The beam which is reflected by the optical member and {HEAD ~ the beam} which is reflected by {TAIL ~ the reflecting member} after being transmitted through the optical member generate a dual focus on the optical disc, in which the dual focus has different focal distances 
The beam which is reflected by the optical member and { HEAD ~ the beam } which is reflected by { TAIL ~ the reflecting member } after being transmitted through the optical member generate a dual focus on the optical disc , in which the dual focus has different focal distances
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH