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 rewritable discs, detection error occurs due to disc radial tilt. We have developed a track center detection method in which the center of a track is accurately detected using the complementary allocated pit address (CAPA) of a digital versatile rewritable disc (DVD-RAM). The track center servo corrects the 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 level of the push-pull tracking error signal indicates the amount of disc radial tilt when the track center servo is in operation. The developed servo system was introduced in a 4.7-G byte DVD-RAM disc drive, and it has been confirmed that jitter deterioration during reproduction was reduced to 0.5% or lower in the range of +/-0.5 degree of disc radial tilt.