| 摘要 |
PROBLEM TO BE SOLVED: To reproduce information recorded in a recording medium without any errors by controlling a timing for irradiating the recording medium with a recording light beam according to bits of first and second information and light beams intensity according the second information. SOLUTION: The LPF 50 of a pulse width modulation circuit 100 performs waveform shaping such that the rising and falling parts of an EFM modulated EFM signal have a predetermined tilt. A comparator 52 outputs, when a recording power changing signal is a given level, a signal having a pulse width wider by β/2 than the EFM signal as an output signal of the pulse width modulation circuit 100 to an optical modulator in the rising and falling parts, and shades or transmits lights according to the output signal of the pulse width modulation circuit 100. For a bit formed in a visible region, the length of a track direction is (L+β) and, by setting a βvalue to a proper level, a time during which a binary signal reproduced from this bit is 0 is set to T. |
