| 摘要 |
PURPOSE: To obtain a thin optical pickup in which adjustment is simplified by a constitution wherein a light beam is split on a diffraction grating face into three and condensed onto a recording medium and then the reflected light is diffracted by a hologram element and enters not through the diffraction grating face but through a mirror into a light detection stage. CONSTITUTION: An light beam emitted from a semiconductor laser element 4 is split into three main beams through a diffraction grating face 5a, e.g. a transmission diffraction grating 5 for splitting into three, comprising protrusions and recesses of constant pitch. These three beams pass, in zero-order, through a transmission hologram element 6 having a hologram face 6a comprising a group of curves the pitch of protrusions and recesses thereof varies gradually. These three beams are reflected upward on a reflector 7 and condensed through an objective lens 8 onto an optical recording medium 1. The reflected light passes through the lens 8 and reflected on the reflector 7 and further reflected on the face 6a of the element 6 and a reflector 9, while avoiding the face 5a, before entering directly into a photodetecting means 3. This constitution realizes a thin optical pickup in which adjustment is facilitated. |
