| 摘要 |
PURPOSE:To enable a head to be moved at high speed without promoting the track recording density of a servo positioning signal by detecting a head speed from a track passing pulse at the time of moving the head at high speed. CONSTITUTION:A high speed detector 17 consists of a zero cross detector 18 for detecting the zero cross of a periodic position signal, a track passing pulse generator 19 for detecting the leading edge and falling edge of the zero cross pulse and an F/V converter 20 for converting the inverse number of the periodicity of the track passing pulse into voltage, and outputs a head speed signal at the time of its moving at high speed. In other words, the track passing pulse can be obtained by comparing the periodic position signal with the zero level. The position signal in this case is not used with necessity of such accuracy as to obtain the speed by differentiating it, etc., so that the sampling is allowable at a low rate. By this method, the frequency of the periodic position signal during the high speed movement of the head becomes higher by narrowing a space between the tracks and speeding up the access speed, so that the speed signal can hence be obtained with high accuracy by detecting the zero cross of the periodic position signal even if the sampling of the position signal per period is decreased in its number of times.
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