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The most important chunk of an optical disc drive is an optical path, placed in a pickup head (PUH), usually consisting of semiconductor laser, a Cassette to CD Recorder lense for guiding the laser beam, and photodiodes detecting the burnished reflection from disc's surface. |
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Double layer (DL) television have two independent data layers separated by a semi-reflective layer. Both layers are open from the same side, but require the optics to copper the laser's focus. Traditional only layer (SL) writable photo opportunity are produced with a spiral groove molded in the protective polycarbonate layer (not in the data recording layer), to lead and synchronize the speed of recording head.