Patent ID: 7553785

Claim:
A lead-free and arsenic-free optical glass with a refractive index n d of 1.86≦n d ≦1.95 and an Abbe number ν d of 19≦ν d ≦24, wherein said optical glass is free of lead, free of arsenic, free of Na 2 O, free of B 2 O 3 , and has a glass composition (based on oxide content in % by weight) comprising: P 2 O 5 18-25 Nb 2 O 5 30-40 Bi 2 O 3 6-18 WO 3 12-17 GeO 2 2-7 Li 2 O 0.7-4 K 2 O 0.5-4 Cs 2 O 1-6 MgO 0-4 CaO 0-4 SrO 0-4 BaO 0-6 ZnO 0-4 TiO 2 0-1.5 Σ Alkali oxides 3-9 Σ Alkaline-earth oxides 0.5-6 Σ Nb 2 O 5 , WO 3 , Bi 2 O 3 ≧57 a fining agent 0-2.