Abstract: A scanning device for scanning a record carrier is disclosed which comprises parallel, optically detectable tracks. The device comprises an optical system for focusing via the record carrier a main radiation beam, a first and a second auxiliary radiation beam on a radiation-sensitive main detector, a first auxiliary detector and a second auxiliary detector, respectively. The main detector and auxiliary detectors comprise each at least a first and a second sub-detector. A tracking control system controls a position of a read spot caused by the main radiation beam on the record carrier. In a first operating state first generating means for generating a first tracking error signal are used for generating a differential push-pull signal (Srepp) representative of a combination of mutual differences between detector signals from sub-detectors of individual detectors as an error tracking signal (SRE).

Abstract: An optical writing and/or reading device. A radiation source (10) generates a radiation beam (11). This radiation beam (11) is directed by an optical system onto a servotrack (4) of a rotating record carrier (1). The beam reflected via the record carrier is passed on to a push-pull detector (12). The servotrack has a periodical radial wobble whose frequency is modulated in accordance with a position-information signal. A signal-regaining circuit (17) regains the position-information signal from the push-pull signal. A balancing circuit (41, 42; 50, 51) adjusts a weighting the ratio between the detection signals which contribute to the difference signal. The DC component in the adapted push-pull signal is derived by means of a low-pass filter (44). In dependence upon the determined DC component, a circuit (45) sets the weighting ratio to a value at which the determined DC component is substantially zero.

Abstract: An apparatus and method for recording an information signal on a record carrier by means of a radiation beam which produces optically detectable marks in parallel track portions thereon having a substantially constant track pitch (q). The write intensity of the radiation beam is adjusted to an optimum level which results in a width (p) of the optical marks which corresponds to the track pitch (q). The optimum intensity level is determined by recording different test signals in adjoining track portions at various write intensities of the radiation beam, reading-out the recorded test signals, and detecting therefrom the write intensity at which signal components of one test signal no longer occur in another recorded test signal. Recording at the optimum write intensity results in a minimum block error rate (BLER) upon read-out of the recorded information signal.

Abstract: A method and device for recording signals on a record carrier with the aid of a radiation beam (15). The signals are recorded in the form of optically detectable marks in parallel tracks which have a substantially constant track pitch. The recording intensity of the radiation beam is set in such a way that with a "minimum" recording intensity information patterns are recorded with a low desired error rate "(Block) Error Rate". Furthermore, a method and device are described by which the "minimum" recording intensity of the radiation beam can be determined.

Abstract: An information recording device for recording digital information at a higher bit rate than that at which it is received. The difference in bit rate is compensated by an input buffer memory, read-out of a packet of information stored therein and recording thereof being periodically interrupted so as to maintain the filling level within a predetermined range. During each recording interruption, the recorded information pattern corresponding to the last recorded packet of information is read-out from the record carrier and the read-out signal is analyzed by an analysis circuit to derive an indication signal indicative of recording quality. The indication signal can be used to optimize the write parameters of the recording device, and also to determine whether re-recording of any or all of the last already recorded information packet should be performed before resuming read-out and recording of subsequent information packets from the buffer memory.

Abstract: An optical reading device for reading information recorded on a track of an optical record carrier, and an optical recording device for recording information on a track of an optical record carrier. Both devices use a radiation source to scan the record carrier (the reading device to read and the recording device to record) and a buffer memory which changes the rate in which the information which is read or to be written enters and leaves the buffer memory. In the reading device, the information read enters the buffer memory at a faster rate than it leave the buffer memory. In the recording device the opposite occurs. As a result, when the buffer memory of the reading device reaches a certain maximum filling level, information read in thereto is interrupted and so is use of the radiation source, such interrupts ending when the filling level of the buffer memory reaches a minimum level.

Abstract: A method and apparatus for recording an information signal on the recording layer of an optical record carrier by writing areas of modified optical properties in such layer. The layer is heated locally to a temperature above the write temperature by scanning with a laser beam whose power (P) is pulsed between a low level (Pl) and a write level (Ps) in accordance with the information signal. A signal (.alpha.(t)) which is indicative of the speed with which the write areas are formed, and therefore of the dimensions of such areas, is derived by a measurement circuit (50) from the radiation reflected from the recording layer. The measurement circuit is part of an adjustment circuit (12) which also includes a control circuit (60) which derives an adjustment signal (Ih) for a laser drive circuit (13) to control the write power (Ps) of the laser beam in accordance with the area forming-speed signal (.alpha.).

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 recording method and corresponding recording apparatus adjusts at least one record carrier-dependent recording parameter (I.sub.s) which influences the quality of the recorded information pattern (58, 59). In determining an optimum setting of the parameter (I.sub.s) a calibration area (21) is selected from a predetermined number of such areas on the record carrier. The selected area is then provided with test patterns recorded at different settings of the recording parameter, and based on the test patterns thus formed an optimum setting of such parameter is determined in accordance with a predetermined criterion. The parameter is adjusted in accordance with such optimum setting thereof during the recording of the information pattern (58, 59). Each time such a calibration is performed an auxiliary pattern is recorded in an auxiliary area (22) assigned to the calibration area employed, which auxiliary pattern indicates that test patterns are present in such calibration area.

Abstract: The invention relates to a magneto-optical recorder with magnetic-field modulation. It comprises a laser (8) for producing a light beam (6), an optical focussing system (9) for forming a focal spot (12), and a servo device (10) for maintaining the focal spot (12) in focus on the surface of a thermo-magnetic record carrier (4), and for supplying a correction signal (V.sub.c) which is representative of the position of the surface of said carrier. A current modulator modulates the current through a coil (15) of a magnetic head. A compensation device (7) is responsive to said correction signal (V.sub.c) to change a parameter influencing the field of the coil, in such a way that the field strength at the surface of said carrier (4) is substantially independant of the position of said surface.

Abstract: A scanning device including an optical head which generates three radiation beams for scanning a track in an information plane of a record carrier. The radiation from the record carrier produced by the respective beams is detected by respective detection systems. The resulting detection signals are combined to derive scanning control signals as well as a reference signal which corresponds to variations in and differences between the beam intensities. A divider circuit uses the reference signal to stabilize the control signals against such variations and differences in the beam intensities.

Abstract: An information recording device (FIG. 1) has write means (3, 8) for providing the record carrier (1) with information patterns (58, 59). The write means (3, 8) are adjustable. in determining the optimum adjustment a calibration procedure is carried out. For different settings of the write means (3, 8) information patterns (58, 59) are recorded. The optimum setting is determined on the basis of the recorded information patterns. The information recording device further comprises storage means for storing in a memory the determined optimum setting together with identification data which indicate for which combination of the recording device and a record carrier (1) the adjustment data has been determined. After a record carrier (1) has been loaded into the information recording device the occurrence of adjustment data for the relevant combination of a record carrier (1) and an information recording device is detected in the memory (1, 12).

Abstract: A read apparatus for reading a record carrier (1) having a concentric track pattern comprises a scanning device (2, 3) for reading the information, and a separator circuit (4) for extracting a periodic synchronizing signal (Ps) from the information read. By means of a servo system, which inter alia includes a drive motor (9) for driving the disc 1 and a control circuit (5), the rotational speed of the disc is controlled so as to maintain the periodic synchronizing signal (Ps) in synchronism with a reference signal (Pr). The circuit (9a) rejects those signal components in the control signal (U) for the motor (9) which are caused by an eccentric position of the center of rotation of the disc relative to the track pattern. This prevents these signal components from causing an unnecessary dissipation of electric power in the motor, yielding a substantial improvement in motor efficiency.