In accomplishing the object, according to one aspect of the present invention, there is provided a focus position detecting {HEAD ~ method} comprising {TAIL ~ steps} of: 
comprising
In accomplishing the object , according to one aspect of the present invention , there is provided a focus position detecting { HEAD ~ method } comprising { TAIL ~ steps } of :
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH