Dear Sam,   
      
   The periscope principle is indeed exactly what I need.   
   I just did not know where to start looking.   
      
   Thanks a lot!!   
      
   > This problem is closely related to the design of submarine periscopes.   
   > It is not a big deal to learn about the optics involved, but don't   
   > expect someone to do the design work for you for free.   
   >   
   > Sam   
      
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