Spin-coating compensation for an optical storage medium with a substrate groove profile gradient

When a dye material layer is spin-coated on an optical storage medium of the type having grooves fabricated in a substrate thereof, the dye material layer surface has depressions in the vicinity of the grooves. These depressions have a profile which is a function of the distance from the center of the storage medium. To compensate for the radial dependence of the depressions, the geometry of the grooves is changed by varying the base dimension of the groove as a function of the distance from the center of the storage medium. In this manner, the difference in phase for radiation traversing the storage medium by an optical path that includes a groove as compared to an optical path that does not include an associated groove is constant as a function of distance from the center of the storage medium. The phase difference which is a constant as a function of distance from the center of the storage medium is important in the generation of signals used in tracking the groove.