LG GSA-4165B 사용자 설명서

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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 = 

(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.

•

(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.)

Incident recording pulse

Reflected recording pulse

Sampled timing  B

11T

Sample B-level (Write Power)

Level B

Sampled at timing B

Pwo decided by OPC

Recording Power

Level  B  with Pwo

normalized to recording power

Sample Disc Reflectivity 
(Read power)