Optical pickup device and optical disc apparatus

An optical pickup device comprising:

• a laser diode which emits laser light;
• an objective lens which irradiates an optical beam emitted from the laser diode on an optical disc;
• a grating which branches an optical beam;
• and
• one photodetector having a plurality of light receiving parts which detects an optical beam reflected by an information recording layer on the optical disc,
• wherein the photodetector has one light receiving part which detects a reproduction signal, and generates a signal for controlling a servo signal from all the light receiving parts except the light receiving part for detecting a reproduction signal.

An optical pickup device comprising:

• a laser diode which emits laser light;
• an objective lens which irradiates an optical beam emitted from the laser diode on an optical disc;
• an actuator which displaces the objective lens in a radius direction of the optical disc;
• a grating which branches an optical beam reflected by an information recording layer on the optical disc into a plurality of regions;
• and
• one photodetector having a plurality of light receiving parts which receives optical beams branched by the plurality of regions on the grating, wherein:
• the photodetector has a first light receiving part which detects zero-th order grating diffracted light of the grating and a plurality of second light receiving parts which detects grating diffracted light having an order more than or equal to that of ±first order grating diffracted light;
• a detected signal of the zero-th order grating diffracted light of the grating is defined as a reproduction signal;
• and
• a detected signal of the grating diffracted light having an order more than or equal to that of the ±first order grating diffracted light is defined as a signal for servo controlling.