Optical disc drive 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. During the times of CD writer drives, they are often marked with three different speed ratings. In these cases, the first speed is for write-once (R) operations, the second speed for re-write (RW)
5D DVD with a capacity of 10 terabytes, approximately 2000 times the capacity of a standard DVD, compared to Holographic Versatile Disc technology, which has an estimated maximum disc capacity of 6 terabytes. The similarity of disc writing would also make it easier to make 5D DVD players backwards-compatible with existing CD and DVD technology. 5D DVD A 5D DVD is a digital storage medium akin to a DVD being developed by Peter Zijlstra, James Chon and Min Gu at the Swinburne University of Technology in Melbourne, Australia. In 2009, the developers estimated that the technology could be commercially ready in five