| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical disk device capable of reproducing a signal even from an optical disk whose substrate thickness is unsuitable for an objective lens. SOLUTION: In this optical disk device, a laser beam transmitted from a semiconductor laser beam source 1 is converged by an objective lens 5 through a collimator lens 2 and a beam splitter 3, an optical disk 6 is irradiated with the beam, the reflected light beam from the optical disk 6 is separated in the orthogonal direction to the reflected optical axis through the objective lens 5 and detected by a photodetector 9. In this case, the light receiving surface of the photodetector 9 is divided into a middle area on which the central part of the reflected beam is made incident and a peripheral area on which its outer peripheral part is made incident, when the substrate thickness of the optical disk conforms to the objective lens, light quantities received by both middle and outer peripheral areas of the photodetector 9 are used for an information reproducing signal and, when it does not conform, a light quantity received by the middle area of the photodetector 9 is used for the signal. |
