Band filters for use in protective glasses
First Claim
1. A band filter adapted to allow passage only of a band length between 350 and 750 nm, said filter consisting essentially of a support which is at least partially transparent in the considered band, a filter element coated on at least one of the two faces of said support, said filter element consisting of three metallic layers respectively separated by two layers of transparent material, said layers of transparent material having an index of refraction greater than 1.5, the optical thickness of the layers of transparent material each being equal to about 1/4 of the mean wave length of the considered band, one of said metallic layers of said filter elements having a surface within about 15 nm of said support, and an anti-reflection coating on the outer surface of said filter element opposite said support, said anti-reflection coating consisting of a layer of a metallic or semi-metallic element on the other of said outer metal layers of said outer surface and a layer of transparent material disposed on said layer of metallic or semi-metallic element.
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Abstract
A band filter adapted to pass only a band of determined wave length of the electromagnetic spectrum and comprising a support, at least partially transparent in the considered band, covered on one of its surfaces by a filtering element constituted of three metallic layers separated respectively by two layers of transparent material. The filter can employ anti-reflection coatings and binding and adherency layers.
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Citations
12 Claims
- 1. A band filter adapted to allow passage only of a band length between 350 and 750 nm, said filter consisting essentially of a support which is at least partially transparent in the considered band, a filter element coated on at least one of the two faces of said support, said filter element consisting of three metallic layers respectively separated by two layers of transparent material, said layers of transparent material having an index of refraction greater than 1.5, the optical thickness of the layers of transparent material each being equal to about 1/4 of the mean wave length of the considered band, one of said metallic layers of said filter elements having a surface within about 15 nm of said support, and an anti-reflection coating on the outer surface of said filter element opposite said support, said anti-reflection coating consisting of a layer of a metallic or semi-metallic element on the other of said outer metal layers of said outer surface and a layer of transparent material disposed on said layer of metallic or semi-metallic element.
Specification