Use and efficacy of DOVIDs and other optical security devices

Nanooptical elements for visual verification

“…Let us consider area G (1) (Fig. 2c), which consists of elementary areas G ij , where (i + j) is even, and area G (2) , which consists of elementary areas G ij , where (i + j) is odd.…”

“…(1) ij (x, y) = C • ρ 2 cos(2φ) and the phase function � (1) ij (x, y) of the multilevel kinoform that forms the image of symbol «A». In elementary areas G ij in area G (2) , the phase function of the optical element is equal to the sum of the given function h In variant 3, when the optical element is illuminated by a point source, the observer sees three symbols «A», «B», and «C», which «diverge away from each other» when the element is tilted, and the angles between the symbols are equal to 120°. Similar to variants 1 and 2, area G is subdivided into nonintersecting areas G (1) , G (2) , and G (3) , as shown in Fig.…”

“…Experts in the technology of banknote production viewed this event as somewhat exotic. Banknotes in circulation must meet very stringent requirements, and the first incorporated optical elements hardly helped to increase the banknote lifetime 2 . An obvious advantage of these elements was that they improved the protection of banknotes against counterfeiting.…”

Optical Document Security: Measurement, Characterization and Visualization: in the Light of Visual Evaluation

“…text we can relate a concept used by the US Secret Service: the phrase "passable product" is used to denote an item which may be fake but which has been accepted (passed) by a lay person or even a retail clerk [44].…”

“…Another challenge is, especially regarding the general public and first line inspection, the strong belief that no document is a counterfeit. Information campaigns are then ineffective, and inspectors will remain ignorant and inspections will remain infrequent, hence over-all ineffective inspections [44].…”