Apparatus and {HEAD ~ method} for controlling {TAIL ~ tracking} and focusing servo in a holographic digital data storage system 
for controlling
Apparatus and { HEAD ~ method } for controlling { TAIL ~ tracking } and focusing servo in a holographic digital data storage system
OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH