As shown in FIG 2, the image beam C emits to the beam splitter 30 with an incidence angle θ between 0 and 90 degrees , and {HEAD ~ the preferable incidence angle} θ is between 40 degrees and {TAIL ~ 50 degrees} 
is between
As shown in FIG 2 , the image beam C emits to the beam splitter 30 with an incidence angle θ between 0 and 90 degrees , and { HEAD ~ the preferable incidence angle } θ is between 40 degrees and { TAIL ~ 50 degrees }
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 HEAD HEAD HEAD OTH REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL