Patent ID: 7209415

Claim:
An optical pickup device for performing recording and/or reproduction of information by irradiating laser light onto a disk, the optical pickup device comprising: (a) an astigmatic lens for receiving and converging a split laser beam reflected from the disk; (b) a photodetector for receiving the converged beam from the astigmatic lens; (c) an objective lens drive actuator for receiving a focus servo signal generated from an electrical signal outputted from the photodetector and adjusting the laser beam in an on-focus state; (d) a lens designed to converge reflection light from the disk when a thickness of an intermediate layer, between a disk surface and a recording layer, is greater or smaller than an optimum value by a predetermined degree; (c) a photodetector that receives the reflection light converged by the lens (d) to output an electric signal, and when the thickness of the intermediate layer assumes the optimum value, receives a predetermined portion of the reflection light with reference to a total light quantity of the reflection light, wherein components (d) and (e) detect a spherical aberration when the laser light is in an on-focus state; and (f) a diffusion angle converter that changes a diffusion angle of the laser light traveling toward the disk in accordance with a servo signal generated from the electric signal outputted from the photodetector (e), wherein component (f) corrects the spherical aberration when the laser light is in an on-focus state.