Basics DVD-ROM Drive Technology - 31
Table 4: CD vs. DVD Comparison
CD DVD
Disc Diameter 120mm 120mm
Disc Thickness 1.2mm 1.2mm
Disc Structure Single substrate Two bonded 0.6mm
substrates
Laser Wavelength 780nm (infrared) 650 and 635nm (red)
Numerical Aperature 0.45 0.60
Track Pitch 1.6um 0.74um
Shortest Pit/Land Length 0.83um 0.4um