A focus servo system with a focus close algorithm is disclosed. The focus close algorithm provides a bias control effort to the focus servo system when focus is closed. A method of closing focus includes positioning an optical pick-up unit at a first position away from an optical medium, moving the optical...http://www.google.com/patents/US7672199?utm_source=gb-gplus-sharePatent US7672199 - Close focus algorithm in a digital focus servo system
