| 摘要 |
A header region evaluation circuit includes a difference signal detection unit that detects a difference signal proportional to a difference in amounts of received light from an optical disc, a high pass filter that switches a plurality of cutoff frequencies according to a passband control signal, removes a low frequency component from the difference signal, and generates a difference signal HPF output, a waveform shaping unit that generates a shaping signal to convert the difference signal HPF output into a pulse, and a physical header detection sequencer that generates a groove detection signal for evaluating whether the physical header region is either one of a groove and an inter-groove and generates a passband control signal for controlling the cutoff frequency to be reduced for a difference signal corresponding to at least a part of the physical header region. |
