microscopy links
Koehler illumination:
http://www.microscopyu.com/tutorials/java/kohler/
Phase contrast imaging:
http://www.microscopyu.com/articles/phasecontrast/phasemicroscopy.html
http://www.microscopyu.com/articles/phasecontrast/phaseconfiguration.html
Fluorescence imaging:
http://www.microscopyu.com/articles/fluorescence/filtercubes/filterindex.html