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