Optical disc device

An optical device for playing back data recorded on a disc-shaped recording medium on the basic of a played-back signal obtained by projecting a light beam onto said disc-shaped recording medium and receiving said light beam returned from said disc-shaped recording medium, comprising:

• a high-pass filter for suppressing a low frequency component of said played-back signal and outputting the resulting signal
• an adder for adding an output signal of said high-pass filter and a correction signal and outputting the resulting signal;
• a first comparator for binarizing an output signal of said adder and outputting the resulting signal;
• a low-pass filter, having a frequency characteristic complementary to the frequency characteristic of said high-pass filter, for suppressing a high frequency component of an output signal of said first collator to generate said correction signal;
• a second comparator for binarizing said output signal of said adder taking a slice level as a reference and outputting the resulting signal as played-back data;
• and
• a controlling circuit for varying one of said slice level and a direct current level of said output signal of said adder in such a manner that a duty ratio of said played-back data becomes a prescribed value.