Thus, a signal proportional to the total amount of {HEAD ~ light} received by {TAIL ~ the photo detecting elements 6a} and 6b is supplied to the light intensity control circuit D 
Thus , a signal proportional to the total amount of { HEAD ~ light } received by { TAIL ~ the photo detecting elements 6a } and 6b is supplied to the light intensity control circuit D
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH