a mirror unit configured to, as a result of being arranged in a light path of the object light, change {HEAD ~ the light path} of {TAIL ~ the object} light 
a mirror unit configured to , as a result of being arranged in a light path of the object light , change { HEAD ~ the light path } of { TAIL ~ the object } light
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 HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH