| 摘要 |
PURPOSE:To provide the optical head by which as for a detection of a focus error signal, a light spot does not cause a misalignment on a photodetector, and also, as for a tracking error signal, its adjustment can be executed, and more-over, which can be used for detecting a signal with regard to a -primary diffracted light, as well. CONSTITUTION:Between a beam splitter 3 and a photodetector 9, a cylindrical lens 7, and a diffraction grating 8 consisting of two areas whose diffraction directions or diffraction angles are different from each other are installed, and a diffracted light of the diffraction grating 8 is guided to the photodetector 9 by containing a O-order diffracted light (direct transmission light). A focus error signal by an astigmatism method is detected by the O-order diffracted light, and a tracking error signal is detected by using a + or - primary diffracted light. |
