To carry out these operations, the optical head 13 is moved radially over the optical disk 11, so that {HEAD ~ a laser beam spot} is positioned at {TAIL ~ a predetermined track} 
is positioned at
To carry out these operations , the optical head 13 is moved radially over the optical disk 11 , so that { HEAD ~ a laser beam spot } is positioned at { TAIL ~ a predetermined track }
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 REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL