Patent ID: 7605099

Claim:
An optical element for an optical data transfer device said optical element comprising an optical glass with an index of refraction (n d ) greater than or equal to 1.70, an Abbé number (ν d ) greater than or equal to 35 and a density (ρ) that is less than or equal to 4.5 g/cm 3 , wherein said optical glass is a lanthanate borate glass with a composition, in percent by might based on oxide content which consists of: La 2 O 3 30 to 45 B 2 O 3 30 to 40 Al 2 O 3 0 to 5 PbO 0.1 to 5 Li 2 O 0 to 10 Na 2 O 0 to 10 K 2 O 0 to 10 Rb 2 O 0 to 10 Cs 2 O 0 to 10 MgO 0 to 8 CaO 0 to 8 SrO 0 to 8 BaO 0 to 8 ZnO 1 to 10 TiO 2 0 to 5 ZrO 2 1 to 10 Y 2 O 3 1 to 8 Yb 2 O 3 0.1 to 2 Gd 2 O 3 0.1 to 5 Nb 2 O 5 0.1 to 10 with MgO + CaO + SrO + BaO 0 to 10 with Li 2 O + Na 2 O + K 2 O + Rb 2 O + Cs 2 O 0 to 10; and from 0 to 1.5 percent by weight of at least one refining agent, wherein said at least one refining agent is selected from the group consisting of SO 4 −2 , Cl − , Sb 2 O 3 , As 2 O 3 , SnO 2 and CeO 2 .