Abstract: The invention relates to a laser device comprising a number of fiber amplifiers (3) delivering a number of optical waves, which is supplied by an oscillator (1) that delivers a signal wave, characterized in that said device comprises: a coherent source (4) emitting a coherent wave at a wavelength approximately equal to that of the signal wave and the propagation direction of which is inclined to the propagation direction of the optical waves output by the fiber amplifiers; means for making the coherent wave interfere with the optical waves output by the fiber amplifiers, and generating an interferogram consisting of an array of fringes; interferogram detection means (7), the relative positions of the fringes transcribing an inter-fiber phase law; a spatial phase modulator (2); and processing/display means (6) for processing the detected phase law and for displaying it on the spatial modulator, said spatial modulator being positioned so as to be able to be read by the signal wave and thus generate a phase-m

Abstract: The invention relates to a laser device comprising a number of fibre amplifiers (3) delivering a number of optical waves, which is supplied by an oscillator (1) that delivers a signal wave, characterized in that said device comprises: a coherent source (4) emitting a coherent wave at a wavelength approximately equal to that of the signal wave and the propagation direction of which is inclined to the propagation direction of the optical waves output by the fibre amplifiers; means for making the coherent wave interfere with the optical waves output by the fibre amplifiers, and generating an interferogram consisting of an array of fringes; interferogram detection means (7), the relative positions of the fringes transcribing an inter-fibre phase law; a spatial phase modulator (2); and processing/display means (6) for processing the detected phase law and for displaying it on the spatial modulator, said spatial modulator being positioned so as to be able to be read by the signal wave and thus generate a phase-m

Abstract: The invention relates to a radial slaving method and to a reproduction device implementing it for optical discs. In an optical head of a conventional reproduction device using a four-quadrant detector with four photodiode is distributed on either side of a direction parallel to the axis of the track, the individual signals of the photodiodes (d1 to d4) are combined in order to obtain read signals along the two diagonals (diag1, diag2) by subtraction (21, 22). A phase comparison signal circuit (100) makes it possible to construct a radial error signal (Sr) by measuring the phase shift of the diagonal read signals. The invention applies in particular to phase discs with slightly phase-shifting marks.

Abstract: The method in accordance with the invention consists in illuminating with coherent light a volume-wise at least partially scattering surface of reference objects under specified illumination conditions, in recording the speckle patterns thus obtained for various nominal values of illumination parameters and in a range of values around these nominal values, then, upon the verification of other objects or of the same objects, in illuminating these objects under the same nominal conditions and in comparing each time the speckle pattern thus obtained with those which were recorded and in retaining the objects if their speckle pattern corresponds to one of those that was recorded.

Abstract: The invention relates to a radial slaving method and to a reproduction device implementing it for optical discs. In an optical head of a conventional reproduction device using a four-quadrant detector with four photodiode is distributed on either side of a direction parallel to the axis of the track, the individual signals of the photodiodes (d1 to d4) are combined in order to obtain read signals along the two diagonals (diag1, diag2) by subtraction (21, 22). A phase comparison signal circuit (100) makes it possible to construct a radial error signal (Sr) by measuring the phase shift of the diagonal read signals. The invention applies in particular to phase discs with slightly phase-shifting marks.

Abstract: The invention relates to a system for reading a magnetic medium having several tracks of data which can be read in parallel with a detection device having at least as many detectors as there are tracks, making it possible to read simultaneously and at regular intervals a sample of data on each track. This system furthermore includes a processing circuit configured to receive each sample of data to be processed from each track together with sample of a first adjacent track and sample of a second adjacent track and to calculate the cross-talk affecting the sample of data to be processed due to the adjacent tracks. An integration circuit configured to receive the cross-talk value calculated by the processing circuit, integrates these values at each read time, and at subsequent read times. The systems also include a relative track-following control circuit configured to receive the result of integration of the integrator circuit and to supply a track-following control signal for the detection device.

Abstract: A clock circuit for the reading of sequential information elements includes a phase-locked loop for the control of the controlled oscillator. In the case of a reading system with n tracks, the phase computation circuit, the digital filter and the controlled oscillator each include as many memories (delay circuits R 1.1, . . . R 2.1, . . . R 3.1, . . . ) as there are samples of information elements (or information tracks) to be processed almost simultaneously. The invention finds particular application in the reading of high-density recording media.

Abstract: A process for reading binary information written on a carrier. The carrier has at least one track and the binary information is written onto the carrier at a frequency Fbit. The process includes the step of reading binary information at the sampling frequency F.sub.e to form a succession of successive read samples SAM(k) of the same track. SAM(k) is the read sample of order k, each read sample having a phase .phi.(k) lying between 0 and 2.pi.. The method further includes a step of interpolating to make it possible to calculate an interpolated sample I(k) with phase equal to .pi. which corresponds to read sample SAM(k) on the basis of the read sample and on the i+j read samples which bracket the original read sample SAM(k) such that:I(k)=a.sub.k-i SAM(k-i)+ . . . +a.sub.k SAM(k)+ . . . +a.sub.

