A signal corresponding to {HEAD ~ a distance} from {TAIL ~ 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 
A signal corresponding to { HEAD ~ a distance } from { TAIL ~ 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
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL 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