I wworked for 6 momths for a company that manufactured thin-film optical
filters.

The glass pieces were placed ina vacuum chamber. along with the
crucible(s) with the coating material(s).

Once the chamber was evacuated an electron beam was used to heat the
coating materials, which usually sublimed and were directed magneticaly
to the glass.

I still have one of the electron guns (filament burned out). It looks
like an oversized tube with an open ended glass tube on one side where
the beam was directed out.

--
"Peace is that brief moment is history when everybody stands around
reloading,"--

Rev. Skip Heitzig