I went back and read the article again, and this time I found the part that
says there is a spring that closes the iris, and the current opens it.  So =
I
believe you are correct.  I was in doubt before I went back and read it, an=
d
those illustrations with the op amps certainly suggested otherwise.  In the
end, I would suggest applying a small current to the lens and seeing how it
actually works.  You have the advantage of having the actual part in front
of you.

Just a comment about "galvanometer":

I understood the theory a little different. The iris mechanism is
> galvanometric, so we need to apply the current in only one direction,
>

I looked up the definition, ,just  to be sure, and there's nothing about
galvanometers that implies current in one direction only.  Nowadays the ter=
m
seems to mean "current driven" and "very sensitive".

Barry
--=20
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