A correction signal is applied to the modulator to maintain {HEAD ~ substantially uniform exposure} across {TAIL ~ the output medium} notwithstanding variations in the velocity of the beam 
across
A correction signal is applied to the modulator to maintain { HEAD ~ substantially uniform exposure } across { TAIL ~ the output medium } notwithstanding variations in the velocity of the beam
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH