| 摘要 |
PURPOSE: An optical pickup device is provided to eliminate the offset unit of a tracking error signal generated by the uneven depth of a pit or the movement of a substance lens from an optical axis center. CONSTITUTION: Optical beams generated in laser diodes(41,42) are inputted to an optical system in a P wave or an S wave. If the incidence beam is the P wave, the beam is concentrated in a disk(100) by a substance lens(46) while vibrating for the pits arranged toward a tangential direction. If the incidence beam is the S wave, the beam is concentrated in the disk by the substance lens while vibrating for the radial direction of the pits. Therefore, the beam spot having direction to the pits is changed while rotating the shape of the beam spot formed on a four-division optical detector(49) according to the defocus between the disk and the substance lens. And the direction of astigmatism is adjusted to the direction of polarized light for the beam spot shape on the four-division optical detector to maintain a symmetrical shaped to the pits. Therefore, a direct current offset included in a tracking error signal is eliminated. |
