Patent ID: 6661750
Filing Date: 2003-12-09
Classification: G11B

Abstract:
An aberration detection device comprising:a radiation source for emitting a light beam; an object lens for focusing the light beam on an information carrier; a hologram for partitioning a returning light beam that has been reflected by the information carrier and passed through said object lens into a light beam passing a first region and a light beam passing a second region, and diffracting the light beam passing the first region away from said radiation source; and a plurality of light detectors for receiving a diffracted light beam passing through the first region; wherein said plurality of light detectors receives both a +1-order diffractive light beam and a âˆ’1-order diffractive light beam that have passed through the first region and been diffracted, said plurality of light detectors comprises a photo-detector partitioned into at least two portions, the photo-detector is arranged such that both the +1-order diffractive light beam and the âˆ’1-order diffractive light beam are irradiated onto a partition line of the at least two portions, and a spherical aberration, a coma aberration or an astigmatism is detected and identified individually from an output signal from the photo-detector.