I have the physical design worked out for how I'm going to move the iris center, and allow for an iris that I can change in size at the same time without moving the entire mechanism to do it.. I think.

The current idea is to move part of the iris closure mechanism, which normally is purely rotational, to allow for (x,y) movement as well and then to try to compensate for the uneven closure of the leaves blocking the light by enlarging them a bit.. so the generated center *can* be off-center without creating gaps in the blocked portion.

I'm not really confident in which portion of the offset motion I should be moving to get the desired effect here.  I could move the part that contains the end pins, or I could move the pins which ultimately reside in carved channels.

I'm trying to turn this into code, but my initial path of generating this arc has taken me to generating the shape needed from the resulting motion of the leaf itself.  But... that motion is just a simple rotational motion right now.

It will probably be easier to generate both outcomes in hardware and physically test them than it is to attempt to model it.

So in the end I really don't know if I can do this yet.  We will find out soon.  If I was doing this in FreeCAD instead of OpenSCAD I could probably define constraints allowing me to do this faster without a lot of math  But I want to do it in OpenSCAD.   

Silly in a way, but here we are.  :)

I'm confident that the idea will work.  To what extent I can relocate the center of X,Y in either mechanism and still had a good looking, round iris opening is the question here.

It is novel in a way that I don't have any data to back up the second assumption.  Experimentation ensuing.