| 摘要 |
PURPOSE: A data detector of a multiple layer CD(Compact Disk) is provided to save a large capacity of data by forming multiple track layers of a CD. CONSTITUTION: A 3D multiple wavelength whispering gallery laser(30) emits various kinds of laser beams(ray1,ray2) having different wavelength at different angles. A first and a second photodetector(PD1,PD2) detect the laser beams reflected from tracks in a first(L1) and a second layer(L2) of a double layer CD(32). Thereby, data recorded on two layers of the double layer CD are read out at the same time to promote synchronous parallel signal processing. In addition, to improve efficiency, NBRC(Narrow Band Reflective Coating) of the first and second laser beam is performed under the first and second layer. All of the first laser beam is reflected from the first layer, and data on the first layer are transferred to the first photodetector. Most of the second laser beam is transmitted from the first layer and is incident to the second layer. The second layer data are transferred to the second photodetector through the second layer.
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