1f64a66d   
   From: mscir@yahoo.com   
      
   On 9/13/2011 3:12 PM, Quadibloc wrote:   
   > On Sep 13, 12:09 pm, Phil Hobbs   
   >   wrote:   
   >> On 09/12/2011 07:32 PM, Helpful person wrote:   
   >   
   >>> The early lens design programs used a lot of simple calculations to   
   >>> limit computational requirements.  Most of these are not used anymore   
   >>> due to the speed of modern computers.  A few of the calculations   
   >>> included:   
   >>   
   >>> OSC (offense against the sine condition) to control coma   
   >>> Coddingtons to control astigmatism   
   >>> Conrady's formulae to control chromatic aberration   
   >>> Seidels to nudge a lens in the correct direction.   
   >>   
   >>> There were many others, but these are just a few that I remember.   
   >>   
   >>> It's interesting that these methods are can still be useful today,   
   >>> particularly for getting out of a local minimum.   
   >   
   >> Having a bit of derivative information is awfully helpful sometimes, and   
   >> Seidels remain very useful in system design, e.g. for figuring out how   
   >> thick an observation window can be as a function of aperture and field   
   >> angle.   
   >   
   > This discussion reminds me of a Youtube video I just bumped into:   
   >   
   > http://www.youtube.com/watch?v=BlkRkhg5kKs   
   >   
   > Looking for courseware on optical design, because I had found some   
   > courseware on computer architecture on YouTube a while back, instead I   
   > found this video which shows, with a Double Gauss lens as an example,   
   > how to get Zemax to avoid doing silly things.   
   >   
   > John Savard   
      
   Thanks for posting that, very interesting.   
      
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