Varifeye Window
A hole in the paper covered by a transparent film (with liquid-crystal or other coatings) from one side of a banknote. Design features within the Varifeye change in contrast as a banknote is moved over a black or white background. There may also be a kinetic affect. The feature is produced during the manufacturing process of the paper substrate and has fibers forming a kind of fringe along the perimeter of the hole (fig. 1).
a
b
Fig. 1. Varifeye. 20 Bulgarian Leva (2005):
a – against the dark background; b – against the light background