HEAD POSITIONING SERVO SYSTEM FOR OPTICAL RECORDING

摘要

An optical recording system has a system optical apparatus carried by a fine tracking system which moves the optical apparatus for small track seeking movements and for truck following. The fine tracking system is carried by a linear actuator coarse tracking system which makes large track seeking movements so that the entire area of the optical recording media is available to the system. Both the coarse tracking system and the fine tracking system are operated by servo control loops. The fine tracking system responds to tracking status signals with respect to track following and track seeking signals in response to track addressing information. The coarse tracking system responds to position sensor signals derived from a position sensor which is associated with the fine tracking system and provides signals related to the relative position of the fine tracking system to the coarse tracking system. The coarse tracking system follows the movements of the fine tracking system using signals from the position sensing system as the only necessary control for the coarse tracking system.