| 摘要 |
An apparatus efficiently compensates a focus error signal detected by a focus error detector in an optical disk system using an improved focus error compensation scheme. At an optical head, light reflected from a data recording surface of an optical disk is received, wherein the light from a light source is first focussed on the data recording surface of the optical disk before it is reflected therefrom, and converted into an electrical signal. At the focus error detector, the focus error (FE) signal is detected from the electrical signal. Next, at a controller, a regenerative information (RF) signal from the optical head is received and a selection signal is derived based on both a magnitude of the FE signal and a power level of the RF signal. Finally, at a filtering unit, in response to the selection signal, for selecting one of N predetermined filtering units, one of them having a very small cutoff frequency and the remainder of the filtering units having predetermined different phase-crossover frequencies, respectively, and filtering the FE signal by using the selected filtering unit to issue a filtered signal to the optical head as a compensated signal, thereby controlling focussing of the light along an optical axis formed by a center point of the light source and a convergence point of the light on the data recording surface of the optical disk, wherein N is a positive integer larger than 1.
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