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The optical head, LD module, from the diffraction component null illuminant and the aforementioned illuminant which are used for the optical recording
The optical head, LD module, from the diffraction component null illuminant and the aforementioned illuminant which are used for the optical recording
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机译:来自用于光学记录的衍射成分零光源和上述光源的光学头LD模块
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摘要
A beam emitted from a light source 1 is separated into a main beam and a sub beam by a diffraction element 2. Because the diffraction element 2 has a diffraction pattern shaped like sinusoidal wave, the spot of the sub beam becomes larger than that of the main beam. As a result, the sub beam little contains any tracking cross component which is generated when the spot crosses any one of tracks of an optical disk 5. Accordingly, when a signal output from a detector provided for detecting the sub beam is subtracted from a push pull signal of the main beam, it is possible to obtain a tracking error signal or a focusing error signal substantially containing no DC offset component.
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