The image detecting module 230 can detect {HEAD ~ a first optical information} about the touch point C and {TAIL ~ the mirror point} C1 
The image detecting module 230 can detect { HEAD ~ a first optical information } about the touch point C and { TAIL ~ the mirror point } C1
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH