Some weeks ago i found chris schaie's [1] iris on hackaday [2] and i was so amazed that i took a screenshot from the video and made my own iris based upon his design.
From there it was a long road but eventually my own design worked out and i managed to create a mechanical iris that can be opened with a stepper motor.
Now we have a welcoming system at the metalab [3]

[1] http://schaie.com
[2] http://hackaday.com
[3] http://metalab.at

Documentation can be found @ http://metalab.at/wiki/iris

To build the thing you need

• a lasercutter
• wood (i used 8mm)
• 3 ball bearings from rollerblades
• a stepper motor + controller electronics