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