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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
22
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
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