[wnkrshm]

Concerning the moving piston: Rather than have a moving plane, they could be using stacked, electrically-switchable films. Ones that you can switch from transparent to only translucent (i.e. scattering) very quickly. (http://en.wikipedia.org/wiki/Smart_glass)

[munk]

We did consider that but smart glass is too far slow to turn on and off for it to work.