PROBLEM TO BE SOLVED: To provide an illumination optical system for endoscopes capable of increasing an outgoing light quantity of illumination light by matching outgoing light intensity distribution of illumination light with an aspect ratio of a monitor and an observation range.SOLUTION: The illumination optical system for endoscopes provided in a flexible insertion tube includes: two light guides that are juxtaposed in the insertion tube in a first direction at both sides of a center of the insertion tube an observation window disposed on a distal surface of the insertion tube and concave lenses disposed at positions facing the end surfaces of the light guides, with the observation window sandwiched therebetween. The width in the first direction of the end faces of the light guides on the distal surface is smaller compared with the width in a second direction orthogonal to the first direction. A negative refractive power of the concave lenses in the first direction is larger than the negative refractive power in the second direction. Among the illumination light outgoing from the light guides and transmitting through the concave lenses, optical paths of illumination light passing through the centers of the light guides and outgoing from the end face centers of the light guides are inclined outward in the first direction, with the axial direction of the insertion tube used as the reference.COPYRIGHT: (C)2015,JPO&INPIT【課題】照明光の出射光強度分布がモニタのアスペクト比、および、観察範囲と整合し、照明光の出射光量を大きくする内視鏡用照明光学系を提供する。【解決手段】可撓性挿入管に設けられた内視鏡用照明光学系であって、挿入管内に、挿入管の中心を挟んで第1の方向に並んで配置された2つのライトガイドと、挿入管の先端面上に配置された観察窓と、ライトガイドの端面に対向する位置に、観察窓を挟むように配置された凹レンズ部と、を備え、先端面上における、ライトガイドの端面の第1の方向の幅が、第1の方向と直交する第2の方向の幅に比べて小さく、凹レンズ部の第1の方向の負の屈折力が、第2の方向の負の屈折力に比べて大きく、ライトガイドから出射して凹レンズ部を透過した照明光のうち、ライトガイドの中心を通ってライトガイドの端面中心から射出された照明光の光路が、挿入管の軸方向を基準として、第1の方向において外側に傾いている。【選択図】図2
