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 optical disc record carrier having a radiation-sensitive surface and a spiral or concentric pattern of information tracks thereon. The radial displacement of each track is modulated to produce a periodic radial wobble, the frequency of such periodic displacement being modulated by a position-information signal identifying the relative positions of the tracks. During recording or reading of information on the tracks the track modulation is read by a scanning beam. A clock signal for controlling scanning velocity is recovered from the track displacement modulation, and an FM demodulator recovers the position-information signal from the frequency modulation of such displacement.

Abstract: A record carrier (1) in the form of a disc-shaped carrier provided with a radiation-sensitive layer (6) having a servo track (4). The servo track produces track modulation by having a radial wobble, or lateral periodic deviation whose frequency is modulated with a position-information signal (FIG. 2). Apparatus (FIG. 8) is presented which forms the track pattern during manufacture of the record carrier (1). When an information signal (Vi) is recorded on the record carrier (1) and the recorded signal is read by recording and/or read apparatus (FIG. 4), the position-information signal (FIG. 2) is recovered by an FM demodulator device (60) from variations in the scanning beam (55) which are propduced by the track modulation. Moveover, a clock signal for the purpose of scanning-velocity control is recovered from this variation in the scanning beam. Furthermore, embodiments of the record carrier highly suitable for recording EFM-modulated signals are described.