Therefore, {HEAD ~ the process} to construct {TAIL ~ the optical pickup device} is easy, and thus, the errors generation ratio of the optical pickup devices is sharply decreased 
to construct
Therefore , { HEAD ~ the process } to construct { TAIL ~ the optical pickup device } is easy , and thus , the errors generation ratio of the optical pickup devices is sharply decreased
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL 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