OPTICAL PICKUP, OPTICAL DISC DEVICE, POLARIZATION ADJUSTMENT PLATE, AND OPTICAL DEVICE

摘要

The present invention can simplify the configuration of a polarization adjustment plate. According to the present invention, the crystal axis of the polarization adjustment wavelength plate 32 is so arranged as to be turned up from the X-Y plane being an orthogonal plane with respect to the optical axis 40 a, and the wavelength dependence which the crystal material is originally provided with is largely expressed, and further the thickness "ta" with respect to the optical axis 40 a is set up such that the phase difference Delta to be brought about at the beam center becomes low from 360°+180°=540° being a desired design value to irradiate the optical beam as the P-polarization by a predetermined difference value or 60°.