SECURITY READER FOR AUTOMATIC DETECTION OF TAMPERING AND ALTERATION

摘要

A document (10) is covered by a laminate (13) comprising a layer of microspheres (16) over an adhesive layer (14) covering a sourceimage (12) such as photograph, printed matter, or a bar code arranged on a substrate (11). Light impinging on the document (10) is splitby the optical properties of the microspheres (16) and underlying specular reflectors. The remaining light passes through the microspheres(16), through the adhesive layer (14) and strikes the substrate (11) or source image (12) on the document (10), and is reflected (18) andscattered (20). Alternatively, the laminate (13) can comprise a plain or clear layer of polyester without microspheres over the adhesivelayer (14). Light impinging on the laminate (13) passes through the polyester and laminate (14) to strike the substrate (11) or source image(12) where it is reflected and scattered. A first light source (24) directs light to the document (10). A second light source (26, 27) directslight towards a beam splitting mirror (23) which reflects the light to to the document (10). The light turning properties of the mirror (23)produce a light source which appears to an image receiver (40) as being returned from the surface of the document (10) at an angle of lessthan 1°. The image receiver (40) passes a signal via line (32) to a personal computer (41) which processes the received information. Suchprocessing is to establish whether the document (10) includes a retroreflective laminate, a plain polyester laminate, or neither. Additionally,further processing can establish whether the document (10) has been tampered with, altered, or forged.