METHOD OF INSPECTING PAPER AND APPARATUS THEREFOR (VERSIONS) Russian patent published in 2014 - IPC G07D7/00 D21H19/62 D21H21/40 

FIELD: physics.

SUBSTANCE: method of inspecting paper with optical protective marks on banknote threads involves synthesis of a flat optical element with an asymmetric microrelief. An asymmetric image is formed in an optical element to allow automatic inspection, invariant to the shift of the banknote and turning thereof within 10 degrees when the protective mark is illuminated with a laser beam perpendicular to the plane of the banknote. The image is in form of bright sections, parallel to the direction of movement of the banknote in the channel of a counting and sorting device, lying in the focal plane, parallel to the plane of the banknote, or in planes Q₁ and Q₂, each inclined to the plane of the banknote by an angle α, which is less than 60 degrees. The line of intersection of planes Q₁ and Q₂ is parallel to the direction of movement of the banknote. The control feature for identification is the distance from each of the sections to the laser beam. The apparatus for inspecting paper with optical protective marks on banknote threads includes a diode laser, a detection system, an electronic unit for recording information from a line of photodiodes and an electronic unit which performs automatic inspection. The diode layer emits a laser beam perpendicular to the plane of the banknote.

EFFECT: high protection of optical marks from forgery, high reliability of identification and invariance of the inspection procedure at high speeds of the banknote in the channel of a counting and sorting machine.

3 cl, 16 dwg