LG HDR676X Service Manual page 80

3) Recording format using phase-change recording material
( DVD-RW / DVD+RW )
• Data is recorded by changing the recording layer from the amorphous status to the crystalline status, and played
back by reading the difference of the reflection coefficient.
Amorphous: Non-crystalline.
Disc structure
Recording principles
[ Recording ]
When a high-power laser is applied to the recording material, it melts and then becomes amorphous with a low
reflection coefficient when it quickly cools off. When a mid-power laser is applied to heat gradually the recording
material and then gradually cools it off, it becomes crystal with a high reflection coefficient.
[ Playback ]
A low-power laser is used for playback. The amount of reflected light depends on the status (amorphous or crys-
talline) of the recording material. This is detected by an optical sensor.
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