To provide {HEAD ~ a fine tuning} of the D.C. restoration function, {TAIL ~ a reference strip} of known reflectivity is provided along a crosstrack edge of the platen surface 
To provide { HEAD ~ a fine tuning } of the D.C. restoration function , { TAIL ~ a reference strip } of known reflectivity is provided along a crosstrack edge of the platen surface
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH