PROBLEM TO BE SOLVED: To provide an endoscope system capable of acquiring and observing an oxygen saturation related to a surface blood vessel with excellent measurement accuracy, in such a form that a configuration of an existing light source device can be easily utilized.SOLUTION: The light source device of the endoscope system includes a white light source 30 for emitting white light utilized for illumination light for obtaining normal observation images, and a semiconductor light source unit 31. The semiconductor light source unit 31 emits oxygen saturation measurement light which has a narrow wavelength band in a part of a blue region and is used for measuring the oxygen saturation of blood hemoglobin in a blood vessel present at an observation site, by irradiating the observation site with the light. In addition to the oxygen saturation measurement light, the light source device supplies, to an electronic endoscope, light of a red region included in the white light as blood amount measurement light for measuring the blood amount of the blood vessel. On the basis of first and second imaging signals outputted by an imaging device according to the oxygen saturation measurement light and the blood amount measurement light, the blood amount and the oxygen saturation are calculated. The information of the oxygen saturation from which the influence of the blood amount is eliminated is turned to an image.【課題】表層血管に関する酸素飽和度について良好な測定精度で取得して観察可能な内視鏡システムを、既存の光源装置の構成を利用しやすい形態で提供する。【解決手段】内視鏡システムの光源装置は、通常観察画像を得るための照明光に利用される白色光を発する白色光源３０と、半導体光源ユニット３１とを有する。半導体光源ユニット３１は、青色領域の一部の狭い波長域を有し、観察部位に照射して観察部位に存在する血管の血中ヘモグロビンの酸素飽和度を測定するための酸素飽和度測定光を発する。光源装置は、酸素飽和度測定光に加えて、血管の血液量を測定するための血液量測定光として、白色光に含まれる赤色領域の光を電子内視鏡に供給する。酸素飽和度測定光及び血液量測定光に応じて撮像素子が出力する第１及び第２の撮像信号に基づいて、血液量及び酸素飽和度が算出される。血液量の影響を除去した酸素飽和度の情報が画像化される。【選択図】図８
