OPTICAL PICKUP AND OPTICAL DISC APPARATUS

摘要

An optical pick-up apparatus and an optical disc apparatus are provided to increase the intensity of a beam emitted from a light source and prevent the reduction of a light use efficiency derived from the production of a main beam and a sub-beam using diffraction grating. A light source irradiates an optical beam toward an optical disc. An objective lens condenses the optical beam onto a recording surface of the optical disc. A photodetector(127) receives an optical beam reflected from the recording surface and outputs a signal corresponding to the intensity of the received optical beam. The shape of a spot(180) of the received optical beam is asymmetric in both radial and tangential directions of the optical disc. A lens shaft signal of the objective lens is detected by a controller which controls the objective lens to follow the optical disc and the signal output from the photodetector(127).