The prerequisites for the fact that the “golden” discs are worse than the “aluminum” ones are laid down in the recording technology itself. Standards for compact discs provide that the reflection of the laser beam from bright areas should be at least 70%.
Such requirements are met for stamped discs. However, recordable discs, unlike stamped discs, have an additional recording layer of organic polymer. This layer has limited transparency. Therefore, standards for recordable discs allow that reflection from highlights should be at least 65%. Continue reading
In devices with a moving coil there are no pre-fixed positions. Instead, they use a special guidance system (positioning), which accurately brings the heads to the desired track.
The system of precise guidance of the heads on the tracks is called a servo drive, and for its operation a feedback signal is required that carries information about the real relative position of the tracks and heads.
Temperature fluctuations do not affect the accuracy of the drive. When compressing and expanding disks (rotation, temperature), all changes in their sizes are monitored by a servo drive and the positions of the heads are adjusted. Continue reading