| 摘要 |
PROBLEM TO BE SOLVED: To provide an insertion portion of an endoscope which lessens breakage of an optical fiber bundle for illumination in spite of long-term use and can maintain good observation performance. SOLUTION: The insertion portion of the endoscope constituted by inserting and arranging the plural built-in objects, such as the optical fiber bundle 13 for illumination and tubes 12 into a flexible pipe 1 formed with a bending section 2 to be bent by remote control in its distal end segment is so constituted that (Σs/S) when the cross-sectional area of the internal space of one flexible pipe in denoted as S and the total of the cross-sectional area of the plural built-in objects is defined asΣs, exists within a range of 0.5<=(Σs/S)<=0.6 if the inner diameter of the flexible pipe 1 is >=6.5 mm and exists in a range of 0.5<=(Σs/S)<=0.65 if the inner diameter of the flexible pipe 1 is blow 6.5 mm.
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