I remember an Iris scanner demo from 20 years ago that worked because of the characteristic flutter / vibration of the iris as much as the pattern of the iris i

I remember an Iris scanner demo from 20 years ago that worked because of the characteristic flutter / vibration of the iris as much as the pattern of the iris itself. As I remember it it didn't work well with high pigment eyes (it worked brilliantly with blue eyes, less well with everyone else).