PROBLEM TO BE SOLVED: To provide a rigid endoscope system capable of acquiring high-resolution observation images while suppressing an outer diameter of a tubular body.SOLUTION: A rigid endoscope system 100 includes: a linear tubular body 110； an objective lens 151 provided at one end side of the tubular body 110； an eye-piece 152 provided at the other end side in an opposite side of the one end side of the tubular body； an imaging lens 153 provided at the other end side of the tubular body 110 further than the eye-piece lens 152； an image pickup device 121 for photoeletrically converting an image to be formed by the imaging lens 153； a lighting element 141 for projecting illumination light； and a splitting optical element 131 provided between the imaging lens 153 and the image pickup device 121, guiding at least partial light flux exited from the imaging lens 153 to the image pickup device side, and guiding at least partial illumination light exited from the lighting element 141 to the image pickup device side. A diameter of an entrance pupil of an optical system including the objective lens 151, the eyepiece 152, and the imaging lens 153 is 60% or more of the outside diameter of the tubular body 110.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2018,JPO&INPIT【課題】管体の外径を抑制しつつ高解像の観察像を取得できる硬性内視鏡システムを提供する。【解決手段】直線状の管体１１０と、管体１１０の一端側に設けられた対物レンズ１５１と、管体の一端側とは反対の他端側に設けられた接眼レンズ１５２と、管体１１０の、接眼レンズ１５２より更に他端側に設けられた結像レンズ１５３と、結像レンズ１５３によって結像される像を光電変換する撮像素子１２１と、照明光を投射する照明素子１４１と、結像レンズ１５３と撮像素子１２１の間に設けられ、結像レンズ１５３から出射される少なくとも一部の光束を撮像素子側へ導くと共に、照明素子１４１から出射される少なくとも一部の照明光を結像レンズ側へ導く分割光学素子１３１とを備え、対物レンズ１５１、接眼レンズ１５２および結像レンズ１５３を含む光学系の入射瞳径が、管体１１０の外径の６０％以上である硬性内視鏡システム１００。【選択図】図１
