In 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 adjustment data in response to {HEAD ~ the signals} from {TAIL ~ the detector} 
In 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 adjustment data in response to { HEAD ~ the signals } from { TAIL ~ the detector }
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 OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL