Patent ID: 6661600
Filing Date: 2003-12-09
Classification: G11B

Abstract:
A method for calibrating servo index positions of a magnetic tape in a track following servo system, said magnetic tape having a plurality of parallel sets of linear servo edges, each said servo edge comprising an interface between two dissimilar recorded servo signals, each said set of servo edges comprising one of said servo edges on each of opposite lateral sides of a middle said recorded servo signal, at least a plurality of said servo index positions laterally offset from said linear servo edges, said track following servo system comprising at least one servo sensor of a tape head for sensing said recorded servo signals of said tape, a servo loop for positioning said tape head laterally with respect to said magnetic tape to track follow said sensed servo signals at specific position error signals representing displacements from said linear servo edges as determined from ratios of said sensed servo signals, and an independent position sensor to sense lateral position of said magnetic tape with respect to said tape head servo sensor, said method comprising:laterally positioning said at least one servo sensor to sense said servo signals at estimated ratios of said servo detector representing locations comprising said servo edges of at least a set of linear servo edges; determining independent position sensor lateral position of said tape head servo sensor with respect to said magnetic tape at said sensed servo edge locations; laterally repositioning said tape head servo sensor to a plurality of lateral positions of said tape head at predetermined displacements from said sensed servo edges as determined by said independent position sensor; track following said linear servo edges with said servo loop at each of said predetermined displacements; determining said ratio of said sensed servo signals at each of said predetermined displacements; and curve fitting a two dimensional, second order curve to said ratios of said sensed servo signals with respect to said predetermined displacements for each said linear servo edge to calibrate expected said position error signals for said servo loop at said laterally offset servo index positions with respect to said sensed servo edges of said set of linear servo edges.