| 摘要 |
PROBLEM TO BE SOLVED: To provide a pickup device which can reduce a noise and stably write or read data in or from a multilayer recording layer. SOLUTION: The pickup device of a device which irradiates a multilayer recording medium having a plurality of recording layer laminated through a spacer layer and a prepit region having an average reflectance different from that of the surrounding regions on the recording layer with a light beam for recording or reproducing information, is provided with an irradiation optical system including an objective lens to condense the light beam on any recording layer of the multilayer recording medium, and a detecting optical system including a photodetector to receive reflected light from the recording layer of the multilayer recording medium through the objective lens for performing a photoelectric conversion. The photodetector has a standardized detector size of 10 to 50 μm2. |
