From: jeedom74000@gmail.com   
      
   On Wednesday, October 23, 2002 at 3:38:22 AM UTC+2, Phil Hobbs wrote:   
   >The best method for fringe surfing is to   
   > arrange two photodiodes so that they see opposite phases of the fringe   
   > pattern--e.g. when PD1 is on a bright fringe, PD2 is on a dark fringe.   
   > Wire the photodiodes in back-to-back parallel (anode to cathode), and   
   > connect this combination between the inverting input of an op amp and   
   > ground.   
      
   Phil, that simple setup sounds very appealing but I have been struggling to   
   understand how that would work.   
   Could you detail how the "Wire the photodiodes in back-to-back parallel (anode   
   to cathode)" works because as I understand it, that would add the charges   
   measured by the two photodiodes while I would normally want to subtract one   
   from the other, no?   
   Many thanks   
   Loic   
      
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