| 摘要 |
PURPOSE:To improve the reliability of an optical head and to reduce the cost by constituting second photodetectors, which detect the change of diffracted light, on a semiconductor substrate constituting a first photodetector as one body. CONSTITUTION:A first photodetector 1b and second photodetectors 11 and 12 are unified and are produced on one semiconductor substrate. A hologram element 2 diffracts and separates reflected light so that a focus error signal or a tracking error signal can be detected in the vicinity of the light reception plane of the first photodetector 1b. The focus error signal is taken out by operating the difference signal between respective difference signals 11a-11b and 12a-12b of second photodetectors 11 and 12 unified with the first photodetector 1b. Thus, the reliability of the optical head is improved and the cost is reduced. |
