From: rrllff@yahoo.com   
      
   On Friday, December 26, 2014 5:35:13 PM UTC-5, Phil Hobbs wrote:   
   > Merry Christmas, all (there are 10 days left) ;)   
   >   
   > These days the catalogue houses sell a lot of so-called nonpolarizing beam   
   splitters.  Since the Fresnel formulae are strongly polarization dependent,   
   making a broadband beamsplitter with only weak polarization dependence is a   
   bit of a parlour trick.   
   >   
   > Anybody know how they do that?   
   >   
   > Cheers   
   >   
   > Phil Hobbs   
      
   One trick is to put "dots" of 100% reflecting material on the surface.  If the   
   area of the dots is equal to the clear area one has a 50/50 non polarizing   
   reflector.  For many cases the diffraction effects are not important.   
      
   Another trick is to reduce the angle of incidence so that it is not 45 degrees.   
      
   Also, a large spectral bandwidth can be obtained with a low angular bandwidth   
   and vice versa.   
      
   http://www.richardfisher.com   
      
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