| 摘要 |
19 SEMICONDUCTOR LASER OPTICAL HEAD ASSEMBLY An improved optical head for reading information recorded on a reflected medium. The optical head uses a hologram lens assembly having a transparent plate and a hologram lens, the transparent plate being obliquely positioned relative to a forward and a return beam paths. The transparent plate corrects beam aberrations in a laser beam emitted by a semiconductor laser on the forward beam path. The hologram lens diffracts the laser beam on the return beam path onto a photodetector. Both the transparent plate and the hologram lens add beam aberrations to the defracted laser beam on the return beam path for tracking purposes. The hologram lens assembly may also include a second hologram lens, preferably a three beam diffraction grating, for tracking purposes. The hologram lens and the diffraction grating may be located on the obliquely positioned transparent plate or on other transparent plates.
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