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