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Untitled Document
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Playback Principle |
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| The principle of signal reading is quite simple; signals are read
based on the differences in the amount of reflection when laser light
(weaker than the write laser) strikes a "pit" on the surface
of the disc versus a "land". The laser beam is reflected
when the light falls onto the land and is diffused when the light
falls onto the mark. These differences are converted into digital
form before being processed into original signals. |
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[Player Block Diagram]
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[Electrical Signals]
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[Signal Classification 3T~11T]
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| As is shown in the above figure, playback principle is to read the
varying lengths of "pits" and "lands," from the
shortest 3T to the longest 11T and then to convert these into original
signals. |
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Principles of CD-RW Recording, Erasing and
Playback. |
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Recording Principle |
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CD-RW recording principle is the same as that of CD-R except that
CD-RW uses phase change technology instead of surface 'deformation.'
When the phase change material is heated above its melting temperature
and then cooled rapidly, the material transforms into solid phase
of crystallization. By controlling the temperature of the laser, crystalline
areas and non-crystalline areas are formed. The crystalline areas
will reflect the laser, while the other areas will absorb it.
The differences register as binary data. |
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| To erase or write over recorded data, the higher temperature laser
is used, which results in the amorphous form, which can then be reformed
by the lower temperature laser. According to Sony, the process can
be repeated up to 1000 times. |
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Erase Principle |
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The unstable amorphous areas transform back to crystalline state
when enough energy is applied.
This recrystallization of the amorphous-phase marks is the basis of
CD-RW erasure. This is what enables CD-RW to be written, erased, and
rewritten with just a little adjustment of laser power. |
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Playback Principle |
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| Principle of CD-RW playback of the recorded data is the same as
that of CD-R except that CD-RW reads the 9 signals ranging from 3T
to 11T using difference in reflectivity between amorphous and crystalline
areas. |
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[CD-RW Recording Marks]
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