| 摘要 |
A focus offset setting portion gives a predetermined quantity of offset to a focus control quantity used to reduce a focus error signal to zero based on the focus error signal generated by a focus error generation portion, and outputs a result. An adaptive equalizer including an adaptive control portion and an FIR filter subjects a reproduction signal RF provided from an optical pickup to waveform equalization based on a signal decoded by a Viterbi decoder. A controller obtains an optimum point of a focus offset by using a tap coefficient of the adaptive equalizer, and changes a set value of a focus offset setting portion.
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