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US 4,303,298 AGranted
Near infrared absorption filter for color television cameras
AssigneeHoya Corporation
InventorToshiharu Yamashita
Life of this patent
Estimating the term…
Abstract
A near infrared absorption filter for color television cameras, comprising (a) a base glass comprising, in % by weight based on the weight of the base glass, 50-78% P.sub.2 O.sub.5, 10-50% BaO, 0-7% Al.sub.2 O.sub.3, 0-6% B.sub.2 O.sub.3, 0-5% SiO.sub.2, 0-8% Li.sub.2 O, 0-15% Na.sub.2 O, 0-18% K.sub.2 O, 0-5% MgO, 0-10% CaO, 0-15% SrO, 0-10% ZnO, and 0-10% PbO, and (b) about 0.5 to about 2.5% by weight of CuO based on the weight of the base glass.
Claims6
A near infrared absorption filter for color television cameras, comprising
- (a) a base glass consisting essentially of, in % by weight, 50-75% P.sub.2 O.sub.5, 10-50% BaO, 0-7% Al.sub.2 O.sub.3, 0-6% B.sub.2 O.sub.3, 0-5% SiO.sub.2, 0-8% Li.sub.2 O, 0-15% Na.sub.2 O, 0-18% K.sub.2 O, 0-5% MgO, 0-10% CaO, 0-15% SrO, 0-10% ZnO, and 0-10% PbO, and
- (b) about 0.5 to about 2.5% by weight of CuO based on the weight of the base glass,
- (c) and wherein the total amount of said BaO and at least one of said Li.sub.2 O, Na.sub.2 O and K.sub.2 O is 25-45% by weight.
A near infrared absorption filter for color television cameras, comprising
- (a) a base glass consisting essentially of, in % by weight, 50-75% P.sub.2 O.sub.5, 10-50% BaO, 0-7% Al.sub.2 O.sub.3, 0-6% B.sub.2 O.sub.3, 0-5% SiO.sub.2, 0-8% Li.sub.2 O, 0-15% Na.sub.2 O, 0-18% K.sub.2 O, 0.5% MgO, 0-10% CaO, 0-15% SrO, 0-10% ZnO, and 0-10% PbO, and
- (b) about 0.5 to about 2.5% by weight of CuO based on the weight of the base glass, said glass having a transmission at 600 nm of 75% or more when the transmission at 700 nm is 15%,
- (c) and wherein the total amount of said BaO and at least one of said Li.sub.2 O, Na.sub.2 O and K.sub.2 O is 25-45% by weight.
Dependencies are inferred from the claim text.