Abstract: A method is described for setting an optimum write power for recording information on an optical recording medium. A series of test patterns (20′, 21′, 22′) is written on the medium, the test patterns being written with different write powers. The values of the write power in subsequent test patterns form a symmetrical pattern. On reading the test patterns, the modulation of each read signal is determined. An optimum value of the write power is determined from the modulations.

Abstract: When writing a record carrier of an optically readable type, such as the rewritable CD-RW, the quality of the written information patterns is affected by contaminations of the surface due to dust and fingerprints. The inventors have found that the control of the writing power P should be inversely proportional to the measured reflection R, but less than an amount proportional thereto. A good control is achieved when P*.sqroot.R is maintained constant, and a control which is suitable for dealing with different contaminations can be achieved by maintaining P*R.sup.x constant, in which x has a value of between 0.5 and 0.8. The way in which the reflection R can be measured from the signal coming from side spots formed next to the track to be scanned is also described.

Abstract: Method of deriving a quality signal for a binary read signal having bit cells of constant length, and reading and recording devices which employ that method. During a reading process, an information pattern of optically detectable effects, representing certain of the bit cells, is scanned. A read signal is generated therefrom in which first read signal portions that exceed a reference value correspond to the effects. The quality signal is derived (in an analysis circuit) from the first read signal portions based on a measure of the deviation of first read signal portions corresponding to a particular length or mutual differences between length deviation of first read signal portions of different lengths. The quality signal can be used for adapting a recording strategy used in the recording of information, or for setting an equalizing filter.

Abstract: A magneto-optical recording apparatus provided with a magnetic field modulator (8). The magnetic-field modulator (8) has a field coil (18) for generating a magnetic field and switches (11,12,15,16,22) for coupling at least one terminal (17) of the magnet coil (18) to a first potential point (10) at a first potential (Vp) or a second potential point (14) at a second potential (Vn) depending on the logic value of a control signal (vs), in order to produce in the field coil an alternating current whose polarity depends on the logic value. The field coil (18) is arranged in a parallel resonant circuit (18,21). The switches have means (12,16) for inhibiting, after the terminal (17) has been uncoupled from one of the potential points (10,14), current supply from the other potential point for a time interval corresponding to half the resonant period of the resonant circuit (18,21). This magnetic-field modulator provides a very rapid reversal of the current through the field coil.

Abstract: A method of and apparatus (FIG. 4) for recording an information signal (Vi), in particular an EFM-modulated signal, are revealed, which information signal comprises time-code signals which alternate with first time-synchronization signals. The record carrier (1) which is employed is provided with a preformed servo track (4) which exhibits a periodic track modulation whose frequency is modulated in conformity with the position-information signal (FIG. 2). The position-information signal (FIG. 2) comprises position-code signals (12) which alternate with position-synchronization signals (11). During recording a fixed phase relationship between the time-synchronization signals and the position-synchronization signals (11) is maintained, so that the portion (141) of the servo track (4) in which the time-synchronization signals are recorded are situated at fixed positions relative to the servo-track portions (140) which represent the position-synchronization signals (11).