Optical information recording/ reproducing device and optical information recording/ reproducing method

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 crstal 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:
• to apply a first effective voltage to said first region;
• to apply a second effective voltage to said second and sixth regions;
• to apply a third effective voltage to said third and seventh regions;
• to apply a fourth effective voltage to said fourth and eighth regions;
• and
• to apply a fifth effective voltage to said fifth and ninth regions;
• and
• 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 V1, said second effective voltage is V1+Vα, said third effective voltage is V1+Vβ, said fourth effective voltage is V1-Vα, and said fifth effective voltage is V1-Vβ, where V1 is a first reference voltage value, Vα is a first voltage value, and Vβis a second voltage value;
• and.
• wherein the predetermined values of Vα and Vβ are not zero.

An optical information recording/reproducing method comprising:

• driving a liquid crystal optical element disposed in an optical path of forward light within an optical head, provided with a liquid crystal polymer layer extending perpendicularly to an optical axis and including a first pattern electrode positioned on one side of said liquid crystal polymer layer in said optical axis direction;
• generating a reproduced signal based on backward light reflected by an optical recording medium;
• and
• controlling drive of said liquid crystal optical element in said driving so that a quality evaluation index of said reproduced signal is best improved,
• 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 driving step includes:
• applying an effective voltage of V1 to said first region,
• applying an effective voltage of V1+Vα+Vβ to said second and sixth regions;
• applying an effective voltage of V1−Vα+Vβ to said third and seventh regions;
• applying an effective voltage of V1−Vα−Vβ to said fourth and eighth regions;
• and
• applying an effective voltage of V1+Vα−Vβ to said fifth and ninth regions, where V1 is a first reference voltage value, Vα is a first voltage value, and Vβ is a second voltage;
• 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.