1931 Barnack Patent for Camera with Coupled Reflex Range Finder

[derleicaman]

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Hello Everyone, David Stephens posted this on the My Leica Historica group on Facebook and interesting picture with information on a Reichspatent application from 1931 for a Camera with Coupled Reflex Range Finder.  I am a bit rusty from looking up German patents from my story on Barnack and the PIX mechanical pencil I did a few years ago. Can anyone here give us a little help on this? I have been on the German Patent Office site, but am having a very hard time with it.

TIA for your help! Here is the image.

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Edited January 3 by derleicaman
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[dg4mgr]

Here we go. A camera with rangefinder coupled to the lens.

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[roydonian]

The British Library in London holds copies of German patents from that era – more than a decade ago I was able to see patents covering ultra-speed (Noctilux-class!) lenses devised by Zeiss designer Bertele, and order photocopies.

In those days the patents were held on open shelves in what was then the Science Reference Library, but now they are probably stored off-site. If the library is not able to deal with a photocopy request from outside of the UK, I might be able to help since I live not far from London, and am a registered user of the library.

[derleicaman]

29 minutes ago, dg4mgr said:

Here we go. A camera with rangefinder coupled to the lens.

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Looks like a long base rangefinder. More like the Contax I, rather than the Model II with its shorter RF base.

[derleicaman]

Thanks to Gerd, I was able to look at the original Patent document. I am attaching it here. I did a Google Translate on it, and here is the text.

Photographic camera with a mirror rangefinder coupled to the lens

 

Patented in the German Reich from October 23, 1931

 

The invention relates to a photographic camera in which the lens is coupled to a mirror rangefinder. The previously known couplings have the disadvantage that when the rangefinder and the lens are set simultaneously, the intermediate measurement values between the near point and infinity of both devices do not match completely, so that when the rangefinder is set together, the focus of the lens does not match exactly, and conversely, if the lens were set exactly, the rangefinder setting would not match exactly the actual distance. With the extremely fast lenses used today in cameras with a coupled lens and rangefinder, this lack of match is particularly noticeable in that the images taken still show a certain degree of blurriness from certain distances. In order to eliminate this defect, according to the invention, when focusing, the setting of the rangefinder and the lens in the intermediate measurement values between the near point and infinity is inevitably brought into line by the cooperation of an adjusting screw with a lever, whereby the adjusting screw is brought into line, or the lever or both parts have one or two suitably curved surfaces. The drawing shows two embodiments of the subject matter of the invention, namely Fig. t shows a design with an adjusting screw 3 screwed into the prism lever a of a rangefinder prism, which rests on the outer half of a horizontally cut axis of rotation 5. A lever arm 4, which rests with the other end 7 on the lens 6, follows the adjustment movement of the lens and thereby rotates the axis of rotation 5, whereby the adjusting screw 3 is moved up and down. The up and down movement adjusts the movable mirror prism 1 in the rangefinder. Because the adjusting screw is provided with a precisely calculated curved contact surface, the unequal relationships between the divisions of the rangefinder and those of the objective are approximately balanced out. For adjustment during assembly or for readjustment, the adjusting screw can be adjusted high or low and, if necessary, also laterally in the prism lever. Fig. 2 shows a design in which the unequal relationship between the divisions is eliminated by the lever surface on which the adjusting screw rests being provided with a precisely calculated curvature. Depending on whether the adjusting screw is screwed higher or lower in the lever arm of the rangefinder, the lifting effect of this lever changes. The axis of rotation 5, which is also designed as a lever arm 70, transfers its leverage when the lever 4 is rotated to the adjusting screw or to the lever arm a of the rotating rangefinder prism 1. Irregularities in the lifting effect, which cannot be completely eliminated by the 75 adjusting screw, are eliminated by the special design of the contact surfaces t0 or 11. The most advantageous design is the contact surface as a circular arc, the diameter of which 80 is selected so that the setting is the same in all intermediate measurement values for both the rangefinder and the lens.

 

PATENT CLAIMS:

 

1. Photographic camera with a mirror rangefinder coupled to the lens, characterized in that the setting of the rangefinder and the lens in the intermediate values between the close point and infinity is inevitably brought into line by the cooperation of an adjusting screw (3) with a lever (4.5), the adjusting screw or the lever or both parts having one or two suitably curved surfaces. 2. Photographic camera according to claim 1, characterized in that the axis of the lever (4.5) is offset and is itself designed as a lever arm.

DE000000589936A_all_pages.pdf

[willeica]

18 hours ago, derleicaman said:

Thanks to Gerd, I was able to look at the original Patent document. I am attaching it here. I did a Google Translate on it, and here is the text.

