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