Patent ID: 8081543

Claim:
An optical disc apparatus that reads or writes an information signal by irradiating an optical disc having a plurality of recording layers with laser light, the optical disc apparatus comprising: a disc motor that rotates the optical disc; an optical pickup that includes a laser light source which generates laser light, an objective lens which irradiates the optical disc with laser light, an optical detector which detects light reflected from the optical disc, and a focus actuator which moves the objective lens vertically in relation to a surface of the optical disc; a signal processing section that generates a focus error signal based on a conventional astigmatism detection (CAD) system and a focus error signal based on a differential astigmatism detection (DAD) system from a detection signal generated by the optical detector; a servo section that provides focus control by giving a focus drive signal to the focus actuator, the servo section including: a focus lump control section, that inputs the focus error signal based on the CAD system, and generates and outputs a focus drive signal, a focus servo control section, that inputs the focus error signal based on the DAD system, and generates and outputs a focus drive signal, and a selector switch, that selects either an output from the focus jump control section or an output from the focus servo control section in accordance with an operation mode; wherein the servo section concurrently inputs the focus error signal based on the CAD system and the focus error signal based on the DAD system from the signal processing section; wherein, when a focus jump is to be performed from one recording layer of the optical disc to another recording layer, the servo section uses a focus drive signal that is generated from the focus error signal based on the CAD system; and wherein, when information is to be written into or read from one recording layer, the servo section uses a focus drive signal that is generated from the focus error signal based on the DAD system.