EP0591479A1 - Method and device for optically reading a sound recording on a grooved recording medium - Google Patents

Method and device for optically reading a sound recording on a grooved recording medium

Info

Publication number
EP0591479A1
EP0591479A1 EP93903773A EP93903773A EP0591479A1 EP 0591479 A1 EP0591479 A1 EP 0591479A1 EP 93903773 A EP93903773 A EP 93903773A EP 93903773 A EP93903773 A EP 93903773A EP 0591479 A1 EP0591479 A1 EP 0591479A1
Authority
EP
European Patent Office
Prior art keywords
fiber
groove
light
optical
disc
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93903773A
Other languages
German (de)
French (fr)
Inventor
Juraj Poliak
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ecole Polytechnique Federale de Lausanne EPFL
Original Assignee
Ecole Polytechnique Federale de Lausanne EPFL
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ecole Polytechnique Federale de Lausanne EPFL filed Critical Ecole Polytechnique Federale de Lausanne EPFL
Publication of EP0591479A1 publication Critical patent/EP0591479A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1384—Fibre optics
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
    • G11B11/16—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by mechanical cutting, deforming or pressing
    • G11B11/18—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by mechanical cutting, deforming or pressing with reproducing by optical means
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
    • G11B7/005—Reproducing

Definitions

  • the present invention relates to a process for the optical reading of a sound recording on an engraved support comprising at least one groove wound in a spiral on a disc, or in a helix on a cylinder, driven in rotation about an axis.
  • the present invention proposes to provide a non-destructive method for reading these old recordings using optical techniques.
  • the invention aims to overcome all the drawbacks of known techniques and to develop a device capable of implementing the method developed.
  • the method of the invention is characterized in that an optical fiber is arranged substantially tangentially in said groove so that modulations etched in said groove cause displacements of the end of this fiber, in this that light is injected into said fiber, in that the light leaving the end of said fiber forms a light spot, in that an image of said spot is collected on an optical position sensor, and in that at least one component of the movements of said spot is analyzed in order to read said recording.
  • the light leaving said fiber and forming the light spot is reflected at the end of the fiber and leaves laterally of the fiber.
  • the movements of the reflected light spot are analyzed along two orthogonal axes and the results of this analysis are used, on the one hand to read said recording and on the other hand to control the movements of the fiber so that it follows the groove of said engraved support.
  • the signal corresponding to the component is preferably broken down along one of the axes into two signals, one of which provides the sound recording engraved on the support and the other of which makes it possible to control the lateral displacement of the fiber to follow the groove, and preferably using the signal corresponding to the component along the other axis to control the height of the anchor point of the fiber relative to said engraved support.
  • the orthogonal axes are respectively parallel and perpendicular to the surface of the engraved support.
  • the orthogonal axes are arranged at 45 ° relative to the median plane passing through the bottom of the groove.
  • the signal providing the sound recording and the signal making it possible to control the lateral displacement of the fiber advantageously correspond to the X axis parallel to the plane of the disc
  • the signal making it possible to control the height of the point fiber anchoring advantageously corresponds to the axis Y perpendicular to the plane of the disc.
  • the device for implementing the method is characterized in that it comprises an optical fiber disposed substantially tangentially in said groove, means for injecting light into the fiber, an optical system for collecting light leaving the fiber, an optical position sensor on which the optical system produces an image of the light spot formed by the light leaving the fiber, and means for analyzing the signals delivered by the position sensor and deducing therefrom the movements of the light spot in at least one direction for reading said recording.
  • the optical fiber has a free end disposed in the groove, this end being arranged to reflect the light guided by its heart and to return it laterally with respect to its axis.
  • the device preferably comprises two servo motors, one for moving the fiber laterally so that it follows the groove wound in a spiral on a disc or in a helix on a cylinder and the other so that it is maintained at a level substantially constant with respect to the surface of the disc.
  • the optical position sensor comprises four electrodes corresponding in pairs to the two orthogonal axes.
  • FIG. 1 represents a perspective view of a section of furrow of an engraved support
  • FIG. 2 represents a cross-sectional view of this groove and the position of a conventional needle used for reading this recording
  • FIG. 3 represents a view in longitudinal section of an end of optical fiber used in the context of the method according to the invention
  • FIG. 4 represents a cross-sectional view of the groove and of the optical fiber used in the context of the method of the invention
  • FIG. 5 is a schematic view illustrating the principle on which the method of the invention is based
  • FIG. 6 represents a block diagram of the electronic circuit analyzing the light spot obtained on the optical position sensor
  • FIG. 7 represents a detailed view of part of the circuit of FIG. 6,
  • FIG. 8 represents a detailed view of another part of the circuit of FIG. 6, and
  • FIG. 9 represents a view illustrating one of the advantages of the method according to the invention.
  • the groove of a phonographic record which has been the only sound recording medium used for many years, has the shape of a spiral groove engraved directly or produced by pressing with a matrix. As shown in Figures 1 and 2, this groove 10 has a V-shaped profile open for example at 90 °. The lateral faces of this V are then inclined at 45 th relative to the vertical and are engraved either identically on the two faces 11 and 12 when the recording is monophonic, or differently when the recording is stereophonic. In the latter case, the face 11 corresponds to the right track and the face 12 corresponds to the left track.
  • the needle or stylet 13 follows the groove of the disc driven in rotation by a turntable turntable and bears on the lateral faces of this groove in zones 11a and 12a which are located near the bottom.
  • An electromagnetic, electrodynamic or piezoelectric cell is mechanically coupled to the needle and converts the movements of the latter into electrical signals.
  • optical fiber 14- see FIG. 3
  • This conventional technique is totally abandoned within the framework of the process defined above and the needle is replaced by an optical fiber 14- (see FIG. 3), or more exactly a section of optical fiber which is disposed substantially tangentially or at an angle. weak in the groove 10.
  • This fiber comprises a core 15 conducting light surrounded by an envelope 16, commonly called “cladding”. Its end 17 is cut in such a way that the light injected into the heart 15 undergoes a total reflection on the fiber-air diopter and is returned laterally through the envelope
  • Figure 4- shows the optical fiber seen in section in the groove 10.
  • the horizontal displacements "X” are due to the modulation of the groove, that is to say that they correspond to the recording engraved in the groove
  • the vertical displacements "Y" correspond to the flatness defects of the disc.
  • the reflected beam 18 corresponding to arrow A is focused by an optical system 19 ' on an optical position sensor 20, in the form of a light spot 21.
  • the movement of this light spot 21 according to the X axis corresponds to the horizontal displacement of the fiber and the displacement of the light spot 21 along the Y axis corresponds to the vertical displacement of this fiber.
  • the sensor 20 supplies two currents per axis. If the light spot is in the center of the sensor, these two currents are equal but with opposite signs.
  • the circuit illustrated in FIG. 6 in the form of a block diagram represents the sensor 20 provided with two position electrodes 20x1 and 20 X 2 for detecting the position of the spot 21 on the X axis and two position electrodes 20 y ⁇ and 20 y2 to detect the position of spot 21 on the Y axis.
  • These detectors provide electrical signals in the form of intensities I x ⁇ , I xZ , I y and I y 2 which are converted into voltage , U x2 , U y x and U Y 2.
  • I o is the total intensity of the current supplied by the detectors on the X axis
  • the currents Ixi and l ⁇ 2 are converted into voltages Uxi and U 2
  • R represents the load resistance
  • the two signals Ux and U y are independent of the brightness of spot 21.
  • Signal X corresponds to the sound recorded by the groove. It is also used to control the horizontal displacement of the optical head, that is to say of the fiber, one free end of which is housed in the groove and the other end of which is anchored on a support controlled by two motors 22 and 23 one of which 22 moves the optical head horizontally and the other of which 23 generates the vertical guide.
  • the Y-axis signals correspond to sound.
  • it is also possible to use the method for playing stereophonic discs by tilting the X and Y axes at 4-5 ° relative to the plane of the disc.
  • the signal X is divided into two parts (see FIG. 7).
  • the part 26a of the signal which has passed through a low-pass filter 24 is used to control the lateral displacement of the fiber to ensure the "tracking" of the groove and to maintain on average the light spot in the middle of the X axis. A this effect, this part of the signal is transmitted to the motor 22 through a regulation circuit 27.
  • the part 26b of the signal which has passed through a high-pass filter 25 having a cut-off frequency of the order of 20 Hz, corresponds to the oscillations side of the light spot around the middle central position.
  • This part 26b of the signal corresponds to the sound recording which can be reproduced by a loudspeaker 28.
  • the signal Y corresponds to the vertical displacement of the fiber which results from the flatness defects of the disc.
  • This signal passes through a low-pass filter 29 with a cut-off frequency of 10 Hz and is directed to the motor 23 via a regulation circuit 30 which controls the vertical movement of the fiber to maintain the light spot in the middle of the Y axis.
  • the stress that the end of the fiber exerts on the groove is of the order of 50 to 60 mg, that is to say much lower than that exerted by any conventional needle or stylus .
  • the reduction in stress is at least a factor of 40 to 50. As a result, it becomes possible to read cracked and cracked discs.
  • FIG. 9 makes it possible to compare the reading positions of a conventional needle and of the optical fiber. Due to the different geometry of these two elements and the appropriate choice of the diameter of the fiber, the contact zones of said elements with the faces 11 and 12 of the groove 10 are not located in the same places. The contact areas 11a and 12a of the needle are often damaged due to the multiple readings of the disc. The contact areas 11b and 12b of the optical fiber 14 are located higher than the previous ones, that is to say in places where there has practically never been contact with a needle. This eliminates a significant part of the parasitic noise.

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Recording Or Reproduction (AREA)
  • Optical Head (AREA)

Abstract

Le dispositif pour la mise en oeuvre du procédé de lecture optique d'un enregistrement sonore sur un support gravé comportant au moins un sillon enroulé en spirale sur un disque, ou en hélice sur un cylindre, entraîné en rotation autour d'un axe, comporte une fibre optique (14) agencée pour qu'une de ses extrémités réfléchisse de la lumière injectée dans cette fibre, et disposée sensiblement tangentiellement dans ledit sillon (10) de telle manière que les modulations gravées dans ledit sillon engendrent des déplacements X et Y de cette fibre, et des moyens pour injecter de la lumière dans ladite fibre. Le faisceau réfléchi (18) de lumière sortant de la fibre optique est focalisé par un système optique (19) sur un capteur optique de position (20) sous la forme d'une tache lumineuse (21), et l'on analyse au moins une composante de cette lumière pour lire ledit enregistrement.The device for implementing the method of optical reading of a sound recording on an engraved medium comprising at least one groove wound in a spiral on a disc, or in a helix on a cylinder, driven in rotation around an axis, comprises an optical fiber (14) arranged so that one of its ends reflects light injected into this fiber, and arranged substantially tangentially in said groove (10) in such a way that the modulations etched in said groove generate X and Y displacements of this fiber, and means for injecting light into said fiber. The reflected beam (18) of light emerging from the optical fiber is focused by an optical system (19) onto an optical position sensor (20) in the form of a light spot (21), and at least a component of this light to read said recording.

