Light source apparatus for electronic endoscope and electronic endoscope having the light source apparatus

1. A light source apparatus for an electronic endoscope comprising:

a light source;

a rotary shutter, having a rotation axis, which includes a pair of coaxial aperture controlling rotary plates, wherein an amount of light emitted from said light source toward a light guide is controlled by varying a relative rotation angle of said pair of aperture controlling rotary plates;

a first planetary gear mechanism including a first internal tooth gear, which is a fixed gear and is coaxial with said rotation axis of said rotary shutter, a first sun gear which is rotated together with one of said pair of aperture controlling rotary plates via a motor and is coaxial with an axis of said first internal tooth gear, and at least one first planet gear which is simultaneously engaged with said first internal tooth gear and said first sun gear;

a second planetary gear mechanism including a second internal tooth gear identical to said first internal tooth gear and coaxial with said rotation axis of said rotary shutter, a second sun gear which rotates together with the other of said pair of aperture controlling rotary plates and is identical to said first sun gear and coaxial with an axis of said second internal tooth gear, and at least one second planet gear, identical to said first planet gear, which is simultaneously engaged with said second internal tooth gear and said second sun gear; and

a carrier device which is rotatable about an axis coincident with said rotation axis of said rotary shutter, wherein said carrier device holds said first and second planet gears in a same phase position with respect to said first and second internal tooth gears, and supports said first and second planet gears to allow said first and second planet gears to rotate relative to each other,

wherein an endless timing belt, formed from a resilient material, is installed on an output gear which is fixed to a drive shaft of a phase-difference motor which is provided separate from said motor and an input tooth portion formed on an outer peripheral surface of said second internal tooth gear, and

wherein said timing belt includes a meshing portion formed on an inner peripheral surface thereof, said meshing portion being engaged with said input tooth portion of said second internal tooth gear and said output gear.

2. An electronic endoscope having said light source apparatus according to claim 1 , further comprising:

an operating portion; and

an insertion portion extending from said operating portion and inserted into an object to be viewed,

wherein said light guide is inserted in said operating portion and said insertion portion so that a distal end of said light guide extends to a distal end of said insertion portion, and

wherein said light source emits illuminating light to said light guide.

3. A light source apparatus for an electronic endoscope comprising:

a light source;

a rotary shutter, having a rotation axis, which includes a pair of coaxial aperture controlling rotary plates, wherein an amount of light emitted from said light source toward a light guide is controlled by varying a relative rotation angle of said pair of aperture controlling rotary plates;

a first planetary gear mechanism including a first internal tooth gear, which is coaxial with said rotation axis of said rotary shutter, a first sun gear which is driven to rotate together with one of said pair of aperture controlling rotary plates via a motor and is coaxial with an axis of said first internal tooth gear, and at least one first planet gear which is simultaneously engaged with said first internal tooth gear and said first sun gear;

a second planetary gear mechanism including a second internal tooth gear, which is a fixed gear, identical to said first internal tooth gear and coaxial with said rotation axis of said rotary shutter, a second sun gear which rotates together with the other of said pair of aperture controlling rotary plates and is identical to said first sun gear and coaxial with an axis of said second internal tooth gear, and at least one second planet gear, identical to said first planet gear, which is simultaneously engaged with said second internal tooth gear and said second sun gear; and

a carrier device which is rotatable about an axis coincident with said rotation axis of said rotary shutter, wherein said carrier device holds said first and second planet gears in a same phase position with respect to said first and second internal tooth gears, and supports said first and second planet gears to allow said first and second planet gears to rotate relative to each other,

wherein an endless timing belt, formed from a resilient material, is installed on an output gear which is fixed to a drive shaft of a phase-difference motor which is provided separate from said motor and an input tooth portion formed on an outer peripheral surface of said first internal tooth gear, and

wherein said timing belt includes a meshing portion formed on an inner peripheral surface thereof, said meshing portion being engaged with said input tooth portion of said second internal tooth gear and said output gear.

4. The light source apparatus according to claim 3 , wherein said first internal tooth gear is rotatably supported by a gear bearing.

5. An electronic endoscope having said light source apparatus according to claim 3 , further comprising:

an operating portion; and

an insertion portion extending from said operating portion and inserted into an object to be viewed,

wherein said light guide is inserted in said operating portion and said insertion portion so that a distal end of said light guide extends to a distal end of said insertion portion, and

wherein said light source emits illuminating light to said light guide.