CD-R Recording and Playback Principle
Playback is realized by detecting changes in the reflection, when a weak focused laser beam falls onto a recorded mark and when the light falls onto an unrecorded land (area between marks). The laser beam is reflected when the light falls onto the land and is diffused when the light falls onto the mark. Both transient states from the land (reflected) to the mark (diffused) and from the mark to the land are allotted " 1 ", while other steady states whether on the land (reflected) or on the mark (diffused) are allotted " 0 ". This data is combined with "0" and "1" like the other digital data. However, in case of the CD, the state changed in a reflection is allotted "1", while the other area is allotted "0". In other words, the boundary between the pit and land is allotted " 1 ", while the other flat portions are " 0 "as far as the same state continues whether for pit or for land.