Error theory for laser etched disk standards

An electromagnetic model and a geometric model are proposed for readback errors caused by laser etching of a magnetic disk surface. These models enable calculation of expected extra pulse (drop-in) and missing pulse (drop-out) error counts for the design and analysis of error standards for magnetic disk testing. In most cases a geometric approach is adequate for the analysis of missing pulses but not for extra pulses. A practical formula is derived for the calculation of extra pulse amplitude ratios from laser etching, and the effect of demagnetization at the laser etch is estimated.