Patent ID: 6363037
Filing Date: 2002-03-26
Classification: G11B

Abstract:
An optical pickup apparatus for reproducing information from one of different kinds of optical information recording medium, each having a transparent substrate in different thickness, or for recording information onto one of said different kinds of optical information recording medium, comprising:a first light source for emitting first light flux whose wavelength is &lgr;1; a second light source for emitting second light flux whose wavelength is &lgr;2, wherein &lgr;2 is greater than &lgr;1; a converging optical system comprising an objective lens having an optical axis, a first aspherical surface and a second surface, and an image sensor, wherein the first aspherical surface has a first divisional surface, a second divisional surface and a third divisional surface, the second divisional surface being farther from the optical axis than the first divisional surface, the third divisional surface being farther from the optical axis than the second divisional surface, wherein the first divisional surface and the third divisional surface are capable of converging the first light flux on a first information recording plane of a first optical information recording medium having a first transparent substrate of thickness t1 so that information recorded in the first optical information recording medium is reproduced or information is recorded in the first optical information recording medium, wherein the first divisional surface and the second divisional surface are capable of converging the second light flux on a second information recording plane of a second optical information recording medium having a second transparent substrate of thickness t2 so that information recorded in the second optical information recording medium is reproduced or information is recorded in the second optical information recording medium, wherein t2 is greater than t1, wherein the image sensor is capable of receiving light flux reflected from the first information recording plane or the second information recording plane, and wherein a distance on the optical axis between the second surface and a crossing point at which a line extended in accordance with a formula of an aspheric surface from the second divisional surface intersects with the optical axis is determined in such a manner that a peak strength ratio of converged first light flux on the first information recording plane of the first optical information recording medium is not less than 0.9 and a peak strength ratio of converged second light flux on the second information recording plane of the second optical information recording medium is not less than 0.8.