| 摘要 |
Disclosure is a pickup device of an apparatus for recording or reproducing information, by irradiation of a light beam, to and from a multi-layered recording medium having a plurality of recording layers laminated through spacer layers and formed on the recording layer a pre-pit region having a reflectivity different from a reflectivity of the surrounding. The device includes an illumination optical system having an objective lens for focusing a light beam onto any of the recording layers of the multi-layered recording medium, and a detecting optical system including a photodetector for receiving and photoelectrically converting reflection light from the recording layer of the multi-layered recording medium through the objective lens. The photodetector has a normalized detector size of a size of 10 mum2 to 50 mum2.
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