Interesting that this is a paid for view document... <A HREF="http://bookstore.spie.org/index.cfm?fuseaction=detailpaper&cvips=PSISDG004129000001000494000001" target="_blank">http://bookstore.spie.org/index.cfm?fuseaction=detailpaper&cvips=PSISDG004129000001000494000001</A>