Patent ID: 8329602

Claim:
An optical glass for a light guide, an image guide or a glass lens for an exposure device for semiconductors comprising each of SiO 2 , B 2 O 3 , BaO, and Ta 2 O 5 , La 2 O 3 in an amount of 0-2 mass % and Nb 2 O 5 in an amount of 0-0.01 mass %, wherein the optical glass is free of a lead compound, an arsenic compound, BaCl 2 , Nd 2 O 3 , Sm 2 O 3 , As 2 O 3 , CeO 2 , Fe 2 O 3 and Pr 2 O 3 , the optical glass having the ratio of Ta 2 O 5 /(Ta 2 O 5 +(ZrO 2 +TiO 2 +Nb 2 O 5 +WO 3 )×5) being 0.95<Ta 2 O 5 /(Ta 2 O 5 +(ZrO 2 +TiO 2 +Nb 2 O 5 +WO 3 )×5)≦1.00) and having internal transmittance of 0.9900 or over at a wavelength within a range from 400 nm to 450 nm and internal transmittance of 0.9980 or over at a wavelength within a range from 600 nm to 700 nm as measured respectively in accordance with the Japan Optical Glass Industry Standard JOGIS17 -1982 “Measuring Method of Internal Transmittance of Optical Glass” by using two samples having thicknesses of 10 mm and 40 mm, and having a refractive index of 1.55 or over, wherein the optical glass is a core material of an optical fiber.