A diagram showing the 4F correlator from Fourier Optics
<a href="//commons.wikimedia.org/w/index.php?title=User:Rswarbrick&amp;action=edit&amp;redlink=1" class="new" title="User:Rswarbrick (page does not exist)">Rswarbrick</a>
2008-12-31
<span class="int-own-work" lang="en">Own work</span>