{TAIL ~ An object} of the invention is to eliminate the disposition change of plural beam spots on the inner face of {HEAD ~ a drum} 
{ TAIL ~ An object } of the invention is to eliminate the disposition change of plural beam spots on the inner face of { HEAD ~ a drum }
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD