From: hwabnig@.-   
      
   On Thu, 6 Sep 2012 16:38:26 -0700, James Klein   
    wrote:   
      
   >Hi,   
   >   
   >I had a very difficult time understanding what the Partial Coherence   
   >option in the MTF option of Code-V really was all about.   
   >   
   >I asked people smarter than myself for 10 years+ to no avail. There are   
   >lots of people smarter than me.   
   >   
   >Then one day, walking down the street and thinking about a totally   
   >unrelated topic (hot women), it came to me.   
   >   
   >The Partial Coherence Code-V option was used in computing MTF in the   
   >EUV illuminator optical system designed by ORA for TRW in the early   
   >90s. It was part of an exterme UV illuminator for use in   
   >micro-lithographic applications. In one plane of the resist, Koehler   
   >Illumination was used. In the other, Direct Illumination.   
   >   
   >In direct Illumination systems, the source of the lithograph is   
   >directly illuminated as opposed to filling the aperture stop of an   
   >enlarger lens. When you do that, the stop of the imaging system is not   
   >filled as in usual systems and the illuminator system shines on the   
   >source and on the image. So when you auto-correlate the "pupil" of the   
   >system, it is just a pin-spot of light across the aperture and the MTF   
   >stays 1.0 to half the cutoff frequency and then drops to zero (100%   
   >"coherence").   
   >   
   >At zero coherence, the pupil is fully filled and you get the tail-off   
   >MTF curve of a condenser enlarger or a Koehler Illuminated microscope   
   >system. At intermediate coherence settings (Code-V lets you set the   
   >coherence %), you get a transition from the square cut-off at half   
   >cut-off frequency to the regular MTF curve at zero coherence).   
   >   
   >I'm sure I'm the only person who ever obsesed over this for as long as   
   >I did and when I understood it, I thought I'd share.   
   >   
   >And NO, I was not smoking Cannabis when I wrote this !   
   >   
   >Jim Klein   
   >   
      
   It's called sigma or fill factor.   
   http://tinyurl.com/8pjntpo   
      
      
   w.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)