PROBLEM TO BE SOLVED: To provide an endoscope lateral side illumination optical system not requiring a light guide which is bent, capable of enhancing operatability by shortening the length of a hard part of the front end part of an endoscope, uniforming light distribution, suppressing the parallax of an illumination field and a visual field even in near observation as much as possible, capable of illuminating in good transmission efficiency, and capable of downsizing as a whole.SOLUTION: The endoscope lateral side illumination optical system has a light source part 11 having an emission opening 11a1 directed to a front end side of an endoscope, a reflecting surface 12a reflecting illumination light emitted from the emission opening of the light source part to a lateral side, and a light transmission optical part 13 which is arranged in an outer periphery of a side view observation optical system 20, in which crosssection is formed in a general U-shape and an outer side surface 13a is formed in a cylindrical shape around a predetermined axis O along a longitudinal direction of the endoscope, and which guides the illumination light reflected by the reflecting surface to an object to be observed in the lateral side, the emission end 13c of the light transmission optical part is formed in an elongate shape along the longitudinal direction of the endoscope and is arranged in the lateral side of the observation window 21 of the lateral view observation optical system.COPYRIGHT: (C)2013,JPO&INPIT【課題】曲げ成形したライトガイドが不要で、内視鏡先端の硬質部の長さを短縮化して操作性を向上でき、配光を均一化し、近接観察においても照野と視野とのパララックスを極力抑え、伝送効率の良い照明ができ、しかも、全体にコンパクト化が可能な内視鏡側方照明光学系の提供。【解決手段】内視鏡の先端側を向く射出開口11a1を有する光源部11と、光源部の射出開口から射出した照明光を側方に反射する反射面12aと、側視観察光学系20の外周に配置され、断面が略U字状に形成されるとともに、外側面13aが内視鏡の長手方向に沿う所定軸Oを中心としたシリンドリカル形状に形成され、反射面で反射された照明光を側方の観察対象側に向けて導光する光伝送光学部13を有し、光伝送光学部の射出端13cが、内視鏡の長手方向に沿って細長形状に形成され、且つ、側視観察光学系の観察窓21の側方に配置されている。【選択図】図1
