Patent ID: 7643393

Claim:
A method for modifying an optical medium, the medium having a plurality of operational characteristics, each operational characteristic having a predefined limit, comprising: selecting a region of the medium to be modified; and modifying the medium in the region to have a first actual characteristic that is at or near a predefined limit of a first of the plurality of operational characteristics prior to a read operation of the medium; and modifying the medium in the region to have a second actual characteristic that is at or near a predefined limit of a second of the plurality of operational characteristics prior to a read operation of the medium; such that during a read operation of data stored in the modified region, the read operation is altered in the modified region as a result of the modifications such that the first and second actual characteristics of the modified medium cause a slow-down in the read operation when the modified region is read, the modified region maintaining its optical characteristics following irradiation of the modified region during the read operation, wherein the first of the plurality of operational characteristics is distortion size and wherein modifying the medium to have the first actual characteristic comprises modifying the medium to have a distortion of a size that is at or near the predefined limit of the operational characteristic for distortion size and wherein the size of the distortion is based on a first size of a physical deformation and a second size of a local corresponding region of increased birefringence.