jaapv
RFF Sponsoring Member.
Err.. it is real glass. In fact, the optimal glass for the application. The problem being that it is a type of glass that can superficially corrode when humid, as is the case with a number of types of optical glass. The standard solution was to cement a second layer of glass over it, but as the M9 needs an extremely thin filter stack the alternative, a sealing coating was chosen.
The coating may either exhibit microscopic porosities in a small number of cases or be damaged mechanically, giving humidity a starting point to delaminate the coating.
The problem now is to find a more stable glass/coating combination that will not degrade the optical performance. That takes time, as testing for corrosion takes time, even in laboratory conditions.
The coating may either exhibit microscopic porosities in a small number of cases or be damaged mechanically, giving humidity a starting point to delaminate the coating.
The problem now is to find a more stable glass/coating combination that will not degrade the optical performance. That takes time, as testing for corrosion takes time, even in laboratory conditions.