Tracking system for optical record medium
Scanning beam control system
Apparatus for reading a disk-shaped record carrier Patent #: 4446545
ApplicationNo. 06/489770 filed on 04/29/1983
US Classes:369/30.22, Correction of error250/201.5, With optical storage medium; e.g., optical disc, etc.369/124.1, Gain processing369/30.12, Particular track portion369/44.32, Means to compensate for defect or abnormal condition369/44.36, Variable gain369/53.29, Transduced location indicating369/53.32, Dropout indicating386/49Using static memory or delay means
ExaminersPrimary: Richardson, Robert L.
Attorney, Agent or Firm
International ClassG11B 7/09 (20060101)
Foreign Application Priority Data1982-04-30 JP
AbstractA scanning servo system, that is, a focusing servo system or a tracking servo system, for an optical-disc information reproducing apparatus includes (a) a light source for generating a light beam to scan a selected track location on an optical-disc wherein the information is stored as a series of pits arranged in the form of the track; (b) an objective lens for applying a scanning spot of the light beam to the selected track location; (c) a transducer for converting an optical signal or an image of the pit into an electric signal; (d) an actuator for driving the objective lens in response to the electric signal in a direction vertical or radial to the optical-disc, thereby causing the scanning spot to scan the selected track location accurately, the actuator being variable in its response characteristics in response to the electric signal; (e) a circuit for detecting a dropout of the information on the selected track location and generating a responsive signal to the dropout of information; (f) a circuit for delaying the responsive signal to the dropout of information for one rotation period of the optical-disc; and (g) a circuit for lowering the response characteristics of the actuator in response to the responsive signal to the dropout of information through the delaying circuit.