{HEAD ~ A signal} corresponding to {TAIL ~ a distance} from the present position of the laser beam spot to the desired track is obtained from the displacement and a desired count value, and is inputted to a function generator to thus obtain a square root of the distance 
corresponding to
{ HEAD ~ A signal } corresponding to { TAIL ~ a distance } from the present position of the laser beam spot to the desired track is obtained from the displacement and a desired count value , and is inputted to a function generator to thus obtain a square root of the distance
HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH