Philips DVDR985 Technical Training Manual page 7

DVDs
All of the previously discussed technologies
apply to the DVD. Like CDs, DVDs are also
stamped into play only discs. In this discussion,
we will point out the differences between DVDs
and CDs. If you are new to disc based technolo-
gy, you will want to start with the information pre-
ceding this discussion.
DVD Disc Mechanical Differences
Most DVDs are single sided, however, the DVD
specification allows for two readable layers, and
the disc can be double sided. We will start our
discussion with single sided, single layered
discs. A Digital Versatile Disc, DVD, looks very
similar to a CD. Refer to Figure 8. The Clamping
Area is larger, starting at 11 mm centered to 16.5
mm centered. The Lead In Area is smaller,
DVD
Figure 8 - DVD Mechanical Layout
Figure 9 – DVD and CD Pit Structure.
measuring 22.7 mm centered to 24 mm cen-
tered. The Information Area is limited to 116mm
centered.
Two of the big differences between DVDs and
CDs are the Pit and Land sizes, and the track
widths. Refer to Figure 9.
The Manufacturing process of a DVD is compa-
rable to that of a CD. The main difference is the
thickness. The DVD can be a double sided prod-
uct. Each side is .6mm. The two sides are glued
back to back, producing 1.2mm total thickness.
CD
6