From: rrllff@yahoo.com   
      
   On Wednesday, November 27, 2013 10:06:08 AM UTC-5, Gash M wrote:   
   I know how to model conventional FL in commercial products like Zemax.My   
   interest is to write a code which can collapse a given surface to Fresnel   
   zones. Could you give me some guidance how to start?   
      
   > Thanks,   
   >   
   > gash   
      
   Sorry, I've never created such a model.   
      
   However, I suggest that you start graphically.  (An   
   old fashioned drafting board is ideal.)  Draw the   
   original surface and on the same paper draw the   
   Fresnel solution.  This should lead to a step by step   
   solution.   
      
   Once that is done don't forget to determine the cut   
   back angles, chosen to minimize vignetting.  Also   
   determines TIR in the pseudo prisms.   
      
   http://www.richardfisher.com   
      
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