Patent ID: 6236627
Filing Date: 2001-05-22
Classification: G11B

Abstract:
An optical medium, comprising:a multitude of sequential elongate tracks for storing information indicated by a multiple marked and unmarked track positions centered along the centerline of the tracks, the marks interacting with incident light to provide difference in light received from the marked and unmarked positions to form a read signal; anda servo field on each track for generating a tracking error signal from the read signal depending on marked positions that are not on the track, the servo field having multiple discrete positions centered on the centerline of the track in the same longitudinal positions along each track, the centered servo field positions including one marked position and at least two unmarked positions, the mark being in a different one of the centered servo field positions than the mark in the centered servo field position of each other track that is adjacent to the track, and the marked centered position in the servo field of each other track that is adjacent to the track is adjacent to an unmarked centered position in the servo field of the track so as to provide the tracking error signal.