ANTIREFLECTIVE MULTILAYER COATING ON A HIGHLY REFRACTIVE SUBSTRATE

• US 3,829,197 A
• Filed: 10/18/1972
• Issued: 08/13/1974
• Est. Priority Date: 10/20/1971
• Status: Expired due to Term

• Current Assignee: Alfred Thelen
• Original Assignee: Alfred Thelen
• Inventors: Thelen, Alfred
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Church, C. E.
• Application Number:
  US05/298,548
• Time in Patent Office: 664 Days
• Field of Search: 350/164,165,166
• US Class Current: 359/588
• CPC Class Codes: C03C 17/3417 all coatings being oxide coatings
• CPC Class Codes: C03C 17/3452 comprising a fluoride
• CPC Class Codes: G02B 1/115 Multilayers

Abstract

An antireflective multilayer coating for highly refractive glass material comprises five partial layers adjusted to one another as for their reflective indices and their optical thicknesses so as to obtain a vary favorable antireflection curve with a broad flat middle portion in the order of the desired, so-called reference wavelength. To this effect, the refraction index of the individual layers is provided, for the first and third layer, by 15 percent lower and, for the second and fourth layer, by 10 to 30 percent higher than the refractive index of the substrate and for the outer fifth layer lower than 1.5, and the optical thicknesses are provided, for the first and fifth layer onefourth, for the second layer one-eightieth to one-sixteenth, for the third layer one-eighth to one-fifth, and for the fourth layer one-half of the reference wavelength. The value of the refractive index of the fifth layer preferably approaches to the square root of the refractive index of the substrate.

Claims

2. An antireflection multilayer coating according to claim 1, wherein said fifth partial layer has a refractive index corresponding approximately to the square root of the refractive index of said substrate.