PROBLEM TO BE SOLVED: To provide an illumination optical system for an endoscope that prevents color unevenness in a subject from occurring even if there exists an object blocking a light ray in the neighborhood of an illumination light emission port by eliminating color unevenness of an excitation light color and a fluorescent color at the illumination light emission port.MEANS FOR SOLVING THE PROBLEM: An illumination optical system for an endoscope includes: a positive lens for converting a laser beam emitted from a laser diode light source to a collimated laser beam a fluorescent body disposed at the tip of an endoscope body, which emits a fluorescent light when irradiated with the collimated laser beam and a negative lens disposed near the position of the fluorescent body in an optical path between the positive lens and the fluorescent body. A light in which a laser beam that transmits the fluorescent body and a fluorescent light are mixed is used as an illumination light for the endoscope. The illumination optical system for an endoscope satisfies the following conditional expressions (1) and (2): (1) 0.07×D≤FP≤0.4×D, and (2) -3≤FP/FN≤-0.5.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2019,JPO&INPIT【課題】照明光出射口での励起光色と蛍光色の色ムラを無くすことで、照明光出射口近傍に光線をさえぎる物体が存在しても被写体での色ムラを発生させない内視鏡用照明光学系を提供すること。【課題手段】レーザーダイオード光源から出射するレーザー光をコリメートされたレーザー光に変換する正レンズと、内視鏡本体の先端に配置され、コリメートされたレーザーが照射されることで蛍光を発する蛍光体と、正レンズと蛍光体との間の光路内であって、蛍光体の位置近傍に配置された負レンズと、を有し、蛍光体を透過するレーザー光と、蛍光と、が混在した光を内視鏡の照明光として使用する内視鏡用照明光学系において、以下の条件式(1)、(2)を満足する。 0.07×D≦FP≦0.4×D (1) -3≦FP/FN≦-0.5 (2)【選択図】図1
