| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical pickup device capable of efficiently receiving a reflected light from an information recording medium having plural recording layers in a depth direction through a pinhole, and accurately reproducing information recorded in a desired recording layer. SOLUTION: This device is constructed in such a manner that a laser light emitted from a semiconductor laser 1 is passed through a beam splitter 2 and an objective lens 5, an information recording medium 7 having plural laminated recording layers 6 is irradiated with this laser light, its reflected light is passed through the objective lens 5, the beam splitter 2 and a pinhole and received by a photodetector, and information recorded in the desired recording layer 6 of the information recording medium 7 is reproduced. In this case, when the radius of the pinhole is (r), the numerical aperture of the detection system of the reflected light is NA and the wavelength of the laser light is λ, Vp=2π.r/(λ/NA) satisfies 3<=Vp<=6. |
