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