to extract image data processed by at least one of the plurality of {HEAD ~ image processing units} from output of the plurality of {TAIL ~ image processing units}, and 
to extract image data processed by at least one of the plurality of { HEAD ~ image processing units } from output of the plurality of { TAIL ~ image processing units } , and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH