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Writing Process Of Disc - LG GWA-4164B Service Manual

Dvd/cd rewritable drive
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2) ROPC (Running Optimum Power Control)
• Variable primary factor of Optimum Power
– Change of Power sensitivity on the Disc. (limited to 0.05 *Po)
– Wavelength shift of the laser diode due to the operating temperature change.
– Change of the Spot aberration due to the Disc skew,
Substrate thickness, Defocus.
– Change of Disc or Optics conditions due to the long term OPC
==> It is necessary to adjust continuously to obtain the Optimum Power.
• Principle of Running OPC
– To meet the factors mentioned above,
a horizontal _ direction movement of a curve is uesd.
– Beta = f(B-level) = constant on the Recorded Disc
– Procedure of ROPC
a. Reference B-level is determined during OPC Procedure.
b. During Recording, B-level value is controlled to have a close
Reference B-level value.
c. Normalization of B-level is used to eliminate the effect of reflectivity fluctuation.
==> The reflected B-level value is normalized by the disc reflectivity itself.
11T
Sample B-level (Write Power)

10. Writing Process of DISC

CD-R/RW Media
Write Strategy
Determination
PCA Test Area
PCA Count Area
* Recording Capacity of CD-R/RW (74Minute Recording media)
• (2048 Byte/Sector) X (75 Sector/Second) X (60 Second/Minute) X 74 Minute
= 681,984,000 Bytes = 682 Mbytes
• But the actual recording capacity is about 650 Mbytes. (according to the ISO 9660 standard, approximately
30 Mbytes are used to make directory structure and volume names.)
Sample Disc Reflectivity
(Read power)
Incident recording pulse
Reflected recording pulse
Sampled at timing B
normalized to recording power
Level B with Pwo
Pwo decided by OPC
Recording Power
Program Area
PMA Area
Lead-In Area
Lead-out Area
Sampled timing B
31

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