| 摘要 |
PROBLEM TO BE SOLVED: To provide a structure for holding a lens constituting an optical system for illumination, which reduces light quantity loss caused by scattering in the outer peripheral part of the lens. SOLUTION: A housing 14 is attached to the front end of a flexible tube 12 of an endoscope to be inserted into a body, and a plano-concave lens 18 constituting the optical system for illumination is built in a lens-holding recessed part 30 of the housing 14. A light reflecting surface 36 is formed in an inner peripheral surface 3004 of the lens-holding recessed part 30. Spaces between a rear face 1804 of the plano-concave lens 18 and a bottom face 3002 of the lens-holding recessed part 30 and between an outer peripheral surface 1808 of the plano-concave lens 18 and the light reflecting surface 36 are filled up with an adhesive 34, and the plano-concave lens 18 is fixed in the lens holding recessed part 30 by this adhesive 34. The adhesive 34 has a light transmission property. The adhesive 34 has a refractive index which is close to that of the plano-concave lens 18 to such a degree that light cannot be scattered greatly on the boundary between the plano-concave lens 18 and the adhesive 34.
|
