| 摘要 |
<p>PURPOSE:To detect completely the control abnormality of a tracking control means from a fact that the prescribed one of two types of frequency components related to the differential frequency between pilot signals of two continuous adjacent tracks is detected from the output of a mixing means. CONSTITUTION:Reference signals have frequencies f1, f4, f3 and f2 while a rotary head is tracking the control target tracks of frequencies f1-f4 recorded in a control pull-in state. Then a 2fH component is produced when the tracks where frequencies f2 are f4 are recorded are traced. While the reference signals have frequencies f3, f2, f1 and f4 while the head is tracing the tracks where frequencies f1-f4 are recorded and if the head is tracing the position shifted from the control target track 2 by-track pitches. Then a 4fH component is produced when the tracks where frequencies f1 and f3 are recorded are traces. Thus the 2fH component is produced when a tracking error is less than 1-track pitch; while the 4fH component is produced when the tracking error exceeds 1 the track pitch respectively.</p> |
