When the amount of compensation in the fine displacing drive unit exceeds a predetermined value, the Y axis drive system is actuated so that the amount of {TAIL ~ compensation} by {HEAD ~ the fine displacing drive unit} lies within a predetermined range 
When the amount of compensation in the fine displacing drive unit exceeds a predetermined value , the Y axis drive system is actuated so that the amount of { TAIL ~ compensation } by { HEAD ~ the fine displacing drive unit } lies within a predetermined range
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 TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH