Optical reader with a limiter in the tracking or focus error servo control loop
AssigneeU.S. Philips Corporation
InventorRonaldus M. Aarts
Life of this patent
Estimating the term…
Abstract
Faults in servo control systems as a result of, for example, signal spikes caused by defects such as thickness variations, air bubbles, and scratches and dust particles on the substrate of the record carrier in an apparatus for reading an optical record carrier, can be suppressed effectively by arranging a limiter in the servo control system of such an apparatus. Suitably, the limiter has an adaptive nature, i.e. the limiting levels are adapted to the amplitude of the servo signal.
Claims5
An apparatus for reading an optical record carrier, which apparatus comprises an optical system for projecting a read beam so as to form a scanning spot on the record carrier, a read detector for detecting information contained in the read beam after it has cooperated with the record carrier, and a control circuit for controlling a control quantity which influences the scanning spot, which control circuit comprises means for generating an error signal, a servo control device for controlling the control quantity depending on said error signal, and a limiter which is arranged between the error signal generating means and the servo control device, for limiting peak-shaped spurious signals in the error signal, said limiter comprising at least one control input for adjusting the limiting level depending on a control signal on said control input, and an amplitude detector, coupled to said control input, for supplying the control signal in dependence on the amplitude of the error signal.
Dependencies are inferred from the claim text.