| 摘要 |
The present invention aims to correct the spherical aberration and ensure the working distance and furthermore to obtain satisfactory recording and reproducing property by shaping the optical spot formed on the disc surface. A liquid crystal element for correcting spherical aberration includes diffraction electrodes for converting the light beam to a divergent light when reproducing a CD, and phase shift electrodes for providing a phase difference to the light beam when reproducing a BD. When reproducing a BD, voltage is applied to the diffraction electrodes as well as the phase shift electrodes to diverge the light beam and lower the light intensity of the central portion, thereby shaping the optical spot formed on the disc.
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