Objective lens velocity control system for use in an optical data storage system

Abstract

An objective lens velocity control system for use in an optical data storage system. The optical data storage system includes an optical disk with servo tracks for storing data, an objective lens, and a tracking drive for driving the objective lens along the tracking axis in response to tracking drive signals. The tracking error detector is responsive to the objective lens and produces tracking error signals representative of the position of the objective lens along the tacking axis. The tracking error signal also defines measurement periods which are representative of an actual velocity of the objective lens. A velocity control is responsive to the tracking error detector and produces the tracking drive signals in a form tending to cause the objective lens to have a desired velocity. For each measurement period, the tracking control produces a first tracking drive signal during a first portion but for no longer than a time duration which is a function of the desired velocity. During the remaining second portion of the measurement period, the velocity control produces a second tracking drive signal. The first and second tracking drive signals (which have opposite effects on the velocity) together tend to cause the objective lens to decelerate during measurement periods when the actual velocity is greater than the desired velocity, and to accelerate during the measurement period when the actual velocity is less than the desired velocity.

Dependencies are inferred from the claim text.