公开(公告)号：US11945256B2

公开(公告)日：2024-04-02

申请号：US17482522

申请日：2021-09-23

Applicant: Canadian Bank Note Company, Limited

Inventor： Thivaharan Thurailingam ,  Silviu Crisan

IPC: G02B5/18 ,  B42D25/29 ,  B42D25/342 ,  B42D25/351 ,  B42D25/435

CPC classification number: B42D25/435 ,  B42D25/29 ,  B42D25/342 ,  B42D25/351 ,  G02B5/1852

Abstract: A security device for security documents provides an angle-dependent Moiré effect. A security device for a security document and method for making the security device are provided. At least two interlaced laser engraved images form an angle dependent parallax effect. First and second images are laser engraved at a substrate of the security document. To render the security device more difficult to copy, a colour changing effect or a nonreciprocal transmission effect may be achieved by adding a coloured (absorptive or emissive) layer between or within non-laser engravable layers situated between the laser engravable layers, and/or by adding a patterned phase diffraction grating situated between the laser engravable layers.