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