tempestglen

http://www2.avs.org/historybook/links/tfexh96.htm SINGLE LAYERS 1935 Zeiss (Smakula), German Patent No.605761 claimed on 1/11/1935 vapor deposition of CaF2; 1936 Strong CaF2 and formula nfilm=nsubstrate0.5 specified. Article submitted 25/9/1935: The reflection will be reduced using this layer from 4.2% to 0.6%; 1938 Cartwright and Turner published a whole class of usable materials including MgF2 and Cryolite; The vapor deposition of MgF2 on hot glass surfaces is still state-of-the-art today. This procedure was unknown in Germany during the last war. Therefore they primarily used Cryolite which lowers the reflection, but is not as hard. DOUBLE LAYERS For a single layer, one only has a few choices of materials. With a double layer, there are more choices using high and low reflective indexes. The three reflections at the three interfaces can always add to zero by varying film thicknesses. This is true for at least one wavelength. The milestone developments were: 1938 Research Corporation, New York announced without mentioning any inventor, the principal of solving the three vector calculations and mentioned materials that can be used (Swiss Patent No.221992, issued June 30, 1942); 1939 Cartwright and Turner - a short publication, describing the principle of using Al2O3/SiO2, which was not practical; 1940- 1941 Zeiss (Smakula) and Schott (Geffcken) and Steinkeil (Schneider) experimented with double and triple layers; double layers never got into production in Germany or the U.S.; 1949 Balzers (Auwaerter) introduced the double layer "Transmar" (MgF2 plus rare earth oxide) and for many years had a leading position with this method. Further developments are well known. Today large volumes of anti-reflection coatings up to six layers are produced. Not only optical instruments but consumer goods like binoculars and cameras use anti-reflection coatings (modern camera lenses have the label “Imulti-coated”). The biggest use (in dollar value) of thin films from 1950 to 1970 was certainly anti-reflection coatings.

Completely Nonesense. In WWII, German used MGF2, and allied used CaF2 to reduce reflection, both were single coating, AFTER WWII,a Swiss company developed PRACTICAL multi-coating lense. Do you know the famous US film <<Gone with the wind>> in 1939? They were coating anti-reflection films for ‘Gone With the Wind,’ for their projection lenses.