| 摘要 |
PURPOSE:To stabilize the tracking control just after track jump by setting the time constant of a differentiation circuit part at the time of track jump so that the point where the polarity of the square wave signal applied to a light beam driving coil is inverted coincides with the zero-crossing point of a tracking error signal. CONSTITUTION:A differentiation circuit part 11 is provided in the preceding stage of a pulse generating means which converts the tracking error signal to a pulse signal for the purpose of detecting the zero-crossing point of the tracking error signal. At the time of track jump, the time constant of the differentiation circuit part 11 is so set that the point where the polarity of the square wave signal, which is generated based on the phase-advance tracking error signal and is applied to a light beam driving coil 8, is inverted coincides with the zero-crossing point of the tracking error signal. Consequently, the impulse sum of the square wave signal applied to the light beam driving coil 8 is zero when the light beam is on a second track after track jump. Thus, the tracking control is stabilized.
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