Photographic camera with a mirror rangefinder coupled to the lens

 

Patented in the German Reich from October 23, 1931

 

The invention relates to a photographic camera in which the lens is coupled to a mirror rangefinder. The previously known couplings have the disadvantage that when the rangefinder and the lens are set simultaneously, the intermediate measurement values between the near point and infinity of both devices do not match completely, so that when the rangefinder is set together, the focus of the lens does not match exactly, and conversely, if the lens were set exactly, the rangefinder setting would not match exactly the actual distance. With the extremely fast lenses used today in cameras with a coupled lens and rangefinder, this lack of match is particularly noticeable in that the images taken still show a certain degree of blurriness from certain distances. In order to eliminate this defect, according to the invention, when focusing, the setting of the rangefinder and the lens in the intermediate measurement values between the near point and infinity is inevitably brought into line by the cooperation of an adjusting screw with a lever, whereby the adjusting screw is brought into line, or the lever or both parts have one or two suitably curved surfaces. The drawing shows two embodiments of the subject matter of the invention, namely Fig. t shows a design with an adjusting screw 3 screwed into the prism lever a of a rangefinder prism, which rests on the outer half of a horizontally cut axis of rotation 5. A lever arm 4, which rests with the other end 7 on the lens 6, follows the adjustment movement of the lens and thereby rotates the axis of rotation 5, whereby the adjusting screw 3 is moved up and down. The up and down movement adjusts the movable mirror prism 1 in the rangefinder. Because the adjusting screw is provided with a precisely calculated curved contact surface, the unequal relationships between the divisions of the rangefinder and those of the objective are approximately balanced out. For adjustment during assembly or for readjustment, the adjusting screw can be adjusted high or low and, if necessary, also laterally in the prism lever. Fig. 2 shows a design in which the unequal relationship between the divisions is eliminated by the lever surface on which the adjusting screw rests being provided with a precisely calculated curvature. Depending on whether the adjusting screw is screwed higher or lower in the lever arm of the rangefinder, the lifting effect of this lever changes. The axis of rotation 5, which is also designed as a lever arm 70, transfers its leverage when the lever 4 is rotated to the adjusting screw or to the lever arm a of the rotating rangefinder prism 1. Irregularities in the lifting effect, which cannot be completely eliminated by the 75 adjusting screw, are eliminated by the special design of the contact surfaces t0 or 11. The most advantageous design is the contact surface as a circular arc, the diameter of which 80 is selected so that the setting is the same in all intermediate measurement values for both the rangefinder and the lens.

 

PATENT CLAIMS:

 

1. Photographic camera with a mirror rangefinder coupled to the lens, characterized in that the setting of the rangefinder and the lens in the intermediate values between the close point and infinity is inevitably brought into line by the cooperation of an adjusting screw (3) with a lever (4.5), the adjusting screw or the lever or both parts having one or two suitably curved surfaces. 2. Photographic camera according to claim 1, characterized in that the axis of the lever (4.5) is offset and is itself designed as a lever arm.

DE000000589936A_all_pages.pdf 139.81 kB · 12 downloads

Bill, this patent appears in its original German version in the book Oskar Barnack - from the Idea to the Leica on pages 172-174. I am referring here to the book by Ulf Richter which was translated by Rolf Fricke for LHSA/LSI. Pages 134 - 137 of the book give a very interesting overview of the whole process, in particular 8 criteria laid down by Barnack as to how the introduction of a built-in and coupled rangefinder should or should not affect the camera. e.g still fit in a pocket.

Interestingly, the book also contains on pages 200 -201  a US Patent in English for a 'combined distance meter and viewfinder', showing two options as regards prisms, which Barnack did not live to see in the Leica IV, and which eventually saw production in the M3.

A few points.

1. Leitz/Leica/Barnack often developed technical concepts many years in advance of their commercial introduction and there is substantial evidence of this.

2. There is little evidence of Leitz /Leica ever relying on their patents in respect of the many copies which eventually flooded the market.

3. There is evidence that Barnack always had an eye towards what Zeiss was doing, which befitted a man whose career had started with Zeiss.

William 

 

Edited January 4 by willeica

[derleicaman]

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William, Ulf Richter responded to me and said the same about this being in his book. He said this was in preparation for the Model II camera. The 1933 date threw me off, as the Model II came out in 1932.

[willeica]

1 hour ago, derleicaman said:

William, Ulf Richter responded to me and said the same about this being in his book. He said this was in preparation for the Model II camera. The 1933 date threw me off, as the Model II came out in 1932.

That book, our book, if you wish, is a goldmine of information and documents. It was great to meet Ulf and his wife in Wetzlar in 2023.

William 

 

[Rick in CO]

19 hours ago, derleicaman said:

William, Ulf Richter responded to me and said the same about this being in his book. He said this was in preparation for the Model II camera. The 1933 date threw me off, as the Model II came out in 1932.

The patent process could take some time from when the patent was applied for, ie. 1931, to when it was approved and published, in this case 1933.  Some items are found marked "ang.", for angemeldet, or applied for, which enabled the manufacturer to release products having the invention, under full patent protection, prior to publication.

[jaapv]

Leica did indeed come up with a prototype the Leica IV from 1935. Image from Johnathan Eastland Leica Compendium 

 

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[dg4mgr]

Note the patent is about coupling the rangefinder to the lens movement, not about a combined viewfinder/rangefinder. The patent was filed in 1931 and protects what has been done in the Leica II (D) that appeared in 1932.