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