Reading the machine translations, my guess is that the technique involves something like 2 immiscible liquids, one coloured, i.e. semi-opaque, in a gap between 2 glass elements. Within the gap between the 2 outer glass surfaces, the clear liquid is in the middle (the optical axis passes through the middle of the zone of clear liquid), and the opaque liquid is in a ring around the edge, outside the clear liquid.
A force, controlled electronically, perhaps via piezo actuators, moves the glass elements apart or together, changing how the liquids are dispersed in the liquid gap, and thereby changing the "width"/"aperture" of the "iris" formed by the opaque liquid. Also, towards the edge of the opaque liquid, it is thinnest there, so its optical attenuation is lower at that edge, so optically, the attenuation at that edge is not a step function, but rather a function of the shapes of the enclosing movable glass surfaces.
I dunno. I'm guessing!