Patent ID: 6930962
Filing Date: 2005-08-16
Classification: B82Y,G11B

Abstract:
1. An optical information reading apparatus comprising: a semiconductor laser; a beam splitter adapted to split a laser beam emitted from the semiconductor laser and a reflected laser beam returning from a recording medium; a collimating lens adapted to change a diffusion angle of the laser beam; a super-resolution cut-off filter, the super-resolution cut-off filter adapted to separate the laser beam into a 0-th order laser beam and ± n-th order laser beam, the ± n-th order laser beams being utilized to perform a tracking control; an objective lens positioned immediately after the super-resolution cut-off filter, having a numerical aperture appropriate for reading information recorded on the recording medium, and adapted to converge the 0-th order laser beam and the ± n-th order laser beams generated by the super-resolution cut-off filter onto the recording medium; and a photodetector for detecting the reflected laser beam from the recording medium, wherein the super-resolution cut-off filter has on its central portion a reflecting means comprising an annular portion and a straight portion substantially corresponding to an inner diameter of the annular portion.