{TAIL ~ Perimeter receiver fiber optics/elements} are spaced apart from a central source fiber optic/element and received light reflected from {HEAD ~ the surface} of the object is measured 
{ TAIL ~ Perimeter receiver fiber optics / elements } are spaced apart from a central source fiber optic / element and received light reflected from { HEAD ~ the surface } of the object is measured
TAIL TAIL TAIL TAIL TAIL 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 OTH OTH OTH OTH OTH