Classifications

• • 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
  • G11B11/10—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 magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
  • G11B11/105—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 magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
  • G11B11/10532—Heads
  • G11B11/10541—Heads for reproducing
  • G11B11/10543—Heads for reproducing using optical beam of radiation
  • G11B11/10547—Heads for reproducing using optical beam of radiation interacting with the magnetisation of an intermediate transfer element, e.g. magnetic film, included in the head
• • 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
  • G11B11/10—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 magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
  • G11B11/105—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 magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
  • G11B11/1055—Disposition or mounting of transducers relative to record carriers
  • G11B11/10576—Disposition or mounting of transducers relative to record carriers with provision for moving the transducers for maintaining alignment or spacing relative to the carrier
• • 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
  • G11B7/002—Recording, reproducing or erasing systems characterised by the shape or form of the carrier
  • G11B7/003—Recording, reproducing or erasing systems characterised by the shape or form of the carrier with webs, filaments or wires, e.g. belts, spooled tapes or films of quasi-infinite extent
• • 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
  • G11B7/14—Heads, e.g. forming of the optical beam spot or modulation of the optical beam specially adapted to record on, or to reproduce from, more than one track simultaneously

Definitions

• the present invention relates to devices which make it possible to read magneto-optically simultaneously all of the tracks recorded in parallel on a magnetic tape. It applies more particularly to the system for recording high density digital data on magnetic tape, known in the art as SDCR.
• the SDCR high density magnetic tape recording and playback system was designed in the central research laboratory of THOMSON-CSF to obtain a magnetic tape recording system based on a set of parallel tracks which have a very high recording density, without resorting to the conventional system of rotating heads. It uses for this a very original recording device by magnetic head having a set of integrated poles arranged in a matrix, and for reading a magneto-optical head with Kerr effect having an essentially monolithic structure.
• the writing and reading heads thus designed therefore allow extremely dense parallel recording and reading while being very simple to manufacture compared to the systems used elsewhere. More particularly, for reading the Kerr effect head comprises, in a manner now known in the art, a prism comprising a stack of suitable materials.
• a polarized laser beam having a flat and elongated incident beam to be adapted to the size of the bits inscribed on the magnetic tracks, and a width sufficient to cover the entire magnetic strip according to the width thereof.
• the polarization of the optical beam changes as a function of the direction of the magnetization induced by the magnetic tape respectively for each track recorded on the tape. This change in polarization is transformed into a change in intensity, by a polarizer for example.
• the beam is then received on a strip of detectors, of the CCD type for example. Each of the cells of this CCD then delivers a signal representative of the information recorded on each of the tracks of the strip.
• the invention proposes a magneto-optical reading device for multitrack magnetic tapes, comprising a flat and elongated incident beam directed towards the active part of a magneto-optical reading head and reflected by this head towards a strip of detectors, mainly characterized in that it includes correction means to be able to move the impact zone of the incident beam on the head so as to maintain the beam on the active part as it moves under the effect of the wear of the head .
• these correction means comprise a first blade with parallel flat faces, inserted in the path of the incident beam and rotating around a first axis parallel to the plane of the incident beam and perpendicular to the axis thereof.
• the correction means further comprise a second blade with parallel flat faces inserted in the path of the return beam reflected by the read head and rotating around a second axis parallel to the plane of the reflected beam and perpendicular to its axis, to correct the displacement of this reflected beam as a function of the displacement of the incident beam caused by the rotation of the first plate with parallel plane faces.
• said second blade with parallel planar faces also comprises a third axis of rotation perpendicular to the plane of the reflected beam in order to be able to move this reflected beam in its own plane so as to keep the brushes of this beam modulated by the tracks of the magnetic strip on the corresponding detectors of the detection strip, thus correcting the swaying movements of the magnetic strip.
• the device comprises a controlled system making it possible to operate the correction means to permanently obtain an optimal correction of the wear of the read head.
• a magnetic strip 101 comprising a set of parallel tracks 102 scrolls under a read head 103.
• the structure of this head is known elsewhere and it has only been shown schematically and seen by transparency above the head contact area with the magnetic strip.
• the active part 104 magnetized by the strip, has the shape of a very narrow rectilinear strip (width of the order of 2 to 3 micrometers) located in the figure at the end of the left edge of the read head 103.
• This active part is illuminated by a laser, not shown in the figure, and whose polarized light beam has been shaped by a known optical system, itself not shown in the figure, so as to have dimensions adapted to the active part 104.
• This beam 105 is oriented so as to illuminate this active part 104. It is then reflected by being modulated in polarization by the orientation of the bits contained in the magnetic tracks 102, to form a return beam 106, containing a set of modulated brushes , which is directed towards a strip 107 of detectors, of the CCD type for example. Each of the detectors 108 of this strip thus receives one of the brushes of the beam 106, which has been modulated by one of the tracks 102. The intensity received on each of these cells depends on the modification of the polarization brought to the beam by the magnetic state of the track being read. Polarizing plates, not shown but known in the art, make it possible to transform this change in polarization into a change in intensity that can be detected by the cells 108.
• the advantage of the system is that it does not individualize the reading of the tracks at the level of the head 103 proper, as is done in magnetoresistive heads, which would require a longitudinal segmentation adapted to the tracks and a tracking system. track to compensate for the lateral sway of the magnetic strip, which are very difficult to implement.
• the individualization of the tracks is therefore carried over to the level of the detector array 107, which is a well known and commercially available device.
• the swaying of the strip is compensated for using a blade with parallel flat faces 109 which can oscillate around an axis 1 10 perpendicular to the beam plane 106.
• the movement C x x thus obtained makes it possible to move this beam 106 in its own plane while remaining parallel to itself, according to the well-known properties of the blades with parallel flat faces.
• a servomechanism system itself known, makes it possible to maintain the image of the tracks 102 on the cells 108 which are assigned to them, so that each of these cells always delivers the signal recorded on the corresponding track with the maximum level possible, and this despite the movements of the magnetic strip in its own plane.
• the active part 104 will have moved a distance Z after a few hundred hours of operation, to be located in the position 1 1 1, itself located outside the beam incident 105.
• the invention proposes using a second blade with parallel flat faces 112 which can oscillate around an axis of rotation 1 13 parallel to the plane of the incident beam 105 and perpendicular to the axis of it.
• the movement Cu z , of this blade with parallel plane faces displaces the beam 105 in a direction perpendicular to the plane of the incident beam while keeping it parallel to itself. This beam therefore moves to strike the read head in the new position 1 1 1 occupied by the active part thereof.
• the return beam 1 16 reflected by this area at its new location is offset from the initial reflected beam 106 and therefore no longer strikes the array of detectors 107 in the right place.
• the invention proposes to also rotate the blade with parallel flat faces 109 along an axis 1 14 parallel to the plane of the return beam 106 and perpendicular to the axis thereof,
• the movement C ⁇ z foster of the blade 109 around this axis 114 will be substantially symmetrical with the movement Cu z , of the blade 112 around the axis 1 13, so as to compensate for the displacement of the return beam originating from the displacement of the incident beam, so that this beam always come to strike the 107 detector array in the right place.
• the displacements in question which are very slow, can be obtained by micromotors, piezoelectric for example, not shown in the figure and controlled by a controlled system, itself not shown, which will operate from the detection of an error signal.
• One can use for example a dedicated track, which can be a synchronization track. It is also possible, for example, to detect the average power observed on the output signal from the cells 108 of the detector array. This will permanently obtain an optimal correction of the wear of the read head.
• the blades with parallel flat faces 109 and 1 12 only in their rest state when the magnetic strip is centered and that there is no wear.
• the beams 105 and 106 are those actually transmitted by the blades with parallel flat faces, while the beams 1 15 and 1 16 are those which would be transmitted when these blades would have turned around the axes 1 13 and 1 14 of the angles necessary to obtain the desired deviation.
• the path of these beams in the blades, as shown in the figure, is therefore not the actual path but makes it possible to understand the invention perfectly.
• the invention extends to all means making it possible to obtain an automatic correction of the wear of the head, such as for example a micromotor making it possible to move the head itself, where the sensitive part thereof, of so as to maintain the detection beam on the active part of the head.

Applications Claiming Priority (5)

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• 2000
  • 2000-04-07 FR FR0004502A patent/FR2797514B3/fr not_active Expired - Lifetime
  • 2000-08-04 US US10/048,476 patent/US6958956B1/en not_active Expired - Lifetime
  • 2000-08-04 EP EP00956621A patent/EP1203374A1/de not_active Withdrawn
  • 2000-08-04 WO PCT/FR2000/002248 patent/WO2001011619A1/fr not_active Application Discontinuation

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