A modulated laser beam is scanned across the object to create a plurality of spots which are viewed by {HEAD ~ a pair} of {TAIL ~ well matched receivers} 
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A modulated laser beam is scanned across the object to create a plurality of spots which are viewed by { HEAD ~ a pair } of { TAIL ~ well matched receivers }
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 TAIL