In {HEAD ~ one embodiment}, the detector is a low resolution CCD array and the position controller includes an electronic controller and a look up table in a memory that provides {TAIL ~ adjustment data} in response to the signals from the detector 
In { HEAD ~ one embodiment } , the detector is a low resolution CCD array and the position controller includes an electronic controller and a look up table in a memory that provides { TAIL ~ adjustment data } in response to the signals from the detector
OTH HEAD HEAD HEAD HEAD HEAD HEAD 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 TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH