Track center servo and radial tilt servo system for a digital versatile rewritable disc (DVD-RAM)

In the push-pull tracking error signal, which is generally used for rewrita ble discs, detection error occurs due to disc radial tilt. We have develope d a track center detection method in which the center of a track is accurat ely detected using the complementary allocated pit address (CAPA) of a digi tal versatile rewritable disc (DVD-RAM). The track center servo corrects th e tracking deviation caused by the detection error. We have also developed a method for detecting the disc radial tilt based on the fact that the leve l of the push-pull tracking error signal indicates the amount of disc radia l tilt when the track center servo is in operation. The developed servo sys tem was introduced in a 4.7-G byte DVD-RAM disc drive, and it has been conf irmed that jitter deterioration during reproduction was reduced to 0.5% or lower in the range of +/-0.5 degree of disc radial tilt.