| 摘要 |
PROBLEM TO BE SOLVED: To facilitate the guidance of a treating implement with simple constitution and to enable the intensification of the visible contrast of an observation image. SOLUTION: The endoscope which has an observation optical system having an observation window 2 at the front end of an endoscope insertion part 1 and an illumination optical system having an illumination window 3 at the front end of the endoscope insertion part 1 satisfies (1) L/De>=0.4 and (2) Si/Se<=0.09, where L: the distance between the center of the observation window 2 and the center of the illumination window 3, De: the outside diameter at the front end 1 of the endoscope insertion part, Si: the cross-sectional area of the illumination window 3 and Se: the cross-sectional area at the front end 1 of the endoscope insertion part.
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