Description

PROCEDE ET DISPOSITIF DE LECTURE OPTIQUE D'UN ENREGIS¬ TREMENT SONORE SUR UN SUPPORT GRAVEMETHOD AND DEVICE FOR OPTICALLY READING A SOUND RECORDING ON A GRAVE MEDIUM
La présente invention concerne un procédé de lecture optique d'un enregistrement sonore sur un - support gravé comportant au moins un sillon enroulé en spirale sur un disque, ou en hélice sur un cylindre , entraîné en rotation autour d'un axe.The present invention relates to a process for the optical reading of a sound recording on an engraved support comprising at least one groove wound in a spiral on a disc, or in a helix on a cylinder, driven in rotation about an axis.
Elle concerne également un dispositif pour la mise en oeuvre de ce procédé.It also relates to a device for implementing this method.
Il existe dans les archives de toutes les stations de radio, un volume important de disques et autres supports gravés tels que par exemple des cylindres gravés dans de la cire, qui ne peuvent plus être lus de nos jours avec les équipements de lecture dont on dispose ou qui, s'ils sont lus avec le matériel ancien encore disponible, subissent des dégradations irrémédiables . De 1885, année de l'invention du phonographe par Thomas Edison, jusqu'à l'apparition des enregistrements sur supports magnétiques , les seuls supports d'enregistrement des voix et de la musique étaient les cylindres et les disques gravés . Les enregistrements directs effectués notamment par les journalistes des stations de radiodiffusion, étaient faits sur disques . C'est pourquoi de très nombreux enregistrements , qui constituent aujourd'hui de véritables documents historiques , sont devenus inutilisables et par conséquent perdus si une solution n'est pas trouvée pour les reproduire sur des supports plus actuels . En effet les cylindres de cire ont subi des altérations qui les ont rendu fragiles ou les ont fissuré, ce qui rend toute lecture par une aiguille rigide impossible ou destructrice.In the archives of all radio stations, there is a large volume of discs and other engraved media such as, for example, cylinders engraved in wax, which can no longer be read today with the reading equipment available. or which, if read with the old material still available, undergo irreparable damage. From 1885, the year of the invention of the phonograph by Thomas Edison, until the appearance of recordings on magnetic media, the only media for recording voices and music were cylinders and burned discs. Direct recordings made in particular by journalists of broadcasting stations were made on discs. This is why very many recordings, which today constitute true historical documents, have become unusable and consequently lost if a solution is not found to reproduce them on more current supports. Indeed, the wax cylinders have undergone alterations which have made them fragile or have cracked them, which makes any reading by a rigid needle impossible or destructive.
Les disques étaient anciennement réalisés au moyen d'une plaque métallique recouverte d'une couche de résine. Au fil des ans , la couche de résine s'est fissurée et des plages entières se sont décalées les unes par rapport aux autres de sorte que des tronçons de sillons ne se correspondent plus. Une lecture de ces enregistrements est quasiment exclue avec des aiguilles de phonographe qui risquent d'arracher des particules de résine et par conséquent de détériorer définitivement ces enregistrements .The discs were formerly made using a metal plate covered with a layer of resin. Over the years, the resin layer has cracked and entire areas have shifted relative to each other so that sections of grooves no longer match. A reading of these recordings is almost excluded with phonograph needles which risk tearing off particles of resin and consequently permanently damaging these recordings.
La présente invention se propose de fournir un procédé non destructif de lecture de ces enregistrements anciens en utilisant des techniques optiques .The present invention proposes to provide a non-destructive method for reading these old recordings using optical techniques.
Des tentatives ont déjà été faites dans ce sens , mais tous les procédés qui consistent à éclairer directement les sillons et à recueillir la lu¬ mière réfléchie par la surface de ce sillon, n'aboutissent pas à des ré¬ sultats satisfaisants car ils répercutent les détériorations subies par le support sans pouvoir éliminer des signaux obtenus , les parasites dus à ces détériorations .Attempts have already been made in this direction, but all the processes which consist in directly illuminating the furrows and in collecting the light reflected by the surface of this furrow, do not lead to satisfactory results because they reflect the deterioration undergone by the support without being able to eliminate from the signals obtained, the parasites due to these deteriorations.
L'invention a pour but de pallier tous les inconvénients des techniques connues et de développer un dispositif susceptible de mettre en oeuvre le procédé mis au point.The invention aims to overcome all the drawbacks of known techniques and to develop a device capable of implementing the method developed.
Dans ce but, le procédé de l'invention est caractérisé en ce que l'on dispose une fibre optique sensiblement tangentiellement dans ledit sillon de telle manière que des modulations gravées dans ledit sillon engendrent des déplacements de l'extrémité de cette fibre, en ce que l'on injecte de la lumière dans ladite fibre, en ce que la lumière sortant de l'extrémité de ladite fibre forme une tache lumineuse, en ce que l'on recueille une image de ladite tache sur un capteur optique de position, et en ce que l'on analyse au moins une composante des mouvements de ladite tache pour lire ledit enregistrement.For this purpose, the method of the invention is characterized in that an optical fiber is arranged substantially tangentially in said groove so that modulations etched in said groove cause displacements of the end of this fiber, in this that light is injected into said fiber, in that the light leaving the end of said fiber forms a light spot, in that an image of said spot is collected on an optical position sensor, and in that at least one component of the movements of said spot is analyzed in order to read said recording.
Selon un mode de réalisation préféré, la lumière sortant de ladite fibre et formant la tache lumineuse est réfléchie à l'extrémité de la fibre et sort latéralement de la fibre.According to a preferred embodiment, the light leaving said fiber and forming the light spot is reflected at the end of the fiber and leaves laterally of the fiber.
Dans le cadre de ce mode de réalisation préféré, l'on analyse les mouvements de la tache lumineuse réfléchie selon deux axes orthogonaux et l'on exploite les résultats de cette analyse, d'une part pour lire ledit enregistrement et d'autre part pour commander les déplacements de la fibre pour qu' elle suive le sillon dudit support gravé.In the context of this preferred embodiment, the movements of the reflected light spot are analyzed along two orthogonal axes and the results of this analysis are used, on the one hand to read said recording and on the other hand to control the movements of the fiber so that it follows the groove of said engraved support.
Pour analyser les mouvements de la tache lumineuse, on décompose de préférence le signal correspondant à la composante selon l'un des axes en deux signaux dont l'un fournit l'enregistrement sonore gravé sur le support et dont l'autre permet d'asservir le déplacement latéral de la fibre pour suivre le sillon, et l'on utilise de préférence le signal correspondant à la composante selon l'autre axe pour commander la hauteur du point d'ancrage de la fibre par rapport audit support gravé.To analyze the movements of the light spot, the signal corresponding to the component is preferably broken down along one of the axes into two signals, one of which provides the sound recording engraved on the support and the other of which makes it possible to control the lateral displacement of the fiber to follow the groove, and preferably using the signal corresponding to the component along the other axis to control the height of the anchor point of the fiber relative to said engraved support.
Dans une première variante, les axes orthogonaux sont respectivement parallèle et perpendiculaire à la surface du support gravé.In a first variant, the orthogonal axes are respectively parallel and perpendicular to the surface of the engraved support.
Dans une deuxième variante, les axes orthogonaux sont disposés à 45° par rapport au plan médian passant par le fond du sillon.In a second variant, the orthogonal axes are arranged at 45 ° relative to the median plane passing through the bottom of the groove.
Pour un support du type disque, le signal fournissant l'enregistrement sonore et le signal permettant d'asservir le déplacement latéral de la fibre correspondent avantageusement à l'axe X parallèle au plan du disque, et le signal permettant de commander la hauteur du point d'ancrage de la fibre correspond avantageusement à l'axe Y perpendiculaire au plan du disque.For a disc-type support, the signal providing the sound recording and the signal making it possible to control the lateral displacement of the fiber advantageously correspond to the X axis parallel to the plane of the disc, and the signal making it possible to control the height of the point fiber anchoring advantageously corresponds to the axis Y perpendicular to the plane of the disc.
Dans ce but également, le dispositif pour la mise en oeuvre du procédé est caractérisé en ce qu'il comporte une fibre optique disposée sensiblement tangentiellement dans ledit sillon, des moyens pour injecter de la lumière dans la fibre, un système optique pour recueillir la lumière sortant de la fibre, un capteur optique de position sur lequel le système optique produit une image de la tache lumineuse formée par la lumière sortant de la fibre, et des moyens pour analyser les signaux délivrés par le capteur de position et en déduire les mouvements de la tache lumineuse selon au moins une direction pour lire ledit enregistrement. Selon un mode de construction préféré, la fibre optique a une extrémité libre disposée dans le sillon, cette extrémité étant agencée pour réfléchir la lumière guidée par son coeur et pour la renvoyer latéralement par rapport à son axe.For this purpose also, the device for implementing the method is characterized in that it comprises an optical fiber disposed substantially tangentially in said groove, means for injecting light into the fiber, an optical system for collecting light leaving the fiber, an optical position sensor on which the optical system produces an image of the light spot formed by the light leaving the fiber, and means for analyzing the signals delivered by the position sensor and deducing therefrom the movements of the light spot in at least one direction for reading said recording. According to a preferred construction method, the optical fiber has a free end disposed in the groove, this end being arranged to reflect the light guided by its heart and to return it laterally with respect to its axis.
Le dispositif comporte de préférence deux moteurs d'asservissement, l'un pour déplacer latéralement la fibre pour qu'elle suive le sillon enroulé en spirale sur un disque ou en hélice sur un cylindre et l'autre pour qu'elle se maintienne à un niveau sensiblement constant par rapport à la surface du disque.The device preferably comprises two servo motors, one for moving the fiber laterally so that it follows the groove wound in a spiral on a disc or in a helix on a cylinder and the other so that it is maintained at a level substantially constant with respect to the surface of the disc.
Selon une forme de construction particulièrement avantageuse, le capteur optique de position comporte quatre électrodes correspondant par paire aux deux axes orthogonaux.According to a particularly advantageous form of construction, the optical position sensor comprises four electrodes corresponding in pairs to the two orthogonal axes.
La présente invention sera mieux comprise en référence à la description d'un exemple de réalisation et du dessin annexé dans lequel :The present invention will be better understood with reference to the description of an exemplary embodiment and the attached drawing in which:
la figure 1 représente une vue en perspective d'un tronçon de sillon d'un support gravé,FIG. 1 represents a perspective view of a section of furrow of an engraved support,
la figure 2 représente une vue en coupe transversale de ce sillon et la position d'une aiguille classique utilisée pour la lecture de cet enregistrement ,FIG. 2 represents a cross-sectional view of this groove and the position of a conventional needle used for reading this recording,
la figure 3 représente une vue en coupe longitudinale d'une extrémité de fibre optique utilisée dans le cadre du procédé selon l'invention,FIG. 3 represents a view in longitudinal section of an end of optical fiber used in the context of the method according to the invention,
la figure 4 représente une vue en coupe transversale du sillon et de la fibre optique utilisée dans le cadre du procédé de l'invention,FIG. 4 represents a cross-sectional view of the groove and of the optical fiber used in the context of the method of the invention,
la figure 5 est une vue schématique illustrant le principe sur lequel est basé le procédé de l'invention, la figure 6 représente un schéma-bloc du circuit électronique analysant la tache lumineuse obtenue sur le capteur optique de position,FIG. 5 is a schematic view illustrating the principle on which the method of the invention is based, FIG. 6 represents a block diagram of the electronic circuit analyzing the light spot obtained on the optical position sensor,
la figure 7 représente une vue détaillée d'une partie du circuit de la figure 6,FIG. 7 represents a detailed view of part of the circuit of FIG. 6,
la figure 8 représente une vue détaillée d'une autre partie du circuit de la figure 6, etFIG. 8 represents a detailed view of another part of the circuit of FIG. 6, and
la figure 9 représente une vue illustrant un des avantages du procédé selon l'invention.FIG. 9 represents a view illustrating one of the advantages of the method according to the invention.
Le sillon d'un disque phonographique, qui a été pendant de longues années le seul support d'enregistrement des sons utilisé, présente la forme d'une gorge en spirale gravée directement ou fabriquée par pressage au moyen d'une matrice. Comme le montrent les figures 1 et 2, cette gorge 10 à un profil en V ouvert par exemple à 90° . Les faces latérales de ce V sont alors inclinées à 45 e par rapport à la verticale et sont gravées soit de façon identique sur les deux faces 11 et 12 lorsque l'enregistrement est monophonique, soit de façon différente lorsque l'enregistrement est stéréophonique. Dans ce dernier cas, la face 11 correspond à la voie droite et la face 12 correspond à la voie gauche.The groove of a phonographic record, which has been the only sound recording medium used for many years, has the shape of a spiral groove engraved directly or produced by pressing with a matrix. As shown in Figures 1 and 2, this groove 10 has a V-shaped profile open for example at 90 °. The lateral faces of this V are then inclined at 45 th relative to the vertical and are engraved either identically on the two faces 11 and 12 when the recording is monophonic, or differently when the recording is stereophonic. In the latter case, the face 11 corresponds to the right track and the face 12 corresponds to the left track.
L'aiguille ou stylet 13 suit le sillon du disque entraîné en rotation par une platine de tourne-disque et prend appui sur les faces latérales de ce sillon dans des zones lia et 12a qui se localisent à proximité du fond. Une cellule électromagnétique, électrodynamique ou piézo- électrique est couplée mécaniquement à l'aiguille et convertit les mouvements de celle-ci en signaux électriques.The needle or stylet 13 follows the groove of the disc driven in rotation by a turntable turntable and bears on the lateral faces of this groove in zones 11a and 12a which are located near the bottom. An electromagnetic, electrodynamic or piezoelectric cell is mechanically coupled to the needle and converts the movements of the latter into electrical signals.
Cette technique classique est totalement abandonnée dans le cadre du procédé défini ci-dessus et l'aiguille est remplacée par une fibre optique 14- (voir figure 3) , ou plus exactement un tronçon de fibre optique qui est disposé sensiblement tangentiellement ou sous un angle faible dans la gorge 10. Cette fibre comporte un coeur 15 conducteur de la lumière entourée d'une enveloppe 16, couramment appelée "cladding" . Son extrémité 17 est coupée de telle manière que la lumière injectée dans le coeur 15 subisse une réflexion totale sur le dioptre fibre-air et soit renvoyée latéralement à travers l'enveloppeThis conventional technique is totally abandoned within the framework of the process defined above and the needle is replaced by an optical fiber 14- (see FIG. 3), or more exactly a section of optical fiber which is disposed substantially tangentially or at an angle. weak in the groove 10. This fiber comprises a core 15 conducting light surrounded by an envelope 16, commonly called "cladding". Its end 17 is cut in such a way that the light injected into the heart 15 undergoes a total reflection on the fiber-air diopter and is returned laterally through the envelope
16, comme le montre la flèche A. On pourrait également prévoir de métalliser l'extrémité de cette fibre pour constituer un réflecteur.16, as shown in arrow A. One could also plan to metallize the end of this fiber to form a reflector.
La figure 4- montre la fibre optique vue en coupe dans la gorge 10. Les déplacements horizontaux "X" sont dus à la modulation de la gorge, c'est-à-dire qu'ils correspondent à l'enregistrement gravé dans le sillon, et les déplacements verticaux "Y" correspondent aux défauts de planéité du disque.Figure 4- shows the optical fiber seen in section in the groove 10. The horizontal displacements "X" are due to the modulation of the groove, that is to say that they correspond to the recording engraved in the groove , and the vertical displacements "Y" correspond to the flatness defects of the disc.
Comme le montre la figure 5, le faisceau réfléchi 18 correspondant à la flèche A est focalisé par un système optique 19 ' sur un capteur optique de position 20, sous la forme d'une tache lumineuse 21. Le déplacement de cette tache lumineuse 21 selon l'axe X correspond au déplacement horizontal de la fibre et le déplacement de la tache lumineuse 21 selon l'axe Y correspond au déplacement vertical de cette fibre. Le capteur 20 fournit deux courants par axe. Si la tache lumineuse est au centre du capteur, ces deux courants sont égaux mais de signes opposés.As shown in FIG. 5, the reflected beam 18 corresponding to arrow A is focused by an optical system 19 ' on an optical position sensor 20, in the form of a light spot 21. The movement of this light spot 21 according to the X axis corresponds to the horizontal displacement of the fiber and the displacement of the light spot 21 along the Y axis corresponds to the vertical displacement of this fiber. The sensor 20 supplies two currents per axis. If the light spot is in the center of the sensor, these two currents are equal but with opposite signs.
Le circuit illustré par la figure 6 sous forme d'un schéma-bloc représente le capteur 20 pourvu de deux électrodes de position 20x1 et 20X2 pour détecter la positon de la tache 21 sur l'axe X et deux électrodes de position 20yχ et 20y2 pour détecter la positon de la tache 21 sur l'axe Y. Ces détecteurs fournissent des signaux électriques sous la forme d'intensités Ixι , IxZ, Iy et Iy2 qui sont converties en tension , Ux2, Uyx et UY2. On additionne et on soustrait ces valeurs, pour obtenir respectivement les signaux Uxi - UχZ, U, A + Ux-2 et Uyi - Uy2, Uyi + Uy2 pour calculer finalement les rapports :The circuit illustrated in FIG. 6 in the form of a block diagram represents the sensor 20 provided with two position electrodes 20x1 and 20 X 2 for detecting the position of the spot 21 on the X axis and two position electrodes 20 y χ and 20 y2 to detect the position of spot 21 on the Y axis. These detectors provide electrical signals in the form of intensities I x ι, I xZ , I y and I y 2 which are converted into voltage , U x2 , U y x and U Y 2. We add and subtract these values, to obtain respectively the signals Uxi - Uχ Z , U, A + Ux-2 and Uyi - U y 2, Uyi + U y 2 for finally calculate the ratios:
qui permettent de définir à la fois le signal sonore enregistré et le paramètres de positionnement de la fibre optique, comme décrit plu en détail ci-dessous . which allow you to define both the recorded sound signal and the optical fiber positioning parameters, as described in more detail below.
Les courants produits par le capteur optique de position sont : I*ι = o L/2 + x et Iχ2 = o L/2 - x L L où : L est la longueur utile sur l'axe X ,The currents produced by the optical position sensor are: I * ι = o L / 2 + x and Iχ 2 = o L / 2 - x LL where: L is the useful length on the X axis,
I o est l'intensité totale du courant fourni par les détecteurs d l'axe X , x est la position de la tache lumineuse sur l'axe X, l'origine étan localisée au centre du capteur, de sorte que x = 0 si la tache es parfaitement centrée.I o is the total intensity of the current supplied by the detectors on the X axis, x is the position of the light spot on the X axis, the etan origin located at the center of the sensor, so that x = 0 if the spot is perfectly centered.
Les courants Ixi et lχ2 sont convertis en tensions Uxi et U 2The currents Ixi and lχ 2 are converted into voltages Uxi and U 2
où : or :
R représente la résistance de charge.R represents the load resistance.
De la même manière, on obtient la valeur de Uy pour l'axe Y :In the same way, we obtain the value of U y for the Y axis:
Uy = ûUy = 2χ ΣUy LU y = ûU y = 2χ ΣU y L
Les deux signaux Ux et Uy sont indépendants de la luminosité de l tache 21. Le signal X correspond au son enregistré par le sillon. I est également utilisé pour commander le déplacement horizontal de l tête optique, c'est-à-dire de la fibre dont une extrémité libre es logée dans le sillon et dont l'autre extrémité est ancrée sur u support commandé par deux moteurs 22 et 23 dont l'un 22 déplace l tête optique horizontalement et dont l'autre 23 génère le guidag vertical. Pour des supports à gravure verticale, comme par exemple les cylindres phonographiques, les signaux de l'axe Y correspondent au son. En outre, il est également possible d'utiliser le procédé pour lire les disques stéréophoniques en inclinant les axes X et Y à 4-5° par rapport au plan du disque.The two signals Ux and U y are independent of the brightness of spot 21. Signal X corresponds to the sound recorded by the groove. It is also used to control the horizontal displacement of the optical head, that is to say of the fiber, one free end of which is housed in the groove and the other end of which is anchored on a support controlled by two motors 22 and 23 one of which 22 moves the optical head horizontally and the other of which 23 generates the vertical guide. For vertical engraving media, such as phonographic cylinders, the Y-axis signals correspond to sound. In addition, it is also possible to use the method for playing stereophonic discs by tilting the X and Y axes at 4-5 ° relative to the plane of the disc.
On notera que le signal X est divisé en deux parties (voir figure 7) . La partie 26a du signal qui a passé à travers un filtre passe-bas 24 est utilisée pour piloter le déplacement latéral de la fibre pour assurer le "suivi" du sillon et maintenir en moyenne la tache lumineuse au milieu de l'axe X. A cet effet, cette partie du signal est transmise au moteur 22 à travers un circuit de régulation 27. La partie 26b du signal qui a traversé un filtre passe-haut 25 présentant une fréquence de coupure de l'ordre de 20 Hz, correspond aux oscillations latérales de la tache lumineuse autour de la position centrale moyenne. Cette partie 26b du signal correspond à l'enregistrement sonore qui peut être reproduit par un haut-parleur 28.It will be noted that the signal X is divided into two parts (see FIG. 7). The part 26a of the signal which has passed through a low-pass filter 24 is used to control the lateral displacement of the fiber to ensure the "tracking" of the groove and to maintain on average the light spot in the middle of the X axis. A this effect, this part of the signal is transmitted to the motor 22 through a regulation circuit 27. The part 26b of the signal which has passed through a high-pass filter 25 having a cut-off frequency of the order of 20 Hz, corresponds to the oscillations side of the light spot around the middle central position. This part 26b of the signal corresponds to the sound recording which can be reproduced by a loudspeaker 28.
Le signal Y correspond au déplacement vertical de la fibre qui résulte des défauts de planéité du disque. Ce signal traverse un filtre passe- bas 29 avec une fréquence de coupure de 10 Hz et est dirigé sur le moteur 23 par l'intermédiaire d'un circuit de régulation 30 qui pilote le déplacement vertical de la fibre pour maintenir la tache lumineuse au milieu de l'axe Y.The signal Y corresponds to the vertical displacement of the fiber which results from the flatness defects of the disc. This signal passes through a low-pass filter 29 with a cut-off frequency of 10 Hz and is directed to the motor 23 via a regulation circuit 30 which controls the vertical movement of the fiber to maintain the light spot in the middle of the Y axis.
Il est particulièrement important de savoir que la contrainte que l'extrémité de la fibre exerce sur le sillon est de l'ordre de 50 à 60 mg, c'est-à-dire très inférieure à celle exercée par une quelconque aiguille ou stylet classique. Dans la pratique, la diminution de la contrainte est d'au moins un facteur 40 à 50. De ce fait, il devient possible de lire des disques fissurés et craquelés.It is particularly important to know that the stress that the end of the fiber exerts on the groove is of the order of 50 to 60 mg, that is to say much lower than that exerted by any conventional needle or stylus . In practice, the reduction in stress is at least a factor of 40 to 50. As a result, it becomes possible to read cracked and cracked discs.
Le signal correspondant au son enregistré peut ensuite être retraité par des techniques courantes de numérisation qui permettent de reconstituer le son original en éliminant tous les défauts dus à ces fissures ou à ces craquelures. La figure 9 permet de comparer les positions de lecture d' une aiguille classique et de la fibre optique . En raison de la géométrie différente de ces deux éléments et du choix approprié du diamètre de la fibre, les zones de contact desdits éléments avec les faces 11 et 12 de la gorge 10 ne sont pas situées aux mêmes endroits . Les zones de contact lia et 12a de l'aiguille sont souvent endommagées en raison des multiples lectures du disque . Les zones de contact 11b et 12b de la fibre optique 14 sont localisées plus haut que les précédentes , c'est-à-dire à des endroits où il n'y a pratiquement jamais eu de contact avec une aiguille. De ce fait on élimine une part non négligeable des bruits parasites . The signal corresponding to the recorded sound can then be reprocessed by current digitization techniques which make it possible to reconstruct the original sound by eliminating all the defects due to these cracks or to these cracks. FIG. 9 makes it possible to compare the reading positions of a conventional needle and of the optical fiber. Due to the different geometry of these two elements and the appropriate choice of the diameter of the fiber, the contact zones of said elements with the faces 11 and 12 of the groove 10 are not located in the same places. The contact areas 11a and 12a of the needle are often damaged due to the multiple readings of the disc. The contact areas 11b and 12b of the optical fiber 14 are located higher than the previous ones, that is to say in places where there has practically never been contact with a needle. This eliminates a significant part of the parasitic noise.

Claims

REVENDICATIONS
1. Procédé de lecture optique d'un enregistrement sonore sur un sup¬ port gravé comportant au moins un sillon enroulé en spirale sur un disque, ou en hélice sur un cylindre, entraîné en rotation autour d'un axe, caractérisé en ce que l'on dispose une fibre optique sensiblement tangentiellement dans ledit sillon de telle manière que les modulations gravés dans ledit sillon engendrent des déplacements de l'extrémité de cette fibre, en ce que l'on injecte de la lumière dans ladite fibre, en ce que la lumière sortant près de l'extrémité de ladite fibre forme une tache lumineuse, en ce que l'on recueille une image de ladite tache sur un capteur optique de position, et en ce que l'on analyse au moins une composante des mouvements de ladite tache pour lire ledit enregistrement .1. Process for the optical reading of a sound recording on an engraved support comprising at least one groove wound in a spiral on a disc, or in a helix on a cylinder, driven in rotation about an axis, characterized in that l 'an optical fiber is disposed substantially tangentially in said groove so that the modulations etched in said groove cause displacements of the end of this fiber, in that light is injected into said fiber, in that the light coming out near the end of said fiber forms a light spot, in that an image of said spot is collected on an optical position sensor, and in that at least one component of the movements of said said is analyzed task to read said recording.
2. Procédé selon la revendication 1, caractérisé en ce que la lumière sortant de ladite fibre et formant ladite tache est réfléchie à l'extrémité de ladite fibre et sort latéralement de la fibre.2. Method according to claim 1, characterized in that the light leaving said fiber and forming said spot is reflected at the end of said fiber and leaves laterally of the fiber.
3. Procédé selon la revendication 2, caractérisé en ce que l'on analyse les mouvements de ladite tache lumineuse selon deux axes orthogonaux, et en ce que l'on exploite les résultats de cette analyse, d'une part pour lire ledit enregistrement et d'autre part pour commander les déplacements de la fibre pour qu'elle suive le sillon dudit support gravé.3. Method according to claim 2, characterized in that one analyzes the movements of said light spot along two orthogonal axes, and in that one uses the results of this analysis, on the one hand to read said recording and on the other hand to control the movements of the fiber so that it follows the groove of said engraved support.
4. Procédé selon la revendication 3, caractérisé en ce que, pour analyser les mouvements de la tache lumineuse, on décompose le signal correspondant à la composante selon l'un des axes en deux signaux dont l'un fournit l'enregistrement sonore gravé sur le support et dont l'autre permet d'asservir le déplacement latéral de la fibre pour suivre le sillon, et en ce que l'on utilise le signal correspondant à la composante selon l'autre axe pour commander la hauteur du point d'ancrage de la fibre par rapport audit support gravé. 4. Method according to claim 3, characterized in that, to analyze the movements of the light spot, the signal corresponding to the component is broken down along one of the axes into two signals, one of which provides the sound recording engraved on the support and the other of which controls the lateral movement of the fiber to follow the groove, and in that the signal corresponding to the component along the other axis is used to control the height of the anchor point of the fiber with respect to said engraved support.
5. Procédé selon la revendication 3, caractérisé en ce que les axes orthogonaux sont respectivement parallèle et perpendiculaire à la surface du support gravé.5. Method according to claim 3, characterized in that the orthogonal axes are respectively parallel and perpendicular to the surface of the engraved support.
6. Procédé selon la revendication 3, caractérisé en ce que, les axes orthogonaux sont disposés à 45° par rapport au plan médian passant par le fond du sillon.6. Method according to claim 3, characterized in that, the orthogonal axes are arranged at 45 ° relative to the median plane passing through the bottom of the groove.
7. Procédé selon les revendications 4 et 5, caractérisé en ce que, pour un support du type disque, le signal fournissant l'enregistrement sonore et le signal permettant d'asservir le déplacement latéral de la fibre correspondent à l'axe X parallèle au plan du disque, et en ce que le signal permettant de commander la hauteur du point d'ancrage de la fibre correspond à l'axe Y perpendiculaire au plan du disque.7. Method according to claims 4 and 5, characterized in that, for a disc-type support, the signal providing the sound recording and the signal making it possible to control the lateral movement of the fiber correspond to the X axis parallel to the plane of the disc, and in that the signal making it possible to control the height of the fiber anchoring point corresponds to the axis Y perpendicular to the plane of the disc.
8. Dispositif de lecture optique d'un enregistrement sonore sur un support gravé comportant au moins un sillon enroulé en spirale sur un disque, ou en hélice sur un cylindre, entraîné en rotation autour d'un axe, caractérisé en ce qu'il comporte une fibre optique (14) disposée sensiblement tangentiellement dans ledit sillon, des moyens pour injecter de la lumière dans la fibre (14) , un système optique (19) pour recueillir la lumière sortant de la fibre, un capteur optique de position (20) sur lequel le système optique (19) produit une image de la tache lumineuse (21) formée par la lumière sortant de la fibre, et des moyens pour analyser les signaux délivrés par le capteur de position (20) et en déduire les mouvements de la tache lumineuse selon au moins une direction pour lire ledit enregistrement.8. Device for optically reading a sound recording on an engraved support comprising at least one groove wound in a spiral on a disc, or in a helix on a cylinder, driven in rotation about an axis, characterized in that it comprises an optical fiber (14) disposed substantially tangentially in said groove, means for injecting light into the fiber (14), an optical system (19) for collecting the light leaving the fiber, an optical position sensor (20) on which the optical system (19) produces an image of the light spot (21) formed by the light leaving the fiber, and means for analyzing the signals delivered by the position sensor (20) and deducing therefrom the movements of the light spot in at least one direction for reading said recording.
9. Dispositif selon la revendication 8, caractérisé en ce que la fibre optique (14) a une extrémité libre disposée dans le sillon, cette extrémité étant agencée pour réfléchir la lumière guidée par son coeur (15) et pour la renvoyer latéralement par rapport à son axe.9. Device according to claim 8, characterized in that the optical fiber (14) has a free end disposed in the groove, this end being arranged to reflect the light guided by its heart (15) and to return it laterally with respect to its axis.
10. Dispositif selon la revendication 8, caractérisé en ce qu'il comporte deux moteurs d'asservissement (22, 23) , l'un (22) pour déplacer latéralement la fibre pour qu'elle suive le sillon enroulé en spirale sur un disque, ou en hélice sur un cylindre, et l'autre (23) pour qu'elle se maintienne à un niveau sensiblement constant par rapport à la surface du disque.10. Device according to claim 8, characterized in that it comprises two servo motors (22, 23), one (22) for moving the fiber laterally so that it follows the groove wound in a spiral on one disc, or helically on a cylinder, and the other (23) so that it is maintained at a substantially constant level with respect to the surface of the disc.
11. Dispositif selon la revendication 8, caractérisé en ce que le capteur optique de position (20) comporte quatre électrodes (20xi , 20x2 ; 20yι, 20y2) correspondant par paire aux deux axes orthogonaux. 11. Device according to claim 8, characterized in that the optical position sensor (20) comprises four electrodes (20xi, 20x2; 20 y ι, 20y2) corresponding in pairs to the two orthogonal axes.
EP93903773A 1992-02-24 1993-02-22 Method and device for optically reading a sound recording on a grooved recording medium Withdrawn EP0591479A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
CH557/92 1992-02-24
CH55792 1992-02-24
PCT/CH1993/000045 WO1993017418A1 (en) 1992-02-24 1993-02-22 Method and device for optically reading a sound recording on a grooved recording medium

