Methods and apparatus for rendering an optically encoded medium unreadable by deforming the medium that is responsive to a read out beam

摘要

Methods and apparatus are provided for making an optically readable media (20) unreadable. The method includes steps of (a) providing the media (20) with an optically activated mechanism that degrades the reflectivity of a surface wherein information is encoded; (b) exposing the media (20) to optical radiation for reading out the information; and, during the step of exposing, (c) initiating the operation of the optically activated mechanism. In a further aspect the optically activated mechanism causes a defocusing of a readout beam, thereby degrading reflection of the readout beam from a surface wherein information is encoded. In another embodiment the method deforms a surface of the layer resulting in readout beam aberration or in an inability to correctly stay on track. In another embodiment a portion of the surface is removed to the atmosphere, such as by evaporation or sublimation.