| 摘要 |
An objective optical system for optical recording media and an optical pickup device using the objective optical system includes a holographic optical element that includes angularly-multiplexed holograms for correcting spherical aberration and/or coma aberration due to variations in substrate thicknesses of recording media and errors by tilting the holographic optical element out of the plane perpendicular to the optical axis by specified amounts. A control system determines the spherical aberration and/or coma using a control unit and outputs command signals for controlling the amount of tilt. The angularly-multiplexed holograms may change an input substantially collimated light beam to a divergent or convergent light beam except when the substrate of the optical recording media has a specified thickness. Additionally, the holographic optical element may include wavelength-multiplexed holograms to correct for chromatic aberration due to mode hopping of a semiconductor laser light source.
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