Methods and apparatus for rendering an optically encoded medium unreadable and tamper-resistant

Abstract

Methods and apparatus are provided for making an optically readable media unreadable and tamper-resistant. A method is disclosed for making an optically readable media unreadable, as is a media that operates in accordance with the method. The method has steps of (a) providing the media with a readout surface layer that is non-flat (i.e., textured in some way, such as by embossing, scratching, depositing a non-planar layer or regions, such as droplets) and that inhibits optical readout of the media; (b) applying a coating layer to the non-flat surface layer to smooth the non-flat surface and to enable optical readout of the media; and, after an initiation of a readout period, (c) removing the coating layer so as to expose the non-flat readout surface layer, thereby inhibiting optical readout of the media. Preferably, the coating layer is substantially index matched to the readout surface layer. In one embodiment the step of removing includes a step of evaporating at least one component material of the coating layer, while in another embodiment the step of removing includes a step of subliming at least one component material of the coating layer. A method is also disclosed for discouraging tampering with a readout-limiting mechanism of an optically readable media, as is a media that is constructed so as to operate in accordance with the method. In this embodiment the method has steps of: (a) providing the media with at least one layer that embodies the readout-limiting mechanism; (b) providing a textured surface that forms part of a layer that underlies the at least one layer, where the textured surface inhibits optical readout of the media; and (c) applying a coating layer over the textured surface to smooth the textured surface and to enable optical readout of the media, wherein removal of the coating layer exposes the textured surface thereby inhibiting optical readout of the media. The disk can be packaged in a sealed container with a source of an agent that inhibits transport of a volatile species from the color forming layer or from a layer that sublimates, wherein the onset of the limited play period coincides with the opening of the container.

1 . A method for making an optically readable media unreadable, comprising steps of: 
 providing the media with a readout surface layer that is non-flat and that inhibits optical readout of the media;    applying a coating layer to the non-flat surface layer to smooth the non-flat surface and to enable optical readout of the media; and    after an initiation of a readout period, reducing the thickness of the coating layer so as to expose the non-flat readout surface layer, thereby inhibiting optical readout of the media.    
     
     
         2 . A method as in  claim 1 , wherein the coating layer is substantially index matched to the readout surface layer.  
     
     
         3 . A method as in  claim 1 , wherein the step of reducing the thickness comprises a step of evaporating at least one component material of the coating layer.  
     
     
         4 . A method as in  claim 1 , wherein the step of reducing the thickness comprises a step of subliming at least one component material of the coating layer.  
     
     
         5 . A method for discouraging tampering with a readout-limiting mechanism of an optically readable media, comprising steps of: 
 providing the media with at least one layer that embodies the readout-limiting mechanism;    providing a textured surface that comprises a layer that underlies said at least one layer, said textured surface inhibiting optical readout of the media; and    applying a coating layer over said textured surface to smooth the textured surface and to enable optical readout of the media, wherein removal of the coating layer exposes the textured surface thereby inhibiting optical readout of the media.    
     
     
         6 . A method as in  claim 5 , wherein the readout-limiting mechanism comprises a layer that changes from an optically transparent state to a state that inhibits successful readout of data structures located on the media.  
     
     
         7 . A method as in  claim 5 , wherein the readout-limiting mechanism comprises said coating layer.  
     
     
         8 . A method as in  claim 5 , wherein the readout-limiting mechanism comprises said coating layer, and changes from an optically transparent state to a state that inhibits successful readout of data structures located on the media.  
     
     
         9 . A method as in  claim 5 , wherein the readout-limiting mechanism comprises a layer that changes from a first state that enables successful readout of data structures located on the media to a second state that inhibits successful readout of data structures located on the media.  
     
     
         10 . A method as in  claim 9 , wherein said change to said second state is induced by an increase in optical absorption.  
     
     
         11 . A method as in  claim 9 , wherein said change to said second state is induced by an increase in mechanical stress.  
     
     
         12 . A method as in  claim 9 , wherein said change to said second state is induced by an increase in optical noise or wavefront aberration created by scattering.  
     
     
         13 . A method as in  claim 9 , wherein said change to said second state is induced by evaporation of a volatile compound.  
     
     
         14 . A method as in  claim 9 , wherein said change to said second state is induced by sublimation of a volatile compound.  
     
     
         15 . A method as in  claim 5 , wherein the coating layer is substantially index matched to the textured surface layer.  
     
     
         16 . A method for making an optically readable media unreadable, comprising steps of: 
 providing the media with a first layer having a textured surface that would inhibit successful readout of the optically readable media;    coating the textured surface with a second layer that is comprised of a volatile component;    removing at least some of said volatile component for causing an increase in at least one of photoabsorption or scattering or surface roughness; wherein    an attempt to remove the second layer results in exposure of the textured surface, thereby inhibiting successful readout of the optically readable media.    
     
     
         17 . A method as in  claim 16 , wherein the step of removing at least some of the volatile component occurs through a barrier layer.  
     
     
         18 . A method as in  claim 16 , wherein the step of removing at least some of the volatile component occurs after a step of removing a barrier layer.  
     
     
         19 . A method as in  claim 16 , wherein the step of removing at least some of the volatile component occurs after a step of removing the media from a package that contains the volatile compound.  
     
     
         20 . A method for making an optically readable media unreadable, comprising steps of: 
 providing the media with a first layer having a textured surface that would inhibit successful readout of the optically readable media;    coating the textured surface with a second layer that is comprised of a volatile component; and    during a media play enablement period removing at least some of volatile component for reducing at least a thickness of the second layer; and    terminating the media play enablement period when the thickness of the second layer is reduced to a point that an exposure of the textured surface occurs, thereby inhibiting successful readout of the optically readable media.    
     
     
         21 . A method as in  claim 20 , wherein the step of removing at least some of the volatile component occurs through a barrier layer, and where the barrier layer has a thickness that is predetermined for controlling a rate of transport of the volatile component through the barrier layer.  
     
     
         22 . A method as in  claim 20 , wherein the step of removing at least some of the volatile component occurs after a step of removing a barrier layer.  
     
     
         23 . A method as in  claim 20 , wherein the step of removing at least some of the volatile component occurs after a step of removing the media from a package that contains the volatile compound.  
     
     
         24 . An optically readable media, comprising: 
 a region that encodes information that is optically readable by a reading device;    an overlying readout surface layer that is non-flat and that would inhibit the readout device from reading the information; and    a coating layer over said non-flat surface layer for smoothing the non-flat surface and enabling the readout device to read the information; wherein    said coating layer is responsive to an initiation of a readout period for being reduced in thickness so as to expose at least a portion of the non-flat readout surface layer, thereby inhibiting the readout device from reading the information.    
     
     
         25 . A media as in  claim 28 , wherein the coating layer is substantially index matched to the readout surface layer.  
     
     
         26 . A media as in  claim 28 , wherein said coating layer is comprised of a volatile compound and is reduced in thickness by evaporation or sublimation of said volatile compound.  
     
     
         27 . An optically readable media, comprising: 
 a region that encodes information that is optically readable by a reading device;    a transparent layer having a textured surface that overlies said region, said textured surface inhibiting optical readout of the media by the reading device; and    a readout-limiting layer that overlies said textured surface, said read-out limiting layer smoothing said textured surface and enabling, for the duration of a readout period, optical readout of the media by the readout device, wherein removal of the readout-limiting coating layer exposes said textured surface thereby inhibiting optical readout of the media by the readout device.    
     
     
         28 . A media as in  claim 31 , wherein the readout-limiting comprises material that changes from an optically transparent state to a state that inhibits successful readout of the surface region of the media.  
     
     
         29 . A media as in  claim 31 , wherein the readout-limiting layer comprises material that changes from a first state that enables successful readout of data structures located on the surface region of the media to a second state that inhibits successful readout of the data structures located on the surface region of the media.  
     
     
         30 . A media as in  claim 33 , wherein said change to said second state is induced by an increase in optical absorption.  
     
     
         31 . A media as in  claim 33 , wherein said change to said second state is induced by an increase in mechanical stress.  
     
     
         32 . A media as in  claim 33 , wherein said change to said second state is induced by an increase in optical scattering.  
     
     
         33 . A media as in  claim 33 , wherein said change to said second state is induced by evaporation or sublimation of a volatile compound.  
     
     
         34 . A media as in  claim 31 , wherein said readout-limiting layer is substantially index matched to said transparent layer.  
     
     
         35 . A media as in  claim 31 , wherein at least one layer is comprised of a volatile substance, and further comprising a barrier layer for isolating said at least one layer from a surrounding medium.  
     
     
         36 . A media as in  claim 31 , wherein at least one layer is comprised of a volatile substance, and further comprising a peel-off barrier layer for isolating said at least one layer from a surrounding medium at least until it is desired to use the media in the readout device.  
     
     
         37 . An optically readable disk, comprising: 
 a readout surface through which a readout device is able to read information;    a plurality of three dimensional features disposed on said readout surface, said features inhibiting optical readout of said disk by the reading device;    a color forming layer disposed over said readout surface and at least partially covering said features; and    an outer layer disposed over said color forming layer, wherein said features are completely covered by said color forming layer and said outer layer, and wherein the presence of said color forming layer and said outer layer enables optical readout of said disk by the reading device.    
     
     
         38 . An optically readable disk as in  claim 44 , wherein said color forming layer comprises a volatile compound that enters a surrounding medium via a transport mechanism driven by a concentration gradient between said color forming layer and the surrounding medium.  
     
     
         39 . An optically readable disk as in  claim 45 , wherein a thickness of said outer layer is selected at least in part on a desired amount of time that said disk is to remain in a readable condition after the initiation of said transport mechanism.  
     
     
         40 . An optically readable disk as in  claim 44 , wherein said disk comprises an optically detectable taggant compound.  
     
     
         41 . An optically readable disk as in  claim 44 , wherein said color forming layer exhibits an absorption maximum corresponding to one readout wavelength.  
     
     
         42 . An optically readable disk as in  claim 44 , wherein said color forming layer exhibits a plurality of absorption maximum corresponding to a plurality of readout wavelengths.  
     
     
         43 . An optically readable disk as in  claim 44 , wherein removal of all or a portion of a thickness of said color forming layer exposes at least some of said three dimensional features for subsequently inhibiting optical readout of the disk by the reading device.  
     
     
         44 . An optically readable disk as in  claim 45 , wherein said disk is sealed in a container with a source of said volatile compound.  
     
     
         45 . An optically readable disk as in  claim 45 , wherein said disk further comprises a peel-off barrier layer to prevent transport of said volatile compound through said outer layer.  
     
     
         46 . An optically readable disk as in  claim 44 , wherein said color forming layer comprises at least one chromophore that bias said color forming layer so as to reduce an amount of time required for said color forming layer to transition from a state where said disk is readable to a state where said disk is unreadable.  
     
     
         47 . A method of fabricating a limited play optically readable disk, comprising steps of: 
 providing a disk having a readout surface through which a readout device is able to read information;    forming a plurality of three dimensional features at said readout surface, said features inhibiting optical readout of said disk by the reading device;    forming a color forming layer disposed over said readout surface and at least partially covering said features; and    forming an outer layer disposed over said color forming layer, wherein said features are completely covered by said color forming layer and said outer layer, and wherein the presence of said color forming layer and said outer layer enables optical readout of said disk by the reading device.    
     
     
         48 . A method for setting a duration of a limited play period of an optically readable disk, comprising steps of: constructing the disk to include at least one limited play region comprised of a volatile compound, the limited play region operating by volatile compound transport driven by a concentration gradient between the region and a surrounding medium; and 
 adjusting the duration of the limited play period by setting a thickness of a transport barrier layer that overlies the region.    
     
     
         49 . A method as in claim  55 , wherein the step of adjusting comprises a further step of adding a bias chromophore in combination with a color forming layer in the limited play region.