Patent ID: 6278682
Filing Date: 2001-08-21
Classification: B82Y,G11B

Abstract:
An optical disc drive for reading/writing data from/on an optical disc, comprising:a laser source that emits a parallel laser beam;an objective lens system that receives the laser beam emitted by said laser source and converges the laser beam on said optical disc;a deflection mirror provided between said laser source and said objective lens system, an incident angle of the laser beam incident on said objective lens system being changed as said deflection mirror is rotated, a position, on said optical disc, at which the laser beam is converged varying in accordance with said incident angle;a relay lens system including at least first and second relay lens groups, said relay lens system being provided between said deflection mirror and said objective lens system, said relay lens system makes the vicinity of said deflection mirror and a principal plane of said objective lens conjugate;a diffraction grating provided between said laser source and said deflection mirror, said diffraction grating dividing an incident beam into at least 0th order beam and .+-.1st order diffraction beams having predetermined diffraction angles, said at least 0th order beam and .+-.1st order diffraction beams being incident on and deflected by said deflection mirror; anda detecting system that receives the .+-.1st order diffraction beams deflected by said deflection mirror and determines a rotational position of said deflection mirror in accordance with said received .+-.1st order diffraction beams.