By these means, the measurement range determines that range in which the transmitting light spot lies almost completely in the field of {HEAD ~ view} of {TAIL ~ the receiving optic} 
of
By these means , the measurement range determines that range in which the transmitting light spot lies almost completely in the field of { HEAD ~ view } of { TAIL ~ the receiving optic }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL