Patent ID: 7006411

Claim:
An optical pickup unit performing recording or reproducing information by making a light beam emitted from a light source incident on an information recording medium, the optical pickup unit comprising: an electro-optical element switching values of transmittance of a given region through which the light beam passes depending on whether the information is recorded or reproduced, and wherein said electro-optical element is provided subsequent to the light source in an optical path between the light source and the information recording medium; and the transmittance of the given region of said electro-optical element is controlled to a first value at a time of reproducing the information from the information recording medium and to a second value at a time of recording the information on the information recording medium, the first value being smaller than the second value, and the electro-optical element further comprising an outer region provided outside the given region so that the light beam passing through the outer region has a phase difference thereof selectively varied in the outer region, wherein the outer region includes a transparent electrode divided into a plurality of parts; and the phase difference of the light beam passing through the outer region is selectively varied therein by controlling voltages applied to the divided parts so as to vary refractive indices thereof.