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History of multicoating
The binocular was produced near the end of the second war.
Following by Dr Stephen Rohan research, we can learn that in 1936 Carl Zeiss made a discovery of using a vapor coating on the surface of the component lenses of the binocular.
But we have, in our collection 8 x 60H binocular from September 1935 with original coating.
The official German statement was from 1936, but a few was done before.
The coating reduced the amount of light lost in the binocular because of light reflection from the surfaces of the glass elements.
Dr S. Rohan says: “The first coating materials were very soft, and easily damaged therefore, they were generally applied only to the interior of the binocular lenses” (look at the literature list - poss.).
Martin C. Cohen in his article: “Carl Zeiss – A History of a Most Respected Name in Optics” says:
“Another noteworthy milestone was on November 1, 1935 when by then a staff at Zeiss (Aleksander Smakula) developed and then patented antireflective (T - Transparenz) coatings thereby improving light transmission dramatically over uncoated lenses in binoculars to over 80 per cent,...” *)
Aleksander Smakula worked at ‘The Carl Zeiss AG company’, in Jena from 1934.
In the same period over antireflection coatings had worked two scientists: Katherine Burr Blodgett and Irving Langmuir. They developed organic antireflection coatings.
Katherine Blodgett was working, as first women, for General Electric Laboratory in Schenectady, New York, were was Dr Irving Langmuir working as well. Both scientists were working on mono molecular coatings design (mono layer - a single closely packed layer of atoms, molecules or cells), to cover surfaces of water, metal or glass. These coatings were oily.
Katherine Blodgett discovered a way, how to spread these mono molecular onto glass or metal. She used a barium stearate (also known as Barium Salt of Stearic Acid) film to cover glass with 44 layers, which made the glass more than 99% transmitting, creating an ‘unseen’ glass.
This kind of coating was named as Langmuir-Blodgett.
Inspired with soap bubbles, Katherine Blodgett invented the colour gauge. She noticed that the different thickness of the soap bubbles gives new colors. She worked out a glass rules to show different colors corresponding to the thickness.
Katherine Blodgett was the first woman to earn a Ph.D. degree, in physics from Cambridge University, in 1926.
At 5th November 1940 Dr Blodgett issued three US. Patents: “Film structure and method of preparation”; “Reduction of Surface Reflection”; “Low-Reflectance Glass”. **)
It seems that the Aleksander Smakula method of multicoating was the best. Presumably, the temperature and vacuums applied during the coating process has given stronger coatings of the lenses.
Additionally, the surfaces of the lenses are degreased and antireflection coating applied by magnesium fluoride. The prism plates are located in the nests of the evaporator tray. Application of the coating is done by vapor deposition of magnesium fluoride in a vacuum. The process consists of three stages lasting about 1 hour. The first phase is a heating chamber to 300 degrees Celsius. This is followed by ion cleaning. The third phase is a proper vapor deposition occurring in a high vacuum, of 10 to minus 5 Torr. ***)
The method described above was applied by PZO in 1970s and in Wetzlar in 2006. In Wetzlar the temperature was applied to 400 C.
Presumable the similar method was applied by Aleksander Smakula.
As Martin C. Cohen says: “By 1990, Zeiss Oberkochen improved the anti reflecting coatings to transmit more than 90 % of the light of the light entering a binocular (the T* designation). In 1988 ‘Phase Correction’ coatings were introduced on all Carl Zeiss Oberkochen roof prism binoculars to further improve resolution and contrast of roof prism”.
The improvement of the anti reflections coatings is very controversial. Many sources pointed different percentages of development.
Hensoldt in the factories catalogue from about 1963-1964 says: “E-coating eliminates every disturbing reflected image in the binocular and increases the light transmission extremely - about one third more than in uncoated glasses”. In the Hartmann Wetzlar catalogue (1970) is pointed to 30 -35%. When in Carl Zeiss Jena catalogue (1952) is told that a light transmission in Zeiss T optic is 80% against 60% for non coated binocular. The catalogue of Carl Zeiss Oberkochen/Württ, also from 1952, opted for 50% improved of the light transmission.
We could conclude that parameters founded, before experiments were different in each factories and with different binoculars, presumably with a different elements of glasses. In this way the results of trials are dissimilar.
The German discovery was kept as a military secret, in the early years of WW II, because of the military importance. During the war the harder coating process was developed. It allowed to applied antireflective coatings to the outer lens elements. But the coating was still not as hard as that applied after the war. This information it is easy to confirm making a close examination, of the binocular objective. Unfortunately, many tiny scratches are visible.
The coating lenses were marked on the binoculars body with a capital letter “T”. We have not seen this mark on any 10 x 80 multicoated binoculars.
As Dr Blodgett described; the coating glass does not have colour.
Let’s look, in short way, how lens coating works. In the most easy way, we could say that the reflections from the glass, and from the coating surface, cancelling each other.
Reflections, physicists described as reflected waives of light. When a light wave strikes the glass surface, some of the ways bounce off as a reflection. The reflected ray has the same wave as the incident ray, only moving in the opposite direction.
As a wave, the reflection can be cancelled out, when that other wave can be made to be equal frequency, direction and magnitude, and opposite phase. The equal frequency has to obtain differently for all colours, visible in spectrum of light.
The production
The binocular was made by Emil Busch cxn and is no markings on the body to indicate it is a coated version.
Interesting is that the manufacture of multicoated binoculars were at least three groups of the serial numbers , mixed with the production serial numbers of uncoated glasses 10 x 80, produced by Emil Busch.
The body of multicoated binoculars are, in majority, in German army tan colour. It appears that it was produced in gray colour as well.
Fred König - the binoculars’ collector from Germany has sent the pictures from his collection. The body of the binocular is in original gray colour. It is the first binocular we have seen in this colour.
The picture of Fred König binocular
The picture of Fred König binocular
The binocular is unusual in other way. It has a deferent serial number as from a different serial group of the binoculars production. The number is - 77263.
The picture of Fred König binocular
The serial number of the binocular from our collection, in tan colour, is: 112574
The binocular was fully and professionally serviced by Terry Vacani.
The 10x80 multicoated in our collection
The other collectors sent us, serial production numbers of their multicoated binoculars, in tan colour:
The list of production numbers of the multicoated binoculars, which were sent to us:
- 101445;
- 101459;
- 101828;
- 101858;
- 112574; (from our collection)
- 121791;
- 77263; (gray colour);
The picture of Patrick Quentel binocular
The picture of James Wilkie binocular (sent by e-mail as a respond to this article)
The picture of John Coe, Hamilton, MT, USA binocular (sent by e-mail as a respond to this article)
The colour of coating is not every time the same, sometime it is orange-red, other time reddish-purple. The outside coating is easy to scratch and difficult to clean.
The binocular from our collection - serial production number: 112574
The picture of Patrick Quentel binocular
The picture of James Wilkie binocular (sent by e-mail as a respond to this article)
All glasses are coated, inside and outside surfaces. All filters are coated from both sides. Only one element is not coated, it is reticule. The filters selector knob and the eye width control knob always made from brown Bakelite.
As far as today, we now only five collectors, they have this binocular in their collection. This binocular is not a rare binocular, but you can seldom find one with good coating on the outside of the objectives and eye lenses. In the past we have seen, in Belgium, four complete binoculars of this model in like new condition. The owner of this binoculars valued them highly.
The French collector Patrick Quentel, a big enthusiast of this model, says; it is a fantastic picture compared with the normal uncoated 10 x 80 45Ëš.
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