Patent ID: 7250383

Claim:
A glass rod for a graded-index rod lens, wherein a graded-index lens preform glass A is covered by and provided in a single unit with a clad glass composition B; (1) wherein the glass composition of the graded-index lens preform glass A expressed in mol % includes SiO 2 : 45 to 65, Li 2 O: 3 to 20, Na 2 O: 3 to 15, K 2 O: 0 to 10, MgO: 0 to 15, BaO: 0 to 20, TiO 2 : 0 to 10, ZnO: 0 to 10, La 2 O 3 : 0 to 7, B 2 O 3 : 0 to 15, wherein Li 2 O+Na 2 O+K 2 O: 6 to 35; (2) wherein the clad glass composition B substantially does not include PbO and substantially does not include TiO 2 , and expressed in mol % includes SiO 2 : 45 to 65, Na 2 O: 3 to 30, K 2 O: 0 to 10, MgO: 0 to 15, BaO: 0 to 20, wherein Na 2 O+K 2 O: 3 to 35 and MgO+BaO: 0 to 25; and furthermore includes B 2 O 3 : 0 to 15, ZnO: 0 to 10, Y 2 O 3 : 0 to 7, ZrO 2 : 0 to 7, Nb 2 O 5 : 0 to 7, In 2 O 3 : 0 to 7, La 2 O 3 : 0 to 7, and Ta 2 O 5 : 0 to 10, wherein B 2 O 3 +ZnO+Y 2 O 3 +ZrO 2 +Nb 2 O 5 +In 2 O 3 ;+La 2 O 3 +Ta 2 O 5 : 0 to 20.