obtaining {HEAD ~ a focus position} of the object with {TAIL ~ respect} to the optical system based on the evaluation function calculation values 
obtaining { HEAD ~ a focus position } of the object with { TAIL ~ respect } to the optical system based on the evaluation function calculation values
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH