Security device for security document

摘要

A security device (1) for verifying an authenticity of a security document (100) comprises an at least partially transparent substrate (2) with a first surface (3) and a second surface (4). A first pattern (10) is arranged on the first surface (3). This first pattern (10) is derivable using a first seed pattern (10'). A second pattern (20) is arranged on said second surface (4). This second pattern (20) is derivable using the first seed pattern (10') and using a second seed pattern (20'). Transmittances and reflectivities of the first and second patterns (10, 20) are selected such that in a reflection viewing mode, only the first seed pattern (10') is visible. In a transmission viewing mode, however, only the second seed pattern (20') is visible.