Provided is {HEAD ~ a means} for applying {TAIL ~ potentials} to the first and second photodiodes to reverse bias the first and second photodiodes to produce a dark current in flowing through each photodiode 
Provided is { HEAD ~ a means } for applying { TAIL ~ potentials } to the first and second photodiodes to reverse bias the first and second photodiodes to produce a dark current in flowing through each photodiode
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH