The second reflecting surface can be rotated around its longitudinal axis, thereby the second reflecting surface can be inserted in or removed from an optical path of {HEAD ~ light} traveling from {TAIL ~ the light source} to the first reflecting surface 
traveling from
The second reflecting surface can be rotated around its longitudinal axis , thereby the second reflecting surface can be inserted in or removed from an optical path of { HEAD ~ light } traveling from { TAIL ~ the light source } to the first reflecting surface
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 HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH