Labelling scheme and apparatus

Abstract

A method and system for writing a label (defined within a predetermined region of the sample 110 ), the label displaying a visible layout of light-modified regions in a predetermined spatial arrangement. The method comprises: modifying regions of a material within the label using light, wherein the modifying comprises using light of a first polarisation state to provide photo-induced optically active regions of a first type having a first optical activity state which is characteristic of having been formed by light of the first polarisation state, in order to encode covert information in the label using the locations of the first type of light-modified regions within the spatial arrangement of the label.

1 - 43 . (canceled) 
     
     
         44 . A method of reading a label within a sample, the label comprising a plurality of light-modified regions having a predetermined spatial arrangement therebetween, the modified regions comprising light-modified regions which can be of at least a first type having a first optical activity state characteristic of having been formed by light of a first polarisation state, the method comprising:
 illuminating the label with light of a predetermined polarisation state to reveal the locations of the first type of light-modified regions to read covert information encoded by their locations.   
     
     
         45 . The method as claimed in  claim 44 , wherein the light-modified regions can comprise light-modified regions of at least a second type having a second optical activity state characteristic of having been formed by light of a second polarisation state, the method comprising:
 illuminating the label with light of the predetermined polarisation state to reveal the locations the second type of light-modified regions to read covert information encoded by their locations.   
     
     
         46 . The method as claimed in  claim 45 , wherein the light-modified regions can comprise a third type of light-modified region having a third optical activity state characteristic of having been formed by light of a third polarisation state, the method comprising:
 illuminating the label with light of the predetermined polarisation state to reveal the locations the third type of laser modified regions to read covert information encoded by their locations.   
     
     
         47 . The method as claimed in  claim 46 , comprising:
 illuminating the label with light of a second polarisation state to reveal the locations of the second type of light-modified regions to read covert information encoded by their locations; and/or   illuminating the label with light of a third polarisation state to reveal the locations of the third type of light-modified regions to read covert information encoded by their locations.   
     
     
         48 . The method as claimed in  claim 45 , comprising:
 illuminating the label with light of a second polarisation state to reveal the locations of the second type of light-modified regions to read covert information encoded by their locations.   
     
     
         49 . The method as claimed in  claim 44 , comprising:
 alternately illuminating a light-modified region of the label with a pulse of light of a first polarisation state and a pulse of light of a second polarisation state;   timing detection of the illuminating light, for a first predetermined period, so as to detect only light of the first polarisation state;   timing detection of the illuminating light, for a second predetermined period, so as to detect only light of the second polarisation state; and   comparing signals detected in the first predetermined period and the second predetermined period to determine the type of the laser modified region.   
     
     
         50 . The method as claimed in  claim 45 , comprising:
 alternately illuminating a light-modified region of the label with a pulse of light of a first polarisation state and a pulse of light of a second polarisation state;   timing detection of the illuminating light, for a first predetermined period, so as to detect only light of the first polarisation state;   timing detection of the illuminating light, for a second predetermined period, so as to detect only light of the second polarisation state; and   comparing signals detected in the first predetermined period and the second predetermined period to determine the type of the laser modified region.   
     
     
         51 . The method as claimed in  claim 46 , comprising:
 alternately illuminating a light-modified region of the label with a pulse of light of a first polarisation state and a pulse of light of a second polarisation state;   timing detection of the illuminating light, for a first predetermined period, so as to detect only light of the first polarisation state;   timing detection of the illuminating light, for a second predetermined period, so as to detect only light of the second polarisation state; and   comparing signals detected in the first predetermined period and the second predetermined period to determine the type of the laser modified region.   
     
     
         52 . The method as claimed in  claim 47 , comprising:
 alternately illuminating a light-modified region of the label with a pulse of light of a first polarisation state and a pulse of light of a second polarisation state;   timing detection of the illuminating light, for a first predetermined period, so as to detect only light of the first polarisation state;   timing detection of the illuminating light, for a second predetermined period, so as to detect only light of the second polarisation state; and   comparing signals detected in the first predetermined period and the second predetermined period to determine the type of the laser modified region.   
     
     
         53 . A label reader apparatus for reading a label in a sample, the label displaying a visible layout of light-modified regions in a predetermined spatial arrangement, and comprising light-modified regions of a first type having a first optical activity state characteristic of having been formed by light of a first polarisation state, the apparatus comprising:
 an illumination device for illuminating the label in the sample;   a polarisation device for imparting one of a plurality of polarisation states to the illuminating light;   a detection device arranged to detect light from the illumination device; and   a processor configured to determine from the detected light locations of the first type of modified regions and read covert information encoded by their locations.   
     
     
         54 . The label reader apparatus as claimed in  claim 53 , wherein the illumination device is arranged to illuminate only part of the label at a time. 
     
     
         55 . The label reader apparatus as claimed in  claim 53 , wherein the illumination device is arranged to illuminate the whole label all at once. 
     
     
         56 . A system for writing a label and reading a label, comprising:
 a labelling system for writing a label within a sample of a material, the label comprising a visible layout of light-modified regions in a predetermined spatial arrangement, the labelling system comprising:
 a light source for modifying regions of the sample using light; and 
 a polarisation apparatus for imparting any one of a plurality of polarisation states to the light for modifying the regions of the sample; and 
   the label reader apparatus of  claim 53 .   
     
     
         57 . The system for writing a label and reading a label as claimed in  claim 56 , wherein the illumination device is arranged to illuminate only part of the label at a time. 
     
     
         58 . The system for writing a label and reading a label as claimed in  claim 56 , wherein the illumination device is arranged to illuminate the whole label all at once. 
     
     
         59 . A non-transitory computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to perform the method of  claim 44 .