SCEN103 CD 3-Beam Tracking Scheme

On the top and bottom frames, the central spot B has drifter to one side of the track and the modulation is greatest in one of the side beams A or C. In the center frame, the central spot B is correctly located over the track and the modulation from the central spot is a maximum.

[Schematic of CD tracking

Source: "The physics of the compact disc" by John A. Cope, Physics Education 28, 1993.

"http://www.physics.udel.edu/~watson/scen103/cd-tracking.html"
Last updated May 17, 1999.
Copyright George Watson, Univ. of Delaware, 1996.