Patent ID: 7813253

Claim:
An optical disk reproducing device optical disk for reproducing information recorded on an optical disk, the device comprising: a gain controlling portion for setting a gain of an RF amplifier to a maximum range when the optical disk is discriminated during its activation, the RF amplifier amplifying an RF signal from an optical pickup that emits a laser beam toward the optical disk and receives reflected light so as to output the RF signal as a read signal; a binary process portion for performing a binary process on the RF signal from the RF amplifier in accordance with a predetermined binary process condition so as to output a binary signal indicating a detection of a disk unique signal contained in the RF signal; a binary process condition setting portion for setting a binary process condition for the binary process portion, the binary process condition being an upper threshold level and a lower threshold level corresponding to levels of upper and lower predetermined percentages of the maximum range in order to perform the binary process on the disk unique signal contained in the RF signal in accordance with whether or not the RF signal makes up the upper and lower predetermined percentages of the maximum range; a binary signal ratio calculating portion for calculating a binary signal ratio indicating a ratio of a time period of the binary signal to a time period corresponding to one rotation of the disk by measuring a time period of the binary signal from the binary process portion obtained by performing the binary process on a vacant part without a signal between the upper threshold level and the lower threshold level; and a disk discriminating portion for discriminating the optical disk in accordance with the calculated binary signal ratio.