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