{HEAD ~ The distance} between two sensing chip 31, 32 is represented by {TAIL ~ L2}, and the distance between two light focusing means 16, 16 is represented by L1 
is represented by
{ HEAD ~ The distance } between two sensing chip 31 , 32 is represented by { TAIL ~ L2 } , and the distance between two light focusing means 16 , 16 is represented by L1
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH