The optics of non-collimated exposure machines are much less sensitive than the
optics of collimated machines, though it is not true that scratches on the
optics of collimated machines will reproduce on the panel.  Damage on reflectors
in general (on both collimated and non-collimated systems) normally result in
loss of energy at the exposure plane.  Our technicians are taught to clean
optics in a three-stage method.  First try blowing the optics clean with
nitrogen gas under some pressure.  If the contamination remains, then try a
rinse comprised of 50% isopropyl alcohol and 50% de-ionized water.  If the
reflector requires still more cleaning then soak a lint free, soft cloth with
the above mixture and wipe the optics with a very gentle pressure, making sure
that the cloth/reflector contact is well "lubricated" with the liquid mixture.
Any further attempts to clean will probably damage the coating on the optics and
defeat the purpose of the cleaning.

Paul Waldner
Multiline International Europa
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