Patent ID: 8527226

Claim:
An apparatus for modulating an incident beam, comprising: at least one body comprising a composition that is non-transmissive with respect to said incident beam, said body being rotatable about an axis perpendicular to a surface of said body, said body having a first set of features and at least a second set of features on said surface, said first set of features comprising one or more transmissive features with respect to said incident beam along a first radial path at a first radial distance from said axis, and said second set of features comprising a plurality of data storage features along a second radial path at a second radial distance from said axis; and at least one reference sensor disposed over a first position along said second radial path, wherein said first and said second radial distances are different, wherein a number of said transmissive features and a number of said plurality of data storage features are relatively prime, wherein said first set of features modulate said incident beam when said body is rotating, and wherein said reference sensor is configured for generating a reference signal based on at least a portion of said plurality of data storage features traversing said first position when said body is rotating.