| 摘要 |
<p>PROBLEM TO BE SOLVED: To relax the relative positional accuracy between a hologram element and a photodetector, to suppress the generation of offset of a tracking error signal, to improve the assemblability by attaining the constitution capable of accurately mounting on an optical head device with respect to the external shape of the package, and to enable the detection of a high quality signal with less noise by simplifying a signal process circuit with the reduction of the number of detecting elements in each signal detection of focus error, track error and information reproduction. SOLUTION: The device is provided with a laser source, the hologram element 4, an objective lens for converging the laser beam on a recording medium, the photodetector 8 for receiving the light reflected from the recording medium, and a prism optical element for guiding the reflected light to the photodetector 8, then the laser beam is converged on the recording medium, and also the focus error signal and the track error signal are detected by the reflected light 16 from the recording medium. By a polarizing hologram element 4, the detected beam on the photodetector is divided by the hologram element having at least one divided line 5 to relatively enlarge the size of the beam diameter of the signal light on a photodetecting element.</p> |
