Patent ID: 6671247
Filing Date: 2003-12-30
Classification: G11B

Abstract:
An optical pickup apparatus to conduct reproducing and/or recording information of a first optical information recording medium including a first transparent base plate having a thickness of t1 and a second optical information recording medium including a second transparent base plate having a thickness of t2 (t2>t1), comprising:a first light source to emit a first light flux having a wavelength of &lgr;1; a second light source to emit a second light flux having a wavelength of &lgr;2 (&lgr;12); a converging optical system to converge the first light flux or the second light flux onto a first information recording surface of the first optical information recording medium or a second information recording surface of the second optical information recording medium, the converging optical system having an objective lens; and an optical detector to receive reflected light from the first optical information recording medium or the second optical information recording medium; wherein the converging optical system comprises a diffracting section on an almost entire surface in an effective aperture of at least one surface thereof, the converging optical system generates an m-th order diffracted light ray (m being an integer other than zero) more than other order diffracted light rays when the first light flux passes the diffracting section and converges the m-th order diffracted light ray onto the first information recording surface so as to conduct the reproducing and/or recording information of the first optical information recording medium; the converging optical system generates an n-th order diffracted light ray (n being an integer other than zero) more than other order diffracted light rays when the second light flux passes the diffracting section and converges the n-th order diffracted light ray onto the second information recording surface so as to conduct the reproducing and/or recording information of the second optical information recording medium; and a spherical aberration has at least one substantially discontinuous portion when the converging optical system converges the second light flux onto the second information recording surface so as to conduct reproducing and/or recording the information of the second optical information recording medium.