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