Publications (1)

Publication Number Publication Date
EP0591479A1 true EP0591479A1 (en) 1994-04-13

Family

ID=4189769

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93903773A Withdrawn EP0591479A1 (en) 1992-02-24 1993-02-22 Method and device for optically reading a sound recording on a grooved recording medium

Country Status (2)

Country Link
EP (1) EP0591479A1 (en)
WO (1) WO1993017418A1 (en)

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4870631A (en) * 1986-05-30 1989-09-26 Finial Technology, Inc. Optical turntable system with reflected spot position detection

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9317418A1 *

Also Published As

Publication number Publication date
WO1993017418A1 (en) 1993-09-02

Similar Documents

Publication Publication Date Title
EP0012650B1 (en) Device for acceding to a track on an optically recordable or readable carrier and optical system comprising such a device
JP4160135B2 (en) Disk device using ferroelectric thin film
EP0033052A1 (en) Optical recording-reproducing device of record carriers and optical memory system comprising such a device
EP0089263A1 (en) Pre-engraved movable record carrier and tracking device therefor
EP0097092A1 (en) Method of and optical device for focusing a light beam onto a reference plane of an information carrier
EP0519768B1 (en) High density information storage carrier and method of reading such a carrier
WO1989002573A1 (en) Device for continuously determining a condition indication of the surface of a crepe paper web in motion
EP0023868A1 (en) Optical device for access to an information carrier track and optical memory system comprising such a device
EP0527670A1 (en) Magneto-optical read head
FR2676302A1 (en) METHOD FOR READING INFORMATION CONTAINED IN AN OPTICAL DISK
EP0022682A1 (en) Optical reading head with semi-conductor laser source and device for reading a record carrier by using reflexion, comprising such an optical head
CA2042579C (en) High resolution magneto-optic reading head
EP0610147B1 (en) Sensor for measuring the characteristics of a linear product, which is very long in respect to its other dimensions, on a production machine or similar
EP0591479A1 (en) Method and device for optically reading a sound recording on a grooved recording medium
EP0789907B1 (en) Optical focus control system
FR2585527A1 (en) DEVICE FOR THE RESTITUTION AND / OR ANALYSIS OF COLOR IMAGES USING A CATHODIC TUBE OPTICAL FIBER SCREEN LINE
EP1626402B1 (en) Device for optically reading analogical phonographic disks
JPS62175605A (en) Decoder
FR2523727A1 (en) IMPROVEMENTS IN DEVICES FOR MEASURING ELECTRICAL LOADS CARRIED BY A DIELECTRIC
FR2513421A1 (en) DEVICE FOR SEARCHING THE TRACK OF AN INFORMATION SIGNAL FOR A DEVICE FOR REPRODUCING ROTATING RECORDING MEDIA
FR2769417A1 (en) LASER AMPLIFIER DISC AND DISC GLUING CONTROL METHOD
WO1999038160A1 (en) Data medium optical recording/reading device
EP0576322A1 (en) Procedure for non-destructive testing of a soldered joint
FR2621411A1 (en) ASSISTED DEVICE FOR OPTICALLY READING AND MAGNETIC WRITING OF AN INFORMATION CARRIER
BE674554A (en)

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19940203

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE FR GB LI LU NL

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19950901