An imaging unit is arranged in front of the photosensor array such that it maps an image of {TAIL ~ said array} of {HEAD ~ LEDs} on said photosensor array 
An imaging unit is arranged in front of the photosensor array such that it maps an image of { TAIL ~ said array } of { HEAD ~ LEDs } on said photosensor array
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH