Patent ID: 8164999

Claim:
An optical disc device comprising: a laser diode configured to irradiate an optical disc having a layer L 0 and a layer L 1 ; a photodetection section configured to detect laser light reflected by the optical disc, which comprising a pair of sub-photodetectors and a main photodetector provided between the pair of sub-photodetectors; a focus error signal generation circuit configured to generate a focus error signal from a photodetection signal output by the main photodetector; a tracking error signal generation circuit configured to generate a tracking error signal based on the photodetection signal output by the main photodetector and photodetection signals output by the pair of sub-photodetectors; and a layer determination signal processing circuit configured to generate a layer determination signal from the photodetection signals output by the pair of sub-photodetectors and to determine in which of the layers a focus of the laser light is located on the basis of the layer determination signal and focus error signal, wherein the layer determination signal processing circuit is configured to determine that the focus is present in the layer L 0 when the focus error signal corresponds to a first just focus point and the layer determination signal is positive, and to determine that the focus is present in the layer L 1 when the focus error signal corresponds to a second just focus point and the layer determination signal is negative.