A phase-lock control circuit suitable for an optical disk apparatus of a sample-servo format scheme includes an injection-synchronized control loop in addition to a normal phase-lock loop control loop. The phase-lock loop control loop includes a phase-comparator, a low-pass filter, a voltage-controlled...http://www.google.com/patents/US5172357?utm_source=gb-gplus-sharePatent US5172357 - Phase-synchronous controller for production of reference clock signal in optical disk drive system
