Sony DCR-DVD200 DVD Handycam Technology Handbook - Page 7

DVD MEDIA TECHNOLOGY DVD-ROM for Playback Only DVD-ROM discs are for commercial prerecorded movies, computer software programs, etc. Data is stored in the form of microscopic "pits" in the record layer of the disc. These pits are scanned by a laser and then "read" as minute reflections. These minute changes in reflection are converted to signals for further processing. There are four different DVD configurations: single-sided discs with one or two recordable layers, and double-sided discs with one or two recordable layers. ●Record Layer of DVD-ROM Pit Track pitch 0.74µm DVD-R for Recording Once DVD-R discs are for recording only once. Since data recorded to disc cannot be erased, DVD-R is a good choice for data that requires long-term storage. Unlike commercially recorded DVD-ROM discs, DVD-R discs are recorded by a process of chemical change within the surface of the disc. After a DVD-R disc is recorded, data is read by the optical pickup in a manner similar to the process of reading a DVD-ROM disc; this similarity makes DVD-R recordings compatible with DVD playback units. Recorded (or "written") areas of a disc are called "grooves"; unrecorded (or "unwritten") area is called "land." ●Record Layer of DVD-R Track pitch 0.74µm Groove Land 7 DVD Handycam TECHNOLOGY HANDBOOK