INFRA-RED INTERFERENCE FILTER

• US 3,682,528 A
• Filed: 09/10/1970
• Issued: 08/08/1972
• Est. Priority Date: 09/10/1970
• Status: Expired due to Term

• Current Assignee: Joseph H. Apfel, Robert M. Gelber
• Original Assignee: Joseph H. Apfel, Robert M. Gelber
• Inventors: Apfel, Joseph H., Gelber, Robert M.
• Primary Examiner(s): Schonberg, David
• Assistant Examiner(s): Kusmer, Toby H.
• Application Number:
  US05/071,009
• Time in Patent Office: 698 Days
• Field of Search: 350/1,163-166 117/33.3
• US Class Current: 359/360
• CPC Class Codes: G02B 5/282 reflecting for infrared and transparent for visible light, e.g. heat reflectors, laser protection

Abstract

Infra-red reflecting interference filter having a substrate capable of transmitting visible energy and having a surface with a precoat layer adherent thereto formed of a thin layer of material and a layer of silver deposited on the thin layer and having a thickness so that it is highly transmitting of visible energy and highly reflecting of infra-red energy.

Claims

1. In a filter, a substrate having a surface, said substrate being formed of a material capable of transmitting visible energy and a coating formed on said surface, said coating comprising first and second bi-layers, with each of the said bi-layers consisting of a layer of silver having a thickness ranging from 55 to 130 angstroms and a precoat layer having a thickness which is in excess of a minimum value of approximately 5 Angstroms and has a maximum thickness which is ineffective in changing the optical properties of the filter but causing the silver layer to behave as a homogenous metal slab, said coating having a transmission which is over approximately 70 percent in the region from 400 to 700 mm and below approximately 10 percent in the region of 700 to 2500 mm and a reflection which is approximately 10 percent average from 400 to 700 mm and increases to over 90 percent in the range of 700 to 2500 mm.

5. A filter as in claim 1 wherein said coating includes at least one layer of dielectrical material overlying said surface.

6. A filter as in claim 1 wherein said coating includes an additional dielectric layer overlying each bi-layer.

7. A filter as in claim 1 which has a neutral appearance in both directions.

2. A filter as in claim 19 wherein each of said precoat layers has a thickness ranging from 5 to 20 angstroms.

3. A filter as in claim 2 wherein each of said precoat layers is formed of a metal.

4. A filter as in claim 3 wherein each of said precoat layers is formed of nickel.