26
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.
CD-R/RW Media
Write Strategy
Determination
PCA Test Area
Program Area
PMA Area
Lead-In Area
Lead-out Area
OPC
PCA Count Area
ROPC
* 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.)
