Patent ID: 8254238

Claim:
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: 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; 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 pattern electrode further includes: a second set of eight partition regions which are provided outside said second to ninth regions and defined so as to divide a circumference into eight segments with respect to said optical axis, said second set of eight partition regions including tenth to seventeenth regions sequentially arranged, wherein said liquid crystal optical element drive unit is further configured: to apply a sixth effective voltage to said tenth and fourteenth regions; to apply a seventh effective voltage to said eleventh and fifteenth regions; to apply an eighth effective voltage to said twelfth and sixteenth regions; to apply a ninth effective voltage to said thirteenth and seventeenth regions; and wherein an average of said sixth and eighth effective voltages and an average of said seventh and ninth voltages are equal to said first effective voltage.