Method and device for the detection of counterfeit documents and banknotes

A device for the identification of banknotes and documents marked by OVI™ inks (Optical Variable Inks), comprising:

• a light source;
• a first polarizing filter (3) placed between the light source and an area to be assessed, the area including a marked area treated with an optical variable ink and an unmarked area;
• a second polarizing filter (7), in anti-phase with said first polarizing filter (3) and placed in the track of a ray (6) reflected the area to be assessed;
• a third polarizing filter (8), in phase consistency with said first polarizing filter (3) and placed in the track of the ray (6) reflected by the area to be assessed;
• a first luminosity sensor (9a) in the track of the reflected ray (6) downstream the filter (7) and configured to provide a signal sa;
• an
• a second luminosity sensor (9b) in the track of the reflected ray (6) downstream the filter (8) configured to provide a signal sb, wherein
• said first luminosity sensor (9a) and said second luminosity sensor (b) are connected to a signal processor (10) configured to calculate a difference Δ between the signal sb and the signal sa.

A device for the identification of banknotes or documents marked by OVI™ inks (Optical Variable Inks), the device comprising:

• a light source;
• a first polarizing filter (3) placed between said light source and a marked area of a banknote or document to be assessed (5);
• a second polarizing filter (7), in anti-phase with said first polarizing filter and placed in the track of a ray reflected by the marked area to be assessed (5);
• and
• a third polarizing filter (8), in phase consistency with first polarizing filter (3), placed in the track of such a ray (6) reflected by the marked area to be assessed (5);
• a first luminosity sensor (9a) in the track of the reflected ray (6) downstream the filter (7) and configured to provide a signal sa;
• a second luminosity sensor (9b) in the track of the reflected ray (6) downstream the filter (8) and configured to provide a signal sb
• wherein,
• said first luminosity sensor (9a) and said second luminosity sensor (9b) are connected to a signal processor (10) configured to calculate a difference Δ between the signal sb and the signal sa, and
• said signal processor (10) is connected to a data processor (11) configured to compare difference Δ with data in a database (12) containing reference values Δr of genuine banknotes or documents.