A display apparatus includes an image source, {HEAD ~ an eye position detector}, and a combiner, that are aligned to {TAIL ~ a users eye} 
A display apparatus includes an image source , { HEAD ~ an eye position detector } , and a combiner , that are aligned to { TAIL ~ a users eye }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL