| 摘要 |
An optical pickup device using hologram optical elements, the pickup device including a laser diode and, a hologram glass plate diffracting a laser beam emitted from the laser diode and dividing and condensing the laser beam reflected by an optical disc. The hologram glass plate is arranged at the front of the laser source while being spaced apart from the laser diode by a predetermined distance and is provided with four holograms. A collimator is arranged at the front of the hologram glass plate and changes the laser beam emitted from the laser source as well as the laser beam reflected by the optical disc into a parallel beam. An objective lens focuses the parallel laser beam from the collimator on the optical disc. A pair of focusing photo detectors and a pair of tracking photo detectors are also provided at the front of the laser diode and detect the laser beams diffracted and condensed by the holograms of the hologram glass plate in the form of data reading signals. In order to compensate a focusing error and a tracking error, an error compensating actuator is arranged at a side of the objective lens and moves the objective lens in accordance with error signals detected by the focusing and tracking photo detectors.
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