1. 
   parfocal
   Microscope objectives that are mounted in such a way that changing objectives does not put the specimen out of focus are parfocal.
   Found op http://www.encyclo.co.uk/visitor-contributions.php
   
   
2. 
   Parfocal
   Par·fo'cal adjective [ Pari- + focal .] (Opt.) With the lower focal points all in the same plane; -- said of sets of eyepieces so mounted that they may be interchanged without varying the focus of the instrument (as a microscope or t...
   Found op http://www.encyclo.co.uk/webster/P/23
   
   
3. 
   Parfocal
   • (a.) With the lower focal points all in the same plane; -- said of sets of eyepieces so mounted that they may be interchanged without varying the focus of the instrument (as a microscope or telescope) with which they are used.
   Found op http://thinkexist.com/dictionary/meaning/parfocal/
   
   
4. 
   Parfocal
   A microscope that is “parfocal” is one which, if it is in focus with one objective, when the objective is rotated, will remain in focus.
   Found op http://www.greatscopes.com/glossary.htm
   
   

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