New tracking method for two-beam optical heads using continuously grooved disks

A new composite tracking method suitable for a two-beam split-type optical head is suggested. Using twin spot and push-pull tracking method, and with ana auxiliary actuator combined, this method is designed so as to be applied, in particular, to optical disks having continuous grooves. In this method, a read-out spot is controlled by the twin-spot method, and moreover an auxiliary actuator for write spot positioning is driven by a differential signal of two push-pull tracking error signals derived from read-out and write beams. To examine tracking performance of this method, we constructed a two-beam optical head and successfully confirmed that the two spots could be easily positioned on the same track center independent of +/- 100 micrometers objective lens shift.