[Petwksp] false pleochroism in plane light

[William Peck]

Hello all-
 
Apologies for cross-posting of this message.  I have a question for those of
you who have bought binocular teaching petrographic microscopes in the last
few years.  Recently we have noticed that the microscopes we have looked at
have some kind of pleochroism-like effect in minerals that should not
exhibit it. Sometimes this is minor but other times it is very noticeable.
 
We have seen this effect in Meiji and US Micro scopes from different
salespeople, and when shown the problem they have been able to minimize the
effect but not eliminate it. We have swapped around components and I think
the problem is perhaps introduced somewhere in the binocular head.

Is this something any of you have encountered?  It is very noticeable, and
I¹m surprised that our salespeople haven¹t had min/pet instructors from
other schools as frustrated as we are. Any thoughts/experiences would be
appreciated.
 
William