{HEAD ~ The optical touch device} can avoid {TAIL ~ a blind zone} and can be used as a dual touch device or a multi touch device 
avoid
{ HEAD ~ The optical touch device } can avoid { TAIL ~ a blind zone } and can be used as a dual touch device or a multi touch device
HEAD HEAD 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