Patent ID: 8859444

Claim:
An optical glass comprising, by mass %, 1 to 30% of B 2 O 3 , 5.86 to 20% of SiO 2 , 55 to 75% of a total of La 2 O 3 , Gd 2 O 3 , Y 2 O 3 and Yb 2 O 3 , the content of La 2 O 3 being 15 to 55%, the mass ratio of the content of Gd 2 O 3 to the total content of La 2 O 3 , Gd 2 O 3 , Y 2 O 3 and Yb 2 O 3 , (Gd 2 O 3 /La 2 O 3 +Gd 2 O 3 +Y 2 O 3 +Yb 2 O 3 ), being 0.25 to 0.65, 0 to 13% of Ta 2 O 5 (exclusive of 13%), 0 to 25% of a total of Nb 2 O 5 , TiO 2 , WO 3 and ZrO 2 , the content of Nb 2 O 5 being less than 10%, and 0 to 5% WO 3 and having a glass transition temperature of 650° C. or higher, a refractive index nd of 1.875 to 1.92 and an Abbe's number νd of 36 to 45.