Substrate alignment detection using circumferentially extending timing pattern

An apparatus comprising a planar substrate comprising a circumferentially extending timing pattern that surrounds an interior area configured to receive at least one written feature, the timing pattern comprising spaced apart first and second timing marks disposed on opposing sides of a center point of the substrate and a substrate identification (ID) field disposed between the first and second timing marks at a selected radius that stores a unique substrate identifier value in a machine readable form configured to be decoded by a detector during rotation of the substrate about a central axis offset from the center point of the substrate.

An apparatus comprising:

• a support mechanism configured to support and rotate a substrate about a central axis;
• and
• a write assembly configured to apply a write beam to the substrate during rotation thereof about the central axis by the support mechanism to write a circumferentially extending timing pattern to the substrate, the circumferentially extending timing pattern comprising spaced apart first and second timing marks disposed on opposing sides of the central axis to define a center point of the timing pattern and an identification (ID) field between the first and second timing marks that stores a unique identifier value associated with the substrate.