Patent ID: 7170844

Claim:
An optical pick-up apparatus for recording to or reproducing from a first optical information recording medium having a first information recording surface and thereon a first transparent substrate whose thickness is t 1 , and a second optical information recording medium having a second information recording surface and thereon a second transparent substrate whose thickness is t 2 , which is thicker than t 1 , the optical pick-up apparatus comprising: (a) a first light source for emitting a first light flux having a wavelength of λ 1 for recording to or reproducing from the first optical information recording medium, and a second light source for emitting a second light flux having a wavelength of λ 2 , which is greater than λ 1 , for recording to or reproducing from the first optical information recording medium, (b) a light converging optical system, which has an aperture, an objective lens and a correction lens, converging the first light flux onto the first information recording surface so that a wavefront aberration on the first information recording surface is not more than 0.07 λrms, wherein the first light flux enters into the objective lens as parallel light and the second light flux enters in the objective lens as non-parallel light, wherein the aperture and the objective lens are interlocked and shifted in a direction perpendicular to an optical axis of the light converging optical system, and wherein the correction lens includes a first section and a second section, which is farther apart from the optical axis than the first section; and (c) a photodetector for detecting light reflected from the first or second information recording surface, wherein the second light flux, which is passed through the first section of the correction lens, generates a wavefront aberration of not more than 0.07 λrms on the second optical information recording medium, wherein the second light flux, which is passed through the second section of the correction lens, generates an over-spherical aberration.