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 a desired count value, and is inputted to a function generator to thus obtain {HEAD ~ a square root} of {TAIL ~ the distance} 
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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 a desired count value , and is inputted to a function generator to thus obtain { HEAD ~ a square root } of { TAIL ~ the distance }
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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL