| 摘要 |
<P>PROBLEM TO BE SOLVED: To form a suitable light condensing spot for every optical disk to be used considering the influence of double refraction in a cover layer of the optical disk different for every specification of an optical pickup. <P>SOLUTION: A liquid crystal device disposed in an optical path has liquid crystal layers (a first liquid crystal layer and a second liquid crystal layer), alignment layers (alignment layers 23a/23b and alignment layers 33a/33b) and a voltage applying means. An alignment direction of the alignment layer is set symmetrically about an optical axis of light with which the optical disk is irradiated. Since the voltage applying means applies voltage to the liquid crystal layer to control the refractive index of the liquid crystal layer, a method for compensating disorder of a polarization state by double refraction in the cover layer of the optical disk can be easily changed according to the specification (e.g. a usage wavelength, thickness of the cover layer, a numerical aperture of an objective lens, etc.) of the optical pickup. Thereby, the suitable light condensing spot can be formed for every optical disk to be used. <P>COPYRIGHT: (C)2007,JPO&INPIT |
