At 12:31 PM 1/16/2009, Richard Knoppow wrote: > I am not sure what method Kodak used for coating. It >may have been a chemical bath coating or an early form of >vacuum coating. Chemical bath methods were known and some >experimental work was done at Radio Corporation of America >and reported in the RCA house journal. > I can't find Smakula's patent. Marc has more history >about this but I think the work may have been kept secet by >the German government and no patent published. My patent >search uses Google patents and searches only US patents. Its >quite possible Kodak came on a vacuum deposition method >independantly. > A great deal of work on vacuum coating was done in the >US during WW-2. This is detailed in a publication available >on line from the Society of Vacuum Coaters site at >http://www.svc.org Since all German patents were seized by >the US government during the war there would have been no >patent infringement consideration.First, all governments seized the property of enemy nations during the War: Kodak AG in Stuttgart, for instance, was nationalized by the Germans, though Dr Nagel remained in charge. Similarly, the US seized Carl Zeiss U.S.A. but left Dr Bauer in charge. So, all German-held patents became the property of the US Government upon the adoption of the Alien Properties Act, and thus open to all: the US government does not claim intellectual property rights on its possessions. (See Robert Heinlein's A DOOR INTO SUMMER for discussion, and, yes, I am grinning as I write this.)
Dr Bauer, incidentally, was the man who suggested fluoride compounds would be the most suitable for lens coatings though it was Dr Smakula who brought it all together in 1935. (Smakula was brought to the US in 1947 under Operation PAPERCLIP and spent the heart of the Cold War as the Chairman of the Physics Department at MIT, directing the guys in designing bigger and better H-Bombs. Dr Bauer remained as the head of Carl Zeiss U.S.A. until the Zeiss Stiftung repurchased it in 1959; he had irked the mavens of Heidenheim by cheerfully refusing to recognize that Zeiss had moved west and that the guys in East Germany were now a Communist VEB, so he represented Jena and Dresden along with Oberkochen and Stuttgart. He was promptly retired in 1959, albeit on a full Zeiss pension and a US government one as well.)
There are two main methods for coating. The less satisfactory of these is to drip the compound onto the lens element and allow it to dry. This takes a lot of manpower, is slow, and leaves a moist and unstable coating which often flakes off when it dries. The better method is that developed by Smakula, the use of vacuum to deposit the compound onto the lens. This can be done quickly, requires little manpower, and leaves a much hardier coating. The vacuum method was developed independently at Carl Zeiss Jena, by Ross in the UK and by both Wollensak and Kodak in the US. Wollensak then manufactured all of the rangefinder gear and gunsights to the US military, and they began supplying coated units in 1939. Ross supplied coated binoculars to the British Army around the time of the Munich Surrender in 1938. Kodak started shipping commercial coated lenses in 1940. And CZJ certainly marketed coated T-marked lenses around the same time: I own a 1.5/5cm CZJ Sonnar T in Contax RF BM sold in Roanoke, Virginia, in March, 1939.
I am not certain about Kodak, but the other firms do not seem to have patented the process. The government answer was to classify the method. No, Norden never "patented" his bombsight, but its production was HIGHLY classified, to the point where it was made in separate assembly lines and the sub-components were then mated, so that no worker ever got the entire picture. The Germans had a slightly different system, one which flies in the face of all logic and reason. Smakula was granted German Patent 685,767 in November, 1935, but the patent was immediately judged to be "gehiemgehalten", or withheld from publication for security reasons. The process was only revealed when Smakula published its details in a minor German technical journal in February, 1940. The publication date is REALLY odd, as Germany was very much bogged down in the Sitzkrieg, or Phony War, at the time, so why tell your enemies a convenient method of improving optical performance? No one knows!
The Zeiss patent was extended for these four and a half years of secrecy and so only expired in February, 1960. During this time, all German optical firms had to either deal with Zeiss for permission to use the Smakula method or use drip coatings. Zeiss freely licensed the process: Schneider, for instance, was allowed to use it in return for supplying JSK Xenars for use on Zeiss Ikon folders in 1948. Voigtländer got the right when it was purchased by the Zeiss Foundation in 1953. The only firm NOT permitted access to the technology was Ernst Leitz Wetzlar -- payback is HELL and revenge is a dish best served cold and take that, Max Berek! So, Leitz lenses from 1946 to 1960 have shabby coatings for the most part, though John Van Stelten at Focal Point can certainly fix that up in a jiffy.
I am certain that Kodak used vacuum coatings. Why I say this, I do not know, but I am certain of this. Perhaps I ought to ask this over on the Internet Directory of Camera Collectors, which includes not only a number of Compur Shutter freaks but also a bunch of Kodak experts.
Marc msmall@xxxxxxxxxxxx Cha robh bàs fir gun ghràs fir! --- Rollei List - Post to rollei_list@xxxxxxxxxxxxx - Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org - Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with 'unsubscribe' in the subject field OR by logging into www.freelists.org - Online, searchable archives are available at http://www.freelists.org/archives/rollei_list