Patent ID: 8045442
Filing Date: 2011-10-25
Classification: G11B

Abstract:
1. An optical information recording/reproducing apparatus comprising: an optical head including: a light source; an objective lens focusing an emitted light emitted from said light source on an optical recording medium; a photo-detector receiving a reflected light generated by said emitted light being reflected by said optical recording medium; a light splitter splitting forward light directed from said light source to said objective lens and backward light directed from said objective lens to said photo-detector; and a liquid crystal optical element which is provided in a light path of said forward light and includes a liquid crystal polymer layer extending perpendicularly to an optical axis; and a liquid crystal optical element drive unit driving said liquid crystal optical element, wherein said liquid crystal optical element includes a first pattern electrode provided on one side of said liquid crystal polymer layer in said optical axis direction and divided into a plurality of regions, wherein said first pattern electrode includes: a first region provided to surround said optical axis, a set of eight partition regions provided outside said first region and defined so as to divide a circumference into eight segments with respect to said optical axis, said set of eight partition regions including second to ninth regions sequentially arranged, wherein said liquid crystal optical element drive unit is configured: wherein an average of said second and fourth effective voltages and an average of said third and fifth effective voltages are equal to said first effective voltage; wherein said first effective voltage is V wherein an optimum value of said voltage Vβ is determined with said voltage Vα fixed to a predetermined value so that a quality evaluation index of a reproduced signal from said optical recording medium is best improved, and an optimum value of said voltage Vα is determined with said voltage Vβ fixed to a predetermined value so that said quality evaluation index is best improved; and wherein the predetermined values of Vα and Vβ are not zero.