3D moving eyes - how?

I want to build a set of animatronic eyes that can move around, as well as dilate and expand the irises in a controlled manner.

My current rough idea for this is to have an inner eye stalk that moves around via nitinol muscle wire to simulate eye movement, and a magnifying lens that can adjust the distance between itself and the image of the iris at the end of the stalk to zoom in or out (making it look like the iris and pupil are 'contracting' or 'expanding').

I whipped up a pretty good HD image of what I want the eyes to look like, but I'm having trouble figuring out how to make a 2D, flat image look like a 3D, convex surface such as a real human iris to an outside observer. Any ideas? I don't really know enough about lenses to understand how to go about this, and I don't really have anything to test my ideas with. Ideally, the end result would be more or less indistinguishable from a scaled-up human eye, where the iris 'appears' to be right at the surface and moves across the surface of the eyeball appropriately.

This is interesting:
http://forums.stanwinstonschool.com/discussion/854/pupil-dialation-and-expansion-in-artificial-eyes

Agree with udog. For the kind of advanced effects your asking for you really should invest in a few of the relevant videos by The Stan Winston School of Charactor Arts online. Thier lessons are comprehensive and will show you how to do what you want to do.

I watched through all the how-to videos on the channel that was linked. While the electroactive polymer approach does seem great in terms of fluid 'animation' of the object, and relatively simple to implement, I didn't get a very good idea of how far the polymer object can expand, only that it does so in a fluctuating manner depending on the AC frequency (how would one get it to hold a given size?)

The third video down the page ("Animatronic Dilating Eye") seems the closest to what I want out of this, as the pupil can rapidly change size and stay at a new and quite different size for as long as necessary, but unfortunately, there isn't much there in the way of explanation. I tried following a link to the Stan Winston website where an explanation might have been found, but it seems I need to pay for access, and I'm unsure I want to commit to that just yet.

The reason I'm looking for other methods to simulate an eye is that the character I'm building an animatronic replica of has very large, oval-shaped eyes, nearly 7.125" by 5.6875" in area, and the iris size changes dramatically from something like a 7" by 2.5" oval to 3" by 1", a little less than half the original size. Gotta love cartoons.

I fooled around with an idea of using an OLED screen and a pair of digital images, but I couldn't figure out any way to make that look like a set of 3D, convex eyeballs, so that was dropped. I *could* technically create a pair of actual, giant eyeballs with the iris on the surface, and figure out a way to make the irises contract on that surface, but the radius of curvature of the eyes is so large that the two spheres would almost definitely bump into one another within the skull.

What if I 3D-printed an image of the eye with a 3D curvature to it, cast it in silicone, and then put that behind a magnifying lens? That would solve the 3D problem, but I'm unsure if it would 'look right'. Plus, there's still the issue of finding or making a magnifying lens big enough for that...

EDIT: Another idea would be to print the eye image on the surface of a small balloon, and use a controlled reservoir of air to inflate and deflate it as needed. This would 'stretch' the image, though...

Alternatively, instead of nitinol, I could use a magnetic backing on an image of the iris situated in a fluid reservoir between two lenses, and an electromagnet to move the iris around without any visible actuators. Problem is, I've no idea how this one would expand or contract.

If you only watched the highlights then your only getting an insight into the lesson. Yes you have to pay but their lessons can be as long as 3 hours. And you get to keep the lesson and rewatch as often as you like. If they do a lesson on animatronics eye dilation they'll cover everything you need to know. They are expensive which is a bummer. When they first started their lessons were only $19. But the price has quadrupled. Sorry are can't be of more help, unless a special effects expert (there are a few here) chimes in its the only advice I can give.

Actually managed to find this on YouTube, and I'm slapping myself for not thinking of it earlier:
https://www.youtube.com/watch?v=GmjY_4tr0gc
Since my animatronic's eyes aren't spherical (and don't have spherical curvature), that might make things slightly trickier, but this still solves all the problems I was trying to tackle earlier. I'll try to post pictures once I get this thing working!