<P> Compared to a CD's 1.2 mm layer of polycarbonate, a DVD's laser beam only has to penetrate 0.6 mm in order to reach the recording surface . This allows a DVD drive to focus the beam on a smaller spot size and to read smaller pits . DVD lens supports a different focus for CD or DVD media with same laser . With the newer Blu - ray disc drives, the laser only has to penetrate 0.1 mm of material . Thus the optical assembly would normally have to have an even greater focus range . In practice, the Blu - ray optical system is separate from the DVD / CD system . </P> <Table> <Tr> <Th> Optical disc drive </Th> <Th_colspan="16"> Optical disc or optical media </Th> </Tr> <Tr> <Th> Pressed CD </Th> <Th> CD - R </Th> <Th> CD - RW </Th> <Th> Pressed DVD </Th> <Th> DVD - R </Th> <Th> DVD + R </Th> <Th> DVD - RW </Th> <Th> DVD + RW </Th> <Th> DVD + R DL </Th> <Th> Pressed CAT BD </Th> <Th> BD - R </Th> <Th> BD - RE </Th> <Th> BD - R DL </Th> <Th> BD - RE DL </Th> </Tr> <Tr> <Td> Audio CD player </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> CD - ROM drive </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> CD - R recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> CD - RW recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> DVD - ROM drive </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> DVD - R recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> DVD - RW recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> DVD + RW recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> DVD + R recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> DVD ± RW recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> DVD ± RW / DVD + R DL recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> <Td> None </Td> </Tr> <Tr> <Td> BD - ROM </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> </Tr> <Tr> <Td> BD - R recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> Read </Td> <Td> Read </Td> </Tr> <Tr> <Td> BD - RE recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Read </Td> </Tr> <Tr> <Td> BD - R DL recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Read </Td> </Tr> <Tr> <Td> BD - RE DL recorder </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Read </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> <Td> Write </Td> </Tr> </Table> <Tr> <Th> Optical disc drive </Th> <Th_colspan="16"> Optical disc or optical media </Th> </Tr> <Tr> <Th> Pressed CD </Th> <Th> CD - R </Th> <Th> CD - RW </Th> <Th> Pressed DVD </Th> <Th> DVD - R </Th> <Th> DVD + R </Th> <Th> DVD - RW </Th> <Th> DVD + RW </Th> <Th> DVD + R DL </Th> <Th> Pressed CAT BD </Th> <Th> BD - R </Th> <Th> BD - RE </Th> <Th> BD - R DL </Th> <Th> BD - RE DL </Th> </Tr>

What is an optical drive's x factor