Patent ID: 7079475

Claim:
An apparatus for detecting pre-pit information, comprising: an optical pickup configured to irradiate a light beam onto an optical-information recording medium having guiding grooves to be an information-recording track and pre-pits preset in between the guiding grooves; an optical-detecting section configured to optically detect said light beam reflected at said optical-information recording medium, having at least two optical-detecting regions divided across said track; a difference-detecting circuit configured to detect a difference between respective signals output from said two optical-detecting regions of the optical-detecting section; a first peak-value detecting circuit configured to detect and output a peak value of a signal output from the difference-detecting circuit; a filtering circuit configured to extract a signal based on wobble of said guiding grooves from the signal output at said difference-detecting circuit; a second peak-value detecting circuit configured to detect and output a peak value of a signal output from the filtering circuit; a differential potential-dividing circuit configured to divide at a predetermined proportion and output a difference between the output value of said first peak-value detecting circuit and the output value of said second peak-value detecting circuit; and a comparator configured to compare the output of said difference-detecting circuit and the output of said differential potentially-dividing circuit so as to output information regarding said pre-pits, wherein at least one of said first peak-value detecting circuit and said second peak value detecting circuit is made of a maximum-amplitude holding circuit for holding a maximum-amplitude voltage and includes a drop-rate selecting section for selecting multiple setting values as drop rates of the holding voltage.