{HEAD ~ The detection unit} comprises a photosensor array, an imaging unit, and {TAIL ~ a processing unit} 
comprises
{ HEAD ~ The detection unit } comprises a photosensor array , an imaging unit , and { TAIL ~ a processing unit }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL