The trough shaped reflectors are moved in synchronism with the scanning movement of the beams so that the images of the lamp filaments remain in one dimensional focus throughout {HEAD ~ scanning} of {TAIL ~ the flat document plane} 
of
The trough shaped reflectors are moved in synchronism with the scanning movement of the beams so that the images of the lamp filaments remain in one dimensional focus throughout { HEAD ~ scanning } of { TAIL ~ the flat document plane }
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 OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL