Patent ID: 7428207

Claim:
An aberration correcting device which corrects an aberration occurring when one objective lens is employed for a plurality of optical recording media at least one of recording density and thickness of a cover layer of which is different from each other, comprising: a liquid crystal element disposed between the objective lens and a light source and controlled a refractive index thereof to be varied in accordance with an applied voltage; and a voltage applying portion for applying voltage to the liquid crystal element so that a wavefront of light penetrated through the liquid crystal element forms a penetrated wavefront having a predetermined phase distribution, wherein the voltage applying portion applies voltage so that a penetrated wavefront having a phase distribution for correcting only an aberration occurring in an area inside an effective diameter in recording or reproducing the optical recording medium is formed, wherein the voltage applying portion independently applies predetermined voltage to each of a plurality of electrodes arranged along the liquid crystal element to variably control a shape of the penetrated wavefront, in which the voltage applying portion applies predetermined voltage to a plurality of electrodes arranged in an area inside the effective diameter of the optical recording medium so that a penetrated wave having a shape corresponding to aberration occurring in the area is formed, and applies predetermined voltage to a plurality of electrodes arranged in an area outside the effective diameter of the optical recording medium so that a penetrated wave not having a shape corresponding to aberration occurring in the area is formed.