Optical disk device and optical pickup device

An optical disc drive for irradiating a laser beam to an optical disc to record and/or reproduce information signals, comprising:

• a laser source which oscillates in multimode;
• a first phase difference plate;
• a plane-of-polarization preserving fiber;
• and
• a second phase difference plate;
• the laser beam of linear polarization irradiated from the laser source being changed to the laser beam of circular polarization or elliptical polarization by the first phase difference plate to be transmitted by the plane-of-polarization preserving fiber, and being changed to the laser beam of linear polarization by the second phase difference plate to be irradiated to the optical disc, and the returned laser beam of linear polarization from the optical disc being changed to the laser bean of circular polarization or elliptical polarization by the second phase difference plate to be transmitted by the plane-of-polarization preserving fiber, and being changed to the laser beam of linear polarization by the first phase difference plate.

An optical pickup, comprising:

• a laser source which oscillates in multimode;
• a condensing lens for condensing a laser beam irradiated from the laser source to irradiate the condensed laser beam to an optical disc, and condensing the returned laser beam from the optical disc;
• a beam detecting means for detecting the returned laser beam from the optical disc condensed by the condensing lens;
• a first plane-of-polarization preserving fiber;
• and
• a second plane-of-polarization preserving fiber;
• the first plane-of-polarization preserving fiber and the second plane-of-polarization preserving fiber forming an optical path for transmitting the laser beam irradiated from the laser source, variation of polarization state which arises due to the transmission of the laser beam by one of the plane-of-polarization preserving fibers being compensated by the other of the plane-of-polarization preserving fibers.

An optical pickup, comprising:

• a laser source which oscillates in multimode;
• a condensing lens for condensing a laser beam irradiated from the laser source to irradiate the condensed laser beam to an optical disc, and condensing the returned laser beam from the optical disc;
• a beam detecting means for detecting the returned laser beam from the optical disc condensed by the condensing lens;
• a first phase difference plate;
• a plane-of-polarization preserving fiber;
• and
• a second phase difference plate;
• the laser beam of linear polarization irradiated from the laser source being changed to the laser beam of circular polarization or elliptical polarization by the first phase difference plate to be transmitted by the plane-of-polarization preserving fiber, and being changed to the laser beam of linear polarization by the second phase difference plate to be irradiated to the optical disc via the condensing lens, and the returned laser beam of linear polarization from the optical disc being condensed by the condensing lens and changed to the laser beam of circular polarization or elliptical polarization by the second phase difference plate to be transmitted by the plane-of-polarization preserving fiber, and being changed to the laser beam of linear polarization by the first phase difference plate to be transmitted to the beam detecting means.