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    • 38. 发明授权
    • Optical head using a light blocking device to lower the numerical
aperture of an incident beam
    • 光头使用遮光装置降低入射光束的数值孔​​径
    • US5991255A
    • 1999-11-23
    • US958296
    • 1997-10-27
    • Junichi Takahashi
    • Junichi Takahashi
    • G11B7/135G11B7/00G11B7/125
    • G11B7/1381G11B7/127G11B7/139G11B7/13922G11B2007/0006G11B2007/13727
    • It is an object of the invention to provide a compatible optical head apparatus for optical disks with different thicknesses. A laser beam emitted by a semiconductor laser is convert into a collimated laser beam by a collimator lens and passes through a circular aperture, hence an effective NA of an objective lens is reduced. Accordingly, the effective NA for the incident laser beam on the optical disks is lower than that for the reflected laser beam from the optical disk by more than 0.1. Moreover, in the optical head apparatus according to another embodiment, another semiconductor laser with a different lasing wavelength is provided, and when a recorded signal of the optical disk with a wavelength dependent characteristic is reproduced, only one of the semiconductor lasers is activated in accordance with the characteristic of the optical disk to be reproduced.
    • 本发明的目的是提供一种用于具有不同厚度的光盘的兼容的光学头装置。 由半导体激光器发射的激光束通过准直透镜转换成准直的激光束,并且通过圆形孔径,从而减小了物镜的有效NA。 因此,光盘上的入射激光束的有效NA低于来自光盘的反射激光束的有效NA大于0.1。 此外,在根据另一实施例的光头装置中,提供具有不同激光波长的另一半导体激光器,并且当再现具有波长相关特性的光盘的记录信号时,只有一个半导体激光器被激活 具有要再现的光盘的特性。