The invention provides {HEAD ~ correction apparatus} which comprises {TAIL ~ a series connection} of the visual system with a photo sensor , an amplifier , a counter and a comparator  
The invention provides { HEAD ~ correction apparatus } which comprises { TAIL ~ a series connection } of the visual system with a photo sensor , an amplifier , a counter and a comparator
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH