{HEAD ~ The light intensity} detecting {TAIL ~ circuit comprises} first and second photodiodes having predetermined scale and structure 
detecting
{ HEAD ~ The light intensity } detecting { TAIL ~ circuit comprises } first and second photodiodes having predetermined scale and structure
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH