506 Chapter 16
Binary encoding accuracy 16-bit (65,536 steps)
Disc diameter 120 mm
Disc thickness 1.2 mm
Center hole diameter 15 mm
Permissible disc eccentricity (max.) 150 μ m
Number of tracks (max.) 20 625
Track width 0.6 μ m
Track spacing 1.6 μ m
Tracking accuracy 0.1 μ m
Accuracy of focus 0.5 μ m
Lead-in diameter 46 mm
Lead-out diameter 116 mm
Track length (max.) 5300 m
Linear velocity 1.2–1.4 m/s
16.3.1.2 Additional Data Encoded on Disc
● Error correction data.
● Control data—total and elapsed playing times, number of tracks, end of playing
area, preemphasis [may be added using either 15 μ s (10,610 Hz) or 50 μ s
(3183 Hz) time constants], and so on.
● Synchronization signals added to defi ne beginning and end of each data block.
● Merging bits used with EFM.16.3.1.3 Optical Readout System
This is shown, schematically, in Figure 16.8 , and consists of an infra-red laser light
source (GaAIAs, 0.5 mW, 780 nm), which is focused on a refl ecting layer buffed about
1 mm beneath the transparent “ active ” surface of the disc being played. This metallic