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 {HEAD ~ a square root} of the distance 
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 { HEAD ~ a square root } of the distance
OTH OTH OTH OTH 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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH