Three layer anti-reflection coating

• US 3,185,020 A
• Filed: 09/07/1961
• Issued: 05/25/1965
• Est. Priority Date: 09/07/1961
• Status: Expired due to Term

• Current Assignee: Alfred J. Thelen
• Original Assignee: Alfred J. Thelen
• Inventors: Thelen, Alfred J.
• Application Number:
  US04/136,479
• Time in Patent Office: 1,356 Days
• US Class Current: 359/586
• CPC Class Codes: G02B 1/115 Multilayers

Claims

1. IN THE COMBINATION OF A BODY HAVING A NORMAL LIGHT REFLECTING SURFACE AND AN INDEX OF REFRACTION FROM 1.45 TO 1.58 AND A NON-ABSORBING SUBSTANTIALLY COLORLESS MULTIPLE LAYER ANTI-REFLECTION COATING DISPOSED ON SAID SURFACE, THE ANTI-REFLECTION COATING COMPRISING A TRANSPARENT FIRST LAYER HAVING AN OPTICAL THICKNESS OF ONE-QUARTER OF THE DESIGN WAVELENGTH OF ANTI-REFLECTION COATING AND HAVING AN INDEX OF REFRACTION OF APPROXIMATELY 1.38, SAID FIRST LAYER BEING FORMED OF MAGNESIUM FLUORIDE, A TRANSPARENT SECOND LAYER HAVING AN OPTICAL THICKNESS OF ONE-HALF OF THE DESIGN WAVELENGTH OF THE ANTI-REFLECTION COATING AND HAVING AN INDEX OF REFRACTION RANGING FROM 1.9 TO 2.3, SAID SECOND LAYER BEING FORMED OF ZIRCONIUM OXIDE, AND A TRANSPARENT THIRD LAYER HAVING AN OPTICAL THICKNESS OF ONE-QUARTER OF THE DESIGN WAVELENGTH OF THE ANTI-REFLECTION COATING AND HAVING AN INDEX OF REFRACTION FROM 1.8 TO 1.85, SAID THIRD LAYER BEING FORMED OF CERIUM FLUORIDE, SAID THIRD LAYER ALSO BEING FORMED OF A MATERIAL HAVING AN INDEX OF REFRACTION N3 WHICH IS DETERMINED FROM THE EQUATION N1(**2)= N3(**2)/NS WHERE N1 IS THE INDEX OF REFRACTION OF THE MATERIAL FORMING THE FIRST LAYER AND NB IS THE INDEX OF REFRACTION OF THE MATERIAL FORMING THE BODY.