Method and device for disc rotation control in an optical storage system based on detected extent of disc warping

A digital signal processing device adapted for use in an optical storage system for disc rotation control, the optical storage system being capable of generating a focusing error signal from light that was reflected by an optical disc loaded in the optical storage system, said digital signal processing device comprising:

• a low pass filter adapted for removing a high-frequency component of the focusing error signal to obtain a filtered signal;
• a direct current level remover coupled to said low pass filter for removing a direct current component of the filtered signal to obtain a warp-indicating signal;
• and
• a controller coupled to said direct current level remover for comparing the warp-indicating signal with a predetermined threshold value to determine extent of warping of the optical disc;
• said controller being adapted to control the optical storage system so as to limit maximum rotation speed of the optical disc according to result of the comparison made by said controller.