wherein {HEAD ~ an incidence angle} of the image beam to {TAIL ~ the optical lens} is between 0 degrees and 90 degrees 
wherein { HEAD ~ an incidence angle } of the image beam to { TAIL ~ the optical lens } is between 0 degrees and 90 degrees
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH