| 摘要 |
PURPOSE:To correctly detect a tracking error signal amount through the use of both a signal detected from elliptic bits and a signal from a groove in a 1/8 wavelength depth by disposing one or plural sets of elliptic bits so that they are previously arranged in the header area of a disk by shifting the right and left sides of the track. CONSTITUTION:In a low frequency area, the gain of a prewobbling tracking error signal 24 obtained from a set of elliptic bits 20 arrays by shifting the right and left sides of the track is set larger than a push-pull tracking error signal using the groove 15 in a 1/8 wavelength depth, while at the prescribed frequency it is added to a push-pull type error signal in an LPF after attenua tion. If the relationship between the frequency fe ensuring the same gain of the prewobbling error signal after passing through the LPF and the push-pull type error signal, a disk rotation speed fd and a number N in the header area during one rotation is selected as inequalities show, an offset component included in the push-pull tracking error signal can be suppressed, thereby carrying out an precise tracking.
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