Hardware Reference
In-Depth Information
Caution
You should handle optical media with the same care as a photographic negative. The disc is
an optical device and degrades as its optical surface becomes dirty or scratched. Also, it is
importanttonotethat,althoughdiscsarereadfromthebottom,thelayercontainingthetrack
is actually much closer to the top of the disc because the protective lacquer overcoat is only
6-7 microns thick. Writing on the top surface of a disc with a ballpoint pen, for example,
easily damages the recording underneath. You need to be careful even when using a marker
to write on the disc. The inks and solvents used in some markers can damage the print and
lacquer overcoat on the top of the disc, and subsequently the information layer right below.
Useonlymarkersdesignedforortestedasbeingcompatible withoptical media.Theimport-
ant thing is to treat both sides of the disc carefully, especially the top (label) side.
Mass-Producing CDs
Commercialmass-producedopticaldiscsarestampedorpressedandnotburnedbyalaser
asmanypeoplebelieve(see
Figure11.1
)
.Althoughalaserisusedtoetchdataontoaglass
master disc that has been coated with a photosensitive material, using a laser to directly
burn discs would be impractical for the reproduction of hundreds or thousands of copies.
Figure 11.1
CD manufacturing process.
