OPTICALLY VARIABLE SECURITY DEVICE

摘要

A method of recording an optically variable security device. The method comprises exposing an object ( 3 ) to a coherent beam of diffuse light; causing the resultant light to interfere with a reference beam ( 5 ) and recording the resultant interference pattern on or in a record medium ( 4 ). An aperture mask ( 9 ) is located upstream or downstream of the object ( 3 ) with respect to the direction of the diffuse light beam such that different parts of the object are imaged on to respective different, non-overlapping parts of the record medium.