Endoscope light source unit

1. An endoscope light source unit for making illumination light from a light source incident on an incident end face of a light guide connected thereto, said endoscope light source unit comprising:

an aperture device having a plurality of aperture openings of different opening ratios, for selectively positioning one of said aperture openings between said incident end face and said light source;

a driving device for moving said aperture device;

an index detection device for detecting whether a specific one of said aperture openings of said aperture device is positioned between said incident end face and said light source;

an aperture opening position detection device for detecting whether any one of said aperture openings lies between the incident end face and the light source;

a measuring device for measuring a driving amount of said driving device with respect to a position of said specific one of said aperture openings; and

a controller for driving said driving device based on measurements from said index detection device, said aperture position detection device, and said measuring device.

2. The endoscope light source unit according to claim 1 , wherein said aperture device comprises a rotary aperture disc;

wherein said rotary aperture disc includes said aperture openings, a index detection hole for detecting whether said rotary aperture disc is at an initial position of rotation, and a plurality of aperture position detection holes for detecting whether any one of said aperture openings lies between said incident end face and said light source, said aperture openings being formed at regular intervals circumferentially about the center of rotation of said rotary aperture disc;

wherein said index detection device includes an index sensor for detecting said index detection hole when the rotary aperture disc is at the initial position of rotation; and

wherein said aperture opening position detection device includes an aperture position sensor for detecting whether any one of the aperture openings lies between said incident end face and said light source.

3. The endoscope light source unit according to claim 2 , wherein said driving device comprises a stepping motor for driving said rotary aperture disc to rotate step by step in units of a predetermined angle;

wherein said measuring device measures a number of steps by which said stepping motor is driven from said initial position of rotation; and

wherein said index detection hole is formed so as to be continually detected by said index sensor while the stepping motor is driven to rotate by a first predetermined number of steps in one direction, and further driven by a second predetermined number of steps in the same direction, and wherein one of said aperture position detection holes is detected by said aperture position sensor when driven by said second predetermined number of steps.

4. The endoscope light source unit according to claim 3 , wherein said controller drives the stepping motor step by step until the index censor detects said index detection hole in the case where none of said aperture position detection holes are detected by said aperture position sensor after said first and second predetermined numbers of steps of driving.

5. The endoscope light source unit according to claim 4 , wherein said index detection hole and said aperture position detection holes are formed at substantially same distances from the center of rotation of said rotary aperture disc; and

wherein said index detection hole is formed elongated in a circumferential direction of said rotary aperture disc so that said index detection hole continues to be detected by said index sensor while said stepping motor is rotated by a plurality of steps.

6. The endoscope light source unit according to claim 4 , wherein said index detection hole and said aperture position detection holes are formed at different distances from the center of rotation of said rotary aperture disc so that said index detection hole is detected only by said index sensor and said aperture position detection holes is detected by said aperture position sensor.

7. The endoscope light source unit according to claim 3 , further comprising a display device for displaying an error indication when none of said aperture position detection holes is detected by said aperture position sensor after said first and second predetermined numbers of steps of driving.