Rotation controlling apparatus for optical recording medium

An apparatus for controlling the rotation speed of an optical recording medium having a track with wobbling, comprising:

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