The difference between {HEAD ~ the focal distances} of {TAIL ~ the beams} can be determined only by controlling a distance between the optical member and the reflecting member, and does not require the positioning precision 
of
The difference between { HEAD ~ the focal distances } of { TAIL ~ the beams } can be determined only by controlling a distance between the optical member and the reflecting member , and does not require the positioning precision
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL 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 OTH OTH OTH OTH