Self-verifying Filter
A clear window with a filter (coating) which can visualize latent images or texts located on the same banknote. When bending the notes, the filter is placed over the area containing such an image (fig. 1, c), which changes colour and becomes visible (fig. 1, b).
a
b
c
Fig. 1. Self-verifying filter. 10 Brazilian Reals (2000):
a – image without filters; b – through the filter; с – verification process