Anti-Stokes Ink
An ink which contains crystals of rare-earth metals (ytterbium, thulium, etc.) and luminesces when exposed to high-intensity IR light 970-990 nm.
a
b
Fig. 1. USA. Passport issued in 2006:
a — сover. Gold stamping. White light; b — the same. Anti-Stokes, green luminescence: text, emblem, biometric symbol
a
b
Fig. 2. Russian Federation. Residence permit to a stateless person issued in 2012:
a — front endpaper. Paper substrate. Green decorative frame, intaglio printing. White light; b — the same. Anti-Stokes, green and red luminescence of the guilloche frame
a
b
Fig. 3. Poland. Service passport issued in 2012:
a — front endpaper. Paper substrate. White light; b — the same. Anti-Stokes, green luminescence over the whole document page
a
b
Fig. 4. Poland. Visa issued in 2011:
a — paper substrate; b — the same. Anti-Stokes, green luminescence of the number