| Tracking system for optical record medium - Patent 4406000 (5258 words) |
 | The improvement as defined in claim 3, wherein the durations of the first and second control signals are at least as long as the normal duration of the record medium defects of the prescribed type. |
| The beam is reflected in accordance with the recorded information, and the intensity of this reflected beam is detected and suitably processed, to produce a tracking error signal representative of the deviation of the reading beam from the centerline of the selected track. |
| The apparatus compensates for the presence of particular defects in the record medium, by comparing a tracking error signal to a pair of prescribed thresholds that are selectively variable according to the type of defect encountered. |
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