{HEAD ~ The position} of the tool holding unit is measured by {TAIL ~ an optical length measuring device}, and the difference between the measured value and a desired value is compensated by the fine displacing drive unit 
{ HEAD ~ The position } of the tool holding unit is measured by { TAIL ~ an optical length measuring device } , and the difference between the measured value and a desired value is compensated by the fine displacing drive unit
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL TAIL TAIL 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