| 摘要 |
<p>An optical reproducing head for reproducing an information signal recorded on an optical record medium includes a semiconductor laser for generating a laser beam, a first off-axis hologram lens irradiated with the laser beam from the semiconductor laser to produce a beam of parallel rays of light that has an optical axis which is off-set with respect to the optical axis of the laser beam, a second off-axis hologram lens irradiated with the beam of parallel rays of light from the first off-axis hologram lens to generate a focused beam which has an optical axis which is off-set with respect to the optical axis of the beam of parallel rays of light and has an optical axis perpendicular to the optical record medium, and a photo-detector detecting the intensity of a non-diffracted wave beam from the first off-axis hologram lens means, the non-diffracted wave beam being at least part of the focused beam which has been reflected from the optical record medium and has been diffracted by the second off-axis hologram lens. The output of the photodetector is used to produce a focus error signal and a tracking error signal for controlling the focus servo and tracking servo operations.</p> |
