| 摘要 |
An illumination optical system for endoscopes, which is used by combining the llumination optical system with an objective optical system, where the objective optical system can observe a predetermined area at least ranging from the lateral direction to the backward direction with respect to the longitudinal direction of an endoscope and across the range of 180 degrees or more in the circumferential direction of the endoscope, and which is provided with an illumination optical system capable of radiating light to the predetermined area which can be observed by the objective optical system, is formed in such a way that illumination light becomes central darkening along the longitudinal direction of the endoscope and across the range of 180 degrees in the circumferential direction of the endoscope which can be observed by the objective optical system and that the illumination optical system has a luminous intensity distribution characteristic in which the central-darkening illumination light is radiated to the vicinity of the lateral direction with respect to the longitudinal direction of the endoscope.
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