This is done by controlling an adjustable optical filter having an adjustable optical element for {HEAD ~ each} of {TAIL ~ the sampling positions} 
of
This is done by controlling an adjustable optical filter having an adjustable optical element for { HEAD ~ each } of { TAIL ~ the sampling positions }
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