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)
Optical disc packaging for DVD-Audio, and as of mid-2006, the case format for all albums released by the Universal Music Group in Europe. Many alternatives to the standard jewel case may also be found, including larger DVD-style cases with a more book-like shape. It is not uncommon to find CDs housed in custom cases, tins and boxes of varying shapes and sizes. Slipcases and other envelope-type designs are also occasionally used. Some DualDiscs are packaged in jewel cases of a somewhat different design from the CD version; the inside edge is rounded instead of flat, and the physical position of the disc is