| 摘要 |
<p>PROBLEM TO BE SOLVED: To satisfactorily detect the helical scanning scratch of a still scratch, etc., on a tape shaped recording medium. SOLUTION: A reflected light to be reflected from a magnetic tape is detected by a line sensor 7 arranged while its scanning direction is made to coincide with the width direction of the magnetic tape running at a fixed speed in accordance with an irradiating light to be irradiated on the magnetic tape. An output signal D0 by the present scanning of the sensor 7 is obtained from an A/D converter 8. Moreover, output signals D-1 , D-2 by one scanning before and two scannings before of the sensor 7 which are respectively shifted by a predicted moving amount to the width direction of the magnetic tape of the still scratch with respect to the present scanning of the sensor 7 are obtained from a line memories 9, 10 to respective signals D0 . Whether a scratch is present on the magnetic tape or not is detected from the output signal D0 by the present scanning of the sensor 7 in a scratch detector 11. Whether a correlation is present in between the signal D0 and signals D-1 , D-2 or not is detected in correlation detectors 12, 13. Fundamentally, the scratch is detected by a detector 11 and also it is judged that the still scratch is present by detecting that the correlation is present in detectors 12, 13.</p> |
