a beam supplying unit for supplying an incident laser beam including {HEAD ~ data} read from {TAIL ~ a plurality} of tracks on a holographic medium 
read from
a beam supplying unit for supplying an incident laser beam including { HEAD ~ data } read from { TAIL ~ a plurality } of tracks on a holographic medium
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH