image disc

The picture disc is a disc up to 30 cm (12 ") in size, which was used for video playback in the eighties. It is provided with a reflective metallization into which tracks with elongated depressions, so-called pits, are burned. These contain the modulated digitalinformation that is interrogated by laser light reflection.

Analogvideo signals with a video bandwidth of 4 MHz are stored on picture disks using the direct color method, and two analog audio channels are also stored. There are various playback functions, so picture plates can play back still images in addition to normal playback. Picture discs differ in terms of the recording and playback method, which has a direct influence on the playing time. In recording technology, a distinction is made between Constant Linear Velocity( CLV), which operates at a constant speed, and Constant Angular Velocity( CAV), which has a constant angular velocity.

The development of the various image discs has been overtaken by optical storage, especially DVDs, HD-DVDs and Blu-Ray discs.