A very dense type of digital data storage medium. The data are encoded in a spiraling pattern by a laser that carves tiny pits into the surface of the OD master, every change from land to a pit indicating a change from a 1 to a 0, or vice versa. Where no change is recorded, the last-read digit is indicated for each increment of groove length. In the reproduction device, a small laser scans the groove, reading the changes from land to pits, converting this information back into data. The data can be text, video, or digital audio, such as CDs and laserdiscs. See LIMDOW.