Patent ID: 8575048

Claim:
An optical glass comprising, by cationic %, 20 to 50% of B 3+ , 0 to 10% of Si 4+ , 5 to 35% of La 3+ , 0 to 10% of Gd 3+ , 0 to 10% of Y 3+ , 0 to 10% of Yb 3+ , 0 to 4% of Ti 4+ , 1 to 30% of Nb 5+ , 0.5 to 15% of Ta 5+ , 0 to 5% of W 6+ , 0 to 10% of Zr 4+ , 11 to 40% of Zn 2+ , 0 to 10% of Mg 2+ , 0 to 10% of Ca 2+ , 0 to 10% of Sr 2+ , 0 to 10% of Ba 2+ , 0 to 10% of Li + , 0 to 10% of Na + , 0 to 10% of K + , 0 to 10% of Te 4+ , 0 to 10% of Ge 4+ , 0 to 10% of Bi 3+ , and 0 to 10% of Al 3+ , the total content of B 3+ and Si 4+ (B 3+ +Si 4+ ) being 20 to 50%, the total content of La 3+ , Gd 3+ and Y 3+ (La 3+ +Gd 3+ +Y 3+ ) being 5 to 35%, the cationic ratio of ((B 3+ +Si 4+ )/(La 3+ +Gd 3+ +Y 3+ )) being from 1 to 5, the total content of Ti 4+ , Nb 5+ , Ta 5+ and W 6+ (Ti 4+ +Nb 5+ +Ta 5+ +W 6+ ) being 10 to 35%, the cationic ratio of ((Nb 5+ +Ta 5+ )/(Ti 4+ +Nb 5+ +Ta 5+ +W 6+ )) being from 0.7 to 1, the cationic ratio of ((B 3+ +Si 4+ )/(Ti 4+ +Nb 5+ +Ta 5+ +W 6+ )) being from 0.5 to 4, the cationic ratio of ((La 3+ +Gd 3+ +Y 3+ )/(Ti 4+ +Nb 5+ +Ta 5+ +W 6+ )) being from 0.2 to 3, the cationic ratio of the content of Zn 2+ to the total content of Zn 2+ , Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ (Zn 2+ /(Zn 2+ +Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ ) being from 0.8 to 1, the optical glass having a refractive index nd of 1.89 or more and an Abbe's number νd of 27 to 37.