From: boxman@voyager.net   
      
   On 11/27/2013 7:54 AM, Gash M wrote:   
   > Hi all,   
   >   
   > I would like to write a routine (either in c or matlab) which can be   
   > used to collapse a given conic or aspheric surface to Fresnel zones,   
   > which is basically designing a Fresnel lens from a given lens   
   > entity(surface). Fresnel Lens(FL) which has prismatic facets is easy   
   > to implement.But in this case the facets have to be conic(aspheric)   
   > and different ways of realizing the FL is possible like fixed sag per   
   > zone and fixed zone spacing.That is the general goal. My problem is   
   > breaking down this problem into smaller pieces to make it easy for   
   > coding. Therefore, my question is : what are the basic blocks that my   
   > code needs to have to construct a FL from a given surface? A sample   
   > code would be appreciated.   
   >   
   > Thanks, Gash   
   >   
      
   I can't be of much help providing a way of collapsing a conic or   
   aspheric.  I'm not entirely sure how that would help you to design the   
   lens you are trying to create.   
      
   It seems a more direct approach would be to design the actual surface   
   you want by using edge rays to define the boundaries of each facet and   
   then solving for the cartesian oval section that collimates those rays.   
     If you are putting the facets on the outer surface of your lens, you   
   will need to use the virtual focal point of your edge rays that is   
   formed after they refract at the front surface.  The formula for the   
   cartesian oval fitting through a point is too complicated to post in the   
   newsgroup but can be found in parameteric form in the text Introduction   
   to Nonimaging Optics by Julio Chaves. (I would suggest you get a copy if   
   you are doing illumination designs). I have written C# code based on the   
   equations in the Nonimaging Optics text to do the cartesian oval   
   calculation, so I'm sure you could develop C code to do the same thing   
   for your specific problem.   
      
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