The other part of {TAIL ~ the incident beam} is refracted and transmitted through the optical member and then totally reflected by the reflecting member to return to {HEAD ~ the optical member} 
The other part of { TAIL ~ the incident beam } is refracted and transmitted through the optical member and then totally reflected by the reflecting member to return to { HEAD ~ the optical member }
OTH OTH OTH OTH TAIL 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 HEAD HEAD HEAD HEAD HEAD HEAD HEAD