Patent ID: 8579803

Claim:
An endoscope comprising: an insertion portion including an image pickup section and an illumination section in a distal end portion thereof; and a light guide inserted through an inside of the insertion portion, the light guide including a plurality of fibers made of a glass not containing lead, the plurality of fibers guiding illuminating light from a light source apparatus connected to a proximal end portion side to the illumination section, the light guide having a numerical aperture (NA) of 0.46 to 0.90, wherein a core glass of the fibers has a refractive index nd of 1.56 to 1.74, and has a composition of (A) 20 to 55 wt % SiO 2 , (B1) exceeding 2.0 wt % to equal to or less than 4.0 wt % B 2 O 3 , (B2) neither P 2 O 5 nor GeO 2 contained, (C) 25 to 72 wt % (BaO+SrO+La 2 O 3 +Lu 2 O 3 +Ta 2 O 5 +Gd 2 O 3 +WO 3 ), (D) 0 to 30 wt % ZnO, (E) no Al 2 O 3 contained, (F) no ZrO 2 contained, (G) neither PbO nor As 2 O 3 contained, (H) 0 to 15 wt % (Na 2 O+K 2 O), (I) 0 to 0.050 wt % Sb 2 O 3 and (J) 0.26 to 1.63 wt % (Na 2 SO 4 +K 2 SO 4 ).