| 摘要 |
PURPOSE:To provide optical system without generating a track signal and an offset due to optical axial displacement between a moving system and a fixed system in the optical head used for an optical drive, etc. CONSTITUTION:The optical head possesses a photodetector 21 having an area 21-A in the middle and at least bisected areas 21-B and 21-C in its outer periphery and a lens 20 for making light in the middle part of light flux comprising 0th-order light of reflected light flux of an optical disk 1 incident upon the middle area 21-A of the photodetector 21 and also making light of the outer peripheral part of the reflected light flux incident upon the bisected areas 21-B and 21-C in the outer periphery of the photodetector 21, whereas a track signal is detected based on the outer peripheral areas 21-B and 21-C. |