Abstract: A recording/reading head for multitrack information media including magnetic tape recorders comprises a matrix of elementary heads positioned in rows and columns. The columns, and especially the neighboring columns, are not parallel to one another.

Abstract: This magnetic head essentially has at least one excitation conductor located below two layers made of magnetic material constituting the magnetic poles of the head and separated by a gap. The positioning of the conductor is such that it forms an angle different from 0.degree. or 90.degree. with respect to the direction of the gap. Different embodiments of the invention are provided for, notably with several conductors to set up a matrix-type control. Application to write/read magnetic heads.

Abstract: This system for receiving or reading digital serial information provides for the information to be sampled at regular intervals under the control of a local clock. It includes a table containing for each pair of values of consecutive information samples a measured phase value.

Abstract: A system for the reading of a multitrack recording medium comprising a device enabling the reading, on the width of each track, of a number n of information samples. The system includes a filter enabling the making of several combinations of several samples of a track, these combinations differing from one another by a shift equal to one or more samples; a sub-sampling circuit that chooses a determined combination from among the different combinations of a track under the control of a position predictor; a positional error computation circuit computing the positional error of the chosen combination and giving an error correction signal to the position predictor.

Abstract: System for recording/writing on a recording medium in which there are distributed, on the tracks, groups (G0) of tracks with positive continuous components and groups (G1) of tracks with negative continuous components. In reading, the values of the different signals are integrated for each track. Then, on the one hand, a first addition circuit S1 adds up the results of integration of the first tracks of each group of tracks and, secondly, a second addition circuit S2 adds up the results of integration of the last tracks of each group of tracks. A comparison circuit (CD) compares the results of additions of the two addition circuits to correct the track-following operation.

Abstract: A reading head has odd and even elemental areas for reading corresponding odd and even information segments that alternate to make up a frame of information on a record medium. The odd elemental areas provide a train of sequential odd information segments, each odd segment having cross-talk associated with the neighboring even segments which are on either side thereof when it is read from the record medium. Similarly, the even elemental areas provide a train of even information segments, each even segment having cross-talk associated with the odd segments which neighbored it on either side when it is read from the record medium. To correct for such cross-talk in both signal trains, both are fed to each of two cross-talk correcting circuits. These circuits derive needed adjacent segment information as to the cross-talk producing adjacent segments from one of the trains being fed thereto so as to process the segments of the other train being fed thereto for cross-talk correction.

Abstract: System for recording/writing on a recording medium in which there are distributed, on the tracks, groups (G0) of tracks with positive continuous components and groups (G1) of tracks with negative continuous components. In reading, the values of the different signals are integrated for each track. Then, on the one hand, a first addition circuit S1 adds up the results of integration of the first tracks of each group of tracks and, secondly, a second addition circuit S2 adds up the results of integration of the last tracks of each group of tracks. A comparison circuit (CD) compares the results of additions of the two addition circuits to correct the track-following operation.

Abstract: The magnetic recording head of the invention comprises an electrical conductor constituted by the poles themselves or by a magnetic shunt, which gets saturated when an electrical current is sent to it. It is thus possible to control the field at the gap and control the recording by this electrical current which acts by inhibition or validation of the writing, respectively.

Abstract: A method and system for preventing cross-talk during reproduction of data recorded on a high density recording medium. The method includes the steps of receiving signals from at least three consecutively parallel information tracks on a recording medium, determining first and second cross-talk coefficients representing a degree of cross-talk between the three parallel information tracks, filtering the first and second cross-talk coefficients, correcting the cross-talk between the first, second, and third information tracks in accordance with the first and second cross-talk coefficients, forming a difference between the first and second cross-talk coefficients and integrating this difference to generate a track following correction signal, and repeating the above steps for each of the information tracks on the recording medium.

Abstract: The invention relates to a method and system reading data recorded in the form of tracks on a magnetic recording medium. The recorded data is read by a row of read heads greater in number than a number of data tracks. The system of the invention does not require the read heads to follow the data tracks when reading recorded data, and allows a magnetic tape to be read even if the positions of the data tracks relative to the read head positions are unknown. The reading system of the present invention finds particular application in the area of reading high density recorded magnetic tapes.

Abstract: The read head according to the invention comprises a matrix network of elementary heads whose magnetic circuit comprises a magneto-resistive element. The different elements are electrically connected in columns and traversed by a current. Head selection lines enable the active line of heads to be selected. The read signal is collected on each column.

Abstract: In a device for the reading of a set of resistive elements (1.0, . . . , 1.n) in which an interrogation potential (V.sub.0) is applied at each instant to an element while a reference potential (v) is applied to the other elements, a stabilization circuit (CS) operates to keep the reading ports (L.0, . . . , L.n) at the reference potential. The present invention may find particular application to the reading of the elementary magnetoresistive heads of a magnetic reading head.