| 摘要 |
PURPOSE:To attain small size and light weight for an optical pickup by adopting the constitution so that beam shaping and beam separation are implemented by one diffraction grating. CONSTITUTION:A light L1 radiated from a light source 1 is collimated into a collimated light L2 by a collimate lens 2. In this case, the intensity distribution of the collimated light L2 is elliptic. The collimated light L2 is made incident in a diffraction grating 8, the collimated light L2 is diffracted with a high efficiency and becomes an incident light L3 to an objective lens 6. The incident light L3 has a circular intensity distribution. The incident light L3 passes through a pi/4 plate 5 and the objective lens 6 and is focused on the optical disk 9. In this case, the incident light L3 is converted into a circularly polarized light L4. A reflected light L5 including the information from the disk 9 passes through the pi/4 plate 5 and is converted again into a linearly polarized light L6 and made incident in the grating 8. In this case, the diffraction efficiency of the incident light 6 at the grating 8 is low in the direction of polarization, the incident light L6 passes through the grating 8 without any modification and is led to a photodetector 7. |
