Glass for the production of optical elements with refractive index gradients

Claim 2

An optical quality glass composition suitable for the production of optical elements with a refractive index gradient delta n of at least 100×10 -4 by utilizing an ion exchange, consisting essentially of the following synthesis composition, in % by weight: ______________________________________ SiO.sub.2 56-78 MgO 6-15 Li.sub.2 O 5-14 Na.sub.2 O 3-14 K.sub.2 O 0- 9 ______________________________________ wherein the total of MgO plus Li 2 O is 12-23.

Claim 3

A glass composition according to claim 1, suitable for the production of a particularly high refractive index gradient delta n of at least 200×10 -4 , consisting essentially of the following composition, in % by weight: ______________________________________ SiO.sub.2 65-75 MgO 9-13 Li.sub.2 O 8-12 Na.sub.2 O 4-10 K.sub.2 O 0-8 ______________________________________ wherein the total of MgO plus Li 2 O is 16-22.

Claim 4

A glass composition according to claim 1, wherein up to 18% by weight of SiO 2 has been replaced by Al 2 O 3 .

Claim 5

A glass composition according to claim 2, wherein up to 18% by weight of SiO 2 has been replaced by Al 2 O 3 .

Claim 6

A glass composition according to any one of claim 1, 2, 3, or 4 which further contains a stabilizing amount of about 1-6% by weight of at least one of the following oxides is a stabilizing additive: ______________________________________ B.sub.2 O.sub.3 0-5 PbO 0-5 CaO 0-6 SrO 0-6 BaO 0-6 La.sub.2 O.sub.3 0-3 ZrO.sub.2 0-3 Ta.sub.2 O.sub.5 0-2 WO.sub.3 0-2 TiO.sub.2 0-2 ______________________________________

Claim 7

An optical glass having a refractive index gradient of at least 100×10 -4 produced by the ion exchange of a composition according to claim 1 with a molten inorganic sodium salt for a time and at a temperature sufficient to achieve said refractive index gradient.