioned outside of said light-source optical path, light emitted from said auxiliary light being lower in intensity than said main light source; a first sensing portion and a plurality of second sensing portions which are formed in said rotary aperture plate in association with said auxiliary-light aperture opening and said plurality of aperture openings, respectively; a first sensor which detects said first sensing portion when a specific one of said plurality of aperture openings is positioned in said light-source optical path; a second sensor which detects said first sensing portion when said auxiliary-light aperture opening is positioned in said light-source optical path, and detects said plurality of second sensing portions when said plurality of aperture openings other than said specific one aperture opening are positioned in said light-source optical path, respectively; and a controller which drives said rotating device to rotate said rotary aperture plate in one of forward and reverse directions, and stops driving said rotating device to stop said rotary aperture plate in accordance with a state of detection of at least one of said first sensor and said second sensor; wherein, when said auxiliary light is in said retracted position, said controller does not allow the rotary aperture plate to stop at a position where said second sensor detects said first sensing portion.