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 source image (12) such as a photograph, printed matter, or a bar code arranged on a substrate (11). Light impinging on the document (10) is split by 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) and scattered (20). Alternatively, the laminate (13) can comprise a plain or clear layer of polyester without microspheres over the adhesive layer (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) directs light towards a beam splitting mirror (23) which reflects the light 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 less than 1°. The image receiver (40) passes a signal via line (32) to a personal computer (41) which processes the received information. Such processing 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.