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RE: [Rollei] 5 element Xenar

At 08:33 AM 01/09/2002 -0800, you wrote:
>     Richard,   Wasn't the Angulon a modified Biogon? As the the 5-element
>design it looks similar to the way the Heliar is designed. It would be
>interesting to see how well it would perform.  Peter K   > -----Original
>> From: Richard Knoppow [mailto:dickburk  ] 
  The _Super Angulon_ is similar to the second type of Biogon (the first
was a completely different type of design) which is itself based on a lens
by Roosinov. These are essentially back to back reverse telephoto lenses.
Roosinov's patent is USP 2,516,724, which is interesting to read. 
  The original Angulon is a Dagor type lens with the order of powers
reversed from the Dagor. The  negative elements are on the outside.
Actually, von Hoegh shows this form in his patent. Becaue the lens is
thicker than the ordinary Dagor form. In the Angulon the outside elements
are made extra large to avoid mechanical vignetting. This is quite
successful since the circle of illumination is around 102 degrees. However,
for good image quality the coverage is no better than a wide angle Dagor,
namely about 90deg. The Angulon patent is USP 1,882,530
  The original Biogon type was a modified Sonnar, quite different from the
semi-symmetrical later Biogon. 
  Any U.S.patent can be gotten from the patent office web site at
http://www.uspto.gov  Some US government sites are down or partially down
right now due to some bizarre law suit. To look at the patent images you
need a plug-in capable of displaying the fax tiff files used (the patents
were scanned using fax machines). The best is Alternatiff, available free.
Do a google search to find it. 
  The Wang Imaging, now Kodak Imaging in Windows will dilplay stored fax
tiff files. 
- ----
Richard Knoppow
Los Angeles, CA, USA