{HEAD ~ an actuator} for moving either the pinhole plate or {TAIL ~ the focusing lens} to control the amount of the first portion of the focused laser beam passing through the pinholes for replaying a target track on the holographic medium, 
for moving
{ HEAD ~ an actuator } for moving either the pinhole plate or { TAIL ~ the focusing lens } to control the amount of the first portion of the focused laser beam passing through the pinholes for replaying a target track on the holographic medium ,
HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL 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