Abstract: A record carrier on which information may be optically recorded and/or read, having a disc-shaped substrate with a spiral or concentric pattern of preformed tracks thereon and a radiation-sensitive layer extending over such track pattern. The tracks are in the form of ridges of substantially constant width and having a periodic radial wobble of a substantially constant mean frequency, which frequency is modulated by a position-information signal identifying the relative positions of the tracks in the track pattern. Apparatus for forming such a track pattern includes means for modulating the radial track wobble in accordance with the position-information signal.

Abstract: An inscribable record carrier (1) is described, which comprises a previously recorded servo-track structure provided with a recording layer. The contrast between the servo-tracks (3) provided with information areas and the intermediate tracks (5) is increased by combining wide tracks (20) with a white-writing recording layer (24) or by combining narrow servo-tracks (20) with a black-writing recording layer (21).

Abstract: An inscribable record carrier (1) is described, which comprises a previously recorded servo-track structure provided with a recording layer. The contrast between the servo-tracks (3) provided with information areas and the intermediate tracks (5) is increased by combining wide tracks (20) with a white-writing recording layer (24) or by combining narrow servo-tracks (20) with a black-writing recording layer (21). (FIGS.

Abstract: An optical record carrier having an information recording track which is inscribed with control data indicative of the change in average level of read-out signals from recorded and unrecorded portions of the track. Read apparatus for such record carrier scans the track with a radiation beam and derives a read-out electrical signal therefrom. The apparatus includes a signal-processing circuit which is adjusted for operation at the average level of signals derived from recorded portions of the track, such average level being determined by a programmable control unit from the recorded control data and the measured average level of signals from unrecorded portions of the track. Tracking of the scanning beam is also controlled in conformity with the difference in average signal strength from recorded and unrecorded portions of the track.