Even when {HEAD ~ the optical disk} has {TAIL ~ a defect}, the laser beam is continuously irradiated onto the optical disk 
Even when { HEAD ~ the optical disk } has { TAIL ~ a defect } , the laser beam is continuously irradiated onto the optical disk
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH