US Patent 7339870 Optical disk apparatus and data reproducing method

When the data is reproduced by irradiating a laser beam onto the optical disk, an amount-of-irradiation-beam detection signal is produced according to the amount of the laser beam irradiated onto the optical disk, and the defect on the optical disk is detected on the basis of this amount-of-irradiation-beam detection signal. In addition, when the data is reproduced by irradiating the laser beam onto the optical disk, the amount-of-irradiation-beam detection signal is produced according to the amount of the laser beam irradiated onto the optical disk, an amount-of-reflected-beam detection signal is produced in accordance with the amount of the laser beam reflected from the optical disk, and the defect on the optical disk is detected on the basis of the amount-of-irradiation-beam detection signal and the amount-of-reflected-beam detection signal. Even when the optical disk has a defect, the laser beam is continuously irradiated onto the optical disk.