Optical glass
AssigneeHoya Glass Works, Ltd.
InventorsTetsuro Izumitani, Hiroji Sagara
Life of this patent
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Abstract
A thorium oxide-free B.sub.2 O.sub.3 --La.sub.2 O.sub.3 --Gd.sub.2 O.sub.3 --Ta.sub.2 O.sub.5 system optical glass is improved in stability to devitrification and in optical constants by introducing at least one of a divalent metal oxide such as ZnO, CdO, PbO, BaO, SrO, CaO, and MgO into the optical glass composition or replacing Ta.sub.2 O.sub.5 of the optical glass composition with a divalent metal oxide. If desired, the glass may be free of CdO.
Claims12
A thorium oxide-free glass having a liquidus temperature not greater than 1085.degree.C and having optical constants of 1.62-1.91 for n.sub.d and 59-27 for .nu.d consisting essentially of a composition in weight percent of 18 to 60% B.sub.2 O.sub.3, + SiO.sub.2, a quantity of B.sub.2 O.sub.3 being present and the content of said SiO.sub.2 being 0 to 23%, 0 to 50% La.sub.2 O.sub.3, 2to 50% Gd.sub.2 O.sub.3, 2 to 30% Ta.sub.2 O.sub.5, 0 to 50% ZnO, 0 to 53% CdO, 0 to 60% PbO, 0 to 50% BaO, 0 to 45% SrO, 0 to 30% CaO, 0 to 20% MgO, the sum of said ZnO + CdO + PbO + BaO + SrO + CaO + MgO being 2 to 60%, 0 to 16% Al.sub.2 O.sub.3, 0 to 9% ZrO.sub.2, 0 to 10% TiO.sub.2, 0 to 26% Nb.sub.2 O.sub.5, 0 to 15% WO.sub.3, and 0 to 18% Y.sub.2 O.sub.3.
A thorium oxide-free optical glass having optical constants of 1.77-1.85 for n.sub.d and 51-40 for .nu.d consisting essentially of a composition in weight percent of 0 to 8% SiO.sub.2, 21 to 30% B.sub.2 O.sub.3, 0 to 3% Al.sub.2 O.sub.3, 25 to 40% La.sub.2 O.sub.3, 2 to 25% Gd.sub.2 O.sub.3, 2 to 20% ZnO, the sum of said CdO + PbO + CaO + BaO + SrO + CaO + MgO being 0 to 10%, 0 to 6% ZrO.sub.2, 2 to 15% Ta.sub.2 O.sub.5, 0 to 12% Nb.sub.2 O.sub.5, 0 to 6% WO.sub.3, 0 to 3% TiO.sub.2 and 0 to 10 Y.sub.2 O.sub.3.
A thorium oxide-free optical glass having optical constants of 1.59-1.86 for n.sub.d and 62-19 for .nu. d consisting essentially of a composition, in weight percent, of 24 to 70% B.sub.2 O.sub.3 + SiO.sub.2, a quantity of B.sub.2 O.sub.3 being present and the content of said SiO.sub.2 being 0 to 25%, 1 to 50% La.sub.2 O.sub.3, 2 to 50% Gd.sub.2 O.sub.3, 0 to 56% ZnO, 0 to 61% CdO, 0 to 66% PbO, 0 to 50% BaO, 0 to 40% SrO, 0 to 25% CaO, 0 to 20% MgO, the sum of said ZnO + CdO + PbO + BaO + SrO + CaO + MgO being 2 to 66%, 0 to 20% Al.sub.2 O.sub.3, 0 to 10% ZrO.sub.2, 0 to 10% TiO.sub.2, 0 to 15% Nb.sub.2 O.sub.5, 0 to 10% WO.sub.3, and 0 to 20% Y.sub.2 O.sub.3.
Dependencies are inferred from the claim text.