Patent ID: 7969852

Claim:
An optical pickup apparatus comprising: a first light source emitting a light flux with a wavelength λ 1 (nm); a second light source emitting a light flux with a wavelength λ 2 (nm), where λ 1 <λ 2 ; a light-converging optical system comprising a coupling lens and an objective lens; and a photodetector, wherein the optical pickup apparatus is capable of recording and/or reproducing information by converging a light flux from the first light source with the light-converging optical system on an information recording surface of a first optical information recording medium through a protective layer with a thickness of t 1 , and by detecting a reflected light flux from the information recording surface of the first optical information recording medium on the photodetector after the reflected light flux from the information recording surface of the first optical information recording medium passes through the light-converging optical system again, wherein the optical apparatus is capable of recording and/or reproducing information by converging a light flux from the second light source with the light-converging optical system on an information recording surface of a second optical information recording medium through a protective layer with a thickness of t 2 (t 1 ≦t 2 ), and by detecting a reflected light flux from the information recording surface of the second optical information recording medium on the photodetector when the reflected light flux from the information recording surface of the second optical information recording medium passes through the light-converging system again, and wherein the optical pickup apparatus satisfies following expressions (1), (2), and (3): 0 ≦|L 1 −L 2|≦0.5 (1) 0.01 <m 1 −m 2 (2) 0≦| M 1 −M 2|≦0.1 (3) where L 1 (mm) is an optical path length from the first light source to a surface facing the first light source in the first optical information recording medium, L 2 (mm) is an optical path length from the second light source to a surface facing the second light source in the second optical information recording medium, m 1 is an optical system magnification of the objective lens when information for the first optical information recording medium is recorded and/or reproduced, m 2 is an optical system magnification of the objective lens when information for the second optical information recording medium is recorded and/or reproduced, M 1 is a total optical system magnification of the light-converging optical system when information for the first optical information recording medium is recorded and/or reproduced, and M 2 is a total optical system magnification of the light-converging optical system when information for the second optical information recording medium is recorded and/or reproduced.