发明授权
US5633844A Optical pickup device with three beam tracking servo control using oval beams 失效
采用椭圆形光束的三光束跟踪伺服控制的光学拾取装置

Optical pickup device with three beam tracking servo control using oval
beams
摘要:
An optical pickup device for writing or reading data from an optical information recording medium has a recording layer whose state changes in response to a density of intensity of an irradiated light beam and a track being used for a tracking servo control system. The device includes a first light spot irradiating element for irradiating a writing or reading light beam onto the recording layer to form a writing or reading spot and a second light spot irradiating element for irradiating at least one controlling light beam onto the recording layer to form a controlling spot having a major axis extending along the track and being longer than a transverse axis perpendicular to the major axis within a level of luminous flux density keeping an original state of the recording layer, whereby a tracking servo control signal having a sufficient level is obtained.
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