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