Apparatus for inscribing and/or reading a record carrier

Claim 1

An apparatus for inscribing and/or reading a record carrier, which record carrier comprises a disk-shaped substrate with a radiation-sensitive information layer and is provided with information areas arranged in accordance with a spiral or concentric track pattern, which record carrier is intended for recording and/or reproducing digitally coded information of a fixed bit frequency in the information areas via a radiation beam, which information areas have an optically detectable first periodic track modulation, the track position being modulated in a radial direction, for generating a radial tracking signal during recording and/or reproduction, said modulations being radially in phase, which apparatus for this purpose comprises an optical system for projecting a light beam onto said information areas, a detector for detecting the radiation which is reflected or transmitted by the recording areas, which detector is divided into two halves along a line corresponding to the track direction, and a read circuit for extracting a read-information signal from the detected radiation, characterized in that the apparatus comprises means for determining the difference between the radiation detected by two halves of the detector, means of extracting a signal of a frequency corresponding to the period of the periodic track modulation, means for generating an even higher harmonic of said extracted signal, means for the synchronous detection, by means of a reference signal, of a signal supplied by the detector in order to generate a radial tracking signal, and means for generating said reference signal in synchronism with said even higher harmonic.

Claim 2

An apparatus for inscribing and/or reading a record carrier, which record carrier comprises a disk-shaped substrate with a radiation-sensitive information layer and is provided with information areas arranged in accordance with a spiral or concentric track pattern, which record carrier is intended for recording and/or reproducing digitally coded information of a fixed bit frequency in the information areas via a radiation beam, which information areas have an optically detectable first periodic track modulation, the track position being modulated in a radial direction, for generating a radial tracking signal during recording and/or reproduction, said modulations being radially in phase, which apparatus for this purpose comprises an optical system for projecting a light beam onto said information areas, a detector for detecting the radiation which is reflected or transmitted by the recording areas, which detector is divided into two halves along a line corresponding to the track direction, and a read circuit for extracting a read-information signal from the detected radiation, characterized in that the apparatus comprises means for determining the difference between the radiation detected by two halves of the detector, means of extracting a signal of a frequency corresponding to the period of the periodic track modulation, means for generating an even higher harmonic of said extracted signal, means for the synchronous detection, by means of a reference signal, of a signal supplied by the detector in order to generate a radial tracking signal, and means for generating said reference signal in synchronism with said even higher harmonic.