Rotation controlling apparatus for optical recording medium

摘要

An rotation speed controlling apparatus of an optical recording medium having a wobbled track includes an optical pickup for irradiating a light beam to generate a reading signal according to a wobbling shape of the track; a filter having a predetermined frequency band to pass a wobble reference frequency therethrough for extracting a wobble signal from the reading signal; a generator for generating a wobble reference signal; a detector for detecting the difference between the wobble signal frequency and the wobble reference frequency; a controller for controlling the rotation speed on the basis of the difference between the frequency of the extracted wobble signal and the wobble reference frequency; and a discriminator for discriminating that the wobble signal frequency lies outside the frequency band of the filter; wherein the controller controls the rotation speed in accordance with the detected frequency difference when the wobble signal frequency lies outside the frequency band of the